Akebia Therapeutics (AKBA) 10-Q 12 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Trading Symbol	AKBA
Title of 12(b) Security	Common Stock, par value $0.00001 per share
Security Exchange Name	NASDAQ
Entity Registrant Name	Akebia Therapeutics, Inc.
Entity Central Index Key	0001517022
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		118,943,016
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Document Quarterly Report	true
Document Transition Report	false
Entity Incorporation, State or Country Code	DE
Entity Address, Address Line One	245 First Street
Entity Address, City or Town	Cambridge
Entity Address, State or Province	MA
City Area Code	617
Local Phone Number	871-2098
Entity Address, Postal Zip Code	02142
Entity Tax Identification Number	20-8756903
Entity File Number	001-36352

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 122,886,000	$ 104,644,000
Available for sale securities	22,727,000	216,996,000
Inventory	115,987,000	114,245,000
Accounts receivable, net	29,654,000	16,666,000
Prepaid expenses and other current assets	7,754,000	15,724,000
Total current assets	299,008,000	468,275,000
Property and equipment, net	12,799,000	8,023,000
Operating lease assets	30,141,000
Goodwill	55,053,000	55,053,000
Other intangible assets, net	300,312,000	328,153,000
Other assets	97,907,000	137,036,000
Total assets	795,220,000	996,540,000
Current liabilities:
Accounts payable	64,362,000	42,796,000
Accrued expenses and other current liabilities	126,644,000	150,917,000
Debt		15,000,000
Short-term deferred revenue	32,142,000	56,980,000
Total current liabilities	223,148,000	265,693,000
Deferred rent, net of current portion		3,006,000
Deferred revenue, net of current portion	43,887,000	55,709,000
Operating lease liabilities, net of current portion	28,811,000
Deferred tax liabilities	1,752,000	6,631,000
Other non-current liabilities	30,060,000	29,573,000
Total liabilities	327,658,000	360,612,000
Commitments and contingencies (Note 15)
Stockholders' equity:
Preferred stock $0.00001 par value, 25,000,000 shares authorized; 0 shares issued and outstanding at September 30, 2019 and December 31, 2018
Common stock $0.00001 par value; 175,000,000 shares authorized at September 30, 2019 and December 31, 2018; 118,863,735 and 116,887,518 shares issued and outstanding at September 30, 2019 and December 31, 2018, respectively	1,000	1,000
Additional paid-in capital	1,167,126,000	1,150,583,000
Accumulated other comprehensive income (loss)	6,000	(261,000)
Accumulated deficit	(699,571,000)	(514,395,000)
Total stockholders' equity	467,562,000	635,928,000
Total liabilities and stockholders' equity	$ 795,220,000	$ 996,540,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2019	Dec. 31, 2018
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.00001	$ 0.00001
Preferred stock, shares authorized	25,000,000	25,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.00001	$ 0.00001
Common stock, shares authorized	175,000,000	175,000,000
Common stock, shares issued	118,863,735	116,887,518
Common stock, shares outstanding	118,863,735	116,887,518

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenues:
Total revenues	$ 91,977	$ 53,169	$ 265,446	$ 147,892
Cost of goods sold:
Product	$ 29,162		$ 79,888
Type of Cost, Good or Service [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Amortization of intangibles	$ 9,101		$ 27,301
Total cost of goods sold	38,263		107,189
Operating expenses:
Research and development	74,512	$ 70,634	242,557	$ 203,955
Selling, general and administrative	34,178	10,378	104,537	31,940
License expense	929		2,560
Total operating expenses	109,619	81,012	349,654	235,895
Operating loss	(55,905)	(27,843)	(191,397)	(88,003)
Other income:
Interest income	228	1,780	1,582	4,417
Other income (expense)	(185)	16	(240)	52
Net loss before income taxes	(55,862)	(26,047)	(190,055)	(83,534)
Benefit from income taxes	(1,277)		(4,879)
Net loss	$ (54,585)	$ (26,047)	$ (185,176)	$ (83,534)
Net loss per share - basic and diluted	$ (0.46)	$ (0.46)	$ (1.57)	$ (1.54)
Weighted-average number of common shares - basic and diluted	118,863,063	57,027,598	118,071,674	54,207,973
Comprehensive loss:
Net loss	$ (54,585)	$ (26,047)	$ (185,176)	$ (83,534)
Other comprehensive gain (loss) - unrealized gain (loss) on debt securities	(17)	50	267	33
Total comprehensive loss	(54,602)	(25,997)	(184,909)	(83,501)
Product Revenue, Net
Revenues:
Total revenues	30,004		82,204
License, Collaboration and Other Revenue
Revenues:
Total revenues	$ 61,973	$ 53,169	$ 183,242	$ 147,892

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
Balance at Dec. 31, 2017	$ 122,574		$ 493,823	$ (442)	$ (370,807)
Balance, shares at Dec. 31, 2017		47,612,619
Issuance of common stock, net of issuance costs	95,416		95,416
Issuance of common stock, net of issuance costs, shares		9,194,306
Proceeds from sale of stock under employee stock purchase plan	218		218
Proceeds from sale of stock under employee stock purchase plan, shares		17,569
Exercise of options	182		182
Exercise of options, shares		21,363
Share-based compensation expense	2,232		2,232
Restricted stock unit vesting, shares		11,613
Unrealized gain/loss	(108)			(108)
Net income (loss)	(23,418)				(23,418)
Balance at Mar. 31, 2018	197,096		591,871	(550)	(394,225)
Balance, shares at Mar. 31, 2018		56,857,470
Balance at Dec. 31, 2017	122,574		493,823	(442)	(370,807)
Balance, shares at Dec. 31, 2017		47,612,619
Net income (loss)	(83,534)
Balance at Sep. 30, 2018	142,540		597,290	(409)	(454,341)
Balance, shares at Sep. 30, 2018		57,046,563
Balance at Mar. 31, 2018	197,096		591,871	(550)	(394,225)
Balance, shares at Mar. 31, 2018		56,857,470
Proceeds from sale of stock under employee stock purchase plan	(3)		(3)
Exercise of options	314		314
Exercise of options, shares		43,041
Share-based compensation expense	2,494		2,494
Restricted stock unit vesting, shares		13,375
Unrealized gain/loss	91			91
Net income (loss)	(34,069)				(34,069)
Balance at Jun. 30, 2018	165,923		594,676	(459)	(428,294)
Balance, shares at Jun. 30, 2018		56,913,886
Issuance of common stock, net of issuance costs	36		36
Proceeds from sale of stock under employee stock purchase plan	267		267
Proceeds from sale of stock under employee stock purchase plan, shares		31,199
Exercise of options	59		59
Exercise of options, shares		101,478
Share-based compensation expense	2,252		2,252
Unrealized gain/loss	50			50
Net income (loss)	(26,047)				(26,047)
Balance at Sep. 30, 2018	142,540		597,290	(409)	(454,341)
Balance, shares at Sep. 30, 2018		57,046,563
Balance at Dec. 31, 2018	$ 635,928	$ 1	1,150,583	(261)	(514,395)
Balance, shares at Dec. 31, 2018	116,887,518	116,887,518
Proceeds from sale of stock under employee stock purchase plan	$ 188		188
Proceeds from sale of stock under employee stock purchase plan, shares		39,977
Exercise of options	365		365
Exercise of options, shares		62,204
Share-based compensation expense	2,094		2,094
Restricted stock unit vesting, shares		132,563
Unrealized gain/loss	225			225
Net income (loss)	(72,421)				(72,421)
Balance at Mar. 31, 2019	566,379	$ 1	1,153,230	(36)	(586,816)
Balance, shares at Mar. 31, 2019		117,122,262
Balance at Dec. 31, 2018	$ 635,928	$ 1	1,150,583	(261)	(514,395)
Balance, shares at Dec. 31, 2018	116,887,518	116,887,518
Net income (loss)	$ (185,176)
Balance at Sep. 30, 2019	$ 467,562	$ 1	1,167,126	6	(699,571)
Balance, shares at Sep. 30, 2019	118,863,735	118,863,735
Balance at Mar. 31, 2019	$ 566,379	$ 1	1,153,230	(36)	(586,816)
Balance, shares at Mar. 31, 2019		117,122,262
Issuance of common stock, net of issuance costs	9,035		9,035
Issuance of common stock, net of issuance costs, shares		1,384,520
Exercise of options	195		195
Exercise of options, shares		300,592
Retired shares	(426)		(426)
Retired shares, shares		(55,324)
Share-based compensation expense	2,284		2,284
Restricted stock unit vesting, shares		35,251
Unrealized gain/loss	59			59
Net income (loss)	(58,170)				(58,170)
Balance at Jun. 30, 2019	519,356	$ 1	1,164,318	23	(644,986)
Balance, shares at Jun. 30, 2019		118,787,301
Proceeds from sale of stock under employee stock purchase plan	195		195
Proceeds from sale of stock under employee stock purchase plan, shares		47,553
Share-based compensation expense	2,613		2,613
Restricted stock unit vesting, shares		28,881
Unrealized gain/loss	(17)			(17)
Net income (loss)	(54,585)				(54,585)
Balance at Sep. 30, 2019	$ 467,562	$ 1	$ 1,167,126	$ 6	$ (699,571)
Balance, shares at Sep. 30, 2019	118,863,735	118,863,735

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Operating activities:
Net loss	$ (185,176)	$ (83,534)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,659	638
Amortization of intangibles	27,301
Amortization of premium/discount on investments	(795)	(698)
Non-cash interest expense	508
Non-cash operating lease expense	(1,673)
Fair value write-up of inventory sold	51,604
Write-down of inventory to net realizable value	5,968	0
Stock-based compensation	6,991	6,978
Deferred income taxes	(4,879)
Changes in operating assets and liabilities:
Accounts receivable	(12,988)	33,528
Inventory	(28,565)
Prepaid expenses and other current assets	9,415	(346)
Other long-term assets	3,145	67
Accounts payable	26,438	5,686
Accrued expense	(29,176)	42,118
Operating lease liabilities	1,577
Deferred revenue	(36,660)	(28,101)
Deferred rent		(131)
Net cash used in operating activities	(165,306)	(23,795)
Investing activities:
Purchase of equipment	(6,435)	(776)
Proceeds from the maturities of available for sale securities	130,610	180,091
Proceeds from sales of available for sale securities	64,721	13,000
Purchase of available for sale securities		(172,438)
Net cash provided by investing activities	188,896	19,877
Financing activities:
Proceeds from the issuance of common stock, net of issuance costs	9,035	95,453
Proceeds from the sale of stock under employee stock purchase plan	383	482
Proceeds from the exercise of stock options	560	555
Retirement of treasury stock	(426)
Payments on debt	(15,000)
Payments on capital lease obligations		(13)
Net cash provided by (used in) financing activities	(5,448)	96,477
Increase in cash, cash equivalents, and restricted cash	18,142	92,559
Cash, cash equivalents, and restricted cash at beginning of the period	107,099	71,437
Cash, cash equivalents, and restricted cash at end of the period	$ 125,241	$ 163,996

Nature of Organization and Oper

Nature of Organization and Operations	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Nature of Organization and Operations	1. 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 focused on the development and commercialization of therapeutics for people with kidney disease. Akebia’s commercial product, Auryxia ® ® ® The Company’s lead investigational product candidate, vadadustat, is an oral therapy in Phase 3 development for two indications: anemia due to CKD in adult patients with DD-CKD and anemia due to CKD in adult patients with NDD-CKD. The Company believes vadadustat has the potential to set a new standard of care in the treatment of anemia due to CKD, acting via a novel hypoxia-inducible factor, or HIF, pathway. HIF is the primary regulator of the production of red blood cells, or RBCs, in the body, as well as other important metabolic functions. On November 11, 2019, the Company entered into a loan agreement, or the Loan Agreement, with Keryx as guarantor, Biopharma Credit plc as collateral agent and lender, or the Collateral Agent, and Biopharma Credit Investments V (Master) LP as lender, or collectively with the Collateral Agent, Pharmakon, pursuant to which term loans in an aggregate principal amount of $100.0 million are available to the Company in two tranches, subject to certain terms and conditions, or the Term Loan. Subject to the satisfaction of certain conditions, the first tranche of $80.0 million, or Tranche A, will be drawn in a single drawing on November 25, 2019, or the Tranche A Funding Date. The second tranche under the Term Loan allows the Company to borrow an additional $20.0 million until December 31, 2020, or Tranche B. Refer to Note 11 to our condensed consolidated financial statements in Part I, Item 1 – Financial Statements (unaudited) for additional details on the Loan Agreement. On December 12, 2018, the Company completed a merger with Keryx Biopharmaceuticals, Inc., or Keryx, or the Merger. Pursuant to the terms and conditions of the Agreement and Plan of Merger, or the Merger Agreement, each share of Keryx common stock, or Keryx Share, issued and outstanding immediately prior to the effective time of the Merger, or the Effective Time, was cancelled and converted into 0.37433, or the Exchange Multiplier, fully paid and non-assessable shares of Akebia common stock, or Akebia Shares, resulting in the issuance of an aggregate of 59,270,410 Akebia Shares. Since inception, the Company has devoted most of its resources to research and development, including its preclinical and clinical development activities, raising capital, 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 to the Company’s Japanese partners Japan Tobacco, Inc. and its subsidiary Torii Pharmaceutical Co., Ltd., collectively, JT and Torii, The Company expects its cash resources, including funds to be received from its collaborators and $100.0 million upon closing of the Term Loans with Pharmakon, subject to the satisfaction of certain customary conditions, to fund the Company’s current operating plan beyond the next twelve months, into the first quarter of 2021. However, on a quarterly basis, the Company is required to conduct an accounting analysis under ASC 205-40, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern The Company will require additional capital for the further commercialization of Auryxia and continued development and potential commercialization of the Company’s existing product candidates and would need to raise additional funds to pursue development activities related to any additional product candidates. If and until the Company can generate a sufficient amount of product revenue, the Company expects to finance future cash needs through public or private equity or debt transactions, payments from its collaborators, royalty transactions, strategic transactions, or a combination of these approaches. However, adequate additional financing may not be available to the Company on acceptable terms, or at all. If the Company is unable to raise capital when needed or on attractive terms, it may be forced to delay, reduce or eliminate its research and development programs or any commercialization efforts.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. 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 U.S. GAAP for complete financial statements. Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification, or 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 nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2019 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, 2018 filed with the U.S. Securities and Exchange Commission on March 26, 2019, or the 2018 Annual Report on Form 10-K. The significant accounting policies used in preparation of these unaudited condensed consolidated financial statements for the three and nine months ended September 30, 2019 are consistent with those discussed in Note 2 to the consolidated financial statements in the Company’s 2018 Annual Report on Form 10-K and are updated below as necessary. New Accounting Pronouncements – Recently Adopted In February 2016, the FASB issued ASU 2016-02, Leases • The Company elected the package of transition practical expedients, which allows it to retain the lease classification and initial direct costs for any leases that existed prior to the adoption of this new standard. • The Company will not reassess whether any contracts completed prior to the adoption are leases. The Company adopted ASC 842 using the modified retrospective approach, as of January 1, 2019, with no restatements of prior periods or a cumulative effect of the adoption of ASC 842 in retained earnings. On January 1, 2019, the Company recognized additional operating lease liabilities, net of deferred rent, of approximately $37.1 million based on the present value of the remaining minimum lease payments, a corresponding right of use assets of approximately $33.4 million, and $0.9 million to prepaid expenses and other current assets related to leasehold improvement allowances that had yet to be incurred as of the date of adoption, but for which the Company was reasonably certain to incur costs at least equal to the maximum level of leasehold improvement allowance. The adoption of ASC 842 did not have an impact on the Company’s unaudited condensed consolidated statement of operations. Prior periods are presented in accordance with ASC 840, Leases The Company made an accounting policy election not to recognize leases with an initial term of 12 months or less within its unaudited condensed consolidated balance sheets and to recognize those lease payments on a straight-line bases in its unaudited condensed consolidated statements of operations. The Company also made the accounting policy election not to separate the non-lease components from the lease components for its building leases and, rather, account for each non-lease component and lease component as a single component. The Company determines if an arrangement is a lease at inception. An arrangement is determined to contain a lease if the contract conveys the right to control the use of an identified property, plant, or equipment for a period of time in exchange for consideration. If the Company can benefit from the various underlying assets of a lease on their own or together with other resources that are readily available, or if the various underlying assets are neither highly dependent on nor highly interrelated with other underlying assets in the arrangement, they are considered to be a separate lease component. In the event multiple underlying assets are identified, the lease consideration is allocated to the various components based on each of the component’s relative fair value. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent its obligation to make lease payments arising from the leasing arrangement. Operating lease assets and operating lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. The Company uses the implicit rate when readily determinable and uses an estimate of its incremental borrowing rate when the implicit rate is not readily determinable based upon the available information at the commencement date of lease inception. The incremental borrowing rate is determined using a credit rating scoring model to estimate the Company’s credit rating, adjusted for collateralization. The calculation of the operating lease assets includes any lease payments made and excludes any lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company’s operating leases are reflected in prepaid expenses and other current assets, operating lease assets, accrued expenses and operating lease liabilities, net of current portion in its condensed consolidated balance sheets. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment , which simplifies how companies calculate goodwill impairments by eliminating Step 2 of the impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. ASU 2017-04 requires companies to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to the related reporting unit. This ASU is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal year 2020. Early adoption is allowed, and the Company adopted ASU 2017-04 in the first quarter of fiscal year 2019. The Company will conduct its initial goodwill impairment test as of October 1, 2019 and annually thereafter, or more frequently if indicators of impairment are present or changes in circumstances suggest that an impairment may exist. Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. Currently, U.S. GAAP delays recognition of the full amount of credit losses until the loss is probable of occurring. Under this ASU, the income statement will reflect an entity’s current estimate of all expected credit losses. The measurement of expected credit losses will be based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down of the security. Additionally, credit losses for trade receivables will be also be recorded through an allowance that reflects the Company’s current estimate of credit losses expected to be incurred. This ASU is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal year 2020. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-13 on its consolidated financial position and results of operations. Based on the composition of the Company’s available-for-sale debt securities, trade receivables, and other financial assets, and also taking into account current market conditions and historical credit loss activity, the Company does not expect that the adoption of this standard will have a material impact on the Company’s consolidated financial statements and related disclosures. In 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement This ASU is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal year 2020. The Company is currently evaluating the impact the adoption of the standard will have on its condensed consolidated financial statements and related disclosures. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and 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, other non-current liabilities, stock-based compensation expense, product and collaboration revenues including various rebates and reserves related to product sales, inventories, income taxes, intangible assets and goodwill. Cash, Cash Equivalents, and Restricted Cash Cash and cash equivalents consist of all cash on hand, deposits and funds invested in available-for-sale securities with original maturities of three months or less at the time of purchase. At September 30, 2019, the Company’s cash is primarily in money market funds. The Company may maintain balances with its banks in excess of federally insured limits. Restricted cash represents amounts required for security deposits under the Company’s office and lab space lease agreements and cash balances held as collateral for the Company’s employee credit card program. Restricted cash is included in “prepaid expenses and other current assets” and “other assets” in the unaudited condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported in the unaudited condensed consolidated balance sheet that sum to the total of the amounts reported in the unaudited condensed consolidated statement of cash flows (in thousands): September 30, 2019 September 30, 2018 Cash and cash equivalents $ 122,886 $ 162,430 Prepaid expenses and other current assets 263 — Other assets 2,092 1,566 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows $ 125,241 $ 163,996 Investments Management determines the appropriate classification of securities at the time of purchase and reevaluates such designation as of each balance sheet date of Property and Equipment Property and equipment is stated at cost, less accumulated depreciation. Assets under capital lease are included in property and equipment. Property and equipment is depreciated using the straight-line method over the estimated useful lives of the assets, generally three to seven years. Such costs are periodically reviewed for recoverability when impairment indicators are present. Such indicators include, among other factors, operating losses, unused capacity, market value declines and technological obsolescence. Recorded values of asset groups of equipment that are not expected to be recovered through undiscounted future net cash flows are written down to current fair value, which generally is determined from estimated discounted future net cash flows (assets held for use) or net realizable value (assets held for sale). The following is the summary of property and equipment and related accumulated depreciation as of September 30, 2019 and December 31, 2018. Useful Life September 30, 2019 December 31, 2018 (in thousands) Computer equipment and software 3 $ 1,010 $ 1,593 Furniture and fixtures 5 - 7 2,086 1,170 Equipment 7 2,451 1,780 Leasehold improvements Shorter of the useful life or remaining lease term (10 years) 10,869 5,324 Office equipment under capital lease 3 — 114 16,416 9,981 Less accumulated depreciation (3,617 ) (1,958 ) Net property and equipment $ 12,799 $ 8,023 Depreciation expense was approximately $0.6 million and $0.2 million for the three months ended September 30, 2019 and 2018, respectively, and approximately $1.7 million and $0.6 million for the nine months ended September 30, 2019 and 2018, respectively. Inventory The Company values its inventories at the lower-of-cost or net realizable value. The Company determines the cost of its inventories, which includes amounts related to materials and manufacturing overhead, on a first-in, first-out basis. The Company classifies its inventory costs as long-term, in other assets in its unaudited condensed consolidated balance sheets, when it expects to utilize the inventory beyond their normal operating cycle. Prior to the regulatory approval of its product candidates, the Company incurs expenses for the manufacture of material that could potentially be available to support the commercial launch of its products. Until the first reporting period when regulatory approval has been received or is otherwise considered probable and the future economic benefit is expected to be realized, the Company records all such costs as research and development expense. Inventory used in clinical trials is also expensed as research and development expense, when selected for such use. Inventory that can be used in either the production of clinical or commercial products is expensed as research and development costs when identified for use in a clinical manufacturing campaign. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and writes down any excess and obsolete inventory to its net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of product sales in the unaudited condensed consolidated statements of operations and comprehensive loss. The determination of whether inventory costs will be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required. Additionally, the Company’s product is subject to strict quality control and monitoring throughout the manufacturing process. In the event that certain batches or units of product no longer meet quality specifications, the Company will record a charge to cost of product sales to write-down any unmarketable inventory to its estimated net realizable value. In all cases, product inventory is carried at the lower of cost or its estimated net realizable value. Revenue Recognition The Company generates revenues primarily from sales of Auryxia, see Note 3, and from its collaborations with MTPC and Otsuka, see Note 4. The Company recognizes revenue in accordance with ASC 606, which applies to all contracts with customers, except for contracts that are within the scope of other standards. Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, it performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product Revenue, Net The Company sells Auryxia in the U.S. primarily to wholesale distributors as well as certain specialty pharmacy providers, collectively, Customers. These Customers resell the Company’s product to health care providers and patients. In addition to distribution agreements with Customers, the Company enters into arrangements with health care providers and payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks, and discounts with respect to the purchase of the Company’s product. The Company recognizes revenue on product sales when the Customer obtains control of the Company’s product, which occurs at a point in time, typically upon delivery to the Customer. The Company expenses incremental costs of obtaining a contract as and when incurred if the expected amortization period of the asset that it would have recognized is one year or less. Reserves for Variable Consideration Revenue from product sales is recorded at the net sales price (transaction price), which includes estimates of variable consideration for which reserves are established and which result from discounts, returns, chargebacks, rebates, co-pay assistance and other allowances that are offered within contracts between the Company and its Customers, health care providers, payors and other indirect customers relating to the Company’s sales of its products. These reserves are based on the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amount will be credited to the Customer) or as a current liability (if the amount is payable to a Customer or a party other than a Customer). When appropriate, t The amount of variable consideration that is included in the transaction price may be constrained, and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Trade Discounts and Allowances: The Company generally provides Customers with discounts that include incentive fees that are explicitly stated in the Company’s contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. In addition, the Company compensates (through trade discounts and allowances) its Customers for sales order management, data, and distribution services. However, the Company has determined such services received to date are not distinct from the Company’s sale of products to the Customer and, therefore, these payments have been recorded as a reduction of revenue within the unaudited condensed consolidated statement of operations and comprehensive loss through September 30, 2019. The Company records a corresponding reduction of accounts receivable (if the trade discount and/or allowance will be credited to the Customer) or an increase in accrued expense (if the trade discount and/or allowance is payable to a Customer) on the consolidated balance sheets. Product Returns: Consistent with industry practice, the Company generally offers Customers a limited right of return which allows for the product to be returned when the product expiry is within an allowable window. This right of return lapses once the product is provided to a patient. The Company estimates the amount of its product sales that may be returned by its Customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized. The Company currently estimates product return reserve using available industry data and its own historical sales information, including its visibility into the inventory remaining in the distribution channel. Provider Chargebacks and Discounts : Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These reserves are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider by Customers, and the Company generally issues credits for such amounts within a few weeks of the Customer’s resale of the product. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel at each reporting period end that the Company expects will be sold to qualified healthcare providers, and chargebacks that Customers have claimed but for which the Company has not yet issued a credit. Commercial and Medicare Part D Rebates: The Company contracts with various commercial payor organizations, primarily health insurance companies and pharmacy benefit managers, for the payment of rebates with respect to utilization of its products. The Company estimates the rebates for commercial and Medicare Part D payors based upon (i) its contracts with the payors and (ii) information obtained from its Customers and other third parties regarding the payor mix for Auryxia. The Company estimates these rebates and records such estimates in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Other Government Rebates: The Company is subject to discount obligations under state Medicaid programs and other government programs. The Company estimates its Medicaid and other government programs rebates based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses and other current liabilities on the consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but which remains in the distribution channel at the end of each reporting period. Other Incentives: Other incentives that the Company offers include voluntary patient assistance programs such as the Company’s co-pay assistance program, which are intended to provide financial assistance to qualified commercially insured patients with prescription drug co-payments required by payors. The calculation of the accrual for co-pay assistance is based on actual claims processed during a given period, as well as historical utilization data to estimate the amount the Company expects to receive associated with product that has been recognized as revenue, but remains in in the distribution channel at the end of each reporting period. Collaboration Revenues The Company enters into out-license and collaboration agreements which are within the scope of ASC 606, under which it licenses certain rights to its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory, and commercial milestone payments; payments for manufacturing supply services the Company provides through its contract manufacturers; and royalties on net sales of licensed products. Each of these payments may result in license, collaboration and other revenue, except for revenues from royalties on net sales of licensed products, which are classified as royalty revenues. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, the Company implements the five-step model noted above. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine whether the individual promises should be accounted for as separate performance obligations or as a combined performance obligation, and to determine the stand-alone selling price for each performance obligation identified in the contract. A deliverable represents a separate performance obligation if both of the following criteria are met: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer, and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. With regard to the MTPC and Otsuka Agreements (each as defined in Note 4), the Company recognizes revenue related to amounts allocated to the identified performance obligation on a proportional performance basis as the underlying services are performed. Licenses of Intellectual Property If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. Milestone Payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to assess the milestone as probable of being achieved. There is considerable judgment involved in determining whether a milestone is probable of being reached at each specific reporting period. Milestone payments that are not within the control of the Company or the customer, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenues as, or when, the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenue in the period of adjustment. Manufacturing Supply Services Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the licensee exercises these options, any additional payments are recorded in license, collaboration and other revenues when the licensee obtains control of the goods, which is upon delivery. Royalties The Company will recognize sales-based royalties, including milestone payments based on the level of sales, at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). The Company receives royalty payments from JT and Torii, based on net sales of Riona in Japan. Collaborative Arrangements The Company records the elements of its collaboration agreements that represent joint operating activities in accordance with ASC Topic 808, Collaborative Arrangements Revenue from Contracts with Customers – Scope and Scope Exceptions During the three months ended September 30, 2019 and 2018, the Company incurred approximately $0.5 million and $0.2 million, respectively, of costs related to the cost-sharing provisions of the Otsuka U.S. Agreement, as defined below in Note 4, of which approximately $0.2 million and $0.1 million are reimbursable by Otsuka and recorded as a reduction to research and development expense during the three months ended September 30, 2019 and 2018, respectively. Intangible The Company maintains a definite-lived intangible asset related to developed product rights for Auryxia, which was acquired

