Fate Therapeutics (FATE) 10-K 16 Mar 17 2016 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2016	Mar. 13, 2017	Jun. 30, 2016
Document And Entity Information [Abstract]
Entity Registrant Name	FATE THERAPEUTICS INC
Entity Central Index Key	1,434,316
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Smaller Reporting Company
Trading Symbol	FATE
Entity Public Float			$ 43,692,948
Entity Common Stock, Shares Outstanding		41,386,506
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 88,609	$ 64,809
Short-term investments	3,503
Prepaid expenses and other current assets	1,211	843
Total current assets	93,323	65,652
Property and equipment, net	1,579	2,160
Restricted cash	122	122
Other assets	24	24
Total assets	95,048	67,958
Current liabilities:
Accounts payable	934	996
Accrued expenses	3,957	2,439
Current portion of deferred rent	4	54
Current portion of deferred revenue	2,105	2,401
Repurchase liability for unvested equity awards		1
Long–term debt, current portion	8,187	7,550
Total current liabilities	15,187	13,441
Deferred rent	101	58
Deferred revenue	2,829	4,934
Accrued expenses	1,276	799
Long–term debt, net of current portion	2,501	10,688
Commitments and contingencies (Note 5)
Stockholders’ Equity:
Preferred stock, $0.001 par value; authorized shares—5,000,000 at December 31, 2016 and December 31, 2015; 2,819,549 Class A convertible preferred shares issued and outstanding at December 31, 2016; no shares issued or outstanding at December 31, 2015	3
Common stock, $0.001 par value; authorized shares—150,000,000 at December 31, 2016 and December 31, 2015; issued and outstanding—41,386,506 at December 31, 2016 and 28,716,570 at December 31, 2015	41	29
Additional paid–in capital	248,957	180,393
Accumulated other comprehensive loss	(1)
Accumulated deficit	(175,846)	(142,384)
Total stockholders’ equity	73,154	38,038
Total liabilities and stockholders’ equity	$ 95,048	$ 67,958

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, authorized shares	150,000,000	150,000,000
Common stock issued	41,386,506	28,716,570
Common stock, outstanding shares	41,386,506	28,716,570
Class A Convertible Preferred Shares
Preferred stock, issued shares	2,819,549	0
Preferred stock, outstanding shares	2,819,549	0

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Collaboration revenue	$ 4,402	$ 2,431
Operating expenses:
Research and development	26,452	19,861	$ 16,435
General and administrative	9,913	10,352	8,469
Total operating expenses	36,365	30,213	24,904
Loss from operations	(31,963)	(27,782)	(24,904)
Other income (expense):
Interest income	138	10	2
Interest expense	(1,637)	(2,220)	(549)
Loss on extinguishment of debt			(432)
Total other expense, net	(1,499)	(2,210)	(979)
Net loss	(33,462)	(29,992)	(25,883)
Other comprehensive loss:
Unrealized loss on available-for-sale securities, net	(1)
Comprehensive loss	$ (33,463)	$ (29,992)	$ (25,883)
Net loss per common share, basic and diluted	$ (1.05)	$ (1.18)	$ (1.27)
Weighted-average common shares used to compute basic and diluted net loss per share	31,754,140	25,484,262	20,451,840

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid In Capital	Accumulated Other Comprehensive Loss	Accumulated Deficit	Convertible Preferred Stock
Balance at Dec. 31, 2013	$ 50,848	$ 20	$ 137,337		$ (86,509)
Balance (in shares) at Dec. 31, 2013		20,434,080
Exercise of stock options, net of issuance costs	142	$ 1	141
Exercise of stock options, net of issuance costs (in shares)		96,856
Repurchase liability for unvested equity awards	49		49
Stock–based compensation	2,434		2,434
Issuance of warrants for common stock	375		375
Issuance of stock on achievement of milestone	375		375
Issuance of stock on achievement of milestone (in shares)		38,463
Net loss	(25,883)				(25,883)
Balance at Dec. 31, 2014	28,340	$ 21	140,711		(112,392)
Balance (in shares) at Dec. 31, 2014		20,569,399
Exercise of stock options, net of issuance costs	420		420
Exercise of stock options, net of issuance costs (in shares)		227,215
Repurchase liability for unvested equity awards	44		44
Stock–based compensation	2,400		2,400
Senior executive incentive bonuses paid in common stock	97		97
Senior executive incentive bonuses paid in common stock (in Shares)		19,956
Public offering of common stock, net of offering costs	32,149	$ 7	32,142
Public offering of common stock, net of offering costs (in shares)		6,900,000
Issuance of common stock to collaboration partner	4,580	$ 1	4,579
Issuance of common stock to collaboration partner (in Shares)		1,000,000
Net loss	(29,992)				(29,992)
Balance at Dec. 31, 2015	38,038	$ 29	180,393		(142,384)
Balance (in shares) at Dec. 31, 2015		28,716,570
Exercise of stock options, net of issuance costs	187		187
Exercise of stock options, net of issuance costs (in shares)		136,368
Repurchase liability for unvested equity awards	1		1
Stock–based compensation	$ 3,184		3,184
Issuance of stock on achievement of milestone (in shares)	37,641
Private placement issuances of common stock, net of offering costs	$ 28,797	$ 12	28,785
Private placement issuances of common stock, net of offering costs (in shares)		12,486,837
Private placement issuance of Series A convertible preferred stock, net of offering costs	36,289		36,286			$ 3
Private placement issuance of Series A convertible preferred stock, net of offering costs (in shares)						2,819,549
Senior executive incentive bonuses paid in common stock	121		121
Senior executive incentive bonuses paid in common stock (in Shares)		46,731
Unrealized loss on short-term investments	(1)			$ (1)
Net loss	(33,462)				(33,462)
Balance at Dec. 31, 2016	$ 73,154	$ 41	$ 248,957	$ (1)	$ (175,846)	$ 3
Balance (in shares) at Dec. 31, 2016		41,386,506				2,819,549

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities
Net loss	$ (33,462)	$ (29,992)	$ (25,883)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	881	687	496
Stock–based compensation	3,184	2,400	2,434
Amortization of debt discounts and debt issuance costs	139	176	24
Amortization of premiums and discounts on investments, net	171
Noncash interest expense	492	651	167
Deferred rent	(7)	(24)	(52)
Deferred revenue	(2,401)	7,335
Stock–based milestone charges and change in fair value of exchangeable shares			375
Loss on extinguishment of debt			3
Changes in assets and liabilities:
Prepaid expenses and other assets	(381)	(107)	(146)
Accounts payable and accrued expenses	1,561	477	163
Net cash used in operating activities	(29,823)	(18,397)	(22,419)
Cash flows from investing activities
Proceeds from sale of property and equipment	18
Purchase of property and equipment	(457)	(1,498)	(882)
Purchases of short-term investments	(19,675)
Maturities of short-term investments	16,000
Net cash used in investing activities	(4,114)	(1,498)	(882)
Cash flows from financing activities
Issuance of common stock from equity incentive plans, net of repurchases and issuance costs	186	420	142
Proceeds from public offering of common stock, net of issuance costs		32,149
Proceeds from sale of common stock to collaboration partner		4,580
Proceeds from long–term debt			20,000
Payments on long–term debt	(7,689)	(1,546)	(1,750)
Payments for the issuance of debt			(26)
Net cash provided by financing activities	57,737	35,603	18,366
Net change in cash and cash equivalents	23,800	15,708	(4,935)
Cash and cash equivalents at beginning of the period	64,809	49,101	54,036
Cash and cash equivalents at end of the period	88,609	64,809	49,101
Supplemental disclosure of cash flow information
Interest paid	1,067	$ 1,353	494
Supplemental schedule of noncash investing and financing activities
Issuance of warrants for common stock in connection with long–term debt			$ 375
Common Stock
Cash flows from financing activities
Proceeds from private placement issuances of stock, net of issuance costs	28,849
Preferred Stock
Cash flows from financing activities
Proceeds from private placement issuances of stock, net of issuance costs	$ 36,391

