Relypsa (RLYP) 10-Q 4 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Nov. 01, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q3
Trading Symbol	RLYP
Entity Registrant Name	Relypsa Inc
Entity Central Index Key	1,416,792
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		41,691,554

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 94,721	$ 30,264
Short-term investments	192,732	105,493
Restricted cash		268
Other receivables	1,123	425
Prepaid expenses and other current assets	6,467	2,756
Total current assets	295,043	139,206
Restricted cash	686	686
Property and equipment, net	8,571	3,467
Other assets	10,902	8,480
Total assets	315,202	151,839
Current liabilities:
Accounts payable	5,564	3,156
Accrued payroll and related expenses	7,063	4,393
Accrued liabilities	22,310	7,778
Deferred rent, current portion	27	1,156
Line of credit, current portion	298	432
Capital loan, current portion	4,213
Deferred revenue, current portion	27,165
Total current liabilities	66,640	16,915
Long-term liabilities:
Deferred rent, long-term	2,773	983
Line of credit	108	267
Capital loan	11,510	15,213
Deferred revenue, long-term	6,245
Total liabilities	$ 87,276	$ 33,378
Commitments and contingencies
Stockholders’ equity:
Preferred stock: $0.001 par value; 5,000 shares authorized at September 30, 2015 and December 2014; no shares issued and outstanding at September 30, 2015 and December 31, 2014
Common stock: $0.001 par value; 300,000 shares authorized at September 30, 2015 and December 31, 2014; 41,686 and 35,045 shares issued and outstanding at September 30, 2015 and December 31, 2014, respectively	$ 42	$ 35
Additional paid-in capital	654,005	424,175
Accumulated other comprehensive loss	(3)	(21)
Accumulated deficit	(426,118)	(305,728)
Total stockholders’ equity	227,926	118,461
Total liabilities and stockholders’ equity	$ 315,202	$ 151,839

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	41,686,000	35,045,000
Common stock, shares outstanding	41,686,000	35,045,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Income Statement [Abstract]
Collaboration and license revenue	$ 6,590		$ 6,590
Operating expenses:
Research and development	32,391	$ 11,647	66,798	$ 33,631
General and administrative	25,255	7,311	59,082	17,428
Total operating expenses	57,646	18,958	125,880	51,059
Loss from operations	(51,056)	(18,958)	(119,290)	(51,059)
Interest and other income, net	30	17	302	80
Interest expense	(442)	(494)	(1,402)	(1,262)
Net loss	$ (51,468)	$ (19,435)	$ (120,390)	$ (52,241)
Net loss per share, basic and diluted	$ (1.24)	$ (0.57)	$ (2.99)	$ (1.62)
Weighted average common shares used to compute net loss per share, basic and diluted	41,633,410	34,064,780	40,331,485	32,321,477

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (51,468)	$ (19,435)	$ (120,390)	$ (52,241)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net of tax	7	(30)	18	(24)
Total comprehensive loss	$ (51,461)	$ (19,465)	$ (120,372)	$ (52,265)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities
Net loss	$ (120,390)	$ (52,241)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	3,304	2,461
Stock-based compensation	12,850	6,296
Amortization of debt issuance costs	31	20
Amortization of debt discount	77	118
Accretion of final debt payment	441	333
Accrued interest on capital loan		71
Investment premium amortization		481
Loss on disposal of fixed assets	13
Changes in assets and liabilities:
Other receivables	(698)	(142)
Prepaid expenses and other current assets	(3,721)	461
Other assets and restricted cash	(2,154)	(2,146)
Accounts payable	2,408	(2,102)
Accrued and other liabilities	17,202	749
Deferred rent	661	(1,169)
Deferred revenue	33,410
Net cash used in operating activities	(56,566)	(46,810)
Investing activities
Purchases of investments	(283,614)	(141,283)
Proceeds from maturities of short-term investments	192,355	36,390
Proceeds from sales of short-term investments	3,001
Purchases of property and equipment	(7,384)	(1,442)
Net cash used in investing activities	(95,642)	(106,335)
Financing activities
Net proceeds from public offerings	213,711	94,607
Proceeds from common stock option exercises	2,414	1,473
Proceeds from purchases under the Employee Stock Purchase Plan	862
Net proceeds from capital loan		3,549
Repayment of capital loan		(1,530)
Repayment of equipment line of credit	(322)	(303)
Net cash provided by financing activities	216,665	97,796
Net increase (decrease) in cash and cash equivalents	64,457	(55,349)
Cash and cash equivalents at beginning of period	30,264	94,759
Cash and cash equivalents at end of period	94,721	39,410
Noncash investing and financing activities
Change in unrealized gain (loss) on investments	$ 18	(24)
Issuance of warrants in connection with capital loan		$ 234

Description of Business and Sig

Description of Business and Significant Accounting Policies	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Description of Business and Significant Accounting Policies	1. Description of Business and Significant Accounting Policies Organization Relypsa, Inc. (Relypsa or the Company) is a biopharmaceutical company dedicated to the development and commercialization of polymeric medicines to treat conditions that can be addressed in the gastrointestinal tract. On October 21, 2015, the U.S. Food and Drug Administration (FDA) approved Veltassa (patiromer) for oral suspension, the Company’s first medicine, for the treatment of hyperkalemia, a potentially life-threatening condition defined as abnormally elevated levels of potassium in the blood. The Company commenced operations on October 29, 2007. The Company’s principal operations are based in Redwood City, California and it operates in one segment. On October 28, 2014, Relypsa UK LTD was incorporated as a wholly-owned subsidiary of the Company. The information included in this quarterly report on Form 10-Q should be read in conjunction with the consolidated financial statements and notes thereto contained in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 filed with the U.S. Securities Exchange Commission (SEC). Offerings On December 4, 2014, the Company filed a shelf registration statement on Form S-3, which permitted: (a) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $250.0 million of its common stock, preferred stock, debt securities, warrants, purchase contracts and/or units; and (b) as part of the $250.0 million, the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $70.0 million of its common stock that could be sold under a sales agreement with Cantor Fitzgerald & Co in one or more at-the-market offerings. As of December 31, 2014, the Company had sold 514,710 shares pursuant to its at-the-market program at an average price of $32.17 per share for aggregate offering proceeds of $16.6 million and the Company received aggregate net proceeds of $16.1 million. During January and February 2015, the Company sold 1,549,910 shares pursuant to the Company’s at-the-market program at an average price of $34.48 per share for aggregate offering proceeds of $53.4 million, and the Company received aggregate net proceeds of $51.8 million. During the first quarter of 2015, the Company exhausted its current at-the-market offering in full. On March 3, 2015, the Company completed an underwritten public offering of 4,485,000 shares of common stock at an offering price of $38.50 per share for gross proceeds of $172.7 million. The Company received net proceeds from the offering of $161.9 million, after deducting the underwriting discounts and expenses. Basis of Presentation The unaudited interim condensed consolidated financial statements for the three and nine months ended September 30, 2015 and 2014 have been prepared on the same basis as the audited consolidated financial statements for the year ended December 31, 2014. The consolidated financial statements include all normal recurring adjustments, which the Company considers necessary for a fair presentation of our financial position at such dates and our operating results and cash flows for those periods. Results for the interim periods are not necessarily indicative of the results for the entire year. For more complete financial information, these condensed consolidated financial statements, and notes thereto, should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2014 included in our Annual Report on Form 10-K filed with the Securities and Exchange Commission, or SEC. Use of Estimates The preparation of these unaudited interim condensed consolidated financial statements in conformity with GAAP requires management to make estimates and judgments that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue, clinical trial accruals, manufacturing accruals, fair value of assets and liabilities, common stock, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates. Recent Accounting Pronouncements In April 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-03, Simplifying the Presentation of Debt Issuance Costs In May 2014, the FASB issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue From Contracts With Customers Liquidity The Company has never been profitable and, as of September 30, 2015, the Company has an accumulated deficit of $426.1 million. The Company may continue to incur substantial operating losses even after it begins to generate meaningful revenues from Veltassa. The Company will need additional funding to support future operating activities and adequate funding may not be available to the Company on acceptable terms, or at all. The Company’s failure to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition. The Company will need to generate significant revenues to achieve profitability and it may never do so. Revenue Recognition The Company has generated revenue from a collaboration and license agreement which includes non-refundable upfront license fees, milestones, contingent consideration payments based on the achievement of defined collaboration objectives, and royalties on sales of commercialized products. The Company accounts for multiple element arrangements, such as license and development agreements in which a customer may purchase several deliverables, in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Subtopic 605-25, “Multiple Element Arrangements.” The Company identifies the deliverables at the inception of the arrangement and each deliverable within a multiple deliverable revenue arrangement is accounted for as a separate unit of accounting if both the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in the Company’s control. The Company allocates revenue to each non-contingent element based on the relative selling price of each element. When applying the relative selling price method, the Company determines the selling price for each deliverable using vendor-specific objective evidence (VSOE) of selling price, if it exists, or third-party evidence (TPE) of selling price, if it exists. If neither VSOE nor TPE of selling price exist for a deliverable, the Company uses the best estimated selling price for that deliverable. Revenue allocated to each element is then recognized based on when the basic four revenue recognition criteria are met for each element. Revenue from nonrefundable, upfront license or technology access payments under license and collaborative arrangements that are dependent on future performance by the Company is recognized over the estimated period of the continuing performance obligation(s). Where a portion of non-refundable upfront fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as deferred revenue and recognized as revenue over the term of our estimated performance period under the agreement. The estimated performance periods are periodically reviewed based on the progress of the related program. The effect of any change made to an estimated performance period and, therefore revenue recognized, would occur on a prospective basis in the period that the change was made. The Company recognizes revenue from milestone payments when (i) the milestone event is substantive and its achievability was not reasonably assured at the inception of the agreement and (ii) the Company does not have ongoing performance obligations related to the achievement of the milestone. Milestone payments are considered substantive if all of the following conditions are met: the milestone payment (a) is commensurate with either our performance to achieve the milestone or the enhancement of the value of the delivered item or items as a result of a specific outcome resulting from our performance to achieve the milestone, (b) relates solely to past performance, and (c) is reasonable relative to all of the deliverables and payment terms (including other potential milestone consideration) within the arrangement. The Company recognizes revenue from upfront payments over the period of significant involvement under the related agreements unless the fee is in exchange for products delivered or services rendered that represent the culmination of a separate earnings process and no further performance obligation exists under the contract. The Company recognizes milestone payments as revenue upon the achievement of specified milestones only if (1) the milestone payment is non-refundable, (2) substantive effort is involved in achieving the milestone, (3) the amount of the milestone is reasonable in relation to the effort expended or the risk associated with achievement of the milestone, and (4) the milestone is at risk for both parties. If any of these conditions are not met, the milestone payment is included in the allocation of arrangement consideration, which may result in the deferral of the revenue until the underlying remaining performance obligations are completed. Research and Development Expenses Research and development costs are charged to expense as incurred and consist of costs incurred to further the Company’s research and development activities including salaries and related employee benefits, costs associated with clinical trials, costs related to pre-commercialization manufacturing activities such as manufacturing process validation activities and the manufacturing of commercial supply prior to approval, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers and contract research and manufacturing organizations that conduct certain research and development activities on behalf of the Company. Net Loss per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per common share is calculated by dividing the net loss by the weighted-average number of common stock equivalents outstanding for the period using the treasury stock method. The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per common share attributable to common stockholders for the periods presented as the effect of including such securities would be antidilutive (in thousands): September 30, 2015 2014 Warrants to purchase common stock 15 56 Options to purchase common stock 4,913 3,858 Restricted stock units 350 130 Common stock subject to repurchase 1 3 5,279 4,047

