0001193125-26-108346 | 10-K | XBRL Viewer

Fair Value Measurements

12 Months Ended

Dec. 31, 2025

. Fair Value Measurements

In accordance with the authoritative guidance on fair value measurements and disclosures under U.S. GAAP, the Company presents all financial assets and liabilities and any other assets and liabilities that are recognized or disclosed at fair value on a nonrecurring basis. The guidance defines fair value, establishes a framework for measuring fair value in generally accepted accounting principles and expands disclosures about fair-value measurements. The guidance also requires fair value measurements be classified and disclosed in one of the following three categories:

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Observable inputs other than quoted prices in active markets for identical assets or liabilities.

Level 3: Unobservable inputs.

The Company values certain assets and liabilities, focusing on the inputs used to measure fair value, particularly in instances where the measurement uses significant unobservable (Level 3) inputs. The Company’s financial instruments are valued using quoted prices in active markets (Level 1) or based upon other observable inputs (Level 2). The Company’s assessment of the significance of a particular input to the fair value measurement in its entirety requires management to make judgments and considers factors specific to the asset or liability. In addition, the categories presented do not suggest how prices may be affected by the size of the purchases or sales, particularly with the largest highly liquid financial issuers who are in markets continuously with non-equity instruments, or how any such financial assets may be impacted by other factors such as U.S. government guarantees. Assets and liabilities measured at fair value are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The availability of observable data is monitored to assess appropriate classification of financial instruments within the fair value hierarchy. Depending upon the availability of such inputs, specific securities may transfer between levels. In such instances, the transfer is reported at the end of the reporting period.

The fair values of the Company’s financial assets that are measured on a recurring basis are as follows (in thousands):


	December 31, 2025
	Level 1		Level 2		Level 3		Total
Money market funds	$	24,302	$	—	$	—	$	24,302
Corporate bonds		—		27,817		—		27,817
Commercial paper		—		17,797		—		17,797
U.S. government bonds		31,922		4,991		—		36,913
Total	$	56,224	$	50,605	$	—	$	106,829

	December 31, 2024
	Level 1		Level 2		Level 3		Total
Money market funds	$	28,241	$	—	$	—	$	28,241
Commercial paper		—		14,269		—		14,269
U.S. government bonds		2,987		2,981		—		5,968
Total	$	31,228	$	17,250	$	—	$	48,478

The Company’s Level 2 investments are valued using third-party pricing sources. The pricing services utilize industry standard valuation models, including both income and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. These inputs include reported trades of and broker/dealer quotes on the same or similar investments, issuer credit spreads, benchmark investments, prepayment/default projections based on historical data and other observable inputs. During the years ended December 31, 2025 and 2024, the transfers of assets between levels was a total of $22.8 million and $26.3 million transfer from Level 1 to Level 2, respectively, as such US treasury notes and bills were changed to off-the-run when they were issued before the most recent issue and were still outstanding at measurement day.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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+ Details

Balance Sheet Components - Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Available-for-Sale Investments (Detail) $ in Thousands	Dec. 31, 2025 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 61,228
Gross Unrealized Holding Gains	38
Gross Unrealized Holding Losses	0
Estimated Fair Value	61,266
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,800
Gross Unrealized Holding Gains	17
Gross Unrealized Holding Losses	0
Estimated Fair Value	27,817
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,525
Gross Unrealized Holding Gains	0
Gross Unrealized Holding Losses	0
Estimated Fair Value	6,525
U.S. government bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	26,903
Gross Unrealized Holding Gains	21
Gross Unrealized Holding Losses	0
Estimated Fair Value	$ 26,924

- Definition

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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+ Details

Balance Sheet Components - Schedule of Accrued and Other Current Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Accrued Liabilities, Current [Abstract]
Preclinical and clinical trial accruals	$ 3,066	$ 6,327
API and bulk drug product price true-up	6,977	13,071
Litigation settlement	0	28,500
Payroll and related accruals	3,983	4,640
Accrued restructuring charge	537	4,572
Professional services	2,465	2,049
Current portion of liability related to sale of future revenues	1,334	460
Other	1,821	2,416
Total accrued and other current liabilities	$ 20,183	$ 62,035

Income Taxes - Reconciliation of the Beginning and Ending Amounts of Unrecognized Income Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Income Tax Contingency [Line Items]
Ending Balance	$ 74,500
Federal and State [Member]
Income Tax Contingency [Line Items]
Beginning balance	74,321	$ 70,710
Decrease due to prior positions	(229)	(156)
Increase due to current year position	372	3,920
Foreign exchange rate differential	0	(153)
Ending Balance	$ 74,464	$ 74,321

Discontinued Operations and Divestiture - Schedule of Financial Results of Discontinued Operations (Detail) - USD ($) $ in Thousands		12 Months Ended
	Aug. 29, 2025	Dec. 31, 2025	Dec. 31, 2024
Interest and other, net
Gain on divestiture		$ 52,553	$ (0)
Income from discontinued operations, net of tax		241,656	105,519
FibroGen International [Member]
Revenue:
Product revenue, net		226,651	173,664
Operating costs and expenses:
Cost of goods sold		13,454	21,036
Research and development		1,739	7,375
Selling, general and administrative		14,849	32,304
Total operating costs and expenses		30,042	60,715
Income from operations		196,609	112,949
Interest and other, net
Interest expense		(7,816)	(11,683)
Gain on divestiture	$ 52,600	52,553	0
Interest income and other income (expenses), net		(2,173)	423
Total interest and other, net		42,564	(11,260)
Income before income taxes		239,173	101,689
Provision for income taxes		0	139
Investment income in unconsolidated variable interest entity		2,483	3,969
Income from discontinued operations, net of tax		$ 241,656	$ 105,519

Commitments and Contingencies

12 Months Ended

Dec. 31, 2025

Commitments and Contingencies Disclosure [Abstract]

Commitments and Contingencies

11. Commitments and Contingencies

Contract Obligations

As of December 31, 2025, the Company had outstanding total non-cancelable purchase obligations of $3.3 million for general purchases and other programs and $2.3 million for manufacture and supply of roxadustat, expected to pay within the next twelve months. The Company expects to fulfill its commitments under these agreements in the normal course of business, and as such, no liability has been recorded.

See Note 9, Liability Related to Sale of Future Revenues and Note 10, Product Development Obligations for details of the respective obligations.

Legal Proceedings and Other Matters

From time to time, the Company is a party to various legal actions, both inside and outside the U.S., arising in the ordinary course of its business or otherwise. The Company accrues amounts, to the extent they can be reasonably estimated, that the Company believes will result in a probable loss (including, among other things, probable settlement value) to adequately address any liabilities related to legal proceedings and other loss contingencies. A loss or a range of loss is disclosed when it is reasonably possible that a material loss will incur and can be estimated, or when it is reasonably possible that the amount of a loss, when material, will exceed the recorded provision. The Company did not have any material accruals for any active legal action, in its consolidated balance sheet as of December 31, 2025.

Between April 2021 and May 2021, five putative securities class action complaints were filed against the Company and certain of its former executive officers in the U.S. District Court for the Northern District of California. On October 17, 2023, the parties reached an agreement in principle to settle the class action at $28.5 million. The Court approved the settlement Plan of Allocation on May 28, 2024 and Plaintiffs’ motion for attorney’s fees on August 1, 2024. The court entered a class distribution order on January 1, 2025 and the amount was fully distributed during the first quarter of 2025. The settlement was fully covered by insurance.

In the fourth quarter of 2021, the Company received a subpoena from the U.S. Securities and Exchange Commission (“SEC”) requesting documents related to roxadustat’s pooled cardiovascular safety data. The SEC followed up with a subpoena for additional documents in the second quarter of 2024. In May 2025, the Company entered into a settlement with the SEC. As part of the settlement, and without admitting or denying the findings in the settlement offer or administrative order to be issued by the SEC, the Company agreed to pay a $1.25 million civil penalty. In September 2025, the agreement was approved by the Commission and the Company has been making payments to the agreed upon payment schedule.

Between 2022 and 2024, the Company’s Board of Directors received seven litigation demands from purported shareholders of the Company, asking the Board of Directors to investigate and take action against certain current and former officers and directors of the Company for alleged wrongdoing based on the same allegations in the derivative and securities class action lawsuits. The litigation demands have been withdrawn.

Indemnification Agreements

The Company enters into standard indemnification arrangements in the ordinary course of business, including for example, service, manufacturing and collaboration agreements. Pursuant to these arrangements, the Company indemnifies, holds harmless, and agrees to reimburse the indemnified parties for losses suffered or incurred by the indemnified party, including in connection with intellectual property infringement claims by any third party with respect to its technology. The term of these indemnification agreements is generally perpetual after the execution of the agreement. The Company has entered into indemnification agreements with its directors and officers that may require the Company to indemnify its directors and officers against liabilities that may arise by reason of their status or service as directors or officers to the extent permissible under applicable law.

There is currently one SEC complaint against the Company's former Chief Medical Officer in U.S. District Court. While the Company is not a party to this proceeding, pursuant to its indemnification agreement with the former officer, the Company is obligated to advance certain legal expenses and may be required to indemnify certain costs and judgments; however, certain judgments, settlements, or fines sought by the SEC would not be covered by the Company under the indemnification agreement.

As of December 31, 2025, the Company’s accrued liabilities related to these obligations were not material. The Company is unable to reasonably estimate the total amount of future indemnification costs beyond amounts currently accrued due to the early stage of the litigation and significant uncertainties regarding the duration, scope, and outcome of the proceedings.

Equity and Stock-based Compensation - Stock Plans - Summary of Stock Option Transactions (Detail) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($) $ / shares shares
Share-Based Payment Arrangement [Abstract]
Outstanding, Beginning Balance, Shares \| shares	389
Granted, Shares \| shares	263
Forfeited, Shares \| shares	(82)
Expired, Shares \| shares	(197)
Outstanding, Ending Balance, Shares \| shares	373
Vested and expected to vest, Shares \| shares	329
Exercisable, Shares \| shares	146
Outstanding, Beginning Balance, Weighted Average Exercise Price per Share \| $ / shares	$ 400.52
Granted, Weighted Average Exercise Price per Share \| $ / shares	15.14
Forfeited, Weighted Average Exercise Price per Share \| $ / shares	59.65
Expired, Weighted Average Exercise Price per Share \| $ / shares	577.45
Outstanding, Ending Balance, Weighted Average Exercise Price per Share \| $ / shares	110.26
Vested and expected to vest, Weighted Average Exercise per Share \| $ / shares	122.04
Exercisable, Weighted Average Exercise Price per Share \| $ / shares	$ 240.24
Outstanding, Weighted Average Remaining Contractual Life	8 years 2 months 23 days
Vested and expected to vest, Weighted Average Remaining Contractual Life	8 years 1 month 24 days
Exercisable, Weighted Average Remaining Contractual Life	7 years 3 months 29 days
Outstanding, Aggregate Intrinsic Value \| $	$ 30
Vested and expected to vest, Aggregate Intrinsic Value \| $	28
Exercisable, Aggregate Intrinsic Value \| $	$ 12

Liability Related to Sale of Future Revenues

12 Months Ended

Dec. 31, 2025

9. Liability Related to Sale of Future Revenues

In November 2022, the Company entered into a revenue interest financing agreement (the “RIFA”) with NQ Project Phoebus, L.P. (“NovaQuest”), pursuant to which the Company granted NovaQuest 22.5% of its drug product revenue and 10.0% (20.0% for fiscal year 2028 and thereafter) of its revenue from milestone payments that it is entitled to under the Astellas Agreements, for a consideration of $50.0 million (“Investment Amount”) before advisory fees.

In November 2022, the Company received the Investment Amount, net of initial issuance costs, and accounted for it as long-term debt based on the terms of the RIFA because the risks and rewards to NovaQuest are limited by the terms of the transaction. The related debt discount and transaction costs are amortized as interest expense based on the projected balance of the liability as of the beginning of each period. As payments are made to NovaQuest, the balance of the liability related to sale of future revenues is being effectively repaid over the life of the RIFA. The payments to NovaQuest are accounted for as a reduction of debt.

The Company may prepay its obligations to NovaQuest in full at any time during the term of RIFA. The prepayment amount varies from $80.0 million to $125.0 million less any revenue interest payments made up to such prepayment date. Under the RIFA the Company shall pay to NovaQuest up to a specified maximum amount (“Payment Cap”) of (a) $100.0 million, if the payment is made on or before December 31, 2028; (b) $112.5 million, if the payment is made on or after January 1, 2029, but on or before December 31, 2029; or (c) $125.0 million, if the payment is made after January 1, 2030.

After January 1, 2028, if the product (as defined) is not commercialized for a consecutive twelve-month period, then, the payments owed under the RIFA by the Company to NovaQuest for each fiscal year shall be the greater of: (i) the amount which would otherwise be due pursuant to revenue interest payments terms; or (ii) $10.0 million.

Before December 31, 2028, if the sum of all payments under the RIFA paid to NovaQuest, does not equal or exceed $62.5 million, then the Company shall pay NovaQuest the difference of these two amounts by no later than March 1, 2029. If, by no later than December 31, 2030, the sum of all payments under the RIFA paid to NovaQuest does not equal or exceed $125.0 million, then the Company shall pay NovaQuest the difference of these two amounts by no later than March 1, 2031.

NovaQuest will retain this entitlement until it has reached the Payment Cap, at which point 100% of such revenue interest on future global net sales of Astellas will revert to the Company.

Over the course of the RIFA, the effective interest rate is affected by the amount and timing of drug product revenue and revenue from milestone payments recognized, the changes in the timing of forecasted drug product revenue and revenue from milestone payments, and the timing of the Company’s payments to NovaQuest. On a quarterly basis, the Company reassesses the expected total revenue and the timing of such revenue, recalculates the amortization of debt discount and transactions costs and effective interest rate, and adjusts the accounting prospectively as needed. The Company’s estimated effective annual interest rate was 15.21% as of December 31, 2025.

The table below shows the activity of the liability related to sale of future revenues for the year ended December 31, 2025 and 2024:


	For the Year Ended December 31,
	2025			2024
Liability related to sale of future revenues - beginning balance	$	59,324		$	57,067
Interest paid		(450	)		(5,653	)
Interest expense recognized		8,440			7,910
Liability related to sale of future revenues - ending balance		67,314			59,324
Less: Current portion classified to accrued and other current liabilities		(1,334	)		(460	)
Liability related to sale of future revenues, non-current	$	65,980		$	58,864

During the years ended December 31, 2025 and 2024, the Company recognized, under Astellas Agreements, development revenue of $0.6 million and $1.4 million, respectively, and drug product revenue of $5.8 million and $2.0 million, respectively. See Note 4, Collaboration Agreements, License Agreement and Revenue, for details.

During the years ended December 31, 2025 and 2024, the Company recognized the related interest expense of $8.4 million and $7.9 million, respectively. During the years ended December 31, 2025 and 2024, the Company paid $0.5 million and $5.7 million accrued interest, respectively.

Based on the current estimates of drug product revenue and revenue from milestone payments under the Astellas Agreements, and taking into the consideration of the terms discussed above, the Company anticipates to reach a Payment Cap up to $125.0 million by 2031.

Segment and Geographic Information - Schedule of Revenue by Geographic Area (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Segment Reporting Information [Line Items]
Revenue recognized	$ 6,440	$ 29,621
United States [Member]
Segment Reporting Information [Line Items]
Revenue recognized	0	26,114
Europe [Member]
Segment Reporting Information [Line Items]
Revenue recognized	5,643	6,270
Japan [Member]
Segment Reporting Information [Line Items]
Revenue recognized	797	(2,854)
China [Member]
Segment Reporting Information [Line Items]
Revenue recognized	$ 0	$ 91

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

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+ Details

Collaboration Agreements, License Agreement and Revenues - Accounting for the AstraZeneca Agreements - Additional Information 3 (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Sep. 30, 2025
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue	$ 6,440	$ 29,621
AstraZeneca Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue	218,600	$ 159,000
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member] \| License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total Consideration	344,500
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member] \| Co-development, information sharing & committee services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total Consideration	$ 625,500
AstraZeneca Agreements [Member] \| U.S./RoW and China [Member] \| China Performance Obligation [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total Consideration			$ 573,400

- Definition

Amount, excluding tax collected from customer, of revenue from satisfaction of performance obligation by transferring promised good or service to customer. Tax collected from customer is tax assessed by governmental authority that is both imposed on and concurrent with specific revenue-producing transaction, including, but not limited to, sales, use, value added and excise.

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+ Details

The Company - Additional Information (Details) - USD ($) $ in Millions	Aug. 29, 2025	Feb. 20, 2025
Share Purchase Agreement [Member]
Product Information [Line Items]
Discontinued operation consideration	$ 220.4
Share Purchase Agreement [Member] \| FibroGen International [Member]
Product Information [Line Items]
Discontinued operation consideration	220.4
Discontinued operation consideration in cash	85.0
Share Purchase Agreement [Member] \| Net Cash Held in China [Member]
Product Information [Line Items]
Discontinued operation consideration in cash	135.4
CHINA \| Share Purchase Agreement [Member] \| FibroGen International [Member]
Product Information [Line Items]
Discontinued operation consideration	220.4
Discontinued operation consideration in cash	$ 85.0
Disposal group not discontinued operation gain loss on disposal statement of income extensible list not disclosed flag	true
CHINA \| Share Purchase Agreement [Member] \| Net Cash Held in China [Member]
Product Information [Line Items]
Discontinued operation consideration in cash	$ 135.4
Beijing Falikang Pharmaceutical Co Ltd \| Beijing Kangda Yongfu Pharmaceutical Co., LTD [Member] \| AstraZenecaAB [Member]
Product Information [Line Items]
Percentage of outstanding shares acquired	51.10%	51.10%

Senior Secured Term Loan Facilities - Summary of Senior Secured Term Loan Facilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Aug. 29, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Senior secured term loan facilities, ending balance		$ 75,000
Senior secured term loan facilities, non-current	$ 0		$ 73,092
Senior Secured Term Loan Facilities [Member]
Debt Instrument [Line Items]
Principal of senior secured term loan facilities			75,000
Less: Unamortized issuance costs and transaction costs			(1,908)
Senior secured term loan facilities, ending balance			73,092
Senior secured term loan facilities, current			0
Senior secured term loan facilities, non-current			$ 73,092

- Definition

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Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	Dec. 31, 2025	Dec. 31, 2024
Fair Value Disclosures [Abstract]
Transfers of assets from level 1 to 2	$ 22.8	$ 26.3

Income Taxes - Schedule of Significant Components of Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Components of Deferred Tax Assets and Liabilities [Abstract]
Federal and state net operating loss carryforwards	$ 173,195	$ 206,365
Tax credit carryforwards	128,924	129,320
Foreign net operating loss carryforwards	112	120
Capitalized research and development expenses	64,293	83,329
Stock-based compensation	2,128	6,365
Lease obligations	12	22
Reserves and accruals	4,760	4,418
Deferred revenue	0	7,785
Intangible assets	14,135	15,036
Other	6	0
Subtotal	387,565	452,760
Less: Valuation allowance	(387,555)	(452,740)
Net deferred tax assets	10	20
Fixed assets	(10)	(20)
Non-deductible accrued expenses	0	0
Net deferred tax liabilities	(10)	(20)
Total net deferred tax assets	$ 0	$ 0

Consolidated Statements of Comprehensive income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 183,452	$ (47,579)
Other comprehensive income (loss):
Foreign currency translation adjustments	(1,966)	1,166
Cumulative currency translation adjustment attributable to divestiture	5,479	0
Unrealized gain (loss) on investments, net of tax effect	37	(23)
Other comprehensive income, net of taxes	3,550	1,143
Comprehensive income (loss)	$ 187,002	$ (46,436)

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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- Definition

Amount after tax and reclassification adjustments of other comprehensive income (loss).

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+ Details

Balance Sheet Components - Schedule of Prepaid Expenses and Other Current Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Prepaid Expense and Other Assets, Current [Abstract]
Insurance proceeds receivable for litigation settlement	$ 0	$ 28,500
Holdback consideration receivable related to divestiture	4,000	0
Prepaid assets	1,015	1,903
Other current assets	1,121	1,139
Total prepaid expenses and other current assets	$ 6,136	$ 31,542