Product Revenue and Reserves fo

Product Revenue and Reserves for Variable Consideration	9 Months Ended
	Sep. 30, 2019
Revenue From Contract With Customer [Abstract]
Product Revenue and Reserves for Variable Consideration	3. Product Revenue and Reserves for Variable Consideration To date, the Company’s only source of product revenue has been product revenue from the U.S. sales of Auryxia, which it began recording on December 12, 2018 following the consummation of the Merger. Total net product revenue was $30.0 million and $82.2 million for the three and nine months ended September 30, 2019, respectively. The following table summarizes activity in each of the product revenue allowance and reserve categories for the nine months ended September 30, 2019 (in thousands): Chargebacks and Discounts Rebates, Fees and other Deductions Returns Total Balance at December 31, 2018 $ 516 $ 22,861 $ 360 $ 23,737 Current provisions related to sales in current year 5,617 73,424 1,835 80,876 Adjustments related to prior period sales 13 1,507 — 1,520 Credits/payments made relating to sales in current year (4,108 ) (21,087 ) — (25,195 ) Credits/payments made relating to prior period sales (1,373 ) (46,803 ) (1,907 ) (50,083 ) Balance at September 30, 2019 $ 665 $ 29,902 $ 288 $ 30,855 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.

License, Collaboration and Othe

License, Collaboration and Other Significant Agreements	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
License, Collaboration and Other Significant Agreements	4. License, Collaboration and Other Significant Agreements During the three and nine months ended September 30, 2019 and 2018, the Company recognized the following revenues from its license, collaboration and other significant agreements and had the following deferred revenue balances as of September 30, 2019: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 License, Collaboration and Other Revenue: (in thousands) (in thousands) MTPC Agreement $ — $ — $ 10,000 $ 9,281 Otsuka U.S. Agreement 39,718 29,030 103,461 75,086 Otsuka International Agreement 20,220 24,114 64,643 63,176 Total Proportional Performance Revenue $ 59,938 $ 53,144 $ 178,104 $ 147,543 JT and Torii 1,549 — 4,266 — MTPC Stability Studies 486 25 872 349 Total License, Collaboration and Other Revenue $ 61,973 $ 53,169 $ 183,242 $ 147,892 September 30, 2019 Short-Term Long-Term Total Deferred Revenue: (in thousands) Otsuka U.S. Agreement $ 18,873 $ 28,576 $ 47,449 Otsuka International Agreement 13,269 10,632 23,901 Vifor Agreement — 4,679 4,679 Total $ 32,142 $ 43,887 $ 76,029 The following table presents changes in the Company’s contract assets and liabilities during the nine months ended September 30, 2019 and 2018 (in thousands): Nine Months Ended September 30, 2019 Balance at Beginning of Period Additions Deductions Balance at End of Period Contract assets: Other current assets $ — $ 10,000 $ (10,000 ) $ — Accounts receivable ( 1) $ 1,587 $ 134,268 $ (131,651 ) $ 4,204 Contract liabilities: Deferred revenue $ 112,689 $ 131,444 $ (168,104 ) $ 76,029 Accounts payable $ 13,492 $ — $ (13,492 ) $ — Nine Months Ended September 30, 2018 Contract assets: Other current assets $ — $ 531 $ (531 ) $ — Accounts receivable ( 1) $ 34,186 $ 120,283 $ (153,938 ) $ 531 Contract liabilities: Deferred revenue $ 179,624 $ 119,442 $ (147,543 ) $ 151,523 Accounts payable $ — $ 4,427 $ (1,040 ) $ 3,387 (1) During the three and nine months ended September 30, 2019 and 2018, 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 September 30, Nine Months Ended September 30, Revenue Recognized in the Period from: 2019 2018 2019 2018 Amounts included in deferred revenue at the beginning of the period $ 27,095 $ 53,144 $ 60,441 $ 110,974 Performance obligations satisfied in previous periods $ — $ — $ 1,254 $ 6,813 Mitsubishi Tanabe Pharma Corporation Collaboration Agreement Summary of Agreement On December 11, 2015, the Company and MTPC entered into a collaboration agreement, or 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. The Company and MTPC agreed that, instead of including Japanese patients in the Company’s global Phase 3 program for vadadustat, MTPC would be the sponsor of a Phase 3 program for vadadustat in Japan. Following consultation with the Japanese Pharmaceuticals and Medical Devices Agency, or the PMDA, MTPC initiated its Phase 3 development program for vadadustat in Japanese patients in Japan in the fourth quarter of 2017. MTPC reported top-line data for the two Phase 3 pivotal trials and data from the two supportive Phase 3 studies in March 2019 and 52-week data for the two Phase 3 pivotal trials in November 2019. MTPC is responsible for the costs of the Phase 3 program in Japan and other studies required there, and will make no funding payments for the global Phase 3 program. In July 2019, MTPC submitted a Japanese New Drug Application, or JNDA, to the Ministry of Health, Labor and Welfare in Japan for manufacturing and marketing approval of vadadustat, as a treatment for anemia due to CKD, which triggered a $10.0 million regulatory milestone payment to the Company. MTPC has sole responsibility for the commercialization of vadadustat in the MTPC Territory as well as for Medical Affairs (as defined in the MTPC Agreement) in the MTPC Territory. Akebia is responsible for manufacturing and supplying vadadustat for clinical use in the MTPC Territory. Akebia plans to enter into a supply agreement with MTPC for the commercial supply of vadadustat prior to commercial launch. The Company and MTPC have established a joint steering committee pursuant to the MTPC Agreement to oversee development and commercialization of vadadustat in the MTPC Territory, including approval of any development or commercialization plans. Unless earlier terminated, the MTPC Agreement will continue in effect on a country-by-country basis until the later of the following: expiration of the last-to-expire patent covering vadadustat in such country in the MTPC Territory; expiration of marketing or regulatory exclusivity in such country in the MTPC Territory; or ten years after the first commercial sale of vadadustat in such country in the MTPC Territory. MTPC may terminate the MTPC Agreement upon twelve months’ notice at any time after the second anniversary of the effective date of the MTPC Agreement. Either party may terminate the MTPC Agreement upon the material breach of the other party that is not cured within a specified time period or upon the insolvency of the other party. MTPC is required to make certain milestone payments to the Company aggregating up to approximately $225.0 million upon the achievement of specified development, regulatory and commercial events. More specifically, the Company received $10.0 million in development milestone payments, and is eligible to receive up to $40.0 million in regulatory milestone payments, of which the Company received $10.0 million in relation to the JNDA filing in the third quarter of 2019, and up to $175.0 million in commercial milestone payments associated with aggregate sales of all products. In consideration for the exclusive license and other rights contained in the MTPC Agreement, MTPC also made a $20.0 million upfront payment as well as a payment of $20.5 million for Phase 2 studies in Japanese patients completed by the Company and reimbursed by MTPC. Additionally, if vadadustat is commercialized, the Company would be entitled to receive tiered double-digit royalty payments of up to 20% on sales of vadadustat in the MTPC Territory. Royalty payments are subject to certain reductions, including upon the introduction of competitive products in certain instances. Royalties are due on a country-by-country basis from the date of first commercial sale of a licensed product in a country until the last to occur of: (i) the expiration of the last to expire valid claim within the intellectual property covering the licensed product, (ii) the expiration of marketing or regulatory exclusivity in such country, or (iii) the tenth anniversary of the first commercial sale of such licensed product in such country. Due to the uncertainty of pharmaceutical development and the high historical failure rates associated with drug development, although the Company has received $10.0 million in development milestones and a $10.0 million regulatory milestone, for which payment was received in the third quarter of 2019, no additional milestone or royalty payments may ever be received from MTPC. In September 2017, the Company provided MTPC with an option to access data from the Company’s global Phase 3 vadadustat program for payments to the Company of up to $25.0 million, which is in addition to the milestone payments described above. Revenue Recognition The Company evaluated the elements of the MTPC Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, MTPC, is a customer. The Company’s arrangement with MTPC contains the following material promises under the contract at inception: (i) license under certain of the Company’s intellectual property to develop and commercialize vadadustat (the License Deliverable) in the MTPC Territory, (ii) clinical supply of vadadustat (the Clinical Supply Deliverable), (iii) knowledge transfer, (iv) Phase 2 dosing study research services (the Research Deliverable), and (v) rights to future know-how. The Company has 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. The Company did not develop a best estimate of standalone selling price for the License, Research and Clinical Supply Performance Obligation because the estimate of standalone selling price associated with the Rights to Future Know-How Performance Obligation was determined to be immaterial. The Company has concluded that a change in the key assumptions used to determine the best estimate of standalone selling price for each performance obligation would not have a significant impact on the allocation of arrangement consideration. The deliverables associated with the License, Research and Clinical Supply Performance Obligation were satisfied as of June 30, 2018. The transaction price at inception was comprised of: (i) the up-front payment, (ii) the estimated cost for the Phase 2 studies, (iii) a non-substantive milestone associated with the first patient enrolled in the NDD-CKD Phase 3 study, and (iv) the cost of all clinical supply provided to MTPC for the Phase 3 studies. No other development and no regulatory milestones were included in the transaction price at inception, as all other milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. The total aggregate amount of development milestones is $10.0 million and the total aggregate amount of the regulatory milestones is up to $40.0 million. The total aggregate amount of sales milestones is up to $175.0 million. Any consideration related to sales-based milestones (including royalties) will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to MTPC and therefore have also been excluded from the transaction price. The Company re-evaluates the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. As of September 30, 2019, the transaction price is 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, comprised of a $6.0 million and a $4.0 million development milestone, and (v) the $10.0 million regulatory milestone relating to the JNDA filing. As of September 30, 2019, all development milestones have been achieved and, other than the $10.0 million regulatory milestone received by the Company related to the filing of the JNDA that was achieved, no other regulatory milestones have been assessed as probable of being achieved and as a result have been fully constrained. Revenue for the License, Research and Clinical Supply Performance Obligation for the MTPC Agreement is being recognized using a proportional performance method. Accordingly, the Company recognized the $10.0 million regulatory milestone for the filing of the JNDA as revenue during the nine months ended September 30, 2019 as the regulatory milestone was both deemed probable of being achieved and the required performance obligations had been satisfied as of September 30, 2019. The Company recognized approximately $9.3 million during the nine months ended September 30, 2018. The revenue is classified as collaboration revenue in the accompanying unaudited condensed consolidated statements of operations. No revenues were recognized for the three months ended September 30, 2019 and 2018 with respect to the MTPC Agreement. As of September 30, 2019, there is no deferred revenue, no accounts receivable, and no contract assets. There were no asset or liability balances classified as long-term in the unaudited condensed consolidated balance sheet as of September 30, 2019. U.S. Collaboration and License Agreement with Otsuka Pharmaceutical Co. Ltd. Summary of Agreement On December 18, 2016, the Company entered into a collaboration and license agreement with Otsuka, or the Otsuka U.S. Agreement. The collaboration is focused on the development and commercialization of vadadustat in the U.S. Under the terms of the Otsuka U.S. Agreement, the Company is responsible for leading the development of vadadustat, including the ongoing Phase 3 development program. The Company and Otsuka will co-commercialize vadadustat in the U.S., subject to the approval of vadadustat by the FDA. 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 accordance with the associated plans. The co-exclusive license relates to activities that will be jointly conducted by the Company and Otsuka pursuant to the terms of the Otsuka U.S. Agreement. Additionally, the parties agreed not to promote, market or sell any competing product in the territory covered by the agreement. The Company is responsible for performing all activities related to the development of vadadustat as outlined in the current global development plan. The current global development plan encompasses all activities with respect to the ongoing PRO 2 2 Under the Otsuka U.S. Agreement, the parties jointly conduct, and have equal responsibility for, all medical affairs, commercialization and non-promotional activities pursuant to underlying plans as agreed to by the parties. If approved by the FDA, the Company plans to provide vadadustat to Otsuka for commercialization pursuant to a separate supply agreement to be negotiated. The activities under the Otsuka U.S. Agreement are governed by a joint steering committee, or JSC, formed by an equal number of representatives from the Company and Otsuka. The JSC coordinates and monitors the parties’ activities under the collaboration. Among other responsibilities, the JSC manages the overall strategic alignment between the parties, oversees the current global development plan and reviews other detailed plans setting forth the parties’ activities under the arrangement, including the medical affairs plan and commercialization and non-promotional activities plan. Additionally, the parties established a joint development committee, or JDC, which is comprised of an equal number of representatives from the Company and Otsuka. Among other responsibilities, the JDC shares information related to, and reviews and discusses activities and progress under, the current global development plan and any other development that may be conducted pursuant to the collaboration. The Company and Otsuka also established a joint manufacturing committee, or JMC, which is comprised of an equal number of representatives from each of the parties. Among other responsibilities, the JMC oversees the manufacturing plan and related manufacturing activities. In support of the potential commercialization of vadadustat, the parties established a joint commercialization committee, or JCC, which is comprised of an equal number of representatives from the Company and Otsuka. Among other responsibilities, the JCC oversees the activities and progress under the commercialization and non-promotional activities plan and all other sales and marketing activities. The Company has retained final decision-making authority with respect to certain matters, including U.S. pricing strategy and certain other key commercialization matters. Under the terms of the Otsuka U.S. Agreement, the Company received a $125.0 million up-front, non-refundable, non-creditable cash payment in December 2016. In March 2017, the Company received a payment of approximately $33.8 million, which represented reimbursement for Otsuka’s share of costs previously incurred by the Company in implementing the current global development plan through December 31, 2016. Commencing in the third quarter of 2017, whereupon the Company had incurred a specified amount of incremental costs, Otsuka began to contribute, as required by the Otsuka U.S. Agreement, a percentage of the remaining costs incurred under the current global development plan. The Company estimates that Otsuka’s funding of the current global development plan costs subsequent to December 31, 2016 will total $232.3 million or more, depending on the actual costs incurred toward the current global development plan. The $232.3 million estimate includes $168.6 million in base funding and $63.7 million in estimated additional funding that is expected to result from the Company’s exercise of the Otsuka Funding Option, described below, or the Additional Funding. The costs associated with the performance of any development activities in addition to those outlined in the current global development plan will be subject to a cost sharing or reimbursement mechanism to be determined by the parties. Costs incurred with respect to medical affairs and commercialization and non-promotional activities will generally be shared equally by the parties. In addition, due to the costs incurred in completing the activities under the current global development plan exceeding a certain threshold in the second quarter of 2019, 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. The Company estimates that the Additional Funding is estimated to total $63.7 million or more, depending on the actual costs incurred toward the current global development plan. The Additional Funding is fully creditable against future payments due to the Company under the arrangement, provided that future payments due to the Company may not be reduced by more than 50% in any calendar year and any remaining creditable amount above 50% in any calendar year will be applied to subsequent future payments until fully credited. As of September 30, 2019, the Additional Funding was $26.1 million. In addition, Otsuka is required to make certain milestone payments to the Company upon the achievement of specified development, regulatory and commercial events. More specifically, the Company is eligible to receive up to $125.0 million in development milestone payments and up to $65.0 million in regulatory milestone payments for the first product to achieve the associated event. Moreover, the Company is eligible for up to $575.0 million in commercial milestone payments associated with aggregate sales of licensed products, subject to reduction as a result of the Company’s exercise of the Otsuka Funding Option, as described above, the Additional Funding for which, as of September 30, 2019, totaled $26.1 million. Due to the uncertainty of pharmaceutical development and the high historical failure rates associated therewith, no milestone payments may ever be received from Otsuka. Under the Otsuka U.S. Agreement, the Company and Otsuka share the costs of developing and commercializing vadadustat in the U.S. and the profits from the sales of vadadustat after approval by the FDA. In connection with the profit share calculation, net sales include gross sales to third-party customers net of discounts, rebates, chargebacks, taxes, freight and insurance charges and other applicable deductions. Shared costs generally include costs attributable or reasonably allocable to the manufacture of vadadustat for commercialization purposes and the performance of medical affairs activities, non-promotional activities and commercialization activities. Unless earlier terminated, the Otsuka U.S. Agreement will expire in the U.S. on a product-by-product basis on the date that one or more generic versions of vadadustat first achieves 90% market penetration. Either party may terminate the Otsuka U.S. Agreement in its entirety upon an uncured breach or insolvency on the part of the other party. Otsuka may terminate the Otsuka U.S. Agreement in its entirety upon 12 months’ prior written notice at any time after the release of the first topline data from the global Phase 3 development program for vadadustat. In the event of termination of the Otsuka U.S. Agreement, all rights and licensees granted to Otsuka under the Otsuka U.S. Agreement will automatically terminate and the licenses granted to the Company will become freely sublicensable. In addition, the upfront payment, all development costs and milestone payments received by the Company prior to such termination will not be refunded to Otsuka. Revenue Recognition The Company evaluated the elements of the Otsuka U.S. Agreement in accordance with the provisions of ASC 606 and concluded that the contract counterparty, Otsuka, is a customer. The Company’s arrangement with Otsuka contains the following material promises under the contract at inception: (i) license under certain of the Company’s intellectual property to develop, perform medical affairs activities with respect to and conduct non-promotional and commercialization activities related to vadadustat and products containing or comprising vadadustat (the License Deliverable), (ii) development services to be performed pursuant to the current global development plan (the Development Services Deliverable), (iii) rights to future intellectual property (the Future IP Deliverable), and (iv) joint committee services (the Committee Deliverable). The Company has identified three performance obligations in connection with its obligations under the Otsuka U.S. Agreement. Factors considered in making the assessment of which material promises will be accounted for as separate performance obligations included, among other things, the capabilities of the collaboration partner, whether any other vendor sells the item separately, whether the good or service is highly interdependent or highly interrelated to the other elements in the arrangement, and whether there are other vendors that can provide the items. Additionally, the Otsuka U.S. Agreement does not include a general right of return. The three performance obligations identified in connection with the Company’s obligations under the Otsuka U.S. Agreement are as follows: ( i ) License and Development Services Combined (License Performance Obligation) The License Deliverable is not distinct from the Development Services Deliverable, due to the limitations inherent in the license conveyed. More specifically, the license conveyed to Otsuka does not provide Otsuka with the right to manufacture vadadustat and products containing or comprising vadadustat. However, the manufacturing and supply services that are conducted as part of the services to be performed pursuant to the current global development plan are necessary for Otsuka to fully exploit the associated license for its intended purpose. The value of the rights provided through the license conveyed will be realized when the underlying products covered by the intellectual property progress through the development cycle, receive regulatory approval and are commercialized. Products containing or comprising vadadustat cannot be commercialized until the development services under the current global development plan are completed. Accordingly, Otsuka must obtain the manufacturing and supply of the associated products that are included within the development services to be performed pursuant to the current global development plan from the Company in order to derive benefit from the license, which significantly limits the ability for Otsuka to utilize the License Deliverable for its intended purpose in a way that generates economic benefits. (ii) Rights to Future Intellectual Property (Future IP Performance Obligation) The License and Development Services deliverables combined are distinct from the Future IP Deliverable because Otsuka can obtain the value of the license using the clinical trial materials implicit in the development services without the receipt of any other intellectual property that may be discovered or developed in the future. The Future IP Deliverable is distinct from the Committee Deliverable because the joint committee services have no bearing on the value to be derived from the rights to potential future intellectual property. As a result, the Future IP Deliverable qualifies as a separate performance obligation. (iii) Joint Committee Services (Committee Performance Obligation) The License and Development Services deliverables combined are distinct from the Committee Deliverable because Otsuka can obtain the value of the license using the clinical trial materials implicit in the development services without the joint committee services. The Committee Deliverable also is distinct from the rights to Future IP Deliverable because the joint committee services have no bearing on the value to be derived from the rights to potential future intellectual property. As a result, the Committee Deliverable qualifies as a separate 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 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 has concluded that a change in the key assumptions used to determine the best estimate of standalone selling price for each performance obligation would not have a significant impact on the allocation of arrangement consideration. The transaction price at inception was comprised of: (i) the up-front payment, (ii) the cost share payment with respect to amounts incurred by the Company through December 31, 2016, and (iii) an estimate of the cost share payments to be received with respect to amounts incurred by the Company subsequent to December 31, 2016. No development or regulatory milestones were included in the transaction price at inception, as all milestone amounts were fully constrained. As part of its evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestones is outside the control of the Company and contingent upon success in future clinical trials and the licensee’s efforts. Any consideration related to sales-based milestones will be recognized when the related sales occur as they were determined to relate predominantly to the license granted to Otsuka and therefore have also been excluded from the transaction price. The Company re-evaluates the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. No amounts were allocated to the Future IP Performance Obligation because the associated best estimate of standalone selling price was determined to be immaterial. Due to the similar performance period and recognition pattern between the License Performance Obligation and the Committee Performance Obligation, the transaction price has been allocated to the License Performance Obligation and the Committee Performance Obligation on a combined basis. Accordingly, the Company will recognize revenue related to the allocable arrangement consideration on a proportional performance basis as the underlying development services are performed pursuant to the current global development plan which is commensurate with the period and consistent with the pattern over which the Company’s obligations are satisfied for both the License Performance Obligation and the Committee Performance Obligation. Effectively, the Company has treated the arrangement as if the License Performance Obligation and the Committee Performance Obligation are a single performance obligation. As of September 30, 2019, the transaction price totaling $391.1 million is comprised of: (i) the up-front payment of $125.0 million, (ii) the cost share payment with respect to amounts incurred by the Company through December 31, 2016 of $33.8 million, (iii) the estimate of the base cost share payments to be received of approximately $168.6 million with respect to amounts incurred by the Company subsequent to December 31, 2016, and (iv) the estimate of the Additional Funding of approximately $63.7 million related to incremental cost share payments under the Otsuka Funding Option described above. As of September 30, 2019, no development or regulatory milestones have been assessed as probable of being reached and thus have been fully constrained. During the three months ended September s 30, 2019 and 2018, the Company recognized revenue totaling approximately $39.7 million and $29.0 million, respectively, and $103.5 million and $75.1 million during the nine months ended September 30, 2019 and 2018, 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 September 30, 2019, there is approximately $47.5 million of deferred revenue related to the Otsuka U.S. Agreement of which $18.9 million is classified as current and $28.6 million is classified as long-term in the accompanying unaudited condensed consolidated balance sheet based on the performance period of the underlying obligations. Additionally, as of September 30, 2019, there is approximately $1.2 million in accounts receivable in the accompanying unaudited condensed consolidated balance sheet. As of December 31, 2018, there was approximately $7.2 million in contract liabilities (included in accounts payable) in the consolidated balance sheet. The Company determined that the medical affairs, commercialization and non-promotional activities elements of the Otsuka U.S. Agreement represent joint operating activities in which both parties are active participants and of which both parties are exposed to significant risks and rewards that are dependent on the success of the activities. Accordingly, the Company is accounting for the joint medical affairs, commercialization and non-promotional activities in accordance with ASC No. 808, Collaborative Arrangements Revenue from Contracts with Customers – Scope and Scope Exceptions International Collaboration and License Agreement with Otsuka Pharmaceutical Co. Ltd. Summary of Agreement On April 25, 2017, the Company entered into a collaboration and license agreement with Otsuka, or the Otsuka International Agreement. The collaboration is 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 i