Organization and Summary of Sig

Organization and Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Summary of Significant Accounting Policies	1. Organization and Summary of Significant Accounting Policies Organization Fate Therapeutics, Inc. (the “Company”) was incorporated in the state of Delaware on April 27, 2007 and has its principal operations in San Diego, California. The Company is a clinical-stage biopharmaceutical company dedicated to the development of programmed cellular immunotherapies for cancer and immune disorders. The Company’s hematopoietic cell therapy pipeline is comprised of NK- and T-cell immuno-oncology programs, including off-the-shelf product candidates derived from engineered induced pluripotent cells, and immuno-regulatory programs, including product candidates to prevent life-threatening complications in patients undergoing hematopoietic cell transplantation and to promote immune tolerance in patients with autoimmune disease. Its adoptive cell therapy programs are based on the Company’s novel ex vivo As of December 31, 2016, the Company has devoted substantially all of its efforts to product development, raising capital and building infrastructure and has not generated any revenues from any sales of its therapeutic products. To date, the Company’s revenues have been derived from collaboration agreements and government grants. Follow-on Public Equity Offering In May 2015, the Company completed a public offering of common stock in which the Company sold 6,900,000 shares of its common stock at an offering price of $5.00 per share. Gross proceeds from the offering were $34.5 million. Total underwriting discounts, commissions, and other cash costs related to the offering were $2.4 million. After giving effect to all such costs, total net proceeds from the offering were $32.1 million. Private Placements of Common Stock and Convertible Preferred Stock In August 2016, the Company completed a private placement of common stock in which investors purchased 5,250,000 shares of the Company’s common stock at a price of $1.96 per share. Gross proceeds from the private placement were $10.3 million. After giving effect to costs related to the private placement, net proceeds were $10.2 million. The Company also registered all of the shares issued in the private placement transaction for resale on a Form S-3 filed with the Securities and Exchange Commission (the “SEC”), as required under a registration rights agreement entered into by the Company with the purchasers of the common stock, and the registration statement was declared effective in September 2016. In November 2016, the Company completed a private placement of common and preferred stock in which investors, including investors affiliated with the Company’s directors and officers, purchased convertible preferred stock and common stock of the Company. The Company issued 2,819,549 shares of non-voting Class A Preferred Stock at $13.30 per share, each of which is convertible into five shares of common stock upon certain conditions. The Company also issued 7,236,837 shares of common stock at $2.66 per share. Gross proceeds from the private placement were $56.7 million. After giving effect to costs related to the private placement, net proceeds were $55.0 million. The Company also entered into a registration rights agreement (the “Registration Rights Agreement”) with certain of the purchasers in the November 2016 placement, excluding those purchasers affiliated with the Company’s directors and officers, requiring the Company to register for the resale of the relevant shares. The Company registered all of the relevant shares issued in the placement for resale on a Form S-3 filed with the SEC, as required under the Registration Rights Agreement, and the registration statement was declared effective in January 2017. See Note 6 to the Consolidated Financial Statements for additional information related to this offering. Use of Estimates The Company’s consolidated financial statements are prepared in accordance with United States generally accepted accounting principles (“GAAP”). The preparation of the Company’s consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s consolidated financial statements and accompanying notes. The most significant estimates in the Company’s consolidated financial statements relate to accrued expenses. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions. Principles of Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries, Fate Therapeutics (Canada), Inc. or “Fate Canada”, incorporated in Canada and which was dissolved in November 2016, Fate Therapeutics Ltd., incorporated in the United Kingdom, and Tfinity Therapeutics, Inc., incorporated in the United States. To date, the aggregate operations of these subsidiaries have not been significant and all intercompany transactions and balances have been eliminated in consolidation. Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment. Fair Value of Financial Instruments The carrying amounts of accounts payable and accrued liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. Based on the borrowing rates available to the Company for loans with similar terms, which is considered a Level 2 input as described below, the Company believes that the fair value of long-term debt approximates its carrying value. The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three- tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets; Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. Financial assets measured at fair value on a recurring basis consist of the Company’s cash equivalents and short-term investments. Cash equivalents consisted of money market funds and short-term investments consisted of U.S. treasuries. The following table presents the Company’s assets which were measured at fair value on a recurring basis as of December 31, 2016 and 2015 (in thousands): Fair Value Measurements at Reporting Date Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) As of December 31, 2016: Cash equivalents $ 88,609 $ 88,609 $ — $ — U.S. Treasury debt securities 3,503 3,503 — — Total assets $ 92,112 $ 92,112 $ — $ — As of December 31, 2015: Cash equivalents $ 35,257 $ 35,257 $ — $ — Total assets $ 35,257 $ 35,257 $ — $ — The Company obtains pricing information from its investment manager and generally determines the fair value of investment securities using standard observable inputs, including reported trades, broker/dealer quotes, and bid and/or offers. None of the Company’s non-financial assets or liabilities is recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented. As of December 31, 2016 and 2015, the Company had no material liabilities measured at fair value on a recurring basis. Cash and Cash Equivalents Cash and cash equivalents include cash in readily available checking and savings accounts, money market accounts and money market funds. The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents. Short-Term Investments Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in comprehensive income. The amortized cost of available-for-sale debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income. Concentration of Credit Risk Financial instruments, which potentially subject the Company to significant concentration of credit risk, consist primarily of cash, cash equivalents, and short-term investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits and investments are held. Property and Equipment Property and equipment are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the assets (generally two to five years) and generally consist of furniture and fixtures, computers, and scientific and office equipment. Repairs and maintenance costs are charged to expense as incurred. Impairment of Long-Lived Assets Long-lived assets consist primarily of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. While the Company’s current and historical operating losses and negative cash flows are indicators of impairment, management believes that future cash flows to be received support the carrying value of its long-lived assets and, accordingly, has not recognized any impairment losses since inception. Deferred Rent Deferred rent consists of the difference between cash payments and the recognition of rent expense on a straight-line basis for the facilities the Company occupies. The Company’s leases for its facilities provide for fixed increases in minimum annual rental payments. The total amount of rental payments due over the lease terms are charged to rent expense ratably over the life of the leases. Revenue Recognition The Company recognizes revenues when all four of the following criteria are met: (i) persuasive evidence that an agreement exists; (ii) delivery of the products and/or services has occurred; (iii) the selling price is fixed or determinable; and (iv) collectability is reasonably assured. Revenue arrangements with multiple elements are analyzed to determine whether the elements can be divided into separate units of accounting or whether the elements must be accounted for as a single unit of accounting. The Company divides the elements into separate units of accounting and applies the applicable revenue recognition criteria to each of the elements, if the delivered elements have value to the customer on a stand-alone basis, if the arrangement includes a general right of return relative to the delivered elements, and if the delivery or performance of the undelivered elements is considered probable and substantially within the Company’s control. Revenue has been allocated to each element at the inception of the arrangement using the relative selling price method that is based on a three-tier hierarchy. The relative selling price method requires that the estimated selling price for each element be based on vendor-specific objective evidence (“VSOE”) of fair value, which represents the price charged for each element when it is sold separately or, for an element not yet being sold separately, the price established by management. When VSOE of fair value is not available, third-party evidence (“TPE”) of fair value is acceptable, or a best estimate of selling price is used if neither VSOE nor TPE is available. A best estimate of selling price should be consistent with the objective of determining the price at which the Company would transact if the element were sold regularly on a stand-alone basis and should also take into account market conditions and company-specific factors. Revenue arrangements with multiple elements may include license fees, research and development payments, milestone payments, other contingent payments, and royalties on any product sales derived from collaborations. The Company recognizes nonrefundable license fees with stand-alone value as revenue at the time that the Company has satisfied all performance obligations, and recognizes license fees without stand-alone value as revenue in combination with any undelivered performance obligations. The Company recognizes a research and development payment as revenue over the term of the collaboration agreement as contracted amounts are earned, or reimbursable costs are incurred, under the agreement, where contracted amounts are considered to be earned in relative proportion to the performance required under the applicable agreement. The Company recognizes a milestone payment, which is contingent upon the achievement of a milestone in its entirety, as revenue in the period in which the milestone is achieved only if the milestone meets all criteria to be considered substantive. These criteria include the following: (i) the consideration being earned should be commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from the Company’s performance to achieve the milestone; (ii) the consideration being earned should relate solely to past performance; (iii) the consideration being earned should be reasonable relative to all deliverables and payment terms in the arrangement; and (iv) the milestone should be considered in its entirety and cannot be bifurcated into substantive and nonsubstantive components. Any amounts received pursuant to revenue arrangements with multiple elements prior to satisfying the Company’s revenue recognition criteria are recorded as deferred revenue on the Company’s consolidated balance sheets. Revenue from government grants is recorded when reimbursable expenses are incurred under the grant in accordance with the terms of the grant award. Research and Development Costs All research and development costs are expensed as incurred. Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain. Stock-Based Compensation Stock-based compensation expense represents the cost of the grant date fair value of employee stock option and restricted stock unit grants recognized over the requisite service period of the awards (usually the vesting period) on a straight-line basis, net of estimated forfeitures. For stock option grants for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable or the performance condition has been achieved. For stock option grants for which vesting is subject to both performance-based milestones and market conditions, expense is recorded over the derived service period after the point when the achievement of the performance-based milestone is probable or the performance condition has been achieved. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model, with the exception of option grants for which vesting is subject to both performance-based milestones and market conditions, which are valued using a lattice-based model. The fair value of restricted stock units is based on the closing price of the Company’s common stock as reported on The NASDAQ Global Market on the date of grant. The Company accounts for stock options and restricted stock awards to non-employees using the fair value approach. Stock options and restricted stock awards to non-employees are subject to periodic revaluation over their vesting terms. For stock option grants for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the performance condition is determined to be probable of achievement or when it has been achieved. Convertible Preferred Stock The Company applies the relevant accounting standards to distinguish liabilities from equity when assessing the classification and measurement of preferred stock. Preferred shares subject to mandatory redemptions are considered liabilities and measured at fair value. Conditionally redeemable preferred shares are considered temporary equity. All other preferred shares are considered as stockholders’ equity. The Company applies the relevant accounting standards for derivatives and hedging (in addition to distinguishing liabilities from equity) when accounting for hybrid contracts that contain conversion options. Conversion options must be bifurcated from the host instruments and accounted for as free standing financial instruments according to certain criteria. These criteria include circumstances when (i) the economic characteristics and risks of the embedded derivative instruments are not clearly and closely related to the economic characteristics and risks of the host contract, (ii) the hybrid instrument that embodies both the embedded derivative instrument and the host contract is not re-measured at fair value under otherwise applicable accounting principles with changes in fair value reported in earnings as they occurred, and (iii) a separate instrument with the same terms as the embedded derivative instrument would be considered a derivative instrument. The derivative is subsequently measured at fair value at each reporting date, with the changes in fair value reported in earnings. Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more- likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability. Comprehensive Loss Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. Other comprehensive loss included unrealized losses on available-for-sale securities, which was the only difference between net loss and comprehensive loss for the applicable periods. Net Loss Per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Excluded from the weighted-average number of shares outstanding are shares which have been issued upon the early exercise of stock options and are subject to future vesting and unvested restricted stock totaling 3,284 shares, 44,381 shares, and 76,947 shares for the years ended December 31, 2016, 2015, and 2014, respectively. Diluted net loss per common share is calculated by dividing the net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of convertible preferred stock, warrants for the purchase of common stock, and common stock options and restricted stock units outstanding under the Company’s stock option plans. For all periods presented, there is no difference in the number of common shares used to calculate basic and diluted common shares outstanding due to the Company’s net loss position. Potentially dilutive securities not included in the calculation of diluted net loss per common share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): As of December 31, 2016 2015 2014 Warrants for common stock 134,113 134,113 134,113 Common stock options 3,910,350 2,587,474 2,425,969 Restricted stock units 525,250 525,250 — Series A convertible preferred stock (if converted) 14,097,745 — — 18,667,458 3,246,837 2,560,082 Recent Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update No. 2016-09 (ASU 2016-09). ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal periods beginning after December 15, 2016, with early adoption permitted. The Company believes the ultimate adoption of this guidance will not have a material impact on its Consolidated Financial Statements. In February 2016, the FASB issued ASU 2016-02, which requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases, along with additional qualitative and quantitative disclosures. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the effect this standard will have on its Consolidated Financial Statements. In November 2015, the FASB issued ASU 2015-17, which requires that all deferred tax assets and liabilities be classified as noncurrent on the balance sheet, instead of separating deferred taxes into current and noncurrent amounts. The update is effective for financial statements issued for fiscal years beginning after December 15, 2016. As early adoption of this amendment is permitted, the Company has adopted the update prospectively during the year ended December 31, 2015. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In April 2015, the FASB issued ASU 2015-03, which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The update is effective for financial statements issued for fiscal years beginning after December 15, 2015. As early adoption of this amendment is permitted, the Company has implemented the update accordingly by reclassifying prior period and current period amounts from assets to liabilities. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In August 2014, the FASB issued ASU 2014-15, which defined management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related disclosure. ASU 2014-15 defined the term substantial doubt and requires an assessment for a period of one year after the date of the issuance of the financial statements. It requires certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans and requires an express statement and other disclosures when substantial doubt is not alleviated. The guidance became effective for reporting periods ending after December 15, 2016. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In May 2014, the FASB issued ASU 2014-09, which created a single, principle-based revenue recognition model that will supersede and replace nearly all existing U.S. GAAP revenue recognition guidance. Entities will recognize revenue in a manner that depicts the transfer of goods or services to customers at an amount that reflects the consideration to which the entity expects to be entitled to receive in exchange for those goods or services. The model provides that entities follow five steps: (i) identify the contract with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations, and (v) recognize revenue. For public business entities, ASU 2014-09 is effective beginning in the first quarter of 2018 using one of two prescribed transition methods: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the cumulative catch-up transition method). The Company expects to adopt ASU 2014-09 in the first quarter of 2018 using the full retrospective method to restate each prior reporting period presented. The Company is currently evaluating the effect that the updated standard and transition method will have on its internal processes, financial statements and related disclosures. While the Company continues to assess all potential impacts under ASU 2014-09, recognition of the Company’s revenue under the new standard is expected to be materially consistent with the Company’s current revenue recognition policy. The new standard is not expected to materially impact the timing or amounts of revenue recognized. Going Concern Assessment Pursuant to ASU 2014-15, the Company has assessed its ability to continue as a going concern for a period of one year from the date of the issuance of these financial statements. Substantial doubt about an entity’s ability to continue as a going concern exists when relevant conditions and events, considered in the aggregate, indicate that it is probable that the entity will be unable to meet its obligations as they become due within one year from the financial statement issuance date. The Company determined that there are no conditions or events that raise substantial doubt about its ability to continue as a going concern.