Fair Value Measurements

Fair Value Measurements	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	2. Fair Value Measurements Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value should maximize the use of observable inputs and minimize the use of unobservable inputs. There is a three-level valuation hierarchy for disclosure of fair value measurements, as follows: Level 1 – Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2 – Inputs (other than quoted market prices included in Level 1) that are either directly or indirectly observable, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the instrument’s anticipated life. Level 3 – Unobservable inputs that are supported by little or no market activity and reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuation technique and the risk inherent in the inputs to the model. A financial instrument’s categorization within the valuation hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The following tables set forth the fair value of the Company’s financial instruments that were measured at fair value on a recurring basis as of September 30, 2015 and December 31, 2014 (in thousands): Level 1 Level 2 Level 3 Total September 30, 2015 Financial assets: Money market funds $ 54,312 $ — $ — $ 54,312 Corporate bonds — 87,208 — 87,208 Agency bonds — 85,776 — 85,776 Commercial paper — 56,843 — 56,843 Total financial assets $ 54,312 $ 229,827 $ — $ 284,139 Liabilities: Contingent put option liability $ — $ — $ 200 $ 200 Total liabilities $ — $ — $ 200 $ 200 Level 1 Level 2 Level 3 Total December 31, 2014 Financial assets: Money market funds $ 10,202 $ — $ — $ 10,202 Corporate bonds — 71,763 — 71,763 Agency bonds — 15,162 — 15,162 Commercial paper — 30,846 — 30,846 Total financial assets $ 10,202 $ 117,771 $ — $ 127,973 Liabilities: Contingent put option liability $ — $ — $ 233 $ 233 Total liabilities $ — $ — $ 233 $ 233 As of September 30, 2015, the Company’s Level 3 liability is comprised of a contingent put option liability. The following table sets forth a summary of the changes in the estimated fair value of the Company’s contingent put option, which are measured at fair value on a recurring basis (in thousands): Balance as of December 31, 2014 $ 233 Change in fair value included in other income (expense) (33 ) Balance as of September 30, 2015 $ 200 Where quoted prices are available in an active market, securities are classified as Level 1. The Company classifies money market funds as Level 1. When quoted market prices are not available for the specific security, then the Company estimates fair value by using benchmark yields, reported trades, broker/dealer quotes, and issuer spreads; these securities are classified as Level 2. The Company classifies corporate bonds, commercial paper, agency bonds and certificates of deposit as Level 2. In certain cases where there is limited activity or less transparency around inputs to valuation, securities are classified as Level 3. The Company classified a contingent put option liability as a Level 3 liability. See Note 5 “Borrowings,” for further description. The fair value of the contingent put option liability was determined by using a risk-neutral valuation model, wherein the fair value of the underlying debt facility is estimated both with and without the presence of the default provisions, holding all other assumptions constant. The resulting difference between the two estimated fair values is the estimated fair value of the default provisions, or the contingent put option. The fair value of the underlying debt facility is estimated by calculating the expected cash flows in consideration of an estimated probability of default and expected recovery rate in default, and discounting such cash flows back to the reporting date using a risk-free rate. The carrying value of the underlying debt facility or capital loan approximates fair value. The carrying values of the Company’s financial instruments, such as cash equivalents, other receivables, accounts payable, accrued liabilities and line of credit approximate fair value due to the short-term nature of these items. There were no transfers between Level 1, Level 2, and Level 3 during the periods presented.

Cash, Cash Equivalents, and Sho

Cash, Cash Equivalents, and Short-Term Investments	9 Months Ended
	Sep. 30, 2015
Cash Cash Equivalents And Short Term Investments [Abstract]
Cash, Cash Equivalents, and Short-Term Investments	3. Cash, Cash Equivalents, and Short-Term Investments The following is a summary of cash, cash equivalents, and short-term investments (in thousands): Amortized Gross Gross Estimated September 30, 2015 Cash and money market funds $ 57,626 $ — $ — $ 57,626 Corporate bonds 87,235 6 (33 ) 87,208 Agency bonds 85,766 13 (3 ) 85,776 Commercial paper 56,829 14 — 56,843 Total financial assets $ 287,456 $ 33 $ (36 ) $ 287,453 Reported as: Cash and cash equivalents $ 94,721 Short-term Investments 192,732 $ 287,453 Amortized Gross Gross Estimated December 31, 2014 Cash and money market funds $ 17,986 $ — $ — $ 17,986 Corporate bonds 71,794 2 (33 ) 71,763 Agency bonds 15,163 2 (3 ) 15,162 Commercial paper 30,835 11 — 30,846 Total financial assets $ 135,778 $ 15 $ (36 ) $ 135,757 Reported as: Cash and cash equivalents $ 30,264 Short-term investments 105,493 $ 135,757 For the nine months ended September 30, 2015 and the year ended December 31, 2014, there were no realized gains or losses on the available-for-sale securities. All of the Company’s available-for-sale securities are subject to a periodic impairment review. The Company considers a debt security to be impaired when its fair value is less than its carrying cost, in which case the Company would further review the investment to determine whether it is other-than-temporarily impaired. When the Company evaluates an investment for other-than-temporary impairment, the Company reviews factors such as the length of time and extent to which fair value has been below cost basis, the financial condition of the issuer and any changes thereto, intent to sell, and whether it is more likely than not the Company will be required to sell the investment before the recovery of its cost basis. If an investment is other-than-temporarily impaired, the Company writes it down through earnings to its impaired value and establishes that as a new cost basis for the investment. The Company did not identify any of its available-for-sale securities as other-than-temporarily impaired in any of the periods presented. As of September 30, 2015, no investment was in a continuous unrealized loss position for more than one year, the unrealized losses were not due to change in credit risk and the Company believes that is more likely than not the investments will be held until maturity or a forecasted recovery of fair value.

