Relypsa (RLYP) 10-K 25 Feb 16 2015 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2015	Feb. 15, 2016	Jun. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	FY
Trading Symbol	RLYP
Entity Registrant Name	Relypsa Inc
Entity Central Index Key	1,416,792
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		43,311,249
Entity Public Float			$ 1,130,137,164

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 63,723	$ 30,264
Short-term investments	176,993	105,493
Restricted cash		268
Trade receivables	530
Other receivables	779	425
Inventory	8,851
Prepaid expenses and other current assets	5,405	2,756
Total current assets	256,281	139,206
Restricted cash	1,436	686
Property and equipment, net	9,627	3,467
Other assets	10,984	8,480
Total assets	278,328	151,839
Current liabilities:
Accounts payable	3,037	3,156
Accrued payroll and related expenses	11,835	4,393
Accrued liabilities	37,737	7,778
Deferred rent, current portion	27	1,156
Line of credit, current portion	301	432
Deferred revenue, current portion	16,242
Total current liabilities	69,179	16,915
Long-term liabilities:
Deferred rent	3,039	983
Line of credit		267
Capital loan	15,592	15,213
Deferred revenue	5,645
Total liabilities	$ 93,455	$ 33,378
Commitments and contingencies
Stockholders’ equity:
Preferred stock: $0.001 par value; 5,000 shares authorized at December 31, 2015 and 2014; no shares issued and outstanding at December 31, 2015 and 2014
Common stock: $0.001 par value; 300,000 shares authorized at December 31, 2015 and 2014; 41,974 and 35,045 shares issued and outstanding at December 31, 2015 and 2014, respectively	$ 42	$ 35
Additional paid-in capital	669,331	424,175
Accumulated other comprehensive loss	(56)	(21)
Accumulated deficit	(484,444)	(305,728)
Total stockholders’ equity	184,873	118,461
Total liabilities and stockholders’ equity	$ 278,328	$ 151,839

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 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	41,974,000	35,045,000
Common stock, shares outstanding	41,974,000	35,045,000

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Collaboration and license revenue	$ 18,550
Operating expenses:
Research and development	93,298	$ 50,227	$ 58,971
Selling, general and administrative	103,138	27,914	11,940
Total operating expenses	196,436	78,141	70,911
Loss from operations	(177,886)	(78,141)	(70,911)
Interest and other income (expense), net	915	149	(1,481)
Interest expense	(1,745)	(1,896)	(1,453)
Net loss	(178,716)	(79,888)	(73,845)
Deemed dividend to preferred stockholders			(7,336)
Net loss attributable to common stockholders	$ (178,716)	$ (79,888)	$ (81,181)
Net loss per share attributable to common stockholders, basic and diluted	$ (4.39)	$ (2.43)	$ (22.42)
Weighted-average common shares used to compute net loss per share attributable to common stockholders, basic and diluted	40,697,896	32,837,508	3,620,235

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (178,716)	$ (79,888)	$ (73,845)
Other comprehensive loss:
Unrealized loss on available-for-sale securities, net of tax	(35)	(21)	(23)
Total comprehensive loss	$ (178,751)	$ (79,909)	$ (73,868)

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders Equity (Deficit) - USD ($) shares in Thousands, $ in Thousands	Total	Series C-2	Common Stock	Additional Paid-In Capital	Additional Paid-In CapitalSeries C-2	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit	Accumulated DeficitSeries C-2	Shelf Registration Statement	Shelf Registration StatementCommon Stock	Shelf Registration StatementAdditional Paid-In Capital	Convertible Preferred Stock	Convertible Preferred StockSeries C-2
Beginning balance at Dec. 31, 2012	$ (147,361)					$ 23	$ (147,384)					$ 177,418
Issuance of preferred stock for cash													$ 14,983
Warrants deemed dividend		$ (7,336)			$ (2,725)			$ (4,611)
Exercise of warrants	397		$ 3	$ 394
Conversion of preferred stock to common stock	192,401		19	192,382								$ (192,401)
Reclassification of warrant liability	28,647			28,647
Exercise of stock options	97			97
Stock-based compensation	3,909			3,909
Issuance of common stock, net of issuance cost	77,964		8	77,956
Unrealized loss on investments	(23)					(23)
Net loss	(73,845)						(73,845)
Ending balance at Dec. 31, 2013	74,850		$ 30	300,660			(225,840)
Beginning balance, shares at Dec. 31, 2012			310									16,059
Issuance of preferred stock for cash, shares													1,633
Exercise of warrants, shares			2,573
Conversion of preferred stock to common stock, shares			18,925									(17,692)
Issuance of common stock, shares			7,878
Exercise of stock options, shares			24
Ending balance, shares at Dec. 31, 2013			29,710
Exercise of stock options	2,923			2,923
Stock-based compensation	9,695			9,695
Issuance of common stock, net of issuance cost	94,607		$ 4	94,603					$ 16,061	$ 1	$ 16,060
Unrealized loss on investments	(21)					(21)
Net loss	(79,888)						(79,888)
Ending balance at Dec. 31, 2014	118,461		$ 35	424,175		(21)	(305,728)
Issuance of warrants	234			234
Exercise of warrants, shares			12
Issuance of common stock, shares			4,131							515
Exercise of stock options, shares			677
Ending balance, shares at Dec. 31, 2014			35,045
Exercise of stock options	3,952		$ 1	3,951
Issuance of common stock under Employee Stock Purchase Plan	862			862
Stock-based compensation	19,288			19,288
Recovery of related party short-swing profits	7,350			7,350
Issuance of common stock, net of issuance cost	161,871		4	161,867					$ 51,840	$ 2	$ 51,838
Unrealized loss on investments	(35)					(35)
Net loss	(178,716)						(178,716)
Ending balance at Dec. 31, 2015	$ 184,873		$ 42	$ 669,331		$ (56)	$ (484,444)
Exercise of warrants, shares			30
Issuance of common stock, shares			4,485							1,550
Exercise of stock options, shares			781
Ending balance, shares at Dec. 31, 2015			41,974
Vesting of restricted stock units, shares			41
Issuance of common stock under Employee Stock Purchase Plan, shares	862		42

Consolidated Statements of Con7

Consolidated Statements of Convertible Preferred Stock and Stockholders Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Common Stock
Issuance Costs	$ 10,800	$ 6,600	$ 8,691
Issuance of common stock, shares	4,485,000	4,131,000	7,878,000
Convertible Preferred Stock | Series C-2
Issuance Costs			$ 17

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating activities
Net loss	$ (178,716)	$ (79,888)	$ (73,845)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,772	4,766	1,088
Stock-based compensation	19,288	9,695	3,909
Amortization of debt discount	145	174	136
Amortization of debt issuance costs	38	24	32
Accretion of final debt payment	566	498	350
Accrued interest on capital loan		71
Investment premium amortization	1,314	726
Loss on disposal of fixed assets	13
Revaluation of convertible preferred stock warrant liability			1,564
Changes in assets and liabilities:
Receivables	(884)	(184)	2,742
Inventory	(8,851)
Prepaid expenses and other current assets	(2,660)	(1,123)	(669)
Other assets and restricted cash	(2,986)	(5,698)	(3,431)
Accounts payable	(119)	(1,580)	1,264
Accrued and other liabilities	37,261	4,552	3,465
Deferred rent	927	(2,895)	755
Deferred revenue	21,887
Net cash used in operating activities	(110,005)	(70,862)	(62,640)
Investing activities
Purchase of investments	(379,148)	(163,205)	(10,087)
Proceeds from maturities of short-term investments	301,281	56,965	49,198
Proceeds from sales of short-term investments	5,018
Purchase of property and equipment	(8,945)	(2,595)	(3,776)
Net cash (used in) provided by investing activities	(81,794)	(108,835)	35,335
Financing activities
Net proceeds from issuance of convertible preferred stock			14,983
Net proceeds from public offerings	213,711	110,668	77,964
Proceeds from common stock option exercises	3,952	2,923	97
Proceeds from purchases under the Employee Stock Purchase Plan	862
Proceeds from warrant exercises			397
Net proceeds from capital loan		3,549	12,404
Repayment of capital loan		(1,530)
Net proceeds from equipment line of credit			1,225
Loan fee payment	(185)
Repayment of equipment line of credit	(432)	(408)	(227)
Recovery of related party short-swing profits	7,350
Net cash provided by financing activities	225,258	115,202	106,843
Net increase (decrease) in cash and cash equivalents	33,459	(64,495)	79,538
Cash and cash equivalents at beginning of period	30,264	94,759	15,221
Cash and cash equivalents at end of period	63,723	30,264	94,759
Supplemental disclosures of cash flow information
Cash paid for interest	1,135	996	854
Cash paid for taxes	$ 1	1	2
Noncash investing and financing activities
Contingent put option liability		110
Reclassification of convertible preferred stock warrant liability due to the exercise of the warrants			28,072
Reclassification of convertible preferred stock warrant liability due to conversion to warrants to purchase common stock			575
Line of Credit
Noncash investing and financing activities
Issuance of warrants			25
Capital Loan
Noncash investing and financing activities
Issuance of warrants		$ 234	193
Series C Financings
Noncash investing and financing activities
Issuance of warrants			$ 7,336

