Keryx Biopharmaceuticals (KERX) 10-Q 7 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	KERX
Entity Registrant Name	KERYX BIOPHARMACEUTICALS INC
Entity Central Index Key	1,114,220
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		119,223,490

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 113,999	$ 111,810
Inventory	26,010	12,681
Accounts receivable, net	9,198	5,236
Other current assets	15,571	3,170
Total current assets	164,778	132,897
Property, plant and equipment, net	4,698	4,211
Goodwill	3,208	3,208
Other assets, net	1,138	1,111
Total assets	173,822	141,427
Current liabilities:
Accounts payable and accrued expenses	36,538	21,190
Deferred lease incentive, current portion	244	244
Other current liabilities	138	117
Total current liabilities	36,920	21,551
Convertible senior notes	125,000	125,000
Deferred lease incentive, net of current portion	1,078	1,262
Deferred tax liability	930	870
Other liabilities	932	1,040
Total liabilities	164,860	149,723
Commitments and contingencies
Stockholders’ equity (deficit):
Preferred stock, $0.001 par value per share (5,000,000 shares authorized, no shares issued and outstanding)	0	0
Common stock, $0.001 par value per share (230,000,000 and 180,000,000 shares authorized, 119,224,738 and 105,921,052 shares issued, 119,144,790 and 105,841,104 shares outstanding at September 30, 2017 and December 31, 2016, respectively)	119	106
Additional paid-in capital	977,309	827,053
Treasury stock, at cost, 79,948 shares	(357)	(357)
Accumulated deficit	(968,109)	(835,098)
Total stockholders’ equity (deficit)	8,962	(8,296)
Total liabilities and stockholders’ equity (deficit)	$ 173,822	$ 141,427

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	230,000,000	180,000,000
Common stock, shares issued (in shares)	119,224,738	105,921,052
Common stock, shares outstanding (in shares)	119,144,790	105,841,104
Treasury stock, shares (in shares)	79,948	79,948

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues:
Net U.S. Auryxia product sales	$ 13,597	$ 5,050	$ 38,218	$ 18,945
License revenue	1,399	1,287	3,741	3,505
Total revenues	14,996	6,337	41,959	22,450
Costs and expenses:
Cost of goods sold	5,856	18,196	14,508	24,365
License expense	838	772	2,244	2,103
Research and development	9,275	8,674	25,051	23,320
Selling, general and administrative	22,746	20,521	70,835	61,518
Total costs and expenses	38,715	48,163	112,638	111,306
Operating loss	(23,719)	(41,826)	(70,679)	(88,856)
Other income (expense):
Amortization of debt discount	0	0	(62,965)	(34,226)
Other income (expense), net	241	150	693	(4,169)
Total other income (expense)	241	150	(62,272)	(38,395)
Loss before income taxes	(23,478)	(41,676)	(132,951)	(127,251)
Income taxes	20	20	60	60
Net loss	$ (23,498)	$ (41,696)	$ (133,011)	$ (127,311)
Basic and diluted net loss per common share (in dollars per share)	$ (0.20)	$ (0.39)	$ (1.18)	$ (1.20)
Weighted average shares used in computing basic and diluted net loss per common share (in shares)	118,992,825	105,924,106	112,928,551	105,805,669

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities
Net loss	$ (133,011)	$ (127,311)
Adjustments to reconcile loss to cash flows used in operating activities:
Stock-based compensation expense	10,707	10,563
Amortization of debt discount	62,965	34,226
Change in fair value of derivative liability	(225)	4,718
Depreciation and amortization	689	776
Loss on disposal of fixed assets	0	54
Amortization of deferred lease incentive	(184)	(183)
Write-down of inventory to net realizable value	1,671	16,352
Cash received from landlord	0	637
Deferred income taxes	60	60
Changes in operating assets and liabilities:
Other current assets	(12,382)	(563)
Accounts receivable, net	(3,962)	3,656
Inventory	(11,845)	(2,148)
Other assets	(27)	0
Other current liabilities	21	(355)
Accounts payable and accrued expenses	12,318	(3,313)
Deferred revenue	0	(3,526)
Other liabilities	(108)	105
Net cash used in operating activities	(73,313)	(66,252)
Cash flows from investing activities
Purchases of property, plant and equipment	(1,176)	(2,064)
Net cash used in investing activities	(1,176)	(2,064)
Cash flows from financing activities
Proceeds from issuance of common stock, net of commission	75,722	0
Payments for common stock issuance costs	(102)	0
Proceeds from exercise of stock options	1,058	198
Net cash provided by financing activities	76,678	198
Net increase (decrease) in cash and cash equivalents	2,189	(68,118)
Cash and cash equivalents at beginning of the period	111,810	200,290
Cash and cash equivalents at end of the period	113,999	132,172
Non-cash financing activities:
Reclassification of derivative liability to equity	$ 62,735	$ 51,404

Description of Business

Description of Business	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Description of Business	DESCRIPTION OF BUSINESS We are a commercial stage biopharmaceutical company focused on bringing innovative medicines to people with kidney disease. Our long-term vision is to build a multi-product kidney care company. Our marketed product, Auryxia ® (ferric citrate) tablets, is an orally available, absorbable, iron-based medicine. Auryxia is approved by the U.S. Food and Drug Administration, or FDA, for two indications; the medication was originally approved in September 2014 for the control of serum phosphorus levels in patients with chronic kidney disease, or CKD, on dialysis. The FDA approved Auryxia tablets for an additional indication in November 2017 for the treatment of iron deficiency anemia in adults with CKD, not on dialysis. With two FDA-approved indications, we will leverage our U.S. clinical and commercial infrastructure to make Auryxia available to millions of people with CKD. Ferric citrate is also approved in Japan under the trade name Riona ® and marketed by our Japanese partner, Japan Tobacco, Inc., or JT, and its subsidiary, Torii Pharmaceutical Co., Ltd., or Torii, and approved in Europe as Fexeric ® . Our vision of building a multi-product kidney care company includes expansion of our product portfolio with other medicines that can help patients with kidney disease.