Cybersecurity Risk Management, Strategy and Governance	12 Months Ended
Cybersecurity Risk Management, Strategy and Governance	Dec. 31, 2025
Cybersecurity Risk Management, Strategy, and Governance [Line Items]
Cybersecurity Risk Management Processes for Assessing, Identifying, and Managing Threats [Text Block]	ITEM 1C. CYBERSECURITY Cybersecurity Governance and Responsibilities Our Board of Directors recognizes that cybersecurity represents an important component of the Company's overall enterprise risk management (“ERM”). Throughout the year, our Board of Directors and its Committees engage with management to discuss and mitigate a wide range of enterprise risks, including cybersecurity. We seek to mitigate cybersecurity risks through a cross-functional approach, including our Cybersecurity Committee, focused on preserving the confidentiality, security, and availability of the information that the Company collects and stores by identifying, preventing and mitigating cybersecurity threats and effectively responding to and remediating cybersecurity incidents as and if they occur. Our Cybersecurity Committee is comprised of information technology, finance, legal, human resources and data privacy employees. It meets regularly to review and oversee the Company’s data security programs, policies, and strategies, including with respect to cybersecurity risk mitigation, business continuity, and business resiliency. Our Cybersecurity Committee (along with the Chief Financial Officer and General Counsel) also reviews, analyzes, and responds to cybersecurity incidents and breaches. Our Audit Committee of the Board of Directors has the responsibility to review and discuss with management the Company’s guidelines, policies, and governance with respect to financial risk exposures and ERM (including with respect to cybersecurity) and to regularly report to the full Board. Our Audit Committee also oversees our internal audit department and management’s internal controls over financial reporting, including with respect to cybersecurity. Our Audit Committee receives regular presentations and reports on cybersecurity risks, progress on continued updates to the Company’s cybersecurity procedures, as well as is made aware, on a timely basis, of any cybersecurity incidents deemed significant enough to be raised to their attention by management, as well as ongoing updates regarding any such incident until it has been remediated. Our head of Information Technology (“IT”) oversees overall cybersecurity management and implements our cybersecurity programs with the IT group, including appropriate risk mitigation strategies, systems, processes, and controls and provides periodic reports to our Audit Committee at least semi-annually. The head of IT holds a Masters in Computer Information Systems and a Bachelor of Science degree in Microbiology, and has served in leadership roles within the pharmaceutical and biotechnology industries for over 25 years, including leading enterprise-wide cybersecurity strategies, regulatory compliance programs, and IT transformation initiatives at leading biopharmaceutical companies. The head of IT has expertise spanning cybersecurity governance, risk management, cloud security, AI-driven cybersecurity enhancements, infrastructure modernization, and enterprise-wide IT resilience. The head of IT plays a key role in aligning cybersecurity frameworks with industry regulations such as SOC compliance, SOX, GxP, and data privacy standards, ensuring a secure and compliant IT environment to support business objectives. Risk Management and Strategy We periodically assess and test our cybersecurity procedures. We identify and assess material risks from cybersecurity threats by engaging outside advisors and experts to identify, anticipate, and assess future threats and trends, to perform assessments on our cybersecurity risk and measures to mitigate such risk, including information security maturity assessments of our information security control environment. The results of such assessments and reviews are reported as appropriate to the Cybersecurity Committee and Audit Committee, and we adjust our cybersecurity procedures as necessary based on the information provided by these assessments and reviews. Cybersecurity Technical Safeguards We continually invest in information and cybersecurity services and technologies. Technical safeguards are designed to protect the Company's information systems from cybersecurity threats, including firewalls, continuous intrusion detection and response system(s), data leak prevention strategies, enhanced email protection software, antimalware functionality and access controls. These safeguards are evaluated and improved through periodic assessments and review of cybersecurity threat intelligence. We rely on third parties to support its cybersecurity program, including but not limited to email security management, security operations and vulnerability management. Cybersecurity Incident Response and Recovery Planning We have established and maintain incident response and data recovery plans that address our response to a cybersecurity incident. Our Cybersecurity Committee and members of the Cyber Security Incident Response Team (which contains additional information technology specialists) regularly test and evaluate the effectiveness of these incident response and data recovery plans. In addition to the incident detection safeguards described above, our cybersecurity policy requires employees and third party vendors to report any and all cybersecurity incidents to our IT department. Third-Party Risk Management We maintain a risk-based approach to identifying and overseeing cybersecurity risks presented by third parties, including vendors, service providers and other external users of the Company’s systems, as well as the systems of third parties that could materially impact our business in the event of a cybersecurity incident affecting those third-party systems. Depending on the nature of the services provided, we may conduct different amounts of diligence into the cybersecurity practices of the third party, monitor the third party for cybersecurity issues, and impose contractual obligations relating to privacy and cybersecurity onto the third party. Education and Awareness We provide regular (at least annual) training for personnel regarding cybersecurity threats to equip our personnel with effective tools to address cybersecurity threats, and to communicate the Company's evolving information security procedures. Current Cybersecurity Risk Posture For an additional description of the risks from cybersecurity threats that may materially affect the Company, see “Risk Factors” in this Annual Report on Form 10-K, including “ If our information technology systems or data, or those of third parties upon which we rely, are or were compromised by a cybersecurity incident, we could experience adverse consequences resulting from such compromise, including but not limited to regulatory investigations or actions; litigation; fines and penalties; disruptions of our business operations; reputational harm; loss of revenue or profits; and other adverse consequences.”
Cybersecurity Risk Management Third Party Engaged [Flag]	true
Cybersecurity Risk Third Party Oversight and Identification Processes [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Flag]	true
Cybersecurity Risk Materially Affected or Reasonably Likely to Materially Affect Registrant [Text Block]	For an additional description of the risks from cybersecurity threats that may materially affect the Company, see “Risk Factors” in this Annual Report on Form 10-K, including “ If our information technology systems or data, or those of third parties upon which we rely, are or were compromised by a cybersecurity incident, we could experience adverse consequences resulting from such compromise, including but not limited to regulatory investigations or actions; litigation; fines and penalties; disruptions of our business operations; reputational harm; loss of revenue or profits; and other adverse consequences.”
Cybersecurity Risk Board of Directors Oversight [Text Block]	Cybersecurity Governance and Responsibilities Our Board of Directors recognizes that cybersecurity represents an important component of the Company's overall enterprise risk management (“ERM”). Throughout the year, our Board of Directors and its Committees engage with management to discuss and mitigate a wide range of enterprise risks, including cybersecurity. We seek to mitigate cybersecurity risks through a cross-functional approach, including our Cybersecurity Committee, focused on preserving the confidentiality, security, and availability of the information that the Company collects and stores by identifying, preventing and mitigating cybersecurity threats and effectively responding to and remediating cybersecurity incidents as and if they occur. Our Cybersecurity Committee is comprised of information technology, finance, legal, human resources and data privacy employees. It meets regularly to review and oversee the Company’s data security programs, policies, and strategies, including with respect to cybersecurity risk mitigation, business continuity, and business resiliency. Our Cybersecurity Committee (along with the Chief Financial Officer and General Counsel) also reviews, analyzes, and responds to cybersecurity incidents and breaches. Our Audit Committee of the Board of Directors has the responsibility to review and discuss with management the Company’s guidelines, policies, and governance with respect to financial risk exposures and ERM (including with respect to cybersecurity) and to regularly report to the full Board. Our Audit Committee also oversees our internal audit department and management’s internal controls over financial reporting, including with respect to cybersecurity. Our Audit Committee receives regular presentations and reports on cybersecurity risks, progress on continued updates to the Company’s cybersecurity procedures, as well as is made aware, on a timely basis, of any cybersecurity incidents deemed significant enough to be raised to their attention by management, as well as ongoing updates regarding any such incident until it has been remediated. Our head of Information Technology (“IT”) oversees overall cybersecurity management and implements our cybersecurity programs with the IT group, including appropriate risk mitigation strategies, systems, processes, and controls and provides periodic reports to our Audit Committee at least semi-annually. The head of IT holds a Masters in Computer Information Systems and a Bachelor of Science degree in Microbiology, and has served in leadership roles within the pharmaceutical and biotechnology industries for over 25 years, including leading enterprise-wide cybersecurity strategies, regulatory compliance programs, and IT transformation initiatives at leading biopharmaceutical companies. The head of IT has expertise spanning cybersecurity governance, risk management, cloud security, AI-driven cybersecurity enhancements, infrastructure modernization, and enterprise-wide IT resilience. The head of IT plays a key role in aligning cybersecurity frameworks with industry regulations such as SOC compliance, SOX, GxP, and data privacy standards, ensuring a secure and compliant IT environment to support business objectives.
Cybersecurity Risk Board Committee or Subcommittee Responsible for Oversight [Text Block]	We seek to mitigate cybersecurity risks through a cross-functional approach, including our Cybersecurity Committee, focused on preserving the confidentiality, security, and availability of the information that the Company collects and stores by identifying, preventing and mitigating cybersecurity threats and effectively responding to and remediating cybersecurity incidents as and if they occur. Our Cybersecurity Committee is comprised of information technology, finance, legal, human resources and data privacy employees. It meets regularly to review and oversee the Company’s data security programs, policies, and strategies, including with respect to cybersecurity risk mitigation, business continuity, and business resiliency. Our Cybersecurity Committee (along with the Chief Financial Officer and General Counsel) also reviews, analyzes, and responds to cybersecurity incidents and breaches.
Cybersecurity Risk Process for Informing Board Committee or Subcommittee Responsible for Oversight [Text Block]	Our Cybersecurity Committee (along with the Chief Financial Officer and General Counsel) also reviews, analyzes, and responds to cybersecurity incidents and breaches.
Cybersecurity Risk Role of Management [Text Block]	Risk Management and Strategy We periodically assess and test our cybersecurity procedures. We identify and assess material risks from cybersecurity threats by engaging outside advisors and experts to identify, anticipate, and assess future threats and trends, to perform assessments on our cybersecurity risk and measures to mitigate such risk, including information security maturity assessments of our information security control environment. The results of such assessments and reviews are reported as appropriate to the Cybersecurity Committee and Audit Committee, and we adjust our cybersecurity procedures as necessary based on the information provided by these assessments and reviews. Cybersecurity Technical Safeguards We continually invest in information and cybersecurity services and technologies. Technical safeguards are designed to protect the Company's information systems from cybersecurity threats, including firewalls, continuous intrusion detection and response system(s), data leak prevention strategies, enhanced email protection software, antimalware functionality and access controls. These safeguards are evaluated and improved through periodic assessments and review of cybersecurity threat intelligence. We rely on third parties to support its cybersecurity program, including but not limited to email security management, security operations and vulnerability management. Cybersecurity Incident Response and Recovery Planning We have established and maintain incident response and data recovery plans that address our response to a cybersecurity incident. Our Cybersecurity Committee and members of the Cyber Security Incident Response Team (which contains additional information technology specialists) regularly test and evaluate the effectiveness of these incident response and data recovery plans. In addition to the incident detection safeguards described above, our cybersecurity policy requires employees and third party vendors to report any and all cybersecurity incidents to our IT department. Third-Party Risk Management We maintain a risk-based approach to identifying and overseeing cybersecurity risks presented by third parties, including vendors, service providers and other external users of the Company’s systems, as well as the systems of third parties that could materially impact our business in the event of a cybersecurity incident affecting those third-party systems. Depending on the nature of the services provided, we may conduct different amounts of diligence into the cybersecurity practices of the third party, monitor the third party for cybersecurity issues, and impose contractual obligations relating to privacy and cybersecurity onto the third party. Education and Awareness We provide regular (at least annual) training for personnel regarding cybersecurity threats to equip our personnel with effective tools to address cybersecurity threats, and to communicate the Company's evolving information security procedures. Current Cybersecurity Risk Posture For an additional description of the risks from cybersecurity threats that may materially affect the Company, see “Risk Factors” in this Annual Report on Form 10-K, including “ If our information technology systems or data, or those of third parties upon which we rely, are or were compromised by a cybersecurity incident, we could experience adverse consequences resulting from such compromise, including but not limited to regulatory investigations or actions; litigation; fines and penalties; disruptions of our business operations; reputational harm; loss of revenue or profits; and other adverse consequences.”
Cybersecurity Risk Management Positions or Committees Responsible [Flag]	true
Cybersecurity Risk Management Positions or Committees Responsible [Text Block]	Our Audit Committee of the Board of Directors has the responsibility to review and discuss with management the Company’s guidelines, policies, and governance with respect to financial risk exposures and ERM (including with respect to cybersecurity) and to regularly report to the full Board.
Cybersecurity Risk Management Expertise of Management Responsible [Text Block]	The head of IT holds a Masters in Computer Information Systems and a Bachelor of Science degree in Microbiology, and has served in leadership roles within the pharmaceutical and biotechnology industries for over 25 years, including leading enterprise-wide cybersecurity strategies, regulatory compliance programs, and IT transformation initiatives at leading biopharmaceutical companies. The head of IT has expertise spanning cybersecurity governance, risk management, cloud security, AI-driven cybersecurity enhancements, infrastructure modernization, and enterprise-wide IT resilience. The head of IT plays a key role in aligning cybersecurity frameworks with industry regulations such as SOC compliance, SOX, GxP, and data privacy standards, ensuring a secure and compliant IT environment to support business objectives.
Cybersecurity Risk Process for Informing Management or Committees Responsible [Text Block]	Our head of Information Technology (“IT”) oversees overall cybersecurity management and implements our cybersecurity programs with the IT group, including appropriate risk mitigation strategies, systems, processes, and controls and provides periodic reports to our Audit Committee at least semi-annually.
Cybersecurity Risk Management Positions or Committees Responsible Report to Board [Flag]	true

Net Loss Per Share

12 Months Ended

Dec. 31, 2025

Earnings Per Share [Abstract]

Net Loss Per Share

13. Net Loss Per Share

Potential common shares that would have the effect of increasing diluted earnings per share are considered to be anti-dilutive and as such, these shares are not included in the calculation of diluted earnings per share. The Company reported a loss from continuing operations for each of the years ended December 31, 2025 and 2024. Therefore, dilutive common shares are not assumed to have been issued since their effect is anti-dilutive for these periods.

Diluted weighted average shares excluded the following potential common shares related to stock options, RSUs, PRSUs, TSR awards and shares to be purchased under the 2014 Employee Stock Purchase Plan (“ESPP”) for the periods presented as they were anti-dilutive (in thousands):


	Years Ended December 31,
	2025		2024
Employee stock options		465		538
RSUs, PRSUs and TSR awards		33		125
ESPP		—		18
		498		681

Consolidated Variable Interest Entity - Fortis

12 Months Ended

Dec. 31, 2025

Business Combination [Abstract]

Consolidated Variable Interest Entity - Fortis

5. Consolidated Variable Interest Entity - Fortis

In May 2023 (the “Option Acquisition Date”), the Company entered into an exclusive option agreement to acquire Fortis Therapeutics (“Fortis”) with its novel Phase 1 ADC, FOR46 (now referred to as “FG-3246”), that targets a novel epitope on CD46 preferentially expressed on certain cancer cells. FG-3246 is in development for the treatment of mCRPC with potential applicability in other solid tumors and hematologic malignancies. If the Company exercises the option to acquire Fortis, it will pay Fortis an option exercise payment of $80.0 million, and thereafter, legacy Fortis shareholders would be eligible to receive from the Company up to $200.0 million in contingent payments associated with the achievement of various regulatory approvals. If the Company acquires Fortis, it would also be responsible to pay University of California, San Francisco (“UCSF”), an upstream licensor to Fortis, development milestone fees and a single digit royalty on net sales of therapeutic or diagnostic products arising from the licensing arrangement between Fortis and UCSF. If the Company chooses not to acquire Fortis, its exclusive license to FG-3246 would expire.

Pursuant to an evaluation agreement entered into with Fortis concurrent with the option agreement (together the “Fortis Agreements”), the Company has exclusively licensed FG-3246 and will control and fund future research, development, including a Phase 2 clinical study sponsored by the Company, and manufacturing of FG-3246 option period (which ends on December 31, 2027). As part of the clinical development strategy, the Company will continue the work to develop a PET-based biomarker utilizing a radiolabeled version of the targeting antibody for patient selection. Additionally, the Company is obligated to pay Fortis in support of its continued development activities, and the Company fulfilled such obligation with a last payment of $1.7 million in the first quarter of 2024.

Pursuant to the guidance under ASC 810, the Company determined that Fortis is a VIE and that the Company is the primary beneficiary of Fortis, as through the Fortis Agreements the Company has the power to direct activities that most significantly impact the economic performance of Fortis. Therefore, the Company consolidated Fortis starting from the Option Acquisition Date, and continues to consolidate as of December 31, 2025.

The transaction was accounted for as an asset acquisition under ASC 805, Business Combinations, as substantially all of the fair value of the gross assets acquired is concentrated in a single identifiable in-process research and development (“IPR&D”) asset. The fair value of the consideration transferred was zero. The Company determined that the above mentioned quarterly payments to support Fortis’ continued development obligations should not be included in the purchase consideration, as those payments are payable to Fortis rather than to its shareholders.

Fortis has authorized and issued common shares and Series A preferred shares. The Company owned approximately 2% of Fortis’ Series A preferred shares, which was acquired prior the Option Acquisition Date and carried at zero cost. The NCI attributable to the common shares is classified as nonredeemable NCI, as it is 100% owned by third party shareholders.The NCI attributable to the approximately 98% of Series A preferred shares owned by other investors are classified as redeemable NCI in temporary equity, as the preferred shares are redeemable by the non-controlling shares holders upon occurrence of certain events out of the Company’s control.

Subsequent to the Option Acquisition Date, Fortis’ net income is allocated to its common shares and preferred shares based on their respective stated rights. Fortis’ net loss is allocated to its common shares only as the holders of preferred shares do not have a contractual obligation to absorb such losses.

The Company expensed fair value of the acquired IPR&D assets as research and development expense in 2023. The fair value of Fortis (enterprise value) and the fair value of nonredeemable NCI and redeemable NCI were determined based on the above-mentioned option exercise payment of $80.0 million and contingent payments up to $200.0 million, weighted with probability and expected timing of the underlying events, and discounted by the Company’s estimated market level cost of debt.

As of December 31, 2025 and 2024, total assets and liabilities of Fortis were immaterial. For the years ended December 31, 2025 and 2024, Fortis’ net income (losses) was immaterial.

Balance Sheet Components - Schedule of Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Cash and Cash Equivalents [Abstract]
Cash	$ 2,309	$ 2,004
Commercial paper	11,272	14,269
Money market funds	24,302	28,241
U.S. government bonds	9,989	5,968
Total cash and cash equivalents	$ 47,872	$ 50,482

- Definition

Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Excludes cash and cash equivalents within disposal group and discontinued operation.

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+ Details

Schedule II - Valuation and Qualifying Accounts

12 Months Ended

Dec. 31, 2025

SEC Schedule, 12-09, Valuation and Qualifying Accounts [Abstract]

Schedule II - Valuation and Qualifying Accounts

Schedule II: Valuation and Qualifying Accounts

(in thousands)


						Charged
			Charged			to Other
	Balance at		(Credited)			Accounts -
	Beginning of		to Statement			Liabilities		Deductions,		Balance at
	Year		of Operation			and Equity		Net		End of Year
Valuation allowances for deferred tax assets
Year ended December 31, 2025	$	452,740	$	(65,185	)	$	—	$	—	$	387,555
Year ended December 31, 2024	$	426,355	$	26,385		$	—	$	—	$	452,740

Consolidated Variable Interest Entity - Fortis - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	May 31, 2023	Mar. 31, 2024	Dec. 31, 2025
Third Party Shareholders [Member] \| Nonredeemable NCI [Member]
Business Combination [Line Items]
Ownership percentage	100.00%		100.00%
Other Investors [Member] \| Nonredeemable NCI [Member]
Business Combination [Line Items]
Ownership percentage	98.00%		98.00%
Series A Preferred Shares [Member] \| Nonredeemable NCI [Member]
Business Combination [Line Items]
Ownership percentage	2.00%		2.00%
Fortis Therapeutics [Member]
Business Combination [Line Items]
Purchase consideration	$ 0
Payment to options exercised	80,000
Contingent payment associated with business acquisition	$ 200,000
Product development obligations		$ 1,700

Fair Value Measurements (Tables)

12 Months Ended

Dec. 31, 2025

Fair Value Disclosures [Abstract]

Fair Values of Financial Assets Measured on Recurring Basis

The fair values of the Company’s financial assets that are measured on a recurring basis are as follows (in thousands):


	December 31, 2025
	Level 1		Level 2		Level 3		Total
Money market funds	$	24,302	$	—	$	—	$	24,302
Corporate bonds		—		27,817		—		27,817
Commercial paper		—		17,797		—		17,797
U.S. government bonds		31,922		4,991		—		36,913
Total	$	56,224	$	50,605	$	—	$	106,829

	December 31, 2024
	Level 1		Level 2		Level 3		Total
Money market funds	$	28,241	$	—	$	—	$	28,241
Commercial paper		—		14,269		—		14,269
U.S. government bonds		2,987		2,981		—		5,968
Total	$	31,228	$	17,250	$	—	$	48,478

Segment and Geographic Information - Additional information (Detail)	12 Months Ended
	Dec. 31, 2025 Segment
Segment Reporting [Abstract]
Number of operating segment	1
Number of reportable segment	1
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description	The CODM assesses performance of the business, monitors budget versus actual results and manages and allocates resources to the Company’s operations using consolidated net income (loss) as the primary measurement.

Collaboration Agreements, License Agreement and Revenues - Roll-forward of Related Contract Liabilities (Detail) $ in Thousands	12 Months Ended
	Dec. 31, 2025 USD ($)
AstraZeneca Agreements [Member]
Contract with Customer Liability [Line Items]
Balance at December 31, 2024	$ (132,097)
Additions	(82,494)
Recognized as Revenue (Discontinued Operations)	218,575
Currency Translation and Other	(3,984)
Balance at December 31, 2025	0
Drug Product Revenue, Net [Member] \| Astellas Agreement [Member] \| Europe [Member]
Contract with Customer Liability [Line Items]
Balance at December 31, 2024	(9,901)
Additions	(2,210)
Recognized as Revenue	4,778
Reclassified to accrued liability / accounts payable	1,764
Balance at December 31, 2025	$ (5,569)

Commitments and Contingencies - Additional Information (Detail) $ in Thousands	1 Months Ended	2 Months Ended
	May 31, 2025 USD ($)	May 31, 2021 PutativeClassAction	Dec. 31, 2025 USD ($)	Oct. 17, 2023 USD ($)
Commitments And Contingencies [Line Items]
Number of complaints filed \| PutativeClassAction		5
Litigation settlement amount				$ 28,500
Civil penalty payment	$ 1,250
General Purchases And Other Programs [Member]
Commitments And Contingencies [Line Items]
Recorded unconditional purchase obligation			$ 3,300
Manufacture and Supply of Roxadustat [Member]
Commitments And Contingencies [Line Items]
Recorded unconditional purchase obligation			$ 2,300

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Operating activities
Net income (loss)	$ 183,452	$ (47,579)
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation	713	2,654
Amortization of finance lease right-of-use assets	35	38
Net accretion of premium and discount on investments	(72)	(1,680)
Investment income in unconsolidated variable interest entity	(2,485)	(3,969)
Gain on divestiture	(52,553)	0
Loss on debt extinguishments	6,583	0
Impairment of property and equipment	2,062	0
Loss on disposal of property and equipment	0	2,551
Stock-based compensation	6,576	25,215
Dividend received from unconsolidated variable interest entity	3,947	2,230
Changes in operating assets and liabilities:
Accounts receivable, net	(2,543)	(6,737)
Inventories	5,362	22,284
Prepaid expenses and other current assets	54,102	(15,550)
Operating lease right-of-use assets	808	66,306
Other assets	(902)	1,010
Accounts payable	(27,654)	14,512
Accrued and other liabilities	(53,497)	(93,790)
Operating lease liabilities, current	(568)	(12,774)
Deferred revenues	(136,429)	(28,297)
Accrued interest expense related to sale of future revenues	7,990	2,257
Accrued interest for finance lease liabilities	6	14
Operating lease liabilities, non-current	(202)	(66,154)
Other long-term liabilities	495	(540)
Net cash used in operating activities	(4,774)	(137,999)
Investing activities
Purchases of property and equipment	(38)	(266)
Proceeds from divestiture, net of cash transferred	96,615	0
Proceeds from sale of property and equipment	0	1,046
Purchases of available-for-sale securities	(61,158)	(8,628)
Proceeds from maturities of investments	0	133,841
Net cash provided by investing activities	35,419	125,993
Financing activities
Repayments of senior secured term loan facilities	(75,000)	0
Payment of senior secured term loan facilities pay-off premium and fees	(5,550)	0
Repayments of finance lease liabilities	(10)	(40)
Cash paid for payroll taxes on restricted stock unit releases	(69)	(354)
Cash paid to non-controlling interest	(5,353)	0
Payment of issuance cost under ATM Program	(46)	0
Proceeds from issuance of common stock under employee stock plans	0	139
Net cash used in financing activities	(86,028)	(255)
Effect of exchange rate change on cash and cash equivalents	1,077	751
Net decrease in cash and cash equivalents	(54,306)	(11,510)
Total cash and cash equivalents at beginning of period	102,178	113,688
Total cash and cash equivalents at end of period	47,872	102,178
Supplemental cash flow information:
Holdback consideration receivable related to divestiture in prepaid expenses and other current assets	4,000
Interest payments	7,830	16,207
Reconciliation of cash and cash equivalents to the consolidated balance sheets:
Cash and cash equivalents of continuing operations	47,872	50,482
Cash and cash equivalents included in assets held for sale	0	51,696
Total cash and cash equivalents in the consolidated statements of cash flows	$ 47,872	$ 102,178

Senior Secured Term Loan Facilities (Table)

12 Months Ended

Dec. 31, 2025

Debt Disclosure [Abstract]

Summary of Senior Secured Term Loan Facilities

The Company’s senior secured term loan facilities as of December 31, 2024 were as follows (in thousands):


	December 31, 2024
Principal of senior secured term loan facilities	$	75,000
Less: Unamortized issuance costs and transaction costs		(1,908	)
Senior secured term loan facilities, ending balance	$	73,092
Representing:
Senior secured term loan facilities, current	$	—
Senior secured term loan facilities, non-current	$	73,092

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.5-02(22))
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Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
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-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
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Reference 5: http://www.xbrl.org/2003/role/exampleRef
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-Section 55
-Paragraph 69B
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Reference 6: http://www.xbrl.org/2003/role/exampleRef
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Reference 7: http://www.xbrl.org/2009/role/commonPracticeRef
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-Name Accounting Standards Codification
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+ Details

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Basis of Presentation

The consolidated financial statements have been prepared in accordance with accounting principles generally accepted in the U.S. (“U.S. GAAP”). The consolidated financial statements include the accounts of the Company, its wholly owned subsidiaries and its majority-owned subsidiaries, as well as any variable interest entity (“VIE”) for which Kyntra Bio is the primary beneficiary. All inter-company transactions and balances have been eliminated in consolidation.

The Company operates in one reportable segment — the development and commercialization of novel therapeutics to treat serious unmet medical needs.

Discontinued Operations

On February 20, 2025, the Company entered into the Share Purchase Agreement with AstraZeneca Treasury Limited pursuant to which the Company and its subsidiary FibroGen China Anemia Holdings, Ltd. agreed to sell all of the issued and outstanding equity interests of FibroGen International to AstraZeneca Treasury Limited (the “Transaction”). This sale includes all of the Company’s roxadustat assets in China, including FibroGen International’s subsidiary FibroGen Beijing and its 51.1% interest in Falikang. The Transaction was closed on August 29, 2025 for a total consideration of $220.4 million, subject to certain customary adjustments as set forth in the purchase agreement, comprised of $85.0 million in enterprise value and $135.4 million in net cash held in China.

The Company analyzed the quantitative and qualitative factors and concluded that the sale of FibroGen International represents a strategic shift in the Company’s business and qualified as a discontinued operation since December 31, 2024. As a result, the Company determined that FibroGen International met the “held for sale” criteria and the “discontinued operations” criteria in accordance with Financial Accounting Standard Board (“FASB”) Accounting Standards Codification (“ASC”) 205, Presentation of Financial Statements. Accordingly, the operating results related to FibroGen International are classified as discontinued operations, and have been reflected as discontinued operations in the consolidated statements of operations for all periods presented, and therefore, the consolidated statements of operations and the notes to the consolidated financial statements were recasted for all comparative periods presented to classify FibroGen International as discontinued operations. In addition, the related assets and liabilities were classified within the consolidated balance sheets as held for sale for each balance sheet date before the Transaction closed since December 31, 2024. See Note 3, Discontinued Operations and Divestiture, for related disclosures. Unless otherwise noted, discussion in the notes to the consolidated financial statements, relates to solely to the Company’s continuing operations.

Reverse Stock Split

On June 16, 2025, the Company effected a 1-for-25 reverse stock split (the “Reverse Stock Split”). The Reverse Stock Split reduced the number of issued and outstanding shares of common stock from approximately 101.1 million shares to approximately 4.0 million shares. Proportionate adjustments have been made to the number of shares available for issuance under the Company’s equity incentive plans as well as outstanding equity awards, in accordance with their respective terms. All share amounts have been retroactively adjusted in the consolidated financial statements and the notes to the consolidated financial statements, where applicable, to reflect the Reverse Stock Split.

Liquidity and Going Concern

The consolidated financial statements are prepared in accordance with the U.S. GAAP applicable to a going concern, which contemplates the realization of assets and the satisfaction of liabilities in the normal course of business and does not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of the uncertainties described below.

As disclosed in previous filings (including the September 30, 2024 Form 10-Q and subsequent December 31, 2024 Form 10-K, March 31, 2025 Form 10-Q and June 30, 2025 Form 10-Q), if the Company was unable to complete the above mentioned sale of FibroGen International, access additional cash from its China operations, or raise additional capital in the U.S., the Company would not have sufficient liquidity to continue operations in the U.S. for the 12 months from the date that the financial statements were issued and would not be able to comply with its financial covenant that required a minimum balance of unrestricted cash and cash equivalents to be held in accounts in the U.S. Upon an event of default, the Company’s senior secured term loan facilities with Morgan Stanley Tactical Value (“MSTV”) would become immediately due and payable. These factors had raised substantial doubt about the Company’s ability to continue as a going concern.