Juno Collaboration and License

Juno Collaboration and License Agreement	12 Months Ended
	Dec. 31, 2016
Collaboration And License Agreements Disclosure [Abstract]
Juno Collaboration and License Agreement	2. Juno Collaboration and License Agreement On May 4, 2015, the Company entered into a strategic research collaboration and license agreement (the “Agreement”) with Juno Therapeutics, Inc. (“Juno”) to screen for and identify small molecules that enhance the therapeutic properties of Juno’s genetically-engineered T-cell immunotherapies. Pursuant to the terms of the Agreement, Juno paid the Company a non-refundable upfront payment of $5.0 million and purchased 1,000,000 shares of the Company’s common stock at a price of $8.00 per share. Additionally, Juno agreed to fund all of the Company’s collaboration research activities for an initial four-year research term beginning on the effective date of the Agreement, with minimum annual research payments of $2.0 million to the Company. Juno has the option to extend the exclusive research term for an additional two years beyond the initial four-year term, subject to the payment of an extension fee of $3.0 million and the continued funding of the Company’s activities under the collaboration during the extended term, with minimum annual research payments of $4.0 million to the Company during the two-year extension period. Upon exercise of the research term extension, the Company has the option to require Juno to purchase up to $10.0 million of the Company’s common stock at a premium equal to 120% of the then thirty-day trailing volume weighted average trading price of the Company’s common stock. The Company applied Accounting Standards Codification (“ASC”) 605-25, Revenue Recognition — Multiple Element Arrangements, Pursuant to the collaboration’s research plan under the Agreement, the Company is responsible for screening and identifying small molecule modulators of immunological cells, while Juno will be responsible for the development and commercialization of engineered T-cell immunotherapies incorporating the Company’s modulators. As the Company is principally responsible for the performance of the research services under the Agreement, revenue is recognized on a gross basis for such services when earned. Billings for research services will be recognized as deferred revenue until earned. Total revenue recognized under the Agreement for the years ended December 31, 2016 and 2015 was $4.4 million and $2.4 million, respectively. As of December 31, 2016, aggregate deferred revenue related to the Agreement was $4.9 million. Under the Agreement, the Company has granted Juno an exclusive worldwide license to certain of its intellectual property, including its intellectual property arising under the collaboration, to make, use, sell and otherwise exploit genetically-engineered T-cell immunotherapies using or incorporating small molecule modulators directed against certain designated tumor-associated antigen targets, subject to the selection of a target by Juno. The Company has retained exclusive rights to such intellectual property, including its intellectual property arising under the collaboration, for all other purposes, including its use outside of those targets selected by Juno. The Company is eligible under the Agreement to receive selection fees for each tumor-associated antigen target selected by Juno and bonus selection fees based on the aggregate number of tumor-associated antigen targets selected by Juno. In accordance with ASC 605-28, Revenue Recognition — Milestone Method, In connection with each Juno therapy that uses or incorporates the Company’s small molecule modulators, Juno has agreed to pay the Company non-refundable, non-creditable milestone payments totaling up to approximately $51.0 million in the aggregate per therapy upon the achievement of various clinical, regulatory and commercial milestones. Additionally, in connection with the third Juno therapy and the fifth Juno therapy that uses or incorporates the Company’s small molecule modulators, Juno has agreed to pay the Company additional non-refundable, non-creditable bonus milestone payments totaling up to approximately $116.0 million and $137.5 million, respectively, in the aggregate, per therapy upon the achievement of various clinical, regulatory, and commercial milestones. In accordance with ASU 2010-17, the Company determined that these contingent payments meet the definition of a milestone under ASU 2010-17, and that the milestones are substantive given that the milestones are commensurate with the Company’s performance, relate solely to the Company’s past performance, and are reasonable relative to other deliverables and payments under the Agreement. Accordingly, the milestones under the Agreement will be accounted for as revenue on the achievement date, if any. Beginning on the date of the first commercial sale (in each country) for each Juno therapy that uses or incorporates the Company’s small molecule modulators, and continuing until the later of: i) the expiration of the last valid patent claim, ii) ten years after such first commercial sale, or iii) the expiration of all data and other regulatory exclusivity periods afforded each therapy, Juno has agreed to pay the Company royalties in the low single-digits on net sales of each Juno therapy that uses or incorporates the Company’s small molecule modulators. The Agreement will end on the date that no further payments are due under the Agreement.

Short-term Investments

Short-term Investments	12 Months Ended
	Dec. 31, 2016
Short Term Investments [Abstract]
Short-term Investments	3. Short-term Investments During the year ended December 31, 2016, the Company invested excess cash in United States treasuries with maturities ranging from six to twelve months from the purchase date. These debt securities are classified as short-term investments in the accompanying consolidated balance sheets and are accounted for as available-for-sale securities. The following table summarizes the Company’s short-term investments accounted for as available-for-sale securities as of December 31, 2016 (no such investments were owned as of December 31, 2015) (in thousands): Maturity (in years) Amortized Cost Unrealized Losses Unrealized Gains Estimated Fair Value December 31, 2016 U.S. Treasury debt securities 1 or less 3,504 (1 ) — 3,503 Total $ 3,504 $ (1 ) $ — $ 3,503 The Company reviewed its investment holdings as of December 31, 2016 and determined that the unrealized losses were not other-than-temporary unrealized losses because the Company does not intend to sell the underlying securities prior to maturity and it is not more likely than not that the Company will be required to sell these securities before the recovery of their amortized cost basis. During the year ended December 31, 2016, the Company did not recognize any impairment or gains or losses on sales of available-for-sale securities.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Property and Equipment	4. Property and Equipment Property and equipment consist of the following (in thousands): December 31, 2016 2015 Furniture and fixtures $ 324 $ 324 Computer and office equipment 318 300 Software 103 103 Leasehold improvements—building 180 180 Scientific equipment 4,858 4,725 Property and equipment, gross 5,783 5,632 Less accumulated depreciation and amortization (4,204 ) (3,472 ) Property and equipment, net $ 1,579 $ 2,160 Depreciation expense related to property and equipment was $0.9 million, $0.7 million, and $0.5 million, for the years ended December 31, 2016, 2015, and 2014, respectively. No material gains or losses on the disposal of property and equipment have been recorded for the years ended December 31, 2016, 2015, and 2014.