Organization

Organization	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization Relypsa, Inc. (Relypsa or the Company) is a biopharmaceutical company dedicated to the development and commercialization of polymer-based drugs to treat conditions that are often overlooked and undertreated, but that can have a serious impact on patients’ lives and even be life-threatening. On October 21, 2015, the U.S. Food and Drug Administration (FDA) approved the Company’s first drug, Veltassa ® Veltassa in December 2015 and it is available for prescription to patients in the United States through a limited number of specialty pharmacies and specialty distributors.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The accompanying consolidated financial statements include the accounts of Relypsa and its wholly-owned subsidiary, Relypsa UK LTD, and have been prepared in accordance with U.S. generally accepted accounting principles (“US GAAP”). Intercompany transactions and balances have been eliminated in consolidation. Use of Estimates The preparation of consolidated financial statements in conformity with US 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, inventories, clinical trial accruals, manufacturing accruals, fair value of assets and liabilities, 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. Liquidity The Company has never been profitable and, as of December 31, 2015, the Company has an accumulated deficit of $484.4 million. The Company has incurred net losses of approximately $178.7 million, $79.9 million and $73.8 million in the years ended December 31, 2015, 2014, and 2013, respectively. The Company may continue to incur substantial operating losses even after it begins to generate meaningful revenues from Veltassa. If the Company is unable to achieve the level of revenues from product sales during 2016 that is contemplated in its operating plan and the Company is unable to raise additional funds through public or private equity, debt financings or other sources, the Company has contingency plans to implement cost cutting actions to reduce its working capital requirements beginning as early as the third quarter of 2016. As part of such plans, the Company will prioritize necessary and appropriate steps to enable the continued operations of the business and preservation of the value of its assets beyond the next twelve months, including, but not limited to, reducing commercial, marketing, medical affairs, clinical trials, research, manufacturing, and personnel-related costs, and reducing capital equipment investments and other discretionary expenditures that are within its control. These reductions in expenditures, if required, may have an adverse impact on the Company’s ability to achieve certain of its planned objectives during 2016, which could have a material adverse effect on the business, results of operations, and financial condition. The Company will need to generate significant revenues to achieve profitability and may never do so. Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of 90 days or less at the date of purchase to be cash equivalents. Investments Investments consist of debt securities which are classified as available-for-sale. Short-term investments have remaining maturities less than one year as of the balance sheet date. Long-term investments have remaining maturities greater than one year as of the balance sheet date. Investments are carried at fair value based upon quoted market prices or pricing models for similar securities. Unrealized gains and losses on available-for-sale securities are reported as a component of accumulated comprehensive income (loss). Realized gains or losses on the sale of securities are reported in interest and other income (expense), net and computed using the specific identification method. Inventory Inventory is composed of raw materials, intermediate materials, which are classified as work-in-process and finished goods, which are goods that are available for sale. Inventory costs include amounts related to third-party contract manufacturing, shipping costs, amortization of up-front payments to contract manufacturers, or CMOs, packaging services and manufacturing overhead. Inventory is carried at standard cost, which approximates weighted average cost. The Company has contracted with third party manufacturers that produce the raw and intermediate materials used in the production of Veltassa as well as the finished product. In connection with production of inventory, the Company may be required to provide payments to third party manufacturers in advance of transfer of title or risk of loss. These amounts are included in inventory as raw materials on the accompanying consolidated balance sheets. Inventories are stated at the lower of cost or market. If the Company identifies excess, obsolete or unsalable product, the Company will write down its inventory to its net realizable value in the period it is identified. The Company received FDA approval for Veltassa on October 21, 2015 and began capitalizing inventory starting in October 2015. Cost incurred prior to approval have been recorded as research and development expense in the consolidated statements of operations. Accounts Receivable The Company extends credit to customers for product sales resulting in accounts receivable. Customer accounts will be monitored for past due amounts. Past due accounts receivable, determined to be uncollectible, will be written off against the allowance for doubtful accounts. Allowances for doubtful accounts will be estimated based upon past due amounts, historical losses and existing economic factors, and are adjusted periodically. The accounts receivable are reported in the consolidated balance sheets, net of allowances for doubtful accounts. As of December 31, 2015, the Company had a trade accounts receivable balance of $0.5 million related to Veltassa product sales and there were no allowance for doubtful accounts at December 31, 2015. Revenue Recognition Revenue is recognized when (1) persuasive evidence of an arrangement exists, (2) delivery has occurred or services have been rendered, (3) the price is fixed and determinable and (4) collectability is reasonably assured. Revenues are deferred for fees received before earned or until no further obligations exist. The Company exercises judgment in determining that collectability is reasonably assured or that services have been delivered in accordance with the arrangement. The Company assess whether the fee is fixed or determinable based on the payment terms associated with the transaction and whether the sales price is subject to refund or adjustment. The Company assess collectability based primarily on the customer’s payment history and on the creditworthiness of the customer. Product Revenue The Company’s product revenues consist of U.S. sales of Veltassa and are recognized once the Company meets all four revenue recognition criteria described above. Veltassa was approved by the FDA on October 21, 2015 and the Company commenced shipments of Veltassa to specialty pharmacies and specialty distributors in late December 2015. The Company presently does not have the ability to estimate the extent of rebates or chargebacks or product that may ultimately be returned due to our lack of history with Veltassa product revenues at this time. Accordingly, the price is not considered to be deemed fixed and determinable at the time of the shipment to the specialty pharmacy or specialty distributor. Therefore, the Company recognizes revenue once the specialty pharmacy has filled the patient’s prescription for Veltassa or specialty distributor sells Veltassa. This approach is frequently referred to as the “sell-through” revenue recognition model. Under the sell-through approach, revenue is recognized when the specialty pharmacy provides product to a patient based on the fulfillment of a prescription or specialty distributor sells product to a hospital or other eligible entity. As of December 31, 2015, the Company had a deferred revenue balance of $0.5 million related to Veltassa product sales. Collaboration and License Revenue In August 2015, the Company entered into a collaboration and license agreement (License Agreement) with Vifor Fresenius Medical Care Renal Pharma (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. The upfront payment of $40.0 million was allocated to the 1) License and work on the submission of MAA deliverable, 2) the R&D deliverable and 3) the committee participation deliverable using the relative estimated selling price method. The Company estimated the best estimate of selling price (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 determination of the BESP of the license involved significant judgment regarding the patient populations in the Licensed Territory, the percent of patients that would be treated and receive payment coverage, the duration of treatment of patients, the time and probability to achieve regulatory and pricing approval, and an appropriate discount rate. Concentrations of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of investments. The Company invests in money market accounts, U.S. Treasury notes, municipal bonds, agency bonds, corporate notes, certificates of deposit and commercial paper. Other than for obligations of the U.S. government, the Company’s policy is that no more than 5% of its investments may be concentrated in a single issuer. Bank deposits are held by a single financial institution having a strong credit rating and these deposits may at times be in excess of insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and short-term investments and issuers of investments to the extent recorded on the balance sheets. The Company’s investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer. Restricted Cash Restricted cash related to the Company’s leases consist of irrevocable letters of credit that are collateralized by restricted deposits held at the Company’s bank over a term that is consistent with the corresponding lease. Restricted cash also consists of a letter of credit related to the Company’s corporate credit card program that is collateralized by a restricted deposit at the Company’s bank. Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the related assets, ranging from three to seven years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful lives of the respective assets. Impairment of Long-Lived Assets The Company identifies and records impairment losses on long-lived assets used in operations when events and changes in circumstances indicate that the carrying amount of an asset might not be recoverable. Recoverability is measured by comparing the anticipated undiscounted future net cash flows to the related asset’s carrying value. If an asset is considered impaired, the asset is written down to fair value, which is determined based either on discounted cash flows or appraised value, depending on the nature of the asset. The Company has not recorded any impairment losses during the periods presented. 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. Clinical Trial Accruals Clinical trial costs are a component of research and development expenses. The Company accrues and expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company determines the actual costs through discussions with internal personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services. Contract Manufacturing Accruals Contract manufacturing costs related to pre-commercial activities are a component of research and development expense. The Company accrues and expenses contract manufacturing related to pre-commercial activities performed by third parties based upon actual work or the estimated amount of work completed in accordance with agreements established with contract manufacturing organizations. The Company determines the actual costs or estimates of the costs through discussions with internal personnel and external service providers as to the pre-commercial manufacturing activities that were performed or completed and the agreed-upon fee to be paid for such services. Additionally, there may be accruals related to commercial activities that are recorded as a component of inventory. Income Taxes The Company uses the liability method to account for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial statement carrying amounts of existing assets and liabilities and their tax bases. Deferred tax assets and liabilities are measured using enacted tax rates applied to taxable income in the years in which those temporary differences are expected to be recovered or settled. A valuation allowance is established when necessary to reduce deferred tax assets to the amount expected to be realized. Financial statement effects of uncertain tax positions are recognized when it is more–likely-than-not, based on the technical merits of the position, that they will be sustained upon examination. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax. Stock-Based Compensation The Company accounts for stock-based compensation based on the fair value of the share-based awards that are ultimately expected to vest. The fair value of employee stock options granted is estimated on the date of grant using the Black-Scholes option pricing model, and is recognized in expense over the requisite service period using the straight-line method, if performance or service conditions are expected to be achieved. Forfeiture estimates are adjusted to the extent that actual forfeitures differ from the prior estimates. The fair value of restricted stock unit awards used in the Company’s expense recognition method is based on the number of restricted stock units granted and the closing price of the Company’s common stock on the date of the grant. Such value is recognized as an expense over the requisite service period using the straight-line method, net of estimated forfeitures. The Company adopted an employee stock purchase plan (ESPP) on November 2013 and in August 2014, the ESPP was initiated, pursuant to which eligible employees can purchase shares of the Company’s common stock at a price per share equal to the lesser of 85% of the fair market value on the first day of the offering period or 85% of the fair market value on the purchase date. The Company records the expense attributable to nonemployee services paid with share-based awards based on the estimated fair value of the awards determined using the Black-Scholes option pricing model. The measurement of stock-based compensation for nonemployees is subject to periodic adjustments as the options vest, and the expense is recognized over the period during which services are received. Convertible Preferred Stock Prior to the Company’s IPO, the Company recorded all shares of convertible preferred stock at their respective fair values, net of issuance costs, on the dates of issuance. Upon completing the IPO, all shares of the Company’s convertible preferred stock then outstanding converted into 18,924,883 shares of our common stock. Convertible Preferred Stock Warrant Liability Prior to the Company’s IPO, freestanding warrants for shares that were either puttable or redeemable were classified as liabilities on the balance sheets and were carried at their estimated fair value. The preferred stock underlying the warrants was redeemable in certain circumstances. At the end of each reporting period, changes in the estimated fair value during the period were recorded in interest and other income (expense), net. The consummation of the Company’s IPO resulted in the conversion of all classes of the Company’s preferred stock into common stock. Upon such conversion of the underlying classes of preferred stock, the warrants were reclassified as a component of equity and were no longer subject to re-measurement. Deferred Rent Rent expense is recognized on a straight-line basis over the noncancelable term of the Company’s operating lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. In accordance with the terms of the lease for the Company’s office and laboratory space as of December 31, 2015, the Company also recorded lessor-funded lease incentives, such as reimbursable leasehold improvements, as a deferred rent liability, which is amortized as a reduction of rent expense over the noncancelable term of its operating lease. Net Loss per Common Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share of common stock is the same as basic net loss per share of common stock, since the effects of potentially dilutive securities are antidilutive. The net loss per share of common stock attributable to common stockholders is computed using the two-class method required for participating securities. All series of the Company’s convertible preferred stock are considered to be participating securities as they are entitled to participate in undistributed earnings with shares of common stock. Due to the Company’s net loss, there is no impact on earnings per share calculation in applying the two-class method since the participating securities have no legal requirement to share in any losses. 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): Year Ended December 31, 2015 2014 2013 Warrants to purchase common stock 15 56 64 Options to purchase common stock 4,951 3,813 3,545 Restricted stock units 1,042 123 — Common stock subject to repurchase — 1 5 6,008 3,993 3,614 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 In November 2015, FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Fair Value Measurements	3. 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. The accounting guidance for fair value establishes a three-level 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 consolidated financial instruments that were measured at fair value on a recurring basis as of December 31, 2015 and 2014 (in thousands): Level 1 Level 2 Level 3 Total December 31, 2015 Financial assets: Money market funds $ 37,205 $ — $ — $ 37,205 Corporate bonds — 46,650 — 46,650 Agency bonds — 124,434 — 124,434 Commercial paper — 23,288 — 23,288 U.S. government bonds — 7,667 — 7,667 Total financial assets $ 37,205 $ 202,039 $ — $ 239,244 Liabilities: Contingent put option liability $ — $ — $ 93 $ 93 Total financial liabilities $ — $ — $ 93 $ 93 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 financial liabilities $ — $ — $ 233 $ 233 As of December 31, 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 level 3 instruments, which are measured at fair value on a recurring basis (in thousands): Balance as of December 31, 2013 $ — Issuance of contingent put option liability 110 Increase in fair value included in other income (expense) 123 Balance as of December 31, 2014 233 Decrease in fair value included in other income (expense) (140 ) Balance as of December 31, 2015 $ 93 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 8 “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. Changes to the estimated fair value of the contingent put option will be recorded in interest and other income (expense), net in the consolidated statements of operations. The carrying values of the Company’s financial instruments, such as cash equivalents, 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	12 Months Ended
	Dec. 31, 2015
Cash Cash Equivalents And Short Term Investments [Abstract]
Cash, Cash Equivalents, and Short-Term Investments	4. Cash, Cash Equivalents, and Short-Term Investments The following is a summary of cash, cash equivalents, and short-term investments (in thousands). Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value December 31, 2015 Cash and money market funds $ 38,677 $ — $ — $ 38,677 Corporate bonds 46,677 — (27) 46,650 Agency bonds 124,466 12 (44) 124,434 Commercial paper 23,277 11 — 23,288 U.S. government bonds 7,675 — (8) 7,667 Total financial assets $ 240,772 $ 23 $ (79) $ 240,716 Reported as: Cash and cash equivalents $ 63,723 Short-term investments 176,993 $ 240,716 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value 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 periods presented, 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 December 31, 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.

Inventory

Inventory	12 Months Ended
	Dec. 31, 2015
Inventory Disclosure [Abstract]
Inventory	5. Inventory The Company began capitalizing inventory in October 2015 once the FDA approved Veltassa. Inventories consist of the following (in thousands): December 31, 2015 2014 Raw materials $ 4,761 $ — Work in process 3,943 — Finished goods 147 — Total inventory $ 8,851 $ —

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Property and Equipment	6. Property and Equipment The following table is a summary of property and equipment (in thousands): December 31, 2015 2014 Machinery and equipment $ 3,715 $ 2,829 Computers and software 4,300 657 Leasehold improvements 2,129 6,135 Furniture and fixtures 3,290 1,009 13,434 10,630 Less accumulated depreciation and amortization (3,807 ) (7,163 ) $ 9,627 $ 3,467 Property and equipment depreciation and amortization expense was $2.8 million, $4.8 million and $1.0 million for the years ended December 31, 2015, 2014 and 2013, respectively.

Accrued Liabilities

Accrued Liabilities	12 Months Ended
	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued Liabilities	7. Accrued Liabilities Accrued liabilities consisted of the following (in thousands): December 31, 2015 2014 Accrued contract manufacturing $ 26,371 $ 6,655 Accrued accounts payable 10,717 898 Accrued professional and consulting services 355 184 Accrued clinical trial expenses 201 41 Accrued interest 93 — $ 37,737 $ 7,778

Borrowings

Borrowings	12 Months Ended
	Dec. 31, 2015
Debt Disclosure [Abstract]
Borrowings	8. Borrowings Line of Credit In July 2008, the Company entered into a $1.5 million equipment line of credit. The terms of repayment range from 36 months to 42 months, and the interest rate is fixed at 8%. During the year ended December 31, 2012, the equipment line of credit was fully repaid in accordance with the contractual terms. In connection with the equipment line of credit, the Company issued warrants to purchase 2,616 shares of Series A-1 convertible preferred stock at an exercise price of $17.20. The warrants are exercisable upon issuance and expire ten years from the date of grant (July 2008). The aggregate value of the warrants on the date of issuance was $17,000, which was recorded as a liability and as debt issuance costs, which were amortized to interest expense over the term of the line of credit using the effective interest rate method. Upon the Company’s IPO during November 2013, the warrants for convertible preferred stock were converted to warrants for common stock and the related liability was re-classified to equity. As of December 31, 2015, these warrants were still outstanding. Line of Credit In May 2013, the Company entered into a $1.6 million equipment line of credit with a bank. The equipment line will be repaid in 36 equal monthly installments, and the interest rate is fixed at 5.75%. The Company will be required to make a final payment of 9.25% of the amounts advanced. The outstanding balance on the credit line is secured by a first priority lien over all equipment purchased using the line of credit. In connection with the Company’s equipment line of credit, the Company issued a warrant to purchase 6,968 shares of Series C-1 convertible preferred stock at an exercise price of $9.1848. Upon the Company’s IPO in November 2013, the warrants to purchase convertible preferred stock were converted to warrants to purchase common stock and were exercised in 2014. The equipment line of credit 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 term loan. The Company utilized $1.3 million of the line of credit in the second quarter of 2013, and the remaining $0.3 million balance available under the line of credit expired unused on June 30, 2013. As of December 31, 2015, principal of $0.2 million was outstanding under the line of credit, and the Company was in compliance with all required covenants. 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. On December 17, 2015, the Company entered into the Fifth Amendment to the Amended Loan Agreement. Under the Fifth Amendment, payments on the $15.0 million loan will be interest only through January 2017, followed by 30 months of equal monthly payments of interest and principal. The Company is 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 in connection with the Original Agreement. Upon the Company’s IPO in November 2013, the warrants to purchase convertible preferred stock were converted to warrants to purchase common stock. 13,609 warrants were exercised during 2014, resulting in the net issuance of 7,808 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 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. 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 financial statements. As of December 31, 2015 the estimated fair value of the contingent put option liability was $0.1 million, which was determined by using a risk-neutral valuation model, see Note 3 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 December 31, 2015, a principal amount of $15.0 million was outstanding under the Amended Loan Agreement, as amended, and the Company was in compliance with all required covenants.