On August 29, 2025, upon the Transaction close, the Company received cash for the sale of $210.4 million and repaid its senior secured term loan facilities with MSTV, outstanding interest and related premium and fees for approximately $80.9 million. With the cash proceeds from the Transaction close, based on its current operating plan, the Company believes that its existing cash and cash equivalents will be sufficient to fund the Company’s planned operating requirements for at least the 12 months following the issuance of the financial statements for December 31, 2025 and concluded that the conditions and events that initially raised substantial doubt have been alleviated and that substantial doubt does not exist as of issuance.

Foreign Currency Translation

The reporting currency of the Company and its subsidiaries is the U.S. dollar.

The functional currency of FibroGen Europe is the Euro. The functional currency of FibroGen Beijing, a part of the above-mentioned discontinued operations, is CNY. As such, monetary assets and liabilities of FibroGen Europe and FibroGen Beijing in currencies other than their functional currencies are remeasured using exchange rates in effect at the end of the period. The assets and liabilities of FibroGen Europe and FibroGen Beijing are translated to U.S. dollars at exchange rates in effect at the balance sheet date. All income statement accounts are translated at monthly average exchange rates. Resulting foreign currency translation adjustments are recorded directly in accumulated other comprehensive income (loss) as a separate component of stockholders’ equity (deficit).

The functional currency of Kyntra Bio, Inc. and all other subsidiaries is the U.S. dollar. Accordingly, monetary assets and liabilities in the non-functional currency of these subsidiaries are remeasured using exchange rates in effect at the end of the period. Revenues and costs in local currency are remeasured using average exchange rates for the period, except for costs related to those balance sheet items that are remeasured using historical exchange rates. The resulting remeasurement gains and losses are included within interest income and other, net in the consolidated statements of operations as incurred and have not been material for all periods presented.

Use of Estimates

The preparation of the consolidated financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and reported amounts of revenues and expenses during the reporting period. The more significant areas requiring the use of management estimates and assumptions include valuation and recognition of revenue and deferred revenue, specifically, estimates in variable consideration for drug product sales, and estimates in transaction price per unit for the China Performance Obligation (as defined and discussed under Revenue Recognition below), which was completed during the third quarter of 2025 upon the above-mentioned Transaction close. On an ongoing basis, management reviews these estimates and assumptions. Changes in facts and circumstances may alter such estimates and actual results could differ from those estimates.

Concentration of Credit Risk

The Company is subject to risks associated with concentration of credit for cash and cash equivalents. Outside of short-term operating needs, cash on hand is invested in commercial paper, money market funds and U.S. government securities. Any remaining cash is deposited with major financial institutions primarily in the U.S. At times, such deposits may be in excess of insured limits. The Company has not experienced any loss on its deposits of cash and cash equivalents. As of December 31, 2025 and 2024, the accounts receivable was not material.

Other Risks and Uncertainties

The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, the results of clinical trials and the achievement of milestones, research developments, actions by regulatory authorities, market acceptance of the Company’s product candidates, competition from other products and larger companies, the liquidity and capital resources of the Company, intellectual property protection for the Company's proprietary technology, strategic relationships, and dependence on key individuals, suppliers, clinical organization, and other third parties.

Cash, Cash Equivalents

The Company considers all highly liquid investments with maturities of three months or less at the date of purchase to be cash equivalents. Cash and cash equivalents also include certain money market accounts, commercial paper and U.S. government securities.

Investments

As of December 31, 2025, the Company’s short-term investments consist of diversified bonds, commercial paper, and money market funds with original maturities of greater than three months and remaining maturities of less than 12 months (365 days) are considered. Any investments with maturities greater than 12 months (365 days) from the balance sheet date are considered long-term investments. When such investments are held, the Company’s investments classified as available-for-sale are recorded at fair value based upon quoted market prices at period end. Unrealized gains and losses for available-for-sale debt investments that are deemed temporary in nature are recorded in accumulated other comprehensive income (loss) as a separate component of stockholder’ equity. Realized and unrealized gains or losses resulting from changes in value and sale of the Company’s marketable equity investments are recorded in other income (expenses) in the consolidated statement of operations.

A decline in the fair value of any security below cost that is deemed other than temporary results in a charge to earnings and the corresponding establishment of a new cost basis for the security. Premiums and discounts are amortized (accreted) over the life of the related security as an adjustment to its yield. Dividend and interest income are recognized when earned. Realized gains and losses are included in earnings and are derived using the specific identification method for determining the cost of investments sold.

Trade Accounts Receivable

Trade accounts receivable

The allowance for credit losses is based on the Company’s assessment of the collectability of customer accounts. The Company makes estimates of expected credit losses for the allowance for doubtful accounts by considering factors such as historical experience, credit quality, the age of the accounts receivable balances, current economic and regulatory conditions that may affect a customer’s ability to pay, and estimates of expected future losses. The Company’s bad debt expense for the years ended December 31, 2025 and 2024 and the allowance for credit losses as of December 31, 2025 and 2024 were immaterial.

Credit Losses – Available-For-Sale Debt Securities

Credit losses – Available-for-sale debt securities

The Company periodically assesses its available-for-sale investments for other-than-temporary impairment. For debt securities in an unrealized loss position, the Company first considers its intent to sell, or whether it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis. If either of these criteria are met, the amortized cost basis of such debt securities is written down to fair value through interest and other, net.

For debt securities in an unrealized loss position that do not meet the aforementioned criteria, the Company assesses whether the decline in the fair value of such debt securities has resulted from credit losses or other factors. The Company considers the extent to which fair value is less than amortized cost, any changes to the rating of the security by a rating agency, and any adverse conditions specifically related to the securities, among other factors. If this assessment indicates that a credit loss may exist, the Company then compares the present value of cash flows expected to be collected from such securities to their amortized cost basis. If the present value of cash flows expected to be collected is less than the amortized cost basis, a credit loss exists and an allowance for credit losses is recorded through interest and other, net, limited by the amount that the fair value is less than the amortized cost basis. Any additional impairment not recorded through an allowance for credit losses is recognized in other comprehensive income.

Changes in the allowance for credit losses are recorded as provision for, or reversal of, credit loss expense. Losses are charged against the allowance when the Company believes that an available-for-sale security is confirmed uncollectable or when either of the criteria regarding intent or requirement to sell is met.

Inventories

Inventories are stated at the lower of cost or net realizable value, on a first-in, first-out, or FIFO, basis. The Company’s inventories uses actual costs to determine its cost basis. The cost of inventories includes direct material cost, direct labor and manufacturing overhead.

When the technical feasibility of the Company’s future commercialization is considered probable and the future economic benefit is expected to be realized, based on management’s judgment, the Company capitalizes pre-launch inventory costs prior to regulatory approval. A number of factors are considered, including the status in the validation process in significant jurisdictions, regulatory application and approval process, and terms and condition for future sale of such inventory or future alternative use. The pre-launch inventory cost includes purchase cost of raw materials, cost paid to contract manufacturers for inventory manufacturing, freight and custom charges, and certain direct internal labor and overhead expenses.

The Company periodically reviews its inventories to identify obsolete, slow-moving, excess or otherwise unsaleable items. If obsolete, excess or unsaleable items are observed and there are no alternate uses for the inventory, an inventory valuation adjustment is recorded through a charge to cost of goods sold on the Company’s consolidated statements of operations. Inventory valuation adjustments require judgment including consideration of many factors, such as estimates of future product demand and product expiration period, among others.

Variable Interest Entity

Under the Accounting Standards Codification (“ASC”) 810, Consolidation (“ASC 810”), when the Company obtains an economic interest in an entity, it evaluates the entity to determine if it should be deemed a VIE, and, if so, whether the Company is the primary beneficiary and is therefore required to consolidate the VIE, based on significant judgment whether the Company (i) has the power to direct the activities that most significantly impact the economic performance of the VIE and (ii) has the obligation to absorb losses or the right to receive benefits of the VIE that could potentially be significant to the VIE.

On an ongoing basis, the Company re-evaluates the VIE assessment based on potential changes in facts and circumstances, including but not limited to, the shareholder loans to the entity and the execution of any future significant agreements between the entity and its shareholders and/or other third parties.

The Company accounts for the sale of future revenue as a debt, because the risks and rewards to the investor are limited by the terms of the transaction as discussed further in Note 9, Liability Related to Sale of Future Revenues. The difference between the carrying amount of the initial liability and the gross proceeds received is accounted for as a discount. The Company recognizes interest expense based on an estimated effective annual interest rate, which is affected by the amount and timing of revenues recognized and changes in the timing of forecasted revenues. Quarterly, the Company reassesses the expected revenues and the timing of such revenues, recalculates the amortization and effective interest rate and adjusts the accounting prospectively as needed

Revenue Recognition

Revenues under collaboration agreements

The Company’s collaboration agreements include multiple performance obligations comprised of promised services, or bundles of services, that are distinct. Services that are not distinct are combined with other services in the agreement until they form a distinct bundle of services. The Company’s process for identifying performance obligations and an enumeration of each obligation for each agreement is outlined in Note 4, Collaboration Agreements, License Agreement and Revenues. Determining the performance obligations within a collaboration agreement often involves significant judgment and is specific to the facts and circumstances contained in each agreement.

The Company has identified the following material promises under its collaboration agreements: (1) license of the Company’s technology, (2) the performance of co-development services, including manufacturing of clinical supplies and other services during the development period, and (3) manufacture of commercial supply. The evaluation as to whether these promises are distinct, and therefore represent separate performance obligations, is described in more detail in Note 4, Collaboration Agreements, License Agreement and Revenues.

For revenue recognition purposes, the Company determines that the terms of its collaboration agreements begin on the effective date and end upon the completion of all performance obligations contained in the agreements. In each agreement, the contract term is defined as the period in which parties to the contract have present and enforceable rights and obligations. The Company believes that the existence of what it considers to be substantive termination penalties on the part of the counterparty create sufficient incentive for the counterparty to avoid exercising its right to terminate the agreement.

The transaction price for each collaboration agreement is determined based on the amount of consideration the Company expects to be entitled for satisfying all performance obligations within the agreement. The Company’s collaboration agreements include payments to the Company of one or more of the following: non-refundable upfront license fees; co-development billings; development, regulatory, and commercial milestone payments; payments from sales of active pharmaceutical ingredient (“API”); payments from sales of bulk drug product and royalties on net sales of licensed products.

Upfront license fees are non-contingent and non-refundable in nature and are included in the transaction price at the point when the license fees become due to the Company. The Company does not assess whether a contract has a significant financing component if the expectation at contract inception is such that the period between payment by the customer and the transfer of the promised goods or services to the customer will be one year or less.

Co-development billings resulting from the Company’s research and development efforts, which are reimbursable under its collaboration agreements, are considered variable consideration. Determining the reimbursable amount of research and development efforts requires detailed analysis of the terms of the collaboration agreements and the nature of the research and development efforts incurred. Prior to CKD approval in the third quarter of 2021, determining the amount of variable consideration from co-development billings required the Company to make estimates of future research and development efforts, which involved significant judgment. Co-development billings are allocated entirely to the co-development services performance obligation when amounts are related specifically to research and development efforts necessary to satisfy the performance obligation, and such an allocation is consistent with the allocation objective.

Milestone payments are also considered variable consideration, which requires the Company to make estimates of when achievement of a particular milestone becomes probable. Similar to other forms of variable consideration, milestone payments are included in the transaction price when it becomes probable that such inclusion would not result in a significant revenue reversal. Milestones are therefore included in the transaction price when achievement of the milestone becomes probable.

For arrangements that include sales-based royalties and for which the license is deemed to be the predominant item to which the royalties relate, the Company recognizes revenue at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied).

The transaction price is allocated to performance obligations based on their relative standalone selling price (“SSP”), with the exception of co-development billings allocated entirely to co-development services performance obligations. The SSP is determined based on observable prices at which the Company separately sells the products and services. If an SSP is not directly observable, then the Company will estimate the SSP considering marketing conditions, entity-specific factors, and information about the customer or class of customer that is reasonably available. The process for determining SSP involves significant judgment and includes consideration of multiple factors, including assumptions related to the market opportunity and the time needed to commercialize a product candidate pursuant to the relevant license, estimated direct expenses and other costs, which include the rates normally charged by contract research and contract manufacturing organizations for development and manufacturing obligations, and rates that would be charged by qualified outsiders for committee services.

Significant judgment may be required in determining whether a performance obligation is distinct, determining the amount of variable consideration to be included in the transaction price, and estimating the SSP of each performance obligation. An enumeration of the Company’s significant judgments is outlined in Note 4, Collaboration Agreements, License Agreement and Revenues.

For each performance obligation identified within an arrangement, the Company determines the period over which the promised services are transferred and the performance obligation is satisfied. Service revenue that was recognized over time was based on progress toward complete satisfaction of the performance obligation. For each performance obligation satisfied over time, the Company assesses the proper method to be used for revenue recognition, either an input method to measure progress toward the satisfaction of services or an output method of determining the progress of completion of performance obligation.

Drug product revenue

Drug product revenue includes commercial-grade API or bulk drug product sales to AstraZeneca and Astellas in support of pre-commercial preparation prior to the New Drug Application (“NDA”) or Marketing Authorization Application approval, and to Astellas for ongoing commercial activities in Japan and Europe. Drug product revenue is recognized when the Company fulfills the inventory transfer obligations.

The amount of variable consideration that is included in the transaction price may be constrained, and is included in the drug product revenue only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period when the uncertainty associated with the variable consideration is subsequently resolved. Estimating variable consideration and the related constraint requires the use of significant management judgment. The Company reviews new information that may affect its variable consideration estimate at every reporting period and records revenue adjustment, if certain and material. Actual amounts of consideration ultimately received in the future may differ from the Company’s estimates, for which the Company will adjust these estimates and affect the drug product revenue in the period such variances become known.

As each of the Company’s collaboration agreements provide for annual true up to the considerations paid for its commercial supplies, the Company will re-evaluate the transaction price in each reporting period and record adjustment to revenue as uncertain events are resolved or other changes in circumstances occur.

China Performance Obligation

Product revenue, net, which is included in the discontinued operations, consists primarily of revenues from sales of roxadustat commercial product to Falikang. Falikang is jointly owned by AstraZeneca and FibroGen Beijing.

Falikang is FibroGen Beijing’s primary customer in China and substantially all roxadustat product sales to distributors in China are made by Falikang. Falikang bears inventory risk once it receives and accepts the product from FibroGen Beijing, and is responsible for delivering product to its distributors.

The promises identified under the AstraZeneca China Agreement (as defined in Note 4, Collaboration Agreements, License Agreement and Revenues), including the license, co-development services and manufacturing of commercial supplies have been bundled into a single performance obligation (“China Performance Obligation”). Amounts of the transaction price allocable to this performance obligation under the Company’s agreements with AstraZeneca as outlined in Note 4, Collaboration Agreements, License Agreement and Revenues, are deferred until control of the manufactured commercial product is transferred to AstraZeneca.

The initiation of roxadustat sales to Falikang marks the beginning of the China Performance Obligation. Revenue is recognized at a point in time when control of roxadustat commercial product is transferred to Falikang. Revenue is recognized based on the estimated transaction price per unit and actual quantity of product delivered during the reporting period. Specifically, the transaction price per unit is determined based on the overall transaction price over the total estimated sales quantity for the estimated performance period in which the Company determined it is likely those sales would occur. The price per unit is subject to reassessment on a quarterly basis, which may result in cumulative catch up adjustments due to changes in estimates.

The overall transaction price for FibroGen Beijing’s product sales to Falikang includes the following elements of consideration:

•

Non-refundable upfront license fees; development, regulatory, and commercial milestone payments based on the AstraZeneca China Agreement allocated to the China Performance Obligation;

•

Co-development billings resulting from the Company’s research and development efforts, which are reimbursable under the AstraZeneca China Agreement;

•

Interim profit/loss share between FibroGen Beijing and AstraZeneca from April 1, 2020 through December 31, 2020; and

•

Net transaction price from product sales to Falikang from January 1, 2021 onwards. The net transaction price includes the following elements:

Gross transaction price: The gross transaction price is based on a percentage of Falikang’s net sales to its distributors, which takes into account Falikang’s operating expenses and its payments to AstraZeneca for roxadustat sales and marketing efforts, capped at a percentage of Falikang’s net roxadustat sales.

Profit share: The gross transaction price is then adjusted for an estimated amount to achieve the 50/50 profit share from current period roxadustat net sales in China. The adjustments to date have been a reduction to the transaction price and the related accounts receivable from Falikang.

The non-refundable upfront license fees constitute a fixed consideration. The remainder of the above are variable consideration components, which may be constrained, and included in the transaction price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period when the uncertainty associated with the variable consideration is subsequently resolved. The calculation of the above variable consideration includes significant assumptions such as total sales quantity, performance period, gross transaction price and profit share, which require significant judgment.

Any net transaction price in excess of the revenue recognized is deferred, and will be recognized over future periods as the performance obligations are satisfied. As of December 31, 2024, the related deferred revenues were not included in the disposal group held for sale as the related obligation to AstraZeneca would be satisfied upon the closing of the divestiture FibroGen International. The divestiture of FibroGen International was completed on August 29, 2025 and accordingly, the performance obligation to AstraZeneca was completely satisfied upon the closing of the divestiture. As a result, all the previously deferred revenues were recognized as revenue during the year ended December 31, 2025. The product revenue recognized under the China Performance Obligation is included in discontinued operations for all periods presented. See Note 3, Discontinued Operations and Divestiture, for more details.

Research and Development Expenses

Research and development expenses consist of independent research and development costs and the gross amount of costs associated with work performed under collaboration agreements. Research and development costs include employee-related expenses, expenses incurred under agreements with clinical research organizations, other clinical and preclinical costs and allocated direct and indirect overhead costs, such as facilities costs, information technology costs and other overhead. All research and development costs are expensed as incurred.

Clinical Trial Accruals

Clinical trial costs are a component of research and development expenses. The Company accrues and expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company determines the costs to be recorded based upon validation with the external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.

Selling, General and Administrative Expenses

Selling, general and administrative (“SG&A”) expenses consist primarily of employee-related expenses for executive, operational, finance, legal, compliance and human resource functions. SG&A expenses also include facility-related costs, professional fees, accounting and legal services, other outside services, recruiting fees and expenses associated with obtaining and maintaining patents.

Restructuring Charge

A restructuring charge is recognized when the liability is incurred and accrued in the period in which it is probable that the employees are entitled to the restructuring benefits and the amounts can be reasonably estimated. The restructuring liability accrued but not paid at the end of the reporting period is included in accrued and other current liabilities in the consolidated balance sheets.

Income Taxes

The Company utilizes the asset and liability method of accounting for income taxes, which requires the recognition of deferred tax assets and liabilities for expected future consequences of temporary differences between the financial reporting and income tax bases of assets and liabilities using enacted tax rates. Management makes estimates, assumptions and judgments to determine the Company’s provision for income taxes and for deferred tax assets and liabilities, and any valuation allowances recorded against the Company’s deferred tax assets. The Company assesses the likelihood that its deferred tax assets will be recovered from future taxable income and, to the extent the Company believes that recovery is not likely, the Company must establish a valuation allowance.

The calculation of the Company’s current provision for income taxes involves the use of estimates, assumptions and judgments while taking into account current tax laws, interpretation of current tax laws and possible outcomes of future tax audits. The Company has established reserves to address potential exposures related to tax positions that could be challenged by tax authorities. Although the Company believes its estimates, assumptions and judgments to be reasonable, any changes in tax law or its interpretation of tax laws and the resolutions of potential tax audits could significantly impact the amounts provided for income taxes in the Company’s consolidated financial statements.

The calculation of the Company’s deferred tax asset balance involves the use of estimates, assumptions and judgments while taking into account estimates of the amounts and type of future taxable income. Actual future operating results and the underlying amount and type of income could differ materially from the Company’s estimates, assumptions and judgments thereby impacting the Company’s financial position and results of operations.

The Company has adopted ASC 740-10, Accounting for Uncertainty in Income Taxes, that prescribes a recognition threshold and measurement attribute for the financial statement recognition and measurement of uncertain tax positions taken or expected to be taken in the Company’s income tax return, and also provides guidance on derecognition, classification, interest and penalties, accounting in interim periods, disclosure and transition.

The Company includes interest and penalties related to unrecognized tax benefits within income tax expense in the Consolidated Statements of Operations.

Stock-Based Compensation

The Company maintains equity incentive plans under which equity awards are granted to employees, which are comprised of stock options, service-based restricted stock units (“RSUs”), performance-based RSUs (“PRSUs”), and total shareholder return (“TSR”) awards.

The Company measures and recognizes compensation expense for all stock options, RSUs and PRSUs granted to its employees and directors based on the estimated fair value of the award on the grant date. The Company uses the Black-Scholes valuation model to estimate the fair value of stock option awards. The determination of the grant date fair value of options using the Black-Scholes valuation model is affected by the Company’s estimated common stock fair value and requires management to make a number of assumptions including the expected life of the option, the volatility of the underlying stock, the risk-free interest rate and expected dividends. The Company determines the fair value of RSUs and PRSUs using the fair value of its common stock on the date of grant. To estimate the fair value of the TSR awards, the Company uses the Monte Carlo valuation model to simulate the probabilities of achievement, which requires management to make a number of assumptions including 30-day average price, volatility of the underlying stock and the Company’s peers, and the risk-free interest rate.

The compensation cost of service-based stock options and restricted stock units is recognized net of any estimated forfeitures on a straight-line basis over the employee requisite service period. Compensation cost for PRSUs is expensed over the respective vesting periods when the achievement of performance criteria is probable. Compensation cost for the TSR awards is recognized over the requisite service period, regardless of when, if ever, the market condition is satisfied.

The Company believes that the fair value of stock options granted to non-employees is more reliably measured than the fair value of the services received.

The Company estimates the fair value of stock options using the Black-Scholes option valuation model. The fair value of employee stock options and RSUs is being amortized on a straight-line basis over the requisite service period of the awards. Compensation cost for PRSUs is expensed over the respective vesting periods when the achievement of performance criteria is probable. The Company estimates the fair value of the TSR awards using the Monte Carlo valuation model to simulate the probabilities of achievement. Compensation cost for the TSR awards is recognized over the requisite service period, regardless of when, if ever, the market condition is satisfied. The fair market value of common stock is based on the closing price of the Company’s common stock as reported on the Nasdaq Global Select Market on the date of the grant.

The fair value of employee stock-based compensation is estimated using the following assumptions:

•

Expected Term. Expressed as a weighted-average, the expected life of the options is based on the average period the stock options are expected to be outstanding and was based on the Company’s historical information of the option exercise patterns and post-vesting termination behavior as well as contractual terms of the instruments. The expected term of 2014 ESPP shares is the average of the remaining purchase periods under each offering period. The expected term of TSR awards is determined based on the grant date to the end of the performance period.

•

Expected Volatility. The Company considers its historical volatility data for volatility considerations for all of its stock-based compensation types except for its TSR awards, which is based on a blend of the Company’s and comparable public entities’ historical volatility.

•

Risk-Free Interest Rate. Expressed as a weighted-average, the risk-free interest rate assumption is based on the U.S. Treasury instruments whose term was consistent with the expected term of the Company’s respective stock-based compensation types.

•

Expected Dividend Yield. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future.

Comprehensive Income (Loss)

The Company is required to report all components of comprehensive income (loss), including net income (loss), in the consolidated financial statements in the period in which they are recognized. Comprehensive income (loss) is defined as the change in equity during a period from transactions and other events and circumstances from non-owner sources, including unrealized gains and losses on investments and foreign currency translation adjustments. Comprehensive gains (losses) have been reflected in the consolidated statements of comprehensive income (loss) for all periods presented.

Recently Adopted Accounting Guidance

In December 2023, the FASB issued ASU 2023-09, Income Taxes (Topic 740): Improvements to Income Tax Disclosures, which requires enhanced income tax disclosures, including specific categories and disaggregation of information in the effective tax rate reconciliation, disaggregated information related to income taxes paid, income or loss from continuing operations before income tax expense or benefit, and income tax expense or benefit from continuing operations. This guidance is effective for annual periods beginning after December 15, 2024, with early adoption permitted. The Company adopted this guidance in 2025 using a prospective transition method. The adoption resulted in expanded disclosures and did not have a material impact on the Company's consolidated financial statements.

Recently Issued Accounting Guidance Not Yet Adopted

In November 2024, the FASB issued ASU No. 2024-03, Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40), which requires entities to disaggregate operating expenses into specific categories to provide enhanced transparency into the nature and function of expenses. This guidance is effective for fiscal years beginning after December 15, 2026, and for interim periods within fiscal years beginning after December 15, 2027, with early adoption permitted. This guidance should be applied either prospectively to financial statements issued for reporting periods after the effective date or retrospectively to any or all prior periods presented in the financial statements. The Company is currently in the process of evaluating the effects of this guidance on its related disclosures.