Accrued Expenses, Long-Term Deb

Accrued Expenses, Long-Term Debt, Commitments and Contingencies	12 Months Ended
	Dec. 31, 2016
Accrued Expenses Long Term Debt Commitments And Contingencies Disclosure [Abstract]
Accrued Expenses, Long-Term Debt, Commitments and Contingencies	5. Accrued Expenses, Long-Term Debt, Commitments and Contingencies Accrued Expenses Current accrued expenses consist of the following (in thousands): December 31, 2016 December 31, 2015 Accrued payroll and other employee benefits $ 1,505 $ 993 Accrued clinical trial related costs 1,043 446 Accrued other 1,409 1,000 Accrued expenses $ 3,957 $ 2,439 During the year ended December 31, 2016, the Company issued 37,641 shares of its common stock to certain senior executives of the Company as consideration for a portion of their 2015 performance bonuses. All related amounts were accrued for as liabilities as of December 31, 2015. All amounts earned and paid for 2016 performance bonuses were paid in cash. Future senior executive bonus amounts, timing, and method of payment are at the sole discretion of the Board of Directors of the Company. As such, all relevant bonus estimates are accrued for as liabilities. Long-term accrued expenses consist primarily of accruals for the final payment fees associated with our long-term debt. Long-Term Debt Long-term debt and unamortized discount balances are as follows (in thousands): December 31, 2016 December 31, 2015 Long-term debt $ 10,765 $ 18,454 Less debt issuance costs and discount, net of current portion (7 ) (77 ) Long-term debt, net of long-term portion of debt issuance costs and discount 10,758 18,377 Less current portion of long-term debt (8,257 ) (7,689 ) Long-term debt, net $ 2,501 $ 10,688 Current portion of long-term debt $ 8,257 $ 7,689 Less current portion of debt issuance costs and discount (70 ) (139 ) Current portion of long-term debt, net $ 8,187 $ 7,550 On July 30, 2014, the Company entered into an Amended and Restated Loan and Security Agreement (the “Restated LSA”) with Silicon Valley Bank (the “Bank”), collateralized by substantially all of the Company’s assets, excluding certain intellectual property. The Restated LSA amends and restates the Loan and Security Agreement, dated as of January 5, 2009, as amended, by and between the Company and the Bank (the “Loan Agreement”). Pursuant to the Restated LSA, the Bank agreed to make loans to the Company in an aggregate principal amount of up to $20.0 million, comprised of (i) a $10.0 million term loan, funded at the closing date (the “Term A Loan”) and (ii) subject to the achievement of a specified clinical milestone relating to the Company’s Phase 2 clinical trial of ProHema, additional term loans totaling up to $10.0 million in the aggregate, which were available until December 31, 2014 (each, a “Term B Loan”). On December 24, 2014, the Company elected to draw on the full $10.0 million under a Term B Loan. The Term A Loan and the Term B Loan mature on January 1, 2018 and June 1, 2018, respectively and bear interest at a fixed annual rate of 6.94% and 7.07%, respectively. Interest became payable in cash on a monthly basis beginning the first day of each month following the month in which the funding date of each loan occurred. The Company is required to make a monthly payment of interest only during the first twelve months following the funding date of each loan, and thereafter is required to repay the principal and interest under each loan in thirty equal monthly installments based on a thirty-month amortization schedule. During the year ended December 31, 2016, the Company made principal payments totaling $3.9 million and $3.8 million, respectively, on the Term A Loan and Term B Loan. During the year ended December 31, 2015, the Company made principal payments totaling $1.5 million on the Term A Loan. The Company is required to make a final payment fee of 7.5%, equaling $0.8 million, of the funded amount for each of the Term A Loan and Term B Loan on the respective maturity dates. The final payment fees are accrued as interest expense over the terms of the loans and recorded in long-term accrued expenses. A portion of the proceeds from the Term A Loan were used to repay loans outstanding under the Loan Agreement and to pay for transaction fees related to the Restated LSA, including a commitment fee of $0.4 million paid by the Company to the Bank. Net proceeds from the Term A Loan, after repayment of loans outstanding under the Loan Agreement and transaction fees, were $8.8 million. The Company determined the repayment of the Loan Agreement was a debt extinguishment, and accounted for the Term A Loan at fair value as of the issuance date accordingly. During the year ended December 31, 2014, the Company recorded a loss on debt extinguishment of $0.4 million, primarily related to the commitment fee paid to the Bank. Proceeds from the Term B Loan were $10.0 million. In connection with the funding of the Term B Loan, the Company issued the Bank and one of its affiliates fully-exercisable warrants to purchase an aggregate of 98,039 shares of the Company’s common stock (the “Warrants”) at an exercise price of $4.08 per share. The Warrants expire in December 2021. The aggregate fair value of the Warrants was determined to be $0.4 million using the Black-Scholes option pricing model (see Note 6 of the Notes to the Consolidated Financial Statements for additional information) and was recorded as a debt discount on the Term B Loan and is amortized to interest expense over the term of the Term B Loan using the effective interest method. The Company determined the effective interest rates of the Term A Loan and Term B Loan to be 10.3% and 12.0%, respectively. For the years ended December 31, 2016, 2015, and 2014 the Company recorded $1.6 million, $2.2 million, and $0.5 million respectively, in aggregate interest expense related to the Term A and Term B Loans. For the year ended December 31, 2014 the Company recorded aggregate interest expense related to the Loan Agreement of $0.1 million. Warrants to purchase 36,074 shares of the Company’s common stock at a weighted average exercise price of $7.21 per share issued in connection with the Loan Agreement remain outstanding as of December 31, 2016, with 5,305 and 30,769 of such warrants having expiration dates in January 2019 and August 2021, respectively. In addition, the Company is required under the Loan Agreement to maintain its deposit and securities accounts with the Bank and to comply with various operating covenants and default clauses. A breach of any of these covenants or clauses could result in a default under the Loan Agreement, which would cause all of the outstanding indebtedness under the facility to become immediately due and payable. The Company is in compliance with all covenants and clauses. Facility Lease The Company leases certain office and laboratory space from a stockholder of the Company under a non-cancelable operating lease. In June 2016, the Company amended the operating lease, extending the term of the lease through June 2023 and agreeing to lease additional space comprising approximately 24,000 square feet in the same building as its existing space. The lease is subject to additional charges for common area maintenance and other costs. In connection with the lease, the Company entered into a cash-collateralized irrevocable standby letter of credit in the amount of $0.1 million. As of December 31, 2016, future minimum payments under the operating lease are $13.9 million. In January 2015, the Company entered into a sublease for additional laboratory space. The sublease is accounted for as an operating lease and expires in September 2017. Under the sublease, total future minimum payments as of December 31, 2016 are $0.2 million. Aggregate contractual rent expense for both leases was $1.3 million, $1.2 million, and $0.9 million for the years ended December 31, 2016, 2015, and 2014, respectively. License Agreements The Company has entered into exclusive license agreements with certain academic institutions and universities pursuant to which the Company acquired certain intellectual property. Pursuant to each agreement, as consideration for an exclusive license to the intellectual property, the Company paid a license fee, reimbursed the institution for historical patent costs and, in certain instances, issued the institution shares of restricted common stock. Additionally, under each agreement, the institution is generally eligible to receive future consideration including, but not limited to, annual maintenance fees, royalties, milestone payments and sublicensing fees. Each of the license agreements is generally cancelable by the Company, given appropriate prior written notice. Minimum annual payments to maintain these cancelable licenses total an aggregate of $0.3 million. Commitments Future minimum payments under the long-term debt and the non-cancelable operating leases as of December 31, 2016 are as follows (in thousands): Long–Term Debt Operating Leases Total Years Ending December 31, 2017 $ 8,757 1,237 $ 9,994 2018 4,055 2,116 6,171 2019 — 2,278 2,278 2020 — 2,346 2,346 2021 — 2,417 2,417 2022 — 2,489 2,489 2023 — 1,282 1,282 Total $ 12,812 $ 14,165 $ 26,977 Less interest (547 ) Less additional payments due upon maturity (1,500 ) Less unamortized debt discount and debt issuance costs (77 ) Less current portion of long–term debt (8,187 ) Long–term debt, net of current portion $ 2,501

