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STOCK-BASED COMPENSATION PLANS - Schedule of Assumptions Used in Black-Scholes Option Pricing Model (Details) - $ / shares	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Risk-free interest rate, minimum	3.61%	4.00%
Risk-free interest rate, maximum	4.00%	4.38%
Expected volatility, minimum	110.17%	111.97%
Expected volatility, maximum	119.09%	117.83%
Expected dividend yield	0.00%	0.00%
Fair value at grant date (in dollars per share)	$ 1.21	$ 1.92
Minimum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (years)	6 years 3 months	6 years 3 months
Maximum
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Expected term (years)	6 years 3 months	6 years 3 months

ADDITIONAL BALANCE SHEET DETAIL - Schedule of Other Long-Term Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Payables and Accruals [Abstract]
Long-term inventories	$ 56,060	$ 59,129
Other	514	552
Total other long-term assets	$ 56,574	$ 59,681

FAIR VALUE MEASUREMENTS

3 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

FAIR VALUE MEASUREMENTS

The tables below present certain assets and liabilities measured at fair value categorized by the level of input used in the valuation of each asset and liability (in thousands):


	March 31, 2026
	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	135,983	$	—	$	—	$	135,983
Long-term liability:
Warrant liability	$	—	$	2,524	$	—	$	2,524

	December 31, 2025
	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	172,689	$	—	$	—	$	172,689
Long-term liability:
Warrant liability	$	—	$	2,980	$	—	$	2,980

Cash and cash equivalents — Money market funds included within cash and cash equivalents are classified within Level 1 of the fair value hierarchy because they are valued using quoted market prices in active markets.

Warrant liability – The warrant liability is classified within Level 2 of the fair value hierarchy because it is valued using inputs which are observable either directly or indirectly. The fair value was calculated using the Black-Scholes option pricing model using the following key inputs: volatility, risk-free rate, dividend yield and expected term.

- 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 820
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+ Details

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

3 Months Ended

Mar. 31, 2026

Accounting Policies [Abstract]

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

The Company's significant accounting policies are disclosed in the audited consolidated financial statements for the year ended December 31, 2025, and notes thereto, which are included in the Company's Annual Report on Form 10-K, that was filed with the Securities and Exchange Commission, or SEC, on February 26, 2026, or the 2025 Form 10-K. Since the date of those financial statements, there have been no material changes to the Company's significant accounting policies.

In the opinion of management, all adjustments, consisting of normal recurring accruals and revisions of estimates, considered necessary for a fair presentation of the unaudited condensed consolidated financial statements have been included. Interim results for the three months ended March 31, 2026 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2026 or any other future period.

Basis of Presentation and Principles of Consolidation

The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the U.S., or GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB.

The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in the condensed consolidated financial statements herein.

Certain monetary amounts, percentages, and other figures included elsewhere in these unaudited condensed consolidated financial statements have been subject to rounding adjustments. Accordingly, figures shown as totals in certain tables may not be the arithmetic aggregation of the figures that precede them, and figures expressed as percentages in the text may not total 100% or, as applicable, when aggregated may not be the arithmetic aggregation of the percentages that precede them.

Use of Estimates

The preparation of financial statements in conformity with GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenue and expenses, classification of the expenses, assets and liabilities and the disclosure of contingent assets and liabilities as of and during the reported period. On an ongoing basis, management evaluates its estimates. Management bases its estimates and assumptions on historical experience when available and on various factors, including expected business and operational changes, sensitivity and volatility associated with the assumption that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of the assets and liabilities that are not readily apparent from other sources. In certain circumstances, management must apply significant judgment in this process. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management selects an amount that falls within that range of reasonable estimates. Although the Company regularly assesses these estimates, actual results could differ materially from these estimates. Changes in estimates are recorded in the period they become known.

Significant estimates and judgments reflected in these unaudited condensed consolidated financial statements include, but are not limited to: accrued expenses, a liability related to settlement royalties, revenues, including various rebates, returns and provisions related to product sales, inventories, classification of expenses between cost of goods sold, R&D and selling, general and administrative, long-term assets, including the Company's right-of-use assets and goodwill.

Cash, Cash Equivalents and Restricted Cash

In determining its cash, cash equivalents and restricted cash, the Company considers only those highly liquid investments, readily convertible to cash within 90 days from the date of purchase to be cash equivalents. As of March 31, 2026, cash and cash equivalents primarily included cash on hand and money market funds.

Restricted cash represents amounts required to secure the outstanding letter of credit in connection with the Company’s office and laboratory space in Cambridge, Massachusetts, or the Cambridge Lease. Restricted cash is included in "prepaid expenses and other current assets" in the consolidated balance sheet as of March 31, 2026 and December 31, 2025.

The following table reconciles cash, cash equivalents and restricted cash reported within the Company's consolidated balance sheets to the total amounts reported in the consolidated statements of cash flows:


Reconciliation of cash, cash equivalents and restricted cash (in thousands)	March 31, 2026		December 31, 2025
Cash and cash equivalents	$	162,644	$	184,844
Restricted cash	1,704		1,699
Total cash, cash equivalents and restricted cash	$	164,348	$	186,543

Concentration of Credit Risk

Cash, cash equivalents and accounts receivable are the only financial instruments that potentially subject the Company to concentrations of credit risk. The Company maintains cash accounts principally at two financial institutions in the U.S., which at times, may exceed the Federal Deposit Insurance Corporation's limits. The Company has not experienced any losses from cash balances in excess of the insurance limit. The Company's management does not believe the Company is exposed to significant credit risk at this time due to the financial condition of the financial institutions where its cash is held.

The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for receivables when collection becomes doubtful. Provisions are made based upon a specific review of all significant outstanding receivables and the overall quality and age of those invoices not specifically reviewed as well as historical payment patterns and existing economic factors. The Company believes that credit risks associated with its customers and collaboration partners are not

significant. The Company's allowance for credit losses was $2.9 million and $2.7 million as of March 31, 2026 and December 31, 2025, respectively.

The following table summarizes the activity related to the Company's allowance for credit losses (in thousands):


	Three Months Ended March 31,
	2026		2025
Beginning balance	$	2,691	$	1,212
Provision for bad debts	199		702

Ending balance	$	2,889	$	1,914

Manufacturing and Distribution Risk

The Company is dependent on third-party manufacturers, logistics companies and distributors to supply products for commercial activities associated with its products and product candidates, as applicable. In particular, the Company relies and expects to continue to rely on a small number of manufacturers to supply it with its requirements for the active pharmaceutical ingredients, or APIs, and formulated drugs related to the Company's product and product candidate activities. These activities, including the commercialization of Auryxia and Vafseo, could be adversely affected by a significant interruption in the supply of APIs and formulated drugs or distribution of finished product to the market.

New Accounting Pronouncements - Recently Adopted

In July 2025, the FASB issued ASU 2025-05, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets. ASU 2025-05 provides a practical expedient that all entities can use when estimating expected credit losses for current accounts receivable and current contract assets arising from transactions accounted for under ASC 606, Revenue from Contracts with Customers. Under this practical expedient, an entity is allowed to assume that the current conditions it has applied in determining credit loss allowances for current accounts receivable and current contract assets remain unchanged for the remaining life of those assets. ASU 2025-05 is effective for fiscal years beginning after December 15, 2025, and interim reporting periods in those years. Entities that elect the practical expedient and, if applicable, make the accounting policy election are required to apply the amendments prospectively. The adoption of this standard did not have a material effect on the Company’s consolidated financial statements and related disclosures.

New Accounting Pronouncements - Not Yet Adopted

In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, which requires new tabular disclosures in the notes to consolidated financial statements, disaggregating certain cost and expense categories within relevant captions on the consolidated statements of operations and comprehensive income (loss). The prescribed cost and expense categories requiring disaggregated disclosures include purchases of inventory, employee compensation, depreciation and intangible asset amortization, along with certain other expense disclosures already required by GAAP that would need to be integrated within the new tabular disaggregated expense disclosures. Additionally, the amendments require the disclosure of total selling expenses and an entity's definition of those expenses. ASU 2024-03 will be effective for annual reporting periods in fiscal years beginning after December 15, 2026, and interim reporting periods in fiscal years beginning after December 31, 2027. Early adoption is permitted and the amendments should be applied on a prospective basis. Retrospective application is permitted. The Company is currently reviewing the impact that the adoption of ASU 2024-03 may have on its expense disclosures in the notes to the consolidated financial statements.

In September 2025, the FASB issued ASU 2025-06, Intangibles - Goodwill and Other - Internal-Use Software, which removes all references to prescriptive and sequential software development stages (referred to as "project stages"). An entity will be required to start capitalizing software costs when (i) management has authorized and committed to funding the software project and (ii) it is probable that the project will be completed and the software will be used to perform the function intended (referred to as the "probable-to-complete recognition threshold"). ASU 2025-06 is effective for fiscal years beginning after December 15, 2027, and interim reporting periods within those annual periods. Early adoption is permitted as of the beginning of the annual reporting period. The Company is currently evaluating ASU 2025-06 and does not expect it to have a material effect on the Company’s consolidated financial statements.

LICENSE, COLLABORATION AND OTHER REVENUE - Schedule of Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accounts receivable
Contract asset:
Additions	$ 1,552	$ 1,545
Deductions	(2,282)	(1,989)
Accounts receivable
Contract asset:
Balance at Beginning of Period	2,391	2,010
Balance at End of Period	$ 1,661	$ 1,566

STOCK-BASED COMPENSATION PLANS - Schedule of Equity Plans (Details) - shares	Mar. 31, 2026	Dec. 31, 2025	Jun. 10, 2025
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of options outstanding (in shares)	21,871,531	18,152,258
Inducement Award Program
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of options outstanding (in shares)	858,775
Keryx Equity Plans
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Awards outstanding (in shares)	91,696	148,860
Additional awards available for grant (in shares)	0	0
Akebia Therapeutics, Inc. 2014 Incentive Plan, as amended (the 2014 Plan)
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Awards outstanding (in shares)	7,634,941	8,412,898
Additional awards available for grant (in shares)	0	0
Akebia Therapeutics, Inc. 2014 Incentive Plan, as amended (the 2014 Plan) \| Inducement Award Program
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of options outstanding (in shares)	956,825	1,050,525
Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan), as amended
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Awards outstanding (in shares)	23,224,380	15,913,729
Additional awards available for grant (in shares)	16,482,848	24,723,655
Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan), as amended \| Inducement Award Program
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Additional awards available for grant (in shares)			18,900,000
Number of options outstanding (in shares)	3,787,674	3,034,085

- 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

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-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(1)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (e)(2)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

NET INCOME (LOSS) PER SHARE - Schedule of Anti-Dilutive Securities Excluded (Details)	3 Months Ended
	Mar. 31, 2026 shares
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	33,066,402
Outstanding common stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	21,236,218
SARs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	635,313
Unvested RSUs
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	9,079,486
Warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share (in shares)	2,115,385

ADDITIONAL BALANCE SHEET DETAIL - Schedule of Accrued Expenses and other Current Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Payables and Accruals [Abstract]
Product revenue allowances excluding rebates	$ 8,371	$ 7,916
Product rebates	70,556	64,674
Product return provisions, current portion	1,972	2,375
Clinical trial costs	1,329	1,188
Compensation and related benefits	8,320	11,018
Operating lease liabilities	$ 2,127	$ 3,548
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total accrued expenses and other current liabilities	Total accrued expenses and other current liabilities
Royalties due to Panion & BF Biotech, Inc.	$ 2,944	$ 3,924
Professional fees	502	1,597
Accrued manufacturing costs	1,513	1,808
Liability related to sale of future royalties, current portion	1,401	1,664
Settlement royalties liability, current portion	15,397	12,516
Payments due to Q32	5,000	5,000
Other	5,630	4,488
Total accrued expenses and other current liabilities	$ 125,062	$ 121,716

LIABILITY RELATED TO SETTLEMENT ROYALTIES, WORKING CAPITAL FUND LIABILITY AND LIABILITY RELATED TO SALE OF FUTURE ROYALTIES

3 Months Ended

Mar. 31, 2026

Other Liabilities Disclosure [Abstract]

Vifor License Agreement

Summary of Agreement

On February 18, 2022, the Company entered into a Second Amended and Restated License Agreement, or the Vifor License Agreement, with CSL Vifor, which amended and restated the License Agreement dated as of May 12, 2017, or the Original License Agreement. The Vifor License Agreement granted CSL Vifor an exclusive license to sell Vafseo to Fresenius Medical Care North America and its affiliates, including Fresenius Kidney Care Group LLC, to certain third-party dialysis organizations approved by the Company, to independent dialysis organizations that are members of certain group purchasing organizations and certain non-retail specialty pharmacies, collectively, the Supply Group, in the U.S.

The Vifor License Agreement was structured as a profit share arrangement between the Company and CSL Vifor in which the Company would receive approximately 66% of the profit, net of certain pre-specified costs. In addition, CSL Vifor made an upfront payment to the Company of $25.0 million in February 2022 in connection with the amendment and restatement of the Vifor License Agreement, which was previously recorded as long-term deferred revenue in the consolidated balance sheets.

See Note 8, Liability Related to Settlement Royalties, Working Capital Fund Liability and Liability Related to Sale of Future Royalties, of the Notes to the Consolidated Financial Statements in the 2025 Form 10-K for a more detailed description of the Vifor License Agreement.

Investment Agreements

In connection with the Original License Agreement, in May 2017, the Company sold an aggregate of 3,571,429 shares of the Company’s common stock, or 2017 Shares, to CSL Vifor at a price per share of $14.00 for a total of $50.0 million.

In February 2022, in connection with the Vifor License Agreement, the Company sold an aggregate of 4,000,000 shares of its common stock, or 2022 Shares, to CSL Vifor at a price per share of $5.00 for a total of $20.0 million.

The $18.3 million, which represented the premiums over the closing stock price, or $4.7 million for the 2017 Shares and $13.6 million for the 2022 Shares, was previously recorded as long-term deferred revenue in the consolidated balance sheets as it represented consideration related to the Vifor License Agreement.

The 2017 Shares and 2022 Shares are subject to standstill agreements and are subject to voting agreements. The 2017 Shares and 2022 Shares have not been registered pursuant to the Securities Act of 1933, as amended, or the Securities Act, and were issued and sold in reliance upon the exemption from registration contained in Section 4(a)(2) of the Securities Act and Rule 506 promulgated thereunder as the transaction did not involve any public offering within the meaning of Section 4(a)(2) of the Securities Act.

Vifor Termination Agreement

On July 10, 2024, the Company and CSL Vifor entered into the Vifor Termination Agreement, pursuant to which the Company and CSL Vifor agreed, among other things, to terminate, effective immediately, the Vifor License Agreement.

Pursuant to the terms of the Vifor Termination Agreement, the Company will pay CSL Vifor decreasing quarterly tiered royalty payments ranging from a high single-digit percentage of the Company’s net sales of Vafseo up to $450.0 million to mid-single

digit percentage of the Company’s net sales of Vafseo above $450.0 million, in each case, in the U.S. during a calendar year, or the Settlement Royalty Payments. The Settlement Royalty Payments commenced upon the first sale of Vafseo by the Company, its affiliates or third-party licensees to a third party for use in the U.S., and will continue until the later of the (i) expiration of the last-to-expire valid claim listed in the FDA Orange Book that would be infringed by the making, using, selling or importing of Vafseo in the U.S. or (ii) the expiration of marketing or regulatory exclusivity for Vafseo in the U.S., or the Settlement Royalty Term. Beginning on July 1, 2027 and throughout the Settlement Royalty Term, the Company has the option to make a one-time payment to CSL Vifor, or the Royalty Buy-Down Option, upon which the Settlement Royalty Payments will be adjusted as of the date of exercise of the Royalty Buy-Down Option such that the Company will then only pay CSL Vifor quarterly royalty payments based on a mid-single digit percentage of the Company’s net sales of Vafseo up to $450.0 million in the U.S. during a calendar year in lieu of the above Settlement Royalty Payments. If the Company exercises the Royalty Buy-Down Option, the WCF Royalty Payments, as described below, will continue as described below.

The WCF Royalty Payments, the Settlement Royalty Payments and the Royalty Buy-Down Option are in consideration for the termination of the Vifor License Agreement and all obligations thereunder, and the covenants and agreements set forth in the Vifor Termination Agreement, including the settlement and release of all disputes and claims arising from the Vifor License Agreement.

As a result of the Vifor Termination Agreement, the Company reassessed whether the Vifor License Agreement still met the criteria to be considered a contract within the scope of ASC 606, Revenue from Contracts with Customers, and concluded that CSL Vifor no longer met the definition of a customer and, therefore, the arrangement should not be considered a revenue contract with a customer under ASC 606. The Company therefore determined that the consideration received from CSL Vifor of $43.3 million, comprised of the up-front payment of $25.0 million and the premiums paid by CSL Vifor for the 2017 Shares and 2022 Shares of $4.7 million and $13.6 million, respectively, should be classified as debt. Accordingly, the Company recorded the $43.3 million as a liability and is amortizing such amount using the effective interest method over the Settlement Royalty Term. The liability related to settlement royalties and the amortization are based on the Company’s current estimates of future royalties expected to be paid over the life of the arrangement. To the extent the Company’s estimates of future royalty payments are greater or less than previous estimates or the estimated timing of such payments is materially different than previous estimates, the Company will adjust the effective interest rate and recognize the related non-cash interest expense on a prospective basis. On a quarterly basis, the Company reassesses the expected royalty payments.

The annual effective interest rate as of March 31, 2026 was 21.2% which is reflected as interest expense in the unaudited condensed consolidated statements of operations and comprehensive income (loss). The Company recognized interest expense related to the settlement royalties liability of $3.6 million and $5.4 million for the three months ended March 31, 2026 and 2025, respectively. As of March 31, 2026 and December 31, 2025, the balances related to the settlement royalties liability were as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Current portion (included in accrued expenses and other current liabilities)	$	15,397	$	12,516
Long-term portion	54,842		54,750
Total settlement royalties liability	$	70,239	$	67,266

Working Capital Fund Liability (Previously Referred to as Refund Liability to Customer)

Pursuant to the Vifor License Agreement, CSL Vifor contributed $40.0 million to a working capital fund, or Working Capital Fund, established to partially fund the Company’s costs of purchasing Vafseo from its contract manufacturers.

The Working Capital Fund was considered a debt arrangement with zero coupon interest and the Company imputed interest on the Working Capital Fund liability at a rate of 15.0% per annum, which was determined based on certain factors, including the Company's credit rating, comparable securities yield and the expected repayment period. On March 18, 2022, when the $40.0 million was received from CSL Vifor, the Company recorded an initial discount on the Working Capital Fund liability and a corresponding deferred gain to the Working Capital Fund liability in the condensed consolidated balance sheet.