Accrued Liabilities

Accrued Liabilities	9 Months Ended
	Sep. 30, 2015
Payables And Accruals [Abstract]
Accrued Liabilities	4. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): September 30, December 31, 2015 2014 Accrued contract manufacturing $ 21,359 $ 6,655 Accrued clinical trial expenses 329 41 Accrued accounts payable — 795 Accrued professional and consulting services 525 184 Other 97 103 $ 22,310 $ 7,778

Borrowings

Borrowings	9 Months Ended
	Sep. 30, 2015
Debt Disclosure [Abstract]
Borrowings	5. Borrowings Capital Loan On May 30, 2014, the Company entered into an Amended and Restated Loan and Security Agreement (the Amended Loan Agreement) with Oxford Finance LLC and Silicon Valley Bank to amend and restate in its entirety the Loan and Security Agreement, (the Original Agreement), dated January 31, 2013. Per the terms of the Amended Loan Agreement, upon closing, the Company immediately drew $15.0 million, of which approximately $11.0 million was used to repay the outstanding debt under the Original Agreement, and approximately $0.4 million was used to satisfy the accrued portion of the final payment fee under the Original Agreement. Payments on the new $15.0 million loan will be interest only through January 2016, followed by 30 months of equal monthly payments of interest and principal. Due to the acceptance of the Company’s New Drug Application for Veltassa by the U.S. Food and Drug Administration in December 2014, the interest only payment period was extended until January 2016 and the Company may, at its option, draw an additional $20.0 million between July 1, 2015 and December 31, 2015. The Company will be required to make a final payment upon loan maturity of 8.5% of the amounts advanced and the unaccrued portion of the final payment fee under the Original Agreement in the amount of approximately $0.4 million. The interest rate for the first tranche is 7.40% and the interest rate on the second tranche will be equal to the greater of (i) the three month LIBOR rate plus 7.17% or (ii) 7.40%. On January 31, 2013, the Company issued warrants to purchase 54,437 shares of Series C-1 convertible preferred stock at an exercise price of $9.1848 per share in connection with the Original Agreement. Upon the closing of the Company’s initial public offering in November 2013, the warrants to purchase convertible preferred stock were converted to warrants to purchase common stock. 13,609 of these warrants were exercised during 2014, resulting in the net issuance of 7,808 shares of common stock. The remaining 40,828 warrants were exercised in the three months ended March 31, 2015, resulting in the net issuance of 29,690 shares of common stock. On May 30, 2014, the Company issued warrants to purchase 12,661 shares of common stock at an exercise price of $23.69 per share in connection with the first $15.0 million tranche under the Amended Loan Agreement. The fair value of the warrants was $0.2 million at the issuance date and was estimated using the Black-Scholes model with the following assumptions: a risk-free interest rate of 2.06%, a life of 7 years, a volatility factor of 91.67%, and no dividend yield. This amount is recorded as a debt discount, which will be amortized into interest expense over the repayment period. Interest expense was $0.5 million and $0.5 million for the three months ended September 30, 2015 and 2014 and $1.4 million and $1.2 million for the nine months ended September 30, 2015 and 2014 Upon an event of default, Oxford Finance LLC and Silicon Valley Bank have the option to accelerate repayment of the Amended Loan Agreement, including payment of any applicable prepayment charges, which range from 1%-3% of the outstanding loan balance and accrued interest, as well as a final payment fee. This option is considered a contingent put option liability, as the holder of the loan may exercise the option in the event of default, and is considered an embedded derivative, which must be valued and separately accounted for in the Company’s consolidated financial statements. As of September 30, 2015 the estimated fair value of the contingent put option liability was $0.2 million, which was determined by using a risk-neutral valuation model, see Note 2 for details on fair value measurement of the option. The Amended Loan Agreement includes customary operating but non-financial covenants, including limitations on the Company’s ability to incur additional indebtedness, issue dividends and transfer or encumber any collateral securing the debt, as well as a cross-default provision with regard to the Company’s equipment line of credit. As of September 30, 2015, principal of $15.0 million was outstanding under the Amended Loan Agreement, and the Company was in compliance with all required covenants.