Collaboration and License Agree

Collaboration and License Agreement	12 Months Ended
	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaboration and License Agreement	9. 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 year ended December 31, 2015, revenue of $18.6 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 December 31, 2015, no milestones have been triggered under the License Agreement.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	10. 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 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 the parties disagree regarding the feasibility or price of certain specification changes, or with notice at least 24 months in advance, (ii) by Lanxess with notice if the Company fails to issue certain purchase orders, or with notice at least 24 months in advance, (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. 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. These payments are recorded in other assets and were being amortized to research and development expenses prior to FDA approval 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 research and development expense, but as part of the cost basis of inventory. Lanxess will have full ownership of the purchased equipment and may manufacture other products with the modified plant when not occupied by the production of API for Veltassa. 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 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, which are recorded in other assets. These payments are amortized in accordance with the units produced by the facility. The amortization cost is included 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 are amortized in accordance with the period over which the Company expects to derive future economic value 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 Patheon Supply Agreement as of December 31, 2015. These amounts are based on estimates of future timing, quantity discounts and manufacturing efficiencies (in thousands): 2016 $ 43,495 2017 68,006 2018 71,922 2019 59,304 Total future minimum payments $ 242,727 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 Company’s previous lease provided the Company with a tenant improvement allowance in order for the Company to complete an office renovation and a lab build out. The Company accounted for the aggregate tenant improvement allowance received as leasehold improvement assets and as a deferred rent liability. These leasehold improvement assets were being amortized to depreciation expense over the shorter of the period from which the improvements were placed into service until the end of their useful life or until the end of the lease term. The deferred rent liability attributable to the leasehold improvement allowance was being amortized over the lease term as a credit to rent expense. Upon the execution of the Lease, the remaining net book value of the leasehold improvement assets and other assets to be abandoned upon the termination of the previous lease and the remaining deferred rent liability attributable to the improvement allowance were amortized or depreciated on a straight-line basis through February 28, 2015, which is the date the Company ceased using the premises. As of December 31, 2014, the remaining $1.5 million net book value of the leasehold improvements and other assets to be abandoned upon the termination of the previous lease and the remaining deferred rent liability of $1.2 million was amortized or depreciated over the estimated remaining two months of the previous 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 December 31, 2015 are as follows (in thousands): 2016 $ 3,761 2017 3,941 2018 4,034 2019 4,147 2020 4,271 Thereafter 18,808 Total future minimum payments $ 38,962 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 moving and tenant improvement related costs of which the Company used $0.8 million as of December 31, 2015. Amounts utilized of the additional allowance will increase future minimum operating lease payments Rent expense was $2.2 million, $(2.1) million and $1.1 million for the years ended December 31, 2015, 2014 and 2013, respectively. The Company recognized rent expense on a straight-line basis over the lease term. The negative rent expense of $2.1 million incurred in 2014 is primarily attributable to the accelerated amortization of the deferred rent liability attributable to the leasehold improvement allowance caused by the termination of the previous lease. Indemnification In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. The Company also has indemnification obligations to its officers and directors for specified events or occurrences, subject to some limits, while they are serving at the Company’s request in such capacities. There have been no claims to date and the Company has director and officer insurance that may enable the Company to recover a portion of any amounts paid for future potential claims. The Company believes the fair value of these indemnification agreements is minimal. Accordingly, the Company has not recorded any liabilities for these agreements as of December 31, 2015.

Technology Agreement

Technology Agreement	12 Months Ended
	Dec. 31, 2015
Goodwill And Intangible Assets Disclosure [Abstract]
Technology Agreement	11. Technology Agreement During 2007, the Company acquired certain assets from Ilypsa, Inc. (Ilypsa), a wholly owned subsidiary of Amgen, Inc. (Amgen), consisting of certain property and equipment and intangible assets primarily relating to Ilypsa’s nonabsorbed polymer therapeutics clinical development programs. During November 2009, the Company purchased from Ilypsa certain rights Ilypsa had retained in one of the clinical development programs that the Company had acquired in 2007 under an amended intellectual property agreement (the Amended Agreement). The Amended Agreement also obligated the Company to make milestone payments to Ilypsa (Amgen) upon occurrence of certain events related to this program. In February 2013, the Company dosed its first patient in a pivotal clinical trial that is evaluating Veltassa for the treatment of hyperkalemia and in March 2013, the Company made a $12.5 million milestone payment to Ilypsa (Amgen) in accordance with the Amended Agreement. Further, upon a change in control transaction, an additional payment could be owed to Ilypsa (Amgen) ranging from 6.7% to 10% of the purchase price, less certain expenses, up to a total of $30.0 million. The Company has no obligation to pay royalties on future sales of Veltassa to Ilypsa (Amgen).

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders' Equity (Deficit)	12 Months Ended
	Dec. 31, 2015
Stockholders Equity Note [Abstract]
Convertible Preferred Stock and Stockholders' Equity (Deficit)	12. Convertible Preferred Stock and Stockholders’ Equity (Deficit) Convertible Preferred Stock During the year ended December 31, 2012, the Company issued 7,076,901 shares of Series C-1 convertible stock at a price of $9.1848 per share for aggregate proceeds of $65.0 million. Per the terms of the Series C Stock and Warrant Purchase Agreement, as amended (the “Series C Agreements”) if purchasers of Series C-1 shares purchased in excess of 100% of their pro rata share, they were issued warrants to purchase two shares of Series C-1 for each Series C-1 share purchased in excess of their pro rata share. The Company issued warrants to purchase 2,076,643 shares of Series C-1 convertible stock that were immediately exercisable, have an exercise price of $0.17 per share and have a five year contractual life. The terms of the Series C Agreements also required the holders of Series C-1 shares to purchase Series C-2 shares for $9.1848 per share in a second financing (the Series C-2 Financing) which would occur upon the Company’s cash balance falling below a defined level, or upon the election of holders of more than 50% of the Series C-1 shares. Notwithstanding this, each purchaser’s obligation to purchase shares at the Series C-2 closing shall terminate if holders of shares of convertible preferred stock representing at least 55% of the total number of shares of common stock into which the outstanding convertible preferred stock could be converted, voting together as a single class elect to terminate such obligation. During October 2013, the Company issued 1,633,126 shares of Series C-2 convertible preferred stock at a price of $9.1848 per share for aggregate gross proceeds of $15.0 million. Per the terms of the Series C Preferred Stock and Warrant Purchase Agreement, as amended, if purchasers of Series C convertible preferred stock purchased in excess of 100% of their pro rata share, they were issued warrants to purchase two shares of Series C for each Series C share purchased in excess of their pro rata share. The Company issued warrants to purchase 479,221 shares of Series C-2 convertible preferred stock that were immediately exercisable, have an exercise price of $0.17 per share and had a five year contractual life. The warrants were valued at $15.308 per share at the time of issuance based on their intrinsic value. The warrants were determined to be a deemed dividend to preferred stockholders, and the $7.3 million fair value was been classified as an increase to stockholders’ equity (deficit) and as a convertible preferred stock warrant liability. Upon the Company’s IPO during November 2013, the warrants to purchase convertible preferred stock were exercised into 472,187 shares of common stock. As a result of this conversion, the warrants ceased to be re-measured and the warrant liability was reclassified to equity. As of December 31, 2013, the Company had no outstanding convertible preferred stock. Upon the Company’s IPO during November 2013, all outstanding shares of convertible preferred stock converted into 18,924,883 shares of common stock. Shelf Registration Statements 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 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 may be issued and 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 offering program at an average price of $32.17 for an aggregate offering price 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 initial at-the-market offering in full. In March 2015, the Company sold 4,485,000 shares of common stock in an underwritten offering at a price to the public 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 offering-related transaction expenses. On November 4, 2015, 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 $300.0 million of its common stock, preferred stock, debt securities, warrants and/or units; and (b) as part of the $300.0 million, the offering, issuance and sale by the Company of up to a maximum aggregate offering price of $75.0 million of its common stock that may be issued and sold under a sales agreement with Cantor Fitzgerald & Co in one or more at-the-market offerings. As of December 31, 2015, no shares had been sold pursuant to its current at-the-market offering program. During January and February 2016, the Company sold 2,509,372 shares pursuant to its current at-the-market offering at a weighted-average sale price of $18.18 for an aggregate offering price of $45.6 million, and the Company received aggregate net proceeds of $44.2 million. Common Stock The Company has issued options to purchase common stock that are subject to vesting and allow for early exercise. Unvested common stock is issued upon the early exercise of the options. The Company reserves the right to repurchase the unvested common stock in the event of employee termination. At the Company’s option, the repurchase price equals the lower of the share price paid by the employees or the fair market value as of the date of repurchase. The shares purchased by the employees pursuant to the early exercise of stock options are not deemed, for accounting purposes, to be issued until those shares vest. The cash received in exchange for exercised and unvested shares related to stock options granted is recorded as a liability for the early exercise of stock options on the accompanying balance sheets and will be transferred into common stock and additional paid-in capital as the shares vest. As of December 31, 2015, 2014 and 2013, there are 282, 1,276 and 5,125 shares respectively, of unvested common stock with an aggregate purchase price of $1,000, $6,000 and $23,000, respectively that are subject to repurchase at prices ranging from $3.96 to $7.40 per share, and are classified as a component of other accrued liabilities. The following table summarizes information about unvested common stock (in thousands except per share amounts): Number of Shares Weighted- Average Purchase Price ($) Unvested shares at December 31, 2012 7 4.13 Shares sold 23 4.12 Shares vested (25 ) 4.01 Shares repurchased — — Unvested shares at December 31, 2013 5 3.78 Shares sold — — Shares vested (3 ) 4.49 Shares repurchased (1 ) 5.27 Unvested shares at December 31, 2014 1 $ 4.49 Shares sold — — Shares vested (1 ) 4.21 Shares repurchased — — Unvested shares at December 31, 2015 — —