Basis of Presentation and Summa

Basis of Presentation and Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation and Summary of Significant Accounting Policies	BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited condensed consolidated financial statements were prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and footnotes required by GAAP for complete financial statements. All adjustments that are, in the opinion of management, of a normal recurring nature and are necessary for a fair presentation of these interim financial statements have been included. These interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements contained in our Annual Report on Form 10-K for the year ended December 31, 2016 . The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP. The results of operations for the three and nine months ended September 30, 2017 are not necessarily indicative of the results that may be expected for the entire fiscal year or any other interim period. Principles of Consolidation The condensed consolidated financial statements include our financial statements and those of our wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation. Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of these condensed consolidated financial statements and the reported amounts of revenues and expenses during the applicable reporting period. Actual results could differ from those estimates. Such differences could be material to these condensed consolidated financial statements. Revenue Recognition Our primary source of revenue during the reporting periods was product sales. We sell product to a limited number of major wholesalers, our Distributors, as well as certain pharmacies, or collectively, our Customers. Our Distributors resell the product to retail pharmacies for purposes of their reselling the product to fill patient prescriptions. In accordance with GAAP, our revenue recognition policy requires that (i) there is persuasive evidence that an arrangement exists between us and the Customer, (ii) delivery has occurred, (iii) collectability is reasonably assured, and (iv) the price is fixed or determinable. In the fourth quarter of 2016, we began to recognize revenue under the pull-through (ex-factory) method based on sales to our Customers as a result of our ability to reasonably estimate product returns based on our prior sales and product return history. Prior to the fourth quarter of 2016, we recognized revenue based on the resale of Auryxia for the purposes of filling patient prescriptions, and not based on initial sales from us to our Customers as we did not have sufficient history such that we could reliably estimate product returns based on sales to our Customers. As a result, prior to the fourth quarter of 2016, we deferred Auryxia revenue recognition until the earlier of the product being resold for purposes of filling patient prescriptions and the expiration of the right of return (twelve months after the expiration date of the product). The deferred revenue was recorded net of discounts, rebates, and chargebacks. We also deferred the related cost of product sales and recorded such amounts as finished goods inventory held by others, which was included in inventory on our condensed consolidated balance sheet, until revenue related to such product sales was recognized. Our U.S. Auryxia product sales for the three and nine months ended September 30, 2017 and 2016 were offset by provisions for allowances and accruals as set forth in the tables below. (in thousands) Three months ended Percent of gross Auryxia product sales Three months ended Percent of gross Auryxia product sales Gross Auryxia product sales $ 30,620 $ 8,711 Less provision for product sales allowances and accruals: Trade allowances 2,894 9 % 750 9 % Rebates, chargebacks and discounts 13,251 43 % 2,787 32 % Product returns 592 3 % — — Other incentives (1) 286 1 % 124 1 % Total 17,023 56 % 3,661 42 % Net U.S. Auryxia product sales $ 13,597 $ 5,050 (1) Includes co-pay assistance and voucher rebates. (in thousands) Nine months ended September 30, 2017 Percent of gross Nine months ended September 30, 2016 Percent of gross Gross Auryxia product sales $ 74,603 $ 29,896 Less provision for product sales allowances and accruals Trade allowances 7,122 10 % 3,451 12 % Rebates, chargebacks and discounts 27,365 37 % 7,008 23 % Product returns 870 1 % — — Other incentives (1) 1,028 1 % 492 2 % Total 36,385 49 % 10,951 37 % Net U.S. Auryxia product sales $ 38,218 $ 18,945 (1) Includes co-pay assistance and voucher rebates. Reclassifications Certain amounts in the table above for the nine months ended September 30, 2017 , which also appear in Management's Discussion and Analysis of Financial Condition and Results of Operations, have been reclassified for consistency. Specifically, fees paid to a Customer during the three months ended March 31, 2017 totaling $0.5 million that were included in the caption "Rebates, chargebacks and discounts" were reclassified to the caption "Trade allowances" for the nine months ended September 30, 2017 . Total product sales allowances for the nine months ended September 30, 2017 were not affected. Basic and Diluted Net Loss Per Common Share Basic net loss per share is computed by dividing the losses allocable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share does not reflect the effect of shares of common stock to be issued upon the exercise of stock options, as their inclusion would be anti-dilutive. The following table presents amounts that were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect: (in thousands) September 30, 2017 September 30, 2016 Options to purchase common stock 12,135 8,823 Shares issuable upon conversion of convertible senior notes 33,422 33,422 45,557 42,245 Concentrations of Credit Risk We do not have significant off-balance-sheet risk or credit risk concentrations. We primarily maintain our cash and cash equivalents in deposit accounts and institutional money market funds. As of September 30, 2017 , approximately $25.9 million of our total $114 million cash and cash equivalents balance was invested in institutional money market funds. See Note 3 – Fair Value Measurements . Our accounts receivable, net at September 30, 2017 and December 31, 2016 represent amounts due to us from our Customers. We perform ongoing credit evaluations of our Customers and generally do not require collateral. The following table sets forth customers who represented 10% or more of our total accounts receivable, net as of September 30, 2017 and December 31, 2016 . September 30, 2017 December 31, 2016 McKesson Corporation 24 % 31 % Fresenius Medical Care Rx 23 % 22 % AmerisourceBergen Drug Corporation 21 % 23 % Cardinal Health, Inc. 18 % 11 % DaVita Rx 9 % 10 % New Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or the FASB, or other standard setting bodies that we adopt as of the specified effective date. In May 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-09, Revenue from Contracts with Customers (Topic 606) , a comprehensive new standard which amends revenue recognition principles and provides a single set of criteria for revenue recognition among all industries. The new standard provides a five-step framework whereby revenue is recognized when promised goods or services are transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard also requires enhanced disclosures pertaining to revenue recognition in both interim and annual periods. The standard is effective for interim and annual periods beginning after December 15, 2017 and allows for adoption using a full retrospective method, or a modified retrospective method. The FASB has subsequently issued amendments to ASU No. 2014-09 that have the same effective date and transition date of January 1, 2018. We expect to adopt these standards using the modified retrospective method. We have identified the customer contracts that are in the scope of these standards, including contracts with our distributors and specialty pharmacies, as well as contracts with third-party payers. We are in the process of reviewing the contracts to assess the potential impact of these standards. Prior to January 1, 2018, we plan to complete our review of the identified customer contracts as well as our license agreements to determine the impact that these standards will have on our financial position, results of operations and disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases . The new standard requires that all lessees recognize the assets and liabilities that arise from leases on the balance sheet and disclose qualitative and quantitative information about its leasing arrangements. The new standard will be effective for us on January 1, 2019. The adoption of this standard may have a material impact on our financial position as it may impact the amount of our assets and liabilities. We are currently evaluating the potential impact that this standard may have on our results of operations. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . The new standard addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The new standard will be effective for us on January 1, 2018. This standard is not expected to have a material impact on our statement of cash flows upon adoption.

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	FAIR VALUE MEASUREMENTS The following table provides the fair value measurements of applicable financial assets as of September 30, 2017 and December 31, 2016 : Financial assets at fair value Financial assets at fair value (in thousands) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Cash equivalents (1) $ 25,911 $ — $ — $ 107,084 $ — $ — Total assets $ 25,911 $ — $ — $ 107,084 $ — $ — (1) Cash equivalents as of September 30, 2017 and December 31, 2016 consisted of institutional money market funds. The carrying value of our money market funds approximates fair value due to their short-term maturities. Debt In October 2015, we issued $125 million in Convertible Senior Notes, due 2020, or the Notes, in a private financing to funds managed by Baupost Group Securities, L.L.C., or Baupost. As of September 30, 2017 and December 31, 2016 , the fair value of the Notes was $237 million and $196 million , respectively, which differs from their carrying value. The fair value of the Notes is influenced by our stock price and stock price volatility. See Note 9 – Debt for additional information on our debt obligations.