On May 3, 2024, the Company and CSL Vifor entered into Amendment #1 to the Vifor License Agreement, or the Amendment. Pursuant to the Amendment, and as modified by the Vifor Termination Agreement, the Company and CSL Vifor agreed to modify the method of repayment of the Working Capital Fund such that the Working Capital Fund will be repaid through quarterly tiered royalty payments ranging from 8% to 14% of the Company's net sales of Vafseo in the U.S., or the WCF Royalty Payments. The WCF Royalty Payments commenced on July 1, 2025, and will continue until the earlier of (i) the cumulative total of the WCF Royalty Payments equals $40.0 million, or (ii) May 31, 2028, or the WCF Royalty Term. The WCF Royalty Payments are subject to minimum true-up milestones of $10.0 million, $20.0 million and $40.0 million, or the WCF Royalty True-Up Payments, on each of May 31, 2026, May 31, 2027 and May 31, 2028, respectively, or the WCF Royalty True-Up Dates. If the cumulative total of the WCF Royalty Payments paid to CSL Vifor on any given WCF Royalty True-Up Date is less

than the respective WCF Royalty True-Up Payment, the Company will pay CSL Vifor a one-time payment equal to the difference between the WCF Royalty True-Up Payment and the cumulative total of the WCF Royalty Payments paid by the Company through such WCF Royalty True-Up Date. The Company determined that the terms of the Amendment are not substantially different than the terms of the Vifor License Agreement, and therefore the Amendment was accounted for as a modification. The Company concluded that the 15% discount rate remains appropriate. On a quarterly basis, the Company reassesses the effective rate and will adjust the rate prospectively, if needed.

The discount on the Working Capital Fund liability is being amortized to interest expense using the effective interest method over the WCF Royalty Term. The deferred gain is being amortized to interest income on a straight-line basis over the WCF Royalty Term. The amortization of the discount was $1.2 million and $1.1 million for the three months ended March 31, 2026 and 2025, respectively. The amortization of the deferred gain was $0.8 million and $1.0 million for the three months ended March 31, 2026 and 2025, respectively.

As of March 31, 2026 and December 31, 2025, the balances related to the Working Capital Fund liability were as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Current portion	$	23,445	$	17,356
Long-term portion	16,405		22,606
Total Working Capital Fund liability	$	39,850	$	39,962

Liability Related to Sale of Future Royalties

In February 2021, the Company entered into a royalty interest acquisition agreement, or the Royalty Agreement, with HealthCare Royalty Partners IV, L.P., or HCR, pursuant to which the Company sold to HCR its right to receive royalties and sales milestones for Vafseo in Japan and certain other Asian countries, such countries collectively, the TPC Territory, and such payments collectively the Royalty Interest Payments, in each case, payable to the Company under the Company's Collaboration Agreement, or the TPC Agreement, with Tanabe Pharma Corporation, formerly Mitsubishi Tanabe Pharma Corporation, or TPC. The Royalty Interest Payments are subject to an annual maximum “cap” of $13.0 million, after which the Company will receive 85% of the Royalty Interest Payments for the remainder of that year. The Royalty Interest Payments are also subject to an aggregate maximum “cap” of $150.0 million, after which the Royalty Interest Payments will revert back to the Company.

The Company retains the right to receive all potential future regulatory milestones for Vafseo under the TPC Agreement. The Royalty Agreement will terminate on the earlier of the date on which HCR has received (i) the last Royalty Interest Payment or (ii) payment by the Company of an amount equal to the Aggregate Cap minus the aggregate amount of all Royalty Interest Payments actually received by HCR.

At the transaction date, the Company recognized the proceeds received from HCR of $44.8 million (net of certain transaction expenses) as a liability and is amortizing it using the effective interest method over the life of the arrangement. The liability related to sale of future royalties and the debt amortization are based on the Company’s current estimates of future royalties expected to be paid over the life of the arrangement. To the extent the Company’s estimates of future royalty payments are greater or less than previous estimates or the estimated timing of such payments is materially different than previous estimates, the Company will adjust the effective interest rate and recognize related non-cash interest expense on a prospective basis. In the event the Company's estimates of future royalties are less than the proceeds from the sale of future royalties, the Company will not recognize related non-cash interest expense. On a quarterly basis, the Company assesses the expected royalty payments. The annual effective interest rate as of March 31, 2026 was 0% and, therefore the Company did not recognize any non-cash interest expense in the unaudited condensed consolidated statements of operations and comprehensive income (loss). As a result of the Company's ongoing involvement in the cash flows related to the royalties and sales milestones in the TPC Territory, the Company will continue to account for the royalties received as non-cash royalty revenue which is reflected within license, collaboration and other revenue in the unaudited condensed consolidated statements of operations and comprehensive income (loss). See Note 8, Liability Related to Settlement Royalties, Working Capital Fund Liability and Liability Related to Sale of Future Royalties, of the Notes to the Consolidated Financial Statements in the 2025 Form 10-K for a more detailed description of the Royalty Agreement.

The Company paid royalties to HCR of $0.5 million during each of the three months ended March 31, 2026 and 2025. As of March 31, 2026 and December 31, 2025 the balances were as follows (in thousands):


Liability related to sale of future royalties	March 31, 2026		December 31, 2025
Current portion (included in accrued expenses and other current liabilities)	$	1,401	$	1,664
Long-term portion	50,414		50,608
Total liability related to sale of future royalties	$	51,815	$	52,272

The Royalty Agreement requires the Company to take certain actions, including actions with respect to the Royalty Interest Payments, the TPC Agreement, and the Company's intellectual property. The Royalty Agreement also contains certain representations and warranties, covenants, indemnification obligations, events of default and other provisions that are customary for a royalty monetization transaction of this nature. In addition, the Company granted HCR a precautionary security interest in connection with the Royalty Interest Payments.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	3 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Mar. 31, 2026
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation and Principles of Consolidation The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the U.S., or GAAP. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the Accounting Standards Codification, or ASC, and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB.
Principles of Consolidation	The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries. All significant intercompany balances and transactions have been eliminated in the condensed consolidated financial statements herein.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP, requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, revenue and expenses, classification of the expenses, assets and liabilities and the disclosure of contingent assets and liabilities as of and during the reported period. On an ongoing basis, management evaluates its estimates. Management bases its estimates and assumptions on historical experience when available and on various factors, including expected business and operational changes, sensitivity and volatility associated with the assumption that it believes to be reasonable under the circumstances, the results of which form the basis for making judgments about the carrying values of the assets and liabilities that are not readily apparent from other sources. In certain circumstances, management must apply significant judgment in this process. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management selects an amount that falls within that range of reasonable estimates. Although the Company regularly assesses these estimates, actual results could differ materially from these estimates. Changes in estimates are recorded in the period they become known. Significant estimates and judgments reflected in these unaudited condensed consolidated financial statements include, but are not limited to: accrued expenses, a liability related to settlement royalties, revenues, including various rebates, returns and provisions related to product sales, inventories, classification of expenses between cost of goods sold, R&D and selling, general and administrative, long-term assets, including the Company's right-of-use assets and goodwill.
Cash, Cash Equivalents and Restricted Cash	Cash, Cash Equivalents and Restricted Cash In determining its cash, cash equivalents and restricted cash, the Company considers only those highly liquid investments, readily convertible to cash within 90 days from the date of purchase to be cash equivalents. As of March 31, 2026, cash and cash equivalents primarily included cash on hand and money market funds. Restricted cash represents amounts required to secure the outstanding letter of credit in connection with the Company’s office and laboratory space in Cambridge, Massachusetts, or the Cambridge Lease. Restricted cash is included in "prepaid expenses and other current assets" in the consolidated balance sheet as of March 31, 2026 and December 31, 2025.
Concentration of Credit Risk	Concentration of Credit Risk Cash, cash equivalents and accounts receivable are the only financial instruments that potentially subject the Company to concentrations of credit risk. The Company maintains cash accounts principally at two financial institutions in the U.S., which at times, may exceed the Federal Deposit Insurance Corporation's limits. The Company has not experienced any losses from cash balances in excess of the insurance limit. The Company's management does not believe the Company is exposed to significant credit risk at this time due to the financial condition of the financial institutions where its cash is held. The Company makes judgments as to its ability to collect outstanding receivables and provides an allowance for receivables when collection becomes doubtful. Provisions are made based upon a specific review of all significant outstanding receivables and the overall quality and age of those invoices not specifically reviewed as well as historical payment patterns and existing economic factors. The Company believes that credit risks associated with its customers and collaboration partners are not significant.
New Accounting Pronouncements - Recently Adopted/Not Yet Adopted	New Accounting Pronouncements - Recently Adopted In July 2025, the FASB issued ASU 2025-05, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses for Accounts Receivable and Contract Assets. ASU 2025-05 provides a practical expedient that all entities can use when estimating expected credit losses for current accounts receivable and current contract assets arising from transactions accounted for under ASC 606, Revenue from Contracts with Customers. Under this practical expedient, an entity is allowed to assume that the current conditions it has applied in determining credit loss allowances for current accounts receivable and current contract assets remain unchanged for the remaining life of those assets. ASU 2025-05 is effective for fiscal years beginning after December 15, 2025, and interim reporting periods in those years. Entities that elect the practical expedient and, if applicable, make the accounting policy election are required to apply the amendments prospectively. The adoption of this standard did not have a material effect on the Company’s consolidated financial statements and related disclosures. New Accounting Pronouncements - Not Yet Adopted In November 2024, the FASB issued ASU 2024-03, Income Statement—Reporting Comprehensive Income—Expense Disaggregation Disclosures (Subtopic 220-40): Disaggregation of Income Statement Expenses, which requires new tabular disclosures in the notes to consolidated financial statements, disaggregating certain cost and expense categories within relevant captions on the consolidated statements of operations and comprehensive income (loss). The prescribed cost and expense categories requiring disaggregated disclosures include purchases of inventory, employee compensation, depreciation and intangible asset amortization, along with certain other expense disclosures already required by GAAP that would need to be integrated within the new tabular disaggregated expense disclosures. Additionally, the amendments require the disclosure of total selling expenses and an entity's definition of those expenses. ASU 2024-03 will be effective for annual reporting periods in fiscal years beginning after December 15, 2026, and interim reporting periods in fiscal years beginning after December 31, 2027. Early adoption is permitted and the amendments should be applied on a prospective basis. Retrospective application is permitted. The Company is currently reviewing the impact that the adoption of ASU 2024-03 may have on its expense disclosures in the notes to the consolidated financial statements. In September 2025, the FASB issued ASU 2025-06, Intangibles - Goodwill and Other - Internal-Use Software, which removes all references to prescriptive and sequential software development stages (referred to as "project stages"). An entity will be required to start capitalizing software costs when (i) management has authorized and committed to funding the software project and (ii) it is probable that the project will be completed and the software will be used to perform the function intended (referred to as the "probable-to-complete recognition threshold"). ASU 2025-06 is effective for fiscal years beginning after December 15, 2027, and interim reporting periods within those annual periods. Early adoption is permitted as of the beginning of the annual reporting period. The Company is currently evaluating ASU 2025-06 and does not expect it to have a material effect on the Company’s consolidated financial statements.

- Definition

Disclosure of accounting policy for the use of estimates in the preparation of financial statements in conformity with generally accepted accounting principles.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478671/942-235-S50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 942
-SubTopic 235
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-05(b)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477314/942-235-S99-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 12
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-12

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
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-Name Accounting Standards Codification
-Section 50
-Paragraph 9
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-9

Reference 5: http://www.xbrl.org/2003/role/exampleRef
-Topic 275
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-Name Accounting Standards Codification
-Section 55
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482836/275-10-55-6

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
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-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-6

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Topic 275
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-Name Accounting Standards Codification
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-URI https://asc.fasb.org/1943274/2147482861/275-10-50-4

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
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-Paragraph 1
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-Publisher FASB
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (c)
-SubTopic 10
-Topic 275
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-1

+ Details

INDEBTEDNESS (Tables)

3 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

Schedule of Future Principal Payments on the Term Loans

As of March 31, 2026, future principal payments under the BlackRock Credit Agreement are as follows (in thousands):


Years ended December 31,	Principal Payments
2026	$	—
2027	50,558
2028	1,881
Total before unamortized discount and issuance costs	$	52,439
Less: unamortized discount and issuance costs	(3,549)
Total term loans	$	48,890

INVENTORIES - Schedule of Components of Inventory (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Inventory [Line Items]
Inventories, current	$ 12,996	$ 15,610
Raw materials	50	50
Inventories, long-term	56,060	59,129
Total inventories	69,056	74,739
Inventories
Inventory [Line Items]
Work-in-process	7,890	12,651
Finished goods	5,106	2,959
Other Noncurrent Assets
Inventory [Line Items]
Work-in-process	54,418	57,290
Finished goods	$ 1,592	$ 1,789

STOCK-BASED COMPENSATION PLANS (Tables)

3 Months Ended

Mar. 31, 2026

Equity [Abstract]

Schedule of Equity Incentive Plans

The following table contains information about the Company's equity incentive plans:


			March 31, 2026		December 31, 2025
Title of Plan	Group Eligible	Type of Award Granted (or to be Granted)	Awards Outstanding	Additional Awards Available for Grant	Awards Outstanding	Additional Awards Available for Grant
Keryx Equity Plans(1)(2)	Employees, directors and consultants	Stock options and restricted stock units (RSUs)	91,696	—	148,860	—
Akebia Therapeutics, Inc. 2014 Incentive Plan, as amended (2) (3) (the 2014 Plan)	Employees, directors, consultants and advisors	Stock options, RSUs, stock appreciation rights (SARs) and performance awards	7,634,941	—	8,412,898	—
Akebia Therapeutics, Inc. 2023 Stock Incentive Plan, as amended(3) (4) (the 2023 Plan) (replaced 2014 Plan)	Employees, officers, directors, consultants and advisors	Stock options, SARs, restricted stock, unrestricted stock, RSUs, performance awards, other share-based awards and dividend equivalents	23,224,380	16,482,848	15,913,729	24,723,655

(1) The Keryx Equity Plans consist of the Keryx Biopharmaceuticals, Inc. 1999 Share Option Plan, as amended, the 2004 Long-Term Incentive Plan, as amended, the Keryx Biopharmaceuticals, Inc. 2007 Incentive Plan, the Keryx Biopharmaceuticals Inc. Amended and Restated 2013 Incentive Plan and the Keryx Biopharmaceuticals, Inc. 2018 Equity Incentive Plan.

(2) New awards are no longer being granted under these plans.

(3) This table includes the following inducement awards that are subject to the terms and conditions of the applicable plan but were granted as inducement awards consistent with Nasdaq Listing Rule 5635(c)(4) and not under the applicable plan: 956,825 options included as outstanding under the 2014 Plan in the table and 3,787,674 options included as outstanding under the 2023 Plan in the table as of March 31, 2026 and 1,050,525 options included as outstanding under the 2014 Plan and 3,034,085 options included as outstanding under the 2023 Plan in the table as of December 31, 2025.

(4) On June 10, 2025, the 2023 Plan was amended to increase the number of shares of common stock available for issuance thereunder by 18,900,000 shares.

Schedule of Stock Option Activity

The combined stock option activity for the three months ended March 31, 2026, is as follows:


	Stock Options	Weighted Average Exercise Price		Weighted-Average Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2025	18,152,258	$	2.85	6.97 years	$	3,690
Granted	4,869,975	$	1.41	—	—
Exercised	(28,424)	$	0.71	—	—
Expired	(593,220)	$	5.77	—	—
Canceled and forfeited	(529,058)	$	1.78	—	—
Outstanding at March 31, 2026	21,871,531	$	2.48	7.59 years	$	2,691
Exercisable at March 31, 2026	10,605,986	$	3.23	6.04 years	$	2,059

Schedule of RSU and PSU Activity

RSU and PSU activity is as follows:


	2014 Plan			2023 Plan
	Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares	Weighted Average Grant Date Fair Value
Unvested as of December 31, 2025	330,622	$	0.63	5,992,607	$	2.09
Granted	—	$	—	5,426,300	$	1.41
Vested	(330,622)	$	0.63	(2,018,204)	$	2.01
Forfeited and canceled	—	$	—	(321,217)	$	1.80
Unvested as of March 31, 2026	—	$	—	9,079,486	$	1.71

Schedule of Assumptions Used in Black-Scholes Option Pricing Model

The weighted-average assumptions used in calculating the fair values of the rights to acquire stock under the 2023 Plan, the 2014 Plan and inducement awards were as follows:


	Three Months Ended March 31,
Common Stock Options	2026				2025
Risk-free interest rate	3.61	%	-	4.00%	4.00	%	-	4.38%
Expected volatility	110.17	%	-	119.09%	111.97	%	-	117.83%
Expected term (years)	6.25 years		-	6.25 years	6.25 years		-	6.25 years
Expected dividend yield	—%				—%
Weighted average grant date fair value	$1.21				$1.92

Schedule of Stock-Based Compensation Expense in Consolidated Statement of Operations and Comprehensive Loss

The Company has classified stock-based compensation in its unaudited condensed consolidated statements of operations and comprehensive income (loss) as follows (in thousands):


	Three Months Ended March 31,
	2026		2025
Cost of goods sold	$	197	$	139
Research and development	1,056		467
Selling, general and administrative	2,415		1,581

Total stock-based compensation	$	3,668	$	2,187

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ in Thousands	Mar. 31, 2026 USD ($) financial_institution	Dec. 31, 2025 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2024 USD ($)
Accounting Policies [Abstract]
Number of financial institutions maintaining cash \| financial_institution	2
Allowance for credit loss \| $	$ 2,889	$ 2,691	$ 1,914	$ 1,212

SEGMENT INFORMATION (Tables)

3 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

Schedule of Segment Financial Information

The following table presents information about reported segment revenues, segment profit and significant segment expenses for the three months ended March 31, 2026 and 2025:


	Three Months Ended March 31,
	2026		2025
Revenues	$	53,544	$	57,336
Less:
Direct cost of product and other revenue	10,033		5,059
Panion royalty	2,257		2,566


Research and development	14,807		9,754
Selling, general and administrative	30,436		25,742
License	707		701

Income (loss) from operations	(4,696)		13,514

Other income (expense)
Interest expense	(4,691)		(7,770)
Other income	3		213
Change in fair value of warrant liability	456		155


Income (loss) before income taxes	(8,928)		6,112
Income tax expense	(126)		—
Net income (loss)	$	(9,054)	$	6,112

NET INCOME (LOSS) PER SHARE (Tables)

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

Schedule of Earnings Per Share, Basic and Diluted

The following summarizes the calculation of net income (loss) per share:


	Three Months Ended March 31,
(Dollars in thousands, except per share amounts)	2026		2025
Numerator
Net income (loss)	$	(9,054)	$	6,112

Denominator
Denominator for basic net income (loss) per share - weighted average outstanding shares of common stock	267,046,755		235,497,720
Dilutive effect of common stock options and SARs	—		2,490,510
Dilutive effect of RSUs	—		2,230,747
Dilutive effect of warrants	—		1,382,510
Dilutive effect of ESPP	—		1,366
Denominator for diluted net income (loss) per share - weighted average outstanding shares of common stock and assumed conversions	267,046,755		241,602,853
Basic net income (loss) per share	$	(0.03)	$	0.03
Diluted net income (loss) per share	$	(0.03)	$	0.03

Schedule of Anti-Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share

The shares in the table below were excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, due to their anti-dilutive effect:


			Three Months Ended March 31, 2026
Outstanding common stock options			21,236,218
SARs			635,313
Unvested RSUs			9,079,486

Warrants			2,115,385
Total			33,066,402

SEGMENT INFORMATION - Schedule of Segment Financial Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Segment Reporting Information [Line Items]
Total revenues	$ 53,544	$ 57,336
Less:
Research and development	14,807	9,754
Selling, general and administrative	30,436	25,742
License	707	701
Income (loss) from operations	(4,696)	13,514
Other income (expense)
Interest expense	(4,691)	(7,770)
Other income	3	213
Change in fair value of warrant liability	456	155
Income (loss) before income taxes	(8,928)	6,112
Income tax expense	(126)	0
Net income (loss)	(9,054)	6,112
Reportable Segment
Segment Reporting Information [Line Items]
Total revenues	53,544	57,336
Less:
Direct cost of product and other revenue	10,033	5,059
Panion royalty	2,257	2,566
Research and development	14,807	9,754
Selling, general and administrative	30,436	25,742
License	707	701
Income (loss) from operations	(4,696)	13,514
Other income (expense)
Interest expense	(4,691)	(7,770)
Other income	3	213
Change in fair value of warrant liability	456	155
Income (loss) before income taxes	(8,928)	6,112
Income tax expense	(126)	0
Net income (loss)	$ (9,054)	$ 6,112

INVENTORIES

3 Months Ended

Mar. 31, 2026

Inventory Disclosure [Abstract]

INVENTORIES

Inventories consists of the following (in thousands):


	March 31, 2026		December 31, 2025
Inventories, current:
Work-in-process	$	7,890	$	12,651
Finished goods	5,106		2,959
Inventories, current	$	12,996	$	15,610
Long-term inventories included in other long-term assets:
Raw materials	50		50
Work-in-process	54,418		57,290
Finished goods	1,592		1,789
Inventories, long-term	$	56,060	$	59,129
Total inventories	$	69,056	$	74,739

Inventory written down as a result of excess, obsolescence, scrap or other reasons charged to cost of product and other revenue in the unaudited condensed consolidated statements of operations and comprehensive income (loss) was $3.2 million and $0.2 million during the three months ended March 31, 2026 and 2025, respectively.