Convertible Preferred Stock and

Convertible Preferred Stock and Stockholders' Equity	12 Months Ended
	Dec. 31, 2016
Convertible Preferred Stock And Stockholders Deficit Disclosure [Abstract]
Convertible Preferred Stock and Stockholders' Equity (Deficit)	6. Convertible Preferred Stock and Stockholders’ Equity Convertible Preferred Stock In November 2016, the Company completed a private placement of stock in which investors, certain of whom are affiliated with the directors and officers of the Company, purchased convertible preferred stock and common stock of the Company (the “November 2016 Placement”). The Company issued 2,819,549 shares of non-voting Class A Convertible Preferred Stock (the “Class A Preferred”) at $13.30 per share, each of which is convertible into five shares of common stock upon certain conditions defined in the Certificate of Designation of Preferences, Rights and Limitations of the Class A Preferred filed with the Delaware Secretary of State on November 22, 2016 (the “CoD”). The Class A Preferred were purchased exclusively by entities affiliated with Redmile Group, LLC (collectively, “Redmile”). Redmile is prohibited from converting the Class A Preferred into shares of the Company’s common stock if, as a result of conversion, Redmile, together with its affiliates, would own more than 9.99% of the Company’s common stock then issued and outstanding (the “Redmile Percentage Limitation”), which percentage may change at Redmile’s election upon 61 days’ notice to the Company to i) any other number less than or equal to 19.99% or (ii) subject to approval of the Company’s stockholders to the extent required in accordance with the NASDAQ Global Market rules, any number in excess of 19.99%. The Company also issued 7,236,837 shares of common stock at $2.66 per share as part of the November 2016 Placement. Gross proceeds from the November 2016 Placement were $56.7 million, and after giving effect to costs related to placement, net proceeds were $55.0 million. The rights of the Class A Preferred issued in November 2016 are set forth in the CoD. The Class A Preferred are non-voting shares and have a stated par value of $0.001 per share and are convertible into five shares of the Company’s common stock at a conversion price of $2.66 per share, which was the fair value of the Company’s common stock on the date of issuance. Holders of the Class A Preferred have the same dividend rights as holders of the Company’s common stock. Additionally, the liquidation preferences of the Class A Preferred are pari passu The Company evaluated the Class A Preferred for liability or equity classification under ASC 480, Distinguishing Liabilities from Equity, The Company has also evaluated the Class A Preferred in accordance with the provisions of ASC 815, Derivatives and Hedging, The issuance of convertible preferred stock could generate a beneficial conversion feature (“BCF”), which arises when a debt or equity security is issued with an embedded conversion option that is beneficial to the investor (or in-the-money) at inception because the conversion option has an effective strike price that is less than the market price of the underlying stock on the commitment date. The Class A Preferred have an effective conversion price of $2.66 per common share, which was equal to the market price of the Company’s stock on the commitment date. Therefore, no BCF is present. The Company also entered into a registration rights agreement (the “Registration Rights Agreement”) with certain of the purchasers in the November 2016 Placement, excluding those purchasers affiliated with the Company’s directors and officers, requiring the Company to register for the resale of the relevant shares. The Company registered all of the relevant shares issued in the placement for resale on a Form S-3 filed with the SEC, as required under the Registration Rights Agreement, and the registration statement was declared effective in January 2017. Description of Securities Dividends As of December 31, 2016, the Board of Directors of the Company has not declared any dividends. 2007 Equity Incentive Plan, 2013 Stock Option and Incentive Plan, and Inducement Equity Plan The Company adopted an Equity Incentive Plan in 2007 (the 2007 Plan) under which, as amended in August 2013, 2,423,072 shares of common stock were reserved for issuance to employees, nonemployee directors and consultants of the Company. The 2007 Plan provides for the grant of incentive stock options, non-statutory stock options, rights to purchase restricted stock, stock appreciation rights, dividend equivalents, stock payments, and restricted stock units to eligible recipients. In connection with the issuance of restricted common stock, the Company maintains a repurchase right where shares of restricted common stock are released from such repurchase right over a period of time of continued service by the recipient. Effective upon the completion of the Company’s IPO, the board of directors determined not to grant any further awards under the 2007 Plan. On August 28, 2013, the Company’s board of directors and stockholders approved and adopted the 2013 Stock Option and Incentive Plan (the “2013 Plan” and collectively with the 2007 Plan “the Plans”). The 2013 Plan became effective immediately prior to the Company’s IPO. Under the 2013 Plan, the Company may grant stock options, stock appreciation rights, restricted stock, restricted stock units and other awards to individuals who are then employees, officers, directors or consultants of the Company or its subsidiaries. A total of 1,020,000 shares of common stock were initially reserved for issuance under the 2013 Plan. The shares issuable pursuant to awards granted under the 2013 Plan will be authorized, but unissued shares. The shares of common stock underlying any awards from the 2013 Plan and the 2007 Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by us prior to vesting, satisfied without any issuance of common stock, expire or are otherwise terminated (other than by exercise) under the 2013 Plan and the 2007 Plan will be added back to the shares of common stock available for issuance under the 2013 Plan. In addition, the number of shares of stock available for issuance under the 2013 Plan will be automatically increased each January 1 by 4% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31 or such lesser number as determined by the compensation committee of the Company’s board of directors. Recipients of stock options under the Plans shall be eligible to purchase shares of the Company’s common stock at an exercise price equal to no less than the estimated fair value of such stock on the date of grant. Under the Plans, stock options generally vest 25% on the first anniversary of the original vesting date, with the balance vesting monthly over the remaining three years, or vest monthly over four years, unless they contain specific performance and/or market-based vesting provisions. The maximum term of stock options granted under the Plans is ten years. Restricted stock units under the 2013 Plan generally vest 50% on the second anniversary of the grant date, and 50% on the fourth anniversary of the grant date. Inducement Plan On May 10, 2016, the Company’s board of directors approved the Fate Therapeutics, Inc. Inducement Equity Plan (the “Inducement Plan”), the purpose of which is to enable the Company to grant equity awards to induce highly-qualified prospective officers and employees who are not employed by the Company to accept employment with the Company. Under the Inducement Plan, the Company may grant non-qualified stock options and restricted stock units. A total of 500,000 shares of common stock were initially reserved for issuance under the Inducement Plan. The shares of common stock underlying any awards from the Inducement Plan that are forfeited, cancelled, held back upon exercise or settlement of an award to satisfy the exercise price or tax withholding, reacquired by us prior to vesting, satisfied without any issuance of common stock, expire or are otherwise terminated (other than by exercise) under the Inducement Plan will be added back to the shares of common stock available for issuance under the Inducement Plan. Employee Stock Purchase Plan On September 13, 2013, the Company’s board of directors approved and adopted the 2013 Employee Stock Purchase Plan (the “ESPP”). A total of 729,000 shares of common stock were initially reserved for issuance under the ESPP. In addition, the number of shares of stock available for issuance under the ESPP will be automatically increased each January 1, beginning on January 1, 2015, by the lesser of (i) 2% of the outstanding number of shares of the Company’s common stock on the immediately preceding December 31, (ii) 450,000 shares, or (iii) such lesser number as determined by the compensation committee of the Company’s board of directors. No purchases have been made to date under the ESPP. Stock Options and Restricted Stock Awards Stock Options. The following table summarizes stock option activity and related information under all equity plans for the years ended December 31, 2016, 2015 and 2014: Options Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in 000s) Outstanding at December 31, 2013 1,726,991 $ 2.30 8.47 $ 7,203 Granted 885,624 6.62 Exercised (96,856 ) 1.65 Cancelled (89,790 ) 4.38 Outstanding at December 31, 2014 2,425,969 $ 3.83 8.06 $ 4,839 Granted 1,345,744 5.23 Exercised (227,215 ) 1.85 Cancelled (957,024 ) 4.20 Outstanding at December 31, 2015 2,587,474 $ 4.59 6.92 $ 1,486 Granted 2,245,240 2.62 Exercised (136,368 ) 1.44 Cancelled (785,996 ) 3.58 Outstanding at December 31, 2016 3,910,350 $ 3.77 8.28 $ 682 Options vested and expected to vest at December 31, 2016 3,785,029 $ 3.78 8.33 $ 679 Options exercisable at December 31, 2016 1,469,829 $ 4.61 7.39 $ 231 As of December 31, 2016, 2015 and 2014, the outstanding options included 73,600, 14,769, and 138,649, respectively, of performance-based options for which the achievement of the performance-based vesting provisions was determined not to be probable. The aggregate grant date fair value of these options at December 31, 2016, 2015 and 2014, was $0.1 million, $0.1 million and $0.6 million, respectively. For the years ended December 31, 2016, 2015 and 2014, the Company granted its employees 2.2 million, 1.2 million and 0.9 million stock options, respectively, at a weighted-average grant date fair value per share equal to $1.80, $3.54 and $5.10, respectively. As of December 31, 2016, 2015 and 2014, the unrecognized compensation cost related to outstanding options (excluding those with unachieved performance- based conditions) was $4.9 million, $3.8 million and $4.1 million, respectively, which is expected to be recognized as expense over approximately 2.6 years, 2.8 years and 2.6 years, respectively. The total intrinsic value, which is the amount by which the exercise price was exceeded by the price of the Company’s common stock on the date of exercise, of stock options exercised during the year ended December 31, 2016 was $0.1 million. Total cash received upon the exercise of stock options was $0.2 million for the year ended December 31, 2016. Restricted Stock Units. During the year ended December 31, 2015, the Company granted its employees 0.5 million restricted stock units at a weighted-average grant date price per share equal to $4.90 and as of December 31, 2016, no such units have been canceled or have vested, and no additional units have been granted. As of December 31, 2016 and 2015, the unrecognized compensation cost related to outstanding restricted stock units was $1.8 million and $2.4 million, respectively, which is expected to be recognized as expense over approximately 2.8 years and 3.8 years, respectively. Stock-Based Compensation Expense The allocation of stock-based compensation for all stock awards is as follows (in thousands): Years Ended December 31, 2016 2015 2014 Research and development $ 1,802 $ 1,241 $ 1,416 General and administrative 1,382 1,159 1,018 Total stock-based compensation expense $ 3,184 $ 2,400 $ 2,434 Employee Stock Option Grants. The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the employee stock option grants were as follows: Years Ended December 31, 2016 2015 2014 Risk–free interest rate 1.6 % 1.6 % 1.9 % Expected volatility 80 % 81 % 94 % Expected term (in years) 6.0 6.0 6.0 Expected dividend yield 0.0 % 0.0 % 0.0 % Risk-free interest rate. The Company bases the risk-free interest rate assumption on observed interest rates appropriate for the expected term of the stock option grants. Expected dividend yield. The Company bases the expected dividend yield assumption on the fact that it has never paid cash dividends and has no present intention to pay cash dividends. Expected volatility. Due to the Company’s limited operating history and lack of company-specific historical or implied volatility, the expected volatility assumption is based on historical volatilities of a peer group of similar companies whose share prices are publicly available. The peer group was developed based on companies in the biotechnology industry. Expected term. The expected term represents the period of time that options are expected to be outstanding. As the Company does not have sufficient historical exercise behavior, it determines the expected life assumption using the simplified method, which is an average of the contractual term of the option and its vesting period. Based on a low historical employee turnover experience, pre-vesting forfeitures for all employee stock option grants was estimated at 0% for each of the years ended December 31, 2016, 2015, and 2014. Non-Employee Stock Option Grants. The weighted-average assumptions used in the Black-Scholes option pricing model to determine the fair value of the non-employee stock option grants were as follows: Years Ended December 31, 2016 2015 2014 Risk–free interest rate 1.5 % 0.8 % 2.1 % Expected volatility 83 % 72 % 87 % Expected term (in years) 6.4 2.7 6.5 Expected dividend yield 0.0 % 0.0 % 0.0 % Warrants to Purchase Common Stock in Connection with Debt Issuance As a result of the financing of the Term B Loan on December 24, 2014, the Company issued the Bank and one of its affiliates fully-exercisable warrants to purchase an aggregate of 98,039 shares of the Company’s common stock at an exercise price of $4.08 per share. The warrants expire in December 2021. See Note 5 of the Notes to the Consolidated Financial Statements for additional information on the debt issuance. The fair value of the warrants was determined to be $0.4 million, which was recorded to additional paid-in capital as a debt discount. The weighted- average assumptions used in the Black-Scholes option pricing model to determine the fair value of the warrants issued were as follows: As of December 24, 2014 Risk–free interest rate 2.1 % Expected volatility 85 % Expected term (in years) 7.0 Expected dividend yield 0.0 % Common Stock Reserved for Future Issuance Common stock reserved for future issuance is as follows: December 31, 2016 2015 Common stock warrants 134,113 134,113 Convertible preferred stock (if converted) 14,097,745 — Common stock options 3,910,350 2,587,474 Restricted stock units 525,250 525,250 Awards available under the 2013 Plan 760,065 908,288 Awards available under the Inducement Plan 300,000 — Employee stock purchase plan 729,000 729,000 20,456,523 4,884,125