Inventory

Inventory	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Inventory	INVENTORY Inventory consists of the following at September 30, 2017 and December 31, 2016 : (in thousands) September 30, 2017 December 31, 2016 Raw materials $ 520 $ 418 Work in process 22,330 11,430 Finished goods 3,160 833 Total inventory $ 26,010 $ 12,681

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit)	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholders' Equity (Deficit)	STOCKHOLDERS’ EQUITY (DEFICIT) Change in Stockholders’ Equity (Deficit) Total stockholders’ equity was $9.0 million at September 30, 2017 , which is an increase of $17.3 million during the nine months ended September 30, 2017 as compared to stockholders’ deficit at December 31, 2016 of $8.3 million . This increase was primarily attributable to the proceeds from the issuance of common stock of $75.7 million , the reclassification of the derivative liability related to the Notes to equity of $62.7 million and $10.7 million related to stock-based compensation expense, partially offset by our net loss of approximately $133.0 million .

Stock-Based Compensation Expens

Stock-Based Compensation Expense	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock-Based Compensation Expense	STOCK-BASED COMPENSATION EXPENSE Equity Incentive Plans As of September 30, 2017 , a total of 1,966,235 shares were available for the issuance of stock options or other stock-based awards under our stock option and incentive plans. Stock Options The following table summarizes stock option activity for the nine months ended September 30, 2017 : Number of shares Weighted average exercise price Outstanding at December 31, 2016 8,677,998 $ 7.28 Granted 4,581,750 5.46 Exercised (328,575 ) 3.28 Forfeited or Expired (796,533 ) 7.27 Outstanding at September 30, 2017 12,134,640 $ 6.70 Vested and expected to vest at September 30, 2017 7,227,274 $ 7.64 Exercisable at September 30, 2017 4,056,699 $ 9.17 Upon the exercise of stock options, we issue new shares of our common stock. As of September 30, 2017 , 4,338,750 options issued to employees are unvested, performance-based options. Restricted Stock Certain employees and directors have been awarded restricted stock under our equity incentive plans. The time-vesting restricted stock awards vest primarily over a period of three years. The following table summarizes restricted share activity for the nine months ended September 30, 2017 : Number of shares Weighted average grant date fair value Outstanding at December 31, 2016 1,524,884 $ 7.07 Granted 1,171,575 5.73 Vested (513,236 ) 6.01 Forfeited (133,638 ) 5.56 Outstanding at September 30, 2017 2,049,585 $ 6.67 As of September 30, 2017 , 435,000 shares of restricted stock issued to employees are unvested, performance-based shares. Stock-Based Compensation Expense We incurred $3.4 million and $3.7 million of stock-based compensation expense related to equity incentive grants during the three months ended September 30, 2017 and 2016 , respectively, and $10.7 million and $10.6 million during the nine months ended September 30, 2017 and 2016 , respectively. The following table reflects stock-based compensation expense for the three and nine months ended September 30, 2017 and 2016 : Three months ended September 30, Nine months ended September 30, (in thousands) 2017 2016 2017 2016 Cost of goods sold $ 37 $ 39 $ 125 $ 53 Research and development 468 558 1,529 2,143 Selling, general and administrative 2,867 3,120 9,053 8,367 Total stock-based compensation expense $ 3,372 $ 3,717 $ 10,707 $ 10,563 Stock-based compensation costs capitalized as part of inventory were immaterial for the three and nine months ended September 30, 2017 and 2016 . The fair value of stock options granted is estimated at the date of grant using the Black-Scholes pricing model. The expected term of options granted is derived from historical data, the expected vesting period and the full contractual term. Expected volatility is based on the historical volatility of our common stock. The risk-free interest rate is based on the U.S. Treasury Yield for a period consistent with the expected term of the option in effect at the time of the grant. We have assumed no expected dividend yield, as dividends have never been paid to stock or option holders and will not be paid for the foreseeable future. The weighted average grant date fair value of stock options granted during the three months ended September 30, 2017 and 2016 was $5.14 and $5.94 per share, respectively, and during the nine months ended September 30, 2017 and 2016 was $3.91 and $4.54 per share, respectively. We used historical information to estimate forfeitures of stock options. As of September 30, 2017 , there was $10.7 million and $6.3 million of total unrecognized compensation cost related to non-vested stock options and restricted stock, respectively, which is expected to be recognized over weighted-average periods of 1.7 years and 1.6 years , respectively. These amounts do not include 4,338,750 unvested options and 435,000 shares of unvested restricted stock as of September 30, 2017 which are performance-based and vest upon achievement of certain corporate milestones. Stock-based compensation for these awards will be measured and recorded if and when it is probable that the milestone will be achieved.

License Agreements

License Agreements	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
License Agreements	LICENSE AGREEMENTS In November 2005, we entered into a license agreement with Panion & BF Biotech, Inc., or Panion. Under the license agreement, we acquired the exclusive worldwide rights, excluding certain Asian-Pacific countries, for the development and marketing of ferric citrate. To date, we have paid an aggregate of $11.6 million of milestone payments to Panion. In addition, Panion is eligible to receive royalty payments based on a mid-single digit percentage of net sales of ferric citrate in the licensed territory, as well as a manufacturing fee for product manufactured for use in the licensed territory. In September 2007, we entered into a Sublicense Agreement with JT and Torii, under which JT and Torii obtained the exclusive sublicense rights for the development and commercialization of ferric citrate in Japan. JT and Torii are responsible for the future development and commercialization costs in Japan. Effective June 8, 2009, we entered into an Amended and Restated Sublicense Agreement, or Revised Agreement, with JT and Torii, which, among other things, provided for the elimination of all significant on-going obligations under the Sublicense Agreement. In January 2014, JT and Torii received manufacturing and marketing approval of ferric citrate from the Japanese Ministry of Health, Labour and Welfare. Ferric citrate launched in May 2014 and is marketed in Japan by Torii under the brand name Riona and is indicated as an oral treatment for the improvement of hyperphosphatemia in patients with CKD. Under the terms of the Revised Agreement, we receive royalty payments based on a tiered double-digit percentage of net sales of Riona in Japan escalating up to the mid-teens and may also receive up to an additional $55.0 million upon the achievement of certain annual net sales milestones. In accordance with our revenue recognition policy, royalty revenues are recognized in the quarter that JT and Torii provide their written report and related information to us regarding sales of Riona, which generally will be one quarter following the quarter in which the underlying sales by JT and Torii occurred. For the three months ended September 30, 2017 and 2016 , we recorded $1.4 million and $1.3 million , respectively, in license revenue related to royalties earned on net sales of Riona in Japan. For the nine months ended September 30, 2017 and 2016 , we recorded $3.7 million and $3.5 million , respectively, in license revenue related to royalties earned on net sales of Riona in Japan. We record the associated mid-single digit percentage of net sales royalty expense due Panion, the licensor of ferric citrate, in the same period as the royalty revenue from JT and Torii is recorded. For each of the three months ended September 30, 2017 and 2016 , we recorded $0.8 million in license expense related to royalties due to the licensor of ferric citrate relating to sales of Riona in Japan. For the nine months ended September 30, 2017 and 2016 , we recorded $2.2 million and $2.1 million , respectively, in license expense related to royalties due to the licensor of ferric citrate relating to sales of Riona in Japan.