Equity Compensation Plans and S

Equity Compensation Plans and Stock Based Compensation	12 Months Ended
	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Compensation Plans and Stock Based Compensation	13. 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 December 31, 2015, reserved total of 447,642 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 2015, the Company’s board of directors approved amendments to the Inducement Plan to increase the number of shares reserved for issuance by 2,000,000 shares. As of December 31, 2015, 1,757,533 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, the ESPP was initiated in August 2014. As of December 31, 2015, the Company has reserved 563,134 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 year ended December 31, 2015. The following table summarizes option activity under the 2007 Plan, the 2013 Plan, and the Inducement Plan and related information (in thousands, except per share and contractual term amounts): Shares Available for Grant Shares Subject to Outstanding Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value (in years) Options outstanding at December 31, 2012 67 2,163 4.13 Additional shares reserved under plan 2,571 — — Options granted (1,444 ) 1,444 7.91 Options exercised — (23 ) 4.12 Options forfeited 39 (39 ) 4.12 Options outstanding at December 31, 2013 1,233 3,545 5.63 Additional shares reserved under the Inducement plan 1,000 — — Options granted (1,004 ) 1,004 25.63 Restricted stock units granted (130) — — Options exercised — (675 ) 4.31 Options forfeited 61 (61 ) 10.95 Restricted stock units cancelled 7 — — Options outstanding at December 31, 2014 1,167 3,813 11.05 Additional shares reserved under Plan 3,402 — — Options granted (2,262) 2,262 27.92 Restricted stock units granted (989) — 22.05 Options exercised — (781) 5.06 Options forfeited 343 (343) 19.88 Restricted stock units cancelled 30 — 25.61 Balances outstanding at December 31, 2015 1,691 4,951 $ 19.09 8.2 $ 50,248 Vested and expected to vest at December 31, 2015 — 4,719 $ 18.78 8.2 $ 49,297 Vested at December 31, 2015 — 1,676 $ 10.07 6.7 $ 31,023 The aggregate intrinsic values of options outstanding and exercisable, vested and expected to vest were calculated as the difference between the exercise price of the options and the NASDAQ listing fair value of the Company’s common stock as of December 31, 2015. The weighted-average grant-date fair value of options granted during the years ended December 31, 2015, 2014, and 2013 was $19.78, $19.77, and $6.23, respectively. The total fair value of options that vested during the years ended December 31, 2015, 2014, 2013 was $13.2 million, $9.1 million, and $5.0 million, respectively. The intrinsic value (the difference between the fair value of the Company’s common stock at the exercise date and the exercise price) of the options exercised was $20.8 million, $14.9 and $0.2 million during the years ended December 31, 2015, 2014 and 2013, respectively. Included in the option activity tables above are 220,000 performance-based options awarded in November 2015. The number of options that may vest, if any, relate to the achievement of certain pre-established corporate performance-related goals. Stock-Based Compensation Expense Stock-based compensation expense included in the Company’s consolidated statements of operations is as follows (in thousands): Year Ended December 31, 2015 2014 2013 Research and development: Employees $ 5,168 $ 1,657 $ 776 Non-employee consultants 3,325 4,045 1,659 Selling, general and administrative: Employees 10,795 3,980 1,474 Non-employee consultants — 13 — Total stock-based compensation expense $ 19,288 $ 9,695 $ 3,909 The total unrecognized stock-based compensation expense related to stock options and ESPP stock purchase rights at December 31, 2015, was $51.3 million, and is expected to be recognized over a weighted-average period of approximately 3.0 years. The fair value of each option award is estimated on the date of grant using the Black-Scholes option valuation model. Since the Company has only been publicly traded for a short period and does not have adequate trading history for its common stock, the expected stock price volatility was calculated based on the average historical volatility for comparable publicly traded pharmaceutical companies. The Company selected companies with comparable characteristics, including enterprise value, risk profiles, position within the industry, and with historical share price information sufficient to meet the expected life of Relypsa’s stock-based awards. The expected term of the options is based on the average period the stock options are expected to remain outstanding. As the Company does not have sufficient historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior, the expected term is calculated as the midpoint between the weighted-average vesting term and the contractual expiration period also known as the simplified method. The risk-free rate is based on U.S. Treasury zero coupon issues with remaining terms consistent with the expected terms of the stock options, as determined at the time of grant. To date, the Company has not declared or paid any cash dividends and does not have any plans to do so in the future. Therefore, the Company used an expected divided yield of zero. The following table illustrates the assumptions for the Black-Scholes option-pricing model used in determining the fair value of options granted to employees: Year Ended December 31, 2015 2014 2013 Expected volatility 82-92 % 87-109 % 95-110 % Expected dividends 0 % 0 % 0 % Expected term (in years) 5-6 6 6 Risk-free rate 1.3-1.9 % 1.6-2.0 % 1.1-1.8 % In the year ended December 31, 2013, the Company granted 290 common stock options with an exercise price of $7.40 per share in exchange for services from non-employees. No common stock options were granted to non-employees in the years ended December 31, 2015 and 2014. Outstanding non-employee options are primarily related to employees who converted to consultants. Stock-based compensation expense related to stock options granted to non-employees is measured and recognized as the stock options are earned. The Company believes that the estimated fair value of the stock options is more readily measurable than the fair value of the services rendered. The fair value of non-employee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions: Year Ended December 31, 2015 2014 2013 Expected volatility 83-92 % 92 % 91%-122 % Expected dividends 0 % 0 % 0 % Expected term (in years) 6-9 7-9 5-10 Risk-free rate 1.5-2.1 % 1.8-2.0 % 1.3-2.7 % Restricted Stock Units During 2015, the Company granted restricted stock unit (“RSUs”) awards subject to performance-vesting criteria and subject to time-based-vesting criteria from the 2013 Plan. RSUs subject to performance vesting criteria consist of the right to receive shares of common stock, subject to achievement of time-based criteria and certain corporate performance-related goals over a specified period. 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. 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 RSU activity for the twelve months ended December 31, 2015 (in thousands, except per share amounts): Restricted Stock Units Number of Shares Weighted-Average Grant Date Fair Value Per Share Nonvested at December 31, 2014 123 $ 26.85 Granted 989 22.05 Vested (40) 26.11 Canceled (30) 25.61 Nonvested at December 31, 2015 1,042 $ 22.35 Included in the RSU activity table above are 186,268 performance based awards awarded in November 2015. The number of shares that may vest, if any, relate to the achievement of certain pre-established corporate performance-related goals. The total unrecognized stock-based compensation expense related to non-vested RSUs at December 31, 2015, was $21.3 million, and is expected to be recognized over a weighted-average period of approximately 2.8 years.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Taxes	14. Income Taxes The Company did not record a provision or benefit for income taxes during the years ended December 31, 2015, 2014, and 2013. The reconciliation of the statutory federal income tax rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2015 2014 2013 Federal statutory rate 34.0 % 34.0 % 34.0 % State statutory rate 0.8 5.8 5.8 Research and development tax credit 2.0 2.3 1.7 Permanent item (2.0 ) (1.0 ) (1.0 ) Valuation allowance (34.8 ) (41.1 ) (40.5 ) Provision for income taxes — % — % — % At December 31, 2015, the Company had total deferred tax assets of $163.8 million. Due to uncertainties surrounding its ability to generate future taxable income to realize these tax assets, a full valuation has been established to offset total deferred tax assets. The tax effects of temporary differences and carryforwards that give rise to significant portions of the deferred tax assets are as follows (in thousands): December 31, 2015 2014 2013 Federal and state net operating loss carryforwards $ 133,631 $ 91,604 $ 64,768 Federal and state research and development credits 8,210 6,253 4,703 Depreciation 2,825 3,036 1,538 Intangible assets — — (6 ) Accruals and reserves 19,162 7,900 4,942 163,828 108,793 75,945 Valuation allowance (163,828 ) (108,793 ) (75,945 ) Net deferred tax assets $ — $ — $ — No tax benefit has been recorded through December 31, 2015, 2014 and 2013, because of the Company’s history of operating losses, and a full valuation allowance has been provided. The Company’s valuation allowance increased by $55.0 million, $32.8 million and $27.9 million for the years ended December 31, 2015, 2014 and 2013, respectively. As of December 31, 2015, the Company had net operating loss carryforwards of approximately $387.6 million and $252.4 million that may be available, subject to the limitations described below, to reduce future taxable income, if any, for federal and California state income tax purposes, respectively. The federal and state net operating loss carryforwards will begin to expire in 2027 and 2017, respectively. Included in the gross amount, approximately $24.7 million of net operating loss is created by excess stock option deductions. A credit to additional paid-in capital will be recorded when the excess stock option deduction reduces the income tax payable. Additionally, the future utilization of the net operating loss carry forwards to offset future taxable income may be subject to an annual limitation, pursuant to Internal Revenue Code Section 382, as a result of ownership changes that may have occurred previously or that could occur in the future. The Company performed an initial analysis under Section 382. As a result of this analysis, the Company removed the deferred tax assets for net operating losses of $28.6 million generated through December 31, 2014 from its deferred tax asset schedule and have recorded a corresponding decrease to the valuation allowance. When this analysis is updated, the deferred tax asset-schedule and associated valuation allowance will be updated. Due to the existence of the valuation allowance, future changes in unrecognized tax benefits will not impact the Company’s effective tax rate. As of December 31, 2015, the Company had research and development credit carryforwards of approximately $7.1 million and $6.8 million available to reduce future tax expense, if any, for federal and California state income tax purposes, respectively. The federal credits expire beginning in 2027, and the California credits carry forward indefinitely. Further, the future utilization of the research and development credit carryforwards are also subject to the limitations as discussed above. The Company recognizes uncertain tax positions when it is more-likely-than-not, based on the technical merits, that the position will not be sustained upon examination. A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows (in thousands): 2015 2014 2013 Balance at January 1 $ 3,189 $ 2,476 $ 1,836 Increases related to current period tax positions 1,198 713 588 Increases related to prior period tax positions 5,478 — 52 Balance as of December 31 $ 9,865 $ 3,189 $ 2,476 As of December 31, 2015, due to a valuation allowance against the Company’s deferred tax assets, none of the unrecognized tax benefits, if recognized, would affect the Company’s effective tax rate. The Company is subject to U.S. federal and state income tax examination for fiscal tax years ending 2012 through 2015. The U.S. federal and U.S. state taxing authorities may choose to audit tax returns for tax years beyond the statute of limitation period due to significant tax attribute carryforwards from prior years, making adjustments only to carryforward attributes. The Company’s policy is to include interest and penalties related to unrecognized tax benefits within the Company’s provision for income taxes and to date have not recorded any interest or penalties. The Company is not currently under an examination and does not expect material changes to its unrecognized tax benefits in the next twelve months.

401(k) Savings Plan

401(k) Savings Plan	12 Months Ended
	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
401(k) Savings Plan	15. 401(k) Savings Plan The Company sponsors a 401(k) Plan to provide retirement and incidental benefits for its employees. Employees may contribute from 1% to 90% of their annual compensation to the 401(k) Plan, limited to a maximum annual amount as set periodically by the Internal Revenue Service. The Company did not make any matching contributions to the 401(k) Plan in 2015, 2014, or 2013.

Related Party Transaction

Related Party Transaction	12 Months Ended
	Dec. 31, 2015
Related Party Transactions [Abstract]
Related Party Transaction	16. Related Party Transaction Recovery of Stockholder Short-Swing Profit In December 2015, the Company received a payment of $7.4 million from a related-party stockholder in disgorgement of short-swing profits under Section 16(b) of the Securities Exchange Act of 1934, as amended. The Company recognized these proceeds as a capital contribution from a stockholder, and reflected a corresponding increase to additional paid-in capital in its consolidated statements of convertible preferred stock and stockholder’s equity.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2015
Subsequent Events [Abstract]
Subsequent Events	17. Subsequent Events During January and February 2016, the Company sold 2,509,372 shares pursuant to its at-the-market offering program at a weighted- average sale price of $18.18 for an aggregate offering price of $45.6 million, and the Company received aggregate net proceeds of $44.2 million.

Selected Quarterly Financial Da

Selected Quarterly Financial Data (unaudited)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	18. Selected Quarterly Financial Data (unaudited) The following table contains quarterly financial information for 2015 and 2014. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. December 31, September 30, June 30, March 31, December 31, September 30, June 30, March 31, 2015 2015 2015 2015 2014 2014 2014 2014 (In thousands, except share and per share data) Revenues: License and collaboration $ 11,960 $ 6,590 $ — $ — $ — $ — $ — $ — Operating expenses: Research and 26,500 32,391 18,627 15,780 16,596 11,647 11,075 10,909 Selling, general and 44,056 25,255 20,340 13,487 10,486 7,311 5,322 4,795 Total operating 70,556 57,646 38,967 29,267 27,082 18,958 16,397 15,704 Loss from operations (58,596) (51,056) (38,967) (29,267) (27,082) (18,958) (16,397) (15,704) Interest and other income 613 30 188 84 69 17 36 27 Interest expense (343) (442) (478) (482) (635) (494) (376) (391) Net loss (58,326) (51,468) (39,257) (29,665) (27,648) (19,435) (16,737) (16,068) Net loss per share basic and $ (1.40) $ (1.24) $ (0.95) $ (0.78) $ (0.80) $ (0.57) $ (0.51) $ (0.54) Weighted-average common 41,785,176 41,633,410 41,490,003 37,829,239 34,368,776 34,064,780 33,141,384 29,710,415