Collaboration and License Agree

Collaboration and License Agreement	9 Months Ended
	Sep. 30, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreement	6. Collaboration and License Agreement In August 2015, the Company entered into a collaboration and license agreement (License Agreement) with VFMCRP, pursuant to which the Company granted to VFMCRP an exclusive, royalty-bearing license to the Company’s patents to develop and commercialize Veltassa outside the United States and Japan (Licensed Territory). The License Agreement sets forth the parties’ respective obligations for development, commercialization, regulatory and manufacturing and supply activities. In exchange for the Company entering into the License Agreement, VFMCRP agreed to pay the Company an upfront cash payment of $40.0 million. VFMCRP also agreed to pay the Company up to $125.0 million in milestone payments upon achievement of certain regulatory, commercial and net sales milestones and tiered, double digit royalties on net sales in the Licensed Territory. The Company identified the following deliverables per the terms of the License Agreement: 1) the granting of the licenses to VFMCRP; 2) working with VFMCRP on the submission of the Marketing Authorization Application (MAA); 3) performance of research and development activities; 4) participation in the joint steering committee (JSC) and joint development committee (JDC) and 5) manufacturing and supply activities. The Company considered the provisions of the multiple-element arrangement guidance in determining whether the delivered item(s) have standalone value. The Company concluded that the license and the work on the submission of the MAA, together have standalone value apart from the remaining deliverables and represents a separate unit of accounting. The remaining deliverables of the research and development activities, participation in committee activities, and manufacturing supply of Veltassa are also determined to have stand-alone value as VFMCRP or another third party could provide these services without the Company’s assistance. The arrangement consideration related to the manufacturing and supply activities will be recognized when delivered to VFMCRP and will be excluded from the allocation of arrangement consideration because the consideration and performance are contingent upon VFMCRP’s exercise of the option to purchase the services and that such services are priced at an estimated fair value. The upfront payment of $40.0 million was allocated to the 1) License and work on the submission of the MAA deliverable, 2) the research and development deliverable and 3) the committee participation deliverable using the relative estimated selling price method. The Company estimated the BESP of the license based on a probability-adjusted present value of the expected cash flows. The BESP for the other deliverables was estimated by using internal estimates of the cost to perform the specific services plus a normal profit margin for providing the services. The arrangement consideration allocated to the license and work on the submission of MAA will be recognized as collaboration and license revenue over the estimated performance period beginning upon the delivery of the license in August 2015. The amount allocated to the research and development activities and JSC and JDC participation are being recognized over the estimated performance period. For the three and nine months ended September 30, 2015, revenue of $6.6 million was recognized. The Company determined that one of the future contingent payments meets the definition of a milestone under the accounting guidance. Accordingly, revenue for the achievement of this milestone will be recognized in the period when the milestone is achieved. The remaining contingent payments would be triggered based on the performance of VFMCRP and are not considered to be milestones under the accounting guidance. The remaining contingent payments will be included in the allocation of arrangement consideration if and when achieved, resulting in an accounting treatment similar to the up-front payment. As of September 30, 2015, no milestones have been triggered under the License Agreement.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Lanxess Corporation On January 9, 2014, the Company entered into a Manufacturing and Supply Agreement (the Lanxess Supply Agreement) with Lanxess that supersedes an earlier agreement, the Memorandum of Understanding that was executed on November 27, 2012. Under the Lanxess Supply Agreement, Lanxess has agreed to manufacture and supply for commercial sale the active pharmaceutical ingredient (API) for Veltassa. The Lanxess Supply Agreement terminates on December 31, 2020 unless terminated earlier. The Company may extend the Lanxess Supply Agreement for an additional five years with notice. The Lanxess Supply Agreement may be terminated (i) by the Company with notice if it abandons development or manufacturing of Veltassa or fails to obtain FDA approval or the parties disagree regarding the feasibility or price of certain specification changes, or with notice at least 24 months in advance, which may be given after October 1, 2015, (ii) by Lanxess with notice if the Company fails to issue certain purchase orders, or with notice at least 24 months in advance, which may be given after October 1, 2015 and (iii) by either party with notice in the event of certain delays by the other party in performing its material obligations, or with notice if the parties fail to timely agree on certain price terms beginning in September 2015. Under the Lanxess Supply Agreement, Lanxess is obligated to manufacture the Company’s commercial supply of API for Veltassa, and the Company is obligated to purchase from Lanxess such products manufactured, pursuant to the terms and conditions of the Lanxess Supply Agreement. During 2013 and 2014, the Company paid Lanxess for plant modifications that are required to support the manufacturing scale up of API for Veltassa in anticipation of commercial launch. These payments are recorded in other assets and are being amortized to research and development expenses in accordance with the period over which the Company expects to derive future economic value. Upon receiving FDA approval, the amortization cost will no longer be recognized as a research and development cost expense, but as part of the cost basis of inventory. DPx Fine Chemicals On May 14, 2014, the Company entered into a Manufacturing and Supply Agreement (the DPx Supply Agreement) with DPx Fine Chemicals Austria GmbH & Co KG (DPx Fine Chemicals), formerly DSM Fine Chemicals Austria NFG GMBH & Co. KG. Under the DPx Supply Agreement, DPx Fine Chemicals has agreed to manufacture and supply for commercial sale the API for Veltassa. Under the DPx Supply Agreement, the Company is obligated to make certain minimum purchases of API. The DPx Supply Agreement may be terminated (i) by the Company with notice if it abandons development or commercialization of Veltassa or fails to obtain FDA approval, or with 12 months’ notice and without cause after DPx Fine Chemicals’ manufacture and release of certain quantity of API; (ii) by DPx Fine Chemicals within 24 months’ notice and without cause after its manufacture and release of a certain quantity of API; and (iii) by either party with notice for the other party’s uncured material breach, insolvency, liquidation, bankruptcy or dissolution. DPx Fine Chemicals has agreed to make plant modifications under the DPx Supply Agreement and will be the exclusive owner of the purchased equipment. DPx Fine Chemicals may manufacture other products with the modified plant when not occupied by the API for Veltassa. Under the DPx Supply Agreement, the Company has agreed to reimburse DPx Fine Chemicals up to a specified amount for plant modifications. These payments are being recorded in other assets and upon being placed into service, these payments will be amortized to research and development expenses in accordance with the period over which the Company expects to derive future economic value. Upon receiving FDA approval, the amortization cost will no longer be recognized as a research and development cost expense, but as part of the cost basis of inventory. Patheon On September 5, 2014, the Company entered into a multi-year supply agreement (the Patheon Supply Agreement) with Patheon, Inc. (Patheon). Under the Patheon Supply Agreement, Patheon has agreed to manufacture and supply for commercial sale the bulk and finished drug product, referred to as Veltassa. The Company has agreed to supply API for Veltassa to Patheon for use in the manufacture and supply of the bulk and finished drug product, and has agreed, subject to certain conditions, to purchase certain quantities of bulk and finished drug product from Patheon. The Patheon Supply Agreement may be terminated by the Company with written notice under certain provisions. Patheon has agreed to make facility improvements under the Patheon Supply Agreement and will be the exclusive owner of the purchased equipment and facility improvements. Patheon may manufacture other products with the facility improvements when not occupied by manufacturing Veltassa. Under the Patheon Supply Agreement, the Company has agreed to reimburse Patheon up to a specified amount for plant modifications. These payments are recorded in other assets and upon being placed in service, these payments will be amortized to research and development expenses in accordance with the period over which the Company expects to derive future economic value. Upon receiving FDA approval, the amortization cost will no longer be recognized as a research and development cost expense, but as part of the cost basis of inventory. The following are the combined future minimum payments under the terms of the Lanxess Supply Agreement, the DPx Supply Agreement, and the Patheon Supply Agreement as of September 30, 2015. These amounts are based on forecasts that include estimates of future market demand, quantity discounts and manufacturing efficiencies (in thousands): 2015 $ 22,471 2016 54,430 2017 70,563 2018 73,893 2019 28,658 Total future minimum payments $ 250,015 Operating Lease On June 26, 2014, the Company entered into a new lease (the Lease) for office and laboratory facilities in Redwood City, California that serves as the Company’s principal executive offices. The Lease commenced on February 1, 2015, following the landlord’s construction of certain improvements to the premises required under the Lease. The Lease terminates 10 years after the commencement and the Company has an option to extend the Lease to extend the Lease for an additional five years upon written notice to landlord. On July 10, 2015, the Company amended the Lease to expand the existing premises. The term of the expanded premises has the same termination date as the existing lease. The Lease contains rent escalation provisions over the term of the Lease. In accordance with the terms of the Lease the Company provided a security deposit in the form of a $0.7 million irrevocable letter of credit that is collateralized by a $0.7 million restricted deposit at the Company’s bank. The total rent obligation will be expensed ratably over the term of the Lease. The Company’s future minimum operating lease payments at September 30, 2015 are as follows (in thousands): 2015 $ 648 2016 3,761 2017 3,941 2018 4,034 2019 4,147 Thereafter 23,482 Total future minimum payments $ 40,013 The Company utilized a one-time allowance of $0.6 million for costs related to relocation, cabling, furniture, fixtures and equipment. The Company is entitled to begin to draw on an additional allowance of $2.2 million for certain move and tenant improvement related costs of which the Company used $0.8 million as of September 30, 2015. Amounts utilized of the additional allowance will increase future minimum operating lease payments.