Accounts Payable And Accrued Ex

Accounts Payable And Accrued Expenses	9 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
Accounts Payable And Accrued Expenses	ACCOUNTS PAYABLE AND ACCRUED EXPENSES Accounts payable and accrued expenses consists of the following at September 30, 2017 and December 31, 2016 : (in thousands) September 30, 2017 December 31, 2016 Accounts payable $ 6,799 $ 2,225 Accrued compensation and related liabilities 6,377 8,190 Accrued professional, license, and other fees and expenses 8,106 6,159 Accrued commercial rebates, fees and product returns 15,256 4,616 Total accounts payable and accrued expenses $ 36,538 $ 21,190

Debt

Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt	DEBT In October 2015, we completed the sale of $125 million of Notes due 2020, in a private placement, or the Private Placement, to funds managed by Baupost pursuant to a Notes Purchase Agreement dated October 14, 2015. The Notes were issued under an Indenture, or the Indenture, dated as of October 15, 2015, with The Bank of New York Mellon Trust Company, N.A. as trustee, or the Trustee. The Indenture subjects us to certain financial and business covenants and contains restrictions on the payments of cash dividends. The Indenture contains customary terms and events of default. If an event of default (other than certain events of bankruptcy, insolvency or reorganization involving us) occurs and is continuing, the Trustee by notice to us, or the holders of at least 25% in aggregate principal amount of the outstanding Notes by written notice to us and the Trustee, may declare 100% of the principal on all of the Notes to be due and payable. Upon such a declaration of acceleration, such principal will be due and payable immediately. Upon the occurrence of certain events of bankruptcy, insolvency or reorganization involving us, 100% of the principal on all of the Notes will become due and payable automatically. Further, in connection with the Private Placement, we entered into a Registration Rights Agreement with the purchasers of the Notes, or the Registration Rights Agreement, pursuant to which we agreed to (i) file a registration statement, or the Resale Registration Statement with the Securities and Exchange Commission, or SEC, covering the resale of the Notes and the underlying common stock into which the Notes are convertible upon the written request of Baupost, and (ii) use commercially reasonable efforts, subject to receipt of necessary information from all the purchasers of the Notes, to cause the SEC to declare the Resale Registration Statement effective. Further, the Registration Rights Agreement permits Baupost to demand from time to time that we file a shelf Registration Statement pursuant to Rule 415 of the Securities Act from which any number of shelf takedowns may be conducted upon written request from Baupost. Finally, the Registration Rights Agreement affords Baupost certain piggyback registration rights. The Notes are convertible at the option of Baupost at an initial conversion rate of 267.3797 shares of our common stock per $1,000 principal amount, equal to a conversion price of $3.74 per share, which represents the last reported sale price of our stock on October 14, 2015. The conversion rate is subject to adjustment from time to time upon the occurrence of certain events. Further, upon the occurrence of certain fundamental changes involving us, Baupost may require us to repurchase for cash all or part of their Notes at a repurchase price equal to 100% of the principal amount of the Notes to be repurchased. At issuance, a portion of the Notes was contingently convertible into cash if our stockholders did not approve an increase in the number of authorized shares of our common stock by July 1, 2016. In accordance with accounting guidance for debt with a conversion option, we separated the conversion option from the debt instrument and accounted for it separately as a derivative liability, due to the Notes initially being partially convertible to cash at the option of Baupost. We allocated the proceeds between the debt component and the embedded conversion option (the derivative) by performing a valuation of the derivative as of the transaction date, which was determined based on the difference between the fair value of the Notes with the conversion option and the fair value of the Notes without the conversion option. The fair value of the derivative liability was recognized as a debt discount and the carrying amount of the convertible senior notes represented the difference between the proceeds from the issuance of the Notes and the fair value of the derivative liability on the date of issuance. The excess of the principal amount of the debt component over its carrying amount, or debt discount, was amortized to interest expense using the effective interest method over the expected life of the debt. We determined the expected life of the debt was equal to the period through July 1, 2016, as this represented the earliest point at which a portion of the Notes was initially contingently convertible into cash. Accordingly, for the nine months ended September 30, 2016 , approximately $34.2 million of interest expense was recognized related to the Notes, all of which was attributable to the amortization of the debt discount. Following our 2016 Annual Meeting of Stockholders held on May 25, 2016, we filed a certificate of amendment to our certificate of incorporation with the Secretary of State of the State of Delaware to increase the number of authorized shares of our common stock to allow for the full conversion of the Notes into our common stock. On April 10, 2017, we entered into the First Supplemental Indenture, or the First Supplement, to the Indenture. Under the terms of the First Supplement, the Notes issued under the Indenture were not convertible by the holders thereof until on or after June 8, 2017, except in connection with a “fundamental change” as defined in the Indenture. After June 8, 2017, the Notes are convertible entirely into shares of our common stock or cash depending upon the number of shares of our common stock authorized at the time of such conversion. At our 2017 Annual Meeting of Stockholders held on June 8, 2017, our stockholders ratified the filing and effectiveness of the certificate of amendment filed in May 2016. In addition, at the meeting our stockholders also approved a separate amendment to our certificate of incorporation to increase the number of authorized shares of our common stock to 230,000,000 shares. As a result, the full amount of the Notes is convertible into shares of our common stock. The holders of the Notes may, at their option, convert the Notes until the maturity date thereof. In accordance with accounting guidance for debt modifications and exchanges, we assessed the terms of the First Supplement and determined that it resulted in a modification. During the three months ended June 30, 2017, we separated the conversion option from the debt instrument and accounted for it separately as a derivative liability, due to the Notes being contingently convertible to cash at the option of Baupost per the terms of the First Supplement. We allocated the proceeds between the debt component and the embedded conversion option (the derivative) by performing a valuation of the derivative as of the date of the First Supplement, which was determined based on the difference between the fair value of the Notes with the conversion option and the fair value of the Notes without the conversion option. The fair value of the derivative liability was recognized as a debt discount and the carrying amount of the convertible senior notes represented the difference between the principal amount of the Notes and the fair value of the derivative liability on the date of the First Supplement. The excess of the principal amount of the debt component over its carrying amount, or debt discount, was amortized to interest expense using the effective interest method over the expected life of the debt. We determined the expected life of the debt was equal to the period through June 8, 2017, as this represented the point at which the Notes was contingently convertible into cash. In the nine months ended September 30, 2017 and 2016 , $63.0 million and $34.2 million , respectively, of interest expense was recognized related to the Notes. As of September 30, 2017 and December 31, 2016 , the balance of the Notes and the carrying value of the Notes was $125 million , and the fair value of the Notes was $237 million and $196 million , respectively.