Collaboration Arrangements and Revenues

Astellas Agreements

Astellas Japan Agreement

In June 2005, the Company entered into a collaboration agreement with Astellas for the development and commercialization (but not manufacture) of roxadustat for the treatment of anemia in Japan (“Astellas Japan Agreement”). Under this agreement, Astellas agreed to pay license fees, other upfront consideration and various milestone payments, totaling $172.6 million. The Astellas Japan Agreement also provides for tiered payments based on net sales of product (as defined) in the low 20% range of the list price published by the Japanese Ministry of Health, Labour and Welfare, adjusted for certain elements, after commercial launch.

The aggregate amount of the considerations received under the Astellas Japan Agreement, through December 31, 2025 totals $105.1 million, excluding drug product revenue that is discussed under the Drug Product Revenue, Net section below. Based on its current development plans for roxadustat in Japan, the Company does not expect to receive most or all of the additional potential milestones under the Astellas Japan Agreement.

Amounts recognized as license revenue and development revenue under the Astellas Japan Agreement were not material for the years ended December 31, 2025 and 2024.

The transaction price related to consideration received through December 31, 2025 and accounts receivable has been allocated to each of the performance obligations under the Astellas Japan Agreement, including $100.3 million for license and $17.1 million for co-development.

There was no license revenue or development revenue resulting from changes to estimated variable consideration in the current period relating to performance obligations satisfied or partially satisfied in previous periods for the year ended December 31, 2025 under the Astellas Japan Agreement. The Company does not expect material variable consideration from estimated future co-development billing beyond the development period in the transaction price related to the Astellas Japan Agreement.

In 2018, the Company and Astellas entered into an amendment to the Astellas Japan Agreement that allows Astellas to manufacture roxadustat drug product for commercialization in Japan (the “Astellas Japan Amendment”). Under this amendment, the Company would continue to manufacture and supply roxadustat API to Astellas for the roxadustat commercial activities in Japan. The commercial terms of the Astellas Japan Agreement relating to the transfer price for roxadustat for commercial use remain substantially the same, reflecting an adjustment for the manufacture of drug product by Astellas rather than the Company. The related drug product revenue is described under the Drug Product Revenue, Net section below.

Astellas Europe Agreement

In April 2006, the Company entered into a separate collaboration agreement with Astellas for the development and commercialization of roxadustat for the treatment of anemia in Europe, the Middle East, the Commonwealth of Independent States and South Africa (“Astellas Europe Agreement”). Under the terms of the Astellas Europe Agreement, Astellas agreed to pay license fees, other upfront consideration and various milestone payments, totaling $745.0 million. Under the Astellas Europe Agreement, Astellas committed to fund 50% of joint development costs for Europe and North America, and all territory-specific costs. The Astellas Europe Agreement also provides for tiered payments based on net sales of product (as defined) in the low 20% range.

The aggregate amount of the considerations received under the Astellas Europe Agreement through December 31, 2025 totals $685.0 million, excluding drug product revenue that is discussed under the Drug Product Revenue, Net section below. Based on its current development plans for roxadustat in Europe, the Company does not expect to receive most or all of the additional potential milestones under the Astellas Europe Agreement.

Amounts recognized as license revenue and development revenue under the Astellas Europe Agreement were not material for the years ended December 31, 2025 and 2024.

The transaction price related to consideration received through December 31, 2025 and accounts receivable has been allocated to each of the performance obligations under the Astellas Europe Agreement, including $619.0 million for license and $288.7 million for co-development.

There was no license revenue or development revenue resulting from changes to estimated variable consideration in the current period relating to performance obligations satisfied or partially satisfied in previous periods for the year ended December 31, 2025 under the Astellas Europe Agreement. The Company does not expect material variable consideration from estimated future co-development billing beyond the development period in the transaction price related to the Astellas Europe Agreement.

During the first quarter of 2021, the Company entered into an EU Supply Agreement with Astellas (“Astellas EU Supply Agreement”) to define general forecast, order, supply and payment terms for Astellas to purchase roxadustat bulk drug product from the Company in support of commercial supplies. The related drug product revenue is described under the Drug Product Revenue, Net section below.

Accounting for the Astellas Agreements

For each of the Astellas agreements, the Company has evaluated the promised services within the respective arrangements and has identified performance obligations representing those services and bundles of services that are distinct.

Promised services that were not distinct have been combined with other promised services to form a distinct bundle of promised services, with revenue being recognized on the bundle of services rather than the individual services. There are no right-of-return provisions for the delivered items in the Astellas agreements.

As of December 31, 2025, the transaction price for the Astellas Japan Agreement, excluding manufacturing services that is discussed separately below, included $40.1 million of non-contingent upfront payments, $65.0 million of variable consideration related to payments for milestones achieved, and $12.4 million of variable consideration related to co-development billings. The transaction price for the Astellas Europe Agreement, excluding manufacturing services that is discussed separately below, included $320.0 million of non-contingent upfront payments, $365.0 million of variable consideration related to payments for milestones achieved, and $222.5 million of variable consideration related to co-development billings.

For the technology license under the Astellas Japan Agreement and the Astellas Europe Agreement, SSP was determined primarily by using the discounted cash flow (“DCF”) method, which aggregates the present value of future cash flows to determine the valuation as of the effective date of each of the agreements. The DCF method involves the following key steps: 1) the determination of cash flow forecasts and 2) the selection of a range of comparative risk-adjusted discount rates to apply against the cash flow forecasts. The discount rates selected were based on expectations of the total rate of return, the rate at which capital would be attracted to the Company and the level of risk inherent within the Company. The discounts applied in the DCF analysis ranged from 17.5% to 20.0%. The Company’s cash flow forecasts were derived from probability-adjusted revenue and expense projections by territory. Such projections included consideration of taxes and cash flow adjustments. The probability adjustments were made after considering the likelihood of technical success at various stages of clinical trials and regulatory approval phases. SSP also considered certain future royalty payments associated with commercial performance of the Company’s compounds, transfer prices and expected gross margins.

The promised services that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

(1)

License to the Company’s technology existing at the effective date of the agreements. For both of the Astellas agreements, the license was delivered at the beginning of the agreement term. In both cases, the Company concluded at the time of the agreement that its collaboration partner, Astellas, would have the knowledge and capabilities to fully exploit the licenses without the Company’s further involvement. However, the Astellas Japan Agreement has contractual limitations that might affect Astellas’ ability to fully exploit the license and therefore, potentially, the conclusion as to whether the license is capable of being distinct. The Company considered the fact that at the time of delivery of the license, the development services were beyond the preclinical development phase and any remaining development work in either agreement would not be expected to result in any significant modification or customization to the licensed technology. As such, the development services are separately identifiable from the licensed technology, indicating that the license is a distinct performance obligation. The portion of the transaction price allocated to this performance obligation based on a relative SSP basis was recognized as revenue in its entirety at the point in time the license transfers to Astellas.

(2)

Co-development services (Astellas Europe Agreement). This promise relates to co-development services that were reasonably expected to be performed by the Company at the time the collaboration agreement was signed and is considered distinct. Co-development billings are allocated entirely to the co-development services performance obligation as amounts are related specifically to research and development efforts necessary to satisfy the performance obligation related to CKD approval, and such an allocation is consistent with the allocation objective. Subsequent to the approval of CKD in 2021, the Company accounts for the development services for the indications related to chemotherapy-induced anemia and MDS separately as services are provided. There was no provision for co-development services in the Astellas Japan Agreement.

(3)

License to the Company’s technology developed during the term of the agreement and development (referred to as “when and if available”) and information sharing services. These promises are generally satisfied throughout the term of the agreements.

(4)

Manufacturing of clinical supplies of products. This promise is satisfied as supplies for clinical product are delivered for use in the Company’s clinical trial programs during the development period, or pre-commercialization period.

(5)

Committee service. This promise is satisfied throughout the course of the agreements as meetings are attended.

Items (2)-(5) are bundled into a single performance obligation that is distinct given the fact that all are highly interrelated during the development period (pre-commercial phase of development) such that satisfying them independently is not practicable. For the revenue recognized over time based on progress toward complete satisfaction of the performance obligation, the Company uses an input method to measure progress toward the satisfaction of the performance obligation, which is based on costs of labor hours or full time equivalents and out-of-pocket expenses incurred relative to total expected costs to be incurred, and updates the measure of progress in each reporting period.

(6)

Manufacturing commercial supplies of products. This promised service is distinct as services are not interrelated with any of the other performance obligations. Payments received for commercial supplies of products represent sales-based payments related predominately to the license of intellectual property under both Astellas agreements. Revenue is recognized as supplies are shipped for commercial use during the commercialization period. See the Drug Product Revenue, Net section below.

Under the Astellas Japan Amendment, the drug product revenue represents variable consideration and is estimated based on the quantity of product shipped, actual listed price for roxadustat issued by the Japanese Ministry of Health, Labour and Welfare and possible future changes to the listed price, adjusted for the timing of and estimated bulk product strength mix intended to be manufactured by Astellas, estimated cost to convert the API to bulk drug product tablets, and estimated yield from the manufacture of bulk product tablets, among others.

Under the Astellas Europe Agreement, the drug product revenue amount represents variable consideration and is estimated based on the quantity of product transferred and an estimated price. The estimated price is based on the contractual transfer price percentage applied on the estimated weighted average net sales price per strength, which is estimated to be realized by Astellas from the end sale of roxadustat in its approved territories.

AstraZeneca Agreements

AstraZeneca U.S./Rest of World Agreement

Effective July 30, 2013, the Company entered into a collaboration agreement with AstraZeneca for the development and commercialization of roxadustat for the treatment of anemia in the U.S. and all other countries in the world, other than China, not previously licensed under the Astellas Europe and Astellas Japan Agreements (“AstraZeneca U.S./RoW Agreement”).

The Company and AstraZeneca entered into an agreement to terminate the AstraZeneca U.S./RoW Agreement, effective as of February 25, 2024 (“AstraZeneca Termination and Transition Agreement”), as amended and restated on August 29, 2025. Pursuant to the AstraZeneca Termination and Transition Agreement, AstraZeneca returns all of their non-China roxadustat rights to the Company, with the exception of South Korea, and provides certain assistance during a transition period. In addition, as a part of this AstraZeneca Termination and Transition Agreement, AstraZeneca will receive tiered mid-single digit royalties on the Company’s sales of roxadustat in the terminated territories, or thirty-five percent of all revenue the Company receives if it licenses or sells such rights to a third-party. Neither party incurred any early termination penalties.

The aggregate amount of the considerations received under the AstraZeneca U.S./RoW Agreement through December 31, 2025 totals $439.0 million, excluding drug product revenue under the Master Supply Agreement with AstraZeneca under the AstraZeneca U.S./RoW Agreement (“AstraZeneca Master Supply Agreement”), entered in 2020, which is described under the Drug Product Revenue, Net section below. In addition, resulting from the AstraZeneca Termination and Transition Agreement, the Company and AstraZeneca settled the outstanding balances relating to past transactions under the AstraZeneca Master Supply Agreement. Accordingly, during the first quarter of 2024, the Company accounted for the termination of the AstraZeneca U.S./RoW Agreement as a contract modification under the Accounting Standards Codification (“ASC”) 606, Revenue from Contracts with Customers (“ASC 606”) and recorded a cumulative catch-up adjustment as described under the Drug Product Revenue, Net section below.

AstraZeneca China Agreement

AstraZeneca was the Company’s long-time commercialization partner for roxadustat in greater China. In July 2013, the Company (through its subsidiaries affiliated with China) entered into a collaboration agreement with AstraZeneca for roxadustat for the treatment of anemia in China (“AstraZeneca China Agreement”). Under the terms of the AstraZeneca China Agreement, AstraZeneca agreed to pay upfront consideration and potential milestone payments, totaling $376.7 million. The aggregate amount of such considerations received for milestone and upfront payments through the third quarter of 2025 totals $81.2 million. As discussed in Note 3, Discontinued Operations and Divestiture, on August 29, 2025, the Transaction was completed to sell the Company’s China operations to AstraZeneca pursuant to the Share Purchase Agreement.

AstraZeneca China Amendment

In July 2020, FibroGen China Anemia Holdings, Ltd., FibroGen Beijing, and FibroGen International (Hong Kong) Limited and AstraZeneca entered into an amendment, relating to the development and commercialization of roxadustat in China (the “AstraZeneca China Amendment”). Under the AstraZeneca China Amendment, in 2020, FibroGen Beijing and AstraZeneca completed the establishment of a jointly owned entity, Falikang, which performs roxadustat distribution, as well as conducts sales and marketing through AstraZeneca.

Substantially all direct roxadustat product sales to distributors in China are made by Falikang, while FibroGen Beijing continues to sell roxadustat product directly in limited areas in China. FibroGen Beijing manufactures and supplies commercial product to Falikang based on a gross transfer price, which is adjusted for the estimated profit share. Further discussion related to the sales to Falikang is discussed under the China Performance Obligation section below.

Prior to the above-mentioned termination of the AstraZeneca U.S./RoW Agreement, the Company evaluated under the ASC 606 and accounted for the AstraZeneca U.S./RoW Agreement and the AstraZeneca China Agreement as a single arrangement with the presumption that two or more agreements executed with a single customer at or around the same time should be presumed to be a single arrangement. As a result of the termination of the AstraZeneca U.S./RoW Agreement, during the first quarter of 2024, the Company recorded the final development revenue under the AstraZeneca U.S./RoW Agreement and AstraZeneca China Agreement, which was immaterial.

The related net product revenue recognized from the sales to Falikang is discussed under the China Performance Obligation section below. The related net product revenue recognized from the sales to Falikang was $218.6 million and $159.0 million for the years ended December 31, 2025 and 2024, respectively, and were included in the discontinued operations in the consolidated statements of operations together with the sales directly to distributors, resulting from the Share Purchase Agreement with AstraZeneca Treasury Limited as discussed in Note 3, Discontinued Operations and Divestiture.

Accounting for the AstraZeneca Agreements

The Company evaluated whether the AstraZeneca U.S./RoW Agreement and the AstraZeneca China Agreement should be accounted for as a single or separate arrangements and concluded that the agreements should be accounted for as a single arrangement with the presumption that two or more agreements executed with a single customer at or around the same time should be presumed to be a single arrangement, and therefore upfront and other non-contingent consideration received and to be received has been pooled together and allocated to each of the performance obligations in both the AstraZeneca U.S./RoW Agreement and the AstraZeneca China Agreement based on their relative SSPs.

For each of the AstraZeneca agreements, the Company has evaluated the promised services within the respective arrangements and has identified performance obligations representing those services and bundled services that are distinct.Promised services that were not distinct have been combined with other promised services to form a distinct bundle of promised services, with revenue being recognized on the bundle of services rather than the individual promised services. There are no right-of-return provisions for the delivered items in the AstraZeneca agreements.

The transaction price related to consideration received and accounts receivable through the termination of the AstraZeneca U.S./RoW Agreement has been allocated to each of the performance obligations under the AstraZeneca U.S./RoW Agreement and AstraZeneca China Agreement, including $344.5 million for license, $625.5 million for co-development, information sharing and committee services, and $573.4 million for China Performance Obligation (cumulative revenue through the third quarter of 2025) that is recognized as product revenue, net, included in discontinued operations as described under China Performance Obligation section below.

For the AstraZeneca agreements, the Company allocated the transaction price to the various performance obligations based on the relative SSP of each performance obligation, with the exception of co-development billings and commercial sale of product. Co-development billings under the AstraZeneca U.S./RoW Agreement were allocated entirely to the U.S./RoW co-development services performance obligation, and co-development billings under the AstraZeneca China Agreement were allocated entirely to the combined performance obligation under the AstraZeneca China Agreement. Commercial sale of product under the AstraZeneca U.S./RoW Agreement is entirely allocated to the manufacturing commercial supply of products performance obligation, and commercial sale of product under the AstraZeneca China Agreement is allocated entirely to the combined China Performance Obligation.

In accordance with the AstraZeneca China Amendment, substantially all product sales will be made by Falikang directly to the distributors in China, while the Company continues to sell directly in one province in China. Revenue is recognized at a point in time when control of roxadustat commercial product is transferred to Falikang. See the China Performance Obligation section below. The related net product revenue is included in the discontinued operations in the consolidated statements of operations, resulting from the Share Purchase Agreement with AstraZeneca Treasury Limited as discussed in Note 3, Discontinued Operations and Divestiture.

Product Revenue, Net

Product revenue, net, which is included in the discontinued operations, consists primarily of revenues from sales of roxadustat commercial product to Falikang. Substantially all direct roxadustat product sales to distributors in China are made by Falikang. FibroGen Beijing manufactures and supplies commercial product to Falikang. The net transaction price for FibroGen Beijing’s product sales to Falikang is based on a gross transaction price, adjusted for the estimated profit share.

The roxadustat sales to Falikang marked the beginning of the Company’s China Performance Obligation under the Company’s agreements with AstraZeneca. Product revenue is based on the transaction price of the China Performance Obligation. Revenue is recognized when control of the product is transferred to Falikang, in an amount that reflects the allocation of the transaction price to the performance obligation satisfied during the reporting period. Periodically, the Company updates its assumptions such as total sales quantity, performance period, gross transaction price, profit share and other inputs including foreign currency translation impact, among others. Any net transaction price in excess of the revenue recognized is added to the deferred balance, and recognized in future periods as the performance obligation is satisfied.

As discussed in Note 3, Discontinued Operations and Divestiture, the divestiture of FibroGen International was completed on August 29, 2025 and accordingly, the performance obligation to AstraZeneca was completely satisfied upon the closing of the divestiture. As a result, all the previously deferred revenues were recognized as revenue during the third quarter of 2025. The following table includes a roll-forward of the related deferred revenue that was considered as a contract liability that was not included in the disposal group held for sale as of December 31, 2024 (in thousands):


	Balance at December 31, 2024			Additions			Recognized as Revenue (Discontinued Operations)		Currency Translation and Other			Balance at December 31, 2025
AstraZeneca China performance obligation - deferred revenue	$	(132,097	)	$	(82,494	)	$	218,575	$	(3,984	)	$	—

The related net product revenue recognized from the sales to Falikang was $218.6 million and $159.0 million for year ended December 31, 2025 and 2024, respectively, which were included in the discontinued operations in the consolidated statements of operations together with the sales directly to distributors.

Drug Product Revenue, Net

Drug product revenue from commercial-grade API or bulk drug product sales to Astellas and AstraZeneca was as follows for the years ended December 31, 2025 and 2024 (in thousands):


	Years Ended December 31,
	2025		2024
Astellas Japan Agreement	$	793	$	(2,872	)
Astellas Europe Agreement		5,055		4,874
AstraZeneca U.S./RoW Agreement		—		25,671
Drug product revenue, net	$	5,848	$	27,673

Astellas Japan Agreement

For the year ended December 31, 2025, the Company updated its estimate of variable consideration related to the API shipments fulfilled under the terms of Astellas Japan Amendment, and accordingly recorded an adjustment to the drug product revenue of $0.8 million. Specifically, the change in estimated variable consideration was based on the API held by Astellas at period end, adjusted to reflect the changes in the estimated bulk product strength mix intended to be manufactured by Astellas and foreign exchange impacts, among others.

For the year ended December 31, 2024, the Company updated its estimate of variable consideration related to the API shipments fulfilled under the terms of Astellas Japan Amendment, and accordingly recorded a reduction to the drug product revenue of $2.9 million. Specifically, the change in estimated variable consideration was based on the API held by Astellas at period end, adjusted to reflect the changes in the estimated bulk product strength mix intended to be manufactured by Astellas and foreign exchange impacts, among others.

As of December 31, 2025, the balances related to the API price true-up under the Astellas Japan Agreement were $1.6 million in accrued liabilities, representing the Company’s best estimate of the timing for these amounts to be paid. As of December 31, 2024, the balances related to the API price true-up under the Astellas Japan Agreement were $2.5 million in accrued liabilities and $0.6 million in other long-term liabilities.

Astellas Europe Agreement

During the fourth quarter of 2025, the Company transferred bulk drug product for commercial purposes under the terms of the Astellas Europe Agreement and the Astellas EU Supply Agreement, and recognized the related fully-burdened manufacturing costs of $0.3 million as drug product revenue, and recorded $2.2 million as deferred revenue due to a high degree of uncertainty associated with the variable consideration for revenue recognition purposes. In addition, the Company updated its estimate of variable consideration related to the bulk drug product transferred in prior years. Specifically, the change in estimated variable consideration was based on the bulk drug product held by Astellas at the period end, adjusted to reflect the changes in the estimated transfer price, forecast information, shelf-life estimates and other items. As a result, for the year ended December 31, 2025, the Company reclassified $1.8 million from the related deferred revenue to accrued liabilities. As of December 31, 2025, the related balance in accrued liabilities was $5.4 million, representing the Company’s best estimate that this amount will be paid within the next 12 months.

During the fourth quarter of 2024, the Company transferred bulk drug product for commercial purposes under the terms of the Astellas Europe Agreement and the Astellas EU Supply Agreement, and recognized the related fully-burdened manufacturing costs of $0.6 million as drug product revenue, and recorded $4.4 million as deferred revenue due to a high degree of uncertainty associated with the variable consideration for revenue recognition purposes. In addition, the Company updated its estimate of variable consideration related to the bulk drug product transferred in prior years. Specifically, the change in estimated variable consideration was based on the bulk drug product held by Astellas at the period end, adjusted to reflect the changes in the estimated transfer price, forecast information, shelf-life estimates and other items. As a result, for the year ended December 31, 2024, the Company reclassified $7.2 million from the related deferred revenue to accrued liabilities. As of December 31, 2024, the related balance in accrued liabilities was $10.5 million, and the Company paid $7.1 million to Astellas during the year ended December 31, 2025.

The Company recognized royalty revenue of $4.8 million and $4.3 million as drug product revenue from the deferred revenue under the Astellas Europe Agreement during the years ended December 31, 2025 and 2024, respectively. The remainder of the deferred revenue will be recognized as and when uncertainty is resolved, based on the performance of roxadustat product sales in the Astellas territory.

The following table includes a roll-forward of the above-mentioned deferred revenues that are considered as contract liabilities related to drug product (in thousands):


	Balance at December 31, 2024			Additions			Recognized as Revenue		Reclassified to Accrued Liability / Accounts Payable		Balance at December 31, 2025
Drug product revenue - deferred revenue:
Astellas Europe Agreement	$	(9,901	)	$	(2,210	)	$	4,778	$	1,764	$	(5,569	)

AstraZeneca U.S./RoW Agreement

As described under AstraZeneca Agreements section above, pursuant to the AstraZeneca Termination and Transition Agreement related to the AstraZeneca U.S./RoW Agreement, the Company and AstraZeneca settled the outstanding balances relating to past transactions under the AstraZeneca Master Supply Agreement. Accordingly, during the year ended December 31, 2024, the Company accounted for the termination of the AstraZeneca U.S./RoW Agreement as a contract modification under the ASC 606 and recorded a cumulative catch-up net adjustment of $25.7 million to the drug product revenue and correspondingly recorded the related cost of goods sold of $14.6 million.

Fair Value Measurements

Level 1: Quoted prices in active markets for identical assets or liabilities.

Level 2: Observable inputs other than quoted prices in active markets for identical assets or liabilities.

Level 3: Unobservable inputs.

Collaboration Agreements, License Agreement and Revenues - Drug Product Revenue - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2025	Dec. 31, 2024
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			$ 6,440	$ 29,621
Deferred Revenue	$ 5,314	$ 27,290	5,314	27,290
Related cost of goods sold			556	15,561
Other long-term liabilities	82	822	82	822
AstraZeneca U.S./RoW Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Related cost of goods sold				14,600
Cumulative catch-up net adjustment				25,700
Astra Zeneca Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			218,600	159,000
Drug Product Revenue, Net [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			5,848	27,673
Drug Product Revenue, Net [Member] \| API Shipment [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			800	2,900
Drug Product Revenue, Net [Member] \| Astellas Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			5,800	2,000
Drug Product Revenue, Net [Member] \| Astellas Europe Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Deferred Revenue	2,200	4,400	2,200	4,400
Drug Product Revenue, Net [Member] \| Japan [Member] \| Astellas Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			793	(2,872)
Accrued liabilities	1,600	2,500	1,600	2,500
Other long-term liabilities		600		600
Drug Product Revenue, Net [Member] \| Europe [Member] \| Astellas Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			5,055	4,874
Drug Product Revenue, Net [Member] \| Europe [Member] \| Astellas Europe Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Burdened manufacturing costs	300	600
Bulk Drug Product [Member] \| Europe [Member] \| Astellas Europe Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized			1,800	7,200
Accrued liabilities	5,400	$ 10,500	5,400	10,500
Accrued liabilities paid	$ 7,100		7,100
Bulk Drug Product [Member] \| Europe [Member] \| Astellas Europe Agreement [Member] \| Royalty Revenue [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Royalty revenue recognized as drug product revenue			$ 4,800	$ 4,300

Related Party Transactions - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Related Party Transaction [Line Items]
Revenues	$ 6,440	$ 29,621
Accounts receivable from related parties	$ 216	481
Falikang
Related Party Transaction [Line Items]
Accounts receivable from related parties		13,900
Percentage of outstanding shares owned	51.10%
Investment income	$ 2,500	4,000
Equity method investment in unconsolidated variable interest entity		6,900
Falikang \| Collaborative Arrangement [Member]
Related Party Transaction [Line Items]
Revenues	$ 218,600	$ 159,000

- Definition

This item represents the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized.