LEASES (Tables)

3 Months Ended

Mar. 31, 2026

Leases [Abstract]

Schedule of Future Commitments under Non-Cancelable Leases

Future commitments under the non-cancelable Cambridge Lease are as follows (in thousands):


	Operating Lease Commitments

2026	2,142
Total lease commitments	$	2,142
Less: present value adjustment	(15)
Current operating lease liabilities	$	2,127

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Allowance for Credit Losses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accounts Receivable, Allowance for Credit Loss [Roll Forward]
Beginning balance	$ 2,691	$ 1,212
Provision for bad debts	199	702
Ending balance	$ 2,889	$ 1,914

ADDITIONAL BALANCE SHEET DETAIL - Schedule of Prepaids and Other Current Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Payables and Accruals [Abstract]
Restricted cash	$ 1,704	$ 1,699
Other	3,601	3,771
Total prepaid expenses and other current assets	$ 5,305	$ 5,470

ADDITIONAL BALANCE SHEET DETAIL (Tables)

3 Months Ended

Mar. 31, 2026

Payables and Accruals [Abstract]

Schedule of Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets are as follows (in thousands):


Description	March 31, 2026		December 31, 2025

Restricted cash	1,704		1,699
Other	3,601		3,771
Total prepaid expenses and other current assets	$	5,305	$	5,470

Schedule of Other Long-Term Assets

Other long-term assets are as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Long-term inventories	$	56,060	$	59,129

Other	514		552
Total other long-term assets	$	56,574	$	59,681

Schedule of Components of Accrued Expenses and Other Current Liabilities

Accrued expenses and other current liabilities are as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Product revenue allowances excluding rebates	$	8,371	$	7,916
Product rebates	70,556		64,674
Product return provisions, current portion	1,972		2,375
Clinical trial costs	1,329		1,188
Compensation and related benefits	8,320		11,018
Operating lease liabilities	2,127		3,548
Royalties due to Panion & BF Biotech, Inc.	2,944		3,924
Professional fees	502		1,597
Accrued manufacturing costs	1,513		1,808

Liability related to sale of future royalties, current portion	1,401		1,664
Settlement royalties liability, current portion	15,397		12,516
Payments due to Q32	5,000		5,000
Other	5,630		4,488
Total accrued expenses and other current liabilities	$	125,062	$	121,716

LICENSE, COLLABORATION AND OTHER REVENUE - Schedule of Revenues Recognized From License, Collaboration and Other Significant Agreements (Details) - USD ($) $ in Thousands		3 Months Ended
	Dec. 11, 2015	Mar. 31, 2026	Mar. 31, 2025
License Collaboration And Other Revenue [Abstract]
Total revenues		$ 53,544	$ 57,336
License, collaboration and other revenue
License Collaboration And Other Revenue [Abstract]
Total revenues		1,552	1,545
Medice \| License, collaboration and other revenue
License Collaboration And Other Revenue [Abstract]
Total revenues		32	7
TPC
License Collaboration And Other Revenue [Abstract]
Total revenues	$ 9,000
TPC \| License, collaboration and other revenue
License Collaboration And Other Revenue [Abstract]
Total revenues		341	369
JT and Torii \| License, collaboration and other revenue
License Collaboration And Other Revenue [Abstract]
Total revenues		$ 1,179	$ 1,169

- 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

LICENSE, COLLABORATION AND OTHER REVENUE - MTPC Collaboration Agreement - Narrative (Details) $ in Thousands		3 Months Ended
	Dec. 11, 2015 USD ($) performance_obligation	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues		$ 53,544	$ 57,336
Accounts receivable, net		62,536		$ 47,031
Payables		8,386		$ 21,185
Revenue recognized		0	0
Tanabe Pharma Corporation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues	$ 9,000
Tanabe Pharma Corporation \| Royalty payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues		300	400
Tanabe Pharma Corporation \| Regulatory Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone revenue	$ 25,000	25,000
Tanabe Pharma Corporation \| Development And Commercialize Collaboration Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of performance obligations \| performance_obligation	2
Tanabe Pharma Corporation \| Development And Commercialize Research And License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment received	$ 20,000
Cost of research services	20,500
Milestone revenue	$ 10,000
Deferred revenue		0
Accounts receivable, net		0
Payables		0
Contract asset		300
Tanabe Pharma Corporation \| Mitsubishi Tanabe Pharma Corporation Supply Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		0
Accounts receivable, net		0
Payables		0
Revenue recognized		$ 0	$ 0

Insider Trading Arrangements	3 Months Ended
Insider Trading Arrangements	Mar. 31, 2026
Trading Arrangements, by Individual
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

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Schedule of Reconciliations (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Mar. 31, 2025	Dec. 31, 2024
Accounting Policies [Abstract]
Cash and cash equivalents	$ 162,644	$ 184,844
Restricted cash	1,704	1,699
Total cash, cash equivalents and restricted cash	$ 164,348	$ 186,543	$ 115,059	$ 53,550

LICENSE, COLLABORATION AND OTHER REVENUE - Schedule of Revenue Recognized Resulting from Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Revenue Recognized in the Period:
Deferred revenue — beginning of the period	$ 0	$ 0

INDEBTEDNESS - Schedule of Future Principal Payments on the Term Loans (Details) $ in Thousands	Mar. 31, 2026 USD ($)
Debt Disclosure [Abstract]
2026	$ 0
2027	50,558
2028	1,881
Total before unamortized discount and issuance costs	52,439
Less: unamortized discount and issuance costs	(3,549)
Total term loans	$ 48,890

- Definition

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References + Details

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

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+ Details

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION

3 Months Ended

Mar. 31, 2026

Revenue from Contract with Customer [Abstract]

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION

The following table presents net product revenue for Vafseo and Auryxia (in thousands):


	Three Months Ended March 31,
Product	2026		2025
Vafseo	$	15,802	$	12,034
Auryxia(1)	36,190		43,757
Total product revenues	$	51,992	$	55,791

(1) Includes the authorized generic version of Auryxia sold and distributed by the Company's authorized generic distribution partner, Mylan Therapeutics, Inc., or AG Distributor, during the three months ended March 31, 2026 and 2025.

The following tables present changes in the Company’s contract assets and liabilities related to the Company's sales to its AG Distributor (in thousands):


	Three Months Ended March 31, 2026
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable	$	194	$	—	$	—	$	194
Contract liabilities:
Deferred revenue	$	2,681	$	4,826	$	(3,011)	$	4,496

	Three Months Ended March 31, 2025
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable	$	—	$	1,241	$	—	$	1,241
Contract liabilities:
Deferred revenue	$	—	$	1,241	$	—	$	1,241

The Company recognized the following revenues related to the Company's sales to its AG Distributor as a result of changes in the contract asset and contract liability balances in the respective periods (in thousands):


	Three Months Ended March 31,
Revenue Recognized in the Period:	2026		2025
Deferred revenue — beginning of the period	$	3,011	$	—

Product revenue allowance and provision categories were as follows:


(in thousands)	Chargebacks and Discounts		Rebates, Fees and Other Deductions		Product Returns		Total
Balance at December 31, 2025	$	1,153	$	72,589	$	3,351	$	77,093
Current provisions related to sales in current year	1,458		20,270		159		21,887
Adjustments related to prior year sales	26		(1,483)		—		(1,457)
Credits/payments made	(1,639)		(12,449)		(872)		(14,960)
Balance at March 31, 2026	$	998	$	78,927	$	2,638	$	82,563

(in thousands)	Chargebacks and Discounts		Rebates, Fees and Other Deductions		Product Returns		Total
Balance at December 31, 2024	$	1,436	$	15,726	$	6,442	$	23,604
Current provisions related to sales in current year	380		20,147		387		20,914
Adjustments related to prior year sales	69		400		(164)		305
Credits/payments made	(1,389)		(8,822)		(145)		(10,356)
Balance at March 31, 2025	$	496	$	27,451	$	6,520	$	34,467

Chargebacks, discounts and estimated product returns are recorded as a reduction of revenue in the period the related product revenue is recognized in the unaudited condensed consolidated statements of operations and comprehensive income (loss). Chargebacks are recorded as a reduction to accounts receivable while discounts, rebates, fees and other deductions are recorded with a corresponding increase to accrued expenses and other current liabilities or accounts payable on the condensed consolidated balance sheets. Estimated product returns on product sales that are not expected to be returned within one year are recorded as other long-term liabilities in the unaudited condensed consolidated balance sheets.

Accounts receivable, net related to product sales, was approximately $60.9 million and $44.4 million as of March 31, 2026 and December 31, 2025, respectively.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

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+ Details

INVENTORIES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
INVENTORIES - Narrative (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Mar. 31, 2025
Inventory [Line Items]
Write-down of inventory	$ 3,216	$ 163
Auryxia Drug Substance
Inventory [Line Items]
Write-down of inventory	$ 3,200	$ 200

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION - Schedule of Revenues Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Deferred revenue — beginning of the period	$ 0	$ 0
Sales to AG Distributor
Disaggregation of Revenue [Line Items]
Deferred revenue — beginning of the period	$ 3,011	$ 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.

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+ Details

LIABILITY RELATED TO SETTLEMENT ROYALTIES, WORKING CAPITAL FUND LIABILITY AND LIABILITY RELATED TO SALE OF FUTURE ROYALTIES - Schedule of Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025	Feb. 25, 2021
Other Liabilities Disclosure [Abstract]
Current portion (included in accrued expenses and other current liabilities)	$ 1,401	$ 1,664
Long-term portion	50,414	50,608	$ 44,800
Total liability related to sale of future royalties	$ 51,815	$ 52,272

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION - Schedule of Product Revenues (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Disaggregation of Revenue [Line Items]
Total revenues	$ 53,544	$ 57,336
Product revenue, net
Disaggregation of Revenue [Line Items]
Total revenues	51,992	55,791
Vafseo
Disaggregation of Revenue [Line Items]
Total revenues	15,802	12,034
Auryxia
Disaggregation of Revenue [Line Items]
Total revenues	$ 36,190	$ 43,757

- 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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LIABILITY RELATED TO SETTLEMENT ROYALTIES, WORKING CAPITAL FUND LIABILITY AND LIABILITY RELATED TO SALE OF FUTURE ROYALTIES - Schedule of Liability Related to Settlement Royalties (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Other Liabilities Disclosure [Abstract]
Current portion (included in accrued expenses and other current liabilities)	$ 15,397	$ 12,516
Long-term portion	54,842	54,750
Total settlement royalties liability	$ 70,239	$ 67,266

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2026
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Manufacturing and Unconditional Purchase Commitment Agreements Siegfried Manufacturing The Company's contractual obligations include a commercial supply agreement with Siegfried Evionnaz SA, or Siegfried, to supply commercial drug substance for Auryxia. The Company and Siegfried entered into a Master Manufacturing Services and Supply Agreement, most recently amended in February 2023, or the Siegfried Agreement, under which the Company has agreed to purchase a minimum quantity of drug substance of Auryxia, annually at a predetermined price. As of March 31, 2026, the Company had no minimum commitments with Siegfried. The term of the Siegfried Agreement expires on December 31, 2026. The Siegfried Agreement provides the Company and Siegfried with certain early termination rights. The Company regularly reviews its estimate of the excess firm purchase commitment liability which relates to the amount of minimum purchase commitments under the Siegfried Agreement that exceeded the then current forecast, including review of assumptions of expected future demand and expiry of inventory. The Company did not have an excess firm purchase commitment liability as of March 31, 2026. The excess firm purchase commitment liability recorded in other long-term liabilities was $0.8 million as of December 31, 2025. Patheon Manufacturing In March 2020, the Company entered into a Supply Agreement with Patheon Inc., or Patheon, or the Patheon Agreement, under which Patheon agreed to manufacture Vafseo drug product for commercial use under a volume-based pricing structure through June 30, 2023, with the agreement renewing annually unless either party gives the other party eighteen months' prior written notice. Under the Patheon Agreement, the Company agreed to purchase from Patheon a certain percentage of the estimated global demand for Vafseo drug product based on certain quarterly and annual forecasts provided by the Company. As of March 31, 2026, the Company has committed to purchase $1.1 million of Vafseo drug product from Patheon through the end of 2026, however, as estimated global demand fluctuates, the Company may have additional future obligations under the Patheon Agreement. WuXi STA Manufacturing In April 2020, the Company entered into a Supply Agreement with STA Pharmaceutical Hong Kong Limited, a subsidiary of WuXi AppTec, or WuXi STA, or, as amended, the WuXi STA DS Agreement. Under the WuXi STA DS Agreement, WuXi STA will manufacture Vafseo drug substance for commercial use under a volume-based pricing structure through April 2, 2029. Pursuant to the WuXi STA DS Agreement, the Company has agreed to purchase a certain percentage of the global demand for Vafseo drug substance from WuXi STA. As of March 31, 2026, the Company has committed to purchase $69.2 million of Vafseo drug substance from WuXi STA through the end of 2027, however, as estimated global demand fluctuates, the Company may have additional future obligations under the WuXi STA DS Agreement. Additionally, on February 10, 2021, the Company entered into a Supply Agreement with WuXi STA, which was amended on October 15, 2024, or the WuXi STA DP Agreement, under which WuXi STA will manufacture and supply Vafseo drug product for commercial purposes under a volume-based pricing structure through January 1, 2032. The Vafseo drug product price is reviewed annually by the Company and WuXi STA. The Company also reimburses WuXi STA for certain reasonable expenses. Pursuant to the WuXi STA DP Agreement, the Company has agreed to purchase a certain percentage of global demand for Vafseo drug product from WuXi STA. The WuXi STA DP Agreement may be renewed or extended by mutual agreement of the Company and WuXi STA with at least eighteen months’ prior written notice. The WuXi STA DP Agreement allows the Company to terminate the relationship on 180 calendar days’ prior written notice to WuXi STA for any reason. In addition, each party has the ability to terminate the WuXi STA DP Agreement upon the occurrence of certain conditions. As of March 31, 2026, the Company has committed to purchase $2.1 million of Vafseo drug product from WuXi STA through the first half of 2026, however, as estimated global demand fluctuates, the Company may have additional future obligations under the WuXi STA DP Agreement. License Agreements Panion License Agreement On April 17, 2019, the Company and Panion & BF Biotech, Inc., or Panion, entered into a second amended and restated license agreement, or the Panion Amended License Agreement, which amended and restated in full the license agreement between the Company and Panion. The Panion Amended License Agreement provides the Company with an exclusive license under Panion-owned know-how and patents covering the rights to sublicense, develop, make, use, sell, offer for sale, import and export ferric citrate worldwide, excluding certain Asian-Pacific countries, or the Licensor Territory. The Panion Amended License Agreement also provides Panion with an exclusive license under Company-owned patents, covering the rights to sublicense (with the Company’s written consent), develop, make, use, sell, offer for sale, import and export ferric citrate in certain countries in the Licensor Territory. Under the Panion Amended License Agreement, Panion is eligible to receive from the Company or any sublicensee royalty payments based on a mid-single digit percentage of sales of ferric citrate in the Company’s licensed territories. The Company is eligible to receive from Panion or any sublicensee royalty payments based on a mid-single digit percentage of net sales of ferric citrate in Panion’s licensed territories. See Note 10, Commitments and Contingencies, of the Notes to the Consolidated Financial Statements in the 2025 Form 10-K for a more detailed description of the Panion Amended License Agreement. The Company incurred royalty payments due to Panion of approximately $2.3 million and $2.6 million during the three months ended March 31, 2026 and 2025, respectively, relating to the Company’s sales of Auryxia in the U.S. and Japan Tobacco, Inc. and its subsidiary Torii Pharmaceutical Co., Ltd., collectively, JT and Torii’s, net sales of Riona in Japan. Cyclerion Agreement In June 2021, the Company entered into a license agreement, or the Cyclerion Agreement, with Cyclerion Therapeutics Inc., or Cyclerion, under which the Company obtained an exclusive global license under certain intellectual property rights to research, develop and commercialize praliciguat, an investigational oral soluble guanylate cyclase stimulator. Under the terms of the Cyclerion Agreement, the Company made an upfront payment of $3.0 million to Cyclerion, which was paid during the second quarter of 2021. Substantially all of the fair value of the assets acquired in conjunction with the Cyclerion Agreement was concentrated in the acquired license. As a result, the Company accounted for this transaction as an asset acquisition under ASU No. 2017-01, Business Combinations (Topic 805): Clarifying the Definition of a Business. The $3.0 million upfront payment was charged to research and development expense at acquisition in June of 2021, as it relates to a development stage compound with no alternative future use. In December 2024, the Company and Cyclerion entered into Amendment #1 to the Cyclerion Agreement, pursuant to which the Company agreed to pay Cyclerion (i) $1.25 million, which was paid in December 2024, and (ii) $0.5 million, which was paid in September 2025. In addition, the parties agreed to the reduction of certain development milestones and the increase of certain royalty rates on net sales and sublicense income. During the year ended December 31, 2024, the Company recorded the $1.25 million payment and $0.5 million payment to research and development expense in accordance with ASC 730, Research and Development, as praliciguat remains a development stage compound with no alternative future use. Furthermore, the only contingency as it related to the $0.5 million payment made in September 2025 was the passage of time. Under the Cyclerion Agreement, as amended, Cyclerion is eligible to receive up to an additional aggregate of $197.5 million from the Company in specified development and regulatory milestone payments on a product-by-product basis. In December 2025, the Company incurred a $1.0 million development milestone in connection with the initiation of a Phase 2 clinical trial for praliciguat in the U.S., which was charged to research and development expense during the year ended December 31, 2025. The $1.0 million development milestone was paid during the three months ended March 31, 2026. Cyclerion will also be eligible to receive specified commercial milestones as well as tiered royalties ranging from a mid-single-digit percentage to twenty percent of net sales, on a product-by-product basis, and subject to reduction upon expiration of patent rights or the launch of a generic product in the territory. Unless earlier terminated, the Cyclerion Agreement will expire on a product-by-product and country-by-country basis upon the expiration of the last royalty term, which ends upon the longest of (i) the expiration of the patents licensed under the Cyclerion Agreement, (ii) the expiration of regulatory exclusivity for such product and (iii) ten years from first commercial sale of such product. The Company may terminate the Cyclerion Agreement in its entirety or only with respect to a particular licensed compound or product upon 180 days' prior written notice to Cyclerion. The parties also have customary termination rights, subject to a cure period, in the event of the other party’s material breach of the Cyclerion Agreement or in the event of certain additional circumstances. Q32 Agreement On November 28, 2025, or the APA Closing Date, the Company entered into an Asset Purchase Agreement, or the Q32 Purchase Agreement, with Q32 Bio Inc. and Q32 Bio Operations Inc, or together, Q32, pursuant to which Q32 sold and assigned to the Company, and the Company purchased and assumed from Q32 substantially all assets and liabilities of Q32 and its affiliates related to the research, development, manufacture and commercialization of Q32's clinical-stage development candidate known as ADX-097 (now referred to as AKB-097) worldwide for the treatment, prevention or diagnosis of any disease or condition in humans. AKB-097, which has been evaluated in a Phase 1 clinical trial in healthy volunteers, is a tissue-targeted C3d-Factor H fusion protein complement inhibitor with the potential to treat rare kidney diseases. Under the terms of the Q32 Purchase Agreement, the Company (i) made an upfront payment of $7.0 million on the APA Closing Date, (ii) will make an additional upfront payment of $3.0 million on the six-month anniversary of the APA Closing Date, (iii) will make certain milestone payments upon the achievement of specified development and regulatory milestone events related to AKB-097 up to an aggregate amount equal to $94.5 million, including a $2.0 million development milestone payment upon the earlier of initiation of a Phase 2 clinical trial and December 31, 2026, (iv) will make certain milestone payments upon the achievement of specified commercial milestone events with respect to the net sales of AKB-097 up to an aggregate amount equal to $487.5 million, and (v) will make certain royalty payments based on the net sales of AKB-097 with royalty percentage tiers ranging from the low single digits to mid-teen percentages. The royalties will expire on a country-by-country basis on the later to occur of (a) the date of expiration of the last-to-expire valid claim of any transferred patent right that covers such product in such country, and (b) the tenth anniversary of the first commercial sale of such product. The transaction was accounted for as an asset acquisition as the acquired assets did not meet the definition of a business. The Company did not acquire any outputs and there was not an acquired substantive process in place to create outputs. The total purchase consideration of $12.8 million was composed of the $7.0 million upfront payment, the $3.0 million additional upfront payment, the $2.0 million development milestone payment and $0.8 million of direct transaction costs. The only contingency as it relates to the $2.0 million milestone payment upon the earlier of initiation of a Phase 2 clinical trial and December 31, 2026 is the passage of time. The fair value was allocated to in process research and development, or IPR&D, assets with no alternative future use for these assets at the closing of the acquisition. As a result, the Company recorded a charge of $12.8 million related to acquired IPR&D expense on the consolidated statements of operations and comprehensive loss during the year ended December 31, 2025. The $3.0 million additional upfront payment and the $2.0 million development milestone payment are included in accrued expenses and other current liabilities in the consolidated balance sheet as of March 31, 2026. Other Third-Party Contracts The Company contracts with various organizations to conduct R&D activities with remaining contract costs to the Company of approximately $81.5 million at March 31, 2026. The scope of the services under these R&D contracts can be modified upon mutual agreement of the parties, and the contracts or scope of services can be cancelled by the Company upon written notice. In some instances, the contracts may be cancelled by the third party upon written notice. Litigation and Related Matters The Company is involved from time to time in various legal proceedings arising in the normal course of business. The Company provides disclosure when a loss in excess of any reserve is reasonably possible, and if estimable, the Company discloses the potential loss or range of possible loss. Significant judgment is required to assess the likelihood of various potential outcomes and the quantification of loss in those scenarios. Changes in the Company’s estimates could have a material impact and are recorded as litigation progresses and new information comes to light. Although the outcomes of potential legal proceedings are inherently difficult to predict, the Company does not expect the resolution of current legal proceedings to have a material adverse effect on its financial position, results of operations or cash flows of the Company. Guarantees and Indemnifications As permitted under Delaware law, the Company may indemnify its officers, directors and employees for certain events or occurrences that happen by reason of their relationship with, or position held at, the Company. The Company may also be subject to indemnification obligations by law with respect to the actions of its employees under certain circumstances and in certain jurisdictions. The Company maintains director and officer liability insurance coverage that is intended to cover a portion of amounts that may be due with respect to indemnification after a deductible is met. Further, the Company is a party to a variety of agreements in the ordinary course of business under which it may be obligated to indemnify third parties with respect to certain matters. For the three months ended March 31, 2026 and 2025, the Company did not experience any losses related to these indemnification obligations, and no claims were outstanding as of March 31, 2026. The Company does not have any claims related to these indemnification obligations and consequently concluded that the fair value of these obligations is negligible and no related accruals were recorded.