Other Income (Expense), Net

Other Income (Expense), Net	9 Months Ended
	Sep. 30, 2017
Other Income and Expenses [Abstract]
Other Income (Expense), Net	OTHER INCOME (EXPENSE), NET The components of other income (expense), net are as follows: Three months ended September 30, Nine months ended September 30, (in thousands) 2017 2016 2017 2016 Interest income $ 240 $ 169 $ 475 $ 556 Other income (expense) 1 (19 ) (7 ) (7 ) Fair value adjustment to derivative liability — — 225 (4,718 ) $ 241 $ 150 $ 693 $ (4,169 ) The fair value adjustment to the derivative liability was recorded in connection with the Notes and related First Supplement. See Note 9 - Debt for additional information.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	COMMITMENTS AND CONTINGENCIES Commitments As of September 30, 2017 , our contractual obligations and commitments primarily consist of our obligations under non-cancelable leases, the Notes and various agreements with third parties, including selling, general and administrative, research and development and manufacturing agreements. Contingencies We accrue a liability for legal contingencies when we believe that it is both probable that a liability has been incurred and that we can reasonably estimate the amount of the loss. We review these accruals and adjust them to reflect the best information available at the time. To the extent new information is obtained and our views on the probable outcomes of claims, suits, assessments, investigations or legal proceedings change, changes in our accrued liabilities would be recorded in the period in which such determination is made. For the matters referenced below, a liability is not probable or the amount cannot be reasonably estimated and, therefore, an accrual has not been made. In addition, in accordance with the relevant authoritative guidance, for any matters in which the likelihood of material loss is at least reasonably possible, we will provide disclosure of the possible loss or range of loss. If a reasonable estimate cannot be made, however, we will provide disclosure to that effect. We expense legal costs as they are incurred. Four purported class action lawsuits have been filed against us and certain of our current and former officers (Gregory P. Madison, Scott A. Holmes, Ron Bentsur, and James Oliviero). Three of these actions were filed in the U.S. District Court for the Southern District of New York, captioned respectively Terrell Jackson v. Keryx Biopharmaceuticals, Inc., et al., No. 1:16-cv-06131, filed on August 2, 2016, Richard J. Erickson v. Keryx Biopharmaceuticals, Inc., et al. No. 1:16-cv-06218, filed on August 4, 2016, and Richard King v. Keryx Biopharmaceuticals, Inc., et al., No. 1:16-cv-06233, filed on August 5, 2016. The Jackson complaint purports to be brought on behalf of stockholders who purchased our common stock between February 25, 2016 and August 1, 2016, the Erickson complaint purports to be brought on behalf of stockholders who purchased our common stock between March 2, 2016 and July 29, 2016, and the King complaint purports to be brought on behalf of stockholders who purchased our common stock between February 25, 2016 and July 29, 2016. On August 26, 2016, the fourth complaint, captioned Tim Karth v. Keryx Biopharmaceuticals, Inc., et al., No. 1:16-cv-11745, was filed in the U.S. District Court for the District of Massachusetts, which complaint was subsequently amended. The Karth complaint purports to be brought on behalf of stockholders who purchased our common stock between May 8, 2013 and August 1, 2016. The Jackson, Erickson and King matters were transferred to the U.S. District Court for the District of Massachusetts on April 5, 2017. Each complaint generally alleges that we and certain of our current and former officers violated Sections 10(b) and/or 20(a) of the Exchange Act and Rule 10b-5 promulgated thereunder by making allegedly false and/or misleading statements concerning us and our business operations and future prospects in light of the August 1, 2016 announcement of an interruption in our supply of Auryxia. Two stockholder derivative complaints were also filed on December 16, 2016 against us and certain of our current and former officers (Gregory P. Madison, Scott A. Holmes, Ron Bentsur and James Oliviero), certain of our current directors (Kevin J. Cameron, Daniel P. Regan, Steven C. Gilman, Michael Rogers and John P. Butler) and our former directors (Michael P. Tarnok, Joseph Feczko, Jack Kaye and Wyche Fowler, Jr.), in the Superior Court of Massachusetts, one captioned Venkat Vara Prasad Malledi v. Keryx Biopharmaceuticals, Inc., et al., No. 16-3865 and one captioned James Anderson v. Keryx Biopharmaceuticals, Inc., et al., No. 16-3866. Each of these two complaints generally allege that the individual defendants breached their fiduciary duties owed to us, unjustly enriched themselves by their actions, abused their control positions with us, mismanaged us and wasted corporate assets since July 31, 2013 in light of our August 1, 2016 announcement by us of an interruption in the supply of the our product Auryxia. On June 27, 2017, the Superior Court granted the parties' motion to consolidate and stay the derivative litigations. All of the complaints seek unspecified damages, interest, attorneys’ fees, and other costs. We deny any allegations of wrongdoing and intend to vigorously defend against these lawsuits. There is no assurance, however, that we or the other defendants will be successful in our defense of either of these lawsuits or that insurance will be available or adequate to fund any settlement or judgment or the litigation costs of these actions. Moreover, we are unable to predict the outcome or reasonably estimate a range of possible losses at this time. A resolution of these lawsuits adverse to us or the other defendants, however, could have a material effect on our financial position and results of operations in the period in which the particular lawsuit is resolved.