Business Combination

Business Combination	9 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
Business Combination	5. Business Combination On December 12, 2018, the Company completed the Merger with Keryx. Keryx focused on the development and commercialization of medicines for people with kidney disease. Keryx’s proprietary product, Auryxia, is approved by the FDA for two indications: (1) the control of serum phosphorus levels in adult patients with DD-CKD and (2) the treatment of iron deficiency anemia in adult patients with NDD-CKD. Pursuant to the terms and conditions of the Merger Agreement, e ach outstanding Keryx Share, excluding the Baupost Additional Shares, as defined below, and each outstanding Keryx equity award were converted into Akebia Shares and substantially similar Akebia equity awards, respectively, at an exchange ratio of 0.37433 for a t Fair value of 57,773,090 Akebia Shares $ 516,492 Fair value of 602,752 Akebia RSUs 304 Fair value of 3,967,290 Akebia stock options 10,958 Total consideration $ 527,754 I mmediately prior to the Merger, Baupost Group Securities, L.L.C., or Baupost, agreed to convert its $164.7 million of Keryx’s Convertible Notes into 35,582,335 Keryx Shares, in accordance with the terms of the governing indenture agreement, in exchange for an additional 4,000,000 Keryx Shares, or the Baupost Additional Shares. The aggregate 39.6 million Keryx Shares were then converted into Akebia Shares at the 0.37433 exchange ratio. The fair value of the Baupost Additional Shares, on an as-converted basis, of $13.4 million has been excluded from the purchase price and recorded within selling, general and administrative expenses in the Company’s consolidated financial statements Business Combinations . The Company has allocated the $527.8 million purchase price to the identifiable assets acquired and liabilities assumed in the business combination at their fair values as of December 12, 2018 as follows Cash and cash equivalents $ 5,257 Inventory 235,597 Trade accounts receivable, net 15,834 Prepaid expenses and other current assets 8,399 Goodwill 55,053 Intangible assets: Developed product rights for Auryxia 329,130 Other intangible assets 545 Property and equipment, net 3,646 Other assets 14,441 Accounts payable (17,570 ) Accrued expenses (42,972 ) Deferred tax liability (35,096 ) Debt (15,000 ) Fair value of unfavorable executory contract (29,510 ) Total purchase price $ 527,754 In performing the purchase price allocation, the Company considered, among other factors, the intended future use of acquired assets, analysis of historical financial performance and estimates of future performance of Keryx’s business. As part of the purchase price allocation, the Company identified developed product rights for Auryxia as the primary intangible asset. The fair value of the developed product rights for Auryxia was determined using the multi-period excess earnings method which is a variation of the income approach, and is a valuation technique that provides an estimate of the fair value of an asset based on the principle that the value of an intangible asset is equal to the present value of the incremental after-tax cash flows attributable to the asset, after taking charges for the use of other assets employed by the business. Key estimates and assumptions used in this model were projected revenues and expenses related to the asset, estimated contributory asset charges, and a risk-adjusted discount rate of 20.0% used to calculate the present value of the future expected cash inflows from the asset. The intangible asset is being amortized on a straight-line basis over its estimated useful life, which for Auryxia is nine years. The Company also identified an executory contract in the supply agreement between Keryx and BioVectra Inc., or BioVectra, which includes future firm purchase commitments. This executory contract was deemed to have an off-market element related to the amount of purchase commitments that exceed the current forecast and as such, the Company recorded a liability in purchase accounting. As of the acquisition date, the preliminary fair value of the off-market element was $29.5 million. The preliminary goodwill represents the excess of the purchase price over the estimated fair value of net assets acquired. The factors contributing to the recognition of goodwill were based on several strategic and synergistic benefits that were expected to be realized from the Merger. These benefits included the expectation that the combined company would establish itself as a leading renal company with enhanced position and large market opportunity, synergistic utilization of Keryx’s commercial organization, and strengthening the combined company’s financial profile. Such goodwill is not deductible for tax purposes. In connection with the Merger, the Company identified a preliminary deferred tax liability of $35.1 million as a result of the difference in the book basis and tax basis related to the identifiable inventory, other intangible assets, net and other liability. There can be no assurance that such finalizations will not result in material changes from the preliminary purchase price allocation. The Company’s estimates and assumptions are subject to change during the measurement period, which is up to one year from the acquisition date, as the Company finalizes the valuations of assets acquired and liabilities assumed.

Available for Sale Securities

Available for Sale Securities	9 Months Ended
	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Available for Sale Securities	6. Available For Sale Securities Available for sale securities at September 30, 2019 and December 31, 2018 consisted of the following : Gross Gross Unrealized Unrealized Amortized Cost Gains Losses Fair Value (in thousands) September 30, 2019 Cash and cash equivalents $ 122,886 $ — $ — $ 122,886 Available for sale securities: Certificates of deposit $ 245 $ — $ — $ 245 U.S. government debt securities 22,476 6 — 22,482 Total available for sale securities $ 22,721 $ 6 $ — $ 22,727 Total cash, cash equivalents, and available for sale securities $ 145,607 $ 6 $ — $ 145,613 Gross Gross Unrealized Unrealized Amortized Cost Gains Losses Fair Value (in thousands) December 31, 2018 Cash and cash equivalents $ 104,644 $ — $ — $ 104,644 Available for sale securities: Certificates of deposit $ 245 — — $ 245 U.S. government debt securities 158,518 1 (198 ) 158,321 Corporate debt securities 58,494 — (64 ) 58,430 Total available for sale securities $ 217,257 $ 1 $ (262 ) $ 216,996 Total cash, cash equivalents, and available for sale securities $ 321,901 $ 1 $ (262 ) $ 321,640 The estimated fair value of the Company’s available for sale securities balance at September 30, 2019, by contractual maturity, was as follows: Due in one year or less $ 22,727 Due after one year — Total available for sale securities $ 22,727 There were no realized gains or losses on available for sale securities for the three and nine months ended September 30, 2019 and 2018. Additionally, the Company did not have any available for sale securities that were in an unrealized loss position as of September 30, 2019. The following table summarizes the Company’s available for sale securities that were in a continuous unrealized loss position, but were not deemed to be other-than temporarily impaired, as of December 31, 2018: Unrealized Loss for Less Than 12 Months Unrealized Loss for 12 Months or More Total Gross Gross Gross Unrealized Estimated Unrealized Estimated Unrealized Estimated Losses Fair Value Losses Fair Value Losses Fair Value (in thousands) December 31, 2018 Available for sale securities: U.S. government debt securities $ (159 ) $ 116,026 $ (39 ) $ 29,934 $ (198 ) $ 145,960 Corporate debt securities (64 ) 58,430 — — (64 ) 58,430 Total $ (223 ) $ 174,456 $ (39 ) $ 29,934 $ (262 ) $ 204,390 As noted above, there were no securities as of September 30, 2019 that were in an unrealized loss position. There were 51 securities as of December 31, 2018, that were in an unrealized loss position. The Company considered the decline in the market value of these securities to be primarily attributable to current economic conditions. The contractual terms of these securities do not permit the issuer to settle the securities at a price less than the amortized cost basis of the investment.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	7. Fair Value of Financial Instruments The Company utilizes a portfolio management company for the valuation of the majority of its investments. This 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 and marketable securities within Level 1 or Level 2. This is because the Company values its cash equivalents and marketable securities 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 September 30, 2019 and December 31, 2018 are summarized below: Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) September 30, 2019 Assets: Cash and cash equivalents $ 122,886 $ — $ — $ 122,886 Certificates of deposit — 245 — 245 U.S. government debt securities — 22,482 — 22,482 $ 122,886 $ 22,727 $ — $ 145,613 Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) December 31, 2018 Assets: Cash and cash equivalents $ 104,644 $ — $ — $ 104,644 Certificates of deposit — 245 — 245 U.S. government debt securities — 158,321 — 158,321 Corporate debt securities — 58,430 — 58,430 $ 104,644 $ 216,996 $ — $ 321,640 The Company’s corporate debt securities are all investment grade. The Company had no assets or liabilities measured at fair value on a recurring basis using significant unobservable inputs (Level 3) at September 30, 2019 and December 31, 2018. Investment securities are exposed to various risks such as interest rate, market and credit risks. Due to the level of risk associated with certain investment securities and the level of uncertainty related to changes in the value of investment securities, it is at least reasonably possible that changes in risks in the near term would result in material changes in the fair value of investments.

Inventory

Inventory	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
Inventory	8. Inventory The components of inventory are summarized as follows: September 30, 2019 December 31, 2018 (in thousands) Raw materials $ 2,824 $ 1,880 Work in process 152,208 215,122 Finished goods 45,863 18,182 Total inventory $ 200,895 $ 235,184 Long-term inventory, which primarily consists of raw materials and work in process, is included in other assets in the Company’s consolidated balance sheets. September 30, 2019 December 31, 2018 (in thousands) Balance Sheet Classification: Inventory $ 115,987 $ 114,245 Other assets 84,908 120,939 Total inventory $ 200,895 $ 235,184 Inventory amounts written down as a result of excess, obsolescence, scrap or other reasons and charged to cost of goods sold totaled $2.9 million and $6.0 million during the three and nine months ended September 30, 2019. The Company did not have any inventory write-offs during the three and nine months ended September 30, 2018, respectively, as there were no inventory amounts prior to the Merger on December 12, 2018. 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 sales in the unaudited condensed consolidated statement of operations.

Intangible Assets and Goodwill

Intangible Assets and Goodwill	9 Months Ended
	Sep. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Intangible Assets and Goodwill	9. Intangible Assets and Goodwill Intangible Assets The following table presents the Company’s intangible assets at September 30, 2019 and December 31, 2018 (in thousands): September 30, 2019 Gross Carrying Value Accumulated Amortization ASC 842 Adjustment Total Estimated useful life Acquired intangible assets: Developed product rights for Auryxia $ 329,130 $ (28,818 ) $ — $ 300,312 9 Years Favorable lease 545 (5 ) (540 ) — N/A Total $ 329,675 $ (28,823 ) $ (540 ) $ 300,312 December 31, 2018 Gross Carrying Value Accumulated Amortization Total Estimated useful life Acquired intangible assets: Developed product rights for Auryxia $ 329,130 $ (1,517 ) $ 327,613 9 Years Favorable lease 545 (5 ) 540 4 Years Total $ 329,675 $ (1,522 ) $ 328,153 On December 12, 2018, the Company completed the Merger, whereby it acquired certain definite-lived intangible assets, including the developed product rights for Auryxia and a favorable lease. The Company amortizes its definite-lived intangible assets acquired as part of the Merger using the straight-line method, which is considered the best estimate of economic benefit, over its estimated useful life. As a result of the adoption of ASC 842 on January 1, 2019, the Company reclassed the remaining balance of the favorable lease intangible asset into the operating lease asset. The Company recorded $9.1 million and $27.3 million in amortization expense related to the developed product rights for Auryxia during the three and nine months ended September 30, 2019, respectively. Estimated future amortization expense for the intangible asset as of September 30, 2019 is as follows (in thousands): Total 2019 $ 9,100 2020 36,402 2021 36,401 2022 36,402 2023 36,401 Thereafter 145,606 $ 300,312 Goodwill Goodwill was $55.1 million as of September 30, 2019 and December 31, 2018, derived as follows (in thousands): Total Merger consideration $ 527,754 Less: Fair value of identified acquired assets and liabilities, net (472,701 ) Goodwill $ 55,053 Goodwill will be evaluated for impairment on an annual basis as of October 1, and more frequently if indicators are present or changes in circumstances suggest that an impairment may exist.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2019
Payables And Accruals [Abstract]
Accrued Expenses	10. Accrued Expenses Accrued expenses as of September 30, 2019 and December 31, 2018 are as follows: September 30, 2019 December 31, 2018 (in thousands) Accrued clinical expenses $ 66,194 $ 71,881 Product revenue allowances 28,408 22,861 Accrued bonus 7,740 9,537 Lease liability 4,884 — Accrued commercial manufacturing 3,352 6,383 Royalties 2,697 2,430 Professional fees 2,393 2,367 Accrued payroll 1,208 2,255 Accrued vacation 926 1,088 Accrued severance 79 3,962 Merger costs — 16,071 Accrued other 8,763 12,082 Total accrued expenses $ 126,644 $ 150,917

