Akebia Therapeutics (AKBA) 10-Q 4 Aug 22 2022 Q2 Quarterly report Financial data

Cover Page

Cover Page - shares	6 Months Ended
	Jun. 30, 2022	Jul. 31, 2022
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Jun. 30, 2022
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, par value $0.00001 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		183,848,654
Amendment Flag	false
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q2
Current Fiscal Year End Date	--12-31
Entity Central Index Key	0001517022

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Current assets:
Cash and cash equivalents	$ 143,893	$ 149,800
Inventory	36,272	38,195
Accounts receivable, net	81,869	50,875
Prepaid expenses and other current assets	42,129	33,140
Total current assets	304,163	272,010
Property and equipment, net	6,035	6,754
Operating lease assets	31,494	33,852
Goodwill	55,053	55,053
Other intangible assets, net	90,106	108,127
Other assets	34,953	49,754
Total assets	521,804	525,550
Current liabilities:
Accounts payable	24,944	33,588
Accrued expenses and other current liabilities	91,284	104,456
Short-term deferred revenue	5,047	20,906
Current portion of refund liability to customer	14,247	0
Current portion of long-term debt	98,158	97,543
Total current liabilities	233,680	256,493
Deferred revenue, net of current portion	43,296	21,474
Operating lease liabilities, net of current portion	31,733	33,703
Derivative liability	1,110	1,820
Liability related to sale of future royalties, net	56,743	53,079
Refund liability to customer, net of current portion	26,053	0
Other non-current liabilities	66,889	82,525
Total liabilities	459,504	449,094
Commitments and contingencies (Note 13)
Stockholders' equity:
Preferred stock $0.00001 par value, 25,000,000 shares authorized; 0 shares issued and    outstanding at June 30, 2022 and December 31, 2021	0	0
Common stock $0.00001 par value; 350,000,000 shares authorized at June 30, 2022 and December 31, 2021; 183,704,654 and 177,000,963 shares issued and outstanding at June 30, 2022 and December 31, 2021, respectively	2	1
Additional paid-in capital	1,555,788	1,536,800
Accumulated other comprehensive loss	6	6
Accumulated deficit	(1,493,496)	(1,460,351)
Total stockholders' equity	62,300	76,456
Total liabilities and stockholders' equity	$ 521,804	$ 525,550

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Jun. 30, 2022	Dec. 31, 2021	Jun. 04, 2020
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	175,000,000
Common stock, issued (in shares)	183,704,654	177,000,963
Common stock, outstanding (in shares)	183,704,654	177,000,963

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenues:
Total revenues	$ 126,759	$ 52,913	$ 188,458	$ 105,217
Cost of goods sold:
Product	9,589	43,484	31,923	69,079
Amortization of intangibles	9,011	9,011	18,021	18,021
Total cost of goods sold	18,600	52,495	49,944	87,100
Operating expenses:
Research and development	26,027	37,214	69,860	77,825
Selling, general and administrative	32,807	41,651	77,134	82,979
License expense	892	894	1,580	1,590
Restructuring	14,531	0	14,531	0
Total operating expenses	74,257	79,759	163,105	162,394
Operating income (loss)	33,902	(79,341)	(24,591)	(144,277)
Other income (expense):
Interest expense	(5,037)	(4,962)	(10,099)	(9,768)
Other income	411	1,265	1,545	1,427
Net loss, basic	29,276	(83,038)	(33,145)	(152,618)
Net loss, diluted	$ 29,276	$ (83,038)	$ (33,145)	$ (152,618)
Net loss per share - basic (in dollars per share)	$ 0.16	$ (0.51)	$ (0.18)	$ (0.97)
Weighted-average number of common shares - basic (in shares)	183,597,766	161,329,990	181,609,452	157,596,143
Net loss per share - diluted (in dollars per share)	$ 0.15	$ (0.51)	$ (0.18)	$ (0.97)
Weighted-average number of common shares - diluted (in shares)	190,375,317	161,329,990	181,609,452	157,596,143
Comprehensive income (loss):
Net income (loss)	$ 29,276	$ (83,038)	$ (33,145)	$ (152,618)
Other comprehensive loss - unrealized loss on debt securities	0	(3)	0	(7)
Total comprehensive income (loss)	29,276	(83,041)	(33,145)	(152,625)
Product revenue, net
Revenues:
Total revenues	43,703	32,959	85,151	63,367
License, collaboration and other revenue
Revenues:
Total revenues	$ 83,056	$ 19,954	$ 103,307	$ 41,850

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Unrealized Gain/(Loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2020		148,074,085
Beginning balance at Dec. 31, 2020	$ 247,618	$ 1	$ 1,425,115	$ 13	$ (1,177,511)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs (in shares)		9,228,017
Issuance of common stock, net of    issuance costs	29,498	$ 1	29,497
Proceeds from sale of stock under employee stock purchase plan (in shares)		154,276
Proceeds from sale of stock under    employee stock purchase plan	367		367
Stock-based compensation expense	5,992		5,992
Restricted stock unit vesting (in shares)		1,063,711
Unrealized loss	(4)			(4)
Net income (loss)	(69,580)				(69,580)
Ending balance (in shares) at Mar. 31, 2021		158,520,089
Ending balance at Mar. 31, 2021	213,891	$ 2	1,460,971	9	(1,247,091)
Beginning balance (in shares) at Dec. 31, 2020		148,074,085
Beginning balance at Dec. 31, 2020	247,618	$ 1	1,425,115	13	(1,177,511)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss	(7)
Net income (loss)	(152,618)
Ending balance (in shares) at Jun. 30, 2021		169,651,423
Ending balance at Jun. 30, 2021	174,631	$ 2	1,504,752	6	(1,330,129)
Beginning balance (in shares) at Mar. 31, 2021		158,520,089
Beginning balance at Mar. 31, 2021	213,891	$ 2	1,460,971	9	(1,247,091)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs (in shares)		10,446,160
Issuance of common stock, net of    issuance costs	37,266		37,266
Stock-based compensation expense	6,515		6,515
Restricted stock unit vesting (in shares)		685,174
Unrealized loss	(3)			(3)
Net income (loss)	(83,038)				(83,038)
Ending balance (in shares) at Jun. 30, 2021		169,651,423
Ending balance at Jun. 30, 2021	$ 174,631	$ 2	1,504,752	6	(1,330,129)
Beginning balance (in shares) at Dec. 31, 2021	177,000,963	177,000,963
Beginning balance at Dec. 31, 2021	$ 76,456	$ 1	1,536,800	6	(1,460,351)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock, net of issuance costs (in shares)		4,404,600
Issuance of common stock, net of    issuance costs	7,178	$ 1	7,177
Proceeds from sale of stock under employee stock purchase plan (in shares)		191,146
Proceeds from sale of stock under    employee stock purchase plan	367		367
Stock-based compensation expense	4,536		4,536
Restricted stock unit vesting (in shares)		1,789,326
Net income (loss)	(62,421)				(62,421)
Ending balance (in shares) at Mar. 31, 2022		183,386,035
Ending balance at Mar. 31, 2022	$ 26,116	$ 2	1,548,880	6	(1,522,772)
Beginning balance (in shares) at Dec. 31, 2021	177,000,963	177,000,963
Beginning balance at Dec. 31, 2021	$ 76,456	$ 1	1,536,800	6	(1,460,351)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Unrealized loss	0
Net income (loss)	$ (33,145)
Ending balance (in shares) at Jun. 30, 2022	183,704,654	183,704,654
Ending balance at Jun. 30, 2022	$ 62,300	$ 2	1,555,788	6	(1,493,496)
Beginning balance (in shares) at Mar. 31, 2022		183,386,035
Beginning balance at Mar. 31, 2022	26,116	$ 2	1,548,880	6	(1,522,772)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation expense	6,841		6,841
Exercise of options (in shares)		142,440
Exercise of options	67		67
Restricted stock unit vesting (in shares)		176,179
Unrealized loss	0
Net income (loss)	$ 29,276				29,276
Ending balance (in shares) at Jun. 30, 2022	183,704,654	183,704,654
Ending balance at Jun. 30, 2022	$ 62,300	$ 2	$ 1,555,788	$ 6	$ (1,493,496)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	Jun. 30, 2022	Dec. 31, 2021
Statement of Stockholders' Equity [Abstract]
Common stock, par value (in dollars per share)	$ 0.00001	$ 0.00001

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Operating activities:
Net loss	$ (33,145)	$ (152,618)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	833	1,012
Amortization of intangibles	18,021	18,021
Amortization of premium/discount on investments	0	(15)
Non-cash interest expense related to sale of future royalties	4,428	4,427
Non-cash royalty revenue related to sale of future royalties	(764)	(116)
Non-cash collaboration revenue	(9,550)	0
Non-cash interest expense	916	539
Non-cash operating lease expense	(1,198)	(965)
Fair value step-up of inventory sold or written off	0	21,575
Write-down of inventory	7,430	5,425
Change in excess inventory purchase commitments	(773)	21,338
Stock-based compensation	11,453	12,506
Change in fair value of derivative liability	(710)	(490)
Changes in operating assets and liabilities:
Accounts receivable	(30,994)	(8,152)
Inventory	1,159	(35,710)
Prepaid expenses and other current assets	561	3,301
Other long-term assets	9,347	4,149
Accounts payable	(8,807)	(1,120)
Accrued expense	(18,625)	(15,706)
Operating lease liabilities	1,205	804
Deferred revenue	5,963	(12,092)
Other non-current liabilities	(9,030)	0
Net cash used in operating activities	(52,280)	(133,887)
Investing activities:
Purchase of equipment	(114)	(59)
Proceeds from the maturities of available for sale securities	0	40,000
Net cash (used in) provided by investing activities	(114)	39,941
Financing activities:
Proceeds from sale of future royalties, net	0	44,783
Proceeds from refund liabilities to customers	40,000	0
Proceeds from the issuance of common stock, net of issuance costs	7,102	66,696
Proceeds from the sale of stock under employee stock purchase plan	367	367
Proceeds from the exercise of stock options	67	0
Net cash provided by financing activities	47,536	111,846
(Decrease) increase in cash, cash equivalents, and restricted cash	(4,858)	17,900
Cash, cash equivalents, and restricted cash at beginning of the period	151,839	231,132
Cash, cash equivalents, and restricted cash at end of the period	146,981	249,032
Non-cash financing activities
Unpaid offering costs	$ 0	$ 68

Nature of Organization and Oper

Nature of Organization and Operations	6 Months Ended
	Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of Organization and Operations	Nature of Organization and Operations Akebia Therapeutics, Inc., referred to as Akebia or the Company, was incorporated in the State of Delaware in 2007. Akebia is a biopharmaceutical company with the purpose of bettering the lives of people impacted by kidney disease. The Company has one commercial product, Auryxia ® (ferric citrate), which is approved by the U.S. Food and Drug Administration, or FDA, and marketed for two indications in the United States: the control of serum phosphorus levels in adult patients with chronic kidney disease, or CKD, on dialysis, or DD-CKD, and the treatment of iron deficiency anemia, or IDA, in adult patients with CKD not on dialysis, or NDD-CKD. Ferric citrate is also approved and marketed in Japan as an oral treatment for IDA in adult patients for the improvement of hyperphosphatemia in such patients with DD-CKD and NDD-CKD under the trade name Riona (ferric citrate hydrate). Vadadustat, the Company’s lead investigational product candidate, is an investigational oral hypoxia-inducible factor prolyl hydroxylase, or HIF-PH, inhibitor designed to mimic the physiologic effect of altitude on oxygen availability. On March 29, 2022, the Company received a complete response letter, or CRL, from the FDA. The CRL provided that the FDA had completed its review of the Company's new drug application, or NDA, for vadadustat for the treatment of anemia due to CKD in adult patients and had determined that it could not approve the NDA in its present form. The Company held an end of review conference with the FDA and are in the process of determining next steps for a potential U.S. approval for vadadustat as a treatment of anemia due to CKD in patients on dialysis. On May 12, 2022, the Company received notice from its former collaboration partner, Otsuka Pharmaceutical Co. Ltd., or Otsuka, that Otsuka had elected to terminate the Collaboration and License Agreement dated December 18, 2016, or the Otsuka U.S. Agreement, and the Collaboration and License Agreement dated April 25, 2017, or the Otsuka International Agreement. On June 30, 2022, the Company and Otsuka entered into a Termination and Settlement Agreement, or the Termination Agreement, pursuant to which, among other things, the Company and Otsuka agreed to terminate the Otsuka U.S. Agreement and the Otsuka International Agreement as of June 30, 2022 (see Note 4 for further details). In October 2021, Otsuka submitted a Marketing Authorization Application, or MAA, for vadadustat for the treatment of anemia due to CKD in adult patients with DD-CKD and NDD-CKD to the European Medicines Agency, or EMA . In connection with the Termination Agreement, in July 2022, Otsuka filed a request with the EMA to transfer the MAA for vadadustat to the Company. Vadadustat is approved in Japan as a treatment for anemia due to CKD in both DD-CKD and NDD-CKD patients under the trade name Vafseo TM , and marketed and sold in Japan by Mitsubishi Tanabe Pharma Corporation, or MTPC. In addition, the Company continues to explore additional development opportunities to expand its pipeline and portfolio of novel therapeutics. Since inception, the Company has devoted most of its resources to research and development, including its preclinical and clinical development activities, commercializing Auryxia, and providing general and administrative support for these operations. The Company began recording revenue from the U.S. sales of Auryxia and revenue from sublicensing rights to Auryxia in Japan from the Company’s Japanese partners, Japan Tobacco, Inc. and its subsidiary Torii Pharmaceutical Co., Ltd., collectively JT and Torii, in December 2018. Additionally, following regulatory approval of vadadustat in Japan, the Company began recognizing royalty revenues from MTPC from the sale of Vafseo in August 2020. In February 2021, the Company entered into a royalty interest acquisition agreement with HealthCare Royalty Partners IV, L.P., or HCR, or the Royalty Agreement, whereby the Company sold its right to receive royalties and sales milestones under its Collaboration Agreement with MTPC, or the MTPC Agreement, subject to certain caps and other terms and conditions (see Note 6 for additional information). The Company has not generated a profit to date, and may never generate profits, from product sales. Vadadustat and the Company’s other potential product candidates are subject to long development cycles, and the Company may be unsuccessful in its efforts to develop, obtain marketing approval for or market vadadustat and its other potential product candidates. If the Company does not successfully commercialize Auryxia, vadadustat, if approved, or any other potential product candidate, it may be unable to achieve profitability. Going Concern The Company’s management completed its going concern assessment in accordance with Accounting Standards Codification, or ASC, 205-40, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern , or ASC 205-40. Pursuant to the requirements of ASC 205-40, the Company’s management must evaluate whether there are conditions or events, considered in the aggregate, that raise substantial doubt about the Company’s ability to continue as a going concern within one year after the date the financial statements are issued. This evaluation initially does not take into consideration the potential mitigating effect of management’s plans that have not been fully implemented as of the date the financial statements are issued. When substantial doubt exists under this methodology, the Company’s management evaluates whether the mitigating effect of its plans sufficiently alleviates substantial doubt about the Company’s ability to continue as a going concern. The mitigating effect of the Company’s plans, however, is only considered if both (1) it is probable that the plans will be effectively implemented within one year after the date that the financial statements are issued and (2) it is probable that the plans, when implemented, will mitigate the relevant conditions or events that raise substantial doubt about the entity’s ability to continue as a going concern within one year after the date that the financial statements are issued. As of June 30, 2022, the Company had cash and cash equivalents of approximately $143.9 million. The Company believes that its cash resources will be sufficient to allow the Company to fund its current operating plan through at least the next twelve months from the filing of this Quarterly Report on Form 10-Q. However, the Company's operating plan includes assumptions pertaining to cost avoidance measures and the reduction of overhead costs that would result from the planned amendment of certain contractual arrangements, including with certain supply and collaboration partners, and the reduction of certain infrastructure costs. Therefore, because these cost avoidance initiatives and certain other elements of the Company's operating plan are outside of its control, including the planned amendment of certain contractual arrangements, including with supply and collaboration partners, and the reduction of certain infrastructure costs, there is uncertainty as to whether the Company's cash resources will be adequate to support its operations for a period through at least the next twelve months from the date of issuance of these financial statements. In addition, on July 15, 2022, or the Effective Date, the Company entered into the Second Amendment and Waiver with BioPharma Credit PLC, or the Collateral Agent, BPCR Limited Partnership, as a Lender, and BioPharma Credit Investments V (Master) LP, as a Lender, or the Second Amendment and Waiver, which amends and waives certain provisions of the loan agreement entered on November 11, 2019, between the Company, with Keryx Biopharmaceuticals, Inc., or Keryx, as guarantor, and the Collateral Agent, as collateral agent and a lender, and BioPharma Credit Investments V (Master) LP as a lender, or the Loan Agreement, as amended by the First Amendment and Waiver among the Collateral Agent, the Lenders and the Company, dated February 18, 2022, or the First Amendment and Waiver. The Collateral Agent and the Lenders are collectively referred to as Pharmakon (see Note 11). Pursuant to the Second Amendment and Waiver, on the Effective Date, the Company made prepayments totaling $25.0 million together with a prepayment premium of $0.5 million plus all accrued and unpaid interest on such prepayments of principal to the Effective Date, and Pharmakon agreed to waive or modify certain covenants in the Loan Agreement (see Note 11). If an event of default occurs and is continuing under the Loan Agreement, the Collateral Agent is entitled to take enforcement action, including acceleration of amounts due under the Loan Agreement, which the Company may not have the available cash resources to repay at such time. For example, pursuant to covenants in the Loan Agreement, the Company's Annual Reports on Form 10-K must not be subject to any qualification as a going concern. If any of the Company's future Annual Reports on Form 10-K is subject to any qualification related to going concern, it will result in an event of default under the Loan Agreement. These conditions raise substantial doubt regarding the Company’s ability to continue as a going concern for a period of one year after the date the financial statements are issued. Management’s plans to alleviate the conditions that raise substantial doubt through cost avoidance measures, including amending certain contractual arrangements, and deprioritizing and cancelling certain infrastructure activities for the Company to continue as a going concern for a period of twelve months from the date the financial statements are issued. However, the Company has concluded that the likelihood that its plan to extend its cash runway from one or more of these approaches will be successful, while reasonably possible, is less than probable. Accordingly, the Company has concluded that substantial doubt exists about its ability to continue as a going concern for a period of at least twelve months from the date of issuance of these financial statements. The accompanying financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the ordinary course of business. The financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities, other than obligations under the Loan Agreement classified as current, that might result from the outcome of the uncertainties described above.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the U.S., or GAAP, for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the ASC and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB. 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 and six months ended June 30, 2022 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2022 or any other future period. The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation. Management has determined that the Company operates in one segment, which is the business of developing and commercializing novel therapeutics for people with kidney disease. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company’s consolidated financial statements and the accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2021 filed with the U.S. Securities and Exchange Commission on March 1, 2022, or the 2021 Annual Report on Form 10-K. The significant accounting policies used in preparation of these unaudited condensed consolidated financial statements for the three and six months ended June 30, 2022 are consistent with those discussed in Note 2 to the consolidated financial statements in the Company’s 2021 Annual Report on Form 10-K and are updated below as necessary. New Accounting Pronouncements – Not Yet Adopted In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting . The amendments provide optional guidance for a limited time to ease the potential burden in accounting for reference rate reform. The new guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments apply only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. These amendments are effective immediately and may be applied prospectively to contract modifications made and hedging relationships entered into or evaluated on or before December 31, 2022. The Company is currently evaluating its contracts and the optional expedients provided by the new standard. 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 and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Estimates are used in the following areas, among others: prepaid and accrued research and development expense, operating lease assets and liabilities, derivative liabilities, refund liabilities to customers, other non-current liabilities, including the excess purchase commitment liability, stock-based compensation expense, product and collaboration revenues including various rebates and reserves related to product sales, non-cash interest expense on the liability related to sale of future royalties, inventories, income taxes, intangible assets and goodwill. 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. The Company bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances.