Cover Page - shares	3 Months Ended
Cover Page - shares	Mar. 31, 2026	May 04, 2026
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2026
Document Transition Report	false
Entity File Number	001-36352
Entity Registrant Name	AKEBIA THERAPEUTICS, INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	20-8756903
Entity Address, Address Line One	245 First Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
Entity Address, Postal Zip Code	02142
City Area Code	617
Local Phone Number	871-2098
Title of 12(b) Security	Common Stock, $0.00001 par value per share
Trading Symbol	AKBA
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		268,258,243
Amendment Flag	false
Document Fiscal Year Focus	2026
Document Fiscal Period Focus	Q1
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001517022

INDEBTEDNESS - Narrative (Details) $ / shares in Units, $ in Thousands				3 Months Ended
	Feb. 03, 2025 USD ($) $ / shares shares	Apr. 19, 2024 USD ($)	Jan. 29, 2024 USD ($) tranche $ / shares shares	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)	Jul. 23, 2025 shares	Jul. 21, 2025 $ / shares shares	Feb. 28, 2025 $ / shares shares
Line of Credit Facility [Line Items]
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]			Secured Overnight Financing Rate (SOFR) [Member]
Warrant to purchase common stock (in shares) \| shares	1,153,846		3,076,923				1,408,588	2,115,384	1,153,846
Exercise price (in dollars per share) \| $ / shares	$ 1.30		$ 1.30					$ 1.30	$ 1.30
Warrant exercise period (in years)	8 years								8 years
Warrant liability				$ 2,524		$ 2,980
Secured Debt \| Term Loan Facility \| Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 55,000
Line of credit, maximum borrowing capacity, number of available tranches \| tranche			3
Variable rate, floor (as percent)			4.25%
Basis spread on variable rate (as percent)			6.75%
Debt instrument, cap rate (as percent)			15.00%
Debt instrument, interest rate (as percent)				11.00%
Interest expense				$ 2,200	$ 2,100
Annual interest rate, increase (as percent)			3.00%
Late fee percentage			2.00%
Exit fee percentage			0.75%
Debt covenant, cash and cash equivalents			$ 15,000
Debt covenant, revenue period (in months)			12 months
Debt covenant, revenue			$ 150,000
Secured Debt \| Term Loan Facility \| Line of Credit \| Minimum
Line of Credit Facility [Line Items]
Transaction fee percentage			1.00%
Prepayment fee percentage			1.00%
Secured Debt \| Term Loan Facility \| Line of Credit \| Maximum
Line of Credit Facility [Line Items]
Transaction fee percentage			1.25%
Prepayment fee percentage			4.00%
Secured Debt \| Term Loan Facility, Tranche A \| Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 37,000
Proceeds from line of credit			34,500
Secured Debt \| Term Loan Facility, Tranche B \| Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			8,000
Proceeds from line of credit		$ 7,500
Secured Debt \| Term Loan Facility, Tranche C \| Line of Credit
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 10,000
Proceeds from line of credit	$ 9,300

CAPITAL STOCK	3 Months Ended
CAPITAL STOCK	Mar. 31, 2026
Equity [Abstract]
CAPITAL STOCK	CAPITAL STOCK Authorized and Outstanding Capital Stock As of March 31, 2026, the authorized capital stock of the Company included 350,000,000 shares of common stock, $0.00001 par value per share, of which 267,898,415 and 265,424,818 shares were issued and outstanding as of March 31, 2026 and December 31, 2025, respectively; and 25,000,000 shares of undesignated preferred stock, $0.00001 par value per share, of which no shares were issued and outstanding as of March 31, 2026 and December 31, 2025. At-the-Market Facility On September 3, 2024, in connection with the filing of a new shelf registration statement on Form S-3, the Company filed a prospectus related to the Company's amended and restated sales agreement (which amended and restated the Original Sales Agreement), with Jefferies, as the Company’s sales agent, pursuant to which the Company is able to offer and sell up to $75.0 million of its common stock at current market prices from time to time. Since September 12, 2024 (the date the Company’s shelf registration statement on Form S-3 went effective) through December 31, 2025, the Company sold 23,708,995 shares of its common stock under this program with gross proceeds of $43.0 million ($42.2 million, net of offering expenses). During the three months ended March 31, 2026, the Company did not sell any shares of its common stock under this program. Public Offering On March 19, 2025, the Company entered into an underwriting agreement, or the Underwriting Agreement, with Leerink Partners LLC and Piper Sandler & Co., as representatives of the several underwriters named therein, collectively, the Underwriters, relating to an underwritten public offering, or the Offering, of 25,000,000 shares, or the Shares, of the Company's common stock. The offering price was $2.00 per share, and the Underwriters agreed to purchase the Shares from the Company pursuant to the Underwriting Agreement at a price of $1.88 per share. Under the terms of the Underwriting Agreement, the Company granted the Underwriters a 30-day option to purchase up to 3,750,000 additional shares of common stock, or the Additional Shares, at the public offering price per share, and the Underwriters partially exercised their option and purchased 850,000 Additional Shares on April 22, 2025. Net proceeds from the Offering were $46.5 million, after deducting underwriting discounts and commissions and offering expenses and net proceeds from the Offering of the Additional Shares were $1.6 million, after deducting underwriting discounts and commissions and offering expenses. Unregistered Common Stock In connection with the Vifor License Agreement, CSL Vifor owns 7,571,429 shares of common stock that are unregistered under the Securities Act. See Note 8, Liability Related to Settlement Royalties, Working Capital Fund Liability and Liability Related to Sale of Future Royalties, for more information. Warrants to Purchase Common Stock In connection with the BlackRock Credit Agreement, described in more detail in Note 7, Indebtedness, the Company issued a warrant to purchase 3,076,923 shares of the Company’s common stock, at an exercise price per share of $1.30, and upon the borrowing of Tranche C in February 2025, the Company issued additional warrants to purchase 1,153,846 shares of the Company’s common stock at an exercise price per share of $1.30. Each warrant is exercisable for eight years from the date of issuance. The warrants and the common stock issuable upon the exercise of such warrants were not registered under the Securities Act. Accordingly, the holder thereof may only sell common stock issued upon exercise of such warrants pursuant to an effective registration statement under the Securities Act covering the resale of those shares, an exemption under Rule 144 under the Securities Act or another applicable exemption under the Securities Act. On July 21, 2025, the Warrant Holder exercised its option to purchase 2,115,384 shares of the Company's common stock under the Initial Warrant on a cashless basis at an exercise price per share of $1.30. The cashless exercise allowed the Warrant Holder to convert the warrants into shares of the Company's common stock without the need for a cash payment. Instead of paying cash upon exercise, the Warrant Holder received a reduced number of shares based on a predetermined formula. On July 23, 2025, as a result of the cashless exercise, the Company issued 1,408,588 shares of common stock to the Warrant Holder under the Initial Warrant.

- Definition

The entire disclosure for equity.

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+ Details

LIABILITY RELATED TO SETTLEMENT ROYALTIES, WORKING CAPITAL FUND LIABILITY AND LIABILITY RELATED TO SALE OF FUTURE ROYALTIES - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended			3 Months Ended
	Feb. 28, 2022	Feb. 28, 2021	May 31, 2017	Mar. 31, 2026	Mar. 31, 2025	May 31, 2028	May 31, 2027	May 31, 2026	Dec. 31, 2025	Jul. 01, 2025	Jul. 10, 2024	May 03, 2024	Mar. 18, 2022	Feb. 18, 2022	Feb. 25, 2021
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, issued (in shares)				267,898,415					265,424,818
Annual effective interest rate (as percent)				0.00%
Interest expense				$ (4,691)	$ (7,770)
Refund liability to customer, amortization of discount				1,200	1,100
Refund liability to customer, amortization of deferred gain				800	1,000
Maximum annual royalty payout capacity		$ 13,000
Percentage of royalty payment to be received once maximum annual royalty payout has been paid		85.00%
Maximum aggregate royalty payout capacity		$ 150,000
Liability related to sale of future royalties, net of current portion				$ 50,414					$ 50,608						$ 44,800
Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Sale of stock, price per share (in dollars per share)	$ 5.00
Number of shares sold in offering (in shares)	4,000,000
Aggregate net proceeds from offering	$ 20,000
Vifor (International) Ltd.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Annual effective interest rate (as percent)				21.20%
Interest expense				$ 3,600	5,400
Refund liability to customer, gross													$ 40,000
Vifor (International) Ltd. \| License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Common stock, issued (in shares)			3,571,429
Sale of stock, price per share (in dollars per share)			$ 14.00
Proceeds from common stock sold			$ 50,000
Vifor (International) Ltd. \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue, remaining performance obligation, profit share percentage														66.00%
Deferred revenue														$ 25,000
Long-term deferred revenue	$ 13,600		$ 4,700
Transaction price														$ 43,300
Refund liability to customer, interest rate (as percent)													15.00%
Vifor (International) Ltd. \| License \| Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Long-term deferred revenue				18,300
CSL Vifor
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Tiered royalty payments as a percentage of net sales											$ 450,000
Refund liability to customer, interest rate (as percent)												15.00%
Royalty payments										$ 40,000
CSL Vifor \| Forecast
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty true-up payments						$ 40,000	$ 20,000	$ 10,000
CSL Vifor \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Tiered royalty payments as a percentage of net sales											$ 450,000
Tiered royalty payments, percentage												14.00%
CSL Vifor \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Tiered royalty payments, percentage												8.00%
Vifor International Limited, First Investment \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Long-term deferred revenue				4,700
Vifor International Limited, Second Investment \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Long-term deferred revenue				13,600
HealthCare Royalty Partners IV, L.P.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payments for royalties				$ 500	$ 500

SUBSEQUENT EVENTS	3 Months Ended
SUBSEQUENT EVENTS	Mar. 31, 2026
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS The Company has evaluated events and transactions occurring after the balance sheet date through the filing date of this Form 10-Q with the Securities and Exchange Commission, to ensure that the unaudited condensed consolidated financial statements include appropriate disclosure of events both recognized in the accompanying unaudited condensed consolidated financial statements as of March 31, 2026, and events which occurred subsequently but were not recognized in the consolidated financial statements. The Company has concluded that no subsequent events have occurred that require disclosure other than the following: Cambridge Lease Extension - Lab Space On April 9, 2026, the Company extended the term of the Cambridge Lease with respect to the laboratory space from September 11, 2026 to October 31, 2026. See Note 9, Leases, for further information on the Cambridge Lease.

FAIR VALUE MEASUREMENTS (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	$ 135,983	$ 172,689
Warrant liability	2,524	2,980
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	135,983	172,689
Warrant liability	0	0
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Warrant liability	2,524	2,980
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market funds	0	0
Warrant liability	$ 0	$ 0

- Definition

Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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-Name Accounting Standards Codification
-Section S99
-Paragraph 5B
-Subparagraph (SX 210.12-13B(Column E)(Footnote 4))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147477271/946-320-S99-5B

+ Details

GOODWILL (Details) - USD ($)	Mar. 31, 2026	Dec. 31, 2025
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	$ 59,044,000	$ 59,044,000
Goodwill, accumulated impairment losses	$ 0

- Definition

Amount, after accumulated impairment loss, of asset representing future economic benefit arising from other asset acquired in business combination or from joint venture formation or both, that is not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/exampleRef
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-Name Accounting Standards Codification
-Section 55
-Paragraph 24
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Reference 4: http://www.xbrl.org/2003/role/exampleRef
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-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(15))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

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-Paragraph 1
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-Topic 942
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-Section S99
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-Topic 805
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-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479581/805-30-50-4

+ Details

STOCK-BASED COMPENSATION PLANS

3 Months Ended

Mar. 31, 2026

Equity [Abstract]

STOCK-BASED COMPENSATION PLANS

Stock-Based Compensation Plans

The Company incurred stock-based compensation expenses of $3.7 million and $2.2 million for the three months ended March 31, 2026 and 2025, respectively.

Equity Incentive Plans

The following table contains information about the Company's equity incentive plans:


			March 31, 2026		December 31, 2025
Title of Plan	Group Eligible	Type of Award Granted (or to be Granted)	Awards Outstanding	Additional Awards Available for Grant	Awards Outstanding	Additional Awards Available for Grant
Keryx Equity Plans(1)(2)	Employees, directors and consultants	Stock options and restricted stock units (RSUs)	91,696	—	148,860	—
Akebia Therapeutics, Inc. 2014 Incentive Plan, as amended (2) (3) (the 2014 Plan)	Employees, directors, consultants and advisors	Stock options, RSUs, stock appreciation rights (SARs) and performance awards	7,634,941	—	8,412,898	—
Akebia Therapeutics, Inc. 2023 Stock Incentive Plan, as amended(3) (4) (the 2023 Plan) (replaced 2014 Plan)	Employees, officers, directors, consultants and advisors	Stock options, SARs, restricted stock, unrestricted stock, RSUs, performance awards, other share-based awards and dividend equivalents	23,224,380	16,482,848	15,913,729	24,723,655

(2) New awards are no longer being granted under these plans.

(4) On June 10, 2025, the 2023 Plan was amended to increase the number of shares of common stock available for issuance thereunder by 18,900,000 shares.