Basis of Presentation and Sum17

Basis of Presentation and Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements were prepared in accordance with U.S. generally accepted accounting principles, or GAAP, for interim financial information and with the instructions to Form 10-Q and Article 10 of Regulation S-X. Accordingly, they may not include all of the information and footnotes required by GAAP for complete financial statements. All adjustments that are, in the opinion of management, of a normal recurring nature and are necessary for a fair presentation of these interim financial statements have been included. These interim condensed consolidated financial statements should be read in conjunction with the audited consolidated financial statements contained in our Annual Report on Form 10-K for the year ended December 31, 2016 . The year-end condensed consolidated balance sheet data was derived from audited financial statements, but does not include all disclosures required by GAAP. The results of operations for the three and nine months ended September 30, 2017 are not necessarily indicative of the results that may be expected for the entire fiscal year or any other interim period.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include our financial statements and those of our wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and judgments that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of these condensed consolidated financial statements and the reported amounts of revenues and expenses during the applicable reporting period. Actual results could differ from those estimates. Such differences could be material to these condensed consolidated financial statements.
Revenue Recognition	Revenue Recognition Our primary source of revenue during the reporting periods was product sales. We sell product to a limited number of major wholesalers, our Distributors, as well as certain pharmacies, or collectively, our Customers. Our Distributors resell the product to retail pharmacies for purposes of their reselling the product to fill patient prescriptions. In accordance with GAAP, our revenue recognition policy requires that (i) there is persuasive evidence that an arrangement exists between us and the Customer, (ii) delivery has occurred, (iii) collectability is reasonably assured, and (iv) the price is fixed or determinable. In the fourth quarter of 2016, we began to recognize revenue under the pull-through (ex-factory) method based on sales to our Customers as a result of our ability to reasonably estimate product returns based on our prior sales and product return history. Prior to the fourth quarter of 2016, we recognized revenue based on the resale of Auryxia for the purposes of filling patient prescriptions, and not based on initial sales from us to our Customers as we did not have sufficient history such that we could reliably estimate product returns based on sales to our Customers. As a result, prior to the fourth quarter of 2016, we deferred Auryxia revenue recognition until the earlier of the product being resold for purposes of filling patient prescriptions and the expiration of the right of return (twelve months after the expiration date of the product). The deferred revenue was recorded net of discounts, rebates, and chargebacks. We also deferred the related cost of product sales and recorded such amounts as finished goods inventory held by others, which was included in inventory on our condensed consolidated balance sheet, until revenue related to such product sales was recognized.
Basic and Diluted Net Loss Per Common Share	Basic and Diluted Net Loss Per Common Share Basic net loss per share is computed by dividing the losses allocable to common stockholders by the weighted average number of shares of common stock outstanding for the period. Diluted net loss per share does not reflect the effect of shares of common stock to be issued upon the exercise of stock options, as their inclusion would be anti-dilutive.
Concentrations of Credit Risk	Concentrations of Credit Risk We do not have significant off-balance-sheet risk or credit risk concentrations. We primarily maintain our cash and cash equivalents in deposit accounts and institutional money market funds. As of September 30, 2017 , approximately $25.9 million of our total $114 million cash and cash equivalents balance was invested in institutional money market funds. See Note 3 – Fair Value Measurements . Our accounts receivable, net at September 30, 2017 and December 31, 2016 represent amounts due to us from our Customers. We perform ongoing credit evaluations of our Customers and generally do not require collateral.
New Accounting Pronouncements	New Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board, or the FASB, or other standard setting bodies that we adopt as of the specified effective date. In May 2014, the FASB issued Accounting Standards Update, or ASU, No. 2014-09, Revenue from Contracts with Customers (Topic 606) , a comprehensive new standard which amends revenue recognition principles and provides a single set of criteria for revenue recognition among all industries. The new standard provides a five-step framework whereby revenue is recognized when promised goods or services are transferred to a customer at an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. The standard also requires enhanced disclosures pertaining to revenue recognition in both interim and annual periods. The standard is effective for interim and annual periods beginning after December 15, 2017 and allows for adoption using a full retrospective method, or a modified retrospective method. The FASB has subsequently issued amendments to ASU No. 2014-09 that have the same effective date and transition date of January 1, 2018. We expect to adopt these standards using the modified retrospective method. We have identified the customer contracts that are in the scope of these standards, including contracts with our distributors and specialty pharmacies, as well as contracts with third-party payers. We are in the process of reviewing the contracts to assess the potential impact of these standards. Prior to January 1, 2018, we plan to complete our review of the identified customer contracts as well as our license agreements to determine the impact that these standards will have on our financial position, results of operations and disclosures. In February 2016, the FASB issued ASU No. 2016-02, Leases . The new standard requires that all lessees recognize the assets and liabilities that arise from leases on the balance sheet and disclose qualitative and quantitative information about its leasing arrangements. The new standard will be effective for us on January 1, 2019. The adoption of this standard may have a material impact on our financial position as it may impact the amount of our assets and liabilities. We are currently evaluating the potential impact that this standard may have on our results of operations. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments . The new standard addresses eight specific cash flow issues with the objective of reducing the existing diversity in practice in how certain cash receipts and cash payments are presented and classified in the statement of cash flows. The new standard will be effective for us on January 1, 2018. This standard is not expected to have a material impact on our statement of cash flows upon adoption.

Basis of Presentation and Sum18

Basis of Presentation and Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Schedule of Provisions for Allowances and Accruals	Our U.S. Auryxia product sales for the three and nine months ended September 30, 2017 and 2016 were offset by provisions for allowances and accruals as set forth in the tables below. (in thousands) Three months ended Percent of gross Auryxia product sales Three months ended Percent of gross Auryxia product sales Gross Auryxia product sales $ 30,620 $ 8,711 Less provision for product sales allowances and accruals: Trade allowances 2,894 9 % 750 9 % Rebates, chargebacks and discounts 13,251 43 % 2,787 32 % Product returns 592 3 % — — Other incentives (1) 286 1 % 124 1 % Total 17,023 56 % 3,661 42 % Net U.S. Auryxia product sales $ 13,597 $ 5,050 (1) Includes co-pay assistance and voucher rebates. (in thousands) Nine months ended September 30, 2017 Percent of gross Nine months ended September 30, 2016 Percent of gross Gross Auryxia product sales $ 74,603 $ 29,896 Less provision for product sales allowances and accruals Trade allowances 7,122 10 % 3,451 12 % Rebates, chargebacks and discounts 27,365 37 % 7,008 23 % Product returns 870 1 % — — Other incentives (1) 1,028 1 % 492 2 % Total 36,385 49 % 10,951 37 % Net U.S. Auryxia product sales $ 38,218 $ 18,945 (1) Includes co-pay assistance and voucher rebates.
Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share	The following table presents amounts that were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect: (in thousands) September 30, 2017 September 30, 2016 Options to purchase common stock 12,135 8,823 Shares issuable upon conversion of convertible senior notes 33,422 33,422 45,557 42,245
Customer Who Represented 10% Or More Total Account Receivable	The following table sets forth customers who represented 10% or more of our total accounts receivable, net as of September 30, 2017 and December 31, 2016 . September 30, 2017 December 31, 2016 McKesson Corporation 24 % 31 % Fresenius Medical Care Rx 23 % 22 % AmerisourceBergen Drug Corporation 21 % 23 % Cardinal Health, Inc. 18 % 11 % DaVita Rx 9 % 10 %

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements of Financial Assets	The following table provides the fair value measurements of applicable financial assets as of September 30, 2017 and December 31, 2016 : Financial assets at fair value Financial assets at fair value (in thousands) Level 1 Level 2 Level 3 Level 1 Level 2 Level 3 Assets: Cash equivalents (1) $ 25,911 $ — $ — $ 107,084 $ — $ — Total assets $ 25,911 $ — $ — $ 107,084 $ — $ — (1) Cash equivalents as of September 30, 2017 and December 31, 2016 consisted of institutional money market funds. The carrying value of our money market funds approximates fair value due to their short-term maturities.