Equity Compensation Plans and S

Equity Compensation Plans and Stock Based Compensation	9 Months Ended
	Sep. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Compensation Plans and Stock Based Compensation	8. Equity Compensation Plans and Stock-Based Compensation The Company adopted the 2007 Equity Incentive Plan (the 2007 Plan) which provides for the granting of stock options to employees, directors and consultants of the Company. Options granted under the 2007 Plan may be either incentive stock options or nonqualified stock options. Incentive stock options may be granted only to Company employees. Nonqualified stock options may be granted to Company employees, outside directors and consultants. Options under the 2007 Plan may be granted for periods of up to ten years and are exercisable immediately, subject to rights of repurchase by the Company, which lapse over the period the applicable shares vest. Employee options granted by the Company generally vest over four years. In November 2013, the Company’s stockholders approved the 2013 Equity Incentive Plan (the 2013 Plan). Options granted under the 2013 Plan may be granted for periods of up to ten years and are generally exercisable when vested. Any remaining shares available for future issuance under the 2007 Stock Plan are available for issuance under the 2013 Plan. The 2013 plan reserve will automatically increase annually from January 1, 2014 through January 1, 2023 by an amount equal to the smaller of: (a) 2,553,174 shares, (b) four percent of the number of shares of common stock issued and outstanding on the immediately preceding December 31, or (c) an amount determined by the Company's board of directors. As of September 30, 2015, a total of 1,007,241 shares were authorized for grant under the 2013 Plan. In June 2014, the Company’s board of directors approved the 2014 Employment Commencement Incentive Plan (the Inducement Plan), under which 1,000,000 shares were reserved. In July 2015, the Company’s board of directors approved an amendment to the Inducement Plan to increase the number of shares reserved for issuance by 1,000,000 shares. As of September 30, 2015, 1,298,650 shares of the Company’s common stock were subject to inducement grants that were issued pursuant to the Inducement Plan. The awards were made pursuant to the NASDAQ inducement grant exception as a component of the Company’s new hires’ employment compensation. The Company adopted the ESPP in November 2013 and in August 2014, the ESPP was initiated. As of September 30, 2015, the Company has reserved 587,438 shares of common stock for issuance under the ESPP, which permits eligible employees to purchase common stock at a discount through payroll deductions. The ESPP is a compensatory plan as defined by the authoritative guidance for stock compensation. As such stock-based compensation expense has been recorded during the three and nine months ended September 30, 2015. The following table summarizes option activity under the 2007 Plan, the 2013 Plan, the Inducement Plan, and related information (in thousands, except per share and contractual term amounts): Shares Shares Subject Weighted- Per Share Weighted- Aggregate (in years) Options outstanding at December 31, 2014 1,167 3,813 $ 11.05 Additional shares reserved under plan 2,402 — — Options granted (1,699 ) 1,699 30.12 Options exercised — (494) 4.88 Options forfeited 105 (105) 27.48 Restricted stock units granted (270 ) — — Restricted stock units canceled 3 — — Balances at September 30, 2015 1,708 4,913 $ 17.91 8.4 $ 28,867 Vested and expected to vest at September 30, 2015 4,686 $ 17.53 8.3 $ 28,513 Vested at September 30, 2015 1,734 $ 8.60 7.3 $ 19,113 The weighted-average grant-date estimated fair value of options granted during the three months ended September 30, 2015 and 2014 was $20.07 and $20.50, respectively. During the nine months ended September 30, 2015 and 2014, the weighted-average grant-date estimated fair value of options granted was $21.95 and $20.98 per share, respectively. The aggregate intrinsic value of options outstanding and exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the fair value of the Company’s common stock as of September 30, 2015. Stock-Based Compensation Expense Stock-based compensation expense included in the Company’s consolidated statements of operations is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Research and development: Employees $ 1,443 $ 440 $ 3,223 $ 934 Nonemployee consultants 609 761 3,001 2,939 General and administrative: Employees 3,045 1,032 6,626 2,410 Nonemployee consultants — — — 13 Total stock-based compensation expense $ 5,097 $ 2,233 $ 12,850 $ 6,296 As of September 30, 2015, the total unrecognized stock-based compensation expense related to stock options and the ESPP stock purchase plan was $52.2 million, which is expected to be recognized over an estimated weighted-average period of 3.19 years. The estimated grant date fair value of employee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Expected volatility 83% - 85% 92% 82% - 92% 87% - 109% Expected dividends 0% 0% 0% 0% Expected term (in years) 6 6 6 6 Risk-free rate 1.7% –1.9 % 1.8% –2.0 % 1.3% –1.9 % 1.8% –2.0 % The fair value of nonemployee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Expected volatility 83% - 91% 104% 83% -92% 104% -122% Expected dividends 0% 0% 0% 0% Expected term (in years) 6 – 8 7 – 9 6 – 9 6 – 9 Risk-free rate 1.5% – 1.8 % 2.0% – 2.4 % 1.5% – 2.1% 2.0% – 2.6% Restricted Stock Units During 2014 and 2015, the Company granted restricted stock unit (“RSUs”) awards subject to time-based vesting criteria from the 2013 Plan. RSUs subject to time-based vesting criteria entitle holders to receive shares of common stock at the end of a specified period of time. For RSUs subject to time-based vesting criteria, vesting is based on continuous employment or service of the holder to the Company. The fair value of RSUs is measured based on the number of shares granted and the closing market price of our common stock on the date of grant. The following table summarizes restricted stock unit activity for the nine months ended September 30, 2015 (in thousands, except per share amounts): Restricted Stock Units Number of Shares Weighted Average Nonvested at December 31, 2014 123 $ 26.85 Granted 270 28.00 Vested (40 ) 26.82 Canceled (3 ) 27.31 Nonvested at September 30, 2015 350 $ 27.82 The total unrecognized stock-based compensation expense related to non-vested RSUs at September 30, 2015, was $9.3 million, and is expected to be recognized over a weighted-average period of approximately 3.5 years.

Description of Business and S15

Description of Business and Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Offerings	Offerings On December 4, 2014, the Company filed a shelf registration statement on Form S-3, which permitted: (a) the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $250.0 million of its common stock, preferred stock, debt securities, warrants, purchase contracts and/or units; and (b) as part of the $250.0 million, the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $70.0 million of its common stock that could be sold under a sales agreement with Cantor Fitzgerald & Co in one or more at-the-market offerings. As of December 31, 2014, the Company had sold 514,710 shares pursuant to its at-the-market program at an average price of $32.17 per share for aggregate offering proceeds of $16.6 million and the Company received aggregate net proceeds of $16.1 million. During January and February 2015, the Company sold 1,549,910 shares pursuant to the Company’s at-the-market program at an average price of $34.48 per share for aggregate offering proceeds of $53.4 million, and the Company received aggregate net proceeds of $51.8 million. During the first quarter of 2015, the Company exhausted its current at-the-market offering in full. On March 3, 2015, the Company completed an underwritten public offering of 4,485,000 shares of common stock at an offering price of $38.50 per share for gross proceeds of $172.7 million. The Company received net proceeds from the offering of $161.9 million, after deducting the underwriting discounts and expenses.
Basis of Presentation	Basis of Presentation The unaudited interim condensed consolidated financial statements for the three and nine months ended September 30, 2015 and 2014 have been prepared on the same basis as the audited consolidated financial statements for the year ended December 31, 2014. The consolidated financial statements include all normal recurring adjustments, which the Company considers necessary for a fair presentation of our financial position at such dates and our operating results and cash flows for those periods. Results for the interim periods are not necessarily indicative of the results for the entire year. For more complete financial information, these condensed consolidated financial statements, and notes thereto, should be read in conjunction with the audited consolidated financial statements for the year ended December 31, 2014 included in our Annual Report on Form 10-K filed with the Securities and Exchange Commission, or SEC.
Use of Estimates	Use of Estimates The preparation of these unaudited interim condensed consolidated financial statements in conformity with GAAP requires management to make estimates and judgments that affect the amounts reported in the consolidated financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including those related to revenue, clinical trial accruals, manufacturing accruals, fair value of assets and liabilities, common stock, income taxes, and stock-based compensation. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In April 2015, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) 2015-03, Simplifying the Presentation of Debt Issuance Costs In May 2014, the FASB issued Accounting Standards Update (“ASU”) No. 2014-09, Revenue From Contracts With Customers
Liquidity	Liquidity The Company has never been profitable and, as of September 30, 2015, the Company has an accumulated deficit of $426.1 million. The Company may continue to incur substantial operating losses even after it begins to generate meaningful revenues from Veltassa. The Company will need additional funding to support future operating activities and adequate funding may not be available to the Company on acceptable terms, or at all. The Company’s failure to obtain sufficient funds on acceptable terms when needed could have a material adverse effect on the Company’s business, results of operations, and financial condition. The Company will need to generate significant revenues to achieve profitability and it may never do so.
Revenue Recognition	Revenue Recognition The Company has generated revenue from a collaboration and license agreement which includes non-refundable upfront license fees, milestones, contingent consideration payments based on the achievement of defined collaboration objectives, and royalties on sales of commercialized products. The Company accounts for multiple element arrangements, such as license and development agreements in which a customer may purchase several deliverables, in accordance with Financial Accounting Standards Board (FASB) Accounting Standards Codification (ASC) Subtopic 605-25, “Multiple Element Arrangements.” The Company identifies the deliverables at the inception of the arrangement and each deliverable within a multiple deliverable revenue arrangement is accounted for as a separate unit of accounting if both the following criteria are met: (1) the delivered item or items have value to the customer on a standalone basis and (2) for an arrangement that includes a general right of return relative to the delivered item(s), delivery or performance of the undelivered item(s) is considered probable and substantially in the Company’s control. The Company allocates revenue to each non-contingent element based on the relative selling price of each element. When applying the relative selling price method, the Company determines the selling price for each deliverable using vendor-specific objective evidence (VSOE) of selling price, if it exists, or third-party evidence (TPE) of selling price, if it exists. If neither VSOE nor TPE of selling price exist for a deliverable, the Company uses the best estimated selling price for that deliverable. Revenue allocated to each element is then recognized based on when the basic four revenue recognition criteria are met for each element. Revenue from nonrefundable, upfront license or technology access payments under license and collaborative arrangements that are dependent on future performance by the Company is recognized over the estimated period of the continuing performance obligation(s). Where a portion of non-refundable upfront fees or other payments received are allocated to continuing performance obligations under the terms of a collaborative arrangement, they are recorded as deferred revenue and recognized as revenue over the term of our estimated performance period under the agreement. The estimated performance periods are periodically reviewed based on the progress of the related program. The effect of any change made to an estimated performance period and, therefore revenue recognized, would occur on a prospective basis in the period that the change was made. The Company recognizes revenue from milestone payments when (i) the milestone event is substantive and its achievability was not reasonably assured at the inception of the agreement and (ii) the Company does not have ongoing performance obligations related to the achievement of the milestone. Milestone payments are considered substantive if all of the following conditions are met: the milestone payment (a) is commensurate with either our performance to achieve the milestone or the enhancement of the value of the delivered item or items as a result of a specific outcome resulting from our performance to achieve the milestone, (b) relates solely to past performance, and (c) is reasonable relative to all of the deliverables and payment terms (including other potential milestone consideration) within the arrangement. The Company recognizes revenue from upfront payments over the period of significant involvement under the related agreements unless the fee is in exchange for products delivered or services rendered that represent the culmination of a separate earnings process and no further performance obligation exists under the contract. The Company recognizes milestone payments as revenue upon the achievement of specified milestones only if (1) the milestone payment is non-refundable, (2) substantive effort is involved in achieving the milestone, (3) the amount of the milestone is reasonable in relation to the effort expended or the risk associated with achievement of the milestone, and (4) the milestone is at risk for both parties. If any of these conditions are not met, the milestone payment is included in the allocation of arrangement consideration, which may result in the deferral of the revenue until the underlying remaining performance obligations are completed.
Research and Development Expenses	Research and Development Expenses Research and development costs are charged to expense as incurred and consist of costs incurred to further the Company’s research and development activities including salaries and related employee benefits, costs associated with clinical trials, costs related to pre-commercialization manufacturing activities such as manufacturing process validation activities and the manufacturing of commercial supply prior to approval, nonclinical research and development activities, regulatory activities, research-related overhead expenses and fees paid to external service providers and contract research and manufacturing organizations that conduct certain research and development activities on behalf of the Company.
Net Loss per Common Share	Net Loss per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per common share is calculated by dividing the net loss by the weighted-average number of common stock equivalents outstanding for the period using the treasury stock method. The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per common share attributable to common stockholders for the periods presented as the effect of including such securities would be antidilutive (in thousands): September 30, 2015 2014 Warrants to purchase common stock 15 56 Options to purchase common stock 4,913 3,858 Restricted stock units 350 130 Common stock subject to repurchase 1 3 5,279 4,047