Summary of Significant Accoun27

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2015
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying consolidated financial statements include the accounts of Relypsa and its wholly-owned subsidiary, Relypsa UK LTD, and have been prepared in accordance with U.S. generally accepted accounting principles (“US GAAP”). Intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of consolidated financial statements in conformity with US 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, inventories, clinical trial accruals, manufacturing accruals, fair value of assets and liabilities, 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.
Liquidity	Liquidity The Company has never been profitable and, as of December 31, 2015, the Company has an accumulated deficit of $484.4 million. The Company has incurred net losses of approximately $178.7 million, $79.9 million and $73.8 million in the years ended December 31, 2015, 2014, and 2013, respectively. The Company may continue to incur substantial operating losses even after it begins to generate meaningful revenues from Veltassa. If the Company is unable to achieve the level of revenues from product sales during 2016 that is contemplated in its operating plan and the Company is unable to raise additional funds through public or private equity, debt financings or other sources, the Company has contingency plans to implement cost cutting actions to reduce its working capital requirements beginning as early as the third quarter of 2016. As part of such plans, the Company will prioritize necessary and appropriate steps to enable the continued operations of the business and preservation of the value of its assets beyond the next twelve months, including, but not limited to, reducing commercial, marketing, medical affairs, clinical trials, research, manufacturing, and personnel-related costs, and reducing capital equipment investments and other discretionary expenditures that are within its control. These reductions in expenditures, if required, may have an adverse impact on the Company’s ability to achieve certain of its planned objectives during 2016, which could have a material adverse effect on the business, results of operations, and financial condition. The Company will need to generate significant revenues to achieve profitability and may never do so.
Cash Equivalents	Cash Equivalents The Company considers all highly liquid investments purchased with original maturities of 90 days or less at the date of purchase to be cash equivalents.
Investments	Investments Investments consist of debt securities which are classified as available-for-sale. Short-term investments have remaining maturities less than one year as of the balance sheet date. Long-term investments have remaining maturities greater than one year as of the balance sheet date. Investments are carried at fair value based upon quoted market prices or pricing models for similar securities. Unrealized gains and losses on available-for-sale securities are reported as a component of accumulated comprehensive income (loss). Realized gains or losses on the sale of securities are reported in interest and other income (expense), net and computed using the specific identification method.
Inventory	Inventory Inventory is composed of raw materials, intermediate materials, which are classified as work-in-process and finished goods, which are goods that are available for sale. Inventory costs include amounts related to third-party contract manufacturing, shipping costs, amortization of up-front payments to contract manufacturers, or CMOs, packaging services and manufacturing overhead. Inventory is carried at standard cost, which approximates weighted average cost. The Company has contracted with third party manufacturers that produce the raw and intermediate materials used in the production of Veltassa as well as the finished product. In connection with production of inventory, the Company may be required to provide payments to third party manufacturers in advance of transfer of title or risk of loss. These amounts are included in inventory as raw materials on the accompanying consolidated balance sheets. Inventories are stated at the lower of cost or market. If the Company identifies excess, obsolete or unsalable product, the Company will write down its inventory to its net realizable value in the period it is identified. The Company received FDA approval for Veltassa on October 21, 2015 and began capitalizing inventory starting in October 2015. Cost incurred prior to approval have been recorded as research and development expense in the consolidated statements of operations.
Accounts Receivable	Accounts Receivable The Company extends credit to customers for product sales resulting in accounts receivable. Customer accounts will be monitored for past due amounts. Past due accounts receivable, determined to be uncollectible, will be written off against the allowance for doubtful accounts. Allowances for doubtful accounts will be estimated based upon past due amounts, historical losses and existing economic factors, and are adjusted periodically. The accounts receivable are reported in the consolidated balance sheets, net of allowances for doubtful accounts. As of December 31, 2015, the Company had a trade accounts receivable balance of $0.5 million related to Veltassa product sales and there were no allowance for doubtful accounts at December 31, 2015.
Revenue Recognition	Revenue Recognition Revenue is recognized when (1) persuasive evidence of an arrangement exists, (2) delivery has occurred or services have been rendered, (3) the price is fixed and determinable and (4) collectability is reasonably assured. Revenues are deferred for fees received before earned or until no further obligations exist. The Company exercises judgment in determining that collectability is reasonably assured or that services have been delivered in accordance with the arrangement. The Company assess whether the fee is fixed or determinable based on the payment terms associated with the transaction and whether the sales price is subject to refund or adjustment. The Company assess collectability based primarily on the customer’s payment history and on the creditworthiness of the customer. Product Revenue The Company’s product revenues consist of U.S. sales of Veltassa and are recognized once the Company meets all four revenue recognition criteria described above. Veltassa was approved by the FDA on October 21, 2015 and the Company commenced shipments of Veltassa to specialty pharmacies and specialty distributors in late December 2015. The Company presently does not have the ability to estimate the extent of rebates or chargebacks or product that may ultimately be returned due to our lack of history with Veltassa product revenues at this time. Accordingly, the price is not considered to be deemed fixed and determinable at the time of the shipment to the specialty pharmacy or specialty distributor. Therefore, the Company recognizes revenue once the specialty pharmacy has filled the patient’s prescription for Veltassa or specialty distributor sells Veltassa. This approach is frequently referred to as the “sell-through” revenue recognition model. Under the sell-through approach, revenue is recognized when the specialty pharmacy provides product to a patient based on the fulfillment of a prescription or specialty distributor sells product to a hospital or other eligible entity. As of December 31, 2015, the Company had a deferred revenue balance of $0.5 million related to Veltassa product sales. Collaboration and License Revenue In August 2015, the Company entered into a collaboration and license agreement (License Agreement) with Vifor Fresenius Medical Care Renal Pharma (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. The upfront payment of $40.0 million was allocated to the 1) License and work on the submission of MAA deliverable, 2) the R&D deliverable and 3) the committee participation deliverable using the relative estimated selling price method. The Company estimated the best estimate of selling price (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 determination of the BESP of the license involved significant judgment regarding the patient populations in the Licensed Territory, the percent of patients that would be treated and receive payment coverage, the duration of treatment of patients, the time and probability to achieve regulatory and pricing approval, and an appropriate discount rate.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to a concentration of credit risk consist primarily of investments. The Company invests in money market accounts, U.S. Treasury notes, municipal bonds, agency bonds, corporate notes, certificates of deposit and commercial paper. Other than for obligations of the U.S. government, the Company’s policy is that no more than 5% of its investments may be concentrated in a single issuer. Bank deposits are held by a single financial institution having a strong credit rating and these deposits may at times be in excess of insured limits. The Company is exposed to credit risk in the event of a default by the financial institutions holding its cash, cash equivalents and short-term investments and issuers of investments to the extent recorded on the balance sheets. The Company’s investment policy limits investments to certain types of debt securities issued by the U.S. government, its agencies and institutions with investment-grade credit ratings and places restrictions on maturities and concentration by type and issuer.
Restricted Cash	Restricted Cash Restricted cash related to the Company’s leases consist of irrevocable letters of credit that are collateralized by restricted deposits held at the Company’s bank over a term that is consistent with the corresponding lease. Restricted cash also consists of a letter of credit related to the Company’s corporate credit card program that is collateralized by a restricted deposit at the Company’s bank.
Property and Equipment	Property and Equipment Property and equipment are stated at cost less accumulated depreciation and amortization. Depreciation and amortization is calculated using the straight-line method over the estimated useful lives of the related assets, ranging from three to seven years. Leasehold improvements are amortized over the shorter of the lease term or the estimated useful lives of the respective assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company identifies and records impairment losses on long-lived assets used in operations when events and changes in circumstances indicate that the carrying amount of an asset might not be recoverable. Recoverability is measured by comparing the anticipated undiscounted future net cash flows to the related asset’s carrying value. If an asset is considered impaired, the asset is written down to fair value, which is determined based either on discounted cash flows or appraised value, depending on the nature of the asset. The Company has not recorded any impairment losses during the periods presented.
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.
Clinical Trial Accruals	Clinical Trial Accruals Clinical trial costs are a component of research and development expenses. The Company accrues and expenses clinical trial activities performed by third parties based upon actual work completed in accordance with agreements established with clinical research organizations and clinical sites. The Company determines the actual costs through discussions with internal personnel and external service providers as to the progress or stage of completion of trials or services and the agreed-upon fee to be paid for such services.
Contract Manufacturing Accruals	Contract Manufacturing Accruals Contract manufacturing costs related to pre-commercial activities are a component of research and development expense. The Company accrues and expenses contract manufacturing related to pre-commercial activities performed by third parties based upon actual work or the estimated amount of work completed in accordance with agreements established with contract manufacturing organizations. The Company determines the actual costs or estimates of the costs through discussions with internal personnel and external service providers as to the pre-commercial manufacturing activities that were performed or completed and the agreed-upon fee to be paid for such services. Additionally, there may be accruals related to commercial activities that are recorded as a component of inventory.
Income Taxes	Income Taxes The Company uses the liability method to account for income taxes. Under this method, deferred tax assets and liabilities are determined based on differences between the financial statement carrying amounts of existing assets and liabilities and their tax bases. Deferred tax assets and liabilities are measured using enacted tax rates applied to taxable income in the years in which those temporary differences are expected to be recovered or settled. A valuation allowance is established when necessary to reduce deferred tax assets to the amount expected to be realized. Financial statement effects of uncertain tax positions are recognized when it is more–likely-than-not, based on the technical merits of the position, that they will be sustained upon examination. Interest and penalties related to unrecognized tax benefits are included within the provision for income tax.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation based on the fair value of the share-based awards that are ultimately expected to vest. The fair value of employee stock options granted is estimated on the date of grant using the Black-Scholes option pricing model, and is recognized in expense over the requisite service period using the straight-line method, if performance or service conditions are expected to be achieved. Forfeiture estimates are adjusted to the extent that actual forfeitures differ from the prior estimates. The fair value of restricted stock unit awards used in the Company’s expense recognition method is based on the number of restricted stock units granted and the closing price of the Company’s common stock on the date of the grant. Such value is recognized as an expense over the requisite service period using the straight-line method, net of estimated forfeitures. The Company adopted an employee stock purchase plan (ESPP) on November 2013 and in August 2014, the ESPP was initiated, pursuant to which eligible employees can purchase shares of the Company’s common stock at a price per share equal to the lesser of 85% of the fair market value on the first day of the offering period or 85% of the fair market value on the purchase date. The Company records the expense attributable to nonemployee services paid with share-based awards based on the estimated fair value of the awards determined using the Black-Scholes option pricing model. The measurement of stock-based compensation for nonemployees is subject to periodic adjustments as the options vest, and the expense is recognized over the period during which services are received.
Convertible Preferred Stock	Convertible Preferred Stock Prior to the Company’s IPO, the Company recorded all shares of convertible preferred stock at their respective fair values, net of issuance costs, on the dates of issuance. Upon completing the IPO, all shares of the Company’s convertible preferred stock then outstanding converted into 18,924,883 shares of our common stock.
Convertible Preferred Stock Warrant Liability	Convertible Preferred Stock Warrant Liability Prior to the Company’s IPO, freestanding warrants for shares that were either puttable or redeemable were classified as liabilities on the balance sheets and were carried at their estimated fair value. The preferred stock underlying the warrants was redeemable in certain circumstances. At the end of each reporting period, changes in the estimated fair value during the period were recorded in interest and other income (expense), net. The consummation of the Company’s IPO resulted in the conversion of all classes of the Company’s preferred stock into common stock. Upon such conversion of the underlying classes of preferred stock, the warrants were reclassified as a component of equity and were no longer subject to re-measurement.
Deferred Rent	Deferred Rent Rent expense is recognized on a straight-line basis over the noncancelable term of the Company’s operating lease and, accordingly, the Company records the difference between cash rent payments and the recognition of rent expense as a deferred rent liability. In accordance with the terms of the lease for the Company’s office and laboratory space as of December 31, 2015, the Company also recorded lessor-funded lease incentives, such as reimbursable leasehold improvements, as a deferred rent liability, which is amortized as a reduction of rent expense over the noncancelable term of its operating lease.
Net Loss per Common Share Attributable to Common Stockholders	Net Loss per Common Share Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per share of common stock is the same as basic net loss per share of common stock, since the effects of potentially dilutive securities are antidilutive. The net loss per share of common stock attributable to common stockholders is computed using the two-class method required for participating securities. All series of the Company’s convertible preferred stock are considered to be participating securities as they are entitled to participate in undistributed earnings with shares of common stock. Due to the Company’s net loss, there is no impact on earnings per share calculation in applying the two-class method since the participating securities have no legal requirement to share in any losses. 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): Year Ended December 31, 2015 2014 2013 Warrants to purchase common stock 15 56 64 Options to purchase common stock 4,951 3,813 3,545 Restricted stock units 1,042 123 — Common stock subject to repurchase — 1 5 6,008 3,993 3,614
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 In November 2015, FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes
Organization	Organization Relypsa, Inc. (Relypsa or the Company) is a biopharmaceutical company dedicated to the development and commercialization of polymer-based drugs to treat conditions that are often overlooked and undertreated, but that can have a serious impact on patients’ lives and even be life-threatening. On October 21, 2015, the U.S. Food and Drug Administration (FDA) approved the Company’s first drug, Veltassa ® Veltassa in December 2015 and it is available for prescription to patients in the United States through a limited number of specialty pharmacies and specialty distributors.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 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): Year Ended December 31, 2015 2014 2013 Warrants to purchase common stock 15 56 64 Options to purchase common stock 4,951 3,813 3,545 Restricted stock units 1,042 123 — Common stock subject to repurchase — 1 5 6,008 3,993 3,614

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 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 consolidated financial instruments that were measured at fair value on a recurring basis as of December 31, 2015 and 2014 (in thousands): Level 1 Level 2 Level 3 Total December 31, 2015 Financial assets: Money market funds $ 37,205 $ — $ — $ 37,205 Corporate bonds — 46,650 — 46,650 Agency bonds — 124,434 — 124,434 Commercial paper — 23,288 — 23,288 U.S. government bonds — 7,667 — 7,667 Total financial assets $ 37,205 $ 202,039 $ — $ 239,244 Liabilities: Contingent put option liability $ — $ — $ 93 $ 93 Total financial liabilities $ — $ — $ 93 $ 93 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 financial liabilities $ — $ — $ 233 $ 233
Summary of Changes in Estimated Fair Value of Level 3 Instruments Measured at Fair Value on Recurring Basis	As of December 31, 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 level 3 instruments, which are measured at fair value on a recurring basis (in thousands): Balance as of December 31, 2013 $ — Issuance of contingent put option liability 110 Increase in fair value included in other income (expense) 123 Balance as of December 31, 2014 233 Decrease in fair value included in other income (expense) (140 ) Balance as of December 31, 2015 $ 93