Product Revenue and Reserves fo

Product Revenue and Reserves for Variable Consideration	6 Months Ended
	Jun. 30, 2022
Revenue from Contract with Customer [Abstract]
Product Revenue and Reserves for Variable Consideration	Product Revenue and Reserves for Variable Consideration To date, the Company’s only source of product revenue has been from the U.S. sales of Auryxia. Total net product revenue was $43.7 million and $33.0 million for the three months ended June 30, 2022 and 2021, respectively, and $85.2 million and $63.4 million for the six months ended June 30, 2022 and 2021, respectively. The following table summarizes activity in each of the product revenue allowance and reserve categories for the six months ended June 30, 2022 and 2021 (in thousands): Chargebacks Rebates, Fees Returns Total Balance at December 31, 2021 $ 1,278 $ 26,625 $ 475 $ 28,378 Current provisions related to sales in current year 4,928 42,566 2,871 50,365 Adjustments related to prior year sales 131 784 — 915 Credits/payments made (5,236) (43,803) (2,804) (51,843) Balance at June 30, 2022 $ 1,101 $ 26,172 $ 542 $ 27,815 Balance at December 31, 2020 $ 802 $ 39,912 $ 649 $ 41,363 Current provisions related to sales in current year 6,084 69,163 3,616 78,863 Adjustments related to prior year sales (6) 812 — 806 Credits/payments made (5,588) (63,795) (3,715) (73,098) Balance at June 30, 2021 $ 1,292 $ 46,092 $ 550 $ 47,934 Chargebacks, discounts and returns are recorded as a direct reduction of revenue on the unaudited condensed consolidated statement of operations with a corresponding reduction to accounts receivable on the unaudited condensed consolidated balance sheets. Rebates, distribution-related fees, and other sales-related deductions are recorded as a reduction in revenue on the unaudited condensed consolidated statement of operations with a corresponding increase to accrued liabilities or accounts payable on the unaudited condensed consolidated balance sheets. Accounts receivable, net related to product sales was approximately $24.8 million and $24.6 million as of June 30, 2022 and December 31, 2021, respectively.

License, Collaboration and Othe

License, Collaboration and Other Significant Agreements	6 Months Ended
	Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License, Collaboration and Other Significant Agreements	License, Collaboration and Other Significant Agreements During the three and six months ended June 30, 2022 and 2021, the Company recognized the following revenues from its license, collaboration and other significant agreements and had the following deferred revenue balances as of June 30, 2022: Three Months Ended June 30, Six Months Ended June 30, 2022 2021 2022 2021 License, Collaboration and Other Revenue: (in thousands) (in thousands) MTPC Agreement $ 434 $ 4,594 $ 8,398 $ 4,612 Otsuka U.S. Agreement 81,135 9,170 86,773 22,844 Otsuka International Agreement — 4,700 5,503 11,672 Total Proportional Performance Revenue $ 81,569 $ 18,464 $ 100,674 $ 39,128 JT and Torii 1,487 1,490 2,633 2,649 MTPC Other Revenue — — — 73 Total License, Collaboration and Other Revenue $ 83,056 $ 19,954 $ 103,307 $ 41,850 June 30, 2022 Short-Term Long-Term Total Deferred Revenue: (in thousands) MTPC Agreement $ 5,047 $ — $ 5,047 Vifor Pharma Agreement — 43,296 43,296 Total $ 5,047 $ 43,296 $ 48,343 The following table presents changes in the Company’s contract assets and liabilities during the six months ended June 30, 2022 and 2021 (in thousands): Six Months Ended June 30, 2022 Balance at Additions Deductions Balance at End Contract assets: Accounts receivable(1) $ 19,094 $ 92,146 $ (54,614) $ 56,626 Prepaid expenses and other current assets $ 4,309 $ 9,550 $ (4,309) $ 9,550 Contract liabilities: Deferred revenue $ 42,380 $ 65,042 $ (59,079) $ 48,343 Accounts payable $ 3,171 $ — $ (3,171) $ — Accrued expenses and other current liabilities $ — $ — $ — $ — Six Months Ended June 30, 2021 Contract assets: Accounts receivable(1) $ 3,045 $ 18,884 $ (19,112) $ 2,817 Prepaid expenses and other current assets $ 1,722 $ 211 $ (5) $ 1,928 Contract liabilities: Deferred revenue $ 40,559 $ 36,679 $ (48,770) $ 28,468 Accounts payable $ 7,227 $ — $ (7,227) $ — Accrued expenses and other current liabilities $ 10,000 $ — $ — $ 10,000 (1) Excludes accounts receivable from other services related to clinical and regulatory activities performed by the Company on behalf of MTPC that are not included in the performance obligations identified under the MTPC Agreement as of June 30, 2022 and 2021 and December 31, 2021 and 2020. Also excludes accounts receivable related to amounts due to the Company from product sales which are included in the accompanying unaudited condensed consolidated balance sheet as of June 30, 2022 and December 31, 2021. During the three and six months ended June 30, 2022 and 2021, 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 June 30, Six Months Ended June 30, Revenue Recognized in the Period: 2022 2021 2022 2021 Amounts included in deferred revenue at the beginning of the period $ 15,503 $ 5,822 $ 22,105 $ 10,895 Performance obligations satisfied in previous periods $ — $ — $ — $ — Mitsubishi Tanabe Pharma Corporation Collaboration Agreement Summary of Agreement On December 11, 2015, the Company and MTPC entered into the MTPC Agreement, providing MTPC with exclusive development and commercialization rights to vadadustat in Japan and certain other Asian countries, collectively, the MTPC Territory. In addition, the Company will supply vadadustat for both clinical and commercial use in the MTPC Territory, subject to MTPC’s option to manufacture commercial drug product in the MTPC 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 MTPC Agreement, subject to certain caps and other terms and conditions (see Note 6 for additional information). A more detailed description of the MTPC Agreement and the Company's evaluation of this agreement under ASC 606 can be found in Note 4 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. The Company identified two performance obligations in connection with its material promises under the MTPC Agreement as follows: (i) License, Research and Clinical Supply Performance Obligation and (ii) Rights to Future Know-How Performance Obligation . 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. The deliverables associated with the License, Research and Clinical Supply Performance Obligation were satisfied as of June 30, 2018. As of June 30, 2022, 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 MTPC for the Phase 3 studies, (iv) $10.0 million in development milestones received, (v) $25.0 million in regulatory milestones received, comprised of $10.0 million relating to the NDA filing in Japan and $15.0 million relating to regulatory approval of vadadustat in Japan, and (vi) $2.0 million in royalties from net sales of Vafseo. As of June 30, 2022, all development milestones and $25.0 million in regulatory milestones have been achieved. No other regulatory milestones have been assessed as probable of being achieved and as a result have been fully constrained. The Company re-evaluates the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. Revenue for the License, Research and Clinical Supply Performance Obligation for the MTPC Agreement is being recognized using a proportional performance method, for which all deliverables have been completed. During the three and six months ended June 30, 2022, the Company recognized revenue from MTPC royalties totaling approximately $0.4 million and $0.7 million, respectively, and approximately $0.1 million during each of the three and six months ended June 30, 2021. 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 MTPC Agreement, subject to certain caps and other terms and conditions (see Note 6 for additional information). The revenue is classified as license, collaboration and other revenue in the accompanying unaudited condensed consolidated statements of operations and comprehensive loss. As of June 30, 2022, the Company recorded $0.2 million in accounts receivable, no deferred revenue, and no contract assets. There were no asset or liability balances classified as long-term in the unaudited condensed consolidated balance sheet as of June 30, 2022. Supply of Drug Product to MTPC On July 15, 2020, the Company and its collaboration partner MTPC entered into a supply agreement, or the MTPC Supply Agreement. The MTPC Supply Agreement includes the terms and conditions under which the Company will supply vadadustat drug product to MTPC for commercial use in Japan and certain other Asian countries, as contemplated by the MTPC Agreement. A more detailed description of this supply agreement can be found in Note 4 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. The Company recognized no revenue and $7.6 million in revenue under the MTPC Supply Agreement during the three and six months ended June 30, 2022, respectively, and $4.5 million during each of the three and six months ended June 30, 2021. As of June 30, 2022, the Company recorded $0.4 million in accounts receivable, $5.0 million in deferred revenue, $19.5 million in other current liabilities and no other non-current liabilities. U.S. Collaboration and License Agreement with Otsuka Pharmaceutical Co. Ltd. On December 18, 2016, the Company entered into the Otsuka U.S. Agreement. The collaboration was focused on the development and commercialization of vadadustat in the United States. The Company was responsible for leading the development of vadadustat, for which it submitted an NDA to the FDA in March 2021, and for which it received a CRL in March 2022. Under the terms of the Otsuka U.S. Agreement, the Company granted to Otsuka a co-exclusive, non-sublicensable license under certain intellectual property controlled by the Company solely to perform medical affairs activities and to conduct non-promotional and commercialization activities related to vadadustat in the United States in accordance with the associated plans. The co-exclusive license related to activities that will be jointly conducted by the Company and Otsuka pursuant to the terms of the Otsuka U.S. Agreement. A more detailed description of this collaboration agreement and the Company's evaluation of this agreement under ASC 606 can be found in Note 4 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. The Company identified three performance obligations in connection with its obligations under the Otsuka U.S. Agreement as follows: (i) License and Development Services Combined (License Performance Obligation); (ii) Rights to Future Intellectual Property (Future IP Performance Obligation) and (iii) Joint Committee Services (Committee Performance Obligation). The Company allocated 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 standalone selling price for the Committee Performance Obligation after considering the nature of the services to be performed and estimates of the associated effort and rates applicable to such services that would be expected to be realized under similar contracts. The Company developed a best estimate of standalone selling price for the Future IP Performance Obligation primarily based on the likelihood that additional intellectual property covered by the license conveyed would be developed during the term of the arrangement. The Company did not develop a best estimate of standalone selling price for the License Performance Obligation due to the following: (i) the best estimates of standalone selling price associated with the Future IP Performance Obligation was determined to be immaterial and (ii) the period of performance and pattern of recognition for the License Performance Obligation and the Committee Performance Obligation was determined to be similar. The Company re-evaluated the transaction price in each reporting period and as uncertain events were resolved or other changes in circumstances occurred. The Company determined that under ASC 606, the contract was modified in the second quarter of 2019, when the Company elected to require Otsuka to increase the aggregate percentage of current global development costs it funds under the Otsuka U.S. Agreement and the Otsuka International Agreement, as defined below, from 52.5% to 80%, or the Otsuka Funding Option, and the Company became eligible to receive the amount from the Otsuka Funding Option. In connection with the modification, the Company adjusted the transaction price to include the amount from the Otsuka Funding Option as additional variable consideration. The Company constrained the variable consideration to an amount for which a significant revenue reversal is not probable. Pursuant to the Otsuka U.S. Agreement, the Company received: (i) an up-front payment of $125.0 million, (ii) a cost share payment with respect to amounts incurred by the Company through December 31, 2016 of $33.8 million, and (iii) net cost share consideration with respect to amounts incurred by the Company under the global development plan of approximately $319.2 million with respect to amounts incurred by the Company subsequent to December 31, 2016. On May 12, 2022, the Company received notice from Otsuka that it had elected to terminate the Otsuka U.S. Agreement and the Otsuka International Agreement. On June 30, 2022, the Company and Otsuka entered into the Termination Agreement, pursuant to which, among other things, the Company and Otsuka agreed to terminate, as of June 30, 2022, the Otsuka U.S. Agreement and the Otsuka International Agreement. In July 2022, the Company received a nonrefundable and non-creditable payment of $55.0 million in consideration for the covenants and agreements set forth in the Termination Agreement, including the settlement and release of all disputes and claims as provided therein. The Company determined that the Termination Agreement met the definition of a contract modification and was accounted for as a cumulative catch-up adjustment at the time of modification under ASC 606. During the three months ended June 30, 2022, the Company recognized $81.1 million of collaboration revenue from Otsuka in its condensed consolidated statement of operations and comprehensive income (loss). This is primarily comprised of the $55.0 million payment to be received pursuant to the Termination Agreement, $15.5 million related to previously deferred revenue as of the date of termination and $9.6 million of non-cash consideration related to Otsuka's obligations to complete certain agreed upon clinical activities related to the Phase 3b clinical trial of vadadustat Otsuka is conducting. During the six months ended June 30, 2022, the Company recognized $92.3 million of collaboration revenue from the Otsuka U.S. Agreement and the Otsuka International Agreement in its condensed consolidated statement of operations and comprehensive income (loss). During the three and six months ended June 30, 2021, the Company recognized revenue totaling $9.2 million and $22.8 million, respectively, with respect to the Otsuka U.S. Agreement. The revenue is classified as collaboration revenue in the accompanying unaudited condensed consolidated statements of operations. As of June 30, 2022, there was no deferred revenue related to the Otsuka U.S. Agreement. Additionally, as of June 30, 2022, there was $55.0 million in accounts receivable and $9.6 million in prepaid expenses and other current assets in the accompanying unaudited condensed consolidated balance sheet. As of December 31, 2021, there was approximately $2.0 million in contract liabilities (included in accounts payable) and $3.0 million in prepaid expenses and other current assets in the consolidated balance sheet. International Collaboration and License Agreement with Otsuka Pharmaceutical Co. Ltd. On April 25, 2017, the Company entered into the Otsuka International Agreement. The collaboration was focused on the development and commercialization of vadadustat in Europe, Russia, China, Canada, Australia, the Middle East and certain other territories, collectively, the Otsuka International Territory. Under the terms of the Otsuka International Agreement, the Company granted to Otsuka an exclusive, sublicensable license under certain intellectual property controlled by the Company to develop and commercialize vadadustat and products containing or comprising vadadustat in the Otsuka International Territory. Additionally, under the terms of this agreement, the Company was responsible for leading the development of vadadustat. Otsuka had the sole responsibility, at its own cost, for the commercialization of vadadustat in the Otsuka International Territory, subject to the approval by the relevant regulatory authorities. A more detailed description of this collaboration agreement and the Company's evaluation of this agreement under ASC 606 can be found in Note 4 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. The Company identified three performance obligations in connection with its obligations under the Otsuka International Agreement as follows: (i) License and Development Services Combined (License Performance Obligation); (ii) Rights to Future Intellectual Property (Future IP Performance Obligation) and (iii) Joint Committee Services (Committee Performance Obligation). The Company allocated 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 standalone selling price for the Committee Performance Obligation after considering the nature of the services to be performed and estimates of the associated effort and rates applicable to such services that would be expected to be realized under similar contracts. The Company developed a best estimate of standalone selling price for the Future IP 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. The Company did not develop a best estimate of standalone selling price for the License Performance Obligation due to the following: (i) the best estimates of standalone selling price associated with the Future IP Performance Obligation was determined to be immaterial and (ii) the period of performance and pattern of recognition for the License Performance Obligation and the Committee Performance Obligation was determined to be similar. The Company re-evaluated the transaction price in each reporting period and as uncertain events were resolved or other changes in circumstances occurred. Pursuant to the Otsuka International Agreement, the Company received: (i) an up-front payment of $73.0 million, (ii) the cost share payment with respect to amounts incurred by the Company during the quarter ended March 31, 2017 of $0.2 million, and (iii) the net cost share consideration with respect to amounts incurred by the Company under the global development plan subsequent to March 31, 2017 of $216.7 million. As discussed above, the Otsuka International Agreement was terminated on June 30, 2022 pursuant to the Termination Agreement. Refer to earlier in this Note 4 for further details of the recognition of this Termination Agreement in the Company's condensed consolidated statement of operations and comprehensive income (loss). During the three and six months ended June 30, 2021, the Company recognized revenue totaling approximately $4.7 million and $11.7 million, respectively, with respect to the Otsuka International Agreement. The revenue is classified as collaboration revenue in the accompanying unaudited condensed consolidated statements of operations. As of June 30, 2022, there was no deferred revenue related to the Otsuka International Agreement. As of June 30, 2022, there were no accounts receivable and no prepaid expenses and other current assets in the accompanying unaudited condensed consolidated balance sheet specific to the Otsuka International Agreement. As of December 31, 2021, there was approximately $0.9 million in contract liabilities (included in accounts payable) and $1.3 million in prepaid expenses and other current assets in the consolidated balance sheet. Janssen Pharmaceutica NV Research and License Agreement On February 9, 2017, the Company entered into a Research and License Agreement, or the Janssen Agreement, with Janssen Pharmaceutica NV, or Janssen, a subsidiary of Johnson & Johnson, pursuant to which Janssen granted the Company an exclusive license under certain intellectual property rights to develop and commercialize worldwide certain HIF prolyl hydroxylase targeted compounds. Under the terms of the Janssen Agreement, Janssen granted to the Company a license for a three-year research term to conduct research on the HIF compound portfolio, which research term is now expired. A more detailed description of this collaboration agreement can be found in Note 4 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. Under the terms of the Janssen Agreement, the Company made an upfront payment of $1.0 million in cash to Janssen and issued a warrant, or the Warrant, to purchase 509,611 shares of the Company’s common stock, which expired on February 9, 2022. In addition, Janssen could be eligible to receive up to an aggregate of $16.5 million from the Company in specified development milestone payments on a product-by-product basis. Janssen could also be eligible to receive up to $215.0 million from the Company in specified commercial milestones as well as tiered, escalating royalties ranging from a low- to mid-single digit percentage 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. A more detailed description of this collaboration agreement can be found in Note 4 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. On August 1, 2022, the Company notified Janssen that it was exercising its right to terminate the Janssen Agreement, and Janssen agreed to the termination which became effective on August 2, 2022. Cyclerion Therapeutics License Agreement On June 4, 2021, the Company entered into a License Agreement, the Cyclerion Agreement, with Cyclerion Therapeutics Inc., or Cyclerion, pursuant to which Cyclerion granted the Company an exclusive global license under certain intellectual property rights to research, develop and commercialize praliciguat, an investigational oral soluble guanylate stimulator. Under the terms of the Cyclerion Agreement, the Company made an upfront payment of $3.0 million in cash to Cyclerion, which was paid during the second quarter of 2021 and recorded to research and development expense in June 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 upfront payment was charged to expense at acquisition, as it relates to a development stage compound with no alternative future use. In addition, Cyclerion is eligible to receive up to an aggregate of $222.0 million from the Company in specified development and regulatory milestone payments on a product-by-product basis. Cyclerion will also be eligible to receive specified commercial milestones as well as tiered royalties ranging from a low-single-digit- to mid-double-digit percentage 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. A more detailed description of this agreement can be found in Note 4 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. Vifor Pharma License Agreement Summary of License Agreement On May 12, 2017, the Company entered into a License Agreement, or the Vifor Agreement, with Vifor (International) Ltd., or Vifor Pharma, pursuant to which the Company granted Vifor Pharma an exclusive license to sell vadadustat solely to Fresenius Kidney Care Group LLC, or FKC, an affiliate of Fresenius Medical Care North America, or FMCNA, in the United States. On April 8, 2019, the Company and Vifor Pharma entered into an Amended and Restated License Agreement, or the Vifor First Amended Agreement, which amended and restated in full the Vifor Agreement. On February 18, 2022, the Company and Vifor Pharma entered into a Second Amended and Restated License Agreement, or the Vifor Second Amended Agreement, which amends and restates the Vifor First Amended Agreement. Pursuant to the Vifor Second Amended Agreement, the Company granted Vifor Pharma an exclusive license to sell vadadustat 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 to certain non-retail specialty pharmacies, or collectively, the Supply Group, in the United States, or the Territory. Pursuant to the Vifor Second Amended Agreement, Vifor Pharma agreed that it would not sell or otherwise supply vadadustat until the FDA has granted regulatory approval for vadadustat in the DD-CKD Indication in the Territory and until Vifor Pharma has entered a supply agreement with the applicable member of the Supply Group. Similar to the Vifor First Amended Agreement, the Vifor Second Amended Agreement is structured as a profit share arrangement between the Company and Vifor Pharma in which the Company will receive approximately 66% of the profit, net of certain pre-specified costs. Under the Vifor Second Amended Agreement, Vifor Pharma made an upfront payment to the Company of $25.0 million in lieu of the previously disclosed milestone payment of $25.0 million that Vifor Pharma was to pay the Company following approval of vadadustat by the FDA, as established under the Vifor First Amended Agreement. Unless earlier terminated, the Vifor Second Amended Agreement will expire upon the later of the expiration of all patents that claim or cover vadadustat or expiration of marketing or regulatory exclusivity for vadadustat in the Territory. Vifor Pharma may terminate the Vifor Second Amended Agreement in its entirety upon 30 months' prior written notice after the first anniversary of the receipt of regulatory approval, if approved from the FDA for vadadustat for dialysis-dependent CKD patients. The Company may terminate the Vifor Second Amended Agreement in its entirety for convenience, following the earlier of a certain period of time elapsing or following certain specified regulatory events, and upon six months’ prior written notice. If the Company so terminates for convenience, subject to specified exceptions, the Company will pay a termination fee to Vifor Pharma. In addition, either party may, subject to a cure period, terminate the Vifor Second Amended Agreement in the event of the other party’s uncured material breach or bankruptcy. Investment Agreement In connection with the Vifor Agreement, in May 2017, the Company and Vifor Pharma entered into an investment agreement, or the First Investment Agreement, pursuant to which the Company sold an aggregate of 3,571,429 shares of the Company’s common stock, or the 2017 Shares, to Vifor Pharma at a price per share of $14.00 for a total of $50.0 million. The amount representing the premium over the closing stock price of $12.69 on the date of the transaction, totaling $4.7 million, was determined by the Company to represent consideration related to the Vifor Agreement. Vifor Pharma agreed to a lock-up restriction such that it agreed not to sell the 2017 Shares for a period of time following the effective date of the First Investment Agreement as well as a customary standstill agreement. In addition, the First Investment Agreement contains voting agreements made by Vifor Pharma with respect to the 2017 Shares. The 2017 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. In connection with entering into the Vifor Second Amended Agreement, on February 18, 2022, the Company and Vifor Pharma entered into an investment agreement, or the Second Investment Agreement, pursuant to which the Company sold an aggregate of 4,000,000 shares of its common stock, or the 2022 Shares, to Vifor Pharma for a total of $20 million on February 22, 2022. The amount representing the premium over the grant date fair value on the date of the transaction, $13.6 million, was determined by the Company to represent the consideration related to the Vifor Second Amended Agreement. Vifor Pharma has agreed to a lock-up restriction to not sell or otherwise dispose of the 2022 Shares for a period of time following the effective date of the Second Investment Agreement as well as a customary standstill agreement. In addition, the Second Investment Agreement contains voting agreements made by Vifor Pharma with respect to the 2022 Shares. The 2022 Shares have not been registered pursuant to 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/or Rule 506 promulgated thereunder, as the transaction does not involve any public offering within the meaning of Section 4(a)(2) of the Securities Act. Revenue Recognition The Company evaluated the elements of the Vifor Second Amended Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, Vifor Pharma, is a customer. The Company’s arrangement with Vifor Pharma contains one material promise under the contract at inception, which is the non-sublicensable, non-transferrable license under certain of the Company’s intellectual property to (i) sell vadadustat solely to the Supply Group, (ii) sell vadadustat to Designated Wholesalers solely for resale to members of the Supply Group, (iii) conduct medical affairs with respect to vadadustat in the Territory in the field during the term of the Vifor Second Amended Agreement and (iv) use the Akebia Trademark solely in connection with the sale of vadadustat (the License Deliverable). The Company has identified one performance obligation in connection with its obligations under the Vifor Second Amended Agreement, which is the License Deliverable, or License Performance Obligation. The transaction price at inception was comprised of: (i) the up-front payment of $25.0 million, (ii) the premium paid by Vifor Pharma on the First Investment Agreement of $4.7 million, and (iii) the premium paid by Vifor Pharma on the Second Investment Agreement of $13.6 million. Pursuant to the terms of the Vifor Second Amended Agreement, these payments from Vifor Pharma are non-refundable and non-creditable against any other amount due to the Company. Also pursuant to the Vifor Second Amended Agreement, if the Centers for Medicare & Medicaid Services, or CMS, determines that vadadustat is excluded from the Transitional Drug Add-on Payment Adjustment, or TDAPA, the Company can terminate the Vifor Second Amended Agreement and will be required to repay the up-front payment and the premiums paid by Vifor Pharma in the First Investment Agreement and Second Investment Agreement, respectively. The Company considered whether the transaction price was constrained as required per the guidance in ASC 606-10-32-11. As part of its evaluation of the constraint, the Company considered numerous factors, including the CRL received from the FDA for vadadustat, the uncertainty associated with a potential future approval of vadadustat by the FDA, and if approval of vadadustat is received in the future, whether vadadustat would be included in certain reimbursement bundles by CMS, which are all outside of the Company’s control. Vifor Pharma also agreed that it will not sell or otherwise supply vadadustat until the FDA has granted regulatory approval for vadadustat in the DD-CKD Indication. The Company constrains the variable consideration to an amount for which a significant revenue reversal is not probable. Therefore, the Company determined that the entire transaction price at inception was constrained under ASC 606, and the Company has recorded the transaction price to deferred revenue as of June 30, 2022. Refund Liability to Customer Pursuant to the Vifor Second Amended Agreement, Vifor Pharma contributed $40.0 million to a working capital fund established to partially fund the Company’s costs of purchasing vadadustat from its contract manufacturers, or the Working Capital Fund, which amount of funding will fluctuate, and which funding the Company will repay to Vifor over time. The $40 million initial contribution to the Working Capital Fund represents 50% of the amount of purchase orders that the Company has placed with its contract manufacturers for the supply of vadadustat for the Territory already delivered as of the effective date of the Vifor Second Amended Agreement, and to be delivered through the end of 2022. The amount of the Working Capital Fund will be reviewed at specified intervals and is adjusted based on a number of f