Debt

Debt	9 Months Ended
	Sep. 30, 2019
Debt Disclosure [Abstract]
Debt	11. Debt Term Loans On November 11, 2019, the Company entered into a loan agreement, or the Loan Agreement, with Keryx as guarantor, BioPharma Credit PLC as collateral agent and a lender, or the Collateral Agent, and BioPharma Credit Investments V (Master) LP as a lender, collectively Pharmakon, pursuant to which term loans in an aggregate principal amount of $100.0 million are made available to the Company in two tranches, subject to certain terms and conditions, or the Term Loans. Subject to the satisfaction of certain conditions, the first tranche of $80.0 million, or Tranche A, will be drawn in a single drawing on November 25, 2019, or the Tranche A Funding Date. The second tranche, available until December 31, 2020, allows the Company to borrow, at its option, an additional $20.0 million, or Tranche B. The date on which Tranche B is drawn, the Tranche B Funding Date, and 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. As a condition to the funding of Tranche A, the Company and Keryx are obligated to enter 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 will be unconditionally guaranteed by Keryx, or the Guarantee. Additionally, the obligations of the Company and Keryx under the Term Loans and the Guarantee will be 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, if certain conditions are met, it will have the option to repay the principal in equal quarterly payments starting on the 48th-month anniversary of the applicable Funding Date, or collectively the Amortization Schedule. 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 will pay to Pharmakon a facility fee equal to 2.00% of the aggregate principal amount of the Term Loans. 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 starting in 2021, and on a quarterly basis, a minimum net sales threshold for Auryxia starting in the fourth quarter of 2020. 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. Revolving Keryx, the Company’s wholly owned subsidiary following the Merger, had a $40.0 million revolving line of credit, or the Line of Credit, under its Loan and Security Agreement with Silicon Valley Bank, or SVB. On July 31, 2019, Keryx entered into a Waiver and First Amendment to Loan and Security Agreement, or the Loan Amendment. Pursuant to the Loan Amendment, certain revisions were made to the Loan and Security Agreement, including requiring Keryx to maintain, from and after December 31, 2019, subject to certain exceptions, a certain amount of funds to which the Company had unrestricted access in one or more asset management accounts with SVB or SVB’s affiliate and revising certain of the representations and warranties and covenants in the Loan and Security Agreement. In addition, pursuant to the Loan Amendment, SVB waived the then-existing events of default. On August 7, 2019, the Company executed and delivered to SVB an Unconditional Guaranty, or the Guaranty, pursuant to which the Company guaranteed the prompt and complete payment and performance when due of all of the obligations and liabilities of Keryx under the Loan and Security Agreement, as amended by the Loan Amendment, or the Amended Loan Agreement. In addition, the Company entered into a Security Agreement with SVB effective August 7, 2019, or the Security Agreement, pursuant to which the Company granted to SVB a continuing first priority security interest in substantially all of the Company’s personal property, other than the Company’s intellectual property, to secure the payment and performance of the Company’s obligations under the Guaranty. The Company’s obligations under the Guaranty were independent of Keryx’s obligations, and separate actions may be brought against the Company. Availability under the Line of Credit was subject to a borrowing base comprised of eligible receivables and eligible inventory of Keryx as set forth in the Loan and Security Agreement. As of September 30, 2019 and December 31, 2018, there was $0 and $15.0 million outstanding, respectively, under the Line of Credit and the Company had approximately $29.4 million in available borrowing base as of September 30, 2019. The principal amount outstanding under the Loan and Security Agreement bore interest at a floating rate per annum equal to the greater of (i) 2.0% above the “prime rate,” as reported in The Wall Street Journal and (ii) 6.75%, which interest was payable monthly. Principal amounts borrowed under the Line of Credit may have been repaid and, prior to the maturity date, re-borrowed, subject to the terms and conditions set forth in the Loan and Security Agreement. Upon entry into the Loan and Security Agreement (payable in installments and subject to certain conditions), and at the one year anniversary of the effective date of the Loan and Security Agreement (or, if earlier, upon termination of or an event of default under the Loan and Security Agreement), Keryx paid to SVB a fee equal to 1.00% of the Line of Credit. Keryx was also required to pay on a quarterly basis a fee equal to 0.25% per annum of the average unused portion of the Line of Credit. Pursuant to the terms of the Loan and Security Agreement, Keryx was required to pay a termination fee of 2.00% of the Line of Credit, if the Loan and Security Agreement was terminated prior to the maturity date of July 18, 2020, subject to certain exceptions. The Company terminated the Loan and Security Agreement, the Unconditional Guaranty, and the Security Agreement on November 7, 2019, and Keryx paid SVB a termination fee of $0.8 million. During the three and nine months ended September 30, 2019, the Company recognized approximately $37,000 and $0.4 million, respectively, of interest expense related to the Line of Credit. The Company did not incur any amortization expense related to the origination fee and other additional fees noted above as such fees were included in the fair value of the Line of Credit as of December 12, 2018, the date on which the Merger was consummated, in accordance with ASC 805.

Warrant

Warrant	9 Months Ended
	Sep. 30, 2019
Warrant Disclosure [Abstract]
Warrant	12. Warrant In connection with the Janssen Agreement, in February 2017 the Company issued a warrant to purchase 509,611 shares of the Company’s common stock at an exercise price of $9.81 per share. The warrant was fully vested upon issuance and is exercisable in whole or in part, at any time prior to February 9, 2022. The warrant satisfied the equity classification criteria of ASC 815, and is therefore classified as an equity instrument. The fair value at issuance of $3.4 million was calculated using the Black Scholes option pricing model and was charged to research and development expense as it represented consideration for a license for which the underlying intellectual property was deemed to have no alternative future use. As of September 30, 2019, the warrant remains outstanding and expires on February 9, 2022.

Stockholders' Equity

Stockholders' Equity	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Stockholders' Equity	13. Stockholders’ Equity Authorized and Outstanding Capital Stock As of September 30, 2019, the authorized capital stock of the Company included 175,000,000 shares of common stock, par value $0.00001 per share, of which 118,863,735 and 116,887,518 shares were issued and outstanding at September 30, 2019 and December 31, 2018, respectively; and 25,000,000 shares of undesignated preferred stock, par value $0.00001 per share, of which 0 shares were issued and outstanding at September 30, 2019 and December 31, 2018. Retired Shares In April 2019, the Company repurchased and retired 55,324 shares of common stock. The proceeds from the disposition of these shares were used by certain officers of the Company to cover tax liabilities associated with previously vested RSUs. Equity Plans On February 28, 2014, the Company’s Board of Directors adopted its 2014 Incentive Plan and its 2014 Employee Stock Purchase Plan, or the 2014 ESPP, which were subsequently approved by its shareholders and became effective upon the closing of the Company’s initial public offering on March 25, 2014. The Company’s 2014 Incentive Plan was subsequently amended on December 11, 2018, which amendment did not require shareholder approval. The Company’s 2014 Incentive Plan, as amended, is referred to as the 2014 Plan. 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 shareholders approved the Amended and Restated 2014 Employee Stock Purchase Plan, or the ESPP. In May 2016, the Company’s Board of Directors approved an inducement award program that was separate from the Company’s equity plans and which, consistent with Nasdaq Listing Rule 5635(c)(4), did not require shareholder approval, or the Inducement Award Program. For 2019, the Company authorized the issuance of up to 3,150,000 shares for the purpose of granting options to purchase shares of the Company’s common stock to new hires under the Inducement Award Program, of which 1,228,900 options to purchase Akebia Shares were granted during the nine months ended September 30, 2019, of which 1,208,100 options to purchase Akebia Shares remained outstanding at September 30, 2019. 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 Akebia Shares outstanding 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 Shares, 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. During the nine months ended September 30, 2019, the Company granted 2,028,625 options to purchase Akebia Shares to employees under the 2014 Plan, 1,228,900 options to purchase Akebia Shares to employees under the Inducement Award Program, 4,430,945 Akebia RSUs to employees under the 2014 Plan, 180,900 options to purchase Akebia Shares to directors under the 2014 Plan, and 123,300 Akebia RSUs to directors under the 2014 Plan. The ESPP provides for the issuance of options to purchase shares of the Company’s common stock to participating employees at a discount to their fair market value. As noted above, the Company’s stockholders approved the ESPP, which amended and restated the Company’s 2014 ESPP, on June 6, 2019. The maximum aggregate number of shares at September 30, 2019 of the Company’s common stock available for future issuance under the ESPP is 5,715,992. Under the ESPP, each offering period is six months, at the end of which employees may purchase shares of the Company’s common stock through payroll deductions made over the term of the offering. The per-share purchase price at the end of each offering period is equal to the lesser of eighty-five percent (85%) of the closing price of the Company’s common stock at the beginning or end of the offering period. Shares Reserved for Future Issuance The Company has reserved for future issuance the following number of shares of common stock: September 30, 2019 December 31, 2018 Common stock options and RSUs outstanding (1) 12,618,799 9,309,204 Shares available for issuance under Akebia equity plans (2) 4,684,048 4,526,563 Warrant to purchase common stock 509,611 509,611 Shares available for issuance under the ESPP (3) 5,715,992 603,522 Total 23,528,450 14,948,900 (1) (2) On January 1, 2019, January 1, 2018 and January 1, 2017, the shares reserved for future grants under the 2014 Plan increased by 3,801,198, 1,575,329 and 1,265,863 shares, respectively, pursuant to the 2014 Plan Evergreen Provision. On December 12, 2018, the shares reserved for future grants under the 2014 Plan increased by 2,323,213 shares as a result of the Company’s addition of the Assumed Shares to the 2014 Plan. On December 19, 2017, the Company’s Board of Directors approved 750,000 shares for issuance as option awards in fiscal year 2018 under the Inducement Award Program. Additionally, on January 30, 2019, the Company’s Board of Directors approved 3,150,000 shares for issuance as option awards in fiscal year 2019 under the Inducement Award Program, or the 2019 Inducement Shares. (3) On June 6, 2019, the shares reserved for future issuance under the ESPP increased by 5,200,000 shares upon shareholder approval of the Amended and Restated 2014 Employee Stock Purchase Plan. On February 28, 2018 and February 28, 2017, the shares reserved for future issuance under the 2014 ESPP remained unchanged. There were no increases in the shares reserved for future issuance pursuant to the evergreen provision under the 2014 ESPP in 2017 and 2018 as the maximum aggregate number of shares available for purchase under the 2014 ESPP had reached its cap of 739,611 on February 28, 2016. Stock-Based Compensation Stock Options Service-Based Stock Options On February 28, 2019, as part of the Company’s annual grant of equity, the Company issued 2,028,625 stock 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. Options granted by the Company 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 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 ten years after the date of grant. The Company recorded approximately $1.3 million and $1.5 million of stock-based compensation expense related to stock options during the three months ended September 30, 2019 and 2018, respectively, and approximately $3.5 million and $5.1 million during the nine months ended September 30, 2019 and 2018, respectively. Performance-Based Stock Options On December 12, 2018, pursuant to the Merger Agreement, each outstanding and unexercised performance-based option to acquire Keryx Shares granted under a Keryx equity plan converted into a service-based option or performance-based option to acquire Akebia Shares, with the number of shares and exercise price adjusted by the Exchange Multiplier. As a result, the Company issued 233,954 performance-based options related to the Merger. The Company did not have any performance-based options outstanding in fiscal year 2018 prior to the consummation of the Merger. The Company did not issue any performance-based options during the nine months ended September 30, 2019 and 2018. As of September 30, 2019, the Company had 59,892 performance-based options outstanding. The potential range of shares issuable pursuant to the Company’s outstanding performance-based options range from 0% to 100% of the target shares based on financial measures. Performance-based options vest up to 50% upon achievement of performance condition and up to 50% one year following achievement of the performance condition. Restricted Stock Units On February 28, 2019, as part of the Company’s annual grant of equity, the Company issued 1,384,775 restricted stock units, or RSUs, to employees. In addition, the Company occasionally issues RSUs not in connection with the annual grant process to employees. On September 30, 2019, the Company issued 2,979,400 restricted stock units to employees. RSUs granted by the Company vest in one of the following ways: (i) 100% of each RSU grant vests on either the first or the third anniversary of the grant date, or (ii) one third of each RSU grant vests on the first, second and third anniversaries of the grant date, subject, in each case, to the individual’s continued service through the applicable vesting date, or (iii) 50% of each RSU grant vests on the first anniversary and 25% of each RSU grant vests in 6 months increment after the one year anniversary of the grant 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 recorded approximately $1.2 million and $0.7 million of stock-based compensation expense related to the Akebia employee RSUs during the three months ended September 30, 2019 and 2018, respectively, and approximately $3.3 million and $1.8 million during the nine months ended September 30, 2019 and 2018, respectively. Employee Stock Purchase Plan The first offering period under the ESPP opened on January 2, 2015. The Company issued 87,530 shares during the nine months ended September 30, 2019. The Company recorded approximately $0.1 million and $52,000 of stock-based compensation expense related to the ESPP during the three months ended September 30, 2019 and 2018, respectively, and approximately $0.2 million and $0.2 million during the nine months ended September 30, 2019 and 2018, respectively. Compensation Expense Summary The Company has classified its stock-based compensation expense related to share-based awards as follows: Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 (in thousands) (in thousands) Research and development $ 556 $ 647 $ 2,118 $ 2,090 Selling, general and administrative 2,057 1,605 4,873 4,888 Total $ 2,613 $ 2,252 $ 6,991 $ 6,978 Compensation expense by type of award: Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 (in thousands) (in thousands) Stock options $ 1,305 $ 1,458 $ 3,490 $ 5,074 Restricted stock units 1,217 742 3,318 1,751 Employee stock purchase plan 91 52 183 153 Total $ 2,613 $ 2,252 $ 6,991 $ 6,978

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2019
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes Deferred income taxes reflect the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax basis purposes. When realization of the deferred tax asset is more likely than not to occur, the benefit related to the deductible temporary differences attributable to operations is recognized as a reduction of income tax expense. A valuation allowance is recorded against deferred tax assets if it is more likely than not that some or all of the deferred tax assets will not be realized. The Company cannot be certain that future taxable income will be sufficient to realize its deferred tax assets. Accordingly, the Company has recorded a valuation allowance against the Company’s otherwise recognizable net deferred tax assets. The Company continues to maintain the underlying tax benefits to offset future taxable income and to monitor the need for a valuation allowance based on the profitability of its future operations. As of September 30, 2019 and December 31, 2018, the Company’s net deferred tax liability was $1.8 million and $6.6 million, respectively. Deferred tax liabilities can be reduced by deferred tax assets generated by the Company. During the three and nine months ended September 30, 2019, the Company reduced its net deferred tax liability by a portion of the deferred tax asset associated with the state net operating loss for the period. As a result, the Company reported a $1.3 million and $4.9 million tax benefit for the three and nine months ended September 30, 2019, respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	15. 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 April 2018, 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 12 th Additionally, as a result of the Merger, the Company now has a lease for 27,300 square feet of office space in Boston, Massachusetts, or the Boston Lease, which expires in February 2023. The total monthly lease payments under the base rent are approximately $136,000 and are subject to annual rent escalations. 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 Cambridge Lease with respect to the lab space expires on November 30, 2021, with an extension option for one additional period of two years. The term of the Boston Lease office space expires on February 28, 2023, with an extension option for one additional five year extension option available. The renewal options in the Company’s 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 lease agreements do not contain residual value guarantees. Operating lease costs for the three and nine months ended September 30, 2019 were $1.7 million and $5.0 million, respectively, and cash paid for amounts included in the measurement of operating lease liabilities for the three and nine months ended September 30, 2019 were $1.7 million and $5.2 million, 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 Company has not entered into any material short-term leases or financing leases as of September 30, 2019. The total security deposit in connection with the Cambridge Lease is $1.6 million as of September 30, 2019. Additionally, the Company recorded $0.8 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 in prepaid expenses and other current assets and in other assets in the Company’s consolidated balance sheets as of September 30, 2019. As of September 30, 2019, undiscounted minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter are as follows: Operating Leases (in thousands) Remaining 2019 $ 1,296 2020 7,008 2021 7,064 2022 6,735 2023 5,347 Thereafter 13,934 Total $ 41,384 In arriving at the operating lease liabilities, the Company applied incremental borrowing rates ranging from 5.91% to 6.94%, which were based on the remaining lease term at the date of adoption of ASC 842. As of September 30, 2019, the remaining lease terms ranged from 2.17 years to 6.95 years. As of September 30, 2019, the following represents the difference between the remaining undiscounted minimum rental commitments under non-cancelable leases and the operating lease liabilities: Operating Leases (in thousands) Total Undiscounted minimum rental commitments $ 41,384 Present value adjustment using incremental borrowing rate (7,689 ) Operating lease liabilities $ 33,695 At December 31, 2018, the Company’s future minimum payments required under these leases are as follows: Operating Lease (in thousands) 2019 $ 6,777 2020 7,008 2021 7,064 2022 6,735 2023 5,347 Thereafter 13,934 Total $ 46,865 Manufacturing Agreements As part of the Merger, the Company retained Keryx’s commercial supply agreements with BioVectra and Siegfried Evionnaz SA, or Siegfried, to supply commercial drug substance for Auryxia. Pursuant to the BioVectra Manufacture and Supply Agreement and the Product Manufacture and Supply and Facility Construction Agreement, collectively the BioVectra 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. In addition, the BioVectra Agreement contained contingent milestone payments for capital developments in connection with construction of an expansion of the site of the BioVectra production facility for the manufacture of drug substance for Auryxia. These milestone payments were achieved by BioVectra and fully recorded prior to the Merger. These milestone payments are recorded in other assets and amortized into drug substance as inventory is released to the Company. The term of the BioVectra Agreement expires in late 2026, after which, it automatically renews for specified terms until terminated. The Company may terminate the BioVectra Agreement prior to the expiration of the contract term, which could result in early termination fee. As of September 30, 2019, the Company is required to purchase a minimum quantity of drug substance for Auryxia annually at a total cost of approximately $135.7 million through the end of the contract term. As part of purchase accounting, the Company identified an executory contract in the BioVectra Agreement, which includes future firm purchase commitments. This executory contract was deemed to have an off-market element related to the amount of purchase commitments that exceed the current forecast. As a result, the Company recorded a liability of $29.5 million in purchase accounting, as of the acquisition date for the preliminary fair value of the off-market element. Through September 30, 2019, the Company recorded $0.5 million in accretion expense related to the present value discount associated with this liability. Pursuant to the Siegfried Master Manufacturing Services and Supply Agreement, 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, 2021, after which, it automatically renews for one-year terms until terminated. The Siegfried Agreement provides for certain termination rights prior to December 31, 2021 for the Company. As of September 30, 2019, the Company is required to purchase a minimum quantity of drug substance for Auryxia annually at a total cost of approximately $66.3 million through the year ending December 31, 2021. Other Third Party Contracts Under the Company’s agreement with IQVIA, formerly known as Quintiles IMS, to provide contract research organization services for the PRO 2 2

Net Loss per Share

Net Loss per Share	9 Months Ended
	Sep. 30, 2019
Earnings Per Share [Abstract]
Net Loss per Share	16. Net Loss per Share The shares in the table below were excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, due to their anti-dilutive effect: As of September 30, 2019 2018 Warrant 509,611 509,611 Outstanding stock options 7,808,382 3,957,940 Unvested restricted stock units 4,810,417 893,850 Total 13,128,410 5,361,401