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes The following is a reconciliation of the Company’s expected federal income tax provision (benefit) to the actual income tax provision (in thousands): Years Ended December 31, 2016 2015 2014 Tax computed at federal statutory rate $ (11,377 ) $ (10,198 ) $ (8,800 ) State tax, net of federal tax benefit (2,089 ) 2,226 (1,311 ) Permanent differences 292 43 159 Stock compensation 968 213 426 R&D tax credits (971 ) (594 ) (596 ) Reserve for uncertain tax positions 2,076 1,733 — Tax attribute limitation 54 2,727 — Other (74 ) (37 ) (256 ) Valuation allowance 11,121 3,887 10,378 Income tax expense $ — $ — $ — Significant components of the Company’s deferred tax assets are summarized as follows (in thousands): As of December 31, 2016 2015 Deferred tax assets: Section 59e amortization $ 17,699 $ 13,042 Net operating losses 35,049 28,963 R&D tax credits 2,175 1,274 Depreciation and amortization 1,020 921 Deferred revenue 1,677 2,494 Stock compensation 1,222 1,109 Other (76 ) (159 ) Deferred tax assets 58,766 47,644 Valuation allowance (58,766 ) (47,644 ) Net deferred tax assets $ — $ — A valuation allowance of $58.8 million and $47.6 million at December 31, 2016 and 2015, respectively, has been established to offset the deferred tax assets, as realization of such assets is uncertain. At December 31, 2016, the Company had federal and California net operating loss (“NOL”) carryforwards of $97.9 million and $98.0 million, respectively, which may be available to offset future taxable income. The federal and California NOL carryforwards begin to expire in 2027 and 2028, respectively, unless previously utilized. At December 31, 2016, the Company had federal and California research and development (“R&D”) credit carryforwards of $1.4 million and $3.4 million, respectively. The federal R&D tax credit carryforwards will begin to expire in 2035 unless previously utilized. The California R&D credit carryforwards will carry forward indefinitely. Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended, or the Code, substantial changes in our ownership may limit the amount of net operating loss and research and development credit carryforwards that could be used annually in the future to offset taxable income. The tax benefits related to future utilization of federal and state net operating loss carryforwards, credit carryforwards, and other deferred tax assets may be limited or lost if cumulative changes in ownership exceeds 50% within any three-year period. The Company completed a study to assess whether an ownership change, as defined by Section 382 of the Internal Revenue Code of 1986, had occurred from the Company’s formation through December 31, 2015. Based upon this study, the Company determined that several ownership changes had occurred. Accordingly, the Company reduced its deferred tax assets related to the federal NOL carryforwards and the federal R&D credit carryforwards that are anticipated to expire unused as a result of these ownership changes. These tax attributes were excluded from deferred tax assets with a corresponding reduction of the valuation allowance with no net effect on income tax expense or the effective tax rate. The Company updated the study through December 31, 2016 and concluded there were no ownership changes during 2016. Future ownership changes may further limit the Company’s ability to utilize its remaining tax attributes. The Company files income tax returns in the United States, California and Canada. The Company currently has no years under examination by any jurisdiction; however, the Company is subject to income tax examination by federal, Californian and Canadian tax authorities for years beginning in 2013, 2012, and 2012, respectively. However, to the extent allowed by law, the taxing authorities may have the right to examine prior periods where NOLs and tax credits were generated and carried forward, and make adjustments up to the amount of the carryforwards. The change in the Company’s unrecognized tax benefits is summarized as follows (in thousands): Balance at December 31, 2013 $ 1,329 Increase related to current year tax positions 491 Balance at December 31, 2014 $ 1,820 Increase related to current year tax positions 374 Increase related to prior year tax positions 2,624 Decrease related to prior year tax positions (949 ) Balance at December 31, 2015 $ 3,869 Increase related to current year tax positions 2,268 Increase related to prior year tax positions 1,625 Decrease related to prior year tax positions (32 ) Balance at December 31, 2016 $ 7,730 The Company does not anticipate that the amount of unrecognized tax benefits as of December 31, 2016 will significantly change within the next twelve months. Due to the valuation allowance recorded against the Company’s deferred tax assets, none of the total unrecognized tax benefits as of December 31, 2016 would reduce the effective tax rate if recognized. The Company has not recognized interest or penalties in its consolidated statements of operations and comprehensive loss since inception. During the year ended December 31, 2015, the Company adopted ASU 2015-17 and applied the standard prospectively (prior period amounts were not retrospectively adjusted). With this adoption, our deferred tax assets and liabilities are no longer classified between current and non-current. All deferred tax assets and liabilities are now classified as non-current regardless of their classification on the balance sheet and the timing of their anticipated reversal. As of December 31, 2016, the Company has not adopted ASU No. 2016-09, Compensation - Stock Compensation (Topic 718): Improvements to Employee Shared-Based Payment Accounting (''ASU 2016-09''). ASU 2016-09 simplifies how several aspects of share-based payments are accounted for and presented in the financial statements. ASU 2016-09 is effective for public companies for annual reporting periods beginning after December 15, 2016.The Company has excess tax benefits for which a benefit could not be previously recognized of $0.1 million. Upon adoption, the balance of the unrecognized excess tax benefits will be reversed with the impact recorded to retained earnings including any change to the valuation allowance as a result of the adoption. Due to the full valuation allowance on the U.S. deferred tax assets, the Company does not expect any impact to the financial statements as a result of this adoption.

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Employee Benefits	8. Employee Benefits Effective January 1, 2009, the Company adopted a defined contribution 401(k) plan for employees who are at least 21 years of age. Employees are eligible to participate in the plan beginning on the first day of the calendar quarter following date of hire. Under the terms of the plan, employees may make voluntary contributions as a percent of compensation. No matching contributions have been made by the Company since the adoption of the 401(k) plan.

Selected Quarterly Financial Da

Selected Quarterly Financial Data	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data	9. Selected Quarterly Financial Data (in thousands, except per share data) (unaudited) First Quarter Second Quarter Third Quarter Fourth Quarter 2016 Revenues $ 1,322 $ 1,027 $ 1,026 $ 1,027 Total operating expenses 9,238 9,031 9,415 8,681 Net loss (8,377 ) (8,408 ) (8,737 ) (7,940 ) Basic and diluted net loss per common share $ (0.29 ) $ (0.29 ) $ (0.27 ) $ (0.21 ) 2015 Revenues $ — $ 329 $ 1,026 $ 1,076 Total operating expenses 7,324 7,547 7,354 7,988 Net loss (7,881 ) (7,779 ) (6,886 ) (7,446 ) Basic and diluted net loss per common share $ (0.38 ) $ (0.33 ) $ (0.24 ) $ (0.26 )