Restructuring

Restructuring	6 Months Ended
	Jun. 30, 2022
Restructuring and Related Activities [Abstract]
Restructuring	Restructuring On April 4, 2022, the Board of Directors of the Company approved a reduction of the Company’s workforce by approximately 42% across all areas of the Company (47% inclusive of the closing of the majority of open positions) following the receipt of a CRL from the FDA to the Company’s NDA for vadadustat for the treatment of anemia due to CKD in adult patients. This workforce reduction was substantially completed as of June 30, 2022. On May 5, 2022, the Company implemented a further reduction in workforce consisting of several members of management. This workforce reduction is expected to be substantially complete by the end of January 2023. These actions reflect the Company’s determination to refocus its strategic priorities around its commercial product, Auryxia ® , and its development portfolio, and are steps in a cost savings plan to significantly reduce the Company’s expense profile in line with being a single commercial product company. The workforce reduction is expected to include total restructuring charges of approximately $14.8 million. During each of the three and six months ended June 30, 2022, the Company recognized $14.5 million of restructuring charges in the condensed consolidated statement of operations. These charges included $11.2 million of one-time termination benefits and contractual termination benefits for severance, healthcare, and related benefits and $3.3 million of non-cash share-based compensation expense. The charges were recorded pursuant to ASC 712, Compensation-Nonretirement Postemployment Benefits or ASC 420, Exit or Disposal Cost Obligations, depending on the employee . The Company will fully recognize the remaining $0.3 million in the third quarter of 2022. Details of the restructuring liability activity for the Company's workforce reduction for the period ended June 30, 2022 are as follows: June 30, 2022 (in thousands) Balance at December 31, 2021 $ — Restructuring charges 14,531 Stock-based compensation expense (3,303) Severance payments and adjustments (4,313) Balance at June 30, 2022 $ 6,915

Liability Related to Sale of Fu

Liability Related to Sale of Future Royalties	6 Months Ended
	Jun. 30, 2022
Other Liabilities Disclosure [Abstract]
Liability Related to Sale of Future Royalties	Liability Related to Sale of Future Royalties On February 25, 2021, the Company entered into the Royalty Agreement with HCR, pursuant to which the Company sold to HCR its right to receive royalties and sales milestones for vadadustat in Japan and certain other Asian countries, such countries, collectively, the MTPC Territory, and such payments collectively the Royalty Interest Payments, in each case, payable to the Company under the MTPC Agreement, subject to an annual maximum “cap” of $13.0 million, or the Annual Cap, and an aggregate maximum “cap” of $150.0 million, or the Aggregate Cap. The Company received $44.8 million from HCR (net of certain transaction expenses) under the Royalty Agreement. The Company retains the right to receive all potential future regulatory milestones for vadadustat under the MTPC Agreement. Although the Company sold its right to receive royalties and sales milestones for vadadustat in the MTPC Territory as described above, as a result of its ongoing involvement in the cash flows related to these royalties, the Company will continue to account for these royalties as revenue. The Company recognized the proceeds received from HCR as a liability that is being amortized using the effective interest method over the life of the arrangement. At the transaction date, the Company recorded the net proceeds of $44.8 million as a liability. In order to determine the amortization of the liability, the Company is required to estimate the total amount of future net royalty payments to be made to HCR over the term of the Royalty Agreement. The total threshold of net royalties to be paid, less the net proceeds received, will be recorded as interest expense over the life of the liability. The Company imputes interest on the unamortized portion of the liability using the effective interest method. The annual effective interest rate as of June 30, 2022 was 15.1% which is reflected as interest expense in the unaudited condensed consolidated statements of operations and comprehensive loss. On a quarterly basis, the Company reassesses the effective interest rate and adjusts the rate prospectively as needed. A more detailed description of Royalty Agreement can be found in Note 5 of the Notes to the Consolidated Financial Statements in the 2021 Annual Report on Form 10-K. The following table shows the activity within the liability account for the six months ended June 30, 2022: June 30, 2022 (in thousands) Liability related to sale of future royalties, net beginning balance at December 31, 2021 $ 53,079 MTPC royalties payable (764) Non-cash interest expense recognized 4,428 Liability related to sale of future royalties, net — ending balance $ 56,743

Fair Value of Financial Instrum

Fair Value of Financial Instruments	6 Months Ended
	Jun. 30, 2022
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company utilizes a portfolio management company for the valuation of the majority of its investments. This portfolio management company is an independent, third-party vendor recognized to be an industry leader with access to market information that obtains or computes fair market values from quoted market prices, pricing for similar securities, recently executed transactions, cash flow models with yield curves and other pricing models. For valuations obtained from the pricing service, the Company performs due diligence to understand how the valuation was calculated or derived, focusing on the valuation technique used and the nature of the inputs. Based on the fair value hierarchy, the Company classifies its cash equivalents within Level 1 or Level 2. This is because the Company values its cash equivalents using quoted market prices or alternative pricing sources and models utilizing market observable inputs. Assets measured or disclosed at fair value on a recurring basis as of June 30, 2022 and December 31, 2021 are summarized below: Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) June 30, 2022 Assets: Cash and cash equivalents $ 143,893 $ — $ — $ 143,893 $ 143,893 $ — $ — $ 143,893 Liabilities: Derivative liability $ — $ — $ 1,110 $ 1,110 $ — $ — $ 1,110 $ 1,110 Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) December 31, 2021 Assets: Cash and cash equivalents $ 149,800 $ — $ — $ 149,800 $ 149,800 $ — $ — $ 149,800 Liabilities: Derivative liability $ — $ — $ 1,820 $ 1,820 $ — $ — $ 1,820 $ 1,820 The Company’s Loan Agreement with Pharmakon (see Note 11) contains certain provisions that change the underlying cash flows of the debt instrument, including a potential extension to the interest-only period dependent on both (i) no event of default having occurred and continuing and (ii) the Company achieving certain regulatory and revenue conditions. One of the regulatory conditions was approval of vadadustat by August 2022, however, in March 2022, the Company received a CRL from the FDA stating that the FDA had determined that it could not approve the NDA for vadadustat in its present form. Therefore, the Company is no longer eligible for the interest-only extension period and this no longer changes the underlying cash flows of the debt instrument. The Company also assessed the acceleration of the obligations under the Loan Agreement under certain events of default. In addition, under certain circumstances, a default interest rate will apply on all outstanding obligations during the occurrence and continuance of an event of default. In accordance with ASC 815, the Company concluded that these features are not clearly and closely related to the host instrument, and represent a single compound derivative that is required to be re-measured at fair value on a quarterly basis. The potential events of default assessed include failure to maintain, on an annual basis, a minimum liquidity threshold which started in 2021, and on a quarterly basis, a minimum net sales threshold for Auryxia which started in the fourth quarter of 2020. The Company recorded a derivative liability related to the Company’s Loan Agreement with Pharmakon of $1.1 million and $1.8 million as of June 30, 2022 and December 31, 2021, respectively. The Company classified the derivative liability as a non-current liability on the unaudited condensed consolidated balance sheet as of June 30, 2022 and December 31, 2021. The estimated fair value of the derivative liability on both June 30, 2022 and December 31, 2021 was determined using a scenario-based approach and discounted cash flow model that includes principal and interest payments under various scenarios involving clinical development success for vadadustat and various cash flow assumptions. The Company used a 0% probability of clinical development success due to receipt of a CRL from the FDA for vadadustat. Should the Company’s assessment of the probabilities around these scenarios change, including for changes in market conditions, there could be a change to the fair value of the derivative liability. The following table provides a roll-forward of the fair value of the derivative liability (in thousands): Balance at December 31, 2021 $ 1,820 Change in fair value of derivative liability, recorded as other income (710) Balance at March 31, 2022 $ 1,110 Change in fair value of derivative liability, recorded as other income — Balance at June 30, 2022 $ 1,110 The Company had no other assets or liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) at June 30, 2022 and December 31, 2021.