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
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 U.S. GAAP for complete financial statements. Any reference in these notes to applicable guidance is meant to refer to the authoritative U.S. GAAP as found in the Accounting Standards Codification, or 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 nine months ended September 30, 2019 are not necessarily indicative of the results that may be expected for the fiscal year ending December 31, 2019 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, 2018 filed with the U.S. Securities and Exchange Commission on March 26, 2019, or the 2018 Annual Report on Form 10-K. The significant accounting policies used in preparation of these unaudited condensed consolidated financial statements for the three and nine months ended September 30, 2019 are consistent with those discussed in Note 2 to the consolidated financial statements in the Company’s 2018 Annual Report on Form 10-K and are updated below as necessary.
New Accounting Pronouncements	New Accounting Pronouncements – Recently Adopted In February 2016, the FASB issued ASU 2016-02, Leases • The Company elected the package of transition practical expedients, which allows it to retain the lease classification and initial direct costs for any leases that existed prior to the adoption of this new standard. • The Company will not reassess whether any contracts completed prior to the adoption are leases. The Company adopted ASC 842 using the modified retrospective approach, as of January 1, 2019, with no restatements of prior periods or a cumulative effect of the adoption of ASC 842 in retained earnings. On January 1, 2019, the Company recognized additional operating lease liabilities, net of deferred rent, of approximately $37.1 million based on the present value of the remaining minimum lease payments, a corresponding right of use assets of approximately $33.4 million, and $0.9 million to prepaid expenses and other current assets related to leasehold improvement allowances that had yet to be incurred as of the date of adoption, but for which the Company was reasonably certain to incur costs at least equal to the maximum level of leasehold improvement allowance. The adoption of ASC 842 did not have an impact on the Company’s unaudited condensed consolidated statement of operations. Prior periods are presented in accordance with ASC 840, Leases The Company made an accounting policy election not to recognize leases with an initial term of 12 months or less within its unaudited condensed consolidated balance sheets and to recognize those lease payments on a straight-line bases in its unaudited condensed consolidated statements of operations. The Company also made the accounting policy election not to separate the non-lease components from the lease components for its building leases and, rather, account for each non-lease component and lease component as a single component. The Company determines if an arrangement is a lease at inception. An arrangement is determined to contain a lease if the contract conveys the right to control the use of an identified property, plant, or equipment for a period of time in exchange for consideration. If the Company can benefit from the various underlying assets of a lease on their own or together with other resources that are readily available, or if the various underlying assets are neither highly dependent on nor highly interrelated with other underlying assets in the arrangement, they are considered to be a separate lease component. In the event multiple underlying assets are identified, the lease consideration is allocated to the various components based on each of the component’s relative fair value. Operating lease assets represent the Company’s right to use an underlying asset for the lease term and operating lease liabilities represent its obligation to make lease payments arising from the leasing arrangement. Operating lease assets and operating lease liabilities are recognized at the commencement date based on the present value of lease payments over the lease term. The Company uses the implicit rate when readily determinable and uses an estimate of its incremental borrowing rate when the implicit rate is not readily determinable based upon the available information at the commencement date of lease inception. The incremental borrowing rate is determined using a credit rating scoring model to estimate the Company’s credit rating, adjusted for collateralization. The calculation of the operating lease assets includes any lease payments made and excludes any lease incentives. The Company’s lease terms may include options to extend or terminate the lease when it is reasonably certain that the Company will exercise that option. The Company’s operating leases are reflected in prepaid expenses and other current assets, operating lease assets, accrued expenses and operating lease liabilities, net of current portion in its condensed consolidated balance sheets. Lease expense for minimum lease payments is recognized on a straight-line basis over the lease term. In January 2017, the FASB issued ASU 2017-04, Intangibles-Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment , which simplifies how companies calculate goodwill impairments by eliminating Step 2 of the impairment test. Step 2 measures a goodwill impairment loss by comparing the implied fair value of a reporting unit’s goodwill with the carrying amount of that goodwill. ASU 2017-04 requires companies to compare the fair value of a reporting unit to its carrying amount and recognize an impairment charge for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to the related reporting unit. This ASU is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal year 2020. Early adoption is allowed, and the Company adopted ASU 2017-04 in the first quarter of fiscal year 2019. The Company will conduct its initial goodwill impairment test as of October 1, 2019 and annually thereafter, or more frequently if indicators of impairment are present or changes in circumstances suggest that an impairment may exist. Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments , which requires that financial assets measured at amortized cost be presented at the net amount expected to be collected. Currently, U.S. GAAP delays recognition of the full amount of credit losses until the loss is probable of occurring. Under this ASU, the income statement will reflect an entity’s current estimate of all expected credit losses. The measurement of expected credit losses will be based upon historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. Credit losses relating to available-for-sale debt securities will be recorded through an allowance for credit losses rather than as a direct write-down of the security. Additionally, credit losses for trade receivables will be also be recorded through an allowance that reflects the Company’s current estimate of credit losses expected to be incurred. This ASU is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal year 2020. Early adoption is permitted. The Company is currently evaluating the impact of the adoption of ASU 2016-13 on its consolidated financial position and results of operations. Based on the composition of the Company’s available-for-sale debt securities, trade receivables, and other financial assets, and also taking into account current market conditions and historical credit loss activity, the Company does not expect that the adoption of this standard will have a material impact on the Company’s consolidated financial statements and related disclosures. In 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement This ASU is effective for annual periods beginning after December 15, 2019, and is applicable to the Company in fiscal year 2020. The Company is currently evaluating the impact the adoption of the standard will have on its condensed consolidated financial statements and related disclosures.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and 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, other non-current liabilities, stock-based compensation expense, product and collaboration revenues including various rebates and reserves related to product sales, inventories, income taxes, intangible assets and goodwill.
Cash, Cash Equivalents, and Restricted Cash	Cash, Cash Equivalents, and Restricted Cash Cash and cash equivalents consist of all cash on hand, deposits and funds invested in available-for-sale securities with original maturities of three months or less at the time of purchase. At September 30, 2019, the Company’s cash is primarily in money market funds. The Company may maintain balances with its banks in excess of federally insured limits. Restricted cash represents amounts required for security deposits under the Company’s office and lab space lease agreements and cash balances held as collateral for the Company’s employee credit card program. Restricted cash is included in “prepaid expenses and other current assets” and “other assets” in the unaudited condensed consolidated balance sheets. The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported in the unaudited condensed consolidated balance sheet that sum to the total of the amounts reported in the unaudited condensed consolidated statement of cash flows (in thousands): September 30, 2019 September 30, 2018 Cash and cash equivalents $ 122,886 $ 162,430 Prepaid expenses and other current assets 263 — Other assets 2,092 1,566 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows $ 125,241 $ 163,996
Investments	Investments Management determines the appropriate classification of securities at the time of purchase and reevaluates such designation as of each balance sheet date of
Property and Equipment	Property and Equipment Property and equipment is stated at cost, less accumulated depreciation. Assets under capital lease are included in property and equipment. Property and equipment is depreciated using the straight-line method over the estimated useful lives of the assets, generally three to seven years. Such costs are periodically reviewed for recoverability when impairment indicators are present. Such indicators include, among other factors, operating losses, unused capacity, market value declines and technological obsolescence. Recorded values of asset groups of equipment that are not expected to be recovered through undiscounted future net cash flows are written down to current fair value, which generally is determined from estimated discounted future net cash flows (assets held for use) or net realizable value (assets held for sale). The following is the summary of property and equipment and related accumulated depreciation as of September 30, 2019 and December 31, 2018. Useful Life September 30, 2019 December 31, 2018 (in thousands) Computer equipment and software 3 $ 1,010 $ 1,593 Furniture and fixtures 5 - 7 2,086 1,170 Equipment 7 2,451 1,780 Leasehold improvements Shorter of the useful life or remaining lease term (10 years) 10,869 5,324 Office equipment under capital lease 3 — 114 16,416 9,981 Less accumulated depreciation (3,617 ) (1,958 ) Net property and equipment $ 12,799 $ 8,023 Depreciation expense was approximately $0.6 million and $0.2 million for the three months ended September 30, 2019 and 2018, respectively, and approximately $1.7 million and $0.6 million for the nine months ended September 30, 2019 and 2018, respectively.
Inventories	Inventory The Company values its inventories at the lower-of-cost or net realizable value. The Company determines the cost of its inventories, which includes amounts related to materials and manufacturing overhead, on a first-in, first-out basis. The Company classifies its inventory costs as long-term, in other assets in its unaudited condensed consolidated balance sheets, when it expects to utilize the inventory beyond their normal operating cycle. Prior to the regulatory approval of its product candidates, the Company incurs expenses for the manufacture of material that could potentially be available to support the commercial launch of its products. Until the first reporting period when regulatory approval has been received or is otherwise considered probable and the future economic benefit is expected to be realized, the Company records all such costs as research and development expense. Inventory used in clinical trials is also expensed as research and development expense, when selected for such use. Inventory that can be used in either the production of clinical or commercial products is expensed as research and development costs when identified for use in a clinical manufacturing campaign. The Company performs an assessment of the recoverability of capitalized inventory during each reporting period, and writes down any excess and obsolete inventory to its net realizable value in the period in which the impairment is first identified. Such impairment charges, should they occur, are recorded as a component of cost of product sales in the unaudited condensed consolidated statements of operations and comprehensive loss. The determination of whether inventory costs will be realizable requires the use of estimates by management. If actual market conditions are less favorable than projected by management, additional write-downs of inventory may be required. Additionally, the Company’s product is subject to strict quality control and monitoring throughout the manufacturing process. In the event that certain batches or units of product no longer meet quality specifications, the Company will record a charge to cost of product sales to write-down any unmarketable inventory to its estimated net realizable value. In all cases, product inventory is carried at the lower of cost or its estimated net realizable value.
Revenue Recognition	Revenue Recognition The Company generates revenues primarily from sales of Auryxia, see Note 3, and from its collaborations with MTPC and Otsuka, see Note 4. The Company recognizes revenue in accordance with ASC 606, which applies to all contracts with customers, except for contracts that are within the scope of other standards. Under ASC 606, the Company recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration which the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of ASC 606, it performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of ASC 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. Product Revenue, Net The Company sells Auryxia in the U.S. primarily to wholesale distributors as well as certain specialty pharmacy providers, collectively, Customers. These Customers resell the Company’s product to health care providers and patients. In addition to distribution agreements with Customers, the Company enters into arrangements with health care providers and payors that provide for government-mandated and/or privately-negotiated rebates, chargebacks, and discounts with respect to the purchase of the Company’s product. The Company recognizes revenue on product sales when the Customer obtains control of the Company’s product, which occurs at a point in time, typically upon delivery to the Customer. The Company expenses incremental costs of obtaining a contract as and when incurred if the expected amortization period of the asset that it would have recognized is one year or less. Reserves for Variable Consideration Revenue from product sales is recorded at the net sales price (transaction price), which includes estimates of variable consideration for which reserves are established and which result from discounts, returns, chargebacks, rebates, co-pay assistance and other allowances that are offered within contracts between the Company and its Customers, health care providers, payors and other indirect customers relating to the Company’s sales of its products. These reserves are based on the amounts earned or to be claimed on the related sales and are classified as reductions of accounts receivable (if the amount will be credited to the Customer) or as a current liability (if the amount is payable to a Customer or a party other than a Customer). When appropriate, t The amount of variable consideration that is included in the transaction price may be constrained, and is included in the net sales price only to the extent that it is probable that a significant reversal in the amount of the cumulative revenue recognized will not occur in a future period. Actual amounts of consideration ultimately received may differ from the Company’s estimates. If actual results in the future vary from the Company’s estimates, the Company will adjust these estimates, which would affect net product revenue and earnings in the period such variances become known. Trade Discounts and Allowances: The Company generally provides Customers with discounts that include incentive fees that are explicitly stated in the Company’s contracts and are recorded as a reduction of revenue in the period the related product revenue is recognized. In addition, the Company compensates (through trade discounts and allowances) its Customers for sales order management, data, and distribution services. However, the Company has determined such services received to date are not distinct from the Company’s sale of products to the Customer and, therefore, these payments have been recorded as a reduction of revenue within the unaudited condensed consolidated statement of operations and comprehensive loss through September 30, 2019. The Company records a corresponding reduction of accounts receivable (if the trade discount and/or allowance will be credited to the Customer) or an increase in accrued expense (if the trade discount and/or allowance is payable to a Customer) on the consolidated balance sheets. Product Returns: Consistent with industry practice, the Company generally offers Customers a limited right of return which allows for the product to be returned when the product expiry is within an allowable window. This right of return lapses once the product is provided to a patient. The Company estimates the amount of its product sales that may be returned by its Customers and records this estimate as a reduction of revenue in the period the related product revenue is recognized. The Company currently estimates product return reserve using available industry data and its own historical sales information, including its visibility into the inventory remaining in the distribution channel. Provider Chargebacks and Discounts : Chargebacks for fees and discounts to providers represent the estimated obligations resulting from contractual commitments to sell products to qualified healthcare providers at prices lower than the list prices charged to Customers who directly purchase the product from the Company. Customers charge the Company for the difference between what they pay for the product and the ultimate selling price to the qualified healthcare providers. These reserves are established in the same period that the related revenue is recognized, resulting in a reduction of product revenue and accounts receivable. Chargeback amounts are generally determined at the time of resale to the qualified healthcare provider by Customers, and the Company generally issues credits for such amounts within a few weeks of the Customer’s resale of the product. Reserves for chargebacks consist of credits that the Company expects to issue for units that remain in the distribution channel at each reporting period end that the Company expects will be sold to qualified healthcare providers, and chargebacks that Customers have claimed but for which the Company has not yet issued a credit. Commercial and Medicare Part D Rebates: The Company contracts with various commercial payor organizations, primarily health insurance companies and pharmacy benefit managers, for the payment of rebates with respect to utilization of its products. The Company estimates the rebates for commercial and Medicare Part D payors based upon (i) its contracts with the payors and (ii) information obtained from its Customers and other third parties regarding the payor mix for Auryxia. The Company estimates these rebates and records such estimates in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability. Other Government Rebates: The Company is subject to discount obligations under state Medicaid programs and other government programs. The Company estimates its Medicaid and other government programs rebates based upon a range of possible outcomes that are probability-weighted for the estimated payor mix. These reserves are recorded in the same period the related revenue is recognized, resulting in a reduction of product revenue and the establishment of a current liability which is included in accrued expenses and other current liabilities on the consolidated balance sheets. For Medicare, the Company also estimates the number of patients in the prescription drug coverage gap for whom the Company will owe an additional liability under the Medicare Part D program. The Company’s liability for these rebates consists of invoices received for claims from prior quarters that have not been paid or for which an invoice has not yet been received, estimates of claims for the current quarter, and estimated future claims that will be made for product that has been recognized as revenue, but which remains in the distribution channel at the end of each reporting period. Other Incentives: Other incentives that the Company offers include voluntary patient assistance programs such as the Company’s co-pay assistance program, which are intended to provide financial assistance to qualified commercially insured patients with prescription drug co-payments required by payors. The calculation of the accrual for co-pay assistance is based on actual claims processed during a given period, as well as historical utilization data to estimate the amount the Company expects to receive associated with product that has been recognized as revenue, but remains in in the distribution channel at the end of each reporting period. Collaboration Revenues The Company enters into out-license and collaboration agreements which are within the scope of ASC 606, under which it licenses certain rights to its product candidates to third parties. The terms of these arrangements typically include payment to the Company of one or more of the following: non-refundable, up-front license fees; development, regulatory, and commercial milestone payments; payments for manufacturing supply services the Company provides through its contract manufacturers; and royalties on net sales of licensed products. Each of these payments may result in license, collaboration and other revenue, except for revenues from royalties on net sales of licensed products, which are classified as royalty revenues. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under each of its agreements, the Company implements the five-step model noted above. As part of the accounting for these arrangements, the Company must develop assumptions that require judgment to determine whether the individual promises should be accounted for as separate performance obligations or as a combined performance obligation, and to determine the stand-alone selling price for each performance obligation identified in the contract. A deliverable represents a separate performance obligation if both of the following criteria are met: (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available to the customer, and (ii) the entity’s promise to transfer the good or service to the customer is separately identifiable from other promises in the contract. The Company uses key assumptions to determine the stand-alone selling price, which may include forecasted revenues, development timelines, reimbursement rates for personnel costs, discount rates, and probabilities of technical and regulatory success. With regard to the MTPC and Otsuka Agreements (each as defined in Note 4), the Company recognizes revenue related to amounts allocated to the identified performance obligation on a proportional performance basis as the underlying services are performed. Licenses of Intellectual Property If the license to the Company’s intellectual property is determined to be distinct from the other performance obligations identified in the arrangement, the Company recognizes revenue from non-refundable, up-front fees allocated to the license when the license is transferred to the customer and the customer is able to use and benefit from the license. For licenses that are bundled with other promises, the Company utilizes judgment to assess the nature of the combined performance obligation to determine whether the combined performance obligation is satisfied over time or at a point in time and, if over time, the appropriate method of measuring progress for purposes of recognizing revenue from non-refundable, up-front fees. The Company evaluates the measure of progress each reporting period and, if necessary, adjust the measure of performance and related revenue recognition. Milestone Payments At the inception of each arrangement that includes development milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. The Company evaluates factors such as the scientific, clinical, regulatory, commercial, and other risks that must be overcome to assess the milestone as probable of being achieved. There is considerable judgment involved in determining whether a milestone is probable of being reached at each specific reporting period. Milestone payments that are not within the control of the Company or the customer, such as regulatory approvals, are not considered probable of being achieved until those approvals are received. If it is probable that a significant revenue reversal would not occur, the associated milestone value is included in the transaction price. The transaction price is then allocated to each performance obligation on a relative stand-alone selling price basis, for which the Company recognizes revenues as, or when, the performance obligations under the contract are satisfied. At the end of each subsequent reporting period, the Company re-evaluates the probability of achievement of such development milestones and any related constraint, and if necessary, adjusts its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect collaboration revenue in the period of adjustment. Manufacturing Supply Services Arrangements that include a promise for future supply of drug substance or drug product for either clinical development or commercial supply at the licensee’s discretion are generally considered as options. The Company assesses if these options provide a material right to the licensee and if so, they are accounted for as separate performance obligations. If the Company is entitled to additional payments when the licensee exercises these options, any additional payments are recorded in license, collaboration and other revenues when the licensee obtains control of the goods, which is upon delivery. Royalties The Company will recognize sales-based royalties, including milestone payments based on the level of sales, at the later of (i) when the related sales occur, or (ii) when the performance obligation to which some or all of the royalty has been allocated has been satisfied (or partially satisfied). The Company receives royalty payments from JT and Torii, based on net sales of Riona in Japan. Collaborative Arrangements The Company records the elements of its collaboration agreements that represent joint operating activities in accordance with ASC Topic 808, Collaborative Arrangements Revenue from Contracts with Customers – Scope and Scope Exceptions During the three months ended September 30, 2019 and 2018, the Company incurred approximately $0.5 million and $0.2 million, respectively, of costs related to the cost-sharing provisions of the Otsuka U.S. Agreement, as defined below in Note 4, of which approximately $0.2 million and $0.1 million are reimbursable by Otsuka and recorded as a reduction to research and development expense during the three months ended September 30, 2019 and 2018, respectively.
Intangible Assets	Intangible The Company maintains a definite-lived intangible asset related to developed product rights for Auryxia, which was acquired on December 12, 2018 as part of the Merger. Intangible assets are initially recorded at fair value and stated net of accumulated amortization and impairments. The Company amortizes its intangible assets that have finite lives using either the straight-line method, or if reliably determinable, based on the pattern in which the economic benefit of the asset is expected to be utilized. Amortization for the Company’s intangible asset is recorded over its estimated useful life of nine years. The Company reviews intangible assets subject to amortization to determine if any adverse conditions exist or a change in circumstances has occurred that would indicate impairment or a change in the remaining useful life. If an impairment indicator exists, the Company performs a recoverability test by comparing the sum of the estimated undiscounted cash flows of the intangible asset and asset group to its carrying value on the unaudited condensed consolidated balance sheet. If the carrying value of the intangible asset exceeds the undiscounted cash flows used in the recoverability test, the Company will write the carrying value down to the fair value in the period identified. The Company calculates the fair value of intangible assets as the present value of estimated future cash flows expected to be generated from the intangible asset using a risk-adjusted discount rate. In determining estimated future cash flows associated with its intangible assets, the Company uses market participant assumptions pursuant to ASC Topic 820, Fair Value Measurements and Disclosures
Fair Value of Financial Instruments	Fair Value of Financial Instruments The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values. ASC 820 establishes a hierarchy of inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing the asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing the asset or liability, and are developed based on the best information available in the circumstances. The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments, and is not a measure of the investment credit quality. The three levels of the fair value hierarchy are described below: • Level 1 – Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. • Level 2 – Valuations based on quoted prices for similar assets or liabilities in markets that are not active, or for which all significant inputs are observable, either directly or indirectly. • Level 3 – Valuations that require inputs that reflect the Company’s own assumptions that are both significant to the fair value measurement and unobservable. To the extent that valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. Accordingly, the degree of judgment exercised by the Company in determining fair value is greatest for instruments categorized in Level 3. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. Items measured at fair value on a recurring basis include available for sale securities (see Note 7). The carrying amounts of prepaid expenses and other current assets, accounts payable and accrued expenses approximate their fair values due to their short-term maturities. Items measured at fair value on a nonrecurring basis include property and equipment, intangible assets and goodwill. The Company remeasures the fair value of these assets upon the occurrence of certain events. There were no such remeasurements to property and equipment for the three and nine months ended September 30, 2019. There were no impairments to assets measured using Level 3 inputs during the three and nine months ended September 30, 2019 and 2018, respectively.
Net Loss per Share	Net Loss per Share Basic net loss per share is calculated by dividing net loss by the weighted-average shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share is calculated by adjusting weighted-average shares outstanding for the dilutive effect of common stock equivalents outstanding for the period, determined using the treasury-stock method. For purposes of the diluted net loss per share calculation, preferred stock, stock options, warrants, restricted stock and RSUs are considered to be common stock equivalents, but have been excluded from the calculation of diluted net loss per share, as their effect would be anti-dilutive for all periods presented. Therefore, basic and diluted net loss per share were the same for all periods presented. Diluted net income per share is calculated by dividing the net income by the weighted-average common shares outstanding for the period, including any dilutive effect from outstanding options, warrants, restricted stock and RSUs using the treasury stock method.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Reconciliation of Cash, Cash Equivalents, and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported in the unaudited condensed consolidated balance sheet that sum to the total of the amounts reported in the unaudited condensed consolidated statement of cash flows (in thousands): September 30, 2019 September 30, 2018 Cash and cash equivalents $ 122,886 $ 162,430 Prepaid expenses and other current assets 263 — Other assets 2,092 1,566 Total cash, cash equivalents, and restricted cash shown in the statement of cash flows $ 125,241 $ 163,996
Summary of Property and Equipment and Related Accumulated Depreciation	The following is the summary of property and equipment and related accumulated depreciation as of September 30, 2019 and December 31, 2018. Useful Life September 30, 2019 December 31, 2018 (in thousands) Computer equipment and software 3 $ 1,010 $ 1,593 Furniture and fixtures 5 - 7 2,086 1,170 Equipment 7 2,451 1,780 Leasehold improvements Shorter of the useful life or remaining lease term (10 years) 10,869 5,324 Office equipment under capital lease 3 — 114 16,416 9,981 Less accumulated depreciation (3,617 ) (1,958 ) Net property and equipment $ 12,799 $ 8,023