Common Stock Options and Stock Appreciation Rights

During the three months ended March 31, 2026, the Company granted 4,011,200 options to employees under the 2023 Plan. Options and SARs granted by the Company generally vest over periods of between 12 and 48 months, subject, in each case, to the individual’s continued service through the applicable vesting date. Options and SARs generally vest either 100% on the first anniversary of the grant date or in installments of (i) 25% at the one year anniversary and (ii) 12 equal quarterly installments beginning after the one year anniversary of the grant date, subject to the individual’s continuous service with the Company. Options and SARs generally expire ten years after the date of grant.

The Company also maintains an inducement award program with a share pool that is separate from the Company's equity plans under which inducement awards may be granted consistent with Nasdaq Listing Rule 5635(c)(4). During the three months ended March 31, 2026, the Company granted 858,775 options to purchase shares of the Company’s common stock to new hires as inducements to such employees entering into employment with the Company, of which 858,775 options remained outstanding as of March 31, 2026.

The Company grants annual service-based stock options to employees and directors and granted SARs to certain executives under the 2023 Plan and previously granted options to employees and directors under the 2014 Plan. In addition, the Company issues stock options to directors, new hires and occasionally to other employees not in connection with the annual grant process.

Finally, the Company periodically grants performance-based stock options which generally vest in connection with the achievement of specified commercial, regulatory and corporate milestones. The performance-based stock options also generally feature a time-based vesting component. The expense recognized for these awards is based on the grant date fair value of the Company’s common stock multiplied by the number of options granted and recognized over time based on the probability of meeting such commercial, regulatory and corporate milestones.

The combined stock option activity for the three months ended March 31, 2026, is as follows:


	Stock Options	Weighted Average Exercise Price		Weighted-Average Contractual Life (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at December 31, 2025	18,152,258	$	2.85	6.97 years	$	3,690
Granted	4,869,975	$	1.41	—	—
Exercised	(28,424)	$	0.71	—	—
Expired	(593,220)	$	5.77	—	—
Canceled and forfeited	(529,058)	$	1.78	—	—
Outstanding at March 31, 2026	21,871,531	$	2.48	7.59 years	$	2,691
Exercisable at March 31, 2026	10,605,986	$	3.23	6.04 years	$	2,059

As of March 31, 2026, there was approximately $14.4 million of unrecognized compensation costs related to stock options, which is expected to be recognized over a weighted average period of 2.96 years.

Restricted Stock Units

Generally, RSUs granted by the Company vest in one of the following ways: (i) 100% of each RSU grant vests on the first anniversary of the grant date, (ii) one third of each RSU grant vests on the first, second and third anniversaries of the grant date, (iii) 50% of each RSU grant vests on the first anniversary and 25% of each RSU grant vests every six months after the one year anniversary of the grant date, or (iv) one third of each RSU grant vests on the first anniversary of the grant date and the remaining two thirds vests in eight substantially equal quarterly installments beginning after the one year anniversary, subject, in each case, to the individual’s continued service through the applicable vesting date. The grant-date fair value of the RSUs is recognized as expense on a straight-line basis. The Company determines the fair value of the RSUs based on the closing price of the common stock on the date of the grants.

The Company also periodically grants performance-based restricted stock units, or PSUs, to employees under the 2023 Plan and previously granted PSUs under the 2014 Plan. The PSUs granted by the Company generally vest in connection with the achievement of specified commercial, regulatory and corporate milestones. The PSUs also generally feature a time-based vesting component. The expense recognized for these awards is based on the grant date fair value of the Company’s common stock multiplied by the number of units granted and recognized over time based on the probability of meeting such commercial, regulatory and corporate milestones.

In addition, the Company has granted PSUs to certain employees under the 2023 Plan with a market condition. The PSUs also generally feature a time-based vesting component. The Company uses a Monte Carlo simulation to determine fair value of the award at the grant date. The expense recognized for these awards is based on the calculated fair value multiplied by the number of the target units granted and is amortized over the service period.

RSU and PSU activity is as follows:


	2014 Plan			2023 Plan
	Number of Shares	Weighted Average Grant Date Fair Value		Number of Shares	Weighted Average Grant Date Fair Value
Unvested as of December 31, 2025	330,622	$	0.63	5,992,607	$	2.09
Granted	—	$	—	5,426,300	$	1.41
Vested	(330,622)	$	0.63	(2,018,204)	$	2.01
Forfeited and canceled	—	$	—	(321,217)	$	1.80
Unvested as of March 31, 2026	—	$	—	9,079,486	$	1.71

As of March 31, 2026, there was $12.7 million of unrecognized compensation costs related to time-based RSUs and PSUs, which is expected to be recognized over a weighted-average period of 2.19 years.

Employee Stock Purchase Plan

On June 6, 2019, the Company's stockholders approved the Amended and Restated 2014 Employee Stock Purchase Plan, or ESPP. Under the ESPP, substantially all employees may voluntarily enroll to purchase shares of the Company’s common stock through payroll deductions at a price equal to 85% of the lower of the fair market values of the stock as of the beginning or

the end of the six-month offering period. An employee's payroll deductions under the ESPP are limited to 15% of the employee's compensation, and an employee may not purchase more than $25,000 worth of stock during any calendar year. In addition, an employee may not purchase more than 1,500 shares in any six-month offering period. As of March 31, 2026 and December 31, 2025, a total of 4,164,300 and 4,260,647 shares of the Company’s common stock were available for future issuance under the ESPP, respectively. The Company issued 96,347 shares under the ESPP during the three months ended March 31, 2026.

Stock-Based Compensation Expense

The Black-Scholes option pricing model is used to estimate the fair value of the common stock options. The weighted-average assumptions used in calculating the fair values of the rights to acquire stock under the 2023 Plan, the 2014 Plan and inducement awards were as follows:


	Three Months Ended March 31,
Common Stock Options	2026				2025
Risk-free interest rate	3.61	%	-	4.00%	4.00	%	-	4.38%
Expected volatility	110.17	%	-	119.09%	111.97	%	-	117.83%
Expected term (years)	6.25 years		-	6.25 years	6.25 years		-	6.25 years
Expected dividend yield	—%				—%
Weighted average grant date fair value	$1.21				$1.92

The Company has classified stock-based compensation in its unaudited condensed consolidated statements of operations and comprehensive income (loss) as follows (in thousands):


	Three Months Ended March 31,
	2026		2025
Cost of goods sold	$	197	$	139
Research and development	1,056		467
Selling, general and administrative	2,415		1,581

Total stock-based compensation	$	3,668	$	2,187

LIABILITY RELATED TO SETTLEMENT ROYALTIES, WORKING CAPITAL FUND LIABILITY AND LIABILITY RELATED TO SALE OF FUTURE ROYALTIES (Tables)

3 Months Ended

Mar. 31, 2026

Other Liabilities Disclosure [Abstract]

Schedule of Liability Related to Sale of Future Royalties

As of March 31, 2026 and December 31, 2025, the balances related to the settlement royalties liability were as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Current portion (included in accrued expenses and other current liabilities)	$	15,397	$	12,516
Long-term portion	54,842		54,750
Total settlement royalties liability	$	70,239	$	67,266

As of March 31, 2026 and December 31, 2025, the balances related to the Working Capital Fund liability were as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Current portion	$	23,445	$	17,356
Long-term portion	16,405		22,606
Total Working Capital Fund liability	$	39,850	$	39,962

As of March 31, 2026 and December 31, 2025 the balances were as follows (in thousands):


Liability related to sale of future royalties	March 31, 2026		December 31, 2025
Current portion (included in accrued expenses and other current liabilities)	$	1,401	$	1,664
Long-term portion	50,414		50,608
Total liability related to sale of future royalties	$	51,815	$	52,272

ADDITIONAL BALANCE SHEET DETAIL

3 Months Ended

Mar. 31, 2026

Payables and Accruals [Abstract]

ADDITIONAL BALANCE SHEET DETAIL

Prepaid expenses and other current assets are as follows (in thousands):


Description	March 31, 2026		December 31, 2025

Restricted cash	1,704		1,699
Other	3,601		3,771
Total prepaid expenses and other current assets	$	5,305	$	5,470

Other prepaid expenses and other current assets, among other things, include capitalized implementation costs, prepaid insurance, prepaid clinical trial costs and prepaid information technology costs.

Other long-term assets are as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Long-term inventories	$	56,060	$	59,129

Other	514		552
Total other long-term assets	$	56,574	$	59,681

See Note 4, Inventories, for further information on long-term inventories.

Accrued expenses and other current liabilities are as follows (in thousands):


Description	March 31, 2026		December 31, 2025
Product revenue allowances excluding rebates	$	8,371	$	7,916
Product rebates	70,556		64,674
Product return provisions, current portion	1,972		2,375
Clinical trial costs	1,329		1,188
Compensation and related benefits	8,320		11,018
Operating lease liabilities	2,127		3,548
Royalties due to Panion & BF Biotech, Inc.	2,944		3,924
Professional fees	502		1,597
Accrued manufacturing costs	1,513		1,808

Liability related to sale of future royalties, current portion	1,401		1,664
Settlement royalties liability, current portion	15,397		12,516
Payments due to Q32	5,000		5,000
Other	5,630		4,488
Total accrued expenses and other current liabilities	$	125,062	$	121,716

LICENSE, COLLABORATION AND OTHER REVENUE - Medice License Agreement - Narrative (Details)		3 Months Ended			12 Months Ended
	May 24, 2023 USD ($) performance_obligation	Mar. 31, 2026 USD ($)	Mar. 31, 2025 USD ($)	Jun. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)	Dec. 31, 2025 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized		$ 0	$ 0
Accounts receivable, net		62,536,000				$ 47,031,000
Payables		8,386,000				$ 21,185,000
Total revenues		53,544,000	57,336,000
License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues		1,552,000	1,545,000
MEDICE Arzneimittel Pütter GmbH & Co. KG \| Collaborative Arrangement, Transaction with Party to Collaborative Arrangement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Percentage of net product margin on sales in collaborative arrangement	70.00%
MEDICE Arzneimittel Pütter GmbH & Co. KG \| License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue	$ 10,000,000.0	0
Eligible milestone payments (up to)	$ 100,000,000.0
Tiered royalties, expected timing of satisfaction period (in years)	12 years
Termination of agreement by counterparty, written notice period (in months)	12 months
Termination of agreement eligible by counterparty, period after effective agreement date (in months)	12 months
Number of performance obligations \| performance_obligation	1
Proceeds from customers			1,400,000	$ 8,600,000
Contract asset		0
Accounts receivable, net		0
Payables		0
MEDICE Arzneimittel Pütter GmbH & Co. KG \| License \| Minimum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Tiered royalties (as percent)	10.00%
MEDICE Arzneimittel Pütter GmbH & Co. KG \| License \| Maximum
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Tiered royalties (as percent)	30.00%
MEDICE Arzneimittel Pütter GmbH & Co. KG \| License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized					$ 10,000,000.0
Contract asset		100,000
Total revenues		32,000	7,000
MEDICE Arzneimittel Pütter GmbH & Co. KG \| Royalty payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues		0	0
MEDICE Arzneimittel Pütter GmbH & Co. KG \| Supply agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue		0
Payables		0
Total revenues		0	0
MEDICE Arzneimittel Pütter GmbH & Co. KG \| Amended Supply Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Total revenues		$ 0	$ 0

LIABILITY RELATED TO SETTLEMENT ROYALTIES, WORKING CAPITAL FUND LIABILITY AND LIABILITY RELATED TO SALE OF FUTURE ROYALTIES - Schedule of Liability Related to Working Capital Funds (Details) - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Other Liabilities Disclosure [Abstract]
Current portion	$ 23,445	$ 17,356
Long-term portion	16,405	22,606
Total Working Capital Fund liability	$ 39,850	$ 39,962

LICENSE, COLLABORATION AND OTHER REVENUE - JT and Torii Sublicense Agreement - Narrative (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2026 USD ($) performance_obligation	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue	$ 53,544	$ 57,336
Accounts receivable, net	$ 62,536		$ 47,031
JT and Torii \| Sublicense Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of performance obligations \| performance_obligation	2
Recognized revenue	$ 1,200	$ 1,200
Accounts receivable, net	$ 1,200

- Definition

+ References

+ Details

LEASES - Narrative (Details)		3 Months Ended
LEASES - Narrative (Details)	Jan. 27, 2026 USD ($) ft² extension_option	Mar. 31, 2026 USD ($) ft²	Mar. 31, 2025 USD ($)	Dec. 31, 2025 USD ($)
Lessee, Lease, Description [Line Items]
Operating lease, remaining lease term (in years)		5 months 12 days
Operating lease, cost		$ 1,200,000
Operating lease, payments		$ 1,500,000	$ 1,500,000
Lessee, operating lease, leased square feet \| ft²	43,474
Lessee, operating lease, expiration period (in months)	84 months
Lessee, operating lease, cost of additional square foot (in dollars per sq foot)	$ 1.00
Total security deposit in connection with lease	$ 800,000
Minimum
Lessee, Lease, Description [Line Items]
Operating lease, incremental borrowing rates based on remaining lease term (in percent)		6.65%
Maximum
Lessee, Lease, Description [Line Items]
Operating lease, incremental borrowing rates based on remaining lease term (in percent)		6.94%
Laboratory Space
Lessee, Lease, Description [Line Items]
Lessee, operating lease, leased square feet \| ft²	14,956
Unrecorded unconditional purchase obligation	$ 1,000,000.0
Operating lease, increase in rent, percentage	3.00%
Office Space
Lessee, Lease, Description [Line Items]
Lessee, operating lease, leased square feet \| ft²	28,518
Operating lease extensions (in extension options) \| extension_option	1
Lease extension period	5 years
Unrecorded unconditional purchase obligation	$ 900,000
Cambridge
Lessee, Lease, Description [Line Items]
Area of property leased (in square feet) \| ft²		65,167
Cambridge \| Letter of Credit
Lessee, Lease, Description [Line Items]
Total security deposit in connection with lease		$ 1,700,000		$ 1,700,000
Cambridge \| Office And Storage Space
Lessee, Lease, Description [Line Items]
Leased area subject to expiration \| ft²		59,216
Cambridge \| Laboratory Space
Lessee, Lease, Description [Line Items]
Leased area subject to expiration \| ft²		5,951

LEASES - Schedule of Future Commitments under Non-Cancelable Leases (Details) $ in Thousands	Mar. 31, 2026 USD ($)
Leases [Abstract]
2026	$ 2,142
Total lease commitments	2,142
Less: present value adjustment	(15)
Current operating lease liabilities	$ 2,127

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2026	Dec. 31, 2025
Current assets:
Cash and cash equivalents	$ 162,644	$ 184,844
Inventories	12,996	15,610
Accounts receivable, net	62,536	47,031
Prepaid expenses and other current assets	5,305	5,470
Total current assets	243,481	252,955
Property and equipment, net	956	1,222
Operating right-of-use assets	2,465	3,663
Goodwill	59,044	59,044
Other long-term assets	56,574	59,681
Total assets	362,520	376,565
Current liabilities:
Accounts payable	8,386	21,185
Accrued expenses and other current liabilities	125,062	121,716
Current portion of deferred revenue	4,496	2,681
Current portion of long-term debt	12,495	0
Working Capital Fund liability, current portion	23,445	17,356
Total current liabilities	173,884	162,938
Long-term debt, net of current portion	36,395	48,250
Liability related to settlement royalties, net of current portion	54,842	54,750
Liability related to sale of future royalties, net of current portion	50,414	50,608
Working Capital Fund liability, net of current portion	16,405	22,606
Warrant liability	2,524	2,980
Other long-term liabilities	681	1,823
Total liabilities	335,145	343,955
Commitments and contingencies (Note 10)
Stockholders' equity:
Preferred stock $0.00001 par value; 25,000,000 shares authorized at March 31, 2026 and December 31, 2025; no shares issued and outstanding at March 31, 2026 and December 31, 2025	0	0
Common stock $0.00001 par value; 350,000,000 shares authorized at March 31, 2026 and December 31, 2025; 267,898,415 and 265,424,818 shares issued and outstanding at March 31, 2026 and December 31, 2025, respectively	2	2
Additional paid-in capital	1,720,126	1,716,307
Accumulated other comprehensive income	6	6
Accumulated deficit	(1,692,759)	(1,683,705)
Total stockholders' equity	27,375	32,610
Total liabilities and stockholders' equity	$ 362,520	$ 376,565

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION - Schedule of Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Accounts receivable
Contract asset:
Additions	$ 1,552	$ 1,545
Deductions	(2,282)	(1,989)
Accounts receivable
Contract asset:
Balance at Beginning of Period	2,391	2,010
Balance at End of Period	1,661	1,566
Sales to AG Distributor \| Accounts receivable
Contract asset:
Additions	0	1,241
Deductions	0	0
Sales to AG Distributor \| Deferred revenue
Contract liability:
Additions	4,826	1,241
Deductions	(3,011)	0
Sales to AG Distributor \| Accounts receivable
Contract asset:
Balance at Beginning of Period	194	0
Balance at End of Period	194	1,241
Sales to AG Distributor \| Deferred revenue
Contract liability:
Balance at Beginning of Period	2,681	0
Balance at End of Period	$ 4,496	$ 1,241