Inventory

Inventory	6 Months Ended
	Jun. 30, 2022
Inventory Disclosure [Abstract]
Inventory	Inventory The components of inventory are summarized as follows: June 30, 2022 December 31, 2021 (in thousands) Raw materials $ 757 $ 1,763 Work in process 38,466 62,635 Finished goods 18,843 14,661 Total inventory $ 58,066 $ 79,059 Long-term inventory, which primarily consists of raw materials and work in process, is included in other assets in the Company’s unaudited condensed consolidated balance sheets. June 30, 2022 December 31, 2021 (in thousands) Balance Sheet Classification: Inventory $ 36,272 $ 38,195 Other assets 21,794 40,864 Total inventory $ 58,066 $ 79,059 Inventory amounts written down as a result of excess, obsolescence, scrap or other reasons and charged to cost of goods sold totaled $2.1 million and $0.4 million during the three months ended June 30, 2022 and 2021, respectively, and $7.4 million and $5.4 million during the six months ended June 30, 2022 and 2021, respectively. The increase in inventory amounts written down for the three and six months ended June 30, 2022 as compared to the three and six months ended June 30, 2021 was primarily due to higher write-downs to inventory reserves related to expired inventory. In addition, there were no related step-up charges during the six months ended June 30, 2022 and $8.7 million related step-up charges during the six months ended June 30, 2021. During the six months ended June 30, 2022, the Company recorded a $9.8 million reduction to the excess purchase commitment liability related to Auryxia inventory previously identified as excess, reflecting Auryxia inventory that was received during the period. If future sales of Auryxia are lower than expected, the Company may be required to write-down the value of such inventories. Inventory write-downs and losses on purchase commitments are recorded as a component of cost of goods sold in the unaudited condensed consolidated statement of operations.

Intangible Assets and Goodwill

Intangible Assets and Goodwill	6 Months Ended
	Jun. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	Intangible Assets and Goodwill Intangible Assets The following table presents the Company’s intangible assets at June 30, 2022 and December 31, 2021 (in thousands): June 30, 2022 Gross Carrying Accumulated Amortization Total Intangible assets: Developed product rights for Auryxia $ 213,603 $ (123,497) $ 90,106 Total $ 213,603 $ (123,497) $ 90,106 December 31, 2021 Gross Carrying Accumulated Total Intangible assets: Developed product rights for Auryxia $ 213,603 $ (105,476) $ 108,127 Total $ 213,603 $ (105,476) $ 108,127 The Company amortizes its definite-lived intangible assets using the straight-line method, which is considered the best estimate of economic benefit, over its estimated useful life of six years. The Company recorded $9.0 million in amortization expense related to the developed product rights for Auryxia during each of the three months ended June 30, 2022 and 2021, and $18.0 million during each of the six months ended June 30, 2022 and 2021. Goodwill The Company's goodwill results from the acquisition of Keryx in December 2018. Goodwill was $55.1 million as of June 30, 2022 and December 31, 2021. The Company operates in one operating segment which the Company considers to be the only reporting unit. Goodwill is evaluated for impairment at the reporting unit level on an annual basis as of October 1, and more frequently if indicators are present or changes in circumstances suggest that it is more likely than not that the fair value of the reporting unit is less than its carrying amount. Events that could indicate impairment and trigger an interim impairment assessment include, but are not limited to, an adverse change in current economic or market conditions, including a significant prolonged decline in market capitalization, a significant adverse change in legal factors, unexpected adverse business conditions, and an adverse action by a regulator. During the six months ended June 30, 2022, the Company evaluated business factors, including the receipt of a CRL from the FDA for vadadustat, the Company's market capitalization as impacted by a recent decline in the Company's stock price, and the impact of the Otsuka Termination Agreement on the Company's future cash flows to determine if there were events or changes in circumstance to indicate that the fair value of the reporting unit was less than its carrying value. The Company performed qualitative interim impairment assessments of the Company's goodwill balance as of each of the three months ended March 31, 2022 and June 30, 2022. The Company determined that it was not more likely than not that the fair value of the reporting unit was less than its carrying value and, therefore, did not perform a further quantitative interim impairment test for any period.

Accrued Expenses

Accrued Expenses	6 Months Ended
	Jun. 30, 2022
Payables and Accruals [Abstract]
Accrued Expenses	Accrued Expenses Accrued expenses as of June 30, 2022 and December 31, 2021 are as follows: June 30, 2022 December 31, 2021 (in thousands) Product revenue allowances $ 26,171 $ 26,624 Accrued clinical 7,622 14,036 Amounts due to collaboration partners 20,797 22,654 Accrued payroll and related 6,883 15,863 Lease liability 4,422 4,802 Royalties 3,457 3,472 Professional fees 1,815 1,899 Accrued commercial manufacturing 3,420 3,843 Accrued restructuring 6,915 — Accrued other 9,782 11,263 Total accrued expenses $ 91,284 $ 104,456

Debt

Debt	6 Months Ended
	Jun. 30, 2022
Debt Disclosure [Abstract]
Debt	Debt Term Loans On November 11, 2019, the Company, with Keryx as guarantor, entered into a loan agreement, or the Loan Agreement, with BioPharma Credit PLC as collateral agent and a lender, or the Collateral Agent, and BioPharma Credit Investments V (Master) LP as a lender, pursuant to which term loans in an aggregate principal amount of $100.0 million were made available to the Company in two tranches, subject to certain terms and conditions, or the Term Loans. BioPharma Credit PLC subsequently transferred its interest in the Term Loans, solely in its capacity as a lender, to its affiliate, BPCR Limited Partnership. The Collateral Agent and the lenders are collectively referred to as Pharmakon (see Note 1 to our condensed consolidated financial statements). The first tranche of $80.0 million, or Tranche A, was drawn on November 25, 2019, or the Tranche A Funding Date, and the second tranche of $20.0 million, or Tranche B, was drawn on December 10, 2020, or the Tranche B Funding Date. Each of the Tranche A Funding Date and the Tranche B Funding Date, a Funding Date. Proceeds from the Term Loans may be used for general corporate purposes. The Company and Keryx entered into a Guaranty and Security Agreement with the Collateral Agent, or the Guaranty and Security Agreement, on the Tranche A Funding Date. Pursuant to the Guaranty and Security Agreement, the Company’s obligations under the Term Loans are unconditionally guaranteed by Keryx, or the Guarantee. Additionally, the obligations of the Company and Keryx under the Term Loans and the Guarantee are secured by a first priority lien on certain assets of the Company and Keryx, including Auryxia and certain related assets, cash, and certain equity interests held by the Company and Keryx, collectively the Collateral. The Term Loans bear interest at a floating rate per annum equal to the three-month LIBOR rate plus 7.50%, subject to a 2.00% LIBOR floor and a 3.35% LIBOR cap, payable quarterly in arrears. The Term Loans will mature on the fifth anniversary of the Tranche A Funding Date, or the Maturity Date. The Company will repay the principal under the Term Loans in equal quarterly payments starting on the 33rd-month anniversary of the applicable Funding Date, or the Amortization Schedule. If certain conditions are met, it would have the option to repay the principal in equal quarterly payments starting on the 48th-month anniversary of the applicable Funding Date. One of these conditions was approval of vadadustat; however, the Company received a CRL from the FDA in March 2022 stating that the FDA had determined that it could not approve the NDA in its present form. Therefore, the Company is no longer eligible for this option to delay repayment of the principal under the Loan Agreement. Under certain circumstances, unless certain liquidity conditions are met, the Maturity Date may decrease by up to one year, and the Amortization Schedule may correspondingly commence up to one year earlier. On the Tranche A Funding Date, the Company paid to Pharmakon a facility fee equal to 2.00% of the aggregate principal amount of the Term Loans, or $2.0 million, in addition to other expenses incurred by Pharmakon and reimbursed by the Company, or Lender Expenses. The Tranche A draw was $77.3 million, net of facility fee, Lender Expenses and issuance costs. The Tranche B draw was $20.0 million, net of immaterial Lender Expenses and issuance costs. The Loan Agreement permits voluntary prepayment at any time in whole or in part, subject to a prepayment premium. The prepayment premium would be 2.00% of the principal amount being prepaid prior to the third anniversary of the applicable Funding Date, 1.00% on or after the third anniversary, but prior to the fourth anniversary, of the applicable Funding Date, and 0.50% on or after the fourth anniversary of the applicable Funding Date but prior to the Maturity Date, and a make-whole premium on or prior to the second anniversary of the applicable Funding Date in an amount equal to foregone interest through the second anniversary of the applicable Funding Date. A change of control triggers a mandatory prepayment of the Term Loans. The Loan Agreement contains customary representations, warranties, events of default and covenants of the Company and its subsidiaries, including maintaining, on an annual basis, a minimum liquidity threshold which started in 2021, and on a quarterly basis, a minimum net sales threshold for Auryxia which started in the fourth quarter of 2020. On February 18, 2022, the Loan Agreement was amended by the First Amendment and Waiver, which waived the provision under the Loan Agreement that required the Company to not be subject to any qualification as a going concern within the Company's 2021 Annual Report on Form 10-K. Pursuant to the First Amendment and Waiver, the Company's filings of Form 10-Q for fiscal quarters ending June 30, 2022 and September 30, 2022, and its future Annual Reports on Form 10-K, must not be subject to any qualification as to going concern, which requirement as to the Company's filings on Form 10-Q was waived in the Second Amendment and Waiver. If the Company does not satisfy the covenant as to going concern in any of these filings, the Company will be in default under the Loan Agreement. There is uncertainty as to whether or not the Company will meet its future annual debt covenants related to qualification as to going concern. If an event of default occurs and is continuing under the Loan Agreement, the Collateral Agent is entitled to take enforcement action, including acceleration of amounts due under the Loan Agreement. Therefore, as of June 30, 2022, the Company continued to classify the borrowings under the Loan Agreement as current. Under certain circumstances, a default interest rate will apply on all outstanding obligations during the occurrence and continuance of an event of default. As of June 30, 2022 and December 31, 2021, the Company determined that no events of default had occurred. The Company assessed the terms and features of the Loan Agreement in order to identify any potential embedded features that would require bifurcation or any beneficial conversion feature. As part of this analysis, the Company assessed the economic characteristics and risks of the Loan Agreement, including put and call features. The terms and features assessed include a potential extension to the interest-only period dependent on both no event of default having occurred and continuing and the Company achieving certain regulatory and revenue conditions. The Company also assessed the acceleration of the obligations under the Loan Agreement under an event of default. In addition, under certain circumstances, a default interest rate will apply on all outstanding obligations during the occurrence and continuance of an event of default. In accordance with ASC 815, the Company concluded that these features are not clearly and closely related to the host instrument, and represent a single compound derivative that is required to be re-measured at fair value on a quarterly basis. The fair value of the derivative liability related to the Company’s Loan Agreement with Pharmakon was $1.1 million and $1.8 million as of June 30, 2022 and December 31, 2021, respectively. The Company classified the derivative liability as a non-current liability on the unaudited condensed consolidated balance sheet as of June 30, 2022. The Company recognized interest expense related to the Loan Agreement of $2.7 million during each of the three months ended June 30, 2022 and 2021, and $5.4 million for each of the six months ended June 30, 2022 and 2021. Second Amendment and Waiver to Loan Agreement with Pharmakon On July 15, 2022, or the Effective Date, the Company and Pharmakon entered into the Second Amendment and Waiver, or the Second Amendment and Waiver, which amends and waives certain provisions of the Loan Agreement, as amended by the First Amendment and Waiver. Pursuant to the Second Amendment and Waiver, on the Effective Date, the Company made a $5.0 million prepayment of the principal of the tranche A loan, or the Second Amendment Effective Date Tranche A Prepayment, and a $20.0 million prepayment of principal of the tranche B loan, or the Second Amendment Effective Date Tranche B Prepayment, in each case, together with any and all accrued and unpaid interest on such prepayments of principal to the Effective Date. In connection therewith, the Company also paid $0.5 million in prepayment premiums under the Loan Agreement. Subject to the payment in full of Second Amendment Effective Date Tranche A Prepayment and the Second Amendment Effective Date Tranche B Prepayment, Pharmakon agreed to, among other things, (1) increase the amount of the working capital facility established in connection with the Company’s Second Amended and Restated License Agreement with Vifor Pharma, which facility is part of the definition of Permitted Indebtedness (as such term is defined in the Loan Agreement) under the Loan Agreement, that the Company is permitted to repay to Vifor Pharma without causing an acceleration of the liabilities under the Loan Agreement, (2) waive the requirement that the Company’s Quarterly Reports on Form 10-Q for the fiscal quarters ending June 30, 2022 and September 30, 2022 not be subject to any qualification as to going concern, and (3) waive certain amounts payable under the Loan Agreement in connection with the Second Amendment Effective Date Tranche B Prepayment. Future principal payments pursuant to the contractual terms of the Loan Agreement, as amended by the Second Amendment and Waiver, are as follows (in thousands): Principal Payments (in thousands) 2022 $ 33,000 2023 32,000 2024 35,000 2025 — 2026 — Thereafter — Total before unamortized discount and issuance costs 100,000 Less: unamortized discount and issuance costs (1,842) Total term loans $ 98,158

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2022
Equity [Abstract]
Stockholders' Equity	Stockholders’ Equity Authorized and Outstanding Capital Stock On June 5, 2020, the Company filed a Certificate of Amendment to its Ninth Amended and Restated Certificate of Incorporation, or its Charter, to increase the number of authorized shares of common stock from 175,000,000 to 350,000,000. As of June 30, 2022, the authorized capital stock of the Company included 350,000,000 shares of common stock, par value $0.00001 per share, of which 183,704,654 and 177,000,963 shares were issued and outstanding as of June 30, 2022 and December 31, 2021, respectively; and 25,000,000 shares of undesignated preferred stock, par value $0.00001 per share, of which no shares were issued and outstanding as of June 30, 2022 and December 31, 2021. At-the-Market Facility On March 12, 2020, the Company filed a prospectus supplement relating to the Company's sales agreement with Cantor Fitzgerald & Co., or the Prior Sales Agreement, pursuant to which it was able to offer and sell up to $65.0 million of its common stock at current market prices from time to time. Through December 31, 2020, the Company sold 3,509,381 shares of common stock under this program with net proceeds (after deducting commissions and other offering expenses) of $10.6 million. During the three months ended March 31, 2021, the Company sold 5,224,278 shares of common stock under this program with net proceeds (after deducting commissions and other offering expenses) of $15.9 million. On February 25, 2021, the Company filed a prospectus relating to the Prior Sales Agreement with its new shelf registration statement (which replaced the prior shelf registration statement and the sales agreement prospectus supplement), pursuant to which it was able to offer and sell up to $100.0 million of its common stock at current market prices from time to time. Through December 31, 2021, the Company sold 21,128,065 shares of common stock under this program with net proceeds (after deducting commissions and other offering expenses) of $72.4 million. On March 1, 2022, the Company filed a prospectus relating to the Prior Sales Agreement, pursuant to which it was authorized to offer and sell up to $25.3 million of its common stock at current market prices from time to time. On March 16, 2022, the Company terminated the Prior Sales Agreement. During the three months ended March 31, 2022, the Company sold 404,600 shares of common stock under this program with net proceeds (after deducting commissions and other offering expenses) of $0.8 million. On April 7, 2022, the Company entered into an Open Market Sale Agreement SM , or the Sales Agreement, with Jefferies LLC, or Jefferies, as agent, for the offer and sale of common stock at current market prices in amounts to be determined from time to time. Also, on April 7, 2022, the Company filed a prospectus supplement relating to the Sales Agreement, pursuant to which it is able to offer and sell under the Sales Agreement up to $26.0 million of its common stock at current market prices from time to time. From the date of filing of the prospectus supplement through the date of the filing of this Quarterly Report on Form 10-Q, the Company has not sold any shares of its common stock under this program. Equity Plans The Company maintains one stock incentive plan, the 2014 Incentive Plan, or the 2014 Plan, as well as the 2014 Employee Stock Purchase Plan, or the 2014 ESPP. The 2014 Plan replaced the Company’s Amended and Restated 2008 Equity Incentive Plan, or the 2008 Plan, however, options or other awards granted under the 2008 Plan prior to the adoption of the 2014 Plan that have not been settled or forfeited remain outstanding and effective. On June 6, 2019, the Company’s stockholders approved the Amended and Restated 2014 Employee Stock Purchase Plan, or the ESPP. The Company also maintains an inducement award program 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 six months ended June 30, 2022, the Company granted 297,000 options to purchase shares of the Company’s common stock to new hires as inducements material to such employees' entering into employment with the Company, of which 174,000 options remained outstanding as of June 30, 2022. The 2014 Plan allows for the granting of stock options, stock appreciation rights, or SARs, restricted stock, unrestricted stock, RSUs, performance awards and other awards convertible into or otherwise based on shares of the Company’s common stock. Dividend equivalents may also be provided in connection with an award under the 2014 Plan. The Company’s employees, officers, directors and consultants and advisors are eligible to receive awards under the 2014 Plan. The Company initially reserved 1,785,000 shares of its common stock for the issuance of awards under the 2014 Plan. The 2014 Plan provides that the number of shares reserved and available for issuance under the 2014 Plan will automatically increase annually on January 1 of each calendar year, by an amount equal to three percent (3%) of the number of the Company's outstanding shares on a fully diluted basis as of the close of business on the immediately preceding December 31, or the 2014 Plan Evergreen Provision. The Company’s Board of Directors may act prior to January 1 of any year to provide that there will be no automatic increase in the number of Akebia Shares available for grant under the 2014 Plan for that year (or that the increase will be less than the amount that would otherwise have automatically been made). On December 12, 2018, in connection with the consummation of the Merger, the Company assumed outstanding and unexercised options to purchase Keryx's stock, as adjusted by the Exchange Multiplier pursuant to the terms of the Merger Agreement, under the following Keryx equity plans, or the Keryx Equity Plans: the Keryx 1999 Share Option Plan, the Keryx 2004 Long-Term Incentive Plan, the Keryx 2007 Incentive Plan, the Keryx Amended and Restated 2013 Incentive Plan, and the Keryx 2018 Equity Incentive Plan, or the Keryx 2018 Plan. In addition, the number of Keryx Shares available for issuance under the Keryx 2018 Plan, as adjusted by the Exchange Multiplier pursuant to the terms of the Merger Agreement, may be used for awards granted by the Company under its 2014 Plan, or the Assumed Shares, provided that the Company uses the Assumed Shares for individuals who were not employees or directors of the Company prior to the consummation of the Merger. The Company grants annual service-based stock options to employees under the 2014 Plan. During the six months ended June 30, 2022, the Company issued 3,233,500 options to employees. In addition, the Company issues stock options to directors, new hires and occasionally to other employees not in connection with the annual grant process. During the six months ended June 30, 2022, the Company issued 140,700 options to directors under the 2014 Plan. Options 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 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 generally expire 10 years after the date of grant. The Company also grants performance-based stock options to employees under the 2014 Plan. The Company issued 400,000 performance-based stock options during the six months ended June 30, 2022. The performance-based stock options granted by the Company generally vest in connection with the achievement of specified commercial and regulatory 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 and regulatory milestones. The Company also grants annual service-based restricted stock units, or RSUs, to employees and directors under the 2014 Plan. The Company also occasionally issues RSUs not in connection with the annual grant process to employees and directors. During the six months ended June 30, 2022, the Company issued 5,212,308 RSUs to employees and 95,900 RSUs to directors under the 2014 Plan. 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 vest on the first anniversary and eight quarterly installments beginning after the one year anniversary, subject, in each case, to the individual’s continued service through the applicable vesting date. 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 on a straight-line basis over the vesting period. The Company also grants performance-based restricted stock units, or PSUs, to employees under the 2014 Plan. The Company issued 400,000 PSUs during the six months ended June 30, 2022. 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.