Product Revenue and Reserves _2

Product Revenue and Reserves for Variable Consideration (Tables)	9 Months Ended
	Sep. 30, 2019
Revenue From Contract With Customer [Abstract]
Summary of Product Revenue Allowance and Reserve Categories	The following table summarizes activity in each of the product revenue allowance and reserve categories for the nine months ended September 30, 2019 (in thousands): Chargebacks and Discounts Rebates, Fees and other Deductions Returns Total Balance at December 31, 2018 $ 516 $ 22,861 $ 360 $ 23,737 Current provisions related to sales in current year 5,617 73,424 1,835 80,876 Adjustments related to prior period sales 13 1,507 — 1,520 Credits/payments made relating to sales in current year (4,108 ) (21,087 ) — (25,195 ) Credits/payments made relating to prior period sales (1,373 ) (46,803 ) (1,907 ) (50,083 ) Balance at September 30, 2019 $ 665 $ 29,902 $ 288 $ 30,855

License, Collaboration and Ot_2

License, Collaboration and Other Significant Agreements (Tables)	9 Months Ended
	Sep. 30, 2019
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Revenues Recognized From License, Collaboration and Other Significant Agreements	During the three and nine months ended September 30, 2019 and 2018, the Company recognized the following revenues from its license, collaboration and other significant agreements and had the following deferred revenue balances as of September 30, 2019: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 License, Collaboration and Other Revenue: (in thousands) (in thousands) MTPC Agreement $ — $ — $ 10,000 $ 9,281 Otsuka U.S. Agreement 39,718 29,030 103,461 75,086 Otsuka International Agreement 20,220 24,114 64,643 63,176 Total Proportional Performance Revenue $ 59,938 $ 53,144 $ 178,104 $ 147,543 JT and Torii 1,549 — 4,266 — MTPC Stability Studies 486 25 872 349 Total License, Collaboration and Other Revenue $ 61,973 $ 53,169 $ 183,242 $ 147,892
Deferred Revenues Balance	During the three and nine months ended September 30, 2019 and 2018, the Company recognized the following revenues from its license, collaboration and other significant agreements and had the following deferred revenue balances as of September 30, 2019: September 30, 2019 Short-Term Long-Term Total Deferred Revenue: (in thousands) Otsuka U.S. Agreement $ 18,873 $ 28,576 $ 47,449 Otsuka International Agreement 13,269 10,632 23,901 Vifor Agreement — 4,679 4,679 Total $ 32,142 $ 43,887 $ 76,029
Schedule of Changes in Contract Assets and Liabilities	The following table presents changes in the Company’s contract assets and liabilities during the nine months ended September 30, 2019 and 2018 (in thousands): Nine Months Ended September 30, 2019 Balance at Beginning of Period Additions Deductions Balance at End of Period Contract assets: Other current assets $ — $ 10,000 $ (10,000 ) $ — Accounts receivable ( 1) $ 1,587 $ 134,268 $ (131,651 ) $ 4,204 Contract liabilities: Deferred revenue $ 112,689 $ 131,444 $ (168,104 ) $ 76,029 Accounts payable $ 13,492 $ — $ (13,492 ) $ — Nine Months Ended September 30, 2018 Contract assets: Other current assets $ — $ 531 $ (531 ) $ — Accounts receivable ( 1) $ 34,186 $ 120,283 $ (153,938 ) $ 531 Contract liabilities: Deferred revenue $ 179,624 $ 119,442 $ (147,543 ) $ 151,523 Accounts payable $ — $ 4,427 $ (1,040 ) $ 3,387 (1)
Schedule of Revenue Recognized Resulting from Changes in Contract Asset and Contract Liability	During the three and nine months ended September 30, 2019 and 2018, 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 September 30, Nine Months Ended September 30, Revenue Recognized in the Period from: 2019 2018 2019 2018 Amounts included in deferred revenue at the beginning of the period $ 27,095 $ 53,144 $ 60,441 $ 110,974 Performance obligations satisfied in previous periods $ — $ — $ 1,254 $ 6,813

Business Combination (Tables)

Business Combination (Tables)	9 Months Ended
	Sep. 30, 2019
Business Combinations [Abstract]
Summary of Total Fair Value Consideration	Pursuant to the terms and conditions of the Merger Agreement, e ach outstanding Keryx Share, excluding the Baupost Additional Shares, as defined below, and each outstanding Keryx equity award were converted into Akebia Shares and substantially similar Akebia equity awards, respectively, at an exchange ratio of 0.37433 for a t Fair value of 57,773,090 Akebia Shares $ 516,492 Fair value of 602,752 Akebia RSUs 304 Fair value of 3,967,290 Akebia stock options 10,958 Total consideration $ 527,754
Summary of Purchase Price of Identifiable Assets Acquired and Liabilities Assumed	The Company has allocated the $527.8 million purchase price to the identifiable assets acquired and liabilities assumed in the business combination at their fair values as of December 12, 2018 as follows Cash and cash equivalents $ 5,257 Inventory 235,597 Trade accounts receivable, net 15,834 Prepaid expenses and other current assets 8,399 Goodwill 55,053 Intangible assets: Developed product rights for Auryxia 329,130 Other intangible assets 545 Property and equipment, net 3,646 Other assets 14,441 Accounts payable (17,570 ) Accrued expenses (42,972 ) Deferred tax liability (35,096 ) Debt (15,000 ) Fair value of unfavorable executory contract (29,510 ) Total purchase price $ 527,754

Available for Sale Securities (

Available for Sale Securities (Tables)	9 Months Ended
	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Summary of Available for Sale Securities at Fair Value	Available for sale securities at September 30, 2019 and December 31, 2018 consisted of the following : Gross Gross Unrealized Unrealized Amortized Cost Gains Losses Fair Value (in thousands) September 30, 2019 Cash and cash equivalents $ 122,886 $ — $ — $ 122,886 Available for sale securities: Certificates of deposit $ 245 $ — $ — $ 245 U.S. government debt securities 22,476 6 — 22,482 Total available for sale securities $ 22,721 $ 6 $ — $ 22,727 Total cash, cash equivalents, and available for sale securities $ 145,607 $ 6 $ — $ 145,613 Gross Gross Unrealized Unrealized Amortized Cost Gains Losses Fair Value (in thousands) December 31, 2018 Cash and cash equivalents $ 104,644 $ — $ — $ 104,644 Available for sale securities: Certificates of deposit $ 245 — — $ 245 U.S. government debt securities 158,518 1 (198 ) 158,321 Corporate debt securities 58,494 — (64 ) 58,430 Total available for sale securities $ 217,257 $ 1 $ (262 ) $ 216,996 Total cash, cash equivalents, and available for sale securities $ 321,901 $ 1 $ (262 ) $ 321,640
Estimated Fair Value of Available for Sale Securities by Contractual Maturity	The estimated fair value of the Company’s available for sale securities balance at September 30, 2019, by contractual maturity, was as follows: Due in one year or less $ 22,727 Due after one year — Total available for sale securities $ 22,727
Summary of Available for Sale Securities that were in Continuous Unrealized Loss Position	The following table summarizes the Company’s available for sale securities that were in a continuous unrealized loss position, but were not deemed to be other-than temporarily impaired, as of December 31, 2018: Unrealized Loss for Less Than 12 Months Unrealized Loss for 12 Months or More Total Gross Gross Gross Unrealized Estimated Unrealized Estimated Unrealized Estimated Losses Fair Value Losses Fair Value Losses Fair Value (in thousands) December 31, 2018 Available for sale securities: U.S. government debt securities $ (159 ) $ 116,026 $ (39 ) $ 29,934 $ (198 ) $ 145,960 Corporate debt securities (64 ) 58,430 — — (64 ) 58,430 Total $ (223 ) $ 174,456 $ (39 ) $ 29,934 $ (262 ) $ 204,390

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
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 September 30, 2019 and December 31, 2018 are summarized below: Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) September 30, 2019 Assets: Cash and cash equivalents $ 122,886 $ — $ — $ 122,886 Certificates of deposit — 245 — 245 U.S. government debt securities — 22,482 — 22,482 $ 122,886 $ 22,727 $ — $ 145,613 Fair Value Measurements Using Level 1 Level 2 Level 3 Total (in thousands) December 31, 2018 Assets: Cash and cash equivalents $ 104,644 $ — $ — $ 104,644 Certificates of deposit — 245 — 245 U.S. government debt securities — 158,321 — 158,321 Corporate debt securities — 58,430 — 58,430 $ 104,644 $ 216,996 $ — $ 321,640

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2019
Inventory Disclosure [Abstract]
Components of Inventory	The components of inventory are summarized as follows: September 30, 2019 December 31, 2018 (in thousands) Raw materials $ 2,824 $ 1,880 Work in process 152,208 215,122 Finished goods 45,863 18,182 Total inventory $ 200,895 $ 235,184 Long-term inventory, which primarily consists of raw materials and work in process, is included in other assets in the Company’s consolidated balance sheets. September 30, 2019 December 31, 2018 (in thousands) Balance Sheet Classification: Inventory $ 115,987 $ 114,245 Other assets 84,908 120,939 Total inventory $ 200,895 $ 235,184

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Tables)	9 Months Ended
	Sep. 30, 2019
Goodwill And Intangible Assets Disclosure [Abstract]
Summary of Intangible Assets	The following table presents the Company’s intangible assets at September 30, 2019 and December 31, 2018 (in thousands): September 30, 2019 Gross Carrying Value Accumulated Amortization ASC 842 Adjustment Total Estimated useful life Acquired intangible assets: Developed product rights for Auryxia $ 329,130 $ (28,818 ) $ — $ 300,312 9 Years Favorable lease 545 (5 ) (540 ) — N/A Total $ 329,675 $ (28,823 ) $ (540 ) $ 300,312 December 31, 2018 Gross Carrying Value Accumulated Amortization Total Estimated useful life Acquired intangible assets: Developed product rights for Auryxia $ 329,130 $ (1,517 ) $ 327,613 9 Years Favorable lease 545 (5 ) 540 4 Years Total $ 329,675 $ (1,522 ) $ 328,153
Schedule of Estimated Future Amortization Expense for Intangible Assets	Estimated future amortization expense for the intangible asset as of September 30, 2019 is as follows (in thousands): Total 2019 $ 9,100 2020 36,402 2021 36,401 2022 36,402 2023 36,401 Thereafter 145,606 $ 300,312
Schedule of Goodwill	Goodwill was $55.1 million as of September 30, 2019 and December 31, 2018, derived as follows (in thousands): Total Merger consideration $ 527,754 Less: Fair value of identified acquired assets and liabilities, net (472,701 ) Goodwill $ 55,053

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2019
Payables And Accruals [Abstract]
Components of Accrued Expenses	Accrued expenses as of September 30, 2019 and December 31, 2018 are as follows: September 30, 2019 December 31, 2018 (in thousands) Accrued clinical expenses $ 66,194 $ 71,881 Product revenue allowances 28,408 22,861 Accrued bonus 7,740 9,537 Lease liability 4,884 — Accrued commercial manufacturing 3,352 6,383 Royalties 2,697 2,430 Professional fees 2,393 2,367 Accrued payroll 1,208 2,255 Accrued vacation 926 1,088 Accrued severance 79 3,962 Merger costs — 16,071 Accrued other 8,763 12,082 Total accrued expenses $ 126,644 $ 150,917

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2019
Equity [Abstract]
Summary of Reserved Shares of Common Stock for Future Issuance	The Company has reserved for future issuance the following number of shares of common stock: September 30, 2019 December 31, 2018 Common stock options and RSUs outstanding (1) 12,618,799 9,309,204 Shares available for issuance under Akebia equity plans (2) 4,684,048 4,526,563 Warrant to purchase common stock 509,611 509,611 Shares available for issuance under the ESPP (3) 5,715,992 603,522 Total 23,528,450 14,948,900 (1) (2) On January 1, 2019, January 1, 2018 and January 1, 2017, the shares reserved for future grants under the 2014 Plan increased by 3,801,198, 1,575,329 and 1,265,863 shares, respectively, pursuant to the 2014 Plan Evergreen Provision. On December 12, 2018, the shares reserved for future grants under the 2014 Plan increased by 2,323,213 shares as a result of the Company’s addition of the Assumed Shares to the 2014 Plan. On December 19, 2017, the Company’s Board of Directors approved 750,000 shares for issuance as option awards in fiscal year 2018 under the Inducement Award Program. Additionally, on January 30, 2019, the Company’s Board of Directors approved 3,150,000 shares for issuance as option awards in fiscal year 2019 under the Inducement Award Program, or the 2019 Inducement Shares. (3) On June 6, 2019, the shares reserved for future issuance under the ESPP increased by 5,200,000 shares upon shareholder approval of the Amended and Restated 2014 Employee Stock Purchase Plan. On February 28, 2018 and February 28, 2017, the shares reserved for future issuance under the 2014 ESPP remained unchanged. There were no increases in the shares reserved for future issuance pursuant to the evergreen provision under the 2014 ESPP in 2017 and 2018 as the maximum aggregate number of shares available for purchase under the 2014 ESPP had reached its cap of 739,611 on February 28, 2016.
Stock-Based Compensation Expense Related to Share-Based Awards	The Company has classified its stock-based compensation expense related to share-based awards as follows: Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 (in thousands) (in thousands) Research and development $ 556 $ 647 $ 2,118 $ 2,090 Selling, general and administrative 2,057 1,605 4,873 4,888 Total $ 2,613 $ 2,252 $ 6,991 $ 6,978
Schedule of Compensation Expense by Type of Award	Compensation expense by type of award: Three Months Ended Nine Months Ended September 30, 2019 September 30, 2018 September 30, 2019 September 30, 2018 (in thousands) (in thousands) Stock options $ 1,305 $ 1,458 $ 3,490 $ 5,074 Restricted stock units 1,217 742 3,318 1,751 Employee stock purchase plan 91 52 183 153 Total $ 2,613 $ 2,252 $ 6,991 $ 6,978

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2019
Commitments And Contingencies Disclosure [Abstract]
Schedule of Undiscounted Minimum Rental Commitments Under Non-cancelable Leases	As of September 30, 2019, undiscounted minimum rental commitments under non-cancelable leases, for each of the next five years and total thereafter are as follows: Operating Leases (in thousands) Remaining 2019 $ 1,296 2020 7,008 2021 7,064 2022 6,735 2023 5,347 Thereafter 13,934 Total $ 41,384
Schedule of Difference Between Undiscounted Minimum Rental Commitments Under Non-cancelable Leases and Operating Leases Liabilities	As of September 30, 2019, the following represents the difference between the remaining undiscounted minimum rental commitments under non-cancelable leases and the operating lease liabilities: Operating Leases (in thousands) Total Undiscounted minimum rental commitments $ 41,384 Present value adjustment using incremental borrowing rate (7,689 ) Operating lease liabilities $ 33,695
Schedule of Future Minimum Payments Required Under Leases	At December 31, 2018, the Company’s future minimum payments required under these leases are as follows: Operating Lease (in thousands) 2019 $ 6,777 2020 7,008 2021 7,064 2022 6,735 2023 5,347 Thereafter 13,934 Total $ 46,865

Net Loss per Share (Tables)

Net Loss per Share (Tables)	9 Months Ended
	Sep. 30, 2019
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 loss per share, prior to the use of the treasury stock method, due to their anti-dilutive effect: As of September 30, 2019 2018 Warrant 509,611 509,611 Outstanding stock options 7,808,382 3,957,940 Unvested restricted stock units 4,810,417 893,850 Total 13,128,410 5,361,401

Nature of Organization and Op_2

Nature of Organization and Operations - Additional Information (Details)	Nov. 11, 2019USD ($)	Dec. 12, 2018shares	Sep. 30, 2019USD ($)
Nature Of Organization And Operations [Line Items]
Line of credit, maximum borrowing capacity			$ 40,000,000
Period for which funds insufficient to satisfy obligations			12 months
Closing of loan agreement subject to satisfaction of customary conditions			$ 100,000,000
Merger Agreement | Keryx
Nature Of Organization And Operations [Line Items]
Issued and outstanding cancelled, converted common stock		0.37433
Number of shares cancelled and converted in merger, shares issued | shares		59,270,410
Subsequent Event | Keryx | Term Loan | Collateral Agent, Pharmakon | Biopharma Credit Investments V (Master) LP
Nature Of Organization And Operations [Line Items]
Line of credit, maximum borrowing capacity	$ 100,000,000
Subsequent Event | Keryx | Term Loan | Collateral Agent, Pharmakon | Biopharma Credit Investments V (Master) LP | Tranche A
Nature Of Organization And Operations [Line Items]
Line of credit, maximum borrowing capacity	$ 80,000,000
Date to draw amount under credit facility	Nov. 25, 2019
Subsequent Event | Keryx | Term Loan | Collateral Agent, Pharmakon | Biopharma Credit Investments V (Master) LP | Tranche B
Nature Of Organization And Operations [Line Items]
Line of credit, maximum borrowing capacity	$ 20,000,000
Last date to draw amount under credit facility	Dec. 31, 2020

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details)	Jan. 01, 2019USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)Segment	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)
Summary Of Significant Accounting Policies [Line Items]
Number of operating segments | Segment				1
Additional operating lease liabilities, net of deferred rent		$ 33,695,000		$ 33,695,000
Operating lease, right-of-use asset		30,141,000		30,141,000
Prepaid expenses and other current assets		7,754,000		7,754,000		$ 15,724,000
Depreciation expense		600,000	$ 200,000	$ 1,700,000	$ 600,000
Intangible assets, estimated useful life				9 years
Otsuka U.S. Agreement
Summary Of Significant Accounting Policies [Line Items]
Cost share costs for license agreement		500,000	200,000
Reimbursable by Otsuka		200,000	100,000
Cost share costs by partner for license agreement		300,000	500,000
Reimbursable to Otsuka		$ 200,000	$ 100,000
Minimum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, Useful life				3 years
Maximum
Summary Of Significant Accounting Policies [Line Items]
Property, plant and equipment, Useful life				7 years
ASC 842
Summary Of Significant Accounting Policies [Line Items]
Cumulative effect of adoption in retained earnings	$ 0
Additional operating lease liabilities, net of deferred rent	37,100,000
Operating lease, right-of-use asset	33,400,000
Prepaid expenses and other current assets	$ 900,000

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Reconciliation of Cash, Cash Equivalents, and Restricted Cash (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Cash and cash equivalents	$ 122,886	$ 104,644	$ 162,430
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	125,241	$ 107,099	163,996	$ 71,437
Prepaid Expenses and Other Current Assets
Summary Of Significant Accounting Policies [Line Items]
Restricted cash, current	263
Other Assets
Summary Of Significant Accounting Policies [Line Items]
Restricted cash, noncurrent	$ 2,092		$ 1,566

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Property and Equipment and Related Accumulated Depreciation (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 16,416	$ 9,981
Less accumulated depreciation	(3,617)	(1,958)
Net property and equipment	$ 12,799	8,023
Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	3 years
Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	7 years
Computer equipment and software
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	3 years
Gross property, plant and equipment	$ 1,010	1,593
Furniture and fixtures
Property, Plant and Equipment [Line Items]
Gross property, plant and equipment	$ 2,086	1,170
Furniture and fixtures | Minimum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	5 years
Furniture and fixtures | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	7 years
Equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	7 years
Gross property, plant and equipment	$ 2,451	1,780
Leasehold improvements
Property, Plant and Equipment [Line Items]
Leasehold improvements, Useful Life	Shorter of the useful life or remaining lease term (10 years)
Gross property, plant and equipment	$ 10,869	5,324
Leasehold improvements | Maximum
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	10 years
Office equipment under capital lease
Property, Plant and Equipment [Line Items]
Property, plant and equipment, Useful life	3 years
Gross property, plant and equipment		$ 114

Product Revenue and Reserves _3

Product Revenue and Reserves for Variable Consideration - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Disaggregation Of Revenue [Line Items]
Total revenues	$ 91,977	$ 53,169	$ 265,446	$ 147,892
Product Revenue, Net
Disaggregation Of Revenue [Line Items]
Total revenues	$ 30,004		$ 82,204

Product Revenue and Reserves _4

Product Revenue and Reserves for Variable Consideration - Summary of Product Revenue Allowance and Reserve Categories (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2019USD ($)
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	$ 23,737
Current provisions related to sales in current year	80,876
Adjustments related to prior period sales	1,520
Credits/payments made relating to sales in current year	(25,195)
Credits/payments made relating to prior period sales	(50,083)
Balance at September 30, 2019	30,855
Chargebacks and Discounts
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	516
Current provisions related to sales in current year	5,617
Adjustments related to prior period sales	13
Credits/payments made relating to sales in current year	(4,108)
Credits/payments made relating to prior period sales	(1,373)
Balance at September 30, 2019	665
Rebates, Fees and other Deductions
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	22,861
Current provisions related to sales in current year	73,424
Adjustments related to prior period sales	1,507
Credits/payments made relating to sales in current year	(21,087)
Credits/payments made relating to prior period sales	(46,803)
Balance at September 30, 2019	29,902
Returns
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at December 31, 2018	360
Current provisions related to sales in current year	1,835
Credits/payments made relating to prior period sales	(1,907)
Balance at September 30, 2019	$ 288

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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	$ 91,977	$ 53,169	$ 265,446	$ 147,892
License, Collaboration and Other Revenue
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	61,973	53,169	183,242	147,892
License, Collaboration and Other Revenue | Mitsubishi Tanabe Pharma Corporation
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	0	0	10,000	9,281
License, Collaboration and Other Revenue | Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	39,718	29,030	103,461	75,086
License, Collaboration and Other Revenue | Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize International Collaboration and License Agreement
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	20,220	24,114	64,643	63,176
License, Collaboration and Other Revenue | Mitsubishi Tanabe Pharma Corporation and Otsuka Pharmaceutical Company Limited
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	59,938	53,144	178,104	147,543
License, Collaboration and Other Revenue | Japan Tobacco Incorporation and Torii Pharmaceutical Company Limited
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	1,549		4,266
License, Collaboration and Other Revenue | Clinical and Regulatory Activities
License, Collaboration and Other Revenue:
License, Collaboration and Other Revenue	$ 486	$ 25	$ 872	$ 349

License, Collaboration and Ot_4

License, Collaboration and Other Significant Agreements - Deferred Revenues Balance (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Deferred Revenue:
Short-Term	$ 32,142	$ 56,980
Long-Term	43,887	$ 55,709
Total	76,029
Otsuka Pharmaceutical Company. Ltd. | U.S.
Deferred Revenue:
Short-Term	18,873
Long-Term	28,576
Total	47,449
Otsuka Pharmaceutical Company. Ltd. | International
Deferred Revenue:
Short-Term	13,269
Long-Term	10,632
Total	23,901
Vifor Pharma
Deferred Revenue:
Long-Term	4,679
Total	$ 4,679

License, Collaboration and Ot_5

License, Collaboration and Other Significant Agreements - Schedule of Changes in Contract Assets and Liabilities (Details) - USD ($) $ in Thousands		9 Months Ended
		Sep. 30, 2019	Sep. 30, 2018
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities, Balance at End of Period		$ 76,029
Other Current Assets
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract assets, Additions		10,000	$ 531
Contract assets, Deductions		(10,000)	(531)
Accounts Receivable
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract assets, Balance at Beginning of Period	[1]	1,587	34,186
Contract assets, Additions	[1]	134,268	120,283
Contract assets, Deductions	[1]	(131,651)	(153,938)
Contract assets, Balance at End of Period	[1]	4,204	531
Deferred Revenue
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities, Balance at Beginning of Period		112,689	179,624
Contract liabilities, Additions		131,444	119,442
Contract liabilities, Deductions		(168,104)	(147,543)
Contract liabilities, Balance at End of Period		76,029	151,523
Accounts Payable
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liabilities, Balance at Beginning of Period		13,492
Contract liabilities, Additions			4,427
Contract liabilities, Deductions		$ (13,492)	(1,040)
Contract liabilities, Balance at End of Period			$ 3,387
[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 September 30, 2018 and 2019 and December 31, 2017 and 2018.