+ References + Details

- Definition

Amount of income (loss) for proportionate share of equity method investee's income (loss).

+ References + Details

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (d)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 850
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483326/850-10-50-3

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(k)(1))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 310
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481990/310-10-45-13

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(i))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(c)(2)(ii))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 220
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.6-07(2)(g)(3))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479134/946-220-S99-1

Liability Related to Sale of Future Revenues - Schedule of Activity of Liability Related to Sale of Future Revenues (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Liability Related to Sale of Future Royalties [Abstract]
Liability related to sale of future revenues - beginning balance	$ 59,324	$ 57,067
Interest paid	(450)	(5,653)
Interest expense recognized	8,440	7,910
Liability related to sale of future revenues - ending balance	67,314	59,324
Less: Current portion classified to accrued and other current liabilities	(1,334)	(460)
Liability related to sale of future revenues, non-current	$ 65,980	$ 58,864

Segment and Geographic Information - Schedule of Customer Concentration by Collaboration Partners (Detail) - Customer Concentration Risk [Member] - Percentage of Revenue [Member]	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
AstraZeneca [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	0.00%	88.00%
Astellas [Member]
Entity Wide Revenue Major Customer [Line Items]
Concentration risk, percentage	100.00%	12.00%

- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References + Details

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Dec. 31, 2025
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	Trading Arrangements None.
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Balance Sheet Components (Tables)

12 Months Ended

Dec. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Cash and Cash Equivalents

Cash and cash equivalents consisted of the following (in thousands):


	December 31, 2025		December 31, 2024
Cash	$	2,309	$	2,004
Commercial paper		11,272		14,269
Money market funds		24,302		28,241
U.S. government bonds		9,989		5,968
Total cash and cash equivalents	$	47,872	$	50,482

Summary of Amortized Cost, Gross Unrealized Holding Gains or Losses, and Fair Value of Investments

The Company’s investments consist primarily of available-for-sale debt investments and the amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s investments by major investments type are summarized in the tables below (in thousands):


	December 31, 2025
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Estimated Fair Value
Corporate bonds	$	27,800	$	17	$	—	$	27,817
Commercial paper		6,525		—		—		6,525
U.S. government bonds		26,903		21		—		26,924
Total investments	$	61,228	$	38	$	—	$	61,266

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):


	December 31, 2025		December 31, 2024
Insurance proceeds receivable for litigation settlement	$	—	$	28,500
Holdback consideration receivable related to divestiture		4,000		—
Prepaid assets		1,015		1,903
Other current assets		1,121		1,139
Total prepaid expenses and other current assets	$	6,136	$	31,542

Schedule of Accrued and Other Current Liabilities

Accrued and other current liabilities consisted of the following (in thousands):


	December 31, 2025		December 31, 2024
Preclinical and clinical trial accruals	$	3,066	$	6,327
API and bulk drug product price true-up		6,977		13,071
Litigation settlement		—		28,500
Payroll and related accruals		3,983		4,640
Accrued restructuring charge		537		4,572
Professional services		2,465		2,049
Current portion of liability related to sale of future revenues		1,334		460
Other		1,821		2,416
Total accrued and other current liabilities	$	20,183	$	62,035

Collaboration Agreements, License Agreement and Revenues - Drug Product Revenue - Summary of Drug Product Revenue (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized	$ 6,440	$ 29,621
AstraZeneca Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized	218,600	159,000
Drug Product Revenue, Net [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized	5,848	27,673
Drug Product Revenue, Net [Member] \| Astellas Agreement [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized	5,800	2,000
Drug Product Revenue, Net [Member] \| Astellas Agreement [Member] \| Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized	793	(2,872)
Drug Product Revenue, Net [Member] \| Astellas Agreement [Member] \| Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized	5,055	4,874
Drug Product Revenue, Net [Member] \| AstraZeneca Agreements [Member] \| U.S. [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Drug product revenue recognized	$ 0	$ 25,671

- Definition

+ References

+ Details

Leases - Schedule of Supplemental Cash Flow Information Related to Leases (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Cash paid for amounts included in the measurement of lease liabilities:
Financing cash flows from finance leases	$ 10	$ 40

Balance Sheet Components

12 Months Ended

Dec. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Balance Sheet Components

7. Balance Sheet Components

Cash and Cash Equivalents

Cash and cash equivalents consisted of the following (in thousands):


	December 31, 2025		December 31, 2024
Cash	$	2,309	$	2,004
Commercial paper		11,272		14,269
Money market funds		24,302		28,241
U.S. government bonds		9,989		5,968
Total cash and cash equivalents	$	47,872	$	50,482

Investments

As of December 31, 2025, The Company’s investments consist primarily of available-for-sale debt investments and the amortized cost, gross unrealized holding gains or losses, and fair value of the Company’s investments by major investments type are summarized in the tables below (in thousands):


	December 31, 2025
	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Estimated Fair Value
Corporate bonds	$	27,800	$	17	$	—	$	27,817
Commercial paper		6,525		—		—		6,525
U.S. government bonds		26,903		21		—		26,924
Total investments	$	61,228	$	38	$	—	$	61,266

As of December 31, 2025, the available-for-sale investments had remaining contractual maturities within two years.

The Company periodically assesses whether the unrealized losses on its available-for-sale investments were temporary. The Company considers factors such as the severity and the reason for the decline in value, the potential recovery period and its intent to sell. For debt securities, the Company also considers whether (i) it is more likely than not that the Company will be required to sell the debt securities before recovery of their amortized cost basis, and (ii) the amortized cost basis cannot be recovered as a result of credit losses. Based on the results of its review, the Company did not recognize any other-than-temporary impairment loss during the two years ended December 31, 2025.

The Company did not have any short-term or long-term investments as of December 31, 2024.

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following (in thousands):


	December 31, 2025		December 31, 2024
Insurance proceeds receivable for litigation settlement	$	—	$	28,500
Holdback consideration receivable related to divestiture		4,000		—
Prepaid assets		1,015		1,903
Other current assets		1,121		1,139
Total prepaid expenses and other current assets	$	6,136	$	31,542

As of December 31, 2025, the Company recorded a $4.0 million receivable in prepaid expenses and other current assets for the second holdback related to the closing of the divestiture of FibroGen International. See Note 3, Discontinued Operations and Divestiture, for details.

As of December 31, 2024, the Company recorded a $28.5 million receivable in prepaid expenses and other current assets, corresponding to the accrued litigation settlement of the same amount related to the Company’s agreement in principle with plaintiffs to settle the class action lawsuit. As the Company maintains insurance that covers exposure related to the class action lawsuit, this amount is fully recoverable under the Company’s insurance policies. The determination that the recorded receivables are probable of collection is based on the terms of the applicable insurance policies and communications with the insurers. Such amount was fully distributed during the first quarter of 2025. As a result, the related accrued liability and the corresponding receivable were fully settled in the same period. See the Accrued and Other Current Liabilities section below, and the Legal Proceedings and Other Matters section in Note 11, Commitments and Contingencies, for details.

Accrued and Other Current Liabilities

Accrued and other current liabilities consisted of the following (in thousands):


	December 31, 2025		December 31, 2024
Preclinical and clinical trial accruals	$	3,066	$	6,327
API and bulk drug product price true-up		6,977		13,071
Litigation settlement		—		28,500
Payroll and related accruals		3,983		4,640
Accrued restructuring charge		537		4,572
Professional services		2,465		2,049
Current portion of liability related to sale of future revenues		1,334		460
Other		1,821		2,416
Total accrued and other current liabilities	$	20,183	$	62,035

The accrued liabilities of $7.0 million and $13.1 million for API and bulk drug product price true-up as of December 31, 2025 and 2024, respectively, resulted from changes in estimated variable consideration associated with the API shipments fulfilled under the terms of the Astellas Japan Amendment, the bulk drug product transferred under the terms of the Astellas Europe Agreement and the Astellas EU Supply Agreement. During the fourth quarter of 2025, the Company paid $7.1 million to Astellas related to accrued amounts. See the Drug Product Revenue, Net section in Note 4, Collaboration Agreements, License Agreement and Revenues, for details.

As of December 31, 2024, the accrued litigation settlement of $28.5 million was related to the Company’s agreement in principle with plaintiffs to settle the class action lawsuit, which was fully distributed during the first quarter of 2025 as mentioned above. See the Prepaid Expenses and Other Current Assets section above, and the Legal Proceedings and Other Matters section in Note 11, Commitments and Contingencies, for details.

Responding to the reported results for pamrevlumab in July 2024, the Company implemented an immediate and significant cost reduction plan in the U.S., including terminating pamrevlumab research and development investment and expeditiously wind down remaining obligations, and reducing U.S. workforce by approximately 75%. As a result, the Company recorded a total of $19.5 million non-recurring restructuring charge during the year ended December 31, 2024, primarily consisting of notice period and severance payments, accrued vacation, and employee benefits contributions. Total cash payments under the reduction in force were $3.5 million and $16.5 million for the years ended December 31, 2025 and 2024, respectively. The remaining accrued restructuring charge of $0.5 million as of December 31, 2025 will be paid out in 2026.

Equity and Stock based compensation - Schedule of Assumptions used to Estimate Fair Value of TSR Awards (Details) - $ / shares	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Weighted average estimated fair value	$ 15.14	$ 43.43
TSR [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (in years)	3 years 10 months 24 days	3 years 10 months 24 days
Expected volatility, minimum	69.00%	69.00%
Expected volatility, maximum	73.30%	73.30%
Risk-free interest rate, minimum	1.80%	1.80%
Risk-free interest rate, maximum	4.20%	4.20%
Expected dividend yield	0.00%	0.00%
Weighted average estimated fair value	$ 759.23	$ 737.88

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(v)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (f)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
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+ Details

Net Loss Per Share - Schedule of Weighted Impacts of Outstanding Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	498	681
Employee Stock Option
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	465	538
RSUs, PRSUs and TSR awards [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	33	125
ESPP [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from computation of net loss per share	0	18

Equity and Stock-based Compensation - Summary of Common Stock Reserved for Future Issuance (Detail) - shares shares in Thousands	Dec. 31, 2025	Dec. 31, 2024
Class Of Stock [Line Items]
Common stock outstanding	4,047	4,037
Stock options outstanding	373	389
RSUs outstanding	16	53
Shares reserved for future stock options and RSUs grant	818	776
Total shares of common stock reserved	5,519	5,520
ESPP [Member]
Class Of Stock [Line Items]
Shares reserved for future ESPP offering	265	265

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Collaboration Agreements, License Agreement and Revenues

12 Months Ended

Dec. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Collaboration Agreements, License Agreement and Revenues

4. Collaboration Agreements, License Agreement and Revenues

Astellas Agreements

Astellas Japan Agreement

Amounts recognized as license revenue and development revenue under the Astellas Japan Agreement were not material for the years ended December 31, 2025 and 2024.

Astellas Europe Agreement

Amounts recognized as license revenue and development revenue under the Astellas Europe Agreement were not material for the years ended December 31, 2025 and 2024.

The transaction price related to consideration received through December 31, 2025 and accounts receivable has been allocated to each of the performance obligations under the Astellas Europe Agreement, including $619.0 million for license and $288.7 million for co-development.

There was no license revenue or development revenue resulting from changes to estimated variable consideration in the current period relating to performance obligations satisfied or partially satisfied in previous periods for the year ended December 31, 2025 under the Astellas Europe Agreement. The Company does not expect material variable consideration from estimated future co-development billing beyond the development period in the transaction price related to the Astellas Europe Agreement.

Accounting for the Astellas Agreements

The promised services that were analyzed, along with their general timing of satisfaction and recognition as revenue, are as follows:

(1)

(2)

(3)

(4)

(5)

Committee service. This promise is satisfied throughout the course of the agreements as meetings are attended.

(6)

AstraZeneca Agreements

AstraZeneca U.S./Rest of World Agreement

AstraZeneca China Agreement

AstraZeneca China Amendment

Accounting for the AstraZeneca Agreements

China Performance Obligation


	Balance at December 31, 2024			Additions			Recognized as Revenue (Discontinued Operations)		Currency Translation and Other			Balance at December 31, 2025
AstraZeneca China performance obligation - deferred revenue	$	(132,097	)	$	(82,494	)	$	218,575	$	(3,984	)	$	—

Drug Product Revenue, Net

Drug product revenue from commercial-grade API or bulk drug product sales to Astellas and AstraZeneca was as follows for the years ended December 31, 2025 and 2024 (in thousands):


	Years Ended December 31,
	2025		2024
Astellas Japan Agreement	$	793	$	(2,872	)
Astellas Europe Agreement		5,055		4,874
AstraZeneca U.S./RoW Agreement		—		25,671
Drug product revenue, net	$	5,848	$	27,673

Astellas Japan Agreement

Astellas Europe Agreement

The following table includes a roll-forward of the above-mentioned deferred revenues that are considered as contract liabilities related to drug product (in thousands):


	Balance at December 31, 2024			Additions			Recognized as Revenue		Reclassified to Accrued Liability / Accounts Payable		Balance at December 31, 2025
Drug product revenue - deferred revenue:
Astellas Europe Agreement	$	(9,901	)	$	(2,210	)	$	4,778	$	1,764	$	(5,569	)

AstraZeneca U.S./RoW Agreement

Collaboration Agreements, License Agreement and Revenues - AstraZeneca Agreements - Additional Information 1 (Detail) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
	Jul. 30, 2013	Sep. 30, 2025	Dec. 31, 2025	Dec. 31, 2024
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			$ 6,440	$ 29,621
Drug Product Revenue, Net [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			5,848	27,673
AstraZeneca Agreements [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			218,600	$ 159,000
AstraZeneca Agreements [Member] \| U.S./RoW [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Aggregate considerations received			$ 439,000
AstraZeneca Agreements [Member] \| China [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent, non-refundable and time-based payments	$ 376,700
Aggregate considerations received		$ 81,200

- Definition

+ References

+ Details

Segment and Geographic Information (Tables)

12 Months Ended

Dec. 31, 2025

Segment Reporting [Abstract]

Schedule of Revenue by Geographic Area

Geographic revenues, which are based on the region that revenue is generated, are as follows (in thousands):


	Years Ended December 31,
	2025		2024
United States	$	—	$	26,114
Europe		5,643		6,270
Japan		797		(2,854	)
China		—		91
Total revenue	$	6,440	$	29,621

Schedule of Customer Concentration by Collaboration Partners

The Company’s revenues have been generated from the following collaboration partners that individually accounted for 10% or more of the Company’s total revenue:


	Percentage of Revenue
	Years Ended December 31,
	2025			2024
AstraZeneca		—	%		88	%
Astellas		100	%		12	%

Discontinued Operations and Divestiture - Additional Information (Detail) - USD ($) $ in Thousands			12 Months Ended
	Nov. 06, 2025	Aug. 29, 2025	Dec. 31, 2025	Dec. 31, 2024
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on divestiture			$ 52,553	$ (0)
Revenues			6,440	29,621
Accounts receivable from related parties			216	481
Share Purchase Agreement [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation cash paid at closing		$ 210,400
Discontinued operation other receivable			$ 10,000
Disposal group including discontinued operation additional payment related to first holdback		400
Discontinued operation consideration		220,400
Falikang [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of outstanding shares owned			51.10%
Investment income			$ 2,500	4,000
Equity method investments				6,900
Accounts receivable from related parties				13,900
Falikang [Member] \| Collaborative Arrangement [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Revenues			$ 218,600	159,000
Astra Zeneca [Member] \| Share Purchase Agreement [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation cash payable at closing subject to holdbacks		10,000
Discontinued operation hold back amount to offset final net cash adjustments	$ 6,400	6,000
Discontinued operation, hold back amount to satisfy any indemnity claims		4,000
Disposal group including discontinued operation additional payment following final net cash adjustments after closing	$ 400
FibroGen International [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Description of discontinued operations			On February 20, 2025, the Company entered into the Share Purchase Agreement with AstraZeneca Treasury Limited, pursuant to which the Company and its subsidiary FibroGen China Anemia Holdings, Ltd. agreed to sell all of the issued and outstanding equity interests of FibroGen International to AstraZeneca Treasury Limited. This sale includes all of the Company’s roxadustat assets in China, including FibroGen International’s subsidiary FibroGen Beijing and its 51.1% interest in Falikang. The Company determined that FibroGen International met the “held for sale” criteria and the “discontinued operations” criteria in accordance with FASB ASC 205, Presentation of Financial Statements, as of December 31, 2024. Accordingly, the operating results related to the FibroGen International are classified as discontinued operations, and have been reflected as discontinued operations in the consolidated statements of operations, while the related assets and liabilities were classified within the consolidated balance sheets as held for sale for all periods presented.
Discontinued operations name			FibroGen International
Gain on divestiture		52,600	$ 52,553	$ 0
FibroGen International [Member] \| Share Purchase Agreement [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation consideration in cash		85,000
Discontinued operation consideration transaction costs and fees		7,800
Discontinued operation derecognition of net equity		154,900
Discontinued operatiion cumulative currency translation adjustments		5,500
Discontinued operation consideration		220,400
Net Cash Held in China [Member] \| Share Purchase Agreement [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Discontinued operation consideration in cash		$ 135,400

Discontinued Operations and Divestiture - Schedule of Carrying Value of Assets and Liabilities of Discontinued Operations (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Assets
Cash and cash equivalents	$ 0	$ 51,696
Total current assets held for sale	0	110,849
Total long-term assets held for sale	0	16,611
Liabilities
Total current liabilities held for sale	0	38,917
Total long-term liabilities held for sale	$ 0	356
FibroGen International [Member]
Assets
Cash and cash equivalents		51,696
Accounts receivable, net		18,443
Inventories		15,547
Prepaid expenses and other current assets		25,163
Total current assets held for sale		110,849
Property and equipment, net		7,041
Equity method investment in unconsolidated variable interest entity		6,864
Operating lease right-of-use assets		1,716
Other assets		990
Total long-term assets held for sale		16,611
Liabilities
Accounts payable		26,974
Accrued and other current liabilities		10,679
Operating lease liabilities, current		1,264
Total current liabilities held for sale		38,917
Operating lease liabilities, non-current		356
Total long-term liabilities held for sale		$ 356

Discontinued Operations and Divestiture (Tables)

12 Months Ended

Dec. 31, 2025

Discontinued Operations and Disposal Groups [Abstract]

Schedule of Financial Results, Carrying Value of Assets and Liabilities and Significant Non-Cash Items and Capital Expenditures of Discontinued Operations

The financial results of the discontinued operations with respect to FibroGen International reflected in the consolidated statements of operations for the years ended December 31, 2025 and 2024 were as follows (in thousands):


	Years Ended December 31,
	2025			2024
Revenue:
Product revenue, net	$	226,651		$	173,664
Operating costs and expenses:
Cost of goods sold		13,454			21,036
Research and development		1,739			7,375
Selling, general and administrative		14,849			32,304
Total operating costs and expenses		30,042			60,715
Income from operations		196,609			112,949
Interest and other, net
Interest expense		(7,816	)		(11,683	)
Gain on divestiture		52,553			—
Interest income and other income (expenses), net		(2,173	)		423
Total interest and other, net		42,564			(11,260	)
Income before income taxes		239,173			101,689
Provision for income taxes		—			139
Investment income in unconsolidated variable interest entity		2,483			3,969
Income from discontinued operations, net of tax	$	241,656		$	105,519

The carrying value of the assets and liabilities of the discontinued operations with respect to FibroGen International on the consolidated balance sheets as of December 31, 2024 were as follows (in thousands):


	December 31, 2024
Assets
Cash and cash equivalents	$	51,696
Accounts receivable, net		18,443
Inventories		15,547
Prepaid expenses and other current assets		25,163
Total current assets held for sale		110,849

Property and equipment, net		7,041
Equity method investment in unconsolidated variable interest entity		6,864
Operating lease right-of-use assets		1,716
Other assets		990
Total long-term assets held for sale		16,611

Liabilities
Accounts payable	$	26,974
Accrued and other current liabilities		10,679
Operating lease liabilities, current		1,264
Total current liabilities held for sale		38,917

Operating lease liabilities, non-current		356
Total long-term liabilities held for sale		356

The significant non-cash items and capital expenditures for the discontinued operations with respect to FibroGen International included in the consolidated statements of cash flows for the years ended December 31, 2025 and 2024 were as follows (in thousands):


	Years Ended December 31,
	2025			2024
Depreciation	$	713		$	1,458
Investment income in unconsolidated variable interest entity		(2,486	)		(3,969	)
Gain on divestiture		(52,553	)		—
Impairment of property and equipment		2,062			—
Dividend received from unconsolidated variable interest entity		3,947			2,230
Stock-based compensation	$	231		$	1,770

- Definition

Tabular disclosure of information related to a disposal group. Includes, but is not limited to, a discontinued operation, disposal classified as held-for-sale or disposed of by means other than sale or disposal of an individually significant component.

+ References

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-Name Accounting Standards Codification
-Section 50
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-Section 50
-Paragraph 1
-SubTopic 20
-Topic 205
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-1

Reference 15: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147483499/205-20-50-3

+ Details

Equity and Stock-based Compensation - Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average estimated fair value	$ 15.14	$ 43.43
Employee stock options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years 4 months 24 days	6 years 1 month 6 days
Expected volatility	123.80%	113.70%
Risk-free interest rate	4.30%	4.20%
Expected dividend yield	0.00%	0.00%
Weighted average estimated fair value	$ 13.23	$ 1.49
Employee stock purchase plans [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	0.00%	61.50%
Expected volatility, maximum		271.20%
Risk-free interest rate, minimum	0.00%	2.60%
Risk-free interest rate, maximum		5.30%
Expected dividend yield	0.00%	0.00%
Weighted average estimated fair value	$ 0	$ 1.67
Employee stock purchase plans [Member] \| Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		6 months
Employee stock purchase plans [Member] \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)		2 years

Equity and Stock-based Compensation

12 Months Ended

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Equity and Stock-based Compensation

12. Equity and Stock-based Compensation

Common Stock

On June 16, 2025, the Company effected the Reverse Stock Split. Proportionate adjustments have been made to the number of shares available for issuance under the Company’s equity incentive plans as well as outstanding equity awards, in accordance with their respective terms. Each share of Common Stock is entitled to one vote. The holders of Common Stock are also entitled to receive dividends whenever funds are legally available and when declared by the board of directors, subject to the prior rights of holders of all classes of stock outstanding.

Shares of Common Stock outstanding, shares of stock plans outstanding and shares reserved for future issuance related to stock options and RSU grants and the Company’s Employee Stock Purchase Plan (“ESPP”) purchases are as follows (in thousands):


	December 31,
	2025		2024
Common stock outstanding		4,047		4,037
Stock options outstanding		373		389
RSUs outstanding		16		53
Shares reserved for future stock options and RSUs grant		818		776
Shares reserved for future ESPP offering		265		265
Total shares of common stock reserved		5,519		5,520

At-the-Market Program

On February 24, 2025, the Company entered into an Equity Distribution Agreement with BofA Securities, Inc. (“BofA”), under which it may offer and sell its common stock having aggregate sales proceeds of up to $30.0 million from time to time through BofA as its sales agent. The Company did not sell any shares of common stock under this ATM program during the years ended December 31, 2025.

Stock Plans

Stock Option and RSU Plans

In September 2014, the Company adopted a 2014 Equity Incentive Plan (the “2014 Plan”) which became effective in November 2014. The 2014 Plan is the successor equity compensation plan to the 2005 Plan. The 2014 Plan provided for the grant of incentive stock options, nonqualified stock options, restricted stock awards, stock appreciation rights, performance stock awards, performance cash awards, restricted stock units and other stock awards to employees, directors and consultants. Stock options granted must be at prices not less than 100% of the fair market value at date of grant. Option vesting schedules were determined by the Company at the time of issuance and generally have a four year vesting schedule. Options generally expire ten years from the date of grant . Unvested options exercised are subject to the Company’s repurchase right.

In June 2024, the Company’s 2024 Equity Incentive Plan (the “2024 Plan”), the successor to and continuation of the 2014 Plan, became effective. The 2024 Plan provides for the grant of incentive stock options, nonqualified stock options, stock appreciation rights, restricted stock awards, restricted stock unit awards and performance stock awards to employees, directors and consultants. Stock options granted must be at prices not less than 100% of the fair market value at date of grant. Option vesting schedules are determined by the Company at the time of issuance and generally have a four year vesting schedule. Options generally expire ten years from the date of grant. Unvested options exercised are subject to the Company’s repurchase right. As of December 31, 2025, the Company has reserved 823,929 shares of its common stock that remains unissued for issuance under the 2024 Plan.

Issuance of shares upon share option exercise or share unit conversion is made through issuance of new shares authorized under the plan.

Certain Common Stock option holders have the right to exercise unvested options, subject to a right held by the Company to repurchase the stock, at the original exercise price, in the event of voluntary or involuntary termination of employment of the stockholder. The shares are generally released from repurchase provisions ratably over four years. The Company accounts for the cash received in consideration for the early exercised options as a liability. At December 31, 2025 and 2024, no shares of Common Stock were subject to repurchase by the Company.