Organization and Summary of S16

Organization and Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Follow-on Public Equity Offering	Follow-on Public Equity Offering In May 2015, the Company completed a public offering of common stock in which the Company sold 6,900,000 shares of its common stock at an offering price of $5.00 per share. Gross proceeds from the offering were $34.5 million. Total underwriting discounts, commissions, and other cash costs related to the offering were $2.4 million. After giving effect to all such costs, total net proceeds from the offering were $32.1 million.
Private Placement of Common Stock and Convertible Preferred Stock	Private Placements of Common Stock and Convertible Preferred Stock In August 2016, the Company completed a private placement of common stock in which investors purchased 5,250,000 shares of the Company’s common stock at a price of $1.96 per share. Gross proceeds from the private placement were $10.3 million. After giving effect to costs related to the private placement, net proceeds were $10.2 million. The Company also registered all of the shares issued in the private placement transaction for resale on a Form S-3 filed with the Securities and Exchange Commission (the “SEC”), as required under a registration rights agreement entered into by the Company with the purchasers of the common stock, and the registration statement was declared effective in September 2016. In November 2016, the Company completed a private placement of common and preferred stock in which investors, including investors affiliated with the Company’s directors and officers, purchased convertible preferred stock and common stock of the Company. The Company issued 2,819,549 shares of non-voting Class A Preferred Stock at $13.30 per share, each of which is convertible into five shares of common stock upon certain conditions. The Company also issued 7,236,837 shares of common stock at $2.66 per share. Gross proceeds from the private placement were $56.7 million. After giving effect to costs related to the private placement, net proceeds were $55.0 million. The Company also entered into a registration rights agreement (the “Registration Rights Agreement”) with certain of the purchasers in the November 2016 placement, excluding those purchasers affiliated with the Company’s directors and officers, requiring the Company to register for the resale of the relevant shares. The Company registered all of the relevant shares issued in the placement for resale on a Form S-3 filed with the SEC, as required under the Registration Rights Agreement, and the registration statement was declared effective in January 2017. See Note 6 to the Consolidated Financial Statements for additional information related to this offering.
Use of Estimates	Use of Estimates The Company’s consolidated financial statements are prepared in accordance with United States generally accepted accounting principles (“GAAP”). The preparation of the Company’s consolidated financial statements requires it to make estimates and assumptions that impact the reported amounts of assets, liabilities, revenues and expenses and the disclosure of contingent assets and liabilities in the Company’s consolidated financial statements and accompanying notes. The most significant estimates in the Company’s consolidated financial statements relate to accrued expenses. Although these estimates are based on the Company’s knowledge of current events and actions it may undertake in the future, actual results may ultimately materially differ from these estimates and assumptions.
Principles of Consolidation	Principles of Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries, Fate Therapeutics (Canada), Inc. or “Fate Canada”, incorporated in Canada and which was dissolved in November 2016, Fate Therapeutics Ltd., incorporated in the United Kingdom, and Tfinity Therapeutics, Inc., incorporated in the United States. To date, the aggregate operations of these subsidiaries have not been significant and all intercompany transactions and balances have been eliminated in consolidation.
Segment Reporting	Segment Reporting Operating segments are identified as components of an enterprise about which separate discrete financial information is available for evaluation by the chief operating decision-maker in making decisions regarding resource allocation and assessing performance. The Company views its operations and manages its business in one operating segment.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of accounts payable and accrued liabilities are considered to be representative of their respective fair values because of the short-term nature of those instruments. Based on the borrowing rates available to the Company for loans with similar terms, which is considered a Level 2 input as described below, the Company believes that the fair value of long-term debt approximates its carrying value. The accounting guidance defines fair value, establishes a consistent framework for measuring fair value and expands disclosure for each major asset and liability category measured at fair value on either a recurring or nonrecurring basis. Fair value is defined as an exit price, representing the amount that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or liability. As a basis for considering such assumptions, the accounting guidance establishes a three- tier fair value hierarchy, which prioritizes the inputs used in measuring fair value as follows: Level 1: Observable inputs such as quoted prices in active markets; Level 2: Inputs, other than the quoted prices in active markets, that are observable either directly or indirectly; and Level 3: Unobservable inputs in which there is little or no market data, which require the reporting entity to develop its own assumptions. Financial assets measured at fair value on a recurring basis consist of the Company’s cash equivalents and short-term investments. Cash equivalents consisted of money market funds and short-term investments consisted of U.S. treasuries. The following table presents the Company’s assets which were measured at fair value on a recurring basis as of December 31, 2016 and 2015 (in thousands): Fair Value Measurements at Reporting Date Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) As of December 31, 2016: Cash equivalents $ 88,609 $ 88,609 $ — $ — U.S. Treasury debt securities 3,503 3,503 — — Total assets $ 92,112 $ 92,112 $ — $ — As of December 31, 2015: Cash equivalents $ 35,257 $ 35,257 $ — $ — Total assets $ 35,257 $ 35,257 $ — $ — The Company obtains pricing information from its investment manager and generally determines the fair value of investment securities using standard observable inputs, including reported trades, broker/dealer quotes, and bid and/or offers. None of the Company’s non-financial assets or liabilities is recorded at fair value on a non-recurring basis. No transfers between levels have occurred during the periods presented. As of December 31, 2016 and 2015, the Company had no material liabilities measured at fair value on a recurring basis.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents include cash in readily available checking and savings accounts, money market accounts and money market funds. The Company considers all highly liquid investments with an original maturity of three months or less from the date of purchase to be cash equivalents.
Short Term Investments	Short-Term Investments Available-for-sale securities are carried at fair value, with the unrealized gains and losses reported in comprehensive income. The amortized cost of available-for-sale debt securities is adjusted for amortization of premiums and accretion of discounts to maturity. Such amortization and accretion is included in interest income. Realized gains and losses and declines in value judged to be other-than-temporary, if any, on available-for-sale securities are included in other income or expense. The cost of securities sold is based on the specific identification method. Interest and dividends on securities classified as available-for-sale are included in interest income.
Concentration of Credit Risk	Concentration of Credit Risk Financial instruments, which potentially subject the Company to significant concentration of credit risk, consist primarily of cash, cash equivalents, and short-term investments. The Company maintains deposits in federally insured financial institutions in excess of federally insured limits. The Company has not experienced any losses in such accounts and management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits and investments are held.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost and depreciated using the straight-line method over the estimated useful lives of the assets (generally two to five years) and generally consist of furniture and fixtures, computers, and scientific and office equipment. Repairs and maintenance costs are charged to expense as incurred.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets Long-lived assets consist primarily of property and equipment. An impairment loss is recorded if and when events and circumstances indicate that assets might be impaired and the undiscounted cash flows estimated to be generated by those assets are less than the carrying amount of those assets. While the Company’s current and historical operating losses and negative cash flows are indicators of impairment, management believes that future cash flows to be received support the carrying value of its long-lived assets and, accordingly, has not recognized any impairment losses since inception.
Deferred Rent	Deferred Rent Deferred rent consists of the difference between cash payments and the recognition of rent expense on a straight-line basis for the facilities the Company occupies. The Company’s leases for its facilities provide for fixed increases in minimum annual rental payments. The total amount of rental payments due over the lease terms are charged to rent expense ratably over the life of the leases.
Revenue Recognition	Revenue Recognition The Company recognizes revenues when all four of the following criteria are met: (i) persuasive evidence that an agreement exists; (ii) delivery of the products and/or services has occurred; (iii) the selling price is fixed or determinable; and (iv) collectability is reasonably assured. Revenue arrangements with multiple elements are analyzed to determine whether the elements can be divided into separate units of accounting or whether the elements must be accounted for as a single unit of accounting. The Company divides the elements into separate units of accounting and applies the applicable revenue recognition criteria to each of the elements, if the delivered elements have value to the customer on a stand-alone basis, if the arrangement includes a general right of return relative to the delivered elements, and if the delivery or performance of the undelivered elements is considered probable and substantially within the Company’s control. Revenue has been allocated to each element at the inception of the arrangement using the relative selling price method that is based on a three-tier hierarchy. The relative selling price method requires that the estimated selling price for each element be based on vendor-specific objective evidence (“VSOE”) of fair value, which represents the price charged for each element when it is sold separately or, for an element not yet being sold separately, the price established by management. When VSOE of fair value is not available, third-party evidence (“TPE”) of fair value is acceptable, or a best estimate of selling price is used if neither VSOE nor TPE is available. A best estimate of selling price should be consistent with the objective of determining the price at which the Company would transact if the element were sold regularly on a stand-alone basis and should also take into account market conditions and company-specific factors. Revenue arrangements with multiple elements may include license fees, research and development payments, milestone payments, other contingent payments, and royalties on any product sales derived from collaborations. The Company recognizes nonrefundable license fees with stand-alone value as revenue at the time that the Company has satisfied all performance obligations, and recognizes license fees without stand-alone value as revenue in combination with any undelivered performance obligations. The Company recognizes a research and development payment as revenue over the term of the collaboration agreement as contracted amounts are earned, or reimbursable costs are incurred, under the agreement, where contracted amounts are considered to be earned in relative proportion to the performance required under the applicable agreement. The Company recognizes a milestone payment, which is contingent upon the achievement of a milestone in its entirety, as revenue in the period in which the milestone is achieved only if the milestone meets all criteria to be considered substantive. These criteria include the following: (i) the consideration being earned should be commensurate with either the Company’s performance to achieve the milestone or the enhancement of the value of the item delivered as a result of a specific outcome resulting from the Company’s performance to achieve the milestone; (ii) the consideration being earned should relate solely to past performance; (iii) the consideration being earned should be reasonable relative to all deliverables and payment terms in the arrangement; and (iv) the milestone should be considered in its entirety and cannot be bifurcated into substantive and nonsubstantive components. Any amounts received pursuant to revenue arrangements with multiple elements prior to satisfying the Company’s revenue recognition criteria are recorded as deferred revenue on the Company’s consolidated balance sheets. Revenue from government grants is recorded when reimbursable expenses are incurred under the grant in accordance with the terms of the grant award.
Research and Development Costs	Research and Development Costs All research and development costs are expensed as incurred.
Patent Costs	Patent Costs Costs related to filing and pursuing patent applications are recorded as general and administrative expense and expensed as incurred since recoverability of such expenditures is uncertain.
Stock-Based Compensation	Stock-Based Compensation Stock-based compensation expense represents the cost of the grant date fair value of employee stock option and restricted stock unit grants recognized over the requisite service period of the awards (usually the vesting period) on a straight-line basis, net of estimated forfeitures. For stock option grants for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the achievement of the milestone is probable or the performance condition has been achieved. For stock option grants for which vesting is subject to both performance-based milestones and market conditions, expense is recorded over the derived service period after the point when the achievement of the performance-based milestone is probable or the performance condition has been achieved. The Company estimates the fair value of stock option grants using the Black-Scholes option pricing model, with the exception of option grants for which vesting is subject to both performance-based milestones and market conditions, which are valued using a lattice-based model. The fair value of restricted stock units is based on the closing price of the Company’s common stock as reported on The NASDAQ Global Market on the date of grant. The Company accounts for stock options and restricted stock awards to non-employees using the fair value approach. Stock options and restricted stock awards to non-employees are subject to periodic revaluation over their vesting terms. For stock option grants for which vesting is subject to performance-based milestones, the expense is recorded over the remaining service period after the point when the performance condition is determined to be probable of achievement or when it has been achieved.
Convertible Preferred Stock	Convertible Preferred Stock The Company applies the relevant accounting standards to distinguish liabilities from equity when assessing the classification and measurement of preferred stock. Preferred shares subject to mandatory redemptions are considered liabilities and measured at fair value. Conditionally redeemable preferred shares are considered temporary equity. All other preferred shares are considered as stockholders’ equity. The Company applies the relevant accounting standards for derivatives and hedging (in addition to distinguishing liabilities from equity) when accounting for hybrid contracts that contain conversion options. Conversion options must be bifurcated from the host instruments and accounted for as free standing financial instruments according to certain criteria. These criteria include circumstances when (i) the economic characteristics and risks of the embedded derivative instruments are not clearly and closely related to the economic characteristics and risks of the host contract, (ii) the hybrid instrument that embodies both the embedded derivative instrument and the host contract is not re-measured at fair value under otherwise applicable accounting principles with changes in fair value reported in earnings as they occurred, and (iii) a separate instrument with the same terms as the embedded derivative instrument would be considered a derivative instrument. The derivative is subsequently measured at fair value at each reporting date, with the changes in fair value reported in earnings.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statements and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes net deferred tax assets to the extent that the Company believes these assets are more likely than not to be realized. In making such a determination, management considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning strategies, and results of recent operations. If management determines that the Company would be able to realize its deferred tax assets in the future in excess of their net recorded amount, management would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions on the basis of a two-step process whereby (1) management determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more- likely-than-not recognition threshold, management recognizes the largest amount of tax benefit that is more than 50 percent likely to be realized upon ultimate settlement with the related tax authority. The Company recognizes interest and penalties related to unrecognized tax benefits within income tax expense. Any accrued interest and penalties are included within the related tax liability.
Comprehensive Loss	Comprehensive Loss Comprehensive loss is defined as a change in equity during a period from transactions and other events and circumstances from non-owner sources. Other comprehensive loss included unrealized losses on available-for-sale securities, which was the only difference between net loss and comprehensive loss for the applicable periods.
Net Loss Per Common Share	Net Loss Per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding for the period, without consideration for common stock equivalents. Excluded from the weighted-average number of shares outstanding are shares which have been issued upon the early exercise of stock options and are subject to future vesting and unvested restricted stock totaling 3,284 shares, 44,381 shares, and 76,947 shares for the years ended December 31, 2016, 2015, and 2014, respectively. Diluted net loss per common share is calculated by dividing the net loss by the weighted-average number of common share equivalents outstanding for the period determined using the treasury-stock method. Dilutive common stock equivalents are comprised of convertible preferred stock, warrants for the purchase of common stock, and common stock options and restricted stock units outstanding under the Company’s stock option plans. For all periods presented, there is no difference in the number of common shares used to calculate basic and diluted common shares outstanding due to the Company’s net loss position. Potentially dilutive securities not included in the calculation of diluted net loss per common share because to do so would be anti-dilutive are as follows (in common stock equivalent shares): As of December 31, 2016 2015 2014 Warrants for common stock 134,113 134,113 134,113 Common stock options 3,910,350 2,587,474 2,425,969 Restricted stock units 525,250 525,250 — Series A convertible preferred stock (if converted) 14,097,745 — — 18,667,458 3,246,837 2,560,082
Recent Accounting Pronouncements	Recent Accounting Pronouncements In March 2016, the Financial Accounting Standards Board (the “FASB”) issued Accounting Standards Update No. 2016-09 (ASU 2016-09). ASU 2016-09 simplifies several aspects of the accounting for share-based payment transactions, including the income tax consequences, classification of awards as either equity or liabilities, and classification on the statement of cash flows. ASU 2016-09 is effective for fiscal periods beginning after December 15, 2016, with early adoption permitted. The Company believes the ultimate adoption of this guidance will not have a material impact on its Consolidated Financial Statements. In February 2016, the FASB issued ASU 2016-02, which requires an entity to recognize assets and liabilities arising from a lease for both financing and operating leases, along with additional qualitative and quantitative disclosures. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The Company is currently evaluating the effect this standard will have on its Consolidated Financial Statements. In November 2015, the FASB issued ASU 2015-17, which requires that all deferred tax assets and liabilities be classified as noncurrent on the balance sheet, instead of separating deferred taxes into current and noncurrent amounts. The update is effective for financial statements issued for fiscal years beginning after December 15, 2016. As early adoption of this amendment is permitted, the Company has adopted the update prospectively during the year ended December 31, 2015. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In April 2015, the FASB issued ASU 2015-03, which requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. The update is effective for financial statements issued for fiscal years beginning after December 15, 2015. As early adoption of this amendment is permitted, the Company has implemented the update accordingly by reclassifying prior period and current period amounts from assets to liabilities. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In August 2014, the FASB issued ASU 2014-15, which defined management’s responsibility to evaluate whether there is substantial doubt about an entity’s ability to continue as a going concern and to provide related disclosure. ASU 2014-15 defined the term substantial doubt and requires an assessment for a period of one year after the date of the issuance of the financial statements. It requires certain disclosures when substantial doubt is alleviated as a result of consideration of management’s plans and requires an express statement and other disclosures when substantial doubt is not alleviated. The guidance became effective for reporting periods ending after December 15, 2016. The adoption of this guidance did not have a material impact on the Company’s Consolidated Financial Statements. In May 2014, the FASB issued ASU 2014-09, which created a single, principle-based revenue recognition model that will supersede and replace nearly all existing U.S. GAAP revenue recognition guidance. Entities will recognize revenue in a manner that depicts the transfer of goods or services to customers at an amount that reflects the consideration to which the entity expects to be entitled to receive in exchange for those goods or services. The model provides that entities follow five steps: (i) identify the contract with a customer, (ii) identify the performance obligations in the contract, (iii) determine the transaction price, (iv) allocate the transaction price to the performance obligations, and (v) recognize revenue. For public business entities, ASU 2014-09 is effective beginning in the first quarter of 2018 using one of two prescribed transition methods: retrospectively to each prior reporting period presented (full retrospective method), or retrospectively with the cumulative effect of initially applying the guidance recognized at the date of initial application (the cumulative catch-up transition method). The Company expects to adopt ASU 2014-09 in the first quarter of 2018 using the full retrospective method to restate each prior reporting period presented. The Company is currently evaluating the effect that the updated standard and transition method will have on its internal processes, financial statements and related disclosures. While the Company continues to assess all potential impacts under ASU 2014-09, recognition of the Company’s revenue under the new standard is expected to be materially consistent with the Company’s current revenue recognition policy. The new standard is not expected to materially impact the timing or amounts of revenue recognized.
Going Concern Assessment	Going Concern Assessment Pursuant to ASU 2014-15, the Company has assessed its ability to continue as a going concern for a period of one year from the date of the issuance of these financial statements. Substantial doubt about an entity’s ability to continue as a going concern exists when relevant conditions and events, considered in the aggregate, indicate that it is probable that the entity will be unable to meet its obligations as they become due within one year from the financial statement issuance date. The Company determined that there are no conditions or events that raise substantial doubt about its ability to continue as a going concern.