Cash, Cash Equivalents, and S30

Cash, Cash Equivalents, and Short-Term Investments (Tables)	12 Months Ended
	Dec. 31, 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 Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value December 31, 2015 Cash and money market funds $ 38,677 $ — $ — $ 38,677 Corporate bonds 46,677 — (27) 46,650 Agency bonds 124,466 12 (44) 124,434 Commercial paper 23,277 11 — 23,288 U.S. government bonds 7,675 — (8) 7,667 Total financial assets $ 240,772 $ 23 $ (79) $ 240,716 Reported as: Cash and cash equivalents $ 63,723 Short-term investments 176,993 $ 240,716 Amortized Cost Gross Unrealized Gains Gross Unrealized Losses Estimated Fair Value 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

Inventory (Tables)

Inventory (Tables)	12 Months Ended
	Dec. 31, 2015
Inventory Disclosure [Abstract]
Schedule of Inventories	Inventories consist of the following (in thousands): December 31, 2015 2014 Raw materials $ 4,761 $ — Work in process 3,943 — Finished goods 147 — Total inventory $ 8,851 $ —

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2015
Property Plant And Equipment [Abstract]
Summary of Property and Equipment	The following table is a summary of property and equipment (in thousands): December 31, 2015 2014 Machinery and equipment $ 3,715 $ 2,829 Computers and software 4,300 657 Leasehold improvements 2,129 6,135 Furniture and fixtures 3,290 1,009 13,434 10,630 Less accumulated depreciation and amortization (3,807 ) (7,163 ) $ 9,627 $ 3,467

Accrued Liabilities (Tables)

Accrued Liabilities (Tables)	12 Months Ended
	Dec. 31, 2015
Payables And Accruals [Abstract]
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): December 31, 2015 2014 Accrued contract manufacturing $ 26,371 $ 6,655 Accrued accounts payable 10,717 898 Accrued professional and consulting services 355 184 Accrued clinical trial expenses 201 41 Accrued interest 93 — $ 37,737 $ 7,778

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 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 Patheon Supply Agreement as of December 31, 2015. These amounts are based on estimates of future timing, quantity discounts and manufacturing efficiencies (in thousands): 2016 $ 43,495 2017 68,006 2018 71,922 2019 59,304 Total future minimum payments $ 242,727
Schedule of Future Minimum Payments Under Operating Lease	The Company’s future minimum operating lease payments at December 31, 2015 are as follows (in thousands): 2016 $ 3,761 2017 3,941 2018 4,034 2019 4,147 2020 4,271 Thereafter 18,808 Total future minimum payments $ 38,962

Convertible Preferred Stock a35

Convertible Preferred Stock and Stockholders' Equity (Deficit) (Tables)	12 Months Ended
	Dec. 31, 2015
Stockholders Equity Note [Abstract]
Summary of Unvested Common Stock	The following table summarizes information about unvested common stock (in thousands except per share amounts): Number of Shares Weighted- Average Purchase Price ($) Unvested shares at December 31, 2012 7 4.13 Shares sold 23 4.12 Shares vested (25 ) 4.01 Shares repurchased — — Unvested shares at December 31, 2013 5 3.78 Shares sold — — Shares vested (3 ) 4.49 Shares repurchased (1 ) 5.27 Unvested shares at December 31, 2014 1 $ 4.49 Shares sold — — Shares vested (1 ) 4.21 Shares repurchased — — Unvested shares at December 31, 2015 — —

Equity Compensation Plans and36

Equity Compensation Plans and Stock Based Compensation (Tables)	12 Months Ended
	Dec. 31, 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, and the Inducement Plan and related information (in thousands, except per share and contractual term amounts): Shares Available for Grant Shares Subject to Outstanding Options Weighted- Average Exercise Price Per Share Weighted- Average Remaining Contractual Term Aggregate Intrinsic Value (in years) Options outstanding at December 31, 2012 67 2,163 4.13 Additional shares reserved under plan 2,571 — — Options granted (1,444 ) 1,444 7.91 Options exercised — (23 ) 4.12 Options forfeited 39 (39 ) 4.12 Options outstanding at December 31, 2013 1,233 3,545 5.63 Additional shares reserved under the Inducement plan 1,000 — — Options granted (1,004 ) 1,004 25.63 Restricted stock units granted (130) — — Options exercised — (675 ) 4.31 Options forfeited 61 (61 ) 10.95 Restricted stock units cancelled 7 — — Options outstanding at December 31, 2014 1,167 3,813 11.05 Additional shares reserved under Plan 3,402 — — Options granted (2,262) 2,262 27.92 Restricted stock units granted (989) — 22.05 Options exercised — (781) 5.06 Options forfeited 343 (343) 19.88 Restricted stock units cancelled 30 — 25.61 Balances outstanding at December 31, 2015 1,691 4,951 $ 19.09 8.2 $ 50,248 Vested and expected to vest at December 31, 2015 — 4,719 $ 18.78 8.2 $ 49,297 Vested at December 31, 2015 — 1,676 $ 10.07 6.7 $ 31,023
Schedule of Stock-Based Compensation Expense	Stock-based compensation expense included in the Company’s consolidated statements of operations is as follows (in thousands): Year Ended December 31, 2015 2014 2013 Research and development: Employees $ 5,168 $ 1,657 $ 776 Non-employee consultants 3,325 4,045 1,659 Selling, general and administrative: Employees 10,795 3,980 1,474 Non-employee consultants — 13 — Total stock-based compensation expense $ 19,288 $ 9,695 $ 3,909
Schedule of Valuation Assumptions Used to Calculate Fair Value of Employee Stock Options	The following table illustrates the assumptions for the Black-Scholes option-pricing model used in determining the fair value of options granted to employees: Year Ended December 31, 2015 2014 2013 Expected volatility 82-92 % 87-109 % 95-110 % Expected dividends 0 % 0 % 0 % Expected term (in years) 5-6 6 6 Risk-free rate 1.3-1.9 % 1.6-2.0 % 1.1-1.8 %
Schedule of Valuation Assumptions Used to Calculate Fair Value of Nonemployee Stock Options	The fair value of non-employee stock options was calculated using the Black-Scholes valuation model, based on the following assumptions: Year Ended December 31, 2015 2014 2013 Expected volatility 83-92 % 92 % 91%-122 % Expected dividends 0 % 0 % 0 % Expected term (in years) 6-9 7-9 5-10 Risk-free rate 1.5-2.1 % 1.8-2.0 % 1.3-2.7 %
Summary of Restricted Stock Unit Activity	The following table summarizes RSU activity for the twelve months ended December 31, 2015 (in thousands, except per share amounts): Restricted Stock Units Number of Shares Weighted-Average Grant Date Fair Value Per Share Nonvested at December 31, 2014 123 $ 26.85 Granted 989 22.05 Vested (40) 26.11 Canceled (30) 25.61 Nonvested at December 31, 2015 1,042 $ 22.35

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Reconciliation of Statutory Federal Income Tax Rate To Company Effective Tax Rate	The reconciliation of the statutory federal income tax rate to the Company’s effective tax rate is as follows: Year Ended December 31, 2015 2014 2013 Federal statutory rate 34.0 % 34.0 % 34.0 % State statutory rate 0.8 5.8 5.8 Research and development tax credit 2.0 2.3 1.7 Permanent item (2.0 ) (1.0 ) (1.0 ) Valuation allowance (34.8 ) (41.1 ) (40.5 ) Provision for income taxes — % — % — %
Tax Effects of Temporary Differences and Carry Forwards	The tax effects of temporary differences and carryforwards that give rise to significant portions of the deferred tax assets are as follows (in thousands): December 31, 2015 2014 2013 Federal and state net operating loss carryforwards $ 133,631 $ 91,604 $ 64,768 Federal and state research and development credits 8,210 6,253 4,703 Depreciation 2,825 3,036 1,538 Intangible assets — — (6 ) Accruals and reserves 19,162 7,900 4,942 163,828 108,793 75,945 Valuation allowance (163,828 ) (108,793 ) (75,945 ) Net deferred tax assets $ — $ — $ —
Schedule of Unrecognized Tax Benefits	The Company recognizes uncertain tax positions when it is more-likely-than-not, based on the technical merits, that the position will not be sustained upon examination. A reconciliation of the beginning and ending amounts of unrecognized tax benefits is as follows (in thousands): 2015 2014 2013 Balance at January 1 $ 3,189 $ 2,476 $ 1,836 Increases related to current period tax positions 1,198 713 588 Increases related to prior period tax positions 5,478 — 52 Balance as of December 31 $ 9,865 $ 3,189 $ 2,476

Selected Quarterly Financial 38

Selected Quarterly Financial Data (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Information	The following table contains quarterly financial information for 2015 and 2014. The Company believes that the following information reflects all normal recurring adjustments necessary for a fair statement of the information for the periods presented. The operating results for any quarter are not necessarily indicative of results for any future period. December 31, September 30, June 30, March 31, December 31, September 30, June 30, March 31, 2015 2015 2015 2015 2014 2014 2014 2014 (In thousands, except share and per share data) Revenues: License and collaboration $ 11,960 $ 6,590 $ — $ — $ — $ — $ — $ — Operating expenses: Research and 26,500 32,391 18,627 15,780 16,596 11,647 11,075 10,909 Selling, general and 44,056 25,255 20,340 13,487 10,486 7,311 5,322 4,795 Total operating 70,556 57,646 38,967 29,267 27,082 18,958 16,397 15,704 Loss from operations (58,596) (51,056) (38,967) (29,267) (27,082) (18,958) (16,397) (15,704) Interest and other income 613 30 188 84 69 17 36 27 Interest expense (343) (442) (478) (482) (635) (494) (376) (391) Net loss (58,326) (51,468) (39,257) (29,665) (27,648) (19,435) (16,737) (16,068) Net loss per share basic and $ (1.40) $ (1.24) $ (0.95) $ (0.78) $ (0.80) $ (0.57) $ (0.51) $ (0.54) Weighted-average common 41,785,176 41,633,410 41,490,003 37,829,239 34,368,776 34,064,780 33,141,384 29,710,415

Organization - Additional Infor

Organization - Additional Information (Details)	12 Months Ended
	Dec. 31, 2015Segment
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Commencement date of operations	Oct. 29, 2007
Number of business segments	1

Summary of Significant Accoun40

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)

1 Months Ended

3 Months Ended

12 Months Ended

Aug. 31, 2015

Dec. 31, 2015

Sep. 30, 2015

Jun. 30, 2015

Mar. 31, 2015

Dec. 31, 2014

Sep. 30, 2014

Jun. 30, 2014

Mar. 31, 2014

Dec. 31, 2015

Dec. 31, 2014

Dec. 31, 2013

Oct. 31, 2013

Significant Accounting Policies [Line Items]

Accumulated deficit

$ (484,444,000)

$ (305,728,000)

$ (484,444,000)

$ (305,728,000)

Net loss

$ 58,326,000

$ 51,468,000

$ 39,257,000

$ 29,665,000

$ 27,648,000

$ 19,435,000

$ 16,737,000

$ 16,068,000

$ 178,716,000

$ 79,888,000

$ 73,845,000

Convertible preferred stock converted into common stock

18,924,883

18,924,883

472,187

Employee Stock Purchase Plan

Significant Accounting Policies [Line Items]

Purchase price per share on fair market value on purchase date

85.00%

Maximum

Significant Accounting Policies [Line Items]

Estimated useful life of plant and equipment

7 years

Maximum | Employee Stock Purchase Plan

Significant Accounting Policies [Line Items]

Purchase price per share of fair market value on first day of offering period

85.00%

Minimum

Significant Accounting Policies [Line Items]

Estimated useful life of plant and equipment

3 years

Credit Concentration Risk | Investments Other Than Government Obligation | Maximum

Significant Accounting Policies [Line Items]

Concentration Risk, Percentage

5.00%

VFMCRP [Member]

Significant Accounting Policies [Line Items]

Upfront cash payment receivable

$ 40,000,000

Veltassa Product Sales

Significant Accounting Policies [Line Items]

Trade accounts receivable

$ 500,000

$ 500,000

Allowance for doubtful accounts receivable

0

0

Deferred revenue

$ 500,000

$ 500,000

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Schedule of Shares Excluded from Computations of Diluted Net Loss per Common Share (Details) - shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock equivalents excluded from computations of diluted net loss per common share	6,008	3,993	3,614
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	64
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	4,951	3,813	3,545
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	1,042	123
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	5

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value of Financial Instruments Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Financial assets:
Total financial assets	$ 239,244	$ 127,973
Liabilities:
Total financial liabilities	93	233
Contingent Put Option Liability
Liabilities:
Total financial liabilities	93	233
Corporate Bonds
Financial assets:
Total financial assets	46,650	71,763
Agency Bonds
Financial assets:
Total financial assets	124,434	15,162
U.S. Government Bonds
Financial assets:
Total financial assets	7,667
Level 1
Financial assets:
Total financial assets	37,205	10,202
Level 2
Financial assets:
Total financial assets	202,039	117,771
Level 2 | Corporate Bonds
Financial assets:
Total financial assets	46,650	71,763
Level 2 | Agency Bonds
Financial assets:
Total financial assets	124,434	15,162
Level 2 | U.S. Government Bonds
Financial assets:
Total financial assets	7,667
Level 3
Liabilities:
Total financial liabilities	93	233
Level 3 | Contingent Put Option Liability
Liabilities:
Total financial liabilities	93	233
Money Market Funds
Financial assets:
Total financial assets	37,205	10,202
Money Market Funds | Level 1
Financial assets:
Total financial assets	37,205	10,202
Commercial Paper
Financial assets:
Total financial assets	23,288	30,846
Commercial Paper | Level 2
Financial assets:
Total financial assets	$ 23,288	$ 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) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Beginning Balance	$ 233
Increase (Decrease) in fair value included in other income (expense)	(140)	$ 123
Ending Balance	$ 93	233
Contingent Put Option Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value measurement with unobservable inputs reconciliation, issuances of instruments		$ 110