In February 2023, the Company granted 6,366 total shares of PRSUs to certain executives for the performance period beginning January 1, 2023 and ending December 31, 2026. In February 2022, the Company granted 11,218 total shares of PRSUs to certain executives for the performance period beginning January 1, 2022 and ending December 31, 2025. The ultimate number of shares eligible to vest for PRSUs range from 0% to 200% of the target number of shares depending on achievement relative to the predefined clinical performance metrics and continued employment with the Company. During the year ended December 31, 2025, 93 shares of the PRSUs have vested and been released.

In February 2023, the Company granted 6,366 total shares of TSR awards to certain executives for the performance period beginning January 1, 2023 and ending December 31, 2026. In February 2022, the Company granted 11,218 total shares of TSR awards to certain executives for the performance period beginning January 1, 2022 and ending December 31, 2025. The ultimate number of shares eligible to vest for the TSR awards range from 0% to 200% of the target number of shares depending on the TSR of the Company’s common stock as compared to companies in the NBI index, and continued employment with the Company. During the year ended December 31, 2025, no TSR awards shares have vested and been released.

Stock option transactions, including forfeited options granted under the 2024 Plan as well as prior plans, are summarized below:


	Shares (In thousands)			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life (In Years)		Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2024		389		$	400.52
Granted		263			15.14
Forfeited		(82	)		59.65
Expired		(197	)		577.45
Outstanding at December 31, 2025		373			110.26		8.23	$	30
Vested and expected to vest, December 31, 2025		329			122.04		8.15		28
Exercisable at December 31, 2025		146		$	240.24		7.33	$	12

The estimated weighted-average fair value of the stock options granted during the years ended December 31, 2025 and 2024 was $15.14 and $43.43, respectively. There was no option exercised during the years ended December 31, 2025 and 2024.

The following table summarizes the activities of RSUs, PRSUs and TSR awards:


	Shares (In thousands)			Weighted Average Fair Value at Grant
Unvested at December 31, 2024		53		$	235.21
Granted		—			—
Vested		(18	)		205.80
Forfeited		(19	)		289.51
Unvested at December 31, 2025		16		$	201.50

Among the vested RSUs during the year ended December 31, 2025, 10,204 shares were released and issued, while the remaining was withheld for the related payroll taxes. There was no awards granted during the year ended December 31, 2025. The estimated weighted-average fair value of the awards granted during the years ended December 31, 2024 was $44.47.

ESPP

In September 2014, the Company adopted a 2014 ESPP that became effective in November 2014. The 2014 ESPP is designed to enable eligible employees to periodically purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan or IRS limitations. At the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last day of the offering period. Purchases are accomplished through participation in discrete offering periods. The 2014 ESPP is intended to qualify as an ESPP under Section 423 of the Internal Revenue Code. The Company has reserved 64,000 shares of its common stock for issuance under the 2014 ESPP. There were 14,163 shares purchased by employees under the 2014 ESPP during the years ended December 31, 2024. The 2014 ESPP was suspended as of December 31, 2024.

Stock-Based Compensation

Stock-based compensation expense was recorded directly to research and development and selling, general and administrative expense for the years the years ended December 31, 2025 and 2024 was as follows (in thousands):


	Years Ended December 31,
	2025		2024
Research and development	$	2,322	$	12,064
Selling, general and administrative		4,023		11,381
Total stock-based compensation expense	$	6,345	$	23,445

The fair value of employee stock-based compensation is estimated using the following assumptions:

•

Expected Dividend Yield. The Company has never declared or paid any cash dividends and does not plan to pay cash dividends in the foreseeable future.

The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows:


	Years Ended December 31,
	2025			2024
Stock Options
Expected term (in years)		5.4			6.1
Expected volatility		123.8	%		113.7	%
Risk-free interest rate		4.3	%		4.2	%
Expected dividend yield		—			—
Weighted average estimated fair value	$	13.23		$	1.49

ESPPs
Expected term (in years)		—		0.5 - 2.0
Expected volatility		—	%	61.5 - 271.2		%
Risk-free interest rate		—	%	2.6 - 5.3		%
Expected dividend yield		—			—
Weighted average estimated fair value	$	—		$	1.67

The assumptions used to estimate the fair value of the TSR awards using the Monte Carlo valuation model were as follows:


	Year Ended December 31,
	2025			2024
TSR awards
Expected term (in years)		3.9			3.9
Expected volatility	69.0 - 73.3		%	69.0 - 73.3		%
Risk-free interest rate	1.8 - 4.2		%	1.8 - 4.2		%
Expected dividend yield		—			—
Weighted average estimated fair value	$	759.23		$	737.88

As of December 31, 2025, there was $3.6 million of total unrecognized compensation costs, net of estimated forfeitures, related to non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period of 2.50 years. As of December 31, 2025, there was $1.7 million of total unrecognized compensation costs, net of estimated forfeitures, related to non-vested RSUs, PRSUs and TSR awards granted that will be recognized on a straight-line basis over the weighted-average period of 1.73 years.

Subsidiary Stock and Non-Controlling Interests

FibroGen Europe

FibroGen Europe has a total of 42,619,022 shares of Preferred Stock outstanding, of which there are 1,700,845 shares of Series A Preferred Stock, 1,875,000 shares of Series B Preferred Stock, 1,599,503 shares of Series C Preferred Stock, 1,520,141 shares of Series D Preferred Stock, 459,565 shares of Series E Preferred Stock, 5,714,332 shares of Series F Preferred Stock, 9,927,500 shares of Series G Preferred Stock and 19,822,136 shares of Series H Preferred Stock, all of which shares no longer have any right to be exchanged for the Company’s Common Stock. Of all the Preferred Stock outstanding, a total of 37,184,807 shares are owned by Kyntra Bio and 5,434,215 shares are owned by minority shareholders. In addition, FibroGen Europe has 7,800,000 common shares outstanding owned by Kyntra Bio. The holders of FibroGen Europe’s shares of Preferred Stock (“Preferred Shares”) have the following rights, preferences and privileges:

Dividend Rights — When the assets of FibroGen Europe are distributed (except for distribution in a liquidation), Preferred Shares shall have the same rights to dividend or other forms of distribution as shares of Common Stock of FibroGen Europe. In the event of a merger, holders of Preferred Shares do not have the right to demand FibroGen Europe to redeem all or part of their Preferred Shares. FibroGen Europe may repurchase shares of Common Stock or Preferred Shares for consideration.

Pre-emptive Right — Preferred Shares shall have pre-emptive subscription right in accordance with the Finnish Limited Liability Companies Act if additional shares are issued, option rights are given, or convertible loan is taken, provided, however, that the foregoing pre-emptive right does not apply to a directed share issue, for which two thirds (2/3) of the voting shares represented at a general meeting of shareholders approve for an important legitimate cause.

Redemption Right — If a Preferred Share can be redeemed by a majority shareholder owning more than ninety percent (90%) of the shares of FibroGen Europe in accordance with the provisions of the Finnish Limited Liability Companies Act, the minority holders of Preferred Shares have the right to request redemption of their shares.

Voting Right — Each share has one vote. Preferred Shares have voting rights only in situations that are specifically provided in the Articles of Association, which include a merger transaction and directed share issue. In addition, Preferred Shares have right to vote in a general shareholder meeting for amending the Articles of Association if the amendment will affect the rights of Preferred Shares.

Conversion Right (1-for-1 basis into Common Stock of FibroGen Europe):

•

Voluntary conversion right: Preferred Shares can be converted into common shares upon the written request of a shareholder provided that the conversion is feasible within the maximum and minimum amounts of shares of classes of FibroGen Europe as set forth in its Articles of Association. Such request can be withdrawn before the notification of conversion is filed with the Finnish Trade Register.

•

Compulsory conversion right: Preferred Shares will be converted into common shares if (i) FibroGen Europe’s shares are listed in a stock exchange or other trading system in the European Economic Area, or (ii) FibroGen Europe’s recombinant collagen and gelatin production technology is being put into commercial use in the area of Europe and certain other European states. Commercial use means there is income generated from the first commercial sale of the products incorporating the above-mentioned technology and does not include license fees, development financing, milestone payments or income from test products or equipment used in research. The board of directors of FibroGen Europe shall notify the shareholders of the compulsory conversion in writing, and the shareholders shall request to convert their shares within the timeframe provided in the notification. Should the shareholders fail to make the conversion request within the time limit, FibroGen Europe may redeem the shares of such shareholders.

Liquidation Right — In the event of a dissolution of FibroGen Europe, holders of Preferred Shares are entitled to be paid in an amount equal to the subscription price of the shares before any distribution is made to holders of common shares. Among holders of Preferred Shares, holders of shares of Series F Preferred Stock are entitled to be paid in an amount equal to the subscription price of Series F Preferred Stock before any distribution is made to holders of other Preferred Shares.

Non-controlling interest positions related to the issuance of FibroGen Europe’s stock are reported as a separate component of consolidated equity from the equity attributable to the Company’s stockholders. In addition, the Company does not allocate losses to the non-controlling interests as the outstanding shares representing the non-controlling interest do not represent a residual equity interest in FibroGen Europe.

FibroGen Cayman

FibroGen Cayman has 15,836,966 Series A Preference Shares outstanding, including 10,484,260 shares owned by Kyntra Bio. and 5,352,706 shares owned by minority shareholders, and 78,000,000 common shares outstanding owned by Kyntra Bio. The holders of the FibroGen Cayman Series A Preference Shares have the following rights, preferences and privileges:

Liquidation — In the event of liquidation, dissolution, or winding up of the entity, either voluntary or involuntary, including by means of a merger, the holders of FibroGen Cayman Series A Preference Shares are entitled to be paid an amount equal to their liquidation preference as set forth in the FibroGen Cayman Amended and Restated Memorandum and Articles of Association (the “Articles”), i.e. the product of the number of shares held by a holder of shares of FibroGen Cayman Series A Preference Shares and the original issue price of $1.00 (subject to equitable adjustment for any stock dividend, combination, split, reclassification, recapitalization) plus all declared and unpaid dividends thereon.

Conversion — Each share of FibroGen Cayman Series A Preference Shares is convertible into the number of fully paid and non-assessable shares of Common Stock of FibroGen Cayman that results from dividing the original issue price by the conversion price in effect at the time of the conversion, subject to adjustments for stock splits, stock dividends, reclassifications and like events. The FibroGen Cayman Series A Preference Shares have a conversion price that is equal to the original issuance price such that the conversion ratio to FibroGen Cayman Common Stock is 1:1 as of all periods presented.

Voting — The holders of FibroGen Cayman Series A Preference Shares are entitled to vote together with the FibroGen Cayman Common Stockholders on all matters submitted for a vote of the stockholders. The holder of each share of FibroGen Cayman Series A Preference Shares has the number of votes equal to the number of shares of FibroGen Cayman Common Stock into which it is convertible.

Dividends — The holders of FibroGen Cayman Series A Preference Shares are entitled to receive cash dividends when and if declared, at a rate of 6%.

The discontinued operations sold under the Transaction discussed in the above Note 3, Discontinued Operations and Divestiture, consisted substantially all the assets owned by FibroGen Cayman, and therefore triggered liquidation distribution process of FibroGen Cayman based on its Articles.

Accordingly, during the year ended December 31, 2025, the Company distributed a total of $5.4 million to FibroGen Cayman’s minority shareholders ($1.00 for each of the FibroGen Cayman Series A Preference Shares held by the minority shareholders), and correspondingly recorded a reduction to the related nonredeemable non-controlling interests of $7.5 million and an adjustment to additional paid-in capital of $2.1 million, for such distribution.

Any further distribution, if applicable, will be paid out on a pro-rata basis to the holders of all common and Series A Preference shares of FibroGen Cayman, and is subject to future adjustments, if any, including additional proceeds received from the holdbacks related to the Transaction, and future costs of FibroGen Cayman.

Income Taxes - Schedule of Reconciliation Between Statutory Federal Income Tax Rate and Effective Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Tax at statutory federal rate, Amount	$ (12,242)
Tax at statutory federal rate	21.00%	21.00%
State tax, net of federal benefit, Amount	$ 0
State tax, net of federal benefit	0.00%	0.00%
Foreign Rate Differential		(1.40%)
Global intangible low-taxed income, Amount	$ 62,730
Global intangible low-taxed income	(107.60%)	(2.10%)
Other, Amount	$ (90)
Other	0.20%
Tax credits, Amount	$ 578
Tax credits	(1.00%)
Change in valuation allowance, Amount	$ (59,391)
Change in valuation allowance	101.90%
Worldwide changes in unrecognized tax benefits, Amount	$ (180)
Worldwide changes in unrecognized tax benefits	0.30%
Stock based compensation, Amount	$ 5,591
Stock based compensation	(9.60%)
Disallowed interest, Amount	$ 448
Disallowed interest	(0.80%)
Other, Amount	$ 9
Other	0.00%
Stock-based compensation expense		(3.20%)
Net operating losses not benefitted		(13.90%)
Deduction limitation on executive compensation		(0.00%)
Other, Amount	$ 271
Other	(0.50%)	(0.20%)
Benefit from income taxes	$ (90)	$ (269)
Total	0.20%	0.20%
Cayman Islands
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Foreign Rate Differential, Amount	$ 2,110
Foreign Rate Differential	(3.60%)
Finland
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Foreign Rate Differential, Amount	$ 76
Foreign Rate Differential	(0.10%)

Discontinued Operations and Divestiture - Schedule of Significant Non-cash Items and Capital Expenditures for Discontinued Operations (Detail) - USD ($) $ in Thousands		12 Months Ended
	Aug. 29, 2025	Dec. 31, 2025	Dec. 31, 2024
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation		$ 713	$ 2,654
Investment income in unconsolidated variable interest entity		(2,485)	(3,969)
Gain on divestiture		(52,553)	0
Impairment of property and equipment		2,062	0
Dividend received from unconsolidated variable interest entity		3,947	2,230
Stock-based compensation		6,576	25,215
FibroGen International [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Depreciation		713	1,458
Investment income in unconsolidated variable interest entity		(2,486)	(3,969)
Gain on divestiture	$ (52,600)	(52,553)	0
Impairment of property and equipment		2,062	0
Dividend received from unconsolidated variable interest entity		3,947	2,230
Stock-based compensation		$ 231	$ 1,770

Equity and Stock-based Compensation - Summary of RSU,PRSU and TSR Awards (Detail) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Shares, Beginning Balance	53
Unvested, Shares, Ending Balance	16	53
Granted, Weighted Average Fair value at Grant		$ 44.47
RSUs, PRSUs and TSR awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unvested, Shares, Beginning Balance	53
Granted, Shares	0
Vested, Shares	(18)
Forfeited, Shares	(19)
Unvested, Shares, Ending Balance	16	53
Unvested, Weighted Average Fair value at Grant, Beginning Balance	$ 235.21
Vested, Weighted Average Fair value at Grant	205.8
Forfeited, Weighted Average Fair value at Grant	289.51
Unvested, Weighted Average Fair value at Grant, Ending Balance	$ 201.50	$ 235.21

Balance Sheet Components - Additional Information (Detail) - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Jul. 31, 2024	Dec. 31, 2025	Dec. 31, 2025	Dec. 31, 2024
Schedule of Available-for-sale Securities [Line Items]
Other-than-temporary impairment loss			$ 0
Available for sale investments contractual maturities			2 years
Litigation settlement receivable		$ 0	$ 0	$ 28,500,000
Depreciation expense for the continuing operations			713,000	2,654,000
API and bulk drug product price true-up		6,977,000	6,977,000	13,071,000
Short-term investments		41,106,000	41,106,000	0
Long-term investment		20,160,000	20,160,000	0
Accrued litigation settlement				28,500,000
Restructuring plan, expected reduction to workforce, percentage	75.00%
Restructuring plan, non-recurring charges			553,000	19,454,000
Cash payments for restructuring			3,500,000	$ 16,500,000
Accrued restructuring charges		500,000	500,000
Closing of Divestiture of FibroGen International [Member]
Schedule of Available-for-sale Securities [Line Items]
Litigation settlement receivable		4,000,000	$ 4,000,000
Astellas Agreement [Member]
Schedule of Available-for-sale Securities [Line Items]
Payment to related parties		$ 7,100,000

Discontinued Operations and Divestiture

12 Months Ended

Dec. 31, 2025

Discontinued Operations and Disposal Groups [Abstract]

Discontinued Operations and Divestiture

3. Discontinued Operations and Divestiture

On February 20, 2025, the Company entered into the Share Purchase Agreement with AstraZeneca Treasury Limited, pursuant to which the Company and its subsidiary FibroGen China Anemia Holdings, Ltd. agreed to sell all of the issued and outstanding equity interests of FibroGen International to AstraZeneca Treasury Limited. This sale includes all of the Company’s roxadustat assets in China, including FibroGen International’s subsidiary FibroGen Beijing and its 51.1% interest in Falikang. The Company determined that FibroGen International met the “held for sale” criteria and the “discontinued operations” criteria in accordance with FASB ASC 205, Presentation of Financial Statements, as of December 31, 2024. Accordingly, the operating results related to the FibroGen International are classified as discontinued operations, and have been reflected as discontinued operations in the consolidated statements of operations, while the related assets and liabilities were classified within the consolidated balance sheets as held for sale for all periods presented.

The Transaction was closed on August 29, 2025 for a total consideration of $220.4 million comprised of $85.0 million in cash for the enterprise value of FibroGen International and $135.4 million in net cash held in China. The total consideration included a $210.4 million in cash paid at closing, and a total of $10.0 million cash payable by AstraZeneca at the closing subject to holdbacks of: (i) a $6.0 million holdback to offset final net cash adjustments which will be released following a customary adjustment process approximately 90 days post-closing (as such time may be extended for the parties to mutually agree upon final adjustments), and (ii) a $4.0 million holdback to satisfy any indemnity claims, which will be released, net of any claims paid or unresolved, nine months after the closing. The Company does not expect such adjustments to be material, therefore have recorded the $10.0 million as other receivable, which were included in the prepaid expenses and other current assets on the consolidated balance sheets. On November 6, 2025, the Company received a $6.4 million payment from AstraZeneca, which is in full satisfaction of the first holdback of $6.0 million, plus $0.4 million that was an additional payment following the final net cash adjustments after closing.


	Years Ended December 31,
	2025			2024
Revenue:
Product revenue, net	$	226,651		$	173,664
Operating costs and expenses:
Cost of goods sold		13,454			21,036
Research and development		1,739			7,375
Selling, general and administrative		14,849			32,304
Total operating costs and expenses		30,042			60,715
Income from operations		196,609			112,949
Interest and other, net
Interest expense		(7,816	)		(11,683	)
Gain on divestiture		52,553			—
Interest income and other income (expenses), net		(2,173	)		423
Total interest and other, net		42,564			(11,260	)
Income before income taxes		239,173			101,689
Provision for income taxes		—			139
Investment income in unconsolidated variable interest entity		2,483			3,969
Income from discontinued operations, net of tax	$	241,656		$	105,519

The product revenue, net, consists primarily of revenues from sales of roxadustat commercial product to Falikang, a distribution entity jointly owned by AstraZeneca and FibroGen Beijing, and is discussed in the China Performance Obligation section in Note 4, Collaboration Agreements, License Agreement and Revenues.

The gain on divestiture of $52.6 million resulted from the above-mentioned total consideration of $220.4 million and additional payment of $0.4 million related to the first holdback, less the transaction costs and fees of $7.8 million, and the derecognition of the net equity of $154.9 million of FibroGen International at the Transaction close and the cumulative currency translation adjustments of $5.5 million.


	December 31, 2024
Assets
Cash and cash equivalents	$	51,696
Accounts receivable, net		18,443
Inventories		15,547
Prepaid expenses and other current assets		25,163
Total current assets held for sale		110,849

Property and equipment, net		7,041
Equity method investment in unconsolidated variable interest entity		6,864
Operating lease right-of-use assets		1,716
Other assets		990
Total long-term assets held for sale		16,611

Liabilities
Accounts payable	$	26,974
Accrued and other current liabilities		10,679
Operating lease liabilities, current		1,264
Total current liabilities held for sale		38,917

Operating lease liabilities, non-current		356
Total long-term liabilities held for sale		356


	Years Ended December 31,
	2025			2024
Depreciation	$	713		$	1,458
Investment income in unconsolidated variable interest entity		(2,486	)		(3,969	)
Gain on divestiture		(52,553	)		—
Impairment of property and equipment		2,062			—
Dividend received from unconsolidated variable interest entity		3,947			2,230
Stock-based compensation	$	231		$	1,770

Included in the discontinued operations, Falikang, an entity jointly owned by FibroGen Beijing and AstraZeneca is an unconsolidated VIE accounted for as an equity method investment, and considered as a related party to the Company. FibroGen Beijing owns 51.1% of Falikang’s equity.

For the years ended December 31, 2025 and 2024, the net product revenue from sales to Falikang were $218.6 million and $159.0 million, respectively. The other income from Falikang were immaterial for the years ended December 31, 2025 and 2024.

For the years ended December 31, 2025 and 2024, the investment income in Falikang was $2.5 million and $4.0 million, respectively. As of December 31, 2024, the Company’s equity method investment in Falikang were $6.9 million which was included in the long-term assets held for sale on the consolidated balance sheets. As of December 31, 2024 accounts receivable, net, from Falikang were $13.9 million which were included in the current assets held for sale on the consolidated balance sheets.

Equity and Stock-based Compensation - Stock Plans - Additional information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended		12 Months Ended
	Feb. 28, 2023	Feb. 28, 2022	Dec. 31, 2025	Dec. 31, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total intrinsic value of options exercised			$ 12
RSUs released and issued net of shares withheld for taxes			10,204
Weighted-average fair value of awards granted				$ 44.47
Weighted average fair value of stock options granted			$ 15.14	43.43
PRSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares	6,366	11,218
Shares vested			93
TSR [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted average fair value of stock options granted			$ 759.23	$ 737.88
Granted, Shares	6,366	11,218
Shares vested			0
RSUs, PRSUs and TSR awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Granted, Shares			0
Maximum [Member] \| PRSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of vesting rights		200.00%
Maximum [Member] \| TSR [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of vesting rights		200.00%
Minimum [Member] \| PRSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of vesting rights		0.00%
Minimum [Member] \| TSR [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of vesting rights		0.00%
2014 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of stock options			10 years
Option vesting term			Option vesting schedules were determined by the Company at the time of issuance and generally have a four year vesting schedule.
Number of common stock repurchased			0	0
Total intrinsic value of options exercised			$ 0	$ 0
2014 Equity Incentive Plan \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair value exercise price grant date			100.00%
2024 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of stock options			10 years
Option vesting term			Option vesting schedules are determined by the Company at the time of issuance and generally have a four year vesting schedule.
Number of common stock reserved for issuance			823,929
2024 Equity Incentive Plan \| Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of fair value exercise price grant date			100.00%

Equity and Stock-based Compensation (Tables)

12 Months Ended

Dec. 31, 2025

Share-Based Payment Arrangement [Abstract]

Summary of Common Stock Reserved for Future Issuance


	December 31,
	2025		2024
Common stock outstanding		4,047		4,037
Stock options outstanding		373		389
RSUs outstanding		16		53
Shares reserved for future stock options and RSUs grant		818		776
Shares reserved for future ESPP offering		265		265
Total shares of common stock reserved		5,519		5,520

Summary of Stock Option Transactions

Stock option transactions, including forfeited options granted under the 2024 Plan as well as prior plans, are summarized below:


	Shares (In thousands)			Weighted Average Exercise Price per Share		Weighted Average Remaining Contractual Life (In Years)		Aggregate Intrinsic Value (In thousands)
Outstanding at December 31, 2024		389		$	400.52
Granted		263			15.14
Forfeited		(82	)		59.65
Expired		(197	)		577.45
Outstanding at December 31, 2025		373			110.26		8.23	$	30
Vested and expected to vest, December 31, 2025		329			122.04		8.15		28
Exercisable at December 31, 2025		146		$	240.24		7.33	$	12

Summary of RSU,PRSU and TSR Awards

The following table summarizes the activities of RSUs, PRSUs and TSR awards:


	Shares (In thousands)			Weighted Average Fair Value at Grant
Unvested at December 31, 2024		53		$	235.21
Granted		—			—
Vested		(18	)		205.80
Forfeited		(19	)		289.51
Unvested at December 31, 2025		16		$	201.50

Schedule of Recorded Stock-Based Compensation Expense


	Years Ended December 31,
	2025		2024
Research and development	$	2,322	$	12,064
Selling, general and administrative		4,023		11,381
Total stock-based compensation expense	$	6,345	$	23,445

Schedule of Assumptions used to Estimate Fair Value of Stock Options Granted and Employee Stock Purchase Plans

The assumptions used to estimate the fair value of stock options granted and ESPPs using the Black-Scholes option valuation model were as follows:


	Years Ended December 31,
	2025			2024
Stock Options
Expected term (in years)		5.4			6.1
Expected volatility		123.8	%		113.7	%
Risk-free interest rate		4.3	%		4.2	%
Expected dividend yield		—			—
Weighted average estimated fair value	$	13.23		$	1.49

ESPPs
Expected term (in years)		—		0.5 - 2.0
Expected volatility		—	%	61.5 - 271.2		%
Risk-free interest rate		—	%	2.6 - 5.3		%
Expected dividend yield		—			—
Weighted average estimated fair value	$	—		$	1.67

Schedule of Assumptions used to Estimate Fair Value of TSR Awards

The assumptions used to estimate the fair value of the TSR awards using the Monte Carlo valuation model were as follows:


	Year Ended December 31,
	2025			2024
TSR awards
Expected term (in years)		3.9			3.9
Expected volatility	69.0 - 73.3		%	69.0 - 73.3		%
Risk-free interest rate	1.8 - 4.2		%	1.8 - 4.2		%
Expected dividend yield		—			—
Weighted average estimated fair value	$	759.23		$	737.88

Income Taxes - Schedule of Components of Provision For Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Current:
Federal	$ 0	$ 0
State	0	0
Foreign	(90)	(269)
Total current	(90)	(269)
Deferred:
Federal	0	0
State	0	0
Foreign	0	0
Total deferred	0	0
Benefit from income taxes	$ (90)	$ (269)

The Company

12 Months Ended

Dec. 31, 2025

Organization, Consolidation and Presentation of Financial Statements [Abstract]

The Company

1. The Company

Kyntra Bio, Inc. (“Kyntra Bio” or the “Company”) is a biopharmaceutical company focused on development of novel therapies at the frontiers of cancer biology and anemia.