STOCK-BASED COMPENSATION PLANS - Narrative (Details) $ in Thousands		3 Months Ended
	Jun. 06, 2019 USD ($) shares	Mar. 31, 2026 USD ($) installment shares	Mar. 31, 2025 USD ($)	Dec. 31, 2025 shares
Class of Stock [Line Items]
Stock-based compensation expense \| $		$ 3,668	$ 2,187
Granted (in shares)		4,869,975
Number of options outstanding (in shares)		21,871,531		18,152,258
Unrecognized compensation costs, options \| $		$ 14,400
Unrecognized compensation costs, options, period for recognition (in years)		2 years 11 months 15 days
2014 Employee Stock Purchase Plan
Class of Stock [Line Items]
Purchase price at the end of offering period	85.00%
Offering period (in months)	6 months
Maximum employee subscription rate (as percent)	15.00%
Maximum employee subscription amount \| $	$ 25
Maximum number of shares per employee in any offering period (in shares)	1,500
Common stock, reserved for future issuance (in shares)		4,164,300		4,260,647
Number of shares issued (in shares)		96,347
Share-based Payment Arrangement, Option
Class of Stock [Line Items]
Expiration period (in years)		10 years
Share-based Payment Arrangement, Option \| Share-based Compensation Award, Tranche, First Anniversary of Grant Date
Class of Stock [Line Items]
Vesting percentage		100.00%
Share-based Payment Arrangement, Option \| Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting period		1 year
Vesting percentage		25.00%
Share-based Payment Arrangement, Option \| Share Based Compensation Award Tranche Two
Class of Stock [Line Items]
Vesting period		1 year
Number of equal quarterly installments \| installment		12
Share-based Payment Arrangement, Option \| Minimum
Class of Stock [Line Items]
Vesting period		12 months
Share-based Payment Arrangement, Option \| Maximum
Class of Stock [Line Items]
Vesting period		48 months
SARs
Class of Stock [Line Items]
Expiration period (in years)		10 years
SARs \| Share-based Compensation Award, Tranche, First Anniversary of Grant Date
Class of Stock [Line Items]
Vesting percentage		100.00%
SARs \| Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting period		1 year
Vesting percentage		25.00%
SARs \| Share Based Compensation Award Tranche Two
Class of Stock [Line Items]
Vesting period		1 year
Number of equal quarterly installments \| installment		12
SARs \| Minimum
Class of Stock [Line Items]
Vesting period		12 months
SARs \| Maximum
Class of Stock [Line Items]
Vesting period		48 months
Inducement Award Program
Class of Stock [Line Items]
Granted (in shares)		858,775
Number of options outstanding (in shares)		858,775
Inducement Award Program \| Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan)
Class of Stock [Line Items]
Number of options outstanding (in shares)		3,787,674		3,034,085
Unvested RSUs \| Share-based Compensation Award, Tranche, First Anniversary of Grant Date
Class of Stock [Line Items]
Vesting percentage		100.00%
Unvested RSUs \| Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting percentage		50.00%
Unvested RSUs \| Share Based Compensation Award Tranche Two
Class of Stock [Line Items]
Vesting period		6 months
Vesting percentage		25.00%
Award vesting grace period (in years)		1 year
Unvested RSUs \| Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date, Subjected To Individual Continued Service
Class of Stock [Line Items]
Vesting percentage		33.33%
Unvested RSUs \| Share-Based Payment Arrangement, Tranche Two, Second Anniversary After Grant Date, Subjected To Individual Continued Service
Class of Stock [Line Items]
Vesting percentage		33.33%
Unvested RSUs \| Share-Based Payment Arrangement, Tranche Three, Third Anniversary After Grant Date, Subjected To Individual Continued Service
Class of Stock [Line Items]
Vesting percentage		33.33%
Unvested RSUs \| Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date
Class of Stock [Line Items]
Vesting percentage		33.33%
Unvested RSUs \| Share-Based Payment Arrangement, Tranche Two, Following First Anniversary After Grant Date
Class of Stock [Line Items]
Vesting period		2 years
Vesting percentage		66.67%
Number of equal quarterly installments \| installment		8
Award vesting grace period (in years)		1 year
Restricted Stock Units (RSUs) And Performance Based Restricted Stock Units (PSUs)
Class of Stock [Line Items]
Unrecognized compensation costs, options, period for recognition (in years)		2 years 2 months 8 days
Unrecognized compensation costs, stock \| $		$ 12,700
Employees \| Share-based Payment Arrangement, Option \| Akebia Therapeutics, Inc. 2023 Stock Incentive Plan (the 2023 Plan) (replaces 2014 Plan)
Class of Stock [Line Items]
Granted (in shares)		4,011,200

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Revenues
Total revenues	$ 53,544	$ 57,336
Cost of goods sold
Cost of product and other revenue	12,290	7,625
Total cost of goods sold	12,290	7,625
Operating expenses:
Research and development	14,807	9,754
Selling, general and administrative	30,436	25,742
License	707	701
Total operating expenses	45,950	36,197
Income (loss) from operations	(4,696)	13,514
Other income (expense)
Interest expense	(4,691)	(7,770)
Other income	3	213
Change in fair value of warrant liability	456	155
Income (loss) before income taxes	(8,928)	6,112
Income tax expense	(126)	0
Net income (loss)	(9,054)	6,112
Comprehensive income (loss)	$ (9,054)	$ 6,112
Net income (loss) per share:
Basic (in dollars per share)	$ (0.03)	$ 0.03
Diluted (in dollars per share)	$ (0.03)	$ 0.03
Weighted average shares of common stock outstanding:
Basic (in shares)	267,046,755	235,497,720
Diluted (in shares)	267,046,755	241,602,853
Product revenue, net
Revenues
Total revenues	$ 51,992	$ 55,791
License, collaboration and other revenue
Revenues
Total revenues	$ 1,552	$ 1,545

LEASES

3 Months Ended

Mar. 31, 2026

Leases [Abstract]

LEASES

Cambridge Lease

Under the Cambridge Lease, the Company leases approximately 65,167 square feet of office, storage and laboratory space in Cambridge, Massachusetts. The term of the Cambridge Lease with respect to the 59,216 square feet of office and storage space expires on September 11, 2026. The term of the Cambridge Lease with respect to the 5,951 square feet of laboratory space was set to expire on September 11, 2026. On April 9, 2026, the Company extended the term of the Cambridge Lease with respect to the laboratory space through October 31, 2026. See Note 17, Subsequent Events, for further information.

The Cambridge Lease is non-cancelable and is classified as an operating lease. The Cambridge Lease does not contain residual value guarantees. In arriving at the operating lease liabilities, the Company applied incremental borrowing rates ranging from 6.65% to 6.94%, which were based on the remaining lease term at either the date of adoption of ASC 842, Leases, or the effective date of any subsequent lease term extensions. As of March 31, 2026, the remaining lease term for the Cambridge Lease was 0.45 years.

Operating lease costs were $1.2 million for each of the three months ended March 31, 2026 and 2025. Cash paid for amounts included in the measurement of operating lease liabilities was $1.5 million for each of the three months ended March 31, 2026 and 2025. The security deposit in connection with the Cambridge Lease is $1.7 million in the form of a letter of credit, which is included as restricted cash in prepaid expenses and other current assets in the accompanying unaudited condensed consolidated balance sheet as of March 31, 2026 and December 31, 2025.

Future Lease Commitments

Future commitments under the non-cancelable Cambridge Lease are as follows (in thousands):


	Operating Lease Commitments

2026	2,142
Total lease commitments	$	2,142
Less: present value adjustment	(15)
Current operating lease liabilities	$	2,127

Waltham Lease

On January 27, 2026, the Company entered into a lease agreement, or the Waltham Lease, with BP THIRD AVENUE LLC, a Delaware limited liability company, or the Landlord, pursuant to which the Company will lease an aggregate of approximately 43,474 square feet, consisting of 28,518 square feet of office space, or the Office Premises, and 14,956 square feet of laboratory space, or the Lab Premises, located in Waltham, Massachusetts. The Company intends to relocate its corporate headquarters to Waltham in September 2026.

Prior to commencement of the term of the Waltham Lease, the Landlord will perform certain items of work on the Office Premises, or the Landlord’s Office Premises Work, and the Lab Premises, or the Landlord’s Lab Premises Work, each pursuant to the Waltham Lease. The Landlord shall be solely responsible for the payment of all costs and expenses associated with completing such work, except as otherwise expressly set forth in the Waltham Lease.

The term of the Waltham Lease with respect to the Office Premises commences on the earlier to occur of (i) the date on which the Landlord’s Office Premises Work has been “substantially completed” and the Office Premises are “ready for occupancy” (each as defined in the Waltham Lease) or (ii) the date upon which the Company occupies all or any portion of the Office Premises, which is expected to be on or about September 1, 2026, or the Office Term Commencement Date. The initial

term of the Waltham Lease will be for an 84-calendar month-period commencing on the Office Term Commencement Date, unless extended or sooner terminated as provided in the Waltham Lease, with one five-year extension option available.

The Company’s annual rent for the Office Premises will start at $0.9 million and will increase at an additional $1.00 per square foot for each successive Rent Year (as defined in the Waltham Lease) until the end of the initial term. The Company’s annual rent for the Lab Premises will start at $1.0 million and will increase by approximately 3.0% for each successive Rent Year until the end of the initial term. The Waltham Lease requires a security deposit in the amount of $0.8 million in the form of an irrevocable letter of credit. In addition to rent, the Company is required to pay additional amounts for taxes, insurance, maintenance and other operating expenses.

STOCK-BASED COMPENSATION PLANS - Schedule of Stock-Based Compensation Expense in Consolidated Statement of Operations and Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 3,668	$ 2,187
Cost of goods sold
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	197	139
Research and development
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	1,056	467
Selling, general and administrative
Share-based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Total stock-based compensation	$ 2,415	$ 1,581

INDEBTEDNESS

3 Months Ended

Mar. 31, 2026

Debt Disclosure [Abstract]

INDEBTEDNESS

Entry into BlackRock Loan Facility

On January 29, 2024, or the Closing Date, the Company entered into the Agreement for the Provision of a Loan Facility, or the BlackRock Credit Agreement, with Kreos Capital VII (UK) Limited, or Kreos, which are funds and accounts managed by BlackRock Inc., collectively, BlackRock, and provides for a senior secured term loan facility in the aggregate principal amount of up to $55.0 million, or the Term Loan Facility. The Term Loan Facility was available in three tranches: (i) Tranche A — $37.0 million was funded on the Closing Date; (ii) Tranche B — $8.0 million was funded on April 19, 2024, or the Tranche B Closing Date; and (iii) Tranche C — $10.0 million was funded on February 3, 2025, or the Tranche C Closing Date, collectively the Term Loans.

On February 3, 2025, the Company and Kreos entered into a Second Amendment to the BlackRock Credit Agreement, or the Second Amendment, which, among other things, extended the expiry date of Tranche C from December 31, 2024 to the Tranche C Closing Date, or the Extended Tranche C. Tranche C was available subject to receipt of a certain amount of cumulative gross cash proceeds after the Closing Date in the form of equity or equity linked securities in one or more series of transactions. The terms of the Extended Tranche C are substantially similar to the terms of the original Tranche C, however, interest accrued on the Extended Tranche C as if it was advanced on December 31, 2024.

On the Closing Date, the Company received $34.5 million on Tranche A, after deducting debt issuance costs, fees and expenses. On the Tranche B Closing Date, the Company received $7.5 million, after deducting debt issuance costs, fees and

expenses. On the Tranche C Closing Date, the Company received $9.3 million, after deducting debt issuance costs, interest, fees and expenses.

The BlackRock Term Loan Facility had an initial maturity date of March 31, 2025, which was automatically extended to January 29, 2028, after the Company received FDA approval for Vafseo, or the BlackRock Maturity Date. The Company is required to make interest-only payments until December 31, 2026, or the BlackRock Interest Only Period, after which the Company will begin paying equal monthly principal on the first calendar day of each month. In the event of certain prespecified events, the repayment schedule will be accelerated.

The Term Loan Facility accrues interest at a floating annual rate equal to the sum of (i) the term Secured Overnight Financing Rate, or SOFR, for a tenor of one month (subject to a floor of 4.25% per annum) plus (ii) a margin of 6.75% per annum (subject to an overall cap of 15.00% per annum on the all-in interest rate). As of March 31, 2026, the Company's interest rate was 11.00%. During the three months ended March 31, 2026 and 2025, the Company recognized interest expense related to the BlackRock Credit Agreement of $2.2 million and $2.1 million, respectively.

During the continuance of any payment event of default under the BlackRock Credit Agreement, the interest rate on such overdue sum will automatically increase by an additional 3.0% per annum, and may be subject to an additional late fee of 2.0% of such overdue sum. The Term Loan Facility also includes transaction fees ranging from 1.00% to 1.25% of the draw down amount as well as exit fees of 0.75% of the amount funded to the relevant tranche.

If the Company prepays the outstanding loan prior to maturity, it will be required to pay a prepayment fee ranging from 1.0% to 4.0% of the amount prepaid.

As of March 31, 2026, future principal payments under the BlackRock Credit Agreement are as follows (in thousands):


Years ended December 31,	Principal Payments
2026	$	—
2027	50,558
2028	1,881
Total before unamortized discount and issuance costs	$	52,439
Less: unamortized discount and issuance costs	(3,549)
Total term loans	$	48,890

The BlackRock Term Loan Facility is secured by substantially all of the existing and after-acquired assets of the Company, including intellectual property. The BlackRock Credit Agreement requires the Company to (i) maintain a minimum aggregate cash balance of $15.0 million in one or more controlled accounts or (ii) trailing twelve-month revenue of $150.0 million, both of which are measured monthly. The BlackRock Credit Agreement contains certain representations and warranties, affirmative and negative covenants that limit the Company's ability to engage in specified types of transactions and other provisions typical within a credit agreement. If an event of default occurs and is continuing under the BlackRock Credit Agreement, BlackRock is entitled to take enforcement action, including acceleration of amounts due and it could limit the Company's ability to make certain payments under the Vifor Termination Agreement (as defined below).

On July 10, 2024, in connection with the Termination and Settlement Agreement entered into between the Company and CSL Vifor (as defined below), or the Vifor Termination Agreement, the Company and Kreos entered into a First Amendment to the BlackRock Credit Agreement, which amended certain provisions of the BlackRock Credit Agreement. See Note 8, Liability Related to Settlement Royalties, Working Capital Fund Liability and Liability Related to Sale of Future Royalties, for further information on the Vifor Termination Agreement.

Warrants

On the Closing Date, Kreos Capital VII Aggregator SCSp, an affiliate of Kreos, or the Warrant Holder, received a warrant to purchase 3,076,923 shares of the Company’s common stock, at an exercise price per share of $1.30, or the Initial Warrant. On the Tranche C Closing Date, the Company issued the Warrant Holder an additional warrant to purchase 1,153,846 shares of the Company’s common stock at an exercise price per share of $1.30, or the Tranche C Warrant. Each warrant is exercisable for eight years from the date of issuance.

On July 21, 2025, the Warrant Holder exercised its option to purchase 2,115,384 shares of the Company's common stock under the Initial Warrant on a cashless basis at an exercise price per share of $1.30. A cashless exercise allows the Warrant Holder to convert the warrants into shares of the Company's common stock without the need for a cash payment. Instead of paying cash upon exercise, the Warrant Holder received a reduced number of shares based on a predetermined formula. On

July 23, 2025, as a result of the cashless exercise, the Company issued 1,408,588 shares of common stock to the Warrant Holder under the Initial Warrant.

The Initial Warrant and the Tranche C Warrant are liabilities classified under ASC 815, Derivatives and Hedging, as they could potentially require net cash settlement outside of the Company’s control. The Initial Warrant and the Tranche C Warrant are measured at fair value each reporting period and when a warrant is exercised, with the changes in fair value presented within the unaudited condensed consolidated statements of operations and comprehensive income (loss). The fair value of the warrant liability was $2.5 million and $3.0 million as of March 31, 2026 and December 31, 2025, respectively. See Note 3, Fair Value Measurements, for information on the fair value determination.

Other Agreements Accounted for as Debt

The Company has a liability related to settlement royalties and a Working Capital Fund liability with Vifor (International) Ltd. (now a part of CSL Limited), or CSL Vifor, and a liability related to the sale of future royalties, which are each accounted for as debt arrangements. See Note 8, Liability Related to Settlement Royalties, Working Capital Fund Liability and Liability Related to Sale of Future Royalties, for further information.

- 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 815
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 8A
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480434/815-10-50-8A

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 235
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-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
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-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 6
-Subparagraph (b)
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-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Paragraph 6
-Subparagraph (a)
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Reference 6: http://www.xbrl.org/2003/role/disclosureRef
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Reference 7: http://www.xbrl.org/2003/role/disclosureRef
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Reference 8: http://www.xbrl.org/2003/role/disclosureRef
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Reference 9: http://www.xbrl.org/2003/role/disclosureRef
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Reference 10: http://www.xbrl.org/2003/role/disclosureRef
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-Subparagraph (a)
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Reference 11: http://www.xbrl.org/2003/role/disclosureRef
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Reference 12: http://fasb.org/us-gaap/role/ref/legacyRef
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-URI https://asc.fasb.org/470/tableOfContent

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
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-Name Accounting Standards Codification
-Section 45
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482925/835-30-45-2

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
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Reference 15: http://www.xbrl.org/2003/role/disclosureRef
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Reference 17: http://www.xbrl.org/2003/role/disclosureRef
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Reference 18: http://www.xbrl.org/2003/role/disclosureRef
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Reference 19: http://www.xbrl.org/2003/role/disclosureRef
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Reference 20: http://www.xbrl.org/2003/role/disclosureRef
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+ Details

SEGMENT INFORMATION

3 Months Ended

Mar. 31, 2026

Segment Reporting [Abstract]

SEGMENT INFORMATION

The Company operates as one operating segment focused on developing and commercializing innovative therapeutics primarily in the U.S. The accounting policies of the segment are the same as those described in Note 2, Summary of Significant Accounting Policies.

The determination of a single business segment is consistent with the consolidated financial information regularly reviewed by the chief executive officer, who is the Company's chief operating decision maker, or CODM, in assessing segment performance and deciding how to allocate resources on a consolidated basis.

The CODM makes decisions on resource allocation, assesses performance of the business, and monitors budget versus actual results using income from operations. Net income is also a measure that is considered in monitoring budget versus actual results. The measure of segment assets is reported on the consolidated balance sheets as total consolidated assets.

The following table presents information about reported segment revenues, segment profit and significant segment expenses for the three months ended March 31, 2026 and 2025:


	Three Months Ended March 31,
	2026		2025
Revenues	$	53,544	$	57,336
Less:
Direct cost of product and other revenue	10,033		5,059
Panion royalty	2,257		2,566


Research and development	14,807		9,754
Selling, general and administrative	30,436		25,742
License	707		701

Income (loss) from operations	(4,696)		13,514

Other income (expense)
Interest expense	(4,691)		(7,770)
Other income	3		213
Change in fair value of warrant liability	456		155


Income (loss) before income taxes	(8,928)		6,112
Income tax expense	(126)		—
Net income (loss)	$	(9,054)	$	6,112

- 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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 21
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-21

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-31

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
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-Section 50
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-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482810/280-10-50-15

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Topic 280
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-Name Accounting Standards Codification
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+ Details

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION - Narrative (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Product revenue, net
Disaggregation of Revenue [Line Items]
Accounts receivable, net	$ 60.9	$ 44.4

- 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

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+ Details

NATURE OF BUSINESS (Details) $ in Thousands	Mar. 31, 2026 USD ($) product	Dec. 31, 2025 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of commercial products \| product	2
Cash and cash equivalents \| $	$ 162,644	$ 184,844

LICENSE, COLLABORATION AND OTHER REVENUE (Tables)

3 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Schedule of Revenues Recognized from License, Collaboration and Other Significant Agreements

The Company recognized the following revenue from its license, collaboration and other revenue agreements (in thousands):


		Three Months Ended March 31,
Entity	Description	2026		2025
Medice	License and royalties related to the sale of Vafseo in the EU	$	32	$	7
TPC	License and Product Supply of Vafseo in Japan	341		369
JT and Torii	License and royalties related to the sale of Riona in Japan	1,179		1,169
Total license and other revenue		$	1,552	$	1,545

Schedule of Changes in Contract Assets and Liabilities

The following tables present changes in the Company’s contract assets and liabilities related to the Company's sales to its AG Distributor (in thousands):


	Three Months Ended March 31, 2026
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable	$	194	$	—	$	—	$	194
Contract liabilities:
Deferred revenue	$	2,681	$	4,826	$	(3,011)	$	4,496

	Three Months Ended March 31, 2025
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable	$	—	$	1,241	$	—	$	1,241
Contract liabilities:
Deferred revenue	$	—	$	1,241	$	—	$	1,241


	Three Months Ended March 31,
Revenue Recognized in the Period:	2026		2025
Deferred revenue — beginning of the period	$	3,011	$	—

The following tables present changes in the Company’s contract assets and liabilities related to license and other revenue (in thousands):


	Three Months Ended March 31, 2026
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract asset:
Accounts receivable(1)	$	2,391	$	1,552	$	(2,282)	$	1,661



	Three Months Ended March 31, 2025
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable(1)	$	2,010	$	1,545	$	(1,989)	$	1,566

(1) Excludes accounts receivable related to amounts due to the Company from product sales of Auryxia and Vafseo which are included in the accompanying unaudited condensed consolidated balance sheets as of March 31, 2026 and 2025.