Description of Business and S16

Description of Business and Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Schedule of Shares Excluded from Computations of Diluted Net Loss per Common Share	The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per common share attributable to common stockholders for the periods presented as the effect of including such securities would be antidilutive (in thousands): September 30, 2015 2014 Warrants to purchase common stock 15 56 Options to purchase common stock 4,913 3,858 Restricted stock units 350 130 Common stock subject to repurchase 1 3 5,279 4,047

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2015
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments Measured at Fair Value on Recurring Basis	The following tables set forth the fair value of the Company’s financial instruments that were measured at fair value on a recurring basis as of September 30, 2015 and December 31, 2014 (in thousands): Level 1 Level 2 Level 3 Total September 30, 2015 Financial assets: Money market funds $ 54,312 $ — $ — $ 54,312 Corporate bonds — 87,208 — 87,208 Agency bonds — 85,776 — 85,776 Commercial paper — 56,843 — 56,843 Total financial assets $ 54,312 $ 229,827 $ — $ 284,139 Liabilities: Contingent put option liability $ — $ — $ 200 $ 200 Total liabilities $ — $ — $ 200 $ 200 Level 1 Level 2 Level 3 Total December 31, 2014 Financial assets: Money market funds $ 10,202 $ — $ — $ 10,202 Corporate bonds — 71,763 — 71,763 Agency bonds — 15,162 — 15,162 Commercial paper — 30,846 — 30,846 Total financial assets $ 10,202 $ 117,771 $ — $ 127,973 Liabilities: Contingent put option liability $ — $ — $ 233 $ 233 Total liabilities $ — $ — $ 233 $ 233
Summary of Changes in Estimated Fair Value of Level 3 Instruments Measured at Fair Value on Recurring Basis	As of September 30, 2015, the Company’s Level 3 liability is comprised of a contingent put option liability. The following table sets forth a summary of the changes in the estimated fair value of the Company’s contingent put option, which are measured at fair value on a recurring basis (in thousands): Balance as of December 31, 2014 $ 233 Change in fair value included in other income (expense) (33 ) Balance as of September 30, 2015 $ 200

Cash, Cash Equivalents, and S18

Cash, Cash Equivalents, and Short-Term Investments (Tables)	9 Months Ended
	Sep. 30, 2015
Cash Cash Equivalents And Short Term Investments [Abstract]
Summary of Cash, Cash Equivalents, and Short-Term Investments	The following is a summary of cash, cash equivalents, and short-term investments (in thousands): Amortized Gross Gross Estimated September 30, 2015 Cash and money market funds $ 57,626 $ — $ — $ 57,626 Corporate bonds 87,235 6 (33 ) 87,208 Agency bonds 85,766 13 (3 ) 85,776 Commercial paper 56,829 14 — 56,843 Total financial assets $ 287,456 $ 33 $ (36 ) $ 287,453 Reported as: Cash and cash equivalents $ 94,721 Short-term Investments 192,732 $ 287,453 Amortized Gross Gross Estimated December 31, 2014 Cash and money market funds $ 17,986 $ — $ — $ 17,986 Corporate bonds 71,794 2 (33 ) 71,763 Agency bonds 15,163 2 (3 ) 15,162 Commercial paper 30,835 11 — 30,846 Total financial assets $ 135,778 $ 15 $ (36 ) $ 135,757 Reported as: Cash and cash equivalents $ 30,264 Short-term investments 105,493 $ 135,757

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2015
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): September 30, December 31, 2015 2014 Accrued contract manufacturing $ 21,359 $ 6,655 Accrued clinical trial expenses 329 41 Accrued accounts payable — 795 Accrued professional and consulting services 525 184 Other 97 103 $ 22,310 $ 7,778

Commitments and Contingencies (

Commitments and Contingencies (Tables)	9 Months Ended
	Sep. 30, 2015
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Payments Under Supply Agreement	The following are the combined future minimum payments under the terms of the Lanxess Supply Agreement, the DPx Supply Agreement, and the Patheon Supply Agreement as of September 30, 2015. These amounts are based on forecasts that include estimates of future market demand, quantity discounts and manufacturing efficiencies (in thousands): 2015 $ 22,471 2016 54,430 2017 70,563 2018 73,893 2019 28,658 Total future minimum payments $ 250,015
Schedule of Future Minimum Payments Under Operating Lease	The Company’s future minimum operating lease payments at September 30, 2015 are as follows (in thousands): 2015 $ 648 2016 3,761 2017 3,941 2018 4,034 2019 4,147 Thereafter 23,482 Total future minimum payments $ 40,013

Equity Compensation Plans and21

Equity Compensation Plans and Stock Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Option Activity Under 2007 Plan 2013 Plan and Inducement Plan and Related Information	The following table summarizes option activity under the 2007 Plan, the 2013 Plan, the Inducement Plan, and related information (in thousands, except per share and contractual term amounts): Shares Shares Subject Weighted- Per Share Weighted- Aggregate (in years) Options outstanding at December 31, 2014 1,167 3,813 $ 11.05 Additional shares reserved under plan 2,402 — — Options granted (1,699 ) 1,699 30.12 Options exercised — (494) 4.88 Options forfeited 105 (105) 27.48 Restricted stock units granted (270 ) — — Restricted stock units canceled 3 — — Balances at September 30, 2015 1,708 4,913 $ 17.91 8.4 $ 28,867 Vested and expected to vest at September 30, 2015 4,686 $ 17.53 8.3 $ 28,513 Vested at September 30, 2015 1,734 $ 8.60 7.3 $ 19,113
Schedule of Stock-Based Compensation Expense	Stock-based compensation expense included in the Company’s consolidated statements of operations is as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Research and development: Employees $ 1,443 $ 440 $ 3,223 $ 934 Nonemployee consultants 609 761 3,001 2,939 General and administrative: Employees 3,045 1,032 6,626 2,410 Nonemployee consultants — — — 13 Total stock-based compensation expense $ 5,097 $ 2,233 $ 12,850 $ 6,296
Schedule of Valuation Assumptions Used to Calculate Fair Value of Employee Stock Options	The estimated grant date fair value of employee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Expected volatility 83% - 85% 92% 82% - 92% 87% - 109% Expected dividends 0% 0% 0% 0% Expected term (in years) 6 6 6 6 Risk-free rate 1.7% –1.9 % 1.8% –2.0 % 1.3% –1.9 % 1.8% –2.0 %
Schedule of Valuation Assumptions Used to Calculate Fair Value of Nonemployee Stock Options	The fair value of nonemployee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions: Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Expected volatility 83% - 91% 104% 83% -92% 104% -122% Expected dividends 0% 0% 0% 0% Expected term (in years) 6 – 8 7 – 9 6 – 9 6 – 9 Risk-free rate 1.5% – 1.8 % 2.0% – 2.4 % 1.5% – 2.1% 2.0% – 2.6%
Summary of Restricted Stock Unit Activity	The following table summarizes restricted stock unit activity for the nine months ended September 30, 2015 (in thousands, except per share amounts): Restricted Stock Units Number of Shares Weighted Average Nonvested at December 31, 2014 123 $ 26.85 Granted 270 28.00 Vested (40 ) 26.82 Canceled (3 ) 27.31 Nonvested at September 30, 2015 350 $ 27.82