In January 2026, the Company announced its rebranding from “FibroGen, Inc.” to “Kyntra Bio, Inc.”, representing the next step of its transformation and focus on oncology and associated rare disease indications. On January 8, 2026, the Company’s common stock began trading under the new Nasdaq symbol “KYNB.”

The Company is developing FG-3246, a potential first-in-class antibody-drug conjugate (“ADC”) targeting CD46, for the treatment of metastatic castration-resistant prostate cancer (“mCRPC”) and potentially other cancers. This program also includes the development of FG-3180, an associated CD46-targeted positron emission tomography (“PET”) biomarker and imaging agent. The Company initiated a Phase 2 monotherapy dose optimization study of FG-3246 for the treatment of mCRPC, along with the exploratory sub-study of FG-3180, in the third quarter of 2025.

The Company and its collaboration partners developed roxadustat (爱瑞卓®, EVRENZOTM), which is currently approved in Europe, Japan, the People’s Republic of China (“China”), and numerous other countries for the treatment of anemia in chronic kidney disease (“CKD”) patients on dialysis and not on dialysis.

On August 29, 2025, the Company closed the sale of its China operations through FibroGen International (Hong Kong) Ltd. (“FibroGen International”) to AstraZeneca Treasury Limited pursuant to the share purchase agreement entered into by the Company and AstraZeneca Treasury Limited on February 20, 2025, as amended (the “Share Purchase Agreement”) for a total consideration of $220.4 million comprised of $85.0 million in enterprise value and $135.4 million in net cash held in China. AstraZeneca AB (“AstraZeneca”) was the Company’s long-time commercialization partner for roxadustat in greater China. This sale included all of its roxadustat assets in China, including FibroGen International’s subsidiary FibroGen (China) Medical Technology Development Co., Ltd (“FibroGen Beijing”) and its 51.1% interest in Beijing Falikang Pharmaceutical Co. Ltd. (“Falikang”). For additional details, refer to Note 3, Discontinued Operations and Divestiture.

The Company has retained the rights to roxadustat in the United States of America (“U.S.”), Canada, Mexico, and in all markets not held by AstraZeneca or licensed to Astellas Pharma Inc. (“Astellas”). Astellas is commercializing roxadustat (EVRENZOTM) in Europe and Japan to treat anemia under two development and commercialization license agreements: one for Japan, and one for Europe, the Commonwealth of Independent States, the Middle East and South Africa.

The Company continues to advance its development plan for roxadustat in anemia associated with lower-risk myelodysplastic syndromes (“MDS”), a high-value indication with significant unmet medical need. The Company had a positive Type-C meeting with the U.S. Food and Drug Administration (“FDA”) in July 2025 and reached alignment on several elements of its proposed Phase 3 study design for roxadustat in anemia associated with lower-risk MDS, including the starting dose and the patient inclusion criteria. The Company is starting preparations for the Phase 3 trial, while evaluating internal development and potential partnership opportunities for this late-stage program. The Company submitted the Phase 3 trial protocol for roxadustat for the treatment of anemia in patients with lower-risk MDS and high transfusion burden to the FDA in December 2025.

The FDA granted Roxadustat Orphan Drug Designation for the treatment of MDS in December 2025.

Consolidated Statements of Changes in Redeemable Non-Controlling Interests and Stockholders' Deficit - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Deficit [Member]	Noncontrolling Interests [Member]	Noncontrolling Interests [Member] Redeemable [Member]
Balance at Dec. 31, 2023	$ (183,679)	$ 988	$ 1,643,641	$ (6,875)	$ (1,841,920)	$ 20,487	$ 21,480
Balance, Shares at Dec. 31, 2023		3,950,809
Net income (loss)	(47,579)	$ 0	0	0	(47,579)	0	0
Change in unrealized gain or loss on investments	(23)	0	0	(23)	0	0	0
Foreign currency translation adjustments	1,166	0	0	1,166	0	0	0
Cumulative currency translation adjustment attributable to divestiture (Note 3)	0
Shares issued from stock plans, net of payroll taxes paid	(215)	$ 21	(236)	0	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		85,869
Stock-based compensation	25,215	$ 0	25,215	0	0	0	0
Balance at Dec. 31, 2024	(205,115)	$ 1,009	1,668,620	(5,732)	(1,889,499)	20,487	21,480
Balance, Shares at Dec. 31, 2024		4,036,678
Net income (loss)	183,452	$ 0	0	0	183,452	0	0
Change in unrealized gain or loss on investments	37	0	0	37	0	0	0
Foreign currency translation adjustments	(1,966)	0	0	(1,966)	0	0	0
Cumulative currency translation adjustment attributable to divestiture (Note 3)	5,479			5,479
Distribution to non-controlling interest (Note 12)	(5,353)	0	2,101	0	0	(7,454)	0
Shares issued from stock plans, net of payroll taxes paid	(69)	$ 3	(72)	0	0	0	0
Shares issued from stock plans, net of payroll taxes paid, Shares		10,204
Issuance cost under ATM Program	(46)	$ 0	(46)	0	0	0	0
Redemption of fractional shares due to reverse stock split, Shares		(55)
Redemption of fractional shares due to reverse stock split	0	$ 0	0	0	0	0	0
Stock-based compensation	6,576	0	6,576	0	0	0	0
Balance at Dec. 31, 2025	$ (17,005)	$ 1,012	$ 1,677,179	$ (2,182)	$ (1,706,047)	$ 13,033	$ 21,480
Balance, Shares at Dec. 31, 2025		4,046,827

Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Revenue:
Total revenue	$ 6,440	$ 29,621
Operating costs and expenses:
Cost of goods sold	$ 556	$ 15,561
Cost, Product and Service [Extensible List]	Product Revenue, Net [Member]	Product Revenue, Net [Member]
Research and development	$ 23,517	$ 95,692
Selling, general and administrative	27,709	49,330
Restructuring charge	553	19,454
Total operating costs and expenses	52,335	180,037
Loss from operations	(45,895)	(150,416)
Interest and other, net
Interest expense	(8,759)	(8,247)
Loss on debt extinguishments	(6,583)	0
Interest income and other income (expenses), net	2,943	5,296
Total interest and other, net	(12,399)	(2,951)
Loss from continuing operations before income taxes	(58,294)	(153,367)
Benefit from income taxes	(90)	(269)
Loss from continuing operations	(58,204)	(153,098)
Income from discontinued operations, net of tax	241,656	105,519
Net income (loss)	$ 183,452	$ (47,579)
Loss from continuing operations per share - basic	$ (14.4)	$ (38.26)
Loss from continuing operations per share - diluted	(14.4)	(38.26)
Income from discontinued operations per share - basic	59.77	26.37
Income from discontinued operations per share - diluted	59.77	26.37
Net income (loss) per share - basic	45.37	(11.89)
Net income (loss) per share - diluted	$ 45.37	$ (11.89)
Weighted average number of common shares used to calculate net income (loss) per share:
Basic	4,043	4,002
Diluted	4,043	4,002
Development and Other Revenue [Member]
Revenue:
Total revenue	$ 592	$ 1,948
Drug Product Revenue, Net [Member]
Revenue:
Total revenue	$ 5,848	$ 27,673

Liability Related to Sale of Future Revenues (Tables)

12 Months Ended

Dec. 31, 2025

Schedule of Activity of Liability Related to Sale of Future Revenues

The table below shows the activity of the liability related to sale of future revenues for the year ended December 31, 2025 and 2024:


	For the Year Ended December 31,
	2025			2024
Liability related to sale of future revenues - beginning balance	$	59,324		$	57,067
Interest paid		(450	)		(5,653	)
Interest expense recognized		8,440			7,910
Liability related to sale of future revenues - ending balance		67,314			59,324
Less: Current portion classified to accrued and other current liabilities		(1,334	)		(460	)
Liability related to sale of future revenues, non-current	$	65,980		$	58,864

Equity and Stock-based Compensation - Stock-Based Compensation - Additional information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($)
Stock Option Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation costs	$ 3.6
Non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period	2 years 6 months
RSUs, PRSUs and TSR Awards [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Non-vested stock option awards granted that will be recognized on a straight-line basis over the weighted-average period	1 year 8 months 23 days
Unrecognized compensation costs	$ 1.7

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Schedule of Components of Loss Before Income Taxes

The components of loss before income taxes are as follows (in thousands):


	Years Ended December 31,
	2025			2024
Domestic	$	(47,917	)	$	(142,819	)
Foreign		(10,377	)		(10,548	)
Loss before benefit for income taxes	$	(58,294	)	$	(153,367	)

Schedule of Components of Provision For Income Taxes

The benefit for income taxes consists of the following (in thousands):


	Years Ended December 31,
	2025			2024
Current:
Federal	$	—		$	—
State		—			—
Foreign		(90	)		(269	)
Total current		(90	)		(269	)
Deferred:
Federal		—			—
State		—			—
Foreign		—			—
Total deferred		—			—
Benefit from income taxes	$	(90	)	$	(269	)

Schedule of Reconciliation Between Statutory Federal Income Tax Rate and Effective Tax Rate

A reconciliation of the benefit for income taxes to the amount computed by applying the 21% statutory U.S. federal income tax rate to income before income taxes for the year ended December 31, 2025, after the adoption of ASU 2023-09, is as follows:


	Years Ended December 31, 2025
	Amount			%
Tax at statutory federal rate	$	(12,242	)		21.0	%
State tax, net of federal benefit		—			—	%
Foreign Tax Effects
Foreign Rate Differential – Cayman Islands		2,110			(3.6	)%
Foreign Rate Differential – Finland		76			(0.1	)%
Effect of cross-border tax laws
Global intangible low-taxed income		62,730			(107.6	)%
Other		(90	)		0.2	%
Tax credits		578			(1.0	)%
Change in valuation allowance		(59,391	)		101.9	%
Worldwide changes in unrecognized tax benefits		(180	)		0.3	%
Nondeductible items
Stock based compensation		5,591			(9.6	)%
Disallowed interest		448			(0.8	)%
Other		9			—	%
Other		271			(0.5	)%
Total	$	(90	)		0.2	%

The following is the reconciliation between the statutory federal income tax rate and the Company’s effective tax rate for year ended in December 31, 2024, prior to the adoption of ASU 2023-09, is as follows:


	Years Ended December 31,
	2024
Tax at statutory federal rate		21.0	%
State tax		—	%
Stock-based compensation expense		(3.2	)%
Net operating losses not benefitted		(13.9	)%
Foreign net operating losses not benefitted		(1.4	)%
Deduction limitation on executive compensation		—	%
Global intangible low-taxed income		(2.1	)%
Other		(0.2	)%
Total		0.2	%

Schedule of Significant Components of Deferred Tax Assets

Significant components of the Company’s deferred tax assets are as follows (in thousands):


	December 31,
	2025			2024
Federal and state net operating loss carryforwards	$	173,195		$	206,365
Tax credit carryforwards		128,924			129,320
Foreign net operating loss carryforwards		112			120
Capitalized research and development expenses		64,293			83,329
Stock-based compensation		2,128			6,365
Lease obligations		12			22
Reserves and accruals		4,760			4,418
Deferred revenue		—			7,785
Intangible assets		14,135			15,036
Other		6			—
Subtotal		387,565			452,760
Less: Valuation allowance		(387,555	)		(452,740	)
Net deferred tax assets		10			20

Fixed assets		(10	)		(20	)
Non-deductible accrued expenses		—			—
Net deferred tax liabilities		(10	)		(20	)
Total net deferred tax assets	$	—		$	—

Schedule of Reconciliation of the Beginning and Ending Amounts of Unrecognized Income Tax Benefits

A reconciliation of the beginning and ending amounts of unrecognized income tax benefits during the two years ended December 31, 2025 is as follows (in thousands):


	Federal and State
Balance as of December 31, 2023	$	70,710
Decrease due to prior positions		(156	)
Increase due to current year position		3,920
Foreign exchange rate differential		(153	)
Balance as of December 31, 2024		74,321
Decrease due to prior positions		(229	)
Increase due to current year position		372
Foreign exchange rate differential		—
Balance as of December 31, 2025	$	74,464

Collaboration Agreements, License Agreement and Revenues - Astellas Agreements - Additional Information (Detail) - USD ($)	1 Months Ended		12 Months Ended
	Apr. 30, 2006	Jun. 30, 2005	Dec. 31, 2025	Dec. 31, 2024
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			$ 6,440,000	$ 29,621,000
Drug Product Revenue, Net [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			5,848,000	27,673,000
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price, variable consideration from estimated future co-development billing			0
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Transaction price, variable consideration from estimated future co-development billing			$ 0
Astellas Agreement [Member] \| Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received		$ 172,600,000
Additional consideration based on net sales description			the low 20% range of the list price
Aggregate considerations received excluding drug product revenue			$ 105,100,000
Transaction price, variable consideration from estimated future co-development billing			0	0
Changes in revenue from changes to estimated variable consideration			0
Astellas Agreement [Member] \| Japan [Member] \| License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash Consideration Received Under Collaboration Agreement			100,300,000
Astellas Agreement [Member] \| Japan [Member] \| Co-development, information sharing & committee services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash Consideration Received Under Collaboration Agreement			$ 17,100,000
Astellas Agreement [Member] \| Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Upfront, non-contingent and time-based payments received	$ 745,000,000
Additional consideration based on net sales description			low 20% range
Aggregate considerations received excluding drug product revenue			$ 685,000,000
Changes in revenue from changes to estimated variable consideration			0
Percentage of joint development costs committed to fund	50.00%
Astellas Agreement [Member] \| Europe [Member] \| License [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Total revenue			0	$ 0
Cash Consideration Received Under Collaboration Agreement			619,000,000
Astellas Agreement [Member] \| Europe [Member] \| Co-development, information sharing & committee services [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Cash Consideration Received Under Collaboration Agreement			$ 288,700,000

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2025	Dec. 31, 2024
Statement of Financial Position [Abstract]
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	125,000,000	125,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	225,000,000	225,000,000
Common stock, shares issued	4,047,000	4,037,000
Common stock, shares outstanding	4,047,000	4,037,000

Equity and Stock-based Compensation - Schedule of Recorded Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 6,345	$ 23,445
Research and development [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	2,322	12,064
Selling, general and administrative [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 4,023	$ 11,381

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2025	Feb. 28, 2026	Jun. 30, 2025
Cover [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2025
Document Fiscal Year Focus	2025
Document Fiscal Period Focus	FY
Trading Symbol	KYNB
Entity Registrant Name	KYNTRA BIO, INC.
Entity Central Index Key	0000921299
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Non-accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Entity Interactive Data Current	Yes
Title of 12(b) Security	Common Stock, $0.01 par value
Security Exchange Name	NASDAQ
Entity File Number	001-36740
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	77-0357827
Entity Address, Address Line One	350 Bay Street
Entity Address, Address Line Two	Suite 100 #6009
Entity Address, City or Town	San Francisco
Entity Address, State or Province	CA
Entity Address, Postal Zip Code	94133
City Area Code	415
Local Phone Number	978-1200
Entity Common Stock, Shares Outstanding		4,046,827
Entity Public Float			$ 21.0
Document Annual Report	true
Document Transition Report	false
ICFR Auditor Attestation Flag	false
Document Financial Statement Error Correction [Flag]	false
Auditor Firm ID	238
Auditor Name	PricewaterhouseCoopers LLP
Auditor Location	Irvine, California
Documents Incorporated by Reference	DOCUMENTS INCORPORATED BY REFERENCE Items 10, 11, 12, 13 and 14 of Part III of this Annual Report on Form 10-K for the year ended December 31, 2025 (the “Annual Report”) incorporate information by reference from the definitive proxy statement for the registrant’s 2026 Annual Meeting of Stockholders to be filed with the Securities and Exchange Commission pursuant to Regulation 14A not later than after 120 days after the end of the fiscal year covered by this Annual Report.

Product Development Obligations

12 Months Ended

Dec. 31, 2025

Debt Disclosure [Abstract]

Product Development Obligations

10. Product Development Obligations

The Technology Development Center of the Republic of Finland (“TEKES”) product development obligations consist of 11 separate advances (each in the form of a note agreement) received by FibroGen Europe between 1996 and 2008 from TEKES. These advances are granted on a project-by-project basis to fund various product development efforts undertaken by FibroGen Europe only. Each separate note is denominated in EUR and bears interest (not compounded) calculated as one percentage point less than the Bank of Finland rate in effect at the time of the note, but no less than 3.0%.

If the research work funded by TEKES does not result in an economically profitable business or does not meet its technological objectives, TEKES may, on application from FibroGen Europe, forgive each of these loans, including accrued interest, either in full or in part. As of December 31, 2025 and 2024, the Company had U.S. Dollar equivalent of $11.1 million and $9.8 million of principal outstanding, respectively, and $8.5 million and $7.2 million of interest accrued, respectively, which were presented in the product development obligations line on the consolidated balance sheets.

The Company is not a guarantor of these loans, and the principal or the accrued interest of these loans are not repayable by FibroGen Europe until it has distributable funds.

Fair Value Measurements - Fair Values of Financial Assets Measured on Recurring Basis (Detail) - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 61,266
Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	27,817
Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	6,525
Fair Value, Measurements, Recurring [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	106,829	$ 48,478
Fair Value, Measurements, Recurring [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	24,302	28,241
Fair Value, Measurements, Recurring [Member] \| Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	27,817
Fair Value, Measurements, Recurring [Member] \| Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	17,797	14,269
Fair Value, Measurements, Recurring [Member] \| U.S. government bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	36,913	5,968
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	56,224	31,228
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	24,302	28,241
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] \| Level 1 [Member] \| U.S. government bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	31,922	2,987
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	50,605	17,250
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	27,817
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	17,797	14,269
Fair Value, Measurements, Recurring [Member] \| Level 2 [Member] \| U.S. government bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	4,991	2,981
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total fair value of financial assets	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Money market funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets fair value disclosure	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Corporate bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| Commercial paper [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	0	0
Fair Value, Measurements, Recurring [Member] \| Level 3 [Member] \| U.S. government bonds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investments	$ 0	$ 0

Consolidated Balance Sheets - USD ($)	Dec. 31, 2025	Dec. 31, 2024
Current assets:
Cash and cash equivalents	$ 47,872,000	$ 50,482,000
Short-term investments	41,106,000	0
Accounts receivable, net	216,000	481,000
Inventories	3,743,000	3,155,000
Prepaid expenses and other current assets	6,136,000	31,542,000
Current assets held for sale	0	110,849,000
Total current assets	99,073,000	196,509,000
Long-term investments	20,160,000	0
Other assets	361,000	1,405,000
Long-term assets held for sale	0	16,611,000
Total assets	119,594,000	214,525,000
Current liabilities:
Accounts payable	3,745,000	5,064,000
Accrued and other current liabilities	20,183,000	62,035,000
Deferred revenue	5,314,000	27,290,000
Current liabilities held for sale	0	38,917,000
Total current liabilities	29,242,000	133,306,000
Product development obligations	19,560,000	17,012,000
Deferred revenue, net of current	255,000	114,708,000
Senior secured term loan facilities, non-current	0	73,092,000
Liability related to sale of future revenues, non-current	65,980,000	58,864,000
Other long-term liabilities	82,000	822,000
Long-term liabilities held for sale	0	356,000
Total liabilities	115,119,000	398,160,000
Commitments and Contingencies (Note 11)
Redeemable non-controlling interests	21,480,000	21,480,000
Stockholders' deficit:
Preferred stock, $0.01 par value; 125,000 shares authorized; no shares issued and outstanding at December 31, 2025 and 2024
Common stock, $0.01 par value; 225,000 shares authorized at December 31, 2025 and 2024; 4,047 and 4,037 shares issued and outstanding at December 31, 2025 and 2024	1,012,000	1,009,000
Additional paid-in capital	1,677,179,000	1,668,620,000
Accumulated other comprehensive loss	(2,182,000)	(5,732,000)
Accumulated deficit	(1,706,047,000)	(1,889,499,000)
Total stockholders' deficit attributable to Kyntra Bio	(30,038,000)	(225,602,000)
Nonredeemable non-controlling interests	13,033,000	20,487,000
Total deficit	(17,005,000)	(205,115,000)
Total liabilities, redeemable non-controlling interests and deficit	$ 119,594,000	$ 214,525,000

Schedule II - Valuation and Qualifying Accounts (Detail) - Valuation Allowances for Deferred Tax Assets [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Year	$ 452,740	$ 426,355
Charged (Credited) to Statement of Operation	(65,185)	26,385
Charged to Other Accounts - Liabilities and Equity	0	0
Deductions, Net	0	0
Balance at End of Year	$ 387,555	$ 452,740

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

Equity and Stock-based Compensation -At-the-Market Program-Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Feb. 24, 2025
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Sale proceeds from common stock		$ 30.0
ATM Program [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Issuance of common stock under ATM Program shares	0

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Senior Secured Term Loan Facilities

12 Months Ended

Dec. 31, 2025

Debt Disclosure [Abstract]

Senior Secured Term Loan Facilities

8. Senior Secured Term Loan Facilities

In April 2023, the Company entered into a financing agreement (“Financing Agreement”) with investment funds managed by MSTV, as lenders (the “Lenders”), and Wilmington Trust, National Association, as the administrative agent, providing for senior secured term loan facilities, and received $74.1 million, representing the Initial Term Loan of $75.0 million net of $0.9 million issuance costs.

The Initial Term Loan accrued interest at a fixed rate of 14.0% per annum, payable monthly in arrears. The Initial Term Loan would mature on May 8, 2026. The Initial Term Loan was subject to amortization payments. The Company was permitted to prepay the Initial Term Loan from time to time, in whole or in part, subject to payment of a make-whole amount equal to the unpaid principal amount of the portion of the Initial Term Loan being repaid or prepaid, plus accrued and unpaid interest of the portion of the Initial Term Loan being repaid or prepaid, plus an amount equal to the remaining scheduled interest payments due on such portion of the Initial Term Loan being repaid or prepaid as if such Initial Term Loan were to remain outstanding until the scheduled maturity date.

The initial issuance costs and the related transaction costs, totaling $3.7 million were amortized as interest expense using the effective interest method over the term of the Initial Term Loan and were reported on the balance sheet as a direct deduction from the amount of the Initial Term Loan. The effective annual interest rate of the Initial Term Loan was 16.13% for the year ended December 31, 2025. The Company recorded interest expense of $7.8 million and $11.7 million for the year ended December 31, 2025 and 2024, respectively, which were included in discontinued operations as the Company was required to repay the loan upon the closing of the divestiture FibroGen International.

On August 29, 2025, upon the above-mentioned Transaction close, the Company paid the Lenders a total of $80.9 million, including $75.0 million for paying off the senior secured term loan facilities, $0.4 million for outstanding interest and $5.5 million for related premium and fees. Accordingly, the Company recorded a loss on debt extinguishments of $6.6 million, including the $5.5 million of prepayment premium and fees and a $1.1 million amortization of issuance costs, for the year ended December 31, 2025.

The Company’s senior secured term loan facilities as of December 31, 2024 were as follows (in thousands):


	December 31, 2024
Principal of senior secured term loan facilities	$	75,000
Less: Unamortized issuance costs and transaction costs		(1,908	)
Senior secured term loan facilities, ending balance	$	73,092
Representing:
Senior secured term loan facilities, current	$	—
Senior secured term loan facilities, non-current	$	73,092

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

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+ Details

Equity method investment - Variable Interest Entity - Additional Information (Detail)	Aug. 29, 2025	Feb. 20, 2025
Beijing Kangda Yongfu Pharmaceutical Co., LTD [Member] \| Beijing Falikang Pharmaceutical Co Ltd \| AstraZenecaAB [Member]
Acquisition And Variable Interest Entity [Line Items]
Percentage of outstanding shares acquired	51.10%	51.10%

Pay vs Performance Disclosure - USD ($) $ in Thousands	12 Months Ended
Pay vs Performance Disclosure - USD ($) $ in Thousands	Dec. 31, 2025	Dec. 31, 2024
Pay vs Performance Disclosure
Net Income (Loss)	$ 183,452	$ (47,579)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

+ Details

Insider Trading Policies and Procedures	12 Months Ended
Insider Trading Policies and Procedures	Dec. 31, 2025
Insider Trading Policies and Procedures [Line Items]
Insider Trading Policies and Procedures Adopted	true

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2025

Accounting Policies [Abstract]

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The Company operates in one reportable segment — the development and commercialization of novel therapeutics to treat serious unmet medical needs.