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Leases The Company leases approximately 65,167 square feet of office and lab space in Cambridge, Massachusetts under a lease which was most recently amended in November 2020, collectively the Cambridge Lease. Under the Third Amendment to the Cambridge Lease, or the Third Amendment, executed in July 2016, total monthly lease payments under the initial base rent were approximately $242,000 and are subject to annual rent escalations. In addition to such annual rent escalations, base rent payments for a portion of said premises commenced on January 1, 2017 in the monthly amount of approximately $22,000. The Fourth Amendment to the Cambridge Lease, executed in May 2017, provided additional storage space to the Company and did not impact rent payments. In April 2018, the Company entered into a Fifth Amendment to the Cambridge Lease, or the Fifth Amendment, for an additional 19,805 square feet of office space on the 12t h floor. Monthly lease payments for the existing 45,362 square feet of office and lab space, under the Third Amendment, remain unchanged. The new space leased by the Company was delivered in September 2018 and additional monthly lease payments of approximately $135,000 commenced in February 2019 and are subject to annual rent escalations, which commenced in September 2019. In November 2020, the Company entered into a Sixth Amendment to the Cambridge Lease, or the Sixth Amendment, to extend the term of the Cambridge Lease with respect to the lab space from November 30, 2021 to January 31, 2025. The Sixth Amendment includes two months of free rent starting in December 2020 and additional monthly lease payments of approximately $48,000, which commenced in December 2021, and is subject to annual rent escalations, which commence in December 2022. Additionally, as a result of the Merger, the Company has a lease for 27,300 square feet of office space in Boston, Massachusetts, or the Boston Lease. The total monthly lease payments under the initial base rent were approximately $136,000 and are subject to annual rent escalations. In February 2022, the Company entered into the First Amendment to the Boston Lease, or the First Lease Amendment, to extend the term of the Boston Lease from February 2023 to July 2031. The First Lease Amendment includes five months of free rent starting in March 2023 and monthly lease payments of $200,122 commencing on August 1, 2023, with an annual rent escalation of approximately 2% commencing on August 1, 2024. The First Lease Amendment also includes a landlord's allowance for certain leasehold improvements to the premises in an amount of up to $1,954,680, provided that such allowance must be used prior to August 1, 2024. The term of the Cambridge Lease with respect to the office space expires on September 11, 2026, with one five-year extension option available. The term of the Boston Lease office space expires on July 31, 2031, with an extension option for one additional five-year term available. The renewal options in these real estate leases were not included in the calculation of the operating lease assets and operating lease liabilities as the renewal is not reasonably certain. The term of the Cambridge Lease with respect to the lab space expires on January 31, 2025, with an extension option for one additional period through September 11, 2026. The renewal option in this real estate lease was included in the calculation of the operating lease assets and operating lease liabilities as the renewal is reasonably certain. The lease agreements do not contain residual value guarantees. Operating lease costs were $1.8 million and $1.7 million for the three months ended June 30, 2022 and 2021, respectively, and $3.6 million and $3.3 million for the six months ended June 30, 2022 and 2021, respectively. Cash paid for amounts included in the measurement of operating lease liabilities was $1.8 million for each of the three months ended June 30, 2022 and 2021 and $3.7 million and $3.5 million for the six months ended June 30, 2022 and 2021, respectively. In September 2019, Keryx entered into an agreement to sublease the Boston office space to Foundation Medicine, Inc., or Foundation. The sublease is subject and subordinate to the Boston Lease between Keryx and the landlord. The term of the sublease commenced on October 16, 2019, upon receipt of the required consent from the landlord for the sublease agreement, and expires on February 27, 2023. Foundation is obligated to pay Keryx rent that approximates the rent due from Keryx to its landlord with respect to the Boston Lease. Sublease rental income is recorded to other income. Keryx continues to be obligated for all payment terms pursuant to the Boston Lease, and the Company will guaranty Keryx’s obligations under the sublease. Keryx recorded $0.4 million in sublease rental income from Foundation during each of the three months ended June 30, 2022 and 2021, respectively, and $0.9 million during each of the six months ended June 30, 2022 and 2021. The Company has not entered into any material short-term leases or financing leases as of June 30, 2022. The total security deposit in connection with the Cambridge Lease is $1.6 million as of June 30, 2022. Additionally, the Company recorded $1.4 million for the security deposit under the Boston Lease. Both the Cambridge Lease and the Boston Lease have their security deposits in the form of a letter of credit, all of which are included as restricted cash in other assets in the Company’s unaudited condensed consolidated balance sheets as of June 30, 2022. As of June 30, 2022, undiscounted minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter are as follows: Operating Lease Payments Net Operating (in thousands) Remaining 2022 $ 3,671 $ 915 $ 2,756 2023 6,954 307 6,647 2024 8,167 — 8,167 2025 8,293 — 8,293 2026 6,571 — 6,571 Thereafter 12,200 — 12,200 Total $ 45,856 $ 1,222 $ 44,634 In arriving at the operating lease liabilities, the Company applied incremental borrowing rates ranging from 6.65% to 7.25%, which were based on the remaining lease term at either the date of adoption of ASC 842 or the effective date of any subsequent lease term extensions. As of June 30, 2022, the remaining lease terms ranged from 4.20 years to 9.09 years. As of June 30, 2022, the following represents the difference between the remaining undiscounted minimum rental commitments under non-cancelable leases and the operating lease liabilities: Operating (in thousands) Undiscounted minimum rental commitments $ 45,856 Present value adjustment using incremental borrowing rate (9,359) Operating lease liabilities $ 36,497 Manufacturing Agreements As a result of the Merger, the Company's contractual obligations include Keryx’s commercial supply agreements with BioVectra Inc., or BioVectra, and Siegfried Evionnaz SA, or Siegfried, to supply commercial drug substance for Auryxia. Pursuant to the Manufacture and Supply Agreement with BioVectra and the Product Manufacture and Supply and Facility Construction Agreement with BioVectra, the Company agreed to purchase minimum quantities of Auryxia drug substance annually at predetermined prices. On September 4, 2020, the Company and BioVectra entered into an Amended and Restated Product Manufacture and Supply and Facility Construction Agreement, which provided for reduced minimum quantity commitments and revised the predetermined prices. The price per kilogram decreases with an increase in quantity above the predetermined purchase quantity tiers. In addition, the Manufacture and Supply Agreement with BioVectra and the Amended and Restated Product Manufacture and Supply and Facility Construction Agreement with BioVectra, require the Company to reimburse BioVectra for certain costs in connection with construction of a new facility for the manufacture and supply of Auryxia drug substance. These construction costs are recorded in other assets and amortized into drug substance as inventory is released to the Company from BioVectra. The term of the Manufacture and Supply Agreement with BioVectra expires on December 31, 2022. The term of the Amended and Restated Product Manufacture and Supply and Facility Construction Agreement expires on December 31, 2026, after which it automatically renews for successive one-year terms unless either party gives notice of its intention to terminate within a specified time prior to the end of the then-current term. In addition, the Company and BioVectra each have the ability to terminate these agreements upon the occurrence of certain conditions. As of June 30, 2022, the Company is required to reimburse BioVectra for certain costs in connection with the construction of the new facility and to purchase minimum quantities of Auryxia drug substance annually for a total cost of approximately $82.4 million through the end of the contract term. Pursuant to the Siegfried Master Manufacturing Services and Supply Agreement, as amended (the most recent amendment having been executed on February 11, 2021), or the Siegfried Agreement, the Company has agreed to purchase a minimum quantity of drug substance of Auryxia at predetermined prices. The price per kilogram will decrease with an increase in quantity above the minimum purchase quantity. The term of the Siegfried Agreement expires on December 31, 2022, subject to the Company's option to extend the term through December 31, 2023 by providing 12 months’ prior written notice to Siegfried. The Siegfried Agreement provides the Company and Siegfried with certain early termination rights. In the first quarter of 2022, the Company notified Siegfried that the Company has elected not to exercise the option to extend the term of the Siegfried Agreement through December 31, 2023. As of June 30, 2022, the Company is required to purchase a minimum quantity of drug substance for Auryxia annually at a total cost of approximately $10.5 million through the year ending December 31, 2022. The Company has executory contracts in the commercial supply agreements between Keryx and its contract manufacturers for Auryxia, which include future firm purchase commitments. These executory contracts were deemed to have an off-market element related to the amount of purchase commitments that exceed the current forecast. The Company regularly reviews its estimate of the excess purchase commitment liability including a review of assumptions of expected future demand, estimates of anticipated expiry of inventory under firm purchase commitments that are estimated to expire before they could be sold as well as any modifications to supply agreements during each reporting period. The excess purchase commitment liability relating to these executory contracts was $66.9 million and $76.7 million as of June 30, 2022 and December 31, 2021, respectively. During the quarter ended June 30, 2022, the Company reviewed the detailed assumptions above and reduced the excess purchase commitment liability by $5.8 million for inventory received that had been previously identified as excess. During the quarter ended March 31, 2022, the Company recorded a $0.8 million reduction to the excess purchase commitments liability within cost of goods sold and reduced the excess purchase commitment liability by $3.2 million for inventory received that had previously been identified as excess. On April 9, 2019, the Company entered into a Supply Agreement with Esteve Química, S.A., or Esteve, or the Esteve Agreement. The Esteve Agreement includes the terms and conditions under which Esteve will manufacture vadadustat drug substance for commercial use. Pursuant to the Esteve Agreement, the Company provides rolling forecasts to Esteve on a quarterly basis, or the Esteve Forecast. The Esteve Forecast reflects the Company’s needs for vadadustat drug substance produced by Esteve over a certain number of months, represented as a quantity of vadadustat drug substance per calendar quarter. The parties have agreed to a volume-based pricing structure under the Esteve Agreement. The Esteve Agreement has an initial term of four years, beginning April 9, 2019 and ending April 9, 2023. Pursuant to the Esteve Agreement, the Company has agreed to purchase a certain percentage of the global demand for vadadustat drug substance from Esteve. As of June 30, 2022, the Company has committed to purchase $32.4 million of vadadustat drug substance from Esteve through the second quarter of 2023. On March 11, 2020, the Company entered into a Supply Agreement with Patheon Inc., or Patheon, or the Patheon Agreement. The Patheon Agreement includes the terms and conditions under which Patheon will manufacture vadadustat drug product for commercial use. Pursuant to the Patheon Agreement, the Company provides Patheon a long-term forecast on an annual basis, as well as short-term forecasts on a quarterly basis, or the Patheon Forecast. The Patheon Forecast reflects the Company’s needs for commercial supply of vadadustat drug product produced by Patheon, represented as a quantity of drug product per calendar quarter. The parties have agreed to a volume-based pricing structure under the Patheon Agreement. The Patheon Agreement has an initial term beginning March 11, 2020 and ending June 30, 2023. Pursuant to the Patheon Agreement, the Company has agreed to purchase a certain percentage of the global demand for vadadustat drug product from Patheon. As of June 30, 2022, the Company had a minimum commitment with Patheon for $3.3 million through the fourth quarter of 2022. On April 2, 2020, the Company entered into a Supply Agreement with STA Pharmaceutical Hong Kong Limited, a subsidiary of WuXi AppTec, or WuXi STA, as amended on April 15, 2021, or the WuXi STA DS Agreement. The WuXi STA DS Agreement includes the terms and conditions under which WuXi STA will manufacture vadadustat drug substance for commercial use. Pursuant to the WuXi STA DS Agreement, the Company provides rolling forecasts to WuXi STA on a quarterly basis, or the WuXi STA DS Forecast. The WuXi STA DS Forecast reflects the Company’s needs for vadadustat drug substance produced by WuXi STA over a certain number of quarters. The parties have agreed to a volume-based pricing structure under the WuXi STA DS Agreement. The WuXi STA DS Agreement has an initial term of four years, beginning April 2, 2020 and ending April 2, 2024. Pursuant to the WuXi STA DS Agreement, the Company has agreed to purchase a certain percentage of the global demand for vadadustat drug substance from WuXi STA. As of June 30, 2022, the Company has committed to purchase $62.0 million of vadadustat drug substance from WuXi STA through the end of 2023. On February 10, 2021, the Company entered into a Supply Agreement with WuXi STA, or the WuXi STA DP Agreement. The WuXi STA DP Agreement includes the terms and conditions under which WuXi STA will manufacture and supply vadadustat drug product for commercial purposes. Pursuant to the WuXi STA DP Agreement, the Company will provide rolling forecasts to WuXi STA on a quarterly basis, or the WuXi STA DP Forecast. Each WuXi STA DP Forecast will reflect the quantities of vadadustat drug product that the Company expects to order from WuXi STA over a certain number of months, represented as a quantity of vadadustat drug product per calendar quarter. Pursuant to the WuXi STA DP Agreement, the Company has agreed to purchase a certain percentage of global demand for vadadustat drug product from WuXi STA. The parties have agreed to a volume-based pricing structure under the WuXi STA DP Agreement. The vadadustat drug product price will remain fixed for the first 12 months and thereafter shall be annually reviewed by the Company and WuXi STA. The Company will also reimburse WuXi STA for certain reasonable expenses. The WuXi STA DP Agreement has an initial term of four years, beginning February 10, 2021 and ending February 10, 2025. The WuXi STA DP Agreement may be renewed or extended by mutual agreement of the Company and WuXi STA with at least 18 months’ prior written notice. The WuXi STA DP Agreement allows the Company to terminate the agreement 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. Other Third-Party Contracts Under the Company’s agreement with IQVIA to provide contract research organization services for the PRO 2 TECT and INNO 2 VATE programs, the total remaining contract costs as of June 30, 2022 were approximately $4.6 million. Substantive performance for the committed work with IQVIA was completed in 2020 and close out activities will be performed throughout 2022. The Company also contracts with various other organizations to conduct research and development activities with remaining contract costs to the Company of approximately $175.7 million at June 30, 2022. The scope of the services under these research and development contracts can be modified and the contracts 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 From time to time, the Company may become subject to legal proceedings and claims which arise in the ordinary course of its business. Consistent with ASC 450, Contingencies , the Company’s policy is to record a liability if a loss in a significant legal dispute is considered probable and an amount can be reasonably estimated. 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. The Company’s estimates change as litigation progresses and new information comes to light. Changes in Company estimates could have a material impact on the Company’s results and financial position. As of June 30, 2022, the Company does not have any significant legal disputes that require a loss liability to be recorded. The Company continually monitors the need for a loss liability for litigation and related matters.