License, Collaboration and Ot_6

License, Collaboration and Other Significant Agreements - Schedule of Revenue Recognized Resulting from Changes in Contract Asset and Contract Liability (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Amounts included in deferred revenue at the beginning of the period	$ 27,095	$ 53,144	$ 60,441	$ 110,974
Performance obligations satisfied in previous periods			$ 1,254	$ 6,813

License, Collaboration and Ot_7

License, Collaboration and Other Significant Agreements - Additional Information (Details)

Apr. 08, 2019USD ($)

May 12, 2017USD ($)$ / sharesshares

Apr. 25, 2017USD ($)

Feb. 09, 2017USD ($)$ / sharesshares

Jul. 31, 2019USD ($)

Mar. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Sep. 30, 2019USD ($)shares

Sep. 30, 2018USD ($)

Mar. 31, 2017USD ($)

Sep. 30, 2019USD ($)Obligationshares

Sep. 30, 2018USD ($)

Dec. 31, 2018USD ($)shares

Dec. 31, 2017USD ($)

Sep. 30, 2017USD ($)

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Recognized revenue under license agreement

$ 91,977,000

$ 53,169,000

$ 265,446,000

$ 147,892,000

Deferred revenue

76,029,000

76,029,000

Collaborative arrangements additional cost sharing payments expected amount

63,700,000

Deferred revenue, current

32,142,000

32,142,000

$ 56,980,000

Deferred revenue, noncurrent

$ 43,887,000

$ 43,887,000

$ 55,709,000

Common stock shares sold | shares

118,863,735

118,863,735

116,887,518

License, Collaboration and Other Revenue

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Recognized revenue under license agreement

$ 61,973,000

53,169,000

$ 183,242,000

147,892,000

Accounts Receivable

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Accounts receivable

[1]

4,204,000

531,000

4,204,000

531,000

$ 1,587,000

$ 34,186,000

Accounts Payable

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Deferred revenue

3,387,000

3,387,000

13,492,000

Mitsubishi Tanabe Pharma Corporation | License, Collaboration and Other Revenue

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Recognized revenue under license agreement

0

0

10,000,000

9,281,000

Mitsubishi Tanabe Pharma Corporation | Development and Commercialize Collaboration Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

10,000,000

$ 10,000,000

Collaboration Agreement, expiration period

10 years

Collaboration Agreement, notice period for termination

12 months

Upfront cash payment received

$ 20,000,000

Percentage of royalty payments on sales

20.00%

Additional milestone or royalty payments received

$ 0

Number of performance obligations | Obligation

2

Mitsubishi Tanabe Pharma Corporation | Development and Commercialize Collaboration Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment received

$ 40,000,000

Milestone revenue

175,000,000

Mitsubishi Tanabe Pharma Corporation | New Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Data access fee receivable

$ 25,000,000

Mitsubishi Tanabe Pharma Corporation | Development And Commercialize Research And License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment received

20,000,000

Cost of research services

20,500,000

Deferred revenue

0

0

Accounts receivable

0

0

Mitsubishi Tanabe Pharma Corporation | Regulatory Milestone Payments

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

$ 10,000,000

Recognized revenue under license agreement

10,000,000

Mitsubishi Tanabe Pharma Corporation | Regulatory Milestone Payments | Development and Commercialize Collaboration Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

10,000,000

Mitsubishi Tanabe Pharma Corporation | Regulatory Milestone Payments | Development and Commercialize Collaboration Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment received

40,000,000

Mitsubishi Tanabe Pharma Corporation | Regulatory Milestone Payments | Development And Commercialize Research And License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

10,000,000

Mitsubishi Tanabe Pharma Corporation | Development, Regulatory and Commercial Events | Development and Commercialize Collaboration Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

225,000,000

Mitsubishi Tanabe Pharma Corporation | Development Milestones | Development and Commercialize Collaboration Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

10,000,000

Mitsubishi Tanabe Pharma Corporation | Commercial Milestone Payments | Development and Commercialize Collaboration Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

175,000,000

Mitsubishi Tanabe Pharma Corporation | Upfront | Development and Commercialize Collaboration Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Incurred clinical and commercial development cost

20,500,000

Mitsubishi Tanabe Pharma Corporation | Development Milestones One | Development And Commercialize Research And License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

6,000,000

Mitsubishi Tanabe Pharma Corporation | Development Milestones Two | Development And Commercialize Research And License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

4,000,000

Mitsubishi Tanabe Pharma Corporation | Development and Commercialize Collaboration Agreement | Development And Commercialize Research And License Agreement | Accounts Receivable

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Accounts receivable

0

0

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

$ 0

Number of performance obligations | Obligation

3

Deferred revenue

47,449,000

$ 47,449,000

Collaborative arrangements cost sharing payments

168,600,000

Collaborative arrangements additional cost sharing payments amount

$ 26,100,000

Percentage of market penetration for license agreement

90.00%

License agreement, notice period for termination

12 months

Transaction price

$ 391,100,000

Reimbursement for Otsuka's share of costs previously incurred

$ 33,800,000

Transaction price, description

As of September 30, 2019, the transaction price totaling $391.1 million is comprised of: (i) the up-front payment of $125.0 million, (ii) the cost share payment with respect to amounts incurred by the Company through December 31, 2016 of $33.8 million, (iii) the estimate of the base cost share payments to be received of approximately $168.6 million with respect to amounts incurred by the Company subsequent to December 31, 2016, and (iv) the estimate of the Additional Funding of approximately $63.7 million related to incremental cost share payments under the Otsuka Funding Option described above. As of September 30, 2019, no development or regulatory milestones have been assessed as probable of being reached and thus have been fully constrained.

Deferred revenue, current

18,873,000

$ 18,873,000

Deferred revenue, noncurrent

28,576,000

28,576,000

Cost share costs incurred

500,000

200,000

Reimbursable by Otsuka

200,000

100,000

Cost share costs by partner for license agreement

300,000

0.5

Reimbursable to Otsuka

200,000

100,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement | Global Development Plan

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Reimbursement for Otsuka's share of costs previously incurred

$ 33,800,000

Collaborative arrangements base cost sharing payments

168,600,000

Collaborative arrangements additional cost sharing payments expected amount

63,700,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement | License, Collaboration and Other Revenue

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Recognized revenue under license agreement

39,718,000

29,030,000

103,461,000

75,086,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement | Accounts Receivable

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Accounts receivable

1,200,000

$ 1,200,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement | Accounts Payable

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Deferred revenue, current

7,200,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement | Minimum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of increase in funding to fund current global development costs

52.50%

Reduction in percentage of future payments due upon current global development costs creditable

50.00%

Percentage of remaining creditable amount applied to future payments

50.00%

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement | Minimum | Global Development Plan

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Collaborative arrangements cost sharing payments

$ 232,300,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize United States Collaboration and License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Percentage of increase in funding to fund current global development costs

80.00%

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize International Collaboration and License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Number of performance obligations | Obligation

3

Deferred revenue

23,901,000

$ 23,901,000

Transaction price

250,400,000

Reimbursement for Otsuka's share of costs previously incurred

$ 200,000

Transaction price, description

As of September 30, 2019, the transaction price totaling $250.4 million is comprised of: (i) the 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) an estimate of the cost share payments to be received with respect to amounts incurred by the Company subsequent to March 31, 2017 of $177.2 million. As of September 30, 2019, no development or regulatory milestones have been assessed as probable of being reached and thus have been fully constrained.

Deferred revenue, current

13,269,000

$ 13,269,000

Deferred revenue, noncurrent

10,632,000

10,632,000

Estimate Subsequent Cost Share Payment Receivable

177,200,000

Milestone or royalty payments received

$ 0

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize International Collaboration and License Agreement | Global Development Plan

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Reimbursement for Otsuka's share of costs previously incurred

$ 200,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize International Collaboration and License Agreement | License, Collaboration and Other Revenue

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Recognized revenue under license agreement

20,220,000

$ 24,114,000

64,643,000

$ 63,176,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize International Collaboration and License Agreement | Accounts Receivable

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Accounts receivable

600,000

600,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize International Collaboration and License Agreement | Accounts Payable

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Deferred revenue, current

$ 6,300,000

Otsuka Pharmaceutical Company. Ltd. | Development and Commercialize International Collaboration and License Agreement | Minimum | Global Development Plan

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Estimate Subsequent Cost Share Payment Receivable

177,200,000

Otsuka Pharmaceutical Company. Ltd. | Regulatory Milestone Payments | Development and Commercialize United States Collaboration and License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

65,000,000

Otsuka Pharmaceutical Company. Ltd. | Regulatory Milestone Payments | Development and Commercialize International Collaboration and License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

52,000,000

Otsuka Pharmaceutical Company. Ltd. | Development Milestones | Development and Commercialize United States Collaboration and License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment received

125,000,000

Otsuka Pharmaceutical Company. Ltd. | Development Milestones | Development and Commercialize International Collaboration and License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment received

80,000,000

Otsuka Pharmaceutical Company. Ltd. | Commercial Milestone Payments | Development and Commercialize United States Collaboration and License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

575,000,000

Otsuka Pharmaceutical Company. Ltd. | Commercial Milestone Payments | Development and Commercialize International Collaboration and License Agreement | Maximum

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

525,000,000

Otsuka Pharmaceutical Company. Ltd. | Up-front, Non-refundable and Non-creditable | Development and Commercialize United States Collaboration and License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment received

$ 125,000,000

125,000,000

Otsuka Pharmaceutical Company. Ltd. | Up-front, Non-refundable and Non-creditable | Development and Commercialize International Collaboration and License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Upfront cash payment received

$ 73,000,000

73,000,000

Otsuka Pharmaceutical Company. Ltd. | Development and Regulatory Milestones | Development and Commercialize United States Collaboration and License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

0

Otsuka Pharmaceutical Company. Ltd. | Development and Regulatory Milestones | Development and Commercialize International Collaboration and License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

$ 0

Janssen Pharmaceutica NV | Development And Commercialize Research And License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Collaboration Agreement, expiration period

10 years

Collaboration Agreement, notice period for termination

180 days

Milestone revenue

$ 215,000,000

Upfront cash payment received

16,500,000

Upfront payment made in cash

$ 1,000,000

Warrant to purchase common stock, shares | shares

509,611

Johnson & Johnson Innovation | Development And Commercialize Research And License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Warrant to purchase common stock, shares | shares

509,611

Fair value of warrant

$ 3,400,000

$ 3,400,000

Exercise price | $ / shares

$ 9.81

Vifor (International) Ltd. | License Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Milestone revenue

$ 25,000,000

$ 25,000,000

License agreement, notice period for termination

12 months

Deferred revenue, noncurrent

$ 4,700,000

Common stock shares sold | shares

3,571,429

Sale of stock, price per share | $ / shares

$ 14

Proceeds from common stock sold

$ 50,000,000

Premium over the closing stock price of common stock | $ / shares

$ 12.69

Premium amount over the closing stock price of common stock

$ 4,700,000

Japan Tobacco Incorporation and Torii Pharmaceutical Company Limited | License, Collaboration and Other Revenue

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Recognized revenue under license agreement

1,549,000

$ 4,266,000

Japan Tobacco Incorporation and Torii Pharmaceutical Company Limited | License Agreement | Panion & BF Biotech, Incorporation

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Royalty payments

2,700,000

$ 7,500,000

Japan Tobacco Incorporation and Torii Pharmaceutical Company Limited | Sublicense Agreement

Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]

Number of performance obligations | Obligation

2

Recognized revenue under license agreement

$ 1,500,000

$ 4,300,000

License agreement, notice period for termination

6 months

Potential payment for achievement of annual net sales milestones

$ 55,000,000

Prior written notice for termination on the breach of agreement period

60 days

[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 September 30, 2018 and 2019 and December 31, 2017 and 2018.

Business Combination - Addition

Business Combination - Additional Information (Details)	Dec. 12, 2018USD ($)	Sep. 30, 2019USD ($)shares	Dec. 31, 2018USD ($)
Business Acquisition [Line Items]
Total fair value consideration		$ 527,754,000
Intangible assets, estimated useful life		9 years
Deferred tax liabilities		$ 1,752,000	$ 6,631,000
Keryx Biopharmaceuticals, Inc.
Business Acquisition [Line Items]
Total fair value consideration	$ 527,754,000
Business combination, Purchase price	$ 527,754,000
Risk-adjusted discount rate used to calculate present value of future expected cash inflows of intangible assets	20.00%
Preliminary fair value of the off-market element	$ 29,510,000
Goodwill deductible for tax purposes	$ 0
Deferred tax liabilities		$ 35,100,000
Keryx Biopharmaceuticals, Inc. | Auryxia
Business Acquisition [Line Items]
Intangible assets, estimated useful life	9 years
Keryx Biopharmaceuticals, Inc. | Common Stock
Business Acquisition [Line Items]
Total fair value consideration	$ 516,492,000
Keryx Biopharmaceuticals, Inc. | Merger Agreement
Business Acquisition [Line Items]
Issued and outstanding cancelled, converted common stock	0.37433	0.37433
Total fair value consideration	$ 527,800,000
Additional shares expected to be issued | shares		4,000,000
Aggregate shares available for conversion | shares		39,600,000
Fair value of additional shares issued		$ 13,400,000
Keryx Biopharmaceuticals, Inc. | Notes Conversion Agreement
Business Acquisition [Line Items]
Convertible notes amount		$ 164,700,000
Keryx Biopharmaceuticals, Inc. | Notes Conversion Agreement | Common Stock
Business Acquisition [Line Items]
Convertible notes converted into shares | shares		35,582,335

Business Combination - Summary

Business Combination - Summary of Total Fair Value Consideration (Details) - USD ($) $ in Thousands	Dec. 12, 2018	Sep. 30, 2019
Business Acquisition [Line Items]
Total fair value consideration		$ 527,754
Keryx Biopharmaceuticals, Inc.
Business Acquisition [Line Items]
Total fair value consideration	$ 527,754
Keryx Biopharmaceuticals, Inc. | Akebia Shares
Business Acquisition [Line Items]
Total fair value consideration	516,492
Keryx Biopharmaceuticals, Inc. | Akebia RSUs | Precombination Employee Services
Business Acquisition [Line Items]
Total fair value consideration	304
Keryx Biopharmaceuticals, Inc. | Akebia Stock Options | Precombination Employee Services
Business Acquisition [Line Items]
Total fair value consideration	$ 10,958

Business Combination - Summar_2

Business Combination - Summary of Total Fair Value Consideration (Parenthetical) (Details) - Keryx Biopharmaceuticals, Inc.	Dec. 12, 2018shares
Akebia Shares
Business Acquisition [Line Items]
Shares issued	57,773,090
Akebia RSUs
Business Acquisition [Line Items]
RSU / Options issued	602,752
Akebia Stock Options
Business Acquisition [Line Items]
RSU / Options issued	3,967,290

Business Combination - Summar_3

Business Combination - Summary of Purchase Price of Identifiable Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Dec. 12, 2018
Business Acquisition [Line Items]
Goodwill	$ 55,053	$ 55,053
Keryx Biopharmaceuticals, Inc.
Business Acquisition [Line Items]
Cash and cash equivalents			$ 5,257
Inventory			235,597
Trade accounts receivable, net			15,834
Prepaid expenses and other current assets			8,399
Goodwill			55,053
Intangible assets:
Developed product rights for Auryxia			329,130
Other intangible assets			545
Property and equipment, net			3,646
Other assets			14,441
Accounts payable			(17,570)
Accrued expenses			(42,972)
Deferred tax liability			(35,096)
Debt			(15,000)
Fair value of unfavorable executory contract			(29,510)
Total purchase price			$ 527,754

Available for Sale Securities -

Available for Sale Securities - Summary of Available for Sale Securities at Fair Value (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 22,721	$ 217,257
Gross Unrealized Gains	6	1
Gross Unrealized Losses		(262)
Fair Value	22,727	216,996
Cash and cash equivalents	122,886	104,644	$ 162,430
Cash and cash equivalents, Fair Value	122,886	104,644
Total cash, cash equivalents, and available for sale securities - Amortized Cost	145,607	321,901
Total cash, cash equivalents, and available for sale securities - Fair Value	145,613	321,640
U.S. government debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	22,476	158,518
Gross Unrealized Gains	6	1
Gross Unrealized Losses		(198)
Fair Value	22,482	158,321
Certificates of deposit
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	245	245
Fair Value	$ 245	245
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost		58,494
Gross Unrealized Losses		(64)
Fair Value		$ 58,430

Available for Sale Securities_2

Available for Sale Securities - Estimated Fair Value of Available for Sale Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Investments Debt And Equity Securities [Abstract]
Due in one year or less	$ 22,727
Total available for sale securities	$ 22,727	$ 216,996

Available for Sale Securities_3

Available for Sale Securities - Additional Information (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)Security	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)Security	Sep. 30, 2018USD ($)	Dec. 31, 2018Security
Investments Debt And Equity Securities [Abstract]
Gains (losses) on available for sale securities | $	$ 0	$ 0	$ 0	$ 0
Available-for-sale, securities in unrealized loss position, number of securities | Security	0		0		51

Available for Sale Securities_4

Available for Sale Securities - Summary of Available for Sale Securities that were in Continuous Unrealized Loss Position (Details) $ in Thousands	Dec. 31, 2018USD ($)
Schedule Of Available For Sale Securities [Line Items]
Unrealized Loss for Less Than 12 Months, Grosss Unrealized Losses	$ (223)
Unrealized Loss for Less Than 12 Months, Estimated Fair Value	174,456
Unrealized Loss for 12 Months or More, Gross Unrealized Losses	(39)
Unrealized Loss for 12 Months or More, Estimated Fair Value	29,934
Total, Gross Unrealized Losses	(262)
Total, Estimated Fair Value	204,390
U.S. government debt securities
Schedule Of Available For Sale Securities [Line Items]
Unrealized Loss for Less Than 12 Months, Grosss Unrealized Losses	(159)
Unrealized Loss for Less Than 12 Months, Estimated Fair Value	116,026
Unrealized Loss for 12 Months or More, Gross Unrealized Losses	(39)
Unrealized Loss for 12 Months or More, Estimated Fair Value	29,934
Total, Gross Unrealized Losses	(198)
Total, Estimated Fair Value	145,960
Corporate debt securities
Schedule Of Available For Sale Securities [Line Items]
Unrealized Loss for Less Than 12 Months, Grosss Unrealized Losses	(64)
Unrealized Loss for Less Than 12 Months, Estimated Fair Value	58,430
Total, Gross Unrealized Losses	(64)
Total, Estimated Fair Value	$ 58,430