Cash, Cash Equivalents, and S44

Cash, Cash Equivalents, and Short-Term Investments - Summary of Cash, Cash Equivalents, and Short-Term Investments (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cash And Cash Equivalents [Line Items]
Amortized Cost	$ 240,772	$ 135,778
Gross Unrealized Gains	23	15
Gross Unrealized Losses	(79)	(36)
Estimated Fair Value	240,716	135,757
Cash and cash equivalents	63,723	30,264	$ 94,759	$ 15,221
Short-term investments	176,993	105,493
Total financial assets	240,716	135,757
Cash and Money Market Funds
Cash And Cash Equivalents [Line Items]
Amortized Cost	38,677	17,986
Estimated Fair Value	38,677	17,986
Commercial Paper
Cash And Cash Equivalents [Line Items]
Amortized Cost	23,277	30,835
Gross Unrealized Gains	11	11
Estimated Fair Value	23,288	30,846
Corporate Bonds
Cash And Cash Equivalents [Line Items]
Amortized Cost	46,677	71,794
Gross Unrealized Gains		2
Gross Unrealized Losses	(27)	(33)
Estimated Fair Value	46,650	71,763
Agency Bonds
Cash And Cash Equivalents [Line Items]
Amortized Cost	124,466	15,163
Gross Unrealized Gains	12	2
Gross Unrealized Losses	(44)	(3)
Estimated Fair Value	124,434	$ 15,162
U.S. Government Bonds
Cash And Cash Equivalents [Line Items]
Amortized Cost	7,675
Gross Unrealized Losses	(8)
Estimated Fair Value	$ 7,667

Cash, Cash Equivalents, and S45

Cash, Cash Equivalents, and Short-Term Investments - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 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

Inventory - Schedule of Invento

Inventory - Schedule of Inventories (Details) $ in Thousands	Dec. 31, 2015USD ($)
Inventory Net [Abstract]
Raw materials	$ 4,761
Work in process	3,943
Finished goods	147
Total inventory	$ 8,851

Property and Equipment - Summar

Property and Equipment - Summary of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 13,434	$ 10,630
Less accumulated depreciation and amortization	(3,807)	(7,163)
Property and equipment, net	9,627	3,467
Machinery and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	3,715	2,829
Computers and Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,300	657
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	2,129	6,135
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 3,290	$ 1,009

Property and Equipment - Additi

Property and Equipment - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Property Plant And Equipment [Abstract]
Depreciation and amortization	$ 2,772	$ 4,766	$ 1,088

Accrued Liabilities - Schedule

Accrued Liabilities - Schedule of Accrued Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accrued contract manufacturing	$ 26,371	$ 6,655
Accrued accounts payable	10,717	898
Accrued professional and consulting services	355	184
Accrued clinical trial expenses	201	41
Accrued interest	93
Total accrued liabilities	$ 37,737	$ 7,778

Borrowings - Additional Informa

Borrowings - Additional Information (Details)	May. 30, 2014USD ($)$ / sharesshares	Jul. 31, 2008USD ($)Payment$ / sharesshares	Jun. 30, 2013USD ($)	Dec. 31, 2015USD ($)Payment	Dec. 31, 2014USD ($)shares	Dec. 31, 2013USD ($)shares	Oct. 31, 2013$ / shares	May. 31, 2013USD ($)$ / sharesshares	Jan. 31, 2013$ / sharesshares	Dec. 31, 2012$ / sharesshares
Debt Instrument [Line Items]
Line of credit amount		$ 1,500,000						$ 1,600,000
Line of credit, interest rate		8.00%		5.75%
Exercise price of warrants | $ / shares							$ 15.308
Line of credit, terms of repayment				36 equal monthly installments
Line of credit, remaining and expired amount			$ 300,000
Line of credit, expiry date				Jun. 30, 2013
Line of credit principal amount outstanding				$ 200,000
Proceeds from issuance of long term debt					$ 3,549,000	$ 12,404,000
Common Stock
Debt Instrument [Line Items]
Conversion of preferred stock to common stock, shares | shares						18,925,000
Capital Loan
Debt Instrument [Line Items]
Number of debt repayments | Payment				30
Exercise price of warrants | $ / shares	$ 23.69
Fair value of warrants				$ 200,000
Final payment as a percentage of amounts borrowed				8.50%
Proceeds from issuance of long term debt	$ 15,000,000			$ 15,000,000
Repayment of outstanding debt				11,000,000
Final payment fee				$ 400,000
Loan agreement amendment date				Dec. 17, 2015
Debt instrument, payment terms				Payments on the $15.0 million loan will be interest only through January 2017, followed by 30 months of equal monthly payments of interest and principal.
Warrants exercised | shares					13,609
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%
Estimated fair value of contingent put option liability				$ 100,000
Principal amount outstanding on loan				$ 15,000,000
Capital Loan | Common Stock
Debt Instrument [Line Items]
Conversion of preferred stock to common stock, shares | shares	12,661				7,808
Capital Loan | Initial advance
Debt Instrument [Line Items]
Debt instrument, interest rate				7.40%
Capital Loan | Three Month LIBOR Rate | Second Tranche
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				7.17%
Series C-1 Convertible Preferred Stock
Debt Instrument [Line Items]
Warrants issued to purchase preferred stock | shares										2,076,643
Exercise price of warrants | $ / shares										$ 0.17
Series C-1 Convertible Preferred Stock | Capital Loan
Debt Instrument [Line Items]
Warrants issued to purchase preferred stock | shares									54,437
Exercise price of warrants | $ / shares									$ 9.1848
Line of Credit
Debt Instrument [Line Items]
Number of debt repayments | Payment				36
Final payment as a percentage of amounts borrowed				9.25%
Line of credit, utilized amount			$ 1,300,000
Line of Credit | Series A-1 Convertible Preferred Stock
Debt Instrument [Line Items]
Warrants issued to purchase preferred stock | shares		2,616
Exercise price of warrants | $ / shares		$ 17.20
Warrants expiration term		10 years
Fair value of warrants		$ 17,000
Line of Credit | Series C-1 Convertible Preferred Stock
Debt Instrument [Line Items]
Warrants issued to purchase preferred stock | shares								6,968
Exercise price of warrants | $ / shares								$ 9.1848
Minimum
Debt Instrument [Line Items]
Number of debt repayments | Payment		36
Minimum | Capital Loan
Debt Instrument [Line Items]
Prepayment charges of outstanding loan				1.00%
Maximum
Debt Instrument [Line Items]
Number of debt repayments | Payment		42
Maximum | Capital Loan
Debt Instrument [Line Items]
Prepayment charges of outstanding loan				3.00%

Collaboration and License Agr51

Collaboration and License Agreement - Additional Information (Details) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2015	Dec. 31, 2015
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue recognized		$ 18,600,000
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 Contingencies -

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Commitments And Contingencies [Line Items]
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
Lease commencement date	Feb. 1, 2015
Operating lease, term of contract	10 years
Operating lease, renewal term	5 years
Net value of the leasehold improvements and other assets		$ 1,500
Deferred rent liability	$ 27	1,156
Additional lease allowance	2,200
One-time lease improvement allowance	600
Amount used in additional lease allowance	800
Rent expense	$ 2,200		$ 1,100
Rent expense attributable to amortization of deferred rent liability		$ (2,100)
Indemnification agreements	In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future, but have not yet been made. To date, the Company has not paid any claims or been required to defend any action related to its indemnification obligations. However, the Company may record charges in the future as a result of these indemnification obligations. The Company also has indemnification obligations to its officers and directors for specified events or occurrences, subject to some limits, while they are serving at the Company’s request in such capacities. There have been no claims to date and the Company has director and officer insurance that may enable the Company to recover a portion of any amounts paid for future potential claims. The Company believes the fair value of these indemnification agreements is minimal. Accordingly, the Company has not recorded any liabilities for these agreements as of December 31, 2015.
Irrevocable Letter of Credit
Commitments And Contingencies [Line Items]
Security deposit	$ 700
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.

Commitments and Contingencies53

Commitments and Contingencies - Schedule of Future Minimum Payments Under Supply Agreement(Details) - DPx Fine Chemicals, Lanxess and Patheon $ in Thousands	Dec. 31, 2015USD ($)
Long Term Purchase Commitment [Line Items]
2,016	$ 43,495
2,017	68,006
2,018	71,922
2,019	59,304
Total future minimum payments	$ 242,727

Commitments and Contingencies54

Commitments and Contingencies - Schedule of Future Minimum Payments Under Operating Lease (Details) $ in Thousands	Dec. 31, 2015USD ($)
Commitments And Contingencies Disclosure [Abstract]
2,016	$ 3,761
2,017	3,941
2,018	4,034
2,019	4,147
2,020	4,271
Thereafter	18,808
Total future minimum payments	$ 38,962

Technology Agreement - Addition

Technology Agreement - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended
	Mar. 31, 2013	Feb. 28, 2013
Finite Lived Intangible Assets [Line Items]
Research and development expense	$ 12.5	$ 12.5
Acquisition expenses		$ 30
Minimum
Finite Lived Intangible Assets [Line Items]
Transaction cost, additional payment percentage on purchase price		6.70%
Maximum
Finite Lived Intangible Assets [Line Items]
Transaction cost, additional payment percentage on purchase price		10.00%

Convertible Preferred Stock a56

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Additional Information (Details) - USD ($)	Mar. 03, 2015	Oct. 31, 2013	Feb. 29, 2016	Feb. 28, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 04, 2015	Dec. 15, 2014	Nov. 30, 2013
Convertible Preferred Stock And Stockholders Equity [Line Items]
Net proceeds from issuance of convertible preferred stock							$ 14,983,000
Exercise price of warrants		$ 15.308
Increase to stockholders' equity (deficit)		$ 7,300,000
Convertible preferred stock converted into common stock		472,187			18,924,883
Preferred stock, shares outstanding					0	0	0
Net proceeds from public offerings	$ 161,900,000				$ 213,711,000	$ 110,668,000	$ 77,964,000
Gross proceeds from issuance of common stock	$ 172,700,000
Unvested common stock, shares					282	1,276	5,125
Unvested common stock, value					$ 1,000	$ 6,000	$ 23,000
Initial Public Offering
Convertible Preferred Stock And Stockholders Equity [Line Items]
Convertible preferred stock converted into common stock											18,924,883
At The Market Offering Program
Convertible Preferred Stock And Stockholders Equity [Line Items]
Issuance of common stock, shares				1,549,910	0	514,710
Shares issued, price per share				$ 34.48		$ 32.17
Aggregate offering price						$ 16,600,000
Net proceeds from public offerings				$ 51,800,000		$ 16,100,000
Gross proceeds from issuance of common stock				$ 53,400,000
At The Market Offering Program | Subsequent Event
Convertible Preferred Stock And Stockholders Equity [Line Items]
Issuance of common stock, shares			2,509,372
Shares issued, price per share			$ 18.18
Net proceeds from public offerings			$ 44,200,000
Gross proceeds from issuance of common stock			$ 45,600,000
Minimum
Convertible Preferred Stock And Stockholders Equity [Line Items]
Purchase price per share					$ 3.96
Maximum
Convertible Preferred Stock And Stockholders Equity [Line Items]
Purchase price per share					$ 7.40
Maximum | Shelf Registration
Convertible Preferred Stock And Stockholders Equity [Line Items]
Aggregate offering price									$ 300,000,000	$ 250,000,000
Common Stock
Convertible Preferred Stock And Stockholders Equity [Line Items]
Issuance of common stock, shares	4,485,000				4,485,000	4,131,000	7,878,000
Shares issued, price per share	$ 38.50
Common Stock | Shelf Registration
Convertible Preferred Stock And Stockholders Equity [Line Items]
Issuance of common stock, shares					1,550,000	515,000
Common Stock | Minimum
Convertible Preferred Stock And Stockholders Equity [Line Items]
Preferred stock holders, ownership percentage						55.00%
Common Stock | Maximum | Shelf Registration
Convertible Preferred Stock And Stockholders Equity [Line Items]
Aggregate offering price									$ 75,000,000	$ 70,000,000
Series C-1 Convertible Preferred Stock
Convertible Preferred Stock And Stockholders Equity [Line Items]
Issuance of common stock, shares								7,076,901
Shares issued, price per share								$ 9.1848
Net proceeds from issuance of convertible preferred stock								$ 65,000,000
Number of securities issued on purchase of excess than pro-rata shares								2
Warrants issued to purchase preferred stock								2,076,643
Exercise price of warrants								$ 0.17
Warrant exercisable contractual life								5 years
Series C-1 Convertible Preferred Stock | Minimum
Convertible Preferred Stock And Stockholders Equity [Line Items]
Preferred stock holders, ownership percentage						50.00%
Series C-2 Convertible Preferred Stock
Convertible Preferred Stock And Stockholders Equity [Line Items]
Issuance of common stock, shares		1,633,126
Shares issued, price per share		$ 9.1848
Net proceeds from issuance of convertible preferred stock		$ 15,000,000
Number of securities issued on purchase of excess than pro-rata shares		2
Warrants issued to purchase preferred stock		479,221
Exercise price of warrants		$ 0.17
Warrant exercisable contractual life		5 years