Net Loss per Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2022
Earnings Per Share [Abstract]
Net Loss per Share	Net Loss per Share For purposes of the diluted net income (loss) per share calculation for the three and six months ended June 30, 2022, as well as the three and six months ended June 30, 2021, preferred stock, stock options, warrants, restricted stock and RSUs are considered to be common stock equivalents and have been excluded from the calculation of diluted net income (loss) per share, as their effect would be anti-dilutive for periods presented. Therefore, basic and diluted net loss per share were the same for all periods presented in the unaudited condensed consolidated statement of operations and comprehensive loss, except for the three months ended June 30, 2022, as the Company had net income for the period. The shares in the table below were excluded from the calculation of diluted net income (loss) per share, prior to the use of the treasury stock method, due to their anti-dilutive effect: Three Months Ended Six Months Ended 2022 2021 2022 2021 Warrant — 509,611 — 509,611 Outstanding stock options 13,502,015 11,532,673 13,508,217 11,532,673 Unvested restricted stock units — 5,574,476 6,771,349 5,574,476 Total 13,502,015 17,616,760 20,279,566 17,616,760

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2022
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Second Amendment and Waiver to Loan Agreement with Pharmakon On July 15, 2022, the Company and Pharmakon entered into the Second Amendment and Waiver, which amends and waives certain provisions of the Loan Agreement, as amended by the First Amendment and Waiver. Refer to Note 11 in this Quarterly Report on Form 10-Q for further details.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the U.S., or GAAP, for interim financial reporting and as required by Regulation S-X, Rule 10-01. Accordingly, they do not include all of the information and footnotes required by GAAP for complete financial statements. Any reference in these notes to applicable guidance is meant to refer to the authoritative GAAP as found in the ASC and Accounting Standards Update, or ASU, of the Financial Accounting Standards Board, or FASB.
Consolidation	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 and six months ended June 30, 2022 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2022 or any other future period.The accompanying unaudited condensed consolidated financial statements include the accounts of the Company and its wholly-owned subsidiaries. All intercompany balances and transactions have been eliminated in consolidation.
New Accounting Pronouncements - Not Yet Adopted	New Accounting Pronouncements – Not Yet Adopted In March 2020, the FASB issued ASU 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting . The amendments provide optional guidance for a limited time to ease the potential burden in accounting for reference rate reform. The new guidance provides optional expedients and exceptions for applying GAAP to contracts, hedging relationships and other transactions affected by reference rate reform if certain criteria are met. The amendments apply only to contracts and hedging relationships that reference LIBOR or another reference rate expected to be discontinued due to reference rate reform. These amendments are effective immediately and may be applied prospectively to contract modifications made and hedging relationships entered into or evaluated on or before December 31, 2022. The Company is currently evaluating its contracts and the optional expedients provided by the new standard.
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 and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results may differ from those estimates. Management considers many factors in selecting appropriate financial accounting policies and controls, and in developing the estimates and assumptions that are used in the preparation of these financial statements. Management must apply significant judgment in this process. In addition, other factors may affect estimates, including expected business and operational changes, sensitivity and volatility associated with the assumptions used in developing estimates, and whether historical trends are expected to be representative of future trends. The estimation process often may yield a range of potentially reasonable estimates of the ultimate future outcomes, and management must select an amount that falls within that range of reasonable estimates. Estimates are used in the following areas, among others: prepaid and accrued research and development expense, operating lease assets and liabilities, derivative liabilities, refund liabilities to customers, other non-current liabilities, including the excess purchase commitment liability, stock-based compensation expense, product and collaboration revenues including various rebates and reserves related to product sales, non-cash interest expense on the liability related to sale of future royalties, inventories, income taxes, intangible assets and goodwill. 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. The Company bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances.

Product Revenue and Reserves _2

Product Revenue and Reserves for Variable Consideration (Tables)	6 Months Ended
	Jun. 30, 2022
Revenue from Contract with Customer [Abstract]
Product Revenue Allowance and Reserve Categories	The following table summarizes activity in each of the product revenue allowance and reserve categories for the six months ended June 30, 2022 and 2021 (in thousands): Chargebacks Rebates, Fees Returns Total Balance at December 31, 2021 $ 1,278 $ 26,625 $ 475 $ 28,378 Current provisions related to sales in current year 4,928 42,566 2,871 50,365 Adjustments related to prior year sales 131 784 — 915 Credits/payments made (5,236) (43,803) (2,804) (51,843) Balance at June 30, 2022 $ 1,101 $ 26,172 $ 542 $ 27,815 Balance at December 31, 2020 $ 802 $ 39,912 $ 649 $ 41,363 Current provisions related to sales in current year 6,084 69,163 3,616 78,863 Adjustments related to prior year sales (6) 812 — 806 Credits/payments made (5,588) (63,795) (3,715) (73,098) Balance at June 30, 2021 $ 1,292 $ 46,092 $ 550 $ 47,934

License, Collaboration and Ot_2

License, Collaboration and Other Significant Agreements (Tables)	6 Months Ended
	Jun. 30, 2022
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Revenues Recognized from License, Collaboration and Other Significant Agreements	During the three and six months ended June 30, 2022 and 2021, the Company recognized the following revenues from its license, collaboration and other significant agreements and had the following deferred revenue balances as of June 30, 2022: Three Months Ended June 30, Six Months Ended June 30, 2022 2021 2022 2021 License, Collaboration and Other Revenue: (in thousands) (in thousands) MTPC Agreement $ 434 $ 4,594 $ 8,398 $ 4,612 Otsuka U.S. Agreement 81,135 9,170 86,773 22,844 Otsuka International Agreement — 4,700 5,503 11,672 Total Proportional Performance Revenue $ 81,569 $ 18,464 $ 100,674 $ 39,128 JT and Torii 1,487 1,490 2,633 2,649 MTPC Other Revenue — — — 73 Total License, Collaboration and Other Revenue $ 83,056 $ 19,954 $ 103,307 $ 41,850
Deferred Revenues	During the three and six months ended June 30, 2022 and 2021, the Company recognized the following revenues from its license, collaboration and other significant agreements and had the following deferred revenue balances as of June 30, 2022: June 30, 2022 Short-Term Long-Term Total Deferred Revenue: (in thousands) MTPC Agreement $ 5,047 $ — $ 5,047 Vifor Pharma Agreement — 43,296 43,296 Total $ 5,047 $ 43,296 $ 48,343
Changes in Contract Assets and Liabilities	The following table presents changes in the Company’s contract assets and liabilities during the six months ended June 30, 2022 and 2021 (in thousands): Six Months Ended June 30, 2022 Balance at Additions Deductions Balance at End Contract assets: Accounts receivable(1) $ 19,094 $ 92,146 $ (54,614) $ 56,626 Prepaid expenses and other current assets $ 4,309 $ 9,550 $ (4,309) $ 9,550 Contract liabilities: Deferred revenue $ 42,380 $ 65,042 $ (59,079) $ 48,343 Accounts payable $ 3,171 $ — $ (3,171) $ — Accrued expenses and other current liabilities $ — $ — $ — $ — Six Months Ended June 30, 2021 Contract assets: Accounts receivable(1) $ 3,045 $ 18,884 $ (19,112) $ 2,817 Prepaid expenses and other current assets $ 1,722 $ 211 $ (5) $ 1,928 Contract liabilities: Deferred revenue $ 40,559 $ 36,679 $ (48,770) $ 28,468 Accounts payable $ 7,227 $ — $ (7,227) $ — Accrued expenses and other current liabilities $ 10,000 $ — $ — $ 10,000 (1) Excludes accounts receivable from other services related to clinical and regulatory activities performed by the Company on behalf of MTPC that are not included in the performance obligations identified under the MTPC Agreement as of June 30, 2022 and 2021 and December 31, 2021 and 2020. Also excludes accounts receivable related to amounts due to the Company from product sales which are included in the accompanying unaudited condensed consolidated balance sheet as of June 30, 2022 and December 31, 2021.
Revenue Recognized Resulting from Changes in Contract Assets and Contract Liabilities	During the three and six months ended June 30, 2022 and 2021, 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 June 30, Six Months Ended June 30, Revenue Recognized in the Period: 2022 2021 2022 2021 Amounts included in deferred revenue at the beginning of the period $ 15,503 $ 5,822 $ 22,105 $ 10,895 Performance obligations satisfied in previous periods $ — $ — $ — $ —

Restructuring (Tables)

Restructuring (Tables)	6 Months Ended
	Jun. 30, 2022
Restructuring and Related Activities [Abstract]
Restructuring Reserve Activity	Details of the restructuring liability activity for the Company's workforce reduction for the period ended June 30, 2022 are as follows: June 30, 2022 (in thousands) Balance at December 31, 2021 $ — Restructuring charges 14,531 Stock-based compensation expense (3,303) Severance payments and adjustments (4,313) Balance at June 30, 2022 $ 6,915

Liability Related to Sale of _2

Liability Related to Sale of Future Royalties (Tables)	6 Months Ended
	Jun. 30, 2022
Other Liabilities Disclosure [Abstract]
Activity within Liability Related to Sale of Future Royalties, net	The following table shows the activity within the liability account for the six months ended June 30, 2022: June 30, 2022 (in thousands) Liability related to sale of future royalties, net beginning balance at December 31, 2021 $ 53,079 MTPC royalties payable (764) Non-cash interest expense recognized 4,428 Liability related to sale of future royalties, net — ending balance $ 56,743

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	6 Months Ended
	Jun. 30, 2022
Fair Value Disclosures [Abstract]
Assets Measured or Disclosed at Fair Value on Recurring Basis	Assets measured or disclosed at fair value on a recurring basis as of June 30, 2022 and December 31, 2021 are summarized below: Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) June 30, 2022 Assets: Cash and cash equivalents $ 143,893 $ — $ — $ 143,893 $ 143,893 $ — $ — $ 143,893 Liabilities: Derivative liability $ — $ — $ 1,110 $ 1,110 $ — $ — $ 1,110 $ 1,110 Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) December 31, 2021 Assets: Cash and cash equivalents $ 149,800 $ — $ — $ 149,800 $ 149,800 $ — $ — $ 149,800 Liabilities: Derivative liability $ — $ — $ 1,820 $ 1,820 $ — $ — $ 1,820 $ 1,820
Fair Value Derivative Liability	The following table provides a roll-forward of the fair value of the derivative liability (in thousands): Balance at December 31, 2021 $ 1,820 Change in fair value of derivative liability, recorded as other income (710) Balance at March 31, 2022 $ 1,110 Change in fair value of derivative liability, recorded as other income — Balance at June 30, 2022 $ 1,110

Inventory (Tables)

Inventory (Tables)	6 Months Ended
	Jun. 30, 2022
Inventory Disclosure [Abstract]
Inventory Components	The components of inventory are summarized as follows: June 30, 2022 December 31, 2021 (in thousands) Raw materials $ 757 $ 1,763 Work in process 38,466 62,635 Finished goods 18,843 14,661 Total inventory $ 58,066 $ 79,059 Long-term inventory, which primarily consists of raw materials and work in process, is included in other assets in the Company’s unaudited condensed consolidated balance sheets. June 30, 2022 December 31, 2021 (in thousands) Balance Sheet Classification: Inventory $ 36,272 $ 38,195 Other assets 21,794 40,864 Total inventory $ 58,066 $ 79,059

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	6 Months Ended
	Jun. 30, 2022
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets	The following table presents the Company’s intangible assets at June 30, 2022 and December 31, 2021 (in thousands): June 30, 2022 Gross Carrying Accumulated Amortization Total Intangible assets: Developed product rights for Auryxia $ 213,603 $ (123,497) $ 90,106 Total $ 213,603 $ (123,497) $ 90,106 December 31, 2021 Gross Carrying Accumulated Total Intangible assets: Developed product rights for Auryxia $ 213,603 $ (105,476) $ 108,127 Total $ 213,603 $ (105,476) $ 108,127

Accrued Expenses (Tables)

Accrued Expenses (Tables)	6 Months Ended
	Jun. 30, 2022
Payables and Accruals [Abstract]
Accrued Expenses	Accrued expenses as of June 30, 2022 and December 31, 2021 are as follows: June 30, 2022 December 31, 2021 (in thousands) Product revenue allowances $ 26,171 $ 26,624 Accrued clinical 7,622 14,036 Amounts due to collaboration partners 20,797 22,654 Accrued payroll and related 6,883 15,863 Lease liability 4,422 4,802 Royalties 3,457 3,472 Professional fees 1,815 1,899 Accrued commercial manufacturing 3,420 3,843 Accrued restructuring 6,915 — Accrued other 9,782 11,263 Total accrued expenses $ 91,284 $ 104,456

Debt (Tables)

Debt (Tables)	6 Months Ended
	Jun. 30, 2022
Debt Disclosure [Abstract]
Schedule of Future Principal Payments on the Term Loans	Future principal payments pursuant to the contractual terms of the Loan Agreement, as amended by the Second Amendment and Waiver, are as follows (in thousands): Principal Payments (in thousands) 2022 $ 33,000 2023 32,000 2024 35,000 2025 — 2026 — Thereafter — Total before unamortized discount and issuance costs 100,000 Less: unamortized discount and issuance costs (1,842) Total term loans $ 98,158

Commitments and Contingencies (

Commitments and Contingencies (Tables)	6 Months Ended
	Jun. 30, 2022
Commitments and Contingencies Disclosure [Abstract]
Undiscounted Minimum Rental Commitments Under Non-Cancelable Leases	As of June 30, 2022, undiscounted minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter are as follows: Operating Lease Payments Net Operating (in thousands) Remaining 2022 $ 3,671 $ 915 $ 2,756 2023 6,954 307 6,647 2024 8,167 — 8,167 2025 8,293 — 8,293 2026 6,571 — 6,571 Thereafter 12,200 — 12,200 Total $ 45,856 $ 1,222 $ 44,634
Difference Between Undiscounted Minimum Rental Commitments Under Non-Cancelable Leases and Operating Leases Liabilities	As of June 30, 2022, the following represents the difference between the remaining undiscounted minimum rental commitments under non-cancelable leases and the operating lease liabilities: Operating (in thousands) Undiscounted minimum rental commitments $ 45,856 Present value adjustment using incremental borrowing rate (9,359) Operating lease liabilities $ 36,497

Net Loss per Share (Tables)

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2022
Earnings Per Share [Abstract]
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 income (loss) per share, prior to the use of the treasury stock method, due to their anti-dilutive effect: Three Months Ended Six Months Ended 2022 2021 2022 2021 Warrant — 509,611 — 509,611 Outstanding stock options 13,502,015 11,532,673 13,508,217 11,532,673 Unvested restricted stock units — 5,574,476 6,771,349 5,574,476 Total 13,502,015 17,616,760 20,279,566 17,616,760

Nature of Organization and Op_2

Nature of Organization and Operations (Details) - USD ($) $ in Thousands	Jul. 15, 2022	Jun. 30, 2022	Dec. 31, 2021
Line of Credit Facility [Line Items]
Cash and cash equivalents		$ 143,893	$ 149,800
Term Loan | Tranche A and B | Collateral Agent, Pharmakon | Subsequent Event
Line of Credit Facility [Line Items]
Payment for debt prepayment	$ 25,000
Payment for debt prepayment premium, including accrued and unpaid interest	$ 500

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Details)	6 Months Ended
	Jun. 30, 2022 segment
Accounting Policies [Abstract]
Number of operating segments	1

Product Revenue and Reserves _3

Product Revenue and Reserves for Variable Consideration - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 126,759	$ 52,913	$ 188,458	$ 105,217
Product revenue, net
Disaggregation of Revenue [Line Items]
Total revenues	43,703	$ 32,959	85,151	$ 63,367
Accounts receivable, net	$ 24,800		$ 24,800		$ 24,600

Product Revenue and Reserves _4

Product Revenue and Reserves for Variable Consideration - Product Revenue Allowance and Reserve Categories (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	$ 28,378	$ 41,363
Current provisions related to sales in current year	50,365	78,863
Adjustments related to prior year sales	915	806
Credits/payments made	(51,843)	(73,098)
Ending balance	27,815	47,934
Chargebacks and Discounts
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	1,278	802
Current provisions related to sales in current year	4,928	6,084
Adjustments related to prior year sales	131	(6)
Credits/payments made	(5,236)	(5,588)
Ending balance	1,101	1,292
Rebates, Fees and other Deductions
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	26,625	39,912
Current provisions related to sales in current year	42,566	69,163
Adjustments related to prior year sales	784	812
Credits/payments made	(43,803)	(63,795)
Ending balance	26,172	46,092
Returns
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning balance	475	649
Current provisions related to sales in current year	2,871	3,616
Adjustments related to prior year sales	0	0
Credits/payments made	(2,804)	(3,715)
Ending balance	$ 542	$ 550

License, Collaboration and Ot_3

License, Collaboration and Other Significant Agreements - Revenues Recognized From License, Collaboration and Other Significant Agreements (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
License, Collaboration and Other Revenue:
Total revenues	$ 126,759	$ 52,913	$ 188,458	$ 105,217
Mitsubishi Tanabe Pharma Corporation
License, Collaboration and Other Revenue:
Total revenues			2,000
License, collaboration and other revenue
License, Collaboration and Other Revenue:
Total revenues	83,056	19,954	103,307	41,850
License, collaboration and other revenue | Mitsubishi Tanabe Pharma Corporation
License, Collaboration and Other Revenue:
Total revenues	434	4,594	8,398	4,612
License, collaboration and other revenue | Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement
License, Collaboration and Other Revenue:
Total revenues	81,135	9,170	86,773	22,844
License, collaboration and other revenue | Otsuka Pharmaceutical Company. Ltd. | Otsuka International Agreement
License, Collaboration and Other Revenue:
Total revenues	0	4,700	5,503	11,672
License, collaboration and other revenue | Total Proportional Performance Revenue
License, Collaboration and Other Revenue:
Total revenues	81,569	18,464	100,674	39,128
License, collaboration and other revenue | JT and Torii
License, Collaboration and Other Revenue:
Total revenues	1,487	1,490	2,633	2,649
License, collaboration and other revenue | MTPC Other Revenue | Mitsubishi Tanabe Pharma Corporation
License, Collaboration and Other Revenue:
Total revenues	$ 0	$ 0	$ 0	$ 73