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Details) $ in Millions	9 Months Ended
	Sep. 30, 2015USD ($)
Commitments And Contingencies [Line Items]
Lease commencement date	Feb. 1, 2015
Operating lease, term of contract	10 years
Operating lease, renewal term	5 years
Supply agreement term	The Lanxess Supply Agreement terminates on December 31, 2020 unless terminated earlier. The Company may extend the Lanxess Supply Agreement for an additional five years with notice.
Agreement termination date	Dec. 31, 2020
Extended agreement period	5 years
Additional lease allowance	$ 2.2
One-time lease improvement allowance	0.6
Amount used in additional lease allowance	0.8
Irrevocable Letter of Credit
Commitments And Contingencies [Line Items]
Security deposit	$ 0.7
Patheon Inc
Commitments And Contingencies [Line Items]
Supply agreement term	The Patheon Supply Agreement may be terminated by the Company with written notice under certain provisions.

Description of Business and S23

Description of Business and Significant Accounting Policies - Additional Information (Details)	Mar. 03, 2015USD ($)$ / sharesshares	Feb. 28, 2015USD ($)$ / sharesshares	Sep. 30, 2015USD ($)Segment	Sep. 30, 2014USD ($)	Dec. 31, 2014USD ($)$ / sharesshares	Dec. 04, 2014USD ($)
Description Of Business And Significant Accounting Policies [Line Items]
Commencement date of operations			Oct. 29, 2007
Number of business segments | Segment			1
Gross proceeds from issuance of common stock	$ 172,700,000
Aggregate net proceeds from issuance of common stock	$ 161,900,000		$ 213,711,000	$ 94,607,000
Accumulated deficit			$ 426,118,000		$ 305,728,000
Common Stock
Description Of Business And Significant Accounting Policies [Line Items]
Issuance of common stock, shares | shares	4,485,000
Shares issued, price per share | $ / shares	$ 38.50
Shelf Registration | Maximum
Description Of Business And Significant Accounting Policies [Line Items]
Aggregate offering price						$ 250,000,000
Shelf Registration | Common Stock | Maximum
Description Of Business And Significant Accounting Policies [Line Items]
Aggregate offering price						$ 70,000,000
At The Market Offering Program
Description Of Business And Significant Accounting Policies [Line Items]
Issuance of common stock, shares | shares		1,549,910			514,710
Shares issued, price per share | $ / shares		$ 34.48			$ 32.17
Gross proceeds from issuance of common stock		$ 53,400,000			$ 16,600,000
Aggregate net proceeds from issuance of common stock		$ 51,800,000			$ 16,100,000
Relypsa UK LTD
Description Of Business And Significant Accounting Policies [Line Items]
Date of entity incorporation			Oct. 28, 2014

Description of Business and S24

Description of Business and Significant Accounting Policies - Schedule of Shares Excluded from Computations of Diluted Net Loss per Common Share (Details) - shares shares in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computations of diluted net loss per common share	5,279	4,047
Warrants To Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computations of diluted net loss per common share	15	56
Options to Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computations of diluted net loss per common share	4,913	3,858
Restricted Stock Units
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computations of diluted net loss per common share	350	130
Common Stock Subject to Repurchase
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computations of diluted net loss per common share	1	3

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Financial assets:
Total financial assets	$ 284,139	$ 127,973
Liabilities:
Total liabilities	200	233
Contingent Put Option Liability
Liabilities:
Total liabilities	200	233
Corporate Bonds
Financial assets:
Total financial assets	87,208	71,763
Agency Bonds
Financial assets:
Total financial assets	85,776	15,162
Level 1
Financial assets:
Total financial assets	54,312	10,202
Level 2
Financial assets:
Total financial assets	229,827	117,771
Level 2 | Corporate Bonds
Financial assets:
Total financial assets	87,208	71,763
Level 2 | Agency Bonds
Financial assets:
Total financial assets	85,776	15,162
Level 3
Liabilities:
Total liabilities	200	233
Level 3 | Contingent Put Option Liability
Liabilities:
Total liabilities	200	233
Money Market Funds
Financial assets:
Total financial assets	54,312	10,202
Money Market Funds | Level 1
Financial assets:
Total financial assets	54,312	10,202
Commercial Paper
Financial assets:
Total financial assets	56,843	30,846
Commercial Paper | Level 2
Financial assets:
Total financial assets	$ 56,843	$ 30,846

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Changes in Estimated Fair Value of Level 3 Instruments Measured at Fair Value on Recurring Basis (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2015USD ($)
Fair Value Disclosures [Abstract]
Beginning Balance	$ 233
Change in fair value included in other income (expense)	(33)
Ending Balance	$ 200

Cash, Cash Equivalents, and S27

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents, and Short-Term Investments (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013
Cash And Cash Equivalents [Line Items]
Amortized Cost	$ 287,456	$ 135,778
Gross Unrealized Gains	33	15
Gross Unrealized Losses	(36)	(36)
Estimated Fair Value	287,453	135,757
Cash and cash equivalents	94,721	30,264	$ 39,410	$ 94,759
Short-term investments	192,732	105,493
Total financial assets	287,453	135,757
Cash and Money Market Funds
Cash And Cash Equivalents [Line Items]
Amortized Cost	57,626	17,986
Estimated Fair Value	57,626	17,986
Commercial Paper
Cash And Cash Equivalents [Line Items]
Amortized Cost	56,829	30,835
Gross Unrealized Gains	14	11
Estimated Fair Value	56,843	30,846
Corporate Bonds
Cash And Cash Equivalents [Line Items]
Amortized Cost	87,235	71,794
Gross Unrealized Gains	6	2
Gross Unrealized Losses	(33)	(33)
Estimated Fair Value	87,208	71,763
Agency Bonds
Cash And Cash Equivalents [Line Items]
Amortized Cost	85,766	15,163
Gross Unrealized Gains	13	2
Gross Unrealized Losses	(3)	(3)
Estimated Fair Value	$ 85,776	$ 15,162

Cash, Cash Equivalents, and S28

Cash, Cash Equivalents, and Short-Term Investments - Additional Information (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Cash Cash Equivalents And Short Term Investments [Abstract]
Realized gain or losses on available-for-sale securities	$ 0	$ 0
Available for sale securities, continuous unrealized loss position for more than one year	$ 0

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accrued contract manufacturing	$ 21,359	$ 6,655
Accrued clinical trial expenses	329	41
Accrued accounts payable		795
Accrued professional and consulting services	525	184
Other	97	103
Total accrued liabilities	$ 22,310	$ 7,778

Borrowings - Additional Informa

Borrowings - Additional Information (Details) $ / shares in Units, $ in Thousands	May. 30, 2014USD ($)$ / sharesshares	Sep. 30, 2015USD ($)Payment	Mar. 31, 2015shares	Dec. 31, 2014shares	Sep. 30, 2014USD ($)	Sep. 30, 2015USD ($)Payment	Sep. 30, 2014USD ($)	Dec. 31, 2014shares	Jan. 31, 2013$ / sharesshares
Debt Instrument [Line Items]
Proceeds from issuance of long term debt							$ 3,549
Capital Loan
Debt Instrument [Line Items]
Proceeds from issuance of long term debt	$ 15,000					$ 15,000
Repayment of outstanding debt						11,000
Final payment fee		$ 400				400
Advance not yet received		$ 20,000				$ 20,000
Debt instrument, payment terms						Payments on the new $15.0 million loan will be interest only through January 2016, followed by 30 months of equal monthly payments of interest and principal
Number of debt repayments | Payment		30				30
Final payment as a percentage of amounts borrowed						8.50%
Exercise price of warrants | $ / shares	$ 23.69
Warrants exercised | shares			40,828	13,609
Fair value of warrants		$ 200				$ 200
Warrants, fair value assumptions, interest rate						2.06%
Warrants, fair value assumptions, expected life						7 years
Warrants, fair value assumptions, volatility factor						91.67%
Warrants, fair value assumptions, dividend yield						0.00%
Interest expense		500			$ 500	$ 1,400	$ 1,200
Estimated fair value of contingent put option liability		200				200
Principal amount outstanding on loan		$ 15,000				$ 15,000
Capital Loan | Minimum
Debt Instrument [Line Items]
Prepayment charges of outstanding loan						1.00%
Capital Loan | Maximum
Debt Instrument [Line Items]
Prepayment charges of outstanding loan						3.00%
Capital Loan | Common Stock
Debt Instrument [Line Items]
Warrant issued to purchase common stock | shares	12,661		29,690					7,808
Capital Loan | Series C-1 Convertible Preferred Stock
Debt Instrument [Line Items]
Warrants issued to purchase preferred stock | shares									54,437
Exercise price of warrants | $ / shares									$ 9.1848
Capital Loan | Initial advance
Debt Instrument [Line Items]
Debt instrument, interest rate		7.40%				7.40%
Capital Loan | Three Month LIBOR Rate | Second Tranche
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate						7.17%