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2017
Inventory Disclosure [Abstract]
Summary of Inventories	Inventory consists of the following at September 30, 2017 and December 31, 2016 : (in thousands) September 30, 2017 December 31, 2016 Raw materials $ 520 $ 418 Work in process 22,330 11,430 Finished goods 3,160 833 Total inventory $ 26,010 $ 12,681

Stock-Based Compensation Expe21

Stock-Based Compensation Expense (Tables)	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Summary of Stock Option Activity	The following table summarizes stock option activity for the nine months ended September 30, 2017 : Number of shares Weighted average exercise price Outstanding at December 31, 2016 8,677,998 $ 7.28 Granted 4,581,750 5.46 Exercised (328,575 ) 3.28 Forfeited or Expired (796,533 ) 7.27 Outstanding at September 30, 2017 12,134,640 $ 6.70 Vested and expected to vest at September 30, 2017 7,227,274 $ 7.64 Exercisable at September 30, 2017 4,056,699 $ 9.17
Summary of Restricted Share Activity	The following table summarizes restricted share activity for the nine months ended September 30, 2017 : Number of shares Weighted average grant date fair value Outstanding at December 31, 2016 1,524,884 $ 7.07 Granted 1,171,575 5.73 Vested (513,236 ) 6.01 Forfeited (133,638 ) 5.56 Outstanding at September 30, 2017 2,049,585 $ 6.67
Stock Based Compensation Expense	The following table reflects stock-based compensation expense for the three and nine months ended September 30, 2017 and 2016 : Three months ended September 30, Nine months ended September 30, (in thousands) 2017 2016 2017 2016 Cost of goods sold $ 37 $ 39 $ 125 $ 53 Research and development 468 558 1,529 2,143 Selling, general and administrative 2,867 3,120 9,053 8,367 Total stock-based compensation expense $ 3,372 $ 3,717 $ 10,707 $ 10,563

Accounts Payable And Accrued 22

Accounts Payable And Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2017
Payables and Accruals [Abstract]
Schedule of Accounts Payable and Accrued Expenses	Accounts payable and accrued expenses consists of the following at September 30, 2017 and December 31, 2016 : (in thousands) September 30, 2017 December 31, 2016 Accounts payable $ 6,799 $ 2,225 Accrued compensation and related liabilities 6,377 8,190 Accrued professional, license, and other fees and expenses 8,106 6,159 Accrued commercial rebates, fees and product returns 15,256 4,616 Total accounts payable and accrued expenses $ 36,538 $ 21,190

Other Income (Expense), Net (Ta

Other Income (Expense), Net (Tables)	9 Months Ended
	Sep. 30, 2017
Other Income and Expenses [Abstract]
Schedule of Other Income (Expense)	The components of other income (expense), net are as follows: Three months ended September 30, Nine months ended September 30, (in thousands) 2017 2016 2017 2016 Interest income $ 240 $ 169 $ 475 $ 556 Other income (expense) 1 (19 ) (7 ) (7 ) Fair value adjustment to derivative liability — — 225 (4,718 ) $ 241 $ 150 $ 693 $ (4,169 )

Basis of Presentation and Sum24

Basis of Presentation and Summary of Significant Accounting Policies - Schedule of Provisions for Allowances and Accruals (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Allowance for Sales Return and Doubtful Accounts [Line Items]
Gross Auryxia product sales	$ 30,620	$ 8,711	$ 74,603	$ 29,896
Provision for product sales allowances and accruals	17,023	3,661	36,385	10,951
Net U.S. Auryxia product sales	$ 13,597	$ 5,050	$ 38,218	$ 18,945
Provision for product sales allowances and accruals, percentage	56.00%	42.00%	49.00%	37.00%
Trade allowances
Allowance for Sales Return and Doubtful Accounts [Line Items]
Provision for product sales allowances and accruals	$ 2,894	$ 750	$ 7,122	$ 3,451
Provision for product sales allowances and accruals, percentage	9.00%	9.00%	10.00%	12.00%
Rebates, chargebacks and discounts
Allowance for Sales Return and Doubtful Accounts [Line Items]
Provision for product sales allowances and accruals	$ 13,251	$ 2,787	$ 27,365	$ 7,008
Provision for product sales allowances and accruals, percentage	43.00%	32.00%	37.00%	23.00%
Product returns
Allowance for Sales Return and Doubtful Accounts [Line Items]
Provision for product sales allowances and accruals	$ 592	$ 0	$ 870	$ 0
Provision for product sales allowances and accruals, percentage	3.00%	0.00%	1.00%	0.00%
Other Incentives
Allowance for Sales Return and Doubtful Accounts [Line Items]
Provision for product sales allowances and accruals	$ 286	$ 124	$ 1,028	$ 492
Provision for product sales allowances and accruals, percentage	1.00%	1.00%	1.00%	2.00%

Basis of Presentation and Sum25

Basis of Presentation and Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Provision for product sales allowances and accruals	$ 17,023		$ 3,661	$ 36,385	$ 10,951
Money market funds	25,900			25,900
Cash and cash equivalents	113,999		132,172	113,999	132,172	$ 111,810	$ 200,290
Trade allowances
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Provision for product sales allowances and accruals	2,894		750	7,122	3,451
Trade allowances | Restatement Adjustment
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Provision for product sales allowances and accruals		$ 500
Rebates, chargebacks and discounts
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Provision for product sales allowances and accruals	$ 13,251		$ 2,787	$ 27,365	$ 7,008
Rebates, chargebacks and discounts | Restatement Adjustment
Basis Of Presentation And Summary Of Significant Accounting Policies [Line Items]
Provision for product sales allowances and accruals		$ (500)

Basis of Presentation and Sum26

Basis of Presentation and Summary of Significant Accounting Policies - Stock Excluded From Calculation (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Option outstanding, not included in computation of net loss per share amount (in shares)	45,557	42,245
Options to purchase common stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Option outstanding, not included in computation of net loss per share amount (in shares)	12,135	8,823
Shares issuable upon conversion of convertible senior notes
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Option outstanding, not included in computation of net loss per share amount (in shares)	33,422	33,422

Basis of Presentation and Sum27

Basis of Presentation and Summary of Significant Accounting Policies - Customer Who Represented 10% Or More Total Account Receivable (Detail) - Accounts Receivable, net - Customer Concentration Risk	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
McKesson Corporation
Concentration Risk [Line Items]
Concentration risk percentage	24.00%	31.00%
Fresenius Medical Care Rx
Concentration Risk [Line Items]
Concentration risk percentage	23.00%	22.00%
AmerisourceBergen Drug Corporation
Concentration Risk [Line Items]
Concentration risk percentage	21.00%	23.00%
Cardinal Health, Inc.
Concentration Risk [Line Items]
Concentration risk percentage	18.00%	11.00%
DaVita Rx
Concentration Risk [Line Items]
Concentration risk percentage	9.00%	10.00%

Fair Value Measurements of Fina

Fair Value Measurements of Financial Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Level 1
Assets:
Total assets	$ 25,911	$ 107,084
Level 2
Assets:
Total assets	0	0
Level 3
Assets:
Total assets	0	0
Cash Equivalents | Level 1
Assets:
Total assets	25,911	107,084
Cash Equivalents | Level 2
Assets:
Total assets	0	0
Cash Equivalents | Level 3
Assets:
Total assets	$ 0	$ 0

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended
	Oct. 31, 2015	Sep. 30, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Convertible debt, fair value disclosures		$ 237	$ 196
Convertible Senior Notes, due 2020
Debt Instrument [Line Items]
Proceeds from issuance of convertible senior notes	$ 125

Inventory - Summary of Inventor

Inventory - Summary of Inventories (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Inventory Disclosure [Abstract]
Raw materials	$ 520	$ 418
Work in process	22,330	11,430
Finished goods	3,160	833
Total inventory	$ 26,010	$ 12,681