Schedule of Revenue Recognized Resulting from Changes in Contract Assets and Contract Liabilities

The Company recognized the following revenues as a result of changes in the contract asset and contract liability balances in the respective periods (in thousands):


	Three Months Ended March 31,
Revenue Recognized in the Period:	2026		2025
Deferred revenue — beginning of the period	$	—	$	—

NET INCOME (LOSS) PER SHARE - Schedule of Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Numerator
Net income (loss)	$ (9,054)	$ 6,112
Denominator
Denominator for basic net income (loss) per share - weighted average outstanding shares of common stock (in shares)	267,046,755	235,497,720
Effect of potential dilutive securities:
Denominator for diluted net income (loss) per share - weighted average outstanding shares of common stock and assumed conversions (in shares)	267,046,755	241,602,853
Earnings per share:
Basic net income (loss) per share (in dollars per share)	$ (0.03)	$ 0.03
Diluted net income (loss) per share (in dollars per share)	$ (0.03)	$ 0.03
Dilutive effect of common stock options and SARs
Effect of potential dilutive securities:
Dilutive effect (in shares)	0	2,490,510
Dilutive effect of RSUs
Effect of potential dilutive securities:
Dilutive effect (in shares)	0	2,230,747
Dilutive effect of warrants
Effect of potential dilutive securities:
Dilutive effect (in shares)	0	1,382,510
Dilutive effect of ESPP
Effect of potential dilutive securities:
Dilutive effect (in shares)	0	1,366

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION - Schedule of Product Revenue Allowance and Provision Categories (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 77,093	$ 23,604
Current provisions related to sales in current year	21,887	20,914
Adjustments related to prior year sales	(1,457)	305
Credits/payments made	(14,960)	(10,356)
Ending balance	82,563	34,467
Chargebacks and Discounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	1,153	1,436
Current provisions related to sales in current year	1,458	380
Adjustments related to prior year sales	26	69
Credits/payments made	(1,639)	(1,389)
Ending balance	998	496
Rebates, Fees and Other Deductions
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	72,589	15,726
Current provisions related to sales in current year	20,270	20,147
Adjustments related to prior year sales	(1,483)	400
Credits/payments made	(12,449)	(8,822)
Ending balance	78,927	27,451
Product Returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	3,351	6,442
Current provisions related to sales in current year	159	387
Adjustments related to prior year sales	0	(164)
Credits/payments made	(872)	(145)
Ending balance	$ 2,638	$ 6,520

GOODWILL	3 Months Ended
GOODWILL	Mar. 31, 2026
Goodwill and Intangible Assets Disclosure [Abstract]
GOODWILL	GOODWILLAs of each of March 31, 2026 and December 31, 2025, the Company had goodwill of $59.0 million recorded in connection with the December 2018 merger with Keryx. The Company has not identified any goodwill impairment to date.

NATURE OF BUSINESS	3 Months Ended
NATURE OF BUSINESS	Mar. 31, 2026
Organization, Consolidation and Presentation of Financial Statements [Abstract]
NATURE OF BUSINESS	NATURE OF BUSINESS Organization Akebia Therapeutics, Inc., referred to as Akebia or the Company, was incorporated in the State of Delaware in 2007 and became a public company in 2014. Akebia is a fully integrated commercial-stage biopharmaceutical company focused on developing and commercializing innovative therapeutics. The Company has two products approved by the Food and Drug Administration, or FDA, in the United States, or U.S. Vafseo® (vadadustat) is an oral hypoxia-inducible factor prolyl hydroxylase, or HIF-PH, inhibitor. Vafseo (vadadustat) Tablets were approved in the U.S. in March 2024 for the treatment of anemia due to chronic kidney disease, or CKD, in adults who have been receiving dialysis for at least three months. Vafseo entered the U.S. market in January 2025. Auryxia® (ferric citrate) is an orally administered medicine approved and marketed in the U.S. for two indications: (i) the control of serum phosphorus levels in adult patients with dialysis dependent chronic kidney disease, or DD-CKD, and (ii) the treatment of iron deficiency anemia, or IDA, in adult patients with non-dialysis dependent chronic kidney disease, or NDD-CKD. Auryxia lost exclusivity in the U.S. in March 2025. On March 11, 2026, Teva Pharmaceuticals Ltd. received approval for its Abbreviated New Drug Application for a generic version of Auryxia, which has subsequently entered the market. Vafseo is also approved for the treatment of symptomatic anemia associated with CKD in the European Economic Area, or EEA, the United Kingdom, or the UK, Switzerland, Australia, South Korea and Taiwan in adult patients on chronic maintenance dialysis and in Japan for adult dialysis-dependent and non-dialysis patients. Vafseo is marketed and sold by the Company's collaboration partners in certain countries. Ferric citrate is also approved in Japan, and is marketed and sold by the Company's collaboration partner, as an oral treatment for the improvement of hyperphosphatemia in patients with CKD, including DD-CKD and NDD-CKD, and for the treatment of adult patients with IDA under the trade name Riona (ferric citrate hydrate). Since its inception, the Company has devoted most of its resources to research and development, or R&D, including its preclinical and clinical development activities, commercializing Auryxia and Vafseo and providing general and administrative support for these operations. The Company's mid-stage rare kidney disease pipeline assets, praliciguat and AKB-097, are being evaluated to target areas of unmet need. The Company's early-stage pipeline assets include AKB-9090 and AKB-10108, which are HIF molecules. In addition, the Company continues to explore additional development opportunities to expand its pipeline and portfolio of novel therapeutics through both internal research and external innovation to leverage its fully integrated team. As of March 31, 2026, the Company had cash and cash equivalents of $162.6 million. Based on its current operating plan, the Company believes that its cash resources and the cash the Company expects to generate from product, royalty, supply and license revenues will be sufficient to fund its current operating plan through at least twelve months from the filing of this Quarterly Report on Form 10-Q, or Form 10-Q. However, if the Company’s operating performance deteriorates significantly from the levels expected in the Company’s operating plan, including if the Company does not achieve its future anticipated Vafseo revenue projections, it would affect the Company’s liquidity and its ability to continue as a going concern in the future. The Company expects to finance future cash needs through product and license, collaboration and other revenue, including royalties and revenue from supply agreements. In addition, the Company may seek to sell public or private equity, enter into new debt transactions, explore potential strategic transactions, consider other cash-generating or saving measures or a combination of these approaches or other strategic alternatives. There can be no assurance that the current operating plan will be achieved in the time frame anticipated by the Company or that its cash resources will fund its operating plan for the period of time anticipated by the Company, or that additional funding will be available on terms acceptable to the Company, or at all.

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Operating Activities:
Net income (loss)	$ (9,054)	$ 6,112
Adjustments to reconcile net income (loss) to net cash used in operating activities:
Depreciation	328	314
Bad debt expense	199	702
Change in fair value of warrant liability	(456)	(155)
Non-cash royalty revenue related to sale of future royalties	(341)	(369)
Non-cash interest expense	4,577	6,253
Non-cash operating lease expense	1,198	1,104
Write-down of inventory	3,216	163
Gain on the sale of property and equipment	0	(172)
Stock-based compensation expense	3,668	2,187
Changes in operating assets and liabilities:
Accounts receivable	(15,704)	(27,872)
Inventory	(2,540)	(4,953)
Prepaid expenses and other current assets	170	2,212
Other long-term assets	(749)	54
Accounts payable	(7,792)	(2,234)
Accrued expense and other current liabilities	2,035	2,771
Operating lease liabilities	(1,422)	(1,310)
Deferred revenue	1,815	1,241
Other long-term liabilities	(355)	365
Net cash used in operating activities	(21,207)	(13,587)
Investing Activities:
Purchases of equipment	(62)	(18)
Proceeds from the sale of property and equipment	0	172
Net cash provided by (used in) investing activities	(62)	154
Financing Activities:
Proceeds from the issuance of debt	0	10,000
Payments of issuance costs related to BlackRock Credit Agreement	0	(63)
Proceeds from issuance of common stock, net of issuance costs	0	64,907
Proceeds from issuance of stock under employee stock purchase plan	131	78
Proceeds from the exercise of stock options	20	482
Repayment of WCF liability	(492)	0
Repayment of liability related to settlement royalties	(585)	0
Repayment of term debt	0	(462)
Net cash provided by (used in) financing activities	(926)	74,942
Increase (decrease) in cash, cash equivalents and restricted cash	(22,195)	61,509
Cash, cash equivalents and restricted cash — beginning of period	186,543	53,550
Cash, cash equivalents and restricted cash — end of period	164,348	115,059
Non-cash financing activities
Issuance of warrants in connection with BlackRock Credit Agreement	0	2,199
Purchase of IPR&D asset included in accrued expenses and other current liabilities	$ 5,000	$ 0

STOCK-BASED COMPENSATION PLANS - Schedule of RSU and PSU Activity (Details) - Restricted Stock Units (RSUs) And Performance Based Restricted Stock Units (PSUs)	3 Months Ended
	Mar. 31, 2026 $ / shares shares
2014 Stock Incentive Plan
Number of Shares
Outstanding beginning balance (in shares) \| shares	330,622
Granted (in shares) \| shares	0
Vested (in shares) \| shares	(330,622)
Forfeited and canceled (in shares) \| shares	0
Outstanding ending balance (in shares) \| shares	0
Weighted Average Grant Date Fair Value
Outstanding beginning balance, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 0.63
Granted, weighted average grant date fair value (in dollars per share) \| $ / shares	0
Vested, weighted-average grant date fair value (in dollars per share) \| $ / shares	0.63
Forfeited and canceled, weighted average grant date fair value (in dollars per share) \| $ / shares	0
Outstanding ending balance, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 0
2023 Stock Incentive Plan
Number of Shares
Outstanding beginning balance (in shares) \| shares	5,992,607
Granted (in shares) \| shares	5,426,300
Vested (in shares) \| shares	(2,018,204)
Forfeited and canceled (in shares) \| shares	(321,217)
Outstanding ending balance (in shares) \| shares	9,079,486
Weighted Average Grant Date Fair Value
Outstanding beginning balance, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 2.09
Granted, weighted average grant date fair value (in dollars per share) \| $ / shares	1.41
Vested, weighted-average grant date fair value (in dollars per share) \| $ / shares	2.01
Forfeited and canceled, weighted average grant date fair value (in dollars per share) \| $ / shares	1.80
Outstanding ending balance, weighted average grant date fair value (in dollars per share) \| $ / shares	$ 1.71

UNAUDITED CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2026	Dec. 31, 2025
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Preferred stock, authorized (in shares)	25,000,000	25,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001
Common stock, authorized (in shares)	350,000,000	350,000,000
Common stock, issued (in shares)	267,898,415	265,424,818
Common stock, outstanding (in shares)	267,898,415	265,424,818

INVENTORIES (Tables)

3 Months Ended

Mar. 31, 2026

Inventory Disclosure [Abstract]

Schedule of Components Inventory

Inventories consists of the following (in thousands):


	March 31, 2026		December 31, 2025
Inventories, current:
Work-in-process	$	7,890	$	12,651
Finished goods	5,106		2,959
Inventories, current	$	12,996	$	15,610
Long-term inventories included in other long-term assets:
Raw materials	50		50
Work-in-process	54,418		57,290
Finished goods	1,592		1,789
Inventories, long-term	$	56,060	$	59,129
Total inventories	$	69,056	$	74,739

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)

3 Months Ended

Mar. 31, 2026

Accounting Policies [Abstract]

Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash


Reconciliation of cash, cash equivalents and restricted cash (in thousands)	March 31, 2026		December 31, 2025
Cash and cash equivalents	$	162,644	$	184,844
Restricted cash	1,704		1,699
Total cash, cash equivalents and restricted cash	$	164,348	$	186,543

Schedule of Reconciliation of Cash, Cash Equivalents, and Restricted Cash


Reconciliation of cash, cash equivalents and restricted cash (in thousands)	March 31, 2026		December 31, 2025
Cash and cash equivalents	$	162,644	$	184,844
Restricted cash	1,704		1,699
Total cash, cash equivalents and restricted cash	$	164,348	$	186,543

Schedule of Allowance for Credit Losses

The following table summarizes the activity related to the Company's allowance for credit losses (in thousands):


	Three Months Ended March 31,
	2026		2025
Beginning balance	$	2,691	$	1,212
Provision for bad debts	199		702

Ending balance	$	2,889	$	1,914

LICENSE, COLLABORATION AND OTHER REVENUE

3 Months Ended

Mar. 31, 2026

Organization, Consolidation and Presentation of Financial Statements [Abstract]

LICENSE, COLLABORATION AND OTHER REVENUE

The Company recognized the following revenue from its license, collaboration and other revenue agreements (in thousands):


		Three Months Ended March 31,
Entity	Description	2026		2025
Medice	License and royalties related to the sale of Vafseo in the EU	$	32	$	7
TPC	License and Product Supply of Vafseo in Japan	341		369
JT and Torii	License and royalties related to the sale of Riona in Japan	1,179		1,169
Total license and other revenue		$	1,552	$	1,545

The following tables present changes in the Company’s contract assets and liabilities related to license and other revenue (in thousands):


	Three Months Ended March 31, 2026
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract asset:
Accounts receivable(1)	$	2,391	$	1,552	$	(2,282)	$	1,661



	Three Months Ended March 31, 2025
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable(1)	$	2,010	$	1,545	$	(1,989)	$	1,566

The Company recognized the following revenues as a result of changes in the contract asset and contract liability balances in the respective periods (in thousands):


	Three Months Ended March 31,
Revenue Recognized in the Period:	2026		2025
Deferred revenue — beginning of the period	$	—	$	—

During each of the three months ended March 31, 2026 and 2025, the Company recognized no revenue from performance obligations satisfied in previous periods.

Medice License Agreement

On May 24, 2023, or the Medice Effective Date, the Company and MEDICE Arzneimittel Pütter GmbH & Co. KG, or Medice, entered into a License Agreement, or the Medice License Agreement, pursuant to which the Company granted to Medice an exclusive license to develop and commercialize Vafseo for the treatment of anemia in adult patients with CKD in the EEA, the UK, Switzerland and Australia, or collectively, the Medice Territory.

Under the Medice License Agreement, the Company received an up-front payment of $10.0 million and is eligible to receive the following payments:

(i) commercial milestone payments up to an aggregate of $100.0 million, and

(ii) tiered royalties ranging from 10% to 30% of Medice's annual net sales of Vafseo in the Medice Territory, subject to reduction in certain circumstances.

The royalties will expire on a country-by-country basis upon the latest to occur of (a) the date of expiration of the last-to-expire valid claim of any Company, Medice or joint patent that covers Vafseo in such country in the Medice Territory, (b) the date of expiration of data or regulatory exclusivity for Vafseo in such country in the Medice Territory and (c) the date that is twelve years from first commercial sale of Vafseo in such country in the Medice Territory.

Under the Medice License Agreement, the Company retains the right to develop Vafseo for non-dialysis patients with anemia due to CKD in the Medice Territory. If the Company develops Vafseo for non-dialysis patients and Vafseo receives marketing approval in the Medice Territory, Medice will commercialize Vafseo for both indications in the Medice Territory. In this instance, the Company would receive 70% of the net product margin of any sales of Vafseo in the non-dialysis patient population, unless Medice requests to share the cost of the development necessary to gain approval to market Vafseo for non-dialysis patients in the Medice Territory and the parties agree on alternative financial terms. If the Company develops Vafseo for non-dialysis patients, the Company has determined that the activities under the Medice License Agreement represent joint operating activities in which both parties are active participants and of which both parties are exposed to significant risks and rewards that are dependent on the success of the activities. Accordingly, if the Company develops Vafseo for non-dialysis patients, the Company will account for the joint activities in accordance with ASC No. 808, Collaborative Arrangements, or ASC 808. Additionally, the Company has determined that in the context of the development of Vafseo for non-dialysis patients, Medice does not represent a customer as contemplated by ASC 606. As a result, the activities conducted pursuant to development activities for Vafseo for non-dialysis patients will be accounted for as a component of the related expense in the period incurred.

The Medice License Agreement expires on the date of expiration of all payment obligations due thereunder with respect to Vafseo in the last country in the Medice Territory, unless earlier terminated in accordance with the terms of the Medice License Agreement. Either party may, subject to a cure period, terminate the Medice License Agreement in the event of the other party's uncured material breach. Medice has the right to terminate the Medice License Agreement in its entirety for convenience upon twelve months' prior written notice delivered on or after the date that is twelve months after the Medice Effective Date.

The Company evaluated the elements of the Medice License Agreement in accordance with the provisions of ASC 606 and concluded Medice is a customer. The Company identified one performance obligation in connection with its obligations under the Medice License Agreement, which is the license, or License Performance Obligation. The transaction price at inception was comprised of the up-front payment of $10.0 million, of which the Company received $8.6 million during the quarter ended June 30, 2023. The remaining $1.4 million was withheld by the German Federal Tax Office and was received during the three months ended March 31, 2025.

Pursuant to the terms of the Medice License Agreement, the up-front payment of $10.0 million is non-refundable and non-creditable against any other amount due to the Company and was allocated to the License Performance Obligation, which was satisfied as of the Medice Effective Date. As such, the Company recognized the $10.0 million up-front payment as license, collaboration and other revenue in the unaudited condensed consolidated statements of operations and comprehensive loss during the year ended December 31, 2023.

In accordance with ASC 606, the Company will recognize sales-based royalties and milestone payments at the later of when the performance obligation is satisfied or the related sales occur. During each of the three months ended March 31, 2026 and 2025, the Company recognized immaterial revenue from Medice royalties. As of March 31, 2026, there were $0.1 million in contract assets, and no accounts receivable, payables or deferred revenue in connection with the Medice License Agreement.

Supply of Drug Product to Medice

On September 13, 2024, the Company and Medice entered into a supply agreement, or the Medice Supply Agreement, under which the Company supplies Vafseo drug product to Medice for commercial and developmental use in the Medice Territory. The Company recognizes revenue under this arrangement when risk of loss passes to Medice, delivery has occurred, and Medice has accepted the product. The Company did not recognize any revenue under the Medice Supply Agreement during the three months ended March 31, 2026 and 2025. As of March 31, 2026, there were no accounts receivable, contract assets, payables or deferred revenue in connection with the Medice Supply Agreement.

Supply of Drug Substance to Medice

On November 12, 2025, the Company and Medice entered into Amendment #1 to the License Agreement, or the Medice Amendment. Pursuant to the Medice Amendment, the Company agreed to supply vadadustat drug substance to Medice pursuant to the terms of a supply agreement dated concurrently with the Medice Amendment and granted Medice the right to manufacture Vafseo tablets using the vadadustat drug substance to be supplied by the Company. In addition, the Medice Amendment provides that any know-how or patent rights arising out of Medice’s manufacture of Vafseo tablets will be owned by the Company.