License, Collaboration and Ot_4

License, Collaboration and Other Significant Agreements - Deferred Revenue (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Deferred Revenue:
Short-Term	$ 5,047	$ 20,906
Long-Term	43,296	$ 21,474
Total	48,343
Mitsubishi Tanabe Pharma Corporation | MTPC Agreement
Deferred Revenue:
Short-Term	5,047
Long-Term	0
Total	5,047
Vifor Pharma
Deferred Revenue:
Short-Term	0
Long-Term	43,296
Total	$ 43,296

License, Collaboration and Ot_5

License, Collaboration and Other Significant Agreements - Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Contract liabilities:
Balance at End of Period	$ 48,343
Accounts receivable
Contract assets:
Balance at Beginning of Period	19,094	$ 3,045
Additions	92,146	18,884
Deductions	(54,614)	(19,112)
Balance at End of Period	56,626	2,817
Prepaid expenses and other current assets
Contract assets:
Balance at Beginning of Period	4,309	1,722
Additions	9,550	211
Deductions	(4,309)	(5)
Balance at End of Period	9,550	1,928
Deferred revenue
Contract liabilities:
Balance at Beginning of Period	42,380	40,559
Additions	65,042	36,679
Deductions	(59,079)	(48,770)
Balance at End of Period	48,343	28,468
Accounts payable
Contract liabilities:
Balance at Beginning of Period	3,171	7,227
Additions	0	0
Deductions	(3,171)	(7,227)
Balance at End of Period	0	0
Accrued expenses and other current liabilities
Contract liabilities:
Balance at Beginning of Period	0	10,000
Additions	0	0
Deductions	0	0
Balance at End of Period	$ 0	$ 10,000

License, Collaboration and Ot_6

License, Collaboration and Other Significant Agreements - Revenue Recognized Resulting from Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Revenue Recognized in the Period:
Amounts included in deferred revenue at the beginning of the period	$ 15,503	$ 5,822	$ 22,105	$ 10,895
Performance obligations satisfied in previous periods	$ 0	$ 0	$ 0	$ 0

License, Collaboration and Ot_7

License, Collaboration and Other Significant Agreements - Mitsubishi Tanabe Pharma Corporation Collaboration Agreement (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) performance_obligation	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue	$ 126,759,000	$ 52,913,000	$ 188,458,000	$ 105,217,000
Deferred revenue	48,343,000		48,343,000
Revenue recognized	15,503,000	5,822,000	22,105,000	10,895,000
Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	56,626,000	2,817,000	56,626,000	2,817,000	$ 19,094,000	$ 3,045,000
Mitsubishi Tanabe Pharma Corporation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue			2,000,000
Mitsubishi Tanabe Pharma Corporation | License Collaboration And Other Revenue, Royalties
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue	400,000	100,000	700,000	100,000
Mitsubishi Tanabe Pharma Corporation | Regulatory Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone revenue			$ 25,000,000
Mitsubishi Tanabe Pharma Corporation | MTPC Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of performance obligations | performance_obligation			2
Deferred revenue	5,047,000		$ 5,047,000
Mitsubishi Tanabe Pharma Corporation | MTPC Agreement | Regulatory Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone revenue			15,000,000
Mitsubishi Tanabe Pharma Corporation | Development And Commercialize Research And License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment received			20,000,000
Cost of research services			20,500,000
Milestone revenue			10,000,000
Accounts receivable	0		0
Deferred revenue	0		0
Mitsubishi Tanabe Pharma Corporation | Development And Commercialize Research And License Agreement | Regulatory Milestone Payments
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Milestone revenue			10,000,000
Mitsubishi Tanabe Pharma Corporation | Mitsubishi Tanabe Pharma Corporation And Otsuka Pharmaceutical Company Limited | Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	200,000		200,000
Mitsubishi Tanabe Pharma Corporation | Mitsubishi Tanabe Pharma Corporation Supply Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue recognized	0	$ 4,500,000	7,600,000	$ 4,500,000
Mitsubishi Tanabe Pharma Corporation | Mitsubishi Tanabe Pharma Corporation Supply Agreement | Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Up-front payments invoiced	400,000		400,000
Mitsubishi Tanabe Pharma Corporation | Mitsubishi Tanabe Pharma Corporation Supply Agreement | Contract With Customer, Liability
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Up-front payments invoiced	5,000,000		5,000,000
Mitsubishi Tanabe Pharma Corporation | Mitsubishi Tanabe Pharma Corporation Supply Agreement | Other Current Liabilities
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Up-front payments invoiced	19,500,000		19,500,000
Mitsubishi Tanabe Pharma Corporation | Mitsubishi Tanabe Pharma Corporation Supply Agreement | Other Noncurrent Liabilities
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Up-front payments invoiced	$ 0		$ 0

License, Collaboration and Ot_8

License, Collaboration and Other Significant Agreements - U.S. Collaboration and License Agreement with Otsuka Pharmaceutical Co. Ltd. (Details)		1 Months Ended	3 Months Ended		6 Months Ended
	Dec. 31, 2016 USD ($)	Jul. 31, 2022 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) performance_obligation	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)	Apr. 01, 2019	Mar. 31, 2019
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue			$ 126,759,000	$ 52,913,000	$ 188,458,000	$ 105,217,000
Revenue recognized			15,503,000	5,822,000	22,105,000	10,895,000
Non cash revenue recognized					9,550,000	0
Deferred revenue			48,343,000		48,343,000
Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable			56,626,000	2,817,000	56,626,000	2,817,000	$ 19,094,000	$ 3,045,000
Prepaid expenses and other current assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable			9,550,000	1,928,000	9,550,000	1,928,000	4,309,000	1,722,000
Accounts payable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue			0	0	0	0	3,171,000	$ 7,227,000
License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue			83,056,000	19,954,000	103,307,000	41,850,000
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. and International Agreement | License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue					$ 92,300,000
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of performance obligations | performance_obligation					3
Percentage of costs funded by customer									80%	52.50%
Reimbursement of costs	$ 33,800,000
Collaborative arrangements cost sharing payments					$ 319,200,000
Revenue recognized			15,500,000
Non cash revenue recognized			9,600,000
Deferred revenue			0		0
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement | Subsequent Event
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Cumulative catch-up adjustment to revenue, modification of contract		$ 55,000,000
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement | Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable			55,000,000		55,000,000
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement | Prepaid expenses and other current assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable			9,600,000		9,600,000		3,000,000
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement | Accounts payable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue							$ 2,000,000
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement | License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue			$ 81,135,000	$ 9,170,000	86,773,000	$ 22,844,000
Otsuka Pharmaceutical Company. Ltd. | Otsuka U.S. Agreement | Up Front Non Refundable And Non Creditable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment received					$ 125,000,000

License, Collaboration and Ot_9

License, Collaboration and Other Significant Agreements - International Collaboration and License Agreement with Otsuka Pharmaceutical Co. Ltd. (Details) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Mar. 31, 2017 USD ($)	Jun. 30, 2022 USD ($) performance_obligation	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue	$ 126,759	$ 52,913		$ 188,458	$ 105,217
Deferred revenue	48,343			48,343
Short-term deferred revenue	5,047			5,047		$ 20,906
Deferred revenue, net of current portion	43,296			43,296		21,474
Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	56,626	2,817		56,626	2,817	19,094	$ 3,045
Prepaid expenses and other current assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	9,550	1,928		9,550	1,928	4,309	1,722
Accounts payable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue	0	0		0	0	3,171	$ 7,227
License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue	83,056	19,954		$ 103,307	41,850
Otsuka Pharmaceutical Company. Ltd. | Otsuka International Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of performance obligations | performance_obligation				3
Reimbursement of costs			$ 200
Estimated current global development costs subsequent to March 31, 2017				$ 216,700
Deferred revenue	0			0
Otsuka Pharmaceutical Company. Ltd. | Otsuka International Agreement | Accounts receivable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	0			0
Otsuka Pharmaceutical Company. Ltd. | Otsuka International Agreement | Prepaid expenses and other current assets
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Accounts receivable	0			0		1,300
Otsuka Pharmaceutical Company. Ltd. | Otsuka International Agreement | Accounts payable
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Deferred revenue						$ 900
Otsuka Pharmaceutical Company. Ltd. | Otsuka International Agreement | License, collaboration and other revenue
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Recognized revenue	$ 0	$ 4,700		5,503	$ 11,672
Otsuka Pharmaceutical Company. Ltd. | Up Front Non Refundable And Non Creditable | Otsuka International Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront cash payment received				$ 73,000

License, Collaboration and O_10

License, Collaboration and Other Significant Agreements - Janssen Pharmaceutica NV Research and License Agreement (Details) - Development And Commercialize Research And License Agreement $ in Millions	Feb. 09, 2017 USD ($) shares
Janssen Pharmaceutica NV
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Collaborative arrangement, term	3 years
Upfront payment made in cash	$ 1
Potential milestone revenue from developmental milestones (up to)	16.5
Potential milestone revenue from commercial milestones (up to)	$ 215
Johnson & Johnson Innovation
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Warrant to purchase common stock (in shares) | shares	509,611

License, Collaboration and O_11

License, Collaboration and Other Significant Agreements - Cyclerion Therapeutics License Agreement (Details) - Cyclerion Therapeutics License Agreement $ in Millions	Jun. 04, 2021 USD ($)
Asset Acquisition [Line Items]
Upfront payment for asset acquisition	$ 3
Contingent consideration from developmental and regulatory milestones	$ 222

License, Collaboration and O_12

License, Collaboration and Other Significant Agreements - Vifor Pharma License Agreement (Details) $ / shares in Units, $ in Thousands					1 Months Ended	3 Months Ended		6 Months Ended
	Feb. 22, 2022 USD ($) shares	Feb. 18, 2022 USD ($)	Feb. 14, 2020 USD ($)	Apr. 08, 2019 USD ($)	May 31, 2017 USD ($) $ / shares shares	Jun. 30, 2022 USD ($) shares	Dec. 31, 2021 USD ($) shares	Jun. 30, 2022 USD ($) performance_obligation shares	May 12, 2017 USD ($)
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Upfront payment						$ 48,343		$ 48,343
Common stock, issued (in shares) | shares						183,704,654	177,000,963	183,704,654
Refund liability to customer, amortization of discount						$ 1,100		$ 1,100
Refund liability to customer, amortization of deferred gain						800		800
Current portion of refund liability to customer						14,247	$ 0	14,247
Vifor (International) Ltd.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract termination, prior written notice period		30 months
Private Placement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Number of shares sold in offering (in shares) | shares	4,000,000
Aggregate net proceeds from offering	$ 20,000
Aggregate net proceeds from offering, fair value in excess of carrying amount	$ 13,600
Vifor (International) Ltd.
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Contract termination, prior written notice period		6 months
Refund liability to customer, gross						40,000		40,000
Refund liability to customer, net of deferred gain and discount						$ 40,300		$ 40,300
Vifor (International) Ltd. | License
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Revenue, remaining performance obligation, profit share percentage		66%
Upfront payment		$ 25,000
Number of performance obligations | performance_obligation								1
Refund liability to customer, purchase orders to total						50%		50%
Refund liability to customer, interest rate						15%		15%
Vifor (International) Ltd. | License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Potential milestone revenue				$ 25,000
Common stock, issued (in shares) | shares					3,571,429
Sale of stock, price per share (in dollars per share) | $ / shares					$ 14
Proceeds from common stock sold					$ 50,000
Premium over the closing stock price of common stock (in dollars per share) | $ / shares					$ 12.69
Premium amount over the closing stock price of common stock					$ 4,700				$ 4,700
Vifor (International) Ltd. | Priority Review Voucher Letter Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Payments for closing Priority Review Voucher purchase			$ 10,000
Proceeds from collaborators							$ 8,600

License, Collaboration and O_13

License, Collaboration and Other Significant Agreements - License Agreement with Panion & BF Biotech, Inc. (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
JT and Torii | Panion & BF Biotech, Incorporation | License Agreement
Collaborative Arrangement and Arrangement Other than Collaborative [Line Items]
Royalty payments	$ 3.5	$ 2.8	$ 6.6	$ 5.3

License, Collaboration and O_14

License, Collaboration and Other Significant Agreements - Sublicense Agreement with Japan Tobacco, Inc. and its subsidiary, Torii Pharmaceutical Co., Ltd. (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) performance_obligation	Jun. 30, 2021 USD ($)
License, Collaboration and Other Revenue:
Recognized revenue	$ 126,759	$ 52,913	$ 188,458	$ 105,217
JT and Torii | Sublicense Agreement
License, Collaboration and Other Revenue:
Number of performance obligations | performance_obligation			2
Recognized revenue	$ 1,500	$ 1,500	$ 2,600	$ 2,600

Restructuring - Narrative (Deta

Restructuring - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Apr. 04, 2022
Restructuring and Related Activities [Abstract]
Percentage for workforce approved for elimination, exclusive of open positions					42%
Percentage for workforce approved for elimination, inclusive of open positions					47%
Expected restructuring cost	$ 14,800		$ 14,800
Restructuring charges	14,531	$ 0	14,531	$ 0
Severance costs	11,200		11,200
Non-cash stock based compensation	3,300		3,300
Expected restructuring cost remaining	$ 300		$ 300

Restructuring - Restructuring R

Restructuring - Restructuring Reserve Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Restructuring Reserve [Roll Forward]
Balance at December 31, 2021			$ 0
Restructuring charges	$ 14,531	$ 0	14,531	$ 0
Stock-based compensation expense			(3,303)
Severance payments and adjustments			(4,313)
Balance at June 30, 2022	$ 6,915		$ 6,915

Liability Related to Sale of _3

Liability Related to Sale of Future Royalties - Additional Information (Details) - USD ($) $ in Thousands		6 Months Ended
	Feb. 25, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021
Other Liabilities Disclosure [Abstract]
Maximum annual royalty payout capacity	$ 13,000
Maximum aggregate royalty payout capacity	150,000
Proceeds from sale of future royalties, net	44,800	$ 0	$ 44,783
Liability related to sale of future royalties, net	$ 44,800	$ 56,743		$ 53,079
Annual effective interest rate		15.10%

Liability Related to Sale of _4

Liability Related to Sale of Future Royalties - Rollforward of Liability Related to Sale of Future Royalties (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Contractual Arrangement, Royalties Agreement, Liability, Noncurrent [Roll Forward]
Liability related to sale of future royalties, net beginning balance at December 31, 2021	$ 53,079
MTPC royalties payable	(764)
Non-cash interest expense recognized	4,428	$ 4,427
Liability related to sale of future royalties, net — ending balance	$ 56,743

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Assets Measured or Disclosed at Fair Value on Recurring Basis (Details) - USD ($)	Jun. 30, 2022	Dec. 31, 2021
Liabilities:
Derivative liability	$ 1,110,000	$ 1,820,000
Level 3
Assets:
Total assets fair value disclosure	0	0
Fair value measurements recurring
Assets:
Cash and cash equivalents	143,893,000	149,800,000
Total assets fair value disclosure	143,893,000	149,800,000
Liabilities:
Derivative liability	1,110,000	1,820,000
Total liabilities fair value disclosure	1,110,000	1,820,000
Fair value measurements recurring | Level 1
Assets:
Cash and cash equivalents	143,893,000	149,800,000
Total assets fair value disclosure	143,893,000	149,800,000
Liabilities:
Derivative liability	0	0
Total liabilities fair value disclosure	0	0
Fair value measurements recurring | Level 2
Assets:
Cash and cash equivalents	0	0
Total assets fair value disclosure	0	0
Liabilities:
Derivative liability	0	0
Total liabilities fair value disclosure	0	0
Fair value measurements recurring | Level 3
Assets:
Cash and cash equivalents	0	0
Total assets fair value disclosure	0	0
Liabilities:
Derivative liability	1,110,000	1,820,000
Total liabilities fair value disclosure	$ 1,110,000	$ 1,820,000

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Additional Information (Details)	Jun. 30, 2022 USD ($)	Dec. 31, 2021 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	$ 1,110,000	$ 1,820,000
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets measured at fair value on recurring basis	$ 0	0
Level 3 | Measurement Input, Clinical Development Success | Valuation, Market Approach
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability, measurement input	0
Level 3 | Other than Derivative Liabilities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Liabilities measured at fair value on recurring basis	$ 0	0
Collateral Agent, Pharmakon
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative liability	$ 1,100,000	$ 1,800,000

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Fair Value Derivative Liability (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2022	Jun. 30, 2021
Derivative Liability, Fair Value, Gross Liability [Roll Forward]
Balance at beginning of period	$ 1,110	$ 1,820	$ 1,820
Change in fair value of derivative liability, recorded as other expense (income)	0	(710)	(710)	$ (490)
Balance at end of period	$ 1,110	$ 1,110	$ 1,110

Inventory - Components of Inven

Inventory - Components of Inventory (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Raw materials	$ 757	$ 1,763
Work in process	38,466	62,635
Finished goods	18,843	14,661
Total inventory	58,066	79,059
Balance Sheet Classification:
Inventory	36,272	38,195
Other assets	$ 21,794	$ 40,864

Inventory - Additional Informat

Inventory - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Business Acquisition [Line Items]
Inventory amounts written down	$ 2,100		$ 400	$ 7,430	$ 5,425
Inventory adjustments to previous reserves	$ 5,800	$ 3,200		9,800
Keryx Biopharmaceuticals, Inc.
Business Acquisition [Line Items]
Inventory step-up charges				$ 0	$ 8,700