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Assets Measured or Disclosed at Fair Value on Recurring Basis (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents, Fair Value	$ 122,886,000	$ 104,644,000
Assets Measured at fair value on recurring basis	22,727,000
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
Fair value measurements recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents, Fair Value	122,886,000	104,644,000
Assets Measured at fair value on recurring basis	145,613,000	321,640,000
Fair value measurements recurring | Certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis	245,000	245,000
Fair value measurements recurring | U.S. government debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis	22,482,000	158,321,000
Fair value measurements recurring | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis		58,430,000
Fair value measurements recurring | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash and cash equivalents, Fair Value	122,886,000	104,644,000
Assets Measured at fair value on recurring basis	122,886,000	104,644,000
Fair value measurements recurring | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis	22,727,000	216,996,000
Fair value measurements recurring | Level 2 | Certificates of deposit
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis	245,000	245,000
Fair value measurements recurring | Level 2 | U.S. government debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis	$ 22,482,000	158,321,000
Fair value measurements recurring | Level 2 | Corporate debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis		$ 58,430,000

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Additional Information (Details) - Level 3 - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Assets Measured at fair value on recurring basis	$ 0	$ 0
Liabilities measured at fair value on recurring basis	$ 0	$ 0

Inventory - Components of Inven

Inventory - Components of Inventory (Details) - USD ($)	Sep. 30, 2019	Dec. 31, 2018	Dec. 12, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 2,824,000	$ 1,880,000
Work in process	152,208,000	215,122,000
Finished goods	45,863,000	18,182,000
Total inventory	200,895,000	235,184,000
Inventory	115,987,000	114,245,000	$ 0
Other assets	$ 84,908,000	$ 120,939,000

Inventory - Additional Informat

Inventory - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Dec. 12, 2018
Inventory Disclosure [Abstract]
Inventory amounts written down	$ 2,900,000	$ 0	$ 5,968,000	$ 0
Inventory	$ 115,987,000		$ 115,987,000		$ 114,245,000	$ 0

Intangible Assets and Goodwil_2

Intangible Assets and Goodwill - Summary of Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 329,675	$ 329,675
Accumulated Amortization	(28,823)	(1,522)
ASC 842 Adjustment	(540)
Total	$ 300,312	328,153
Estimated useful life	9 years
Developed Product Rights for Auryxia
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 329,130	329,130
Accumulated Amortization	(28,818)	(1,517)
Total	$ 300,312	$ 327,613
Estimated useful life	9 years	9 years
Favourable Lease
Finite Lived Intangible Assets [Line Items]
Gross Carrying Value	$ 545	$ 545
Accumulated Amortization	(5)	(5)
ASC 842 Adjustment	$ (540)
Total		$ 540
Estimated useful life		4 years

Intangible Assets and Goodwil_3

Intangible Assets and Goodwill - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Finite Lived Intangible Assets [Line Items]
Amortization expense		$ 27,301
Goodwill	$ 55,053	55,053	$ 55,053
Developed Product Rights for Auryxia
Finite Lived Intangible Assets [Line Items]
Amortization expense	$ 9,100	$ 27,300

Intangible Assets and Goodwil_4

Intangible Assets and Goodwill - Schedule of Estimated Future Amortization Expense for Intangible Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
2019	$ 9,100
2020	36,402
2021	36,401
2022	36,402
2023	36,401
Thereafter	145,606
Total	$ 300,312	$ 328,153

Intangible Assets and Goodwil_5

Intangible Assets and Goodwill - Schedule of Goodwill (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Dec. 31, 2018
Goodwill And Intangible Assets Disclosure [Abstract]
Total fair value consideration	$ 527,754
Less: Fair value of identified acquired assets and liabilities, net	(472,701)
Goodwill	$ 55,053	$ 55,053

Accrued Expenses - Components o

Accrued Expenses - Components of Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables And Accruals [Abstract]
Accrued clinical expenses	$ 66,194	$ 71,881
Product revenue allowances	28,408	22,861
Accrued bonus	7,740	9,537
Lease liability	4,884
Accrued commercial manufacturing	3,352	6,383
Royalties	2,697	2,430
Professional fees	2,393	2,367
Accrued payroll	1,208	2,255
Accrued vacation	926	1,088
Accrued severance	79	3,962
Merger costs		16,071
Accrued other	8,763	12,082
Total accrued expenses	$ 126,644	$ 150,917

Debt - Additional Information (

Debt - Additional Information (Details) - USD ($)	Nov. 11, 2019	Nov. 07, 2019	Dec. 12, 2018	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Line Of Credit Facility [Line Items]
Line of credit, maximum borrowing capacity				$ 40,000,000	$ 40,000,000
Line of credit, available borrowing base				29,400,000	29,400,000
Line of credit, outstanding borrowings				0	0	$ 15,000,000
Silicon Valley Bank | Revolving Credit Facility | Loan and Security Agreement
Line Of Credit Facility [Line Items]
Line of credit, stated interest rate			6.75%
Line of credit, frequency of periodic interest payment			monthly
Line of credit, commitment fee description			Upon entry into the Loan and Security Agreement (payable in installments and subject to certain conditions), and at the one year anniversary of the effective date of the Loan and Security Agreement (or, if earlier, upon termination of or an event of default under the Loan and Security Agreement), Keryx paid to SVB a fee equal to 1.00% of the Line of Credit. Keryx was also required to pay on a quarterly basis a fee equal to 0.25% per annum of the average unused portion of the Line of Credit. Pursuant to the terms of the Loan and Security Agreement, Keryx was required to pay a termination fee of 2.00% of the Line of Credit, if the Loan and Security Agreement was terminated prior to the maturity date of July 18, 2020, subject to certain exceptions
Line of credit, commitment fee percentage			1.00%
Line of credit, frequency of commitment fee on unused portion			quarterly basis
Percentage of commitment fees percent on unused portion of credit facility			0.25%
Line of credit, termination fee percentage			2.00%
Debt instrument, maturity date			Jul. 18, 2020
Interest expense				$ 37,000	$ 400,000
Amortization expense of origination and other fees			$ 0
Silicon Valley Bank | Revolving Credit Facility | Loan and Security Agreement | Prime Rate | Minimum
Line Of Credit Facility [Line Items]
Basis spread on floating interest rate			2.00%
Subsequent Event | 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
Term loan, maturity date, description	The Term Loans will mature on the fifth anniversary of the Tranche A Funding Date, or the Maturity Date.
Term loan payment description	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, if certain conditions are met, it will have the option to repay the principal in equal quarterly payments starting on the 48th-month anniversary of the applicable Funding Date, or collectively the Amortization Schedule. 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
Facility fee percentage on principal amount	2.00%
Prepayment premium percentage on principal if prepaid prior to third anniversary of funding	2.00%
Prepayment premium percentage on principal if prepaid prior to fourth anniversary and after third anniversary of funding	1.00%
Prepayment premium percentage on principal if prepaid after fourth anniversary of funding	0.50%
Subsequent Event | 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%
Subsequent Event | Biopharma Credit Investments V (Master) LP | Keryx | Term Loan | Collateral Agent, Pharmakon | LIBOR
Line Of Credit Facility [Line Items]
Debt instrument, floor rate	2.00%
Debt instrument, cap rate	3.35%
Subsequent Event | 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
Date to draw amount under credit facility	Nov. 25, 2019
Subsequent Event | 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
Last date to draw amount under credit facility	Dec. 31, 2020
Subsequent Event | Silicon Valley Bank | Revolving Credit Facility | Loan and Security Agreement | Keryx
Line Of Credit Facility [Line Items]
Termination fee		$ 800,000

Warrant - Additional Informatio

Warrant - Additional Information (Details) - Janssen Agreement - USD ($) $ / shares in Units, $ in Millions	9 Months Ended
	Sep. 30, 2019	Feb. 28, 2017
Class Of Warrant Or Right [Line Items]
Warrant to purchase common stock, shares		509,611
Exercise price		$ 9.81
Fair value of warrant at issuance	$ 3.4
Warrant expiration date	Feb. 9, 2022

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details)	Sep. 30, 2019$ / sharesshares	Feb. 28, 2019shares	Dec. 12, 2018shares	Apr. 30, 2019shares	Sep. 30, 2019USD ($)$ / sharesshares	Jun. 30, 2019shares	Sep. 30, 2018USD ($)shares	Sep. 30, 2019USD ($)Installment$ / sharesshares	Sep. 30, 2018USD ($)shares	Mar. 31, 2019shares	Dec. 31, 2018$ / sharesshares	Jun. 30, 2018shares	Mar. 31, 2018shares	Dec. 31, 2017shares	Feb. 28, 2014shares
Class of Stock [Line Items]
Common stock, shares authorized	175,000,000				175,000,000			175,000,000			175,000,000
Common stock, par value | $ / shares	$ 0.00001				$ 0.00001			$ 0.00001			$ 0.00001
Common stock, shares issued	118,863,735				118,863,735			118,863,735			116,887,518
Common stock, shares outstanding	118,863,735				118,863,735			118,863,735			116,887,518
Preferred stock, shares authorized	25,000,000				25,000,000			25,000,000			25,000,000
Preferred stock, par value | $ / shares	$ 0.00001				$ 0.00001			$ 0.00001			$ 0.00001
Preferred stock, shares issued	0				0			0			0
Preferred stock, shares outstanding	0				0			0			0
Common stock, shares reserved for future issuance	23,528,450				23,528,450			23,528,450			14,948,900
Stock-based compensation expense | $					$ 2,613,000		$ 2,252,000	$ 6,991,000	$ 6,978,000
2014 Plans
Class of Stock [Line Items]
Common stock, shares reserved for future issuance															1,785,000
Incremental rate at which the shares reserved for issuance increase								3.00%
2014 Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	5,715,992				5,715,992			5,715,992
Purchase price at the end of offering period								85.00%
Offering period								6 months
Shares issued								87,530
Stock-based compensation expense | $					$ 100,000		52,000	$ 200,000	200,000
Inducement Award Program
Class of Stock [Line Items]
Maximum shares of common stock authorized to be issued	3,150,000				3,150,000			3,150,000
Granted, Shares								1,228,900
Outstanding, Shares	1,208,100				1,208,100			1,208,100
Inducement Award Program | Employees
Class of Stock [Line Items]
Granted, Shares								1,228,900
Stock Options
Class of Stock [Line Items]
Shares issued		2,028,625
Stock-based compensation description								Options 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 expiration after the date of grant								10 years
Stock-based compensation expense | $					$ 1,305,000		1,458,000	$ 3,490,000	5,074,000
Stock Options | Minimum
Class of Stock [Line Items]
Vesting periods								12 months
Stock Options | Maximum
Class of Stock [Line Items]
Vesting periods								48 months
Stock Options | Share-based Compensation Award, Tranche, First Anniversary of Grant Date
Class of Stock [Line Items]
Vesting percentage								100.00%
Stock Options | Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting periods								1 year
Vesting percentage								25.00%
Stock Options | Share Based Compensation Award Tranche Two
Class of Stock [Line Items]
Number of equal quarterly installments | Installment								12
Stock Options | 2014 Plans | Employees
Class of Stock [Line Items]
Granted, Shares								2,028,625
Stock Options | 2014 Plans | Director
Class of Stock [Line Items]
Granted, Shares								180,900
Restricted Stock Units
Class of Stock [Line Items]
Granted, Shares	2,979,400	1,384,775
Stock-based compensation description								RSUs granted by the Company vest in one of the following ways: (i) 100% of each RSU grant vests on either the first or the third anniversary of the grant date, or (ii) one third of each RSU grant vests on the first, second and third anniversaries of the grant date, subject, in each case, to the individual’s continued service through the applicable vesting date, or (iii) 50% of each RSU grant vests on the first anniversary and 25% of each RSU grant vests in 6 months increment after the one year anniversary of the grant date
Stock-based compensation expense | $					$ 1,217,000		$ 742,000	$ 3,318,000	$ 1,751,000
Restricted Stock Units | Minimum
Class of Stock [Line Items]
Vesting periods								1 year
Restricted Stock Units | Maximum
Class of Stock [Line Items]
Vesting periods								3 years
Restricted Stock Units | Share Based Compensation Award Tranche One
Class of Stock [Line Items]
Vesting percentage								50.00%
Restricted Stock Units | Share Based Compensation Award Tranche Two
Class of Stock [Line Items]
Vesting periods								6 months
Vesting percentage								25.00%
Restricted Stock Units | Share-based Compensation Award, Tranche, First Or Third Anniversary of Grant Date
Class of Stock [Line Items]
Vesting percentage								100.00%
Restricted Stock Units | 2014 Plans | Employees
Class of Stock [Line Items]
Granted, Shares								4,430,945
Restricted Stock Units | 2014 Plans | Director
Class of Stock [Line Items]
Granted, Shares								123,300
Performance-Based Stock Options
Class of Stock [Line Items]
Granted, Shares								0	0
Oustanding, Shares	59,892		0		59,892			59,892
Vesting percentage, Following achievement of performance condition			50.00%
Performance-Based Stock Options | Keryx Biopharmaceuticals, Inc. | Merger Agreement
Class of Stock [Line Items]
Granted, Shares			233,954
Performance-Based Stock Options | Minimum
Class of Stock [Line Items]
Potential share issuable percentage			0.00%
Performance-Based Stock Options | Maximum
Class of Stock [Line Items]
Potential share issuable percentage			100.00%
Vesting percentage, upon achievement of performance condition			50.00%
Common Stock
Class of Stock [Line Items]
Common stock, shares outstanding	118,863,735				118,863,735	118,787,301	57,046,563	118,863,735	57,046,563	117,122,262	116,887,518	56,913,886	56,857,470	47,612,619
Common stock shares repurchased and retired				55,324		55,324

Stockholders' Equity - Summary

Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Details) - shares	Sep. 30, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	23,528,450	14,948,900
Warrant To Purchase Common Stock
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	509,611	509,611
Stock Options and Restricted Stock Units
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	12,618,799	9,309,204
Akebia Equity Plans
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	4,684,048	4,526,563
Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock, shares reserved for future issuance	5,715,992	603,522

Stockholders' Equity - Summar_2

Stockholders' Equity - Summary of Reserved Shares of Common Stock for Future Issuance (Parenthetical) (Details) - shares

Jun. 06, 2019

Jan. 01, 2019

Dec. 12, 2018

Feb. 28, 2018

Jan. 01, 2018

Feb. 28, 2017

Jan. 01, 2017

Sep. 30, 2019

Jan. 30, 2019

Dec. 31, 2018

Dec. 19, 2017

Feb. 28, 2016

Feb. 28, 2014

Class of Stock [Line Items]

Common stock, shares reserved for future issuance

23,528,450

14,948,900

Employee Stock Purchase Plan

Class of Stock [Line Items]

Increase in common stock, shares reserved for future issuance

5,200,000

0

0

Common stock, shares reserved for future issuance

5,715,992

603,522

Maximum aggregate number of shares available for purchase

739,611

2014 Plans

Class of Stock [Line Items]

Increase in common stock, shares reserved for future issuance

3,801,198

2,323,213

1,575,329

1,265,863

Common stock, shares reserved for future issuance

1,785,000

Inducement Award Program

Class of Stock [Line Items]

Common stock, shares reserved for future issuance

3,150,000

750,000

Stockholders Equity - Stock-Bas

Stockholders Equity - Stock-Based Compensation Expense Related to Share-Based Awards (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,613	$ 2,252	$ 6,991	$ 6,978
Research and Development
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	556	647	2,118	2,090
Selling, General and Administrative
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,057	$ 1,605	$ 4,873	$ 4,888

Stockholders Equity - Schedule

Stockholders Equity - Schedule of Compensation Expense by Type of Award (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 2,613	$ 2,252	$ 6,991	$ 6,978
Stock Options
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,305	1,458	3,490	5,074
Restricted Stock Units
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	1,217	742	3,318	1,751
Employee Stock Purchase Plan
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 91	$ 52	$ 183	$ 153

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Net deferred tax liability	$ 1,752	$ 1,752	$ 6,631
Benefit from income taxes	$ (1,277)	$ (4,879)

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details)	1 Months Ended			3 Months Ended	9 Months Ended
	Sep. 30, 2019USD ($)ft²Extension_Option	Apr. 30, 2018USD ($)ft²	Jul. 31, 2016USD ($)ft²	Sep. 30, 2019USD ($)ft²Extension_Option	Sep. 30, 2019USD ($)ft²Extension_Option	Dec. 12, 2018USD ($)
Commitments And Contingencies [Line Items]
Lessee, operating lease, residual value guarantee, description					The lease agreements do not contain residual value guarantees.
Lessee, operating lease, residual value guarantee					false
Operating lease, cost				$ 1,700,000	$ 5,000,000
Operating lease, payments				1,700,000	5,200,000
Total remaining contract costs	$ 76,900,000			$ 76,900,000	76,900,000
Contract cost incurred in research and development activities					$ 52,700,000
BioVectra Inc
Commitments And Contingencies [Line Items]
Agreement expiration year					2026
Description of termination of agreement prior to contract term					The Company may terminate the BioVectra Agreement prior to the expiration of the contract term, which could result in early termination fee.
Cost of purchased minimum quantity product					$ 135,700,000
Preliminary fair value of the off-market element						$ 29,500,000
Accretion expense					500,000
Siegfried Evionnaz SA
Commitments And Contingencies [Line Items]
Cost of purchased minimum quantity product					$ 66,300,000
Agreement expiration date					Dec. 31, 2021
Agreement renewal term termination					1 year
Agreement early termination					Dec. 31, 2021
Minimum
Commitments And Contingencies [Line Items]
Operating lease, incremental borrowing rates based on remaining lease term	5.91%			5.91%	5.91%
Operating lease, remaining lease term	2 years 2 months 1 day			2 years 2 months 1 day	2 years 2 months 1 day
Maximum
Commitments And Contingencies [Line Items]
Operating lease, incremental borrowing rates based on remaining lease term	6.94%			6.94%	6.94%
Operating lease, remaining lease term	6 years 11 months 12 days			6 years 11 months 12 days	6 years 11 months 12 days
Letter of Credit | Other Current Assets
Commitments And Contingencies [Line Items]
Total security deposit in connection with lease	$ 1,600,000			$ 1,600,000	$ 1,600,000
Office Space
Commitments And Contingencies [Line Items]
Lease expiration date					Sep. 11, 2026
Lease period, number of extension options | Extension_Option	1			1	1
Lease extension period	5 years			5 years	5 years
Lab Space
Commitments And Contingencies [Line Items]
Lease expiration date					Nov. 30, 2021
Lease period, number of extension options | Extension_Option	1			1	1
Lease extension period	2 years			2 years	2 years
Cambridge Lease Amendment
Commitments And Contingencies [Line Items]
Area of property leased | ft²		65,167
Third Amendment to the Cambridge Lease
Commitments And Contingencies [Line Items]
Area of property leased | ft²			45,362
Monthly lease payments			$ 242,000
Operating lease payments commencement date			Jan. 1, 2017
Lease Monthly Payments On Or About January 1 2017
Commitments And Contingencies [Line Items]
Monthly lease payments			$ 22,000
Fifth Amendment to the Cambridge Lease | Office Space
Commitments And Contingencies [Line Items]
Area of property leased | ft²		19,805
Monthly lease payments		$ 135,000
Operating lease payments commencement date		Feb. 28, 2019
Leased property delivered, date		2018-09
Leased property subject to annual rent escalations, commencement date		2019-09
Boston Lease | Office Space
Commitments And Contingencies [Line Items]
Area of property leased | ft²	27,300			27,300	27,300
Monthly lease payments					$ 136,000
Lease expiration month year					2023-02
Operating sublease commencement date	Oct. 16, 2019
Sublease expiration date	Feb. 27, 2023
Keryx Biopharmaceuticals, Inc. | Letter of Credit | Other Current Assets
Commitments And Contingencies [Line Items]
Total security deposit in connection with lease	$ 800,000			$ 800,000	$ 800,000
Keryx Biopharmaceuticals, Inc. | Office Space
Commitments And Contingencies [Line Items]
Lease expiration date					Feb. 28, 2023
Lease period, number of extension options | Extension_Option	1			1	1
Lease extension period	5 years			5 years	5 years

Commitments and Contingencies_2

Commitments and Contingencies - Schedule of Undiscounted Minimum Rental Commitments Under Non-cancelable Leases (Details) $ in Thousands	Sep. 30, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating Leases, remaining 2019	$ 1,296
Operating Leases, 2020	7,008
Operating Leases, 2021	7,064
Operating Leases, 2022	6,735
Operating Leases, 2023	5,347
Operating Leases, Thereafter	13,934
Operating Leases, Total	$ 41,384

Commitments and Contingencies_3

Commitments and Contingencies - Schedule of Undiscounted Minimum Rental Commitments Under Non-cancelable Leases and Operating Leases Liabilities (Details) $ in Thousands	Sep. 30, 2019USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating Leases, Total	$ 41,384
Present value adjustment using incremental borrowing rate	(7,689)
Operating lease liabilities	$ 33,695

Commitments and Contingencies_4

Commitments and Contingencies - Schedule of Future Minimum Payments Required Under Leases (Details) $ in Thousands	Dec. 31, 2018USD ($)
Commitments And Contingencies Disclosure [Abstract]
Operating Lease, 2019	$ 6,777
Operating Lease, 2020	7,008
Operating Lease, 2021	7,064
Operating Lease, 2022	6,735
Operating Lease, 2023	5,347
Operating Lease, Thereafter	13,934
Operating Lease, Total	$ 46,865

Net Loss per Share - Anti-Dilut

Net Loss per Share - Anti-Dilutive Securities Excluded from Calculation of Diluted Net Loss per Share (Details) - shares	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	13,128,410	5,361,401
Warrant
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	509,611	509,611
Stock Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	7,808,382	3,957,940
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	4,810,417	893,850