Stockholders' Equity (Deficit)

Stockholders' Equity (Deficit) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholders’ equity (deficit)	$ 8,962		$ 8,962		$ (8,296)
Increase in stockholders' equity			17,300
Proceeds from issuance of common stock			75,722	$ 0
Reclassification of derivative liability to equity			62,735	51,404
Proceeds related to issuance of stock-based compensation and sock option exercises			10,700
Net loss	$ (23,498)	$ (41,696)	$ (133,011)	$ (127,311)

Stock-Based Compensation Expe32

Stock-Based Compensation Expense - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for the issuance of stock options (in shares)	1,966,235		1,966,235
Stock awards vesting period			3 years
Stock-based compensation expense related to equity incentive granted	$ 3,372	$ 3,717	$ 10,707	$ 10,563
Weighted average grant date fair value of stock options granted (in dollars per shares)	$ 5.14	$ 5.94	$ 3.91	$ 4.54
Total unrecognized compensation cost related to non-vest stock options	$ 10,700		$ 10,700
Non-vested Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average recognition periods for unrecognized compensation cost			1 year 8 months 12 days
Non-vested Stock Options | Unvested Performance-Based Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options (in shares)	4,338,750		4,338,750
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock issued (in shares)	2,049,585		2,049,585		1,524,884
Total unrecognized compensation cost related to restricted stock	$ 6,300		$ 6,300
Weighted average recognition periods for unrecognized compensation cost			1 year 7 months 24 days
Restricted Stock | Performance-based and vest upon achievement of certain corporate milestones
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restricted stock issued (in shares)	435,000		435,000

Stock-Based Compensation Expe33

Stock-Based Compensation Expense - Summary of Stock Option Activity (Detail) - Un-vested, Performance-Based Options	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Number of shares
Outstanding at beginning of period (in shares) | shares	8,677,998
Granted (in shares) | shares	4,581,750
Exercised (in shares) | shares	(328,575)
Forfeited or Expired (in shares) | shares	(796,533)
Outstanding at end of period (in shares) | shares	12,134,640
Vested and expected to vest at period end (in shares) | shares	7,227,274
Exercisable at period end (in shares) | shares	4,056,699
Weighted-average exercise price
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 7.28
Granted (in dollars per share) | $ / shares	5.46
Exercised (in dollars per share) | $ / shares	3.28
Forfeited and Expired (in dollars per share) | $ / shares	7.27
Outstanding at end of period (in dollars per share) | $ / shares	6.70
Vested and expected to vest at period end (in dollars per share) | $ / shares	7.64
Exercisable at period end (in dollars per share) | $ / shares	$ 9.17

Stock-Based Compensation Expe34

Stock-Based Compensation Expense - Summary of Restricted Share Activity (Detail) - Restricted Stock	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Number of shares
Outstanding at beginning of period (in shares) | shares	1,524,884
Granted (in shares) | shares	1,171,575
Vested (in shares) | shares	(513,236)
Forfeited (in shares) | shares	(133,638)
Outstanding at end of period (in shares) | shares	2,049,585
Weighted average grant date fair value
Outstanding at beginning of period (in dollars per share) | $ / shares	$ 7.07
Granted (in dollars per share) | $ / shares	5.73
Vested (in dollars per share) | $ / shares	6.01
Forfeited (in dollars per share) | $ / shares	5.56
Outstanding at end of period (in dollars per share) | $ / shares	$ 6.67

Stock-Based Compensation Expe35

Stock-Based Compensation Expense - Stock Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 3,372	$ 3,717	$ 10,707	$ 10,563
Cost of goods sold
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	37	39	125	53
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	468	558	1,529	2,143
Selling, general and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Stock-based compensation expense	$ 2,867	$ 3,120	$ 9,053	$ 8,367

License Agreements - Additional

License Agreements - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		143 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Revised agreement potential milestone receivable			$ 55,000
License revenue	$ 1,399	$ 1,287	3,741	$ 3,505
License expense	$ 838	$ 772	$ 2,244	$ 2,103
Licensing Agreements
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Payments to acquire right for development and marketing of Ferric Citrate					$ 11,600

Accounts Payable And Accrued 37

Accounts Payable And Accrued Expenses (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Payables and Accruals [Abstract]
Accounts payable	$ 6,799	$ 2,225
Accrued compensation and related liabilities	6,377	8,190
Accrued professional, license, and other fees and expenses	8,106	6,159
Accrued commercial rebates, fees and product returns	15,256	4,616
Total accounts payable and accrued expenses	$ 36,538	$ 21,190

Debt - Additional Information (

Debt - Additional Information (Detail)	Oct. 14, 2015$ / shares	Oct. 31, 2015USD ($)	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)shares	Sep. 30, 2016USD ($)	Jun. 08, 2017shares	Dec. 31, 2016USD ($)shares
Debt Conversion [Line Items]
Notes, carrying amount			$ 125,000,000		$ 125,000,000			$ 125,000,000
Amortization of debt discount			$ 0	$ 0	$ 62,965,000	$ 34,226,000
Common stock, shares authorized (in shares) | shares			230,000,000		230,000,000		230,000,000	180,000,000
Notes, interest expense					$ 63,000,000
Notes, fair value			$ 237,000,000		$ 237,000,000			$ 196,000,000
Convertible Senior Notes, due 2020
Debt Conversion [Line Items]
Proceeds from issuance of convertible senior notes		$ 125,000,000
Minimum aggregate principal amount outstanding for declaration notice			25.00%		25.00%
Initial conversion rate	0.2673797
Conversion price, per share (in dollars per share) | $ / shares	$ 3.74
Repurchase price percentage of the principal amount					100.00%
Notes, carrying amount								$ 125,000,000
Convertible Senior Notes, due 2020 | Default (other than certain events of bankruptcy, insolvency or reorganization)
Debt Conversion [Line Items]
Redemption percentage					100.00%
Convertible Senior Notes, due 2020 | Events of bankruptcy, insolvency or reorganization
Debt Conversion [Line Items]
Redemption percentage					100.00%

Components of Other Income (Exp

Components of Other Income (Expense), Net (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Other Income and Expenses [Abstract]
Interest income	$ 240	$ 169	$ 475	$ 556
Other income (expense)	1	(19)	(7)	(7)
Fair value adjustment to derivative liability	0	0	225	(4,718)
Other income (expense), net	$ 241	$ 150	$ 693	$ (4,169)

Commitments and Contingencies -

Commitments and Contingencies - Narrative (Detail) - Pending Litigation	Dec. 16, 2016lawsuits	Sep. 30, 2017lawsuit
Loss Contingencies [Line Items]
Loss contingency, number of class action lawsuits		4
Filed US District Court, S. District New York
Loss Contingencies [Line Items]
Loss contingency, number of class action lawsuits		3
Breach of Fiduciary Duties
Loss Contingencies [Line Items]
New claims filed | lawsuits	2