Intangible Assets and Goodwil_2

Intangible Assets and Goodwill - Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 213,603	$ 213,603
Accumulated Amortization	(123,497)	(105,476)
Total	90,106	108,127
Developed product rights for Auryxia
Finite-Lived Intangible Assets [Line Items]
Gross Carrying Value	213,603	213,603
Accumulated Amortization	(123,497)	(105,476)
Total	$ 90,106	$ 108,127
Finite-Lived Intangible Asset, Useful Life	6 years

Intangible Assets and Goodwil_3

Intangible Assets and Goodwill - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($) segment	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)
Finite-Lived Intangible Assets [Line Items]
Amortization expense	$ 9,000	$ 9,000	$ 18,021	$ 18,021
Goodwill	$ 55,053		$ 55,053		$ 55,053
Number of operating segments | segment			1
Developed product rights for Auryxia
Finite-Lived Intangible Assets [Line Items]
Intangible assets, estimated useful life			6 years

Accrued Expenses (Details)

Accrued Expenses (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Payables and Accruals [Abstract]
Product revenue allowances	$ 26,171	$ 26,624
Accrued clinical	7,622	14,036
Amounts due to collaboration partners	20,797	22,654
Accrued payroll and related	6,883	15,863
Lease liability	$ 4,422	$ 4,802
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Total accrued expenses	Total accrued expenses
Royalties	$ 3,457	$ 3,472
Professional fees	1,815	1,899
Accrued commercial manufacturing	3,420	3,843
Accrued restructuring	6,915	0
Accrued other	9,782	11,263
Total accrued expenses	$ 91,284	$ 104,456

Debt - Additional Information (

Debt - Additional Information (Details)				3 Months Ended		6 Months Ended
	Jul. 15, 2022 USD ($)	Dec. 10, 2020 USD ($)	Nov. 11, 2019 USD ($) tranche	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($)	Nov. 25, 2019 USD ($)
Line of Credit Facility [Line Items]
Term loan, net of facility fees, lender expenses and issuance costs				$ 98,158,000		$ 98,158,000
Derivative liability				1,110,000		1,110,000		$ 1,820,000
Collateral Agent, Pharmakon
Line of Credit Facility [Line Items]
Derivative liability				1,100,000		1,100,000		$ 1,800,000
Term Loan | Collateral Agent, Pharmakon | Tranche A and B | Subsequent Event
Line of Credit Facility [Line Items]
Payment for debt prepayment	$ 25,000,000
Payment for debt prepayment premium, including accrued and unpaid interest	500,000
Term Loan | Collateral Agent, Pharmakon | Tranche A | Subsequent Event
Line of Credit Facility [Line Items]
Payment for debt prepayment	5,000,000
Term Loan | Collateral Agent, Pharmakon | Tranche B | Subsequent Event
Line of Credit Facility [Line Items]
Payment for debt prepayment	$ 20,000,000
Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 100,000,000
Line of credit, maximum borrowing capacity, number of available tranches | tranche			2
Term loan, maturity term			5 years
Term loan, maturity term, potential reduction (up to)			1 year
Term loan, amortization period, potential reduction (up to)			1 year
Facility fee percentage on principal amount			2%
Facility fee paid, amount			$ 2,000,000
Prepayment premium percentage on principal if prepaid prior to third anniversary of funding			2%
Prepayment premium percentage on principal if prepaid prior to fourth anniversary and after third anniversary of funding			1%
Prepayment premium percentage on principal if prepaid after fourth anniversary of funding			0.50%
Interest expense				$ 2,700,000	$ 2,700,000	$ 5,400,000	$ 5,400,000
Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon | Debt Instrument, Quarterly Periodic Payment, Period One
Line of Credit Facility [Line Items]
Term loan, first quarterly principal payment due in			33 months
Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon | Debt Instrument, Quarterly Periodic Payment, Period Two
Line of Credit Facility [Line Items]
Term loan, first quarterly principal payment due in			48 months
Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon | Three-month LIBOR
Line of Credit Facility [Line Items]
Basis spread on floating interest rate			7.50%
Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, floor rate			2%
Debt instrument, cap rate			3.35%
Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon | Tranche A
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 80,000,000
Term loan, net of facility fees, lender expenses and issuance costs									$ 77,300,000
Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon | Tranche B
Line of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity			$ 20,000,000
BPCR Limited Partnership | Keryx | Term Loan | Collateral Agent, Pharmakon | Tranche B
Line of Credit Facility [Line Items]
Proceeds from line of credit		$ 20,000,000

Debt - Future Principal Payment

Debt - Future Principal Payments on the Term Loans (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Debt Disclosure [Abstract]
2022	$ 33,000
2023	32,000
2024	35,000
2025	0
2026	0
Thereafter	0
Total before unamortized discount and issuance costs	100,000
Less: unamortized discount and issuance costs	(1,842)
Total term loans	$ 98,158

Stockholders' Equity (Details)

Stockholders' Equity (Details) $ / shares in Units, $ in Thousands

3 Months Ended

6 Months Ended

10 Months Ended

Apr. 07, 2022 USD ($)

Mar. 01, 2022 USD ($)

Feb. 25, 2021 USD ($)

Mar. 12, 2020 USD ($)

Mar. 31, 2022 USD ($) shares

Jun. 30, 2021 shares

Mar. 31, 2021 USD ($) shares

Jun. 30, 2022 USD ($) stock_incentive_plan installment $ / shares shares

Jun. 30, 2021 USD ($) shares

Dec. 31, 2021 USD ($) $ / shares shares

Dec. 31, 2020 USD ($) shares

Jun. 04, 2020 shares

Feb. 28, 2014 shares

Class of Stock [Line Items]

Common stock, authorized (in shares)

350,000,000

350,000,000

175,000,000

Common stock, par value (in dollars per share) | $ / shares

$ 0.00001

$ 0.00001

Common stock, issued (in shares)

183,704,654

177,000,963

Common stock, outstanding (in shares)

183,704,654

177,000,963

Preferred stock, shares authorized (in shares)

25,000,000

25,000,000

Preferred stock, par value (in dollars per share) | $ / shares

$ 0.00001

$ 0.00001

Preferred stock, issued (in shares)

0

0

Preferred stock, outstanding (in shares)

0

0

Proceeds from the issuance of common stock, net of issuance costs | $

$ 7,102

$ 66,696

Number of stock incentive plans | stock_incentive_plan

1

Inducement Award Program

Class of Stock [Line Items]

Number of shares granted

297,000

Number of shares outstanding

174,000

Share-based Payment Arrangement, Option

Class of Stock [Line Items]

Expiration period

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%

Share-based Payment Arrangement, Option | Share Based Compensation Award Tranche One

Class of Stock [Line Items]

Vesting period

1 year

Vesting percentage

25%

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

Service-Based Restricted Stock Units | Share Based Compensation Award Tranche One

Class of Stock [Line Items]

Vesting period

1 year

Vesting percentage

50%

Service-Based Restricted Stock Units | Share Based Compensation Award Tranche Two

Class of Stock [Line Items]

Vesting period

6 months

Vesting percentage

25%

Award vesting grace period

1 year

Service-Based Restricted Stock Units | Share-based Compensation Award, Tranche, First Or Third Anniversary of Grant Date

Class of Stock [Line Items]

Vesting percentage

100%

Service-Based Restricted Stock Units | Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date, Subjected To Individual Continued Service

Class of Stock [Line Items]

Vesting period

1 year

Vesting percentage

33.33%

Service-Based Restricted Stock Units | Share-Based Payment Arrangement, Tranche Two, Second Anniversary After Grant Date, Subjected To Individual Continued Service

Class of Stock [Line Items]

Vesting period

2 years

Vesting percentage

33.33%

Service-Based Restricted Stock Units | Share-Based Payment Arrangement, Tranche Three, Third Anniversary After Grant Date, Subjected To Individual Continued Service

Class of Stock [Line Items]

Vesting period

3 years

Vesting percentage

33.33%

Service-Based Restricted Stock Units | Share-Based Payment Arrangement, Tranche One, First Anniversary After Grant Date

Class of Stock [Line Items]

Vesting period

1 year

Vesting percentage

33.33%

Service-Based Restricted Stock Units | Share-Based Payment Arrangement, Tranche Two, Following First Anniversary After Grant Date

Class of Stock [Line Items]

Vesting period

2 years

Award vesting grace period

1 year

Common Stock

Class of Stock [Line Items]

Common stock, outstanding (in shares)

183,386,035

169,651,423

158,520,089

183,704,654

169,651,423

177,000,963

148,074,085

Issuance of common stock, net of issuance costs (in shares)

4,404,600

10,446,160

9,228,017

Common Stock | At The Market Equity Offering Program Authorized February 2021

Class of Stock [Line Items]

Issuance of common stock, net of issuance costs (in shares)

21,128,065

Proceeds from the issuance of common stock, net of issuance costs | $

$ 72,400

Common Stock | At The Market Equity Offering Program Authorized March 2022

Class of Stock [Line Items]

Issuance of common stock, net of issuance costs (in shares)

404,600

Proceeds from the issuance of common stock, net of issuance costs | $

$ 800

Minimum | Share-based Payment Arrangement, Option

Class of Stock [Line Items]

Vesting period

12 months

Minimum | Service-Based Restricted Stock Units | Share-based Compensation Award, Tranche, First Or Third Anniversary of Grant Date

Class of Stock [Line Items]

Vesting period

1 year

Maximum | At The Market Equity Offering Program Authorized February 2021

Class of Stock [Line Items]

Common stock sales agreement amount | $

$ 100,000

Maximum | At The Market Equity Offering Program Authorized March 2022

Class of Stock [Line Items]

Common stock sales agreement amount | $

$ 25,300

Maximum | Open Market Sale Agreement, Authorized April 2022

Class of Stock [Line Items]

Common stock sales agreement amount | $

$ 26,000

Maximum | Share-based Payment Arrangement, Option

Class of Stock [Line Items]

Vesting period

48 months

Maximum | Service-Based Restricted Stock Units | Share-based Compensation Award, Tranche, First Or Third Anniversary of Grant Date

Class of Stock [Line Items]

Vesting period

3 years

At The Market Equity Offering Program | Common Stock

Class of Stock [Line Items]

Issuance of common stock, net of issuance costs (in shares)

5,224,278

3,509,381

Proceeds from the issuance of common stock, net of issuance costs | $

$ 15,900

$ 10,600

At The Market Equity Offering Program | Maximum

Class of Stock [Line Items]

Common stock sales agreement amount | $

$ 65,000

2014 Plans

Class of Stock [Line Items]

Common stock, reserved for future issuance (in shares)

1,785,000

Incremental rate at which the shares reserved for issuance increase

3%

2014 Plans | Share-based Payment Arrangement, Option | Employees

Class of Stock [Line Items]

Number of shares granted

3,233,500

2014 Plans | Share-based Payment Arrangement, Option | Director

Class of Stock [Line Items]

Number of shares granted

140,700

2014 Plans | Performance Shares

Class of Stock [Line Items]

Number of shares granted

400,000

2014 Plans | Service-Based Restricted Stock Units | Employees

Class of Stock [Line Items]

Number of shares granted (in shares)

5,212,308

2014 Plans | Service-Based Restricted Stock Units | Director

Class of Stock [Line Items]

Number of shares granted (in shares)

95,900

2014 Plans | Performance-Based Restricted Stock Units

Class of Stock [Line Items]

Number of shares granted (in shares)

400,000

2014 Employee Stock Purchase Plan

Class of Stock [Line Items]

Common stock, reserved for future issuance (in shares)

4,981,995

Offering period

6 months

Purchase price at the end of offering period

85%

Number of shares issued

191,146

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)

1 Months Ended

3 Months Ended

6 Months Ended

Feb. 10, 2021

Sep. 04, 2020

Apr. 02, 2020

Apr. 09, 2019

Jan. 01, 2017 USD ($)

Feb. 28, 2022 USD ($)

Dec. 31, 2021 USD ($)

Dec. 31, 2020

Feb. 28, 2019 USD ($)

Jul. 31, 2016 USD ($) ft²

Jun. 30, 2022 USD ($) ft² extensionOption

Mar. 31, 2022 USD ($)

Jun. 30, 2021 USD ($)

Jun. 30, 2022 USD ($) ft² extensionOption

Jun. 30, 2021 USD ($)

Nov. 30, 2020 ft²

Apr. 30, 2018 ft²

Commitments And Contingencies [Line Items]

Operating lease, cost

$ 1,800,000

$ 1,700,000

$ 3,600,000

$ 3,300,000

Operating lease, payments

1,800,000

1,800,000

3,700,000

3,500,000

Increase (decrease) in purchase commitments

$ (800,000)

(773,000)

21,338,000

Inventory adjustments to previous reserves

5,800,000

$ 3,200,000

9,800,000

Total remaining contract costs

4,600,000

4,600,000

Contract cost incurred in research and development activities

175,700,000

Supply Agreement, Patheon Inc.

Commitments And Contingencies [Line Items]

Minimum purchase commitment

3,300,000

3,300,000

BioVectra Inc

Commitments And Contingencies [Line Items]

Long-term minimum purchase commitment renewal term

1 year

Cost of purchased minimum quantity product

82,400,000

82,400,000

Siegfried Evionnaz SA

Commitments And Contingencies [Line Items]

Cost of purchased minimum quantity product

$ 10,500,000

$ 10,500,000

Purchase commitment, option to extend, prior notice period

12 months

Esteve Química, S.A

Commitments And Contingencies [Line Items]

Initial term of supply agreement

4 years

Long-term minimum purchase commitment

$ 32,400,000

STA Pharmaceutical Hong Kong Limited

Commitments And Contingencies [Line Items]

Long-term minimum purchase commitment

$ 62,000,000

Minimum purchase commitment, initial term

4 years

WuXi STA

Commitments And Contingencies [Line Items]

Purchase commitment, option to extend, prior notice period

18 months

Minimum purchase commitment, initial term

4 years

Long-term purchase commitment, fixed price, period

12 months

Long-term purchase commitment, option to terminate, prior notice period (at least)

180 days

Minimum

Commitments And Contingencies [Line Items]

Operating lease, incremental borrowing rates based on remaining lease term

6.65%

6.65%

Operating lease, remaining lease term

4 years 2 months 12 days

4 years 2 months 12 days

Maximum

Commitments And Contingencies [Line Items]

Operating lease, incremental borrowing rates based on remaining lease term

7.25%

7.25%

Operating lease, remaining lease term

9 years 1 month 2 days

9 years 1 month 2 days

Keryx Biopharmaceuticals, Inc.

Commitments And Contingencies [Line Items]

Preliminary fair value of the off-market element

$ 76,700,000

$ 66,900,000

$ 66,900,000

Cambridge

Commitments And Contingencies [Line Items]

Area of property leased (in square feet) | ft²

45,362

65,167

Annual lease expense

$ 242,000

Monthly lease expense

$ 22,000

Cambridge | Letter of Credit | Other Assets

Commitments And Contingencies [Line Items]

Total security deposit in connection with lease

$ 1,600,000

$ 1,600,000

Cambridge | Office Space

Commitments And Contingencies [Line Items]

Area of property leased (in square feet) | ft²

19,805

Monthly lease expense

$ 48,000

$ 135,000

Operating lease, free monthly rent, period

2 months

Lease period, number of extension options | extensionOption

1

1

Lease extension period

5 years

5 years

Boston | Keryx Biopharmaceuticals, Inc. | Letter of Credit | Other Assets

Commitments And Contingencies [Line Items]

Total security deposit in connection with lease

$ 1,400,000

$ 1,400,000

Boston | Office Space

Commitments And Contingencies [Line Items]

Area of property leased (in square feet) | ft²

27,300

27,300

Monthly lease expense

$ 200,122

$ 136,000

Operating lease, free monthly rent, period

5 months

Operating lease, annual rent escalation, percentage

2%

Operating lease, allowance for leasehold improvements

$ 1,954,680

Boston | Office Space | Keryx Biopharmaceuticals, Inc.

Commitments And Contingencies [Line Items]

Lease period, number of extension options | extensionOption

1

1

Lease extension period

5 years

5 years

Sublease rental income

$ 400,000

$ 400,000

$ 900,000

$ 900,000

Commitments and Contingencies_2

Commitments and Contingencies - Undiscounted Minimum Rental Commitments Under Non-Cancelable Leases (Details) $ in Thousands	Jun. 30, 2022 USD ($)
Operating Leases
Remaining 2022	$ 3,671
2023	6,954
2024	8,167
2025	8,293
2026	6,571
Thereafter	12,200
Total	45,856
Lease Payments to be Received from Sublease
Remaining 2022	915
2023	307
2024	0
2025	0
2026	0
Thereafter	0
Total	1,222
Net Operating Lease Payments
Remaining 2022	2,756
2023	6,647
2024	8,167
2025	8,293
2026	6,571
Thereafter	12,200
Total	$ 44,634

Commitments and Contingencies_3

Commitments and Contingencies - Difference Between Undiscounted Minimum Rental Commitments Under Non-Cancelable Leases and Operating Leases Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Commitments and Contingencies Disclosure [Abstract]
Total	$ 45,856
Present value adjustment using incremental borrowing rate	(9,359)
Operating lease liabilities	$ 36,497
Operating Lease, Liability, Current, Statement of Financial Position [Extensible Enumeration]	Accrued expenses and other current liabilities	Accrued expenses and other current liabilities

Net Loss per Share - Anti-Dilut

Net Loss per Share - Anti-Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share (Details) - shares	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
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)	13,502,015	17,616,760	20,279,566	17,616,760
Warrant
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)	0	509,611	0	509,611
Share-based Payment Arrangement, Option
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)	13,502,015	11,532,673	13,508,217	11,532,673
Unvested restricted stock units
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)	0	5,574,476	6,771,349	5,574,476