Collaboration and License Agr31

Collaboration and License Agreement - Additional Information (Details) - USD ($)	Aug. 31, 2015	Sep. 30, 2015	Sep. 30, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized		$ 6,600,000	$ 6,600,000
Milestone triggered under License Agreement			$ 0
VFMCRP [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
License upfront fee	$ 40,000,000
Milestone payments receivable	$ 125,000,000

Commitments and Contingencies32

Commitments and Contingencies - Schedule of Future Minimum Payments Under Supply Agreement(Details) - DPx Fine Chemicals, Lanxess and Patheon $ in Thousands	Sep. 30, 2015USD ($)
Long Term Purchase Commitment [Line Items]
2,015	$ 22,471
2,016	54,430
2,017	70,563
2,018	73,893
2,019	28,658
Total future minimum payments	$ 250,015

Commitments and Contingencies33

Commitments and Contingencies - Schedule of Future Minimum Payments Under Operating Lease (Details) $ in Thousands	Sep. 30, 2015USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,015	$ 648
2,016	3,761
2,017	3,941
2,018	4,034
2,019	4,147
Thereafter	23,482
Total future minimum payments	$ 40,013

Equity Compensation Plans and34

Equity Compensation Plans and Stock Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jul. 31, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant-date fair value of options grant		$ 20.07	$ 20.50	$ 21.95	$ 20.98
Unrecognized compensation cost		$ 52.2		$ 52.2
Expected period of compensation expense recognized				3 years 2 months 9 days
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation cost		$ 9.3		$ 9.3
Expected period of compensation expense recognized				3 years 6 months
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		587,438		587,438
2007 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted period				10 years
Option vest over period				4 years
2013 Equity Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Option granted period				10 years
Share-based compensation description				Options granted under the 2013 Plan may be granted for periods of up to ten years and are generally exercisable when vested. Any remaining shares available for future issuance under the 2007 Stock Plan are available for issuance under the 2013 Plan. The 2013 plan reserve will automatically increase annually from January 1, 2014 through January 1, 2023 by an amount equal to the smaller of: (a) 2,553,174 shares, (b) four percent of the number of shares of common stock issued and outstanding on the immediately preceding December 31, or (c) an amount determined by the Company's board of directors.
Increase of shares reserve under the plan				2,553,174
Percentage of common stock issued and outstanding				4.00%
Beginning date for increase in share reserve				Jan. 1, 2014
Ending date for increase in share reserve				Jan. 1, 2023
Share-based compensation authorized		1,007,241		1,007,241
2014 Employment Commencement Incentive Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share-based compensation authorized						1,000,000
Common stock reserved for issuance	1,000,000
Share issued or transferred under the Plan				1,298,650

Equity Compensation Plans and35

Equity Compensation Plans and Stock Based Compensation - Summary of Option Activity Under 2007 Plan 2013 Plan and Inducement Plan and Related Information (Details) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended
	Sep. 30, 2015USD ($)$ / sharesshares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Restricted stock units granted	(270)
Shares Available for Grant, Restricted stock units cancelled	3
2007 Plan, 2013 Plan and Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Options outstanding, beginning balance	1,167
Shares Available for Grant, Additional shares reserved	2,402
Shares Available for Grant, Options granted	(1,699)
Shares Available for Grant, Options forfeited	105
Shares Available for Grant, Restricted stock units granted	(270)
Shares Available for Grant, Restricted stock units cancelled	3
Shares Available for Grant, Options outstanding, ending balance	1,708
Shares Subject to Outstanding Options, Options outstanding, beginning balance	3,813
Shares Subject to Outstanding Options, Options granted	1,699
Shares Subject to Outstanding Options, Options exercised	(494)
Shares subject to Outstanding Options, Options forfeited	(105)
Shares Subject to Outstanding Options, Options outstanding, ending balance	4,913
Shares Subject to Outstanding Options, Vested and expected to vest	4,686
Shares Subject to Outstanding Options, Vested	1,734
Weighted-Average Exercise Price Per Share, Options outstanding, beginning balance | $ / shares	$ 11.05
Weighted-Average Exercise Price Per Share, Options granted | $ / shares	30.12
Weighted-Average Exercise Price Per Share, Options exercised | $ / shares	4.88
Weighted-Average Exercise Price Per Share, Options forfeited | $ / shares	27.48
Weighted-Average Exercise Price Per Share, Options outstanding, ending balance | $ / shares	17.91
Weighted-Average Exercise Price Per Share, Vested and expected to vest | $ / shares	17.53
Weighted-Average Exercise Price Per Share, Vested | $ / shares	$ 8.60
Weighted-Average Remaining Contractual Term, Options outstanding	8 years 4 months 24 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	8 years 3 months 18 days
Weighted-Average Remaining Contractual Term, Vested	7 years 3 months 18 days
Aggregate Intrinsic Value, Options Outstanding | $	$ 28,867
Aggregate Intrinsic Value, Vested and expected to vest | $	28,513
Aggregate intrinsic value, Vested | $	$ 19,113

Equity Compensation Plans and36

Equity Compensation Plans and Stock Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 5,097	$ 2,233	$ 12,850	$ 6,296
Research and Development | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	1,443	440	3,223	934
Research and Development | Non-employee Consultants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	609	761	3,001	2,939
General and Administrative | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 3,045	$ 1,032	$ 6,626	2,410
General and Administrative | Non-employee Consultants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation				$ 13

Equity Compensation Plans and37

Equity Compensation Plans and Stock Based Compensation - Schedule of Valuation Assumptions Used to Calculate Fair Value of Employee Stock Options (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Compensation Related Costs [Abstract]
Expected volatility, maximum	85.00%		92.00%	109.00%
Expected volatility, minimum	83.00%		82.00%	87.00%
Expected volatility		92.00%
Expected dividends	0.00%	0.00%	0.00%	0.00%
Expected term (in years)	6 years	6 years	6 years	6 years
Risk-free rate, maximum	1.90%	2.00%	1.90%	2.00%
Risk-free rate, minimum	1.70%	1.80%	1.30%	1.80%

Equity Compensation Plans and38

Equity Compensation Plans and Stock Based Compensation - Schedule of Valuation Assumptions Used to Calculate Fair Value of Nonemployee Stock Options (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility		104.00%
Expected dividends	0.00%	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	83.00%		83.00%	104.00%
Expected term (in years)	6 years	7 years	6 years	6 years
Risk-free rate	1.50%	2.00%	1.50%	2.00%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	91.00%		92.00%	122.00%
Expected term (in years)	8 years	9 years	9 years	9 years
Risk-free rate	1.80%	2.40%	2.10%	2.60%

Equity Compensation Plans and39

Equity Compensation Plans and Stock Based Compensation - Summary of Restricted Stock Unit Activity (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2015$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Nonvested at Beginning	123
Number of Shares, Granted	270
Number of Shares, Vested	(40)
Number of Shares, Canceled	(3)
Number of Shares, Nonvested at Ending	350
Weighted Average Grant Date Fair Value Per Share, Nonvested at Beginning | $ / shares	$ 26.85
Weighted Average Grant Date Fair Value Per Share, Granted | $ / shares	28
Weighted Average Grant Date Fair Value Per Share, Vested | $ / shares	26.82
Weighted Average Grant Date Fair Value Per Share, Canceled | $ / shares	27.31
Weighted Average Grant Date Fair Value Per Share, Nonvested at Ending | $ / shares	$ 27.82