The Company did not recognize any revenue related to the supply of vadadustat drug substance to Medice during the three months ended March 31, 2026 and 2025.

TPC Collaboration Agreement

On December 11, 2015, the Company and TPC entered into the TPC Agreement, providing TPC with exclusive development and commercialization rights to Vafseo in the TPC Territory, which was amended effective as of December 2, 2022. In addition, the Company supplies Vafseo to TPC for both clinical and commercial use in the TPC Territory. In February 2021, the Company entered into the Royalty Agreement with HCR, whereby the Company sold its right to receive royalties and sales milestones under the TPC Agreement, subject to certain caps and other terms and conditions. See Note 8, Liability Related to Settlement Royalties, Working Capital Fund Liability and Liability Related to Sale of Future Royalties, for additional information and Note 12, License, Collaboration and Other Revenue, of the Notes to the Consolidated Financial Statements in the 2025 Form 10-K for a more detailed description of the TPC Agreement.

The Company evaluated the elements of the TPC Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, TPC, is a customer. The Company identified two performance obligations in connection with its material promises under the TPC Agreement as follows: (i) License, Research and Clinical Supply Performance Obligation and (ii) Rights to Future Know-How Performance Obligation.

The transaction price was comprised of: (i) the up-front payment of $20.0 million, (ii) the cost for the Phase 2 studies of $20.5 million, (iii) the cost of all clinical supply provided to TPC for the Phase 3 studies, (iv) $10.0 million in development milestones

received, (v) $25.0 million in regulatory milestones received and (vi) $9.0 million in royalties from net sales of Vafseo. The Company re-evaluates the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. As of March 31, 2026, all development milestones and $25.0 million in regulatory milestones have been achieved. No other regulatory milestones or commercial milestones have been assessed as probable and have been fully constrained until the period in which they are achieved.

The Company allocates the transaction price to each performance obligation based on the Company’s best estimate of the relative standalone selling price. The Company developed a best estimate of the standalone selling price for the Rights to Future Know-How Performance Obligation primarily based on the likelihood that additional intellectual property covered by the license conveyed will be developed during the term of the arrangement and determined it is immaterial. As such, the Company did not develop a best estimate of standalone selling price for the License, Research and Clinical Supply Performance Obligation and allocated the entire transaction price to this performance obligation.

Revenue for the License, Research and Clinical Supply Performance Obligation for the TPC Agreement is being recognized using a proportional performance method, for which all deliverables have been completed. The Company recognizes any revenue from TPC royalties in the period in which the sales occur. The Company recognized revenue from TPC royalties of $0.3 million and $0.4 million during the three months ended March 31, 2026 and 2025, respectively. As noted above, in February 2021, the Company entered into the Royalty Agreement, whereby the Company sold its right to receive these royalties and sales milestones under the TPC Agreement, subject to certain caps and other conditions. See Note 8, Liability Related to Settlement Royalties, Working Capital Fund Liability and Liability Related to Sale of Future Royalties, for additional information. The revenue is classified as collaboration, license and other revenue in the accompanying unaudited condensed consolidated statements of operations and comprehensive income (loss). As of March 31, 2026, there were no accounts receivable, payables or deferred revenue and $0.3 million in contract assets recorded in connection with the TPC Agreement.

Supply of Drug Product to TPC

On July 15, 2020, the Company and TPC entered into a supply agreement, or the TPC Supply Agreement, under which the Company supplies Vafseo drug product to TPC for commercial use in Japan and certain other Asian countries, as contemplated by the TPC Agreement. See Note 12, License, Collaboration and Other Revenue, of the Notes to the Consolidated Financial Statements in the 2025 Form 10-K for a more detailed description of this supply agreement.

The Company does not recognize revenue under this arrangement until risk of loss on the drug product passes to TPC and delivery has occurred and TPC has accepted the product. The Company recognized no revenue under the TPC Supply Agreement during each of the three months ended March 31, 2026 and 2025. As of March 31, 2026, there were no accounts receivable, deferred revenue or other current liabilities relating to the TPC Supply Agreement.

JT and Torii Sublicense Agreement

The Company has an Amended and Restated Sublicense Agreement, which was amended in June 2013, with JT and Torii, or the JT and Torii Sublicense Agreement, under which JT and Torii obtained the exclusive sublicense rights for the development and commercialization of ferric citrate hydrate in Japan. JT and Torii are responsible for the future development and commercialization costs in Japan. See Note 12, License, Collaboration and Other Revenue, of the Notes to the Consolidated Financial Statements in the 2025 Form 10-K for a more detailed description of this sublicense agreement.

The Company evaluated the elements of the JT and Torii Sublicense Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, JT and Torii, is a customer. The Company identified two performance obligations in connection with its obligations under the JT and Torii Sublicense Agreement: (i) License and Supply Performance Obligation and (ii) Rights to Future Know-How Performance Obligation. The Company developed a best estimate of the standalone selling price for the Rights to Future Know-How Performance Obligation primarily based on the likelihood that additional intellectual property covered by the license conveyed will be developed during the term of the arrangement and determined it immaterial. As such, the Company allocated the entire transaction price to the License and Supply Performance Obligation.

The Company recognized license revenue of $1.2 million during each of the three months ended March 31, 2026 and 2025, related to royalties earned on net sales of Riona in Japan. The Company records the associated mid-single digit percentage of net sales royalty expense due to Panion, the licensor of Riona, in the same period as the royalty revenue from JT and Torii is recorded. As of March 31, 2026, there was $1.2 million in accounts receivables relating to the JT and Torii Sublicense Agreement.

FAIR VALUE MEASUREMENTS (Tables)

3 Months Ended

Mar. 31, 2026

Fair Value Disclosures [Abstract]

Schedule of Assets Measured or Disclosed at Fair Value on Recurring Basis

The tables below present certain assets and liabilities measured at fair value categorized by the level of input used in the valuation of each asset and liability (in thousands):


	March 31, 2026
	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	135,983	$	—	$	—	$	135,983
Long-term liability:
Warrant liability	$	—	$	2,524	$	—	$	2,524

	December 31, 2025
	Level 1		Level 2		Level 3		Total Fair Value
Cash equivalents:
Money market funds	$	172,689	$	—	$	—	$	172,689
Long-term liability:
Warrant liability	$	—	$	2,980	$	—	$	2,980

UNAUDITED CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS’ EQUITY (DEFICIT) - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2024		224,848,992
Beginning balance at Dec. 31, 2024	$ (49,185)	$ 2	$ 1,629,167	$ 6	$ (1,678,360)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs (in shares)		34,437,364
Issuance of common stock, net of issuance costs	64,907		64,907
Proceeds from sale of stock under employee stock purchase plan (in shares)		93,362
Proceeds from sale of stock under employee stock purchase plan	78		78
Exercise of options (in shares)		604,325
Exercise of options	482		482
Stock-based compensation expense	2,187		2,187
Restricted stock unit vesting (in shares)		1,660,547
Net income (loss)	6,112				6,112
Ending balance (in shares) at Mar. 31, 2025		261,644,590
Ending balance at Mar. 31, 2025	$ 24,581	$ 2	1,696,821	6	(1,672,248)
Beginning balance (in shares) at Dec. 31, 2025	265,424,818	265,424,818
Beginning balance at Dec. 31, 2025	$ 32,610	$ 2	1,716,307	6	(1,683,705)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Proceeds from sale of stock under employee stock purchase plan (in shares)		96,347
Proceeds from sale of stock under employee stock purchase plan	$ 131		131
Exercise of options (in shares)	28,424	28,424
Exercise of options	$ 20		20
Stock-based compensation expense	3,668		3,668
Restricted stock unit vesting (in shares)		2,348,826
Net income (loss)	$ (9,054)				(9,054)
Ending balance (in shares) at Mar. 31, 2026	267,898,415	267,898,415
Ending balance at Mar. 31, 2026	$ 27,375	$ 2	$ 1,720,126	$ 6	$ (1,692,759)

SEGMENT INFORMATION - Narrative (Details)	3 Months Ended
SEGMENT INFORMATION - Narrative (Details)	Mar. 31, 2026 segment
Segment Reporting [Abstract]
Number of operating segments	1
Number of reportable segments	1

PRODUCT REVENUE AND PROVISIONS FOR VARIABLE CONSIDERATION (Tables)

3 Months Ended

Mar. 31, 2026

Revenue from Contract with Customer [Abstract]

Schedule of Product Revenues

The following table presents net product revenue for Vafseo and Auryxia (in thousands):


	Three Months Ended March 31,
Product	2026		2025
Vafseo	$	15,802	$	12,034
Auryxia(1)	36,190		43,757
Total product revenues	$	51,992	$	55,791

Schedule of Changes in Contract Assets and Liabilities

The following tables present changes in the Company’s contract assets and liabilities related to the Company's sales to its AG Distributor (in thousands):


	Three Months Ended March 31, 2026
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable	$	194	$	—	$	—	$	194
Contract liabilities:
Deferred revenue	$	2,681	$	4,826	$	(3,011)	$	4,496

	Three Months Ended March 31, 2025
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable	$	—	$	1,241	$	—	$	1,241
Contract liabilities:
Deferred revenue	$	—	$	1,241	$	—	$	1,241


	Three Months Ended March 31,
Revenue Recognized in the Period:	2026		2025
Deferred revenue — beginning of the period	$	3,011	$	—

The following tables present changes in the Company’s contract assets and liabilities related to license and other revenue (in thousands):


	Three Months Ended March 31, 2026
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract asset:
Accounts receivable(1)	$	2,391	$	1,552	$	(2,282)	$	1,661



	Three Months Ended March 31, 2025
	Balance at Beginning of Period		Additions		Deductions		Balance at End of Period
Contract assets:
Accounts receivable(1)	$	2,010	$	1,545	$	(1,989)	$	1,566

Schedule of Product Revenue Allowance and Provision Categories

Product revenue allowance and provision categories were as follows:


(in thousands)	Chargebacks and Discounts		Rebates, Fees and Other Deductions		Product Returns		Total
Balance at December 31, 2025	$	1,153	$	72,589	$	3,351	$	77,093
Current provisions related to sales in current year	1,458		20,270		159		21,887
Adjustments related to prior year sales	26		(1,483)		—		(1,457)
Credits/payments made	(1,639)		(12,449)		(872)		(14,960)
Balance at March 31, 2026	$	998	$	78,927	$	2,638	$	82,563

(in thousands)	Chargebacks and Discounts		Rebates, Fees and Other Deductions		Product Returns		Total
Balance at December 31, 2024	$	1,436	$	15,726	$	6,442	$	23,604
Current provisions related to sales in current year	380		20,147		387		20,914
Adjustments related to prior year sales	69		400		(164)		305
Credits/payments made	(1,389)		(8,822)		(145)		(10,356)
Balance at March 31, 2025	$	496	$	27,451	$	6,520	$	34,467

STOCK-BASED COMPENSATION PLANS - Schedule of Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2026	Dec. 31, 2025
Stock Options
Outstanding beginning balance (in shares)	18,152,258
Granted (in shares)	4,869,975
Exercised (in shares)	(28,424)
Expired (in shares)	(593,220)
Canceled and forfeited (in shares)	(529,058)
Outstanding ending balance (in shares)	21,871,531	18,152,258
Options exercisable at end of period (in shares)	10,605,986
Weighted Average Exercise Price
Outstanding beginning balance (in dollars per share)	$ 2.85
Granted (in dollars per share)	1.41
Exercised (in dollars per share)	0.71
Expired (in dollars per share)	5.77
Canceled and forfeited (in dollars per share)	1.78
Outstanding ending balance (in dollars per share)	2.48	$ 2.85
Options exercisable at end of period, weighted-average exercise price (in dollars per share)	$ 3.23
Weighted-Average Contractual Life (years)
Options outstanding, weighted-average remaining contractual life (in years)	7 years 7 months 2 days	6 years 11 months 19 days
Options exercisable at end of period, weighted-average remaining contractual life (in years)	6 years 14 days
Options outstanding, aggregate intrinsic value	$ 2,691	$ 3,690
Exercisable, aggregate intrinsic value	$ 2,059

COMMITMENTS AND CONTINGENCIES (Details) - USD ($) $ in Thousands			1 Months Ended					3 Months Ended			12 Months Ended
	Nov. 28, 2025	Feb. 10, 2021	Dec. 31, 2025	Sep. 30, 2025	Dec. 31, 2024	Jun. 30, 2021	Mar. 31, 2020	Mar. 31, 2026	Mar. 31, 2025	Jun. 30, 2021	Dec. 31, 2025	Dec. 31, 2024
Commitments And Contingencies [Line Items]
Research and development								$ 14,807	$ 9,754
Contract cost incurred in research and development activities								81,500
Supply Agreement, Patheon Inc.
Commitments And Contingencies [Line Items]
Purchase commitment, option for non-auto renewal, prior written notice period (in months)							18 months
Minimum purchase commitment								1,100
Siegfried Evionnaz SA
Commitments And Contingencies [Line Items]
Cost of purchased minimum quantity product								0
Excess firm purchase commitment charge								0			$ 800
STA Pharmaceutical Hong Kong Limited
Commitments And Contingencies [Line Items]
Excess firm purchase commitment charge								69,200
WuXi STA
Commitments And Contingencies [Line Items]
Excess firm purchase commitment charge								2,100
Purchase commitment, option to extend, prior notice period (in months)		18 months
Long-term purchase commitment, option to terminate, prior notice period (at least)		180 days
Panion & BF Biotech, Inc \| License Agreement
Commitments And Contingencies [Line Items]
Royalty payments								$ 2,300	$ 2,600
Cyclerion \| License Agreement
Commitments And Contingencies [Line Items]
Expiration period beginning with first commercial sale (in years)								10 years
Termination period, prior written notice (in days)								180 days
Cyclerion \| License Agreement \| Acquired Licenses
Commitments And Contingencies [Line Items]
Upfront payments										$ 3,000
Cyclerion \| License Agreement \| Acquired Licenses \| Research and Development Expense
Commitments And Contingencies [Line Items]
Upfront payments						$ 3,000
Cyclerion \| Cyclerion Amendment \| Acquired Licenses
Commitments And Contingencies [Line Items]
Upfront payments				$ 500	$ 1,250			$ 1,000
Contingent consideration				$ 500
Specified development and regulatory milestone payments, contingent on a product-by-product basis											197,500
Research and development			$ 1,000
Cyclerion \| Cyclerion Amendment \| Acquired Licenses \| Maximum
Commitments And Contingencies [Line Items]
Tiered royalties (as percent)								20.00%
Cyclerion \| Cyclerion Amendment \| Acquired Licenses \| Research and Development Expense
Commitments And Contingencies [Line Items]
Upfront payments												$ 1,250
Contingent consideration												$ 500
Q32 \| Q32 Asset Purchase Agreement
Commitments And Contingencies [Line Items]
Upfront payments	$ 12,800
Specified development and regulatory milestone payments, contingent on a product-by-product basis	94,500
Upfront payment	7,000
Additional upfront payment	$ 3,000							$ 3,000
Additional payment term	6 months
Development milestone payment	$ 2,000							$ 2,000
Commercial milestone payment	487,500
Asset acquisition, consideration transferred, transaction cost	$ 800
Charge for purchase of IPR&D asset											$ 12,800

CAPITAL STOCK (Details) - USD ($) $ / shares in Units, $ in Millions			3 Months Ended	16 Months Ended
	Apr. 22, 2025	Mar. 19, 2025	Mar. 31, 2026	Dec. 31, 2025	Jul. 23, 2025	Jul. 21, 2025	Feb. 28, 2025	Feb. 03, 2025	Sep. 03, 2024	Jan. 29, 2024
Class of Stock [Line Items]
Common stock, authorized (in shares)			350,000,000	350,000,000
Common stock, par value (in dollars per share)			$ 0.00001	$ 0.00001
Common stock, outstanding (in shares)			267,898,415	265,424,818
Common stock, issued (in shares)			267,898,415	265,424,818
Preferred stock, authorized (in shares)			25,000,000	25,000,000
Preferred stock, par value (in dollars per share)			$ 0.00001	$ 0.00001
Preferred stock, issued (in shares)			0	0
Preferred stock, outstanding (in shares)			0	0
Issuance and sale of equity securities									$ 75.0
Warrant to purchase common stock (in shares)					1,408,588	2,115,384	1,153,846	1,153,846		3,076,923
Exercise price (in dollars per share)						$ 1.30	$ 1.30	$ 1.30		$ 1.30
Warrant exercise period (in years)							8 years	8 years
Warrant purchased (in shares)						2,115,384
Warrants issued (in shares)						1,408,588
Vifor (International) Ltd. \| License
Class of Stock [Line Items]
Unregistered stock held by customer (in shares)			7,571,429
At-The-Market Sale Agreement, Authorized April 2022, Amended
Class of Stock [Line Items]
Number of shares sold in offering (in shares)			0	23,708,995
Sale of stock, consideration received, gross				$ 43.0
Aggregate net proceeds from offering				$ 42.2
Public Stock Offering
Class of Stock [Line Items]
Number of shares sold in offering (in shares)		25,000,000
Aggregate net proceeds from offering	$ 1.6	$ 46.5
Sale of stock, price per share (in dollars per share)		$ 2.00
Public Stock Offering - Underwriting Agreement
Class of Stock [Line Items]
Sale of stock, price per share (in dollars per share)		$ 1.88
Over-Allotment Option
Class of Stock [Line Items]
Number of shares sold in offering (in shares)	850,000	3,750,000
Underwriters allotment option, term (in days)		30 days

NET INCOME (LOSS) PER SHARE

3 Months Ended

Mar. 31, 2026

Earnings Per Share [Abstract]

NET INCOME (LOSS) PER SHARE

The following summarizes the calculation of net income (loss) per share:


	Three Months Ended March 31,
(Dollars in thousands, except per share amounts)	2026		2025
Numerator
Net income (loss)	$	(9,054)	$	6,112

Denominator
Denominator for basic net income (loss) per share - weighted average outstanding shares of common stock	267,046,755		235,497,720
Dilutive effect of common stock options and SARs	—		2,490,510
Dilutive effect of RSUs	—		2,230,747
Dilutive effect of warrants	—		1,382,510
Dilutive effect of ESPP	—		1,366
Denominator for diluted net income (loss) per share - weighted average outstanding shares of common stock and assumed conversions	267,046,755		241,602,853
Basic net income (loss) per share	$	(0.03)	$	0.03
Diluted net income (loss) per share	$	(0.03)	$	0.03

Potentially dilutive securities including common stock options, RSUs, SARs and warrants have been excluded from the calculation of diluted net loss per share as their effects would be anti-dilutive. For the three months ended March 31, 2026 in which the Company reported a net loss, the weighted average number of shares outstanding used to calculate both basic and

diluted net loss per share were the same. The shares in the table below were excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, due to their anti-dilutive effect:


			Three Months Ended March 31, 2026
Outstanding common stock options			21,236,218
SARs			635,313
Unvested RSUs			9,079,486

Warrants			2,115,385
Total			33,066,402