Discontinued Operations

Reverse Stock Split

Liquidity and Going Concern

Foreign Currency Translation

The reporting currency of the Company and its subsidiaries is the U.S. dollar.

Use of Estimates

Concentration of Credit Risk

Other Risks and Uncertainties

Cash, Cash Equivalents

Investments

Trade accounts receivable

Credit losses – Available-for-sale debt securities

Inventories

Variable Interest Entity

Liability Related to Sale of Future Revenues

Revenue Recognition

Revenues under collaboration agreements

Drug product revenue

China Performance Obligation

The overall transaction price for FibroGen Beijing’s product sales to Falikang includes the following elements of consideration:

•

Non-refundable upfront license fees; development, regulatory, and commercial milestone payments based on the AstraZeneca China Agreement allocated to the China Performance Obligation;

•

Co-development billings resulting from the Company’s research and development efforts, which are reimbursable under the AstraZeneca China Agreement;

•

Interim profit/loss share between FibroGen Beijing and AstraZeneca from April 1, 2020 through December 31, 2020; and

•

Net transaction price from product sales to Falikang from January 1, 2021 onwards. The net transaction price includes the following elements:

Research and Development Expenses

Clinical Trial Accruals

Selling, General and Administrative Expenses

Restructuring Charge

Income Taxes

The Company includes interest and penalties related to unrecognized tax benefits within income tax expense in the Consolidated Statements of Operations.

Stock-Based Compensation

The Company believes that the fair value of stock options granted to non-employees is more reliably measured than the fair value of the services received.

Comprehensive Income (Loss)

Recently Adopted Accounting Guidance

Recently Issued Accounting Guidance Not Yet Adopted

Product Development Obligations - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2025 USD ($) DevelopmentObligation	Dec. 31, 2024 USD ($)
Debt Instrument [Line Items]
Number of product development obligations \| DevelopmentObligation	11
Percentage points deducted to reference rate to compute effective interest rate	1.00%
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	Bank Of Finland Interest Rate [Member]
Accrued product development costs excluding interest	$ 11.1	$ 9.8
Accrued Interest	$ 8.5	$ 7.2
Minimum [Member]
Debt Instrument [Line Items]
Interest rate on product development advances	3.00%

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Senior Secured Term Loan Facilities - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Apr. 30, 2023	Dec. 31, 2025	Dec. 31, 2024	Aug. 29, 2025
Debt Instrument [Line Items]
Term loan				$ 75,000
Paid to the Lenders				80,900
Outstanding interest amount		$ 400
Premium and fees		5,500		$ 5,500
Loss on debt extinguishments		6,583	$ 0
Amortization of issuance costs		1,100
FibroGen International [Member]
Debt Instrument [Line Items]
Interest expense		$ 7,800	$ 11,700
Debt Financing Agreement [Member]
Debt Instrument [Line Items]
Interest rate per annum	14.00%
Maturity date	May 08, 2026
Repayment description		The Initial Term Loan would mature on May 8, 2026. The Initial Term Loan was subject to amortization payments. The Company was permitted to prepay the Initial Term Loan from time to time, in whole or in part, subject to payment of a make-whole amount equal to the unpaid principal amount of the portion of the Initial Term Loan being repaid or prepaid, plus accrued and unpaid interest of the portion of the Initial Term Loan being repaid or prepaid, plus an amount equal to the remaining scheduled interest payments due on such portion of the Initial Term Loan being repaid or prepaid as if such Initial Term Loan were to remain outstanding until the scheduled maturity date.
Initial Term Loan [Member]
Debt Instrument [Line Items]
Interest rate per annum		16.13%
Issuance costs and related transaction costs, amortised		$ 3,700
Initial Term Loan [Member] \| Debt Financing Agreement [Member]
Debt Instrument [Line Items]
Term loan	$ 74,100
Initial term loan amount	75,000
Amount received	75,000
Issuance cost	$ 900

Collaboration Agreements, License Agreement and Revenues - Accounting for the Astellas Agreements - Additional Information 2 (Detail) - Astellas Agreement [Member]	12 Months Ended
	Dec. 31, 2025 USD ($)
Minimum [Member] \| Measurement Input Discount Rate [Member] \| Discounted Cash Flow [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied	17.5
Maximum [Member] \| Measurement Input Discount Rate [Member] \| Discounted Cash Flow [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Discount rate applied	20.0
Japan [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-contingent upfront payments received	$ 40,100,000
Variable consideration related to payments for milestones considered probable of being achieved	65,000,000.0
Variable consideration related to co-development billings	12,400,000
Provision for co-development services	0
Europe [Member]
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Non-contingent upfront payments received	320,000,000.0
Variable consideration related to payments for milestones considered probable of being achieved	365,000,000.0
Variable consideration related to co-development billings	$ 222,500,000

Summary of Significant Accounting Policies - Additional Information (Detail)			12 Months Ended
	Aug. 29, 2025 USD ($)	Jun. 16, 2025 shares	Dec. 31, 2025 USD ($) Segment shares	Dec. 31, 2024 USD ($) shares	Feb. 20, 2025
Accounting Policy [Line Items]
Number of operating segment \| Segment			1
Highly liquid investment maturity period			three months or less
Cash and cash equivalents			$ 47,872,000	$ 50,482,000
Long-term investments			20,160,000	0
Short-term investments			$ 41,106,000	0
Short term investments maturity			12 months
Long term Investments Maturity			12 months
Impairment of long-lived assets			$ 2,062,000	0
Accumulated deficit			(1,706,047,000)	(1,889,499,000)
Accumulated other comprehensive loss			$ (2,182,000)	$ (5,732,000)
Reverse stock split		1-for-25
Common Stock, Shares, Outstanding \| shares			4,047,000	4,037,000
Common stock, shares authorized \| shares		4,000,000	225,000,000	225,000,000
Reverse Stock Split [Member]
Accounting Policy [Line Items]
Common Stock, Shares, Outstanding \| shares		101,100,000
FibroGen International [Member]
Accounting Policy [Line Items]
Impairment of long-lived assets			$ 2,062,000	$ 0
Description of discontinued operations			On February 20, 2025, the Company entered into the Share Purchase Agreement with AstraZeneca Treasury Limited, pursuant to which the Company and its subsidiary FibroGen China Anemia Holdings, Ltd. agreed to sell all of the issued and outstanding equity interests of FibroGen International to AstraZeneca Treasury Limited. This sale includes all of the Company’s roxadustat assets in China, including FibroGen International’s subsidiary FibroGen Beijing and its 51.1% interest in Falikang. The Company determined that FibroGen International met the “held for sale” criteria and the “discontinued operations” criteria in accordance with FASB ASC 205, Presentation of Financial Statements, as of December 31, 2024. Accordingly, the operating results related to the FibroGen International are classified as discontinued operations, and have been reflected as discontinued operations in the consolidated statements of operations, while the related assets and liabilities were classified within the consolidated balance sheets as held for sale for all periods presented.
Discontinued operations name			FibroGen International
AstraZeneca Agreements [Member]
Accounting Policy [Line Items]
Profit share percent			50.00%
Share Purchase Agreement [Member]
Accounting Policy [Line Items]
Discontinued operation consideration	$ 220,400,000
Share Purchase Agreement [Member] \| FibroGen International [Member]
Accounting Policy [Line Items]
Discontinued operation consideration in cash	85,000,000
Discontinued operation consideration	220,400,000
Cash received for sale of discontinued operation	210,400,000
Outstanding interest and related premium and fees	80,900,000
Share Purchase Agreement [Member] \| Net Cash Held in China [Member]
Accounting Policy [Line Items]
Discontinued operation consideration in cash	$ 135,400,000
Beijing Kangda Yongfu Pharmaceutical Co., LTD [Member] \| Beijing Falikang Pharmaceutical Co Ltd \| AstraZenecaAB [Member]
Accounting Policy [Line Items]
Percentage of outstanding shares acquired	51.10%				51.10%

Liability Related to Sale of Future Revenues - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2022	Dec. 31, 2025	Dec. 31, 2024
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 6,440,000	$ 29,621,000
Interest paid		(450,000)	(5,653,000)
Drug Product Revenue [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 5,848,000	27,673,000
NovaQuest Capital Management [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Effective annual interest rate related to sale of future revenues		15.21%
NovaQuest Capital Management [Member] \| Payment Cap Date on or before December 31, 2028 [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum payment cap amount	$ 100,000,000
NovaQuest Capital Management [Member] \| Payment Cap Date on or after January 1, 2029 [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum payment cap amount	112,500,000
NovaQuest Capital Management [Member] \| Payment Cap Date after January 1, 2030 [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Maximum payment cap amount	125,000,000
Minimum [Member] \| NovaQuest Capital Management [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Prepayment amount of 2024 to 2030	80,000,000
Minimum [Member] \| NovaQuest Capital Management [Member] \| Payment Period One [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue interest payment	62,500,000
Minimum [Member] \| NovaQuest Capital Management [Member] \| Payment Period Two [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue interest payment	125,000,000
Maximum [Member] \| NovaQuest Capital Management [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Prepayment amount of 2024 to 2030	125,000,000
Product [Member] \| NovaQuest Capital Management [Member] \| Revenue Interest Financing Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue interest payment	10,000,000
Other Revenue - Contract Manufacturing [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		$ 592,000	1,948,000
Astellas Agreement [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Future revenue granted	$ 50,000,000
Percentage of revenue interest on global net sales	100.00%
Astellas Agreement [Member] \| Drug Product Revenue [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		5,800,000	2,000,000
Non-cash interest expense related to drug product revenue		8,400,000	7,900,000
Astellas Agreement [Member] \| Development Revenue [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenue		600,000	$ 1,400,000
Astellas Agreement [Member] \| Maximum [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue payment cap amount		$ 125,000,000
Astellas Agreement [Member] \| Product [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of revenue sold	22.50%
Astellas Agreement [Member] \| Milestone payments [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of revenue sold	10.00%
Astellas Agreement [Member] \| Milestone payments [Member] \| Payment Period One [Member]
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of revenue sold	20.00%

Income Taxes

12 Months Ended

Dec. 31, 2025

Income Tax Disclosure [Abstract]

Income Taxes

14. Income Taxes

The components of loss before income taxes are as follows (in thousands):


	Years Ended December 31,
	2025			2024
Domestic	$	(47,917	)	$	(142,819	)
Foreign		(10,377	)		(10,548	)
Loss before benefit for income taxes	$	(58,294	)	$	(153,367	)

The benefit for income taxes consists of the following (in thousands):


	Years Ended December 31,
	2025			2024
Current:
Federal	$	—		$	—
State		—			—
Foreign		(90	)		(269	)
Total current		(90	)		(269	)
Deferred:
Federal		—			—
State		—			—
Foreign		—			—
Total deferred		—			—
Benefit from income taxes	$	(90	)	$	(269	)


	Years Ended December 31, 2025
	Amount			%
Tax at statutory federal rate	$	(12,242	)		21.0	%
State tax, net of federal benefit		—			—	%
Foreign Tax Effects
Foreign Rate Differential – Cayman Islands		2,110			(3.6	)%
Foreign Rate Differential – Finland		76			(0.1	)%
Effect of cross-border tax laws
Global intangible low-taxed income		62,730			(107.6	)%
Other		(90	)		0.2	%
Tax credits		578			(1.0	)%
Change in valuation allowance		(59,391	)		101.9	%
Worldwide changes in unrecognized tax benefits		(180	)		0.3	%
Nondeductible items
Stock based compensation		5,591			(9.6	)%
Disallowed interest		448			(0.8	)%
Other		9			—	%
Other		271			(0.5	)%
Total	$	(90	)		0.2	%


	Years Ended December 31,
	2024
Tax at statutory federal rate		21.0	%
State tax		—	%
Stock-based compensation expense		(3.2	)%
Net operating losses not benefitted		(13.9	)%
Foreign net operating losses not benefitted		(1.4	)%
Deduction limitation on executive compensation		—	%
Global intangible low-taxed income		(2.1	)%
Other		(0.2	)%
Total		0.2	%

Significant components of the Company’s deferred tax assets are as follows (in thousands):


	December 31,
	2025			2024
Federal and state net operating loss carryforwards	$	173,195		$	206,365
Tax credit carryforwards		128,924			129,320
Foreign net operating loss carryforwards		112			120
Capitalized research and development expenses		64,293			83,329
Stock-based compensation		2,128			6,365
Lease obligations		12			22
Reserves and accruals		4,760			4,418
Deferred revenue		—			7,785
Intangible assets		14,135			15,036
Other		6			—
Subtotal		387,565			452,760
Less: Valuation allowance		(387,555	)		(452,740	)
Net deferred tax assets		10			20

Fixed assets		(10	)		(20	)
Non-deductible accrued expenses		—			—
Net deferred tax liabilities		(10	)		(20	)
Total net deferred tax assets	$	—		$	—

A valuation allowance has been provided to reduce the deferred tax assets to an amount management believes is more likely than not to be realized. Expected realization of the deferred tax assets for which a valuation allowance has not been recognized is based on upon the reversal of existing temporary differences and future taxable income.

The valuation allowance decreased by $65.2 million for the year ended December 31, 2025 and increased by $26.4 million for the years ended December 31, 2024. Due to uncertainty surrounding the realization of the favorable tax attributes in the future tax returns, the Company has established a valuation allowance against its otherwise recognizable net deferred tax assets.

The Company intends to continue maintaining a full valuation allowance on its deferred tax assets until there is sufficient evidence to support the reversal of all or some portion of this allowance.

At December 31, 2025, the Company had net operating loss carryforwards available to offset future taxable income of approximately $787.4 million and $145.4 million for federal and state tax purposes, respectively. $140.5 million of the federal net operating loss carryforwards will begin to expire in 2035 if not utilized, while the remainder can be carried forward indefinitely. The state net operating loss carryforward will begin to expire in 2031 if not utilized. The Company also had foreign net operating loss carryforwards of approximately $0.6 million, which expire between 2026 and 2034 if not utilized.

At December 31, 2025, the Company had approximately $153.8 million of federal and $53.7 million of California research and development tax credit and other tax credit carryforwards available to offset future taxable income. The federal credits begin to expire in 2026 and the California research credits have no expiration dates.

Federal and state tax laws impose substantial restrictions on the utilization of net operating loss and credit carryforwards in the event of an “ownership change” for tax purposes, as defined in Internal Revenue Code (“IRC”) Section 382. The Company performed an IRC Section 382 analysis and has determined that there were no ownership changes as of December 31, 2024. Thus, IRC Section 382 will not limit the use of the Company’s net operating loss and tax credit carryforwards. The Company will continue to monitor trading activities in its shares which could cause ownership change in future years.

On July 4, 2025, the One Big Beautiful Bill Act (“OBBBA”) was signed into law. The OBBBA makes permanent key elements of the Tax Cuts and Jobs Act, including restoring 100% bonus depreciation, eliminating the capitalization requirement for domestic research and experimentation, and changing the business interest expense limitation. ASC 740 requires the effects of changes in tax rates and laws on deferred tax balances to be recognized in the period in which the legislation was enacted in the third quarter of 2025. The provisions do not have a material impact on the Company’s financial statements.

Uncertain Tax Positions

The Company had unrecognized tax benefits of approximately $74.5 million as of December 31, 2025. Approximately $0.4 million of unrecognized tax benefits, if recognized, would affect the effective tax rate. The interest accrued as of December 31, 2025 and 2024 was immaterial.

A reconciliation of the beginning and ending amounts of unrecognized income tax benefits during the two years ended December 31, 2025 is as follows (in thousands):


	Federal and State
Balance as of December 31, 2023	$	70,710
Decrease due to prior positions		(156	)
Increase due to current year position		3,920
Foreign exchange rate differential		(153	)
Balance as of December 31, 2024		74,321
Decrease due to prior positions		(229	)
Increase due to current year position		372
Foreign exchange rate differential		—
Balance as of December 31, 2025	$	74,464

Unrecognized tax benefits may change during the next twelve months for items that arise in the ordinary course of business.

The Company classifies interest and penalties as a component of tax expense, if any.

The Company files income tax returns in the U.S. federal jurisdiction, U.S. state and other foreign jurisdictions. The U.S. federal and U.S. state taxing authorities may choose to audit tax returns for tax years beyond the statute of limitation period due to significant tax attribute carryforwards from prior years, making adjustments only to carryforward attributes. The foreign statute of limitation generally remains open from 2015 to 2025. The Company is not currently under audit in any tax jurisdiction. The Company did not have any cash payment for income taxes for the years ended December 31, 2025 and 2024.

- Definition

The entire disclosure for income tax.

+ References

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+ Details

Income Taxes - Components of Loss Before Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Components of Income Tax Expense (Benefit), Continuing Operations [Abstract]
Domestic	$ (47,917)	$ (142,819)
Foreign	(10,377)	(10,548)
Loss before provision for income taxes	$ (58,294)	$ (153,367)

- Definition

Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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+ Details

Equity and Stock-based Compensation - Employee Stock Purchase Plan - Additional information (Detail) - 2014 ESPP [Member] - shares	1 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2025	Dec. 31, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Purchase of common stock shares at discount	15.00%
Percentage of fair value exercise price grant date	85.00%
Number of common stock reserved for issuance	64,000
Common stock reserved for future issuance, Description		The Company has reserved 64,000 shares of its common stock for issuance under the 2014 ESPP.
Shares purchased by employees			14,163

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

+ Details

Income Taxes - Additional Information (Detail) - USD ($)		12 Months Ended
	Jul. 04, 2025	Dec. 31, 2025	Dec. 31, 2024
Income Taxes [Line Items]
Increase in valuation allowance		$ 65,200,000	$ 26,400,000
U.S. federal income tax rate		21.00%	21.00%
Federal and state net operating loss carryforwards		$ 173,195,000	$ 206,365,000
Foreign net operating loss carryforwards		112,000	120,000
Unrecognized tax benefits		74,500,000
Unrecognized tax benefits that would affect effective tax rate		$ 400,000
Foreign statute of limitation generally remains open in the year		2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025
Bonus depreciation percentage	100.00%
Cash payment for income taxes		$ 0	$ 0
Foreign net operating loss [Member]
Income Taxes [Line Items]
Foreign net operating loss carryforwards		$ 600,000
Foreign net operating loss [Member] \| Minimum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration year		2026
Foreign net operating loss [Member] \| Maximum [Member]
Income Taxes [Line Items]
Operating loss carryforwards expiration year		2034
Federal [Member]
Income Taxes [Line Items]
Federal and state net operating loss carryforwards		$ 787,400,000
Operating loss carryforwards expiration year		2035
Other tax credit carryforwards		$ 153,800,000
Other tax credit carryforwards expiration year		2026
Federal [Member] \| Expiration Year 2045 [Member]
Income Taxes [Line Items]
Federal and state net operating loss carryforwards		$ 140,500,000
State [Member]
Income Taxes [Line Items]
Federal and state net operating loss carryforwards		$ 145,400,000
Operating loss carryforwards expiration year		2031
State [Member] \| California [Member]
Income Taxes [Line Items]
Other tax credit carryforwards		$ 53,700,000

Equity and Stock-based Compensation - Common Stock - Additional information (Detail)	12 Months Ended
	Dec. 31, 2025
Equity [Abstract]
Common stock voting rights	one vote

Segment and Geographic Information

12 Months Ended

Dec. 31, 2025

Segment Reporting [Abstract]

Segment and Geographic Information

15. Segment and Geographic Information

The Company has one operating and reporting segment which primarily focuses on the development and commercialization of novel therapeutics to treat serious unmet medical needs. The Company has determined that the chief executive officer is the chief operating decision maker (“CODM”). The CODM assesses performance of the business, monitors budget versus actual results and manages and allocates resources to the Company’s operations using consolidated net income (loss) as the primary measurement. The CODM is regularly provided with entity-wide expense categories that are consistent with those found on the Company’s consolidated statements of operations. These significant segment expenses include cost of goods sold, research and development expenses, selling, general and administrative expenses, and restructuring charge. Other segment items that are presented on the consolidated statements of operations include interest expense, loss on debt extinguishments, interest income and other income (expense), net, and provision for (benefit from) income taxes. The measure of segment assets is reported on the balance sheet as total consolidated assets.

Supplemental enterprise-wide information is presented below.

Geographic Revenues

Geographic revenues, which are based on the region that revenue is generated, are as follows (in thousands):


	Years Ended December 31,
	2025		2024
United States	$	—	$	26,114
Europe		5,643		6,270
Japan		797		(2,854	)
China		—		91
Total revenue	$	6,440	$	29,621

Customer Concentration

The Company’s revenues have been generated from the following collaboration partners that individually accounted for 10% or more of the Company’s total revenue:


	Percentage of Revenue
	Years Ended December 31,
	2025			2024
AstraZeneca		—	%		88	%
Astellas		100	%		12	%

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

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+ Details

Net Loss Per Share (Tables)

12 Months Ended

Dec. 31, 2025

Earnings Per Share [Abstract]

Schedule of Weighted Impacts of Outstanding Anti-dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share


	Years Ended December 31,
	2025		2024
Employee stock options		465		538
RSUs, PRSUs and TSR awards		33		125
ESPP		—		18
		498		681

Equity and Stock-based Compensation - Subsidiary Stock and Non-Controlling Interests - Additional information (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024
Class Of Stock [Line Items]
Preferred stock, shares outstanding	0	0
Common stock, shares outstanding	4,047,000	4,037,000
Minority Shareholders [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	5,434,215	5,434,215
Series A [Member] \| Minority Shareholders [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	5,352,706	5,352,706
FibroGen Europe [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	42,619,022	42,619,022
Preferred stock redemption percentage	Redemption Right — If a Preferred Share can be redeemed by a majority shareholder owning more than ninety percent (90%) of the shares of FibroGen Europe in accordance with the provisions of the Finnish Limited Liability Companies Act, the minority holders of Preferred Shares have the right to request redemption of their shares.
Minimum percentage of shareholder's approval to call for redemption of preferred shares	90.00%
Preferred stock, voting rights	one vote
Conversion rights, shares issued upon conversion of each preferred share	1
FibroGen Europe [Member] \| Series A [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,700,845	1,700,845
FibroGen Europe [Member] \| Series B [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,875,000	1,875,000
FibroGen Europe [Member] \| Series C [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,599,503	1,599,503
FibroGen Europe [Member] \| Series D [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	1,520,141	1,520,141
FibroGen Europe [Member] \| Series E [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	459,565	459,565
FibroGen Europe [Member] \| Series F [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	5,714,332	5,714,332
FibroGen Europe [Member] \| Series G [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	9,927,500	9,927,500
FibroGen Europe [Member] \| Series H [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	19,822,136	19,822,136
FibroGen Cayman [Member]
Class Of Stock [Line Items]
Conversion rights, shares issued upon conversion of each preferred share	1
Reduction to nonredeemable noncontrolling interests	$ 7.5
Adjustments to additional paid in capital	2.1
FibroGen Cayman [Member] \| Minority Shareholders [Member]
Class Of Stock [Line Items]
Total dividends distributed	$ 5.4
FibroGen Cayman [Member] \| Series A [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	15,836,966	15,836,966
Preferred shares issued, price per share	$ 1.00
Cash dividend percentage	6.00%
Dividends per share	$ 1
Kyntra Bio [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	37,184,807	37,184,807
Common stock, shares outstanding	78,000,000	78,000,000
Kyntra Bio [Member] \| Common Shares [Member]
Class Of Stock [Line Items]
Common stock, shares outstanding	7,800,000	7,800,000
Kyntra Bio [Member] \| Series A [Member]
Class Of Stock [Line Items]
Preferred stock, shares outstanding	10,484,260	10,484,260

Collaboration Agreements, License Agreement and Revenues (Tables)

12 Months Ended

Dec. 31, 2025

Schedule of Drug Product Revenue

Drug product revenue from commercial-grade API or bulk drug product sales to Astellas and AstraZeneca was as follows for the years ended December 31, 2025 and 2024 (in thousands):


	Years Ended December 31,
	2025		2024
Astellas Japan Agreement	$	793	$	(2,872	)
Astellas Europe Agreement		5,055		4,874
AstraZeneca U.S./RoW Agreement		—		25,671
Drug product revenue, net	$	5,848	$	27,673

AstraZeneca Agreements [Member]

Roll-forward of Related Contract Liabilities


	Balance at December 31, 2024			Additions			Recognized as Revenue (Discontinued Operations)		Currency Translation and Other			Balance at December 31, 2025
AstraZeneca China performance obligation - deferred revenue	$	(132,097	)	$	(82,494	)	$	218,575	$	(3,984	)	$	—

Drug Product Revenue, Net [Member]

Roll-forward of Related Contract Liabilities

The following table includes a roll-forward of the above-mentioned deferred revenues that are considered as contract liabilities related to drug product (in thousands):


	Balance at December 31, 2024			Additions			Recognized as Revenue		Reclassified to Accrued Liability / Accounts Payable		Balance at December 31, 2025
Drug product revenue - deferred revenue:
Astellas Europe Agreement	$	(9,901	)	$	(2,210	)	$	4,778	$	1,764	$	(5,569	)