Convertible Preferred Stock a57

Convertible Preferred Stock and Stockholders' Equity (Deficit) - Summary Of Unvested Common Stock (Details) - $ / shares shares in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Stockholders Equity Note [Abstract]
Number of shares, Unvested at beginning	1	5	7
Number of shares, Shares sold			23
Number of shares, Shares vested	(1)	(3)	(25)
Number of shares, Shares repurchased		(1)
Number of shares, Unvested at ending		1	5
Weighted Average Purchase Price, Unvested shares, Beginning balance	$ 4.49	$ 3.78	$ 4.13
Weighted Average Purchase Price, Shares sold			4.12
Weighted Average Purchase Price, Shares vested	$ 4.21	4.49	4.01
Weighted Average Purchase Price, Shares repurchased		5.27
Weighted Average Purchase Price, Unvested shares, Ending balance		$ 4.49	$ 3.78

Equity Compensation Plans and58

Equity Compensation Plans and Stock Based Compensation - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended
	Nov. 30, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Jun. 30, 2014	Dec. 31, 2012
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average grant-date fair value of options grant		$ 19.78	$ 19.77	$ 6.23
Total fair value of options vested		$ 13,200	$ 9,100	$ 5,000
Intrinsic value of options exercised		20,800	$ 14,900	$ 200
Unrecognized compensation cost		$ 51,300
Expected period of compensation expense recognized		3 years
Shares Subject to Outstanding Options, Options granted				23,000
Common stock options, exercise price				$ 7.40
Restricted Stock Units
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Performance based awards	186,268
Unrecognized compensation cost		$ 21,300
Expected period of compensation expense recognized		2 years 9 months 18 days
Non Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Subject to Outstanding Options, Options granted		0	0	290
ESPP
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		563,134
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		447,642
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		2,000,000
Share issued or transferred under the Plan		1,757,533
2007 Plan, 2013 Plan and Inducement Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance		3,402,000	1,000,000	2,571,000
Performance based awards	220,000
Shares Subject to Outstanding Options, Options granted		2,262,000	1,004,000	1,444,000
Common stock options, exercise price		$ 19.09	$ 11.05	$ 5.63		$ 4.13

Equity Compensation Plans and59

Equity Compensation Plans and Stock Based Compensation - Summary of Option Activity Under 2007 Plan 2013 Plan and Inducement Plan and Related Information (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Options granted			(23)
Shares Available for Grant, Restricted stock units granted	(989)
Shares Available for Grant, Restricted stock units cancelled	30
Shares Subject to Outstanding Options, Options granted			23
Weighted-Average Exercise Price Per Share, Options outstanding, beginning balance		$ 7.40
Weighted-Average Exercise Price Per Share, Options outstanding, ending balance			$ 7.40
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	1,233	67
Shares Available for Grant, Additional shares reserved	3,402	1,000	2,571
Shares Available for Grant, Options granted	(2,262)	(1,004)	(1,444)
Shares Available for Grant, Restricted stock units granted	(989)	(130)
Shares Available for Grant, Options forfeited	343	61	39
Shares Available for Grant, Restricted stock units cancelled	30	7
Shares Available for Grant, Options outstanding, ending balance	1,691	1,167	1,233
Shares Subject to Outstanding Options, Options outstanding, beginning balance	3,813	3,545	2,163
Shares Subject to Outstanding Options, Options granted	2,262	1,004	1,444
Shares Subject to Outstanding Options, Options exercised	(781)	(675)	(23)
Shares subject to Outstanding Options, Options forfeited	(343)	(61)	(39)
Shares Subject to Outstanding Options, Options outstanding, ending balance	4,951	3,813	3,545
Shares Subject to Outstanding Options, Vested and expected to vest	4,719
Shares Subject to Outstanding Options, Vested	1,676
Weighted-Average Exercise Price Per Share, Options outstanding, beginning balance	$ 11.05	$ 5.63	$ 4.13
Weighted-Average Exercise Price Per Share, Options granted	27.92	25.63	7.91
Weighted-Average Exercise Price Per Share, Restricted stock units granted	22.05
Weighted-Average Exercise Price Per Share, Options exercised	5.06	4.31	4.12
Weighted-Average Exercise Price Per Share, Options forfeited	19.88	10.95	4.12
Weighted-Average Exercise Price Per Share, Restricted stock units cancelled	25.61
Weighted-Average Exercise Price Per Share, Options outstanding, ending balance	19.09	$ 11.05	$ 5.63
Weighted-Average Exercise Price Per Share, Vested and expected to vest	18.78
Weighted-Average Exercise Price Per Share, Vested	$ 10.07
Weighted-Average Remaining Contractual Term, Options outstanding	8 years 2 months 12 days
Weighted-Average Remaining Contractual Term, Vested and expected to vest	8 years 2 months 12 days
Weighted-Average Remaining Contractual Term, Vested	6 years 8 months 12 days
Aggregate Intrinsic Value, Options Outstanding	$ 50,248
Aggregate Intrinsic Value, Vested and expected to vest	49,297
Aggregate intrinsic value, Vested	$ 31,023

Equity Compensation Plans and60

Equity Compensation Plans and Stock Based Compensation - Schedule of Stock-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 19,288	$ 9,695	$ 3,909
Research and Development | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	5,168	1,657	776
Research and Development | Non-employee Consultants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	3,325	4,045	1,659
Selling, General and Administrative | Employees
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation	$ 10,795	3,980	$ 1,474
Selling, General and Administrative | Non-employee Consultants
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation		$ 13

Equity Compensation Plans and61

Equity Compensation Plans and Stock Based Compensation - Schedule of Valuation Assumptions Used to Calculate Fair Value of Employee Stock Options (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility, minimum	82.00%	87.00%	95.00%
Expected dividends	0.00%	0.00%	0.00%
Expected term (in years)		6 years	6 years
Risk-free rate, minimum	1.30%	1.60%	1.10%
Expected volatility, maximum	92.00%	109.00%	110.00%
Risk-free rate, maximum	1.90%	2.00%	1.80%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	5 years
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected term (in years)	6 years

Equity Compensation Plans and62

Equity Compensation Plans and Stock Based Compensation - Schedule of Valuation Assumptions Used to Calculate Fair Value of Nonemployee Stock Options (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility		92.00%
Expected dividends	0.00%	0.00%	0.00%
Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	83.00%		91.00%
Expected term (in years)	6 years	7 years	5 years
Risk-free rate	1.50%	1.80%	1.30%
Maximum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expected volatility	92.00%		122.00%
Expected term (in years)	9 years	9 years	10 years
Risk-free rate	2.10%	2.00%	2.70%

Equity Compensation Plans and63

Equity Compensation Plans and Stock Based Compensation - Summary of Restricted Stock Unit Activity (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2015$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Nonvested at Beginning | shares	123
Number of Shares, Granted | shares	989
Number of Shares, Vested | shares	(40)
Number of Shares, Canceled | shares	(30)
Number of Shares, Nonvested at Ending | shares	1,042
Weighted Average Grant Date Fair Value Per Share, Nonvested at Beginning | $ / shares	$ 26.85
Weighted Average Grant Date Fair Value Per Share, Granted | $ / shares	22.05
Weighted Average Grant Date Fair Value Per Share, Vested | $ / shares	26.11
Weighted Average Grant Date Fair Value Per Share, Canceled | $ / shares	25.61
Weighted Average Grant Date Fair Value Per Share, Nonvested at Ending | $ / shares	$ 22.35

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Statutory Federal Income Tax Rate To Company Effective Tax Rate (Details)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal statutory rate	34.00%	34.00%	34.00%
State statutory rate	0.80%	5.80%	5.80%
Research and development tax credit	2.00%	2.30%	1.70%
Permanent item	(2.00%)	(1.00%)	(1.00%)
Valuation allowance	(34.80%)	(41.10%)	(40.50%)
Provision for income taxes	0.00%	0.00%	0.00%

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Line Items]
Deferred Tax Assets, Gross	$ 163,828,000	$ 108,793,000	$ 75,945,000
Tax benefit	0	0	0
Valuation allowance	55,000,000	32,800,000	$ 27,900,000
Excess stock option deductions	24,700,000
Deferred income tax asset for net operating loss		$ 28,600,000
Research and development expense carry forwards	7,100,000
Future tax expenses	6,800,000
Federal Income Tax [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 387,600,000
Operating loss expiration year	2,027
California State Income Tax [Member]
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 252,400,000
Operating loss expiration year	2,017

Income Taxes - Tax Effects of T

Income Taxes - Tax Effects of Temporary Differences and Carry Forwards (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Federal and state net operating loss carryforwards	$ 133,631	$ 91,604	$ 64,768
Federal and state research and development credits	8,210	6,253	4,703
Depreciation	2,825	3,036	1,538
Intangible assets			(6)
Accruals and reserves	19,162	7,900	4,942
Deferred Tax Assets, Gross	163,828	108,793	75,945
Valuation allowance	(163,828)	(108,793)	(75,945)
Net deferred tax assets	$ 0	$ 0	$ 0

Income Taxes - Schedule of Unre

Income Taxes - Schedule of Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Beginning balance	$ 3,189	$ 2,476	$ 1,836
Increases related to current period tax positions	1,198	713	588
Increases related to prior period tax positions	5,478		52
Ending balance	$ 9,865	$ 3,189	$ 2,476

401(k) Savings Plan - Additiona

401(k) Savings Plan - Additional Information (Details) - 401(k) Savings Plan - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Contribution Plan Disclosure [Line Items]
Employee minimum percent contribution for their annual compensation	1.00%
Employee maximum percent contribution for their annual compensation	90.00%
Matching contributions by Company	$ 0	$ 0	$ 0

Related Party Transaction - Add

Related Party Transaction - Additional Information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2015USD ($)
Related Party Transactions [Abstract]
Payments from related party due to disgorgement of short-swing profit recognized increase to additional paid-in capital	$ 7,350

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands	Mar. 03, 2015	Feb. 29, 2016	Feb. 28, 2015	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Subsequent Event [Line Items]
Gross proceeds from issuance of common stock	$ 172,700
Net proceeds from public offerings	$ 161,900			$ 213,711	$ 110,668	$ 77,964
At The Market Offering Program
Subsequent Event [Line Items]
Shares issued, price per share			$ 34.48		$ 32.17
Gross proceeds from issuance of common stock			$ 53,400
Net proceeds from public offerings			$ 51,800		$ 16,100
Subsequent Event | At The Market Offering Program
Subsequent Event [Line Items]
Issuance of common stock, shares		2,509,372
Shares issued, price per share		$ 18.18
Gross proceeds from issuance of common stock		$ 45,600
Net proceeds from public offerings		$ 44,200

Selected Quarterly Financial 71

Selected Quarterly Financial Data (unaudited) - Summary of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
License and collaboration revenue	$ 11,960	$ 6,590							$ 18,550
Operating expenses:
Research and development	26,500	32,391	$ 18,627	$ 15,780	$ 16,596	$ 11,647	$ 11,075	$ 10,909	93,298	$ 50,227	$ 58,971
Selling, general and administrative	44,056	25,255	20,340	13,487	10,486	7,311	5,322	4,795	103,138	27,914	11,940
Total operating expenses	70,556	57,646	38,967	29,267	27,082	18,958	16,397	15,704	196,436	78,141	70,911
Loss from operations	(58,596)	(51,056)	(38,967)	(29,267)	(27,082)	(18,958)	(16,397)	(15,704)	(177,886)	(78,141)	(70,911)
Interest and other income (expense), net	613	30	188	84	69	17	36	27	915	149	(1,481)
Interest expense	(343)	(442)	(478)	(482)	(635)	(494)	(376)	(391)	(1,745)	(1,896)	(1,453)
Net loss	$ (58,326)	$ (51,468)	$ (39,257)	$ (29,665)	$ (27,648)	$ (19,435)	$ (16,737)	$ (16,068)	$ (178,716)	$ (79,888)	$ (73,845)
Net loss per share basic and diluted	$ (1.40)	$ (1.24)	$ (0.95)	$ (0.78)	$ (0.80)	$ (0.57)	$ (0.51)	$ (0.54)	$ (4.39)	$ (2.43)	$ (22.42)
Weighted-average common shares used to compute net loss per share, basic and diluted	41,785,176	41,633,410	41,490,003	37,829,239	34,368,776	34,064,780	33,141,384	29,710,415	40,697,896	32,837,508	3,620,235