Organization and Summary of S17

Organization and Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2016
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Assets Measured at Fair Value on Recurring Basis	The following table presents the Company’s assets which were measured at fair value on a recurring basis as of December 31, 2016 and 2015 (in thousands): Fair Value Measurements at Reporting Date Using Total Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) As of December 31, 2016: Cash equivalents $ 88,609 $ 88,609 $ — $ — U.S. Treasury debt securities 3,503 3,503 — — Total assets $ 92,112 $ 92,112 $ — $ — As of December 31, 2015: Cash equivalents $ 35,257 $ 35,257 $ — $ — Total assets $ 35,257 $ 35,257 $ — $ —
Schedule of Anti-Dilutive Securities not Included in Calculation of Diluted Net Loss Per Common Share	As of December 31, 2016 2015 2014 Warrants for common stock 134,113 134,113 134,113 Common stock options 3,910,350 2,587,474 2,425,969 Restricted stock units 525,250 525,250 — Series A convertible preferred stock (if converted) 14,097,745 — — 18,667,458 3,246,837 2,560,082

Short-term Investments (Tables)

Short-term Investments (Tables)	12 Months Ended
	Dec. 31, 2016
Short Term Investments [Abstract]
Summary of Short-term Investments	The following table summarizes the Company’s short-term investments accounted for as available-for-sale securities as of December 31, 2016 (no such investments were owned as of December 31, 2015) (in thousands): Maturity (in years) Amortized Cost Unrealized Losses Unrealized Gains Estimated Fair Value December 31, 2016 U.S. Treasury debt securities 1 or less 3,504 (1 ) — 3,503 Total $ 3,504 $ (1 ) $ — $ 3,503

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2016
Property Plant And Equipment [Abstract]
Schedule of property and equipment	Property and equipment consist of the following (in thousands): December 31, 2016 2015 Furniture and fixtures $ 324 $ 324 Computer and office equipment 318 300 Software 103 103 Leasehold improvements—building 180 180 Scientific equipment 4,858 4,725 Property and equipment, gross 5,783 5,632 Less accumulated depreciation and amortization (4,204 ) (3,472 ) Property and equipment, net $ 1,579 $ 2,160

Accrued Expenses, Long-Term D20

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2016
Accrued Expenses Long Term Debt Commitments And Contingencies Disclosure [Abstract]
Schedule of accrued expenses	Current accrued expenses consist of the following (in thousands): December 31, 2016 December 31, 2015 Accrued payroll and other employee benefits $ 1,505 $ 993 Accrued clinical trial related costs 1,043 446 Accrued other 1,409 1,000 Accrued expenses $ 3,957 $ 2,439
Schedule of long-term debt and unamortized discount balances	Long-term debt and unamortized discount balances are as follows (in thousands): December 31, 2016 December 31, 2015 Long-term debt $ 10,765 $ 18,454 Less debt issuance costs and discount, net of current portion (7 ) (77 ) Long-term debt, net of long-term portion of debt issuance costs and discount 10,758 18,377 Less current portion of long-term debt (8,257 ) (7,689 ) Long-term debt, net $ 2,501 $ 10,688 Current portion of long-term debt $ 8,257 $ 7,689 Less current portion of debt issuance costs and discount (70 ) (139 ) Current portion of long-term debt, net $ 8,187 $ 7,550
Schedule of future minimum payments under the long-term debt and the non-cancelable operating leases	Future minimum payments under the long-term debt and the non-cancelable operating leases as of December 31, 2016 are as follows (in thousands): Long–Term Debt Operating Leases Total Years Ending December 31, 2017 $ 8,757 1,237 $ 9,994 2018 4,055 2,116 6,171 2019 — 2,278 2,278 2020 — 2,346 2,346 2021 — 2,417 2,417 2022 — 2,489 2,489 2023 — 1,282 1,282 Total $ 12,812 $ 14,165 $ 26,977 Less interest (547 ) Less additional payments due upon maturity (1,500 ) Less unamortized debt discount and debt issuance costs (77 ) Less current portion of long–term debt (8,187 ) Long–term debt, net of current portion $ 2,501

Convertible Preferred Stock a21

Convertible Preferred Stock and Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2016
Stockholders' Equity
Schedule of allocation of stock-based compensation for all options and restricted stock awards	Options Weighted Average Exercise Price Per Share Weighted Average Remaining Contractual Term Aggregate Intrinsic Value (in 000s) Outstanding at December 31, 2013 1,726,991 $ 2.30 8.47 $ 7,203 Granted 885,624 6.62 Exercised (96,856 ) 1.65 Cancelled (89,790 ) 4.38 Outstanding at December 31, 2014 2,425,969 $ 3.83 8.06 $ 4,839 Granted 1,345,744 5.23 Exercised (227,215 ) 1.85 Cancelled (957,024 ) 4.20 Outstanding at December 31, 2015 2,587,474 $ 4.59 6.92 $ 1,486 Granted 2,245,240 2.62 Exercised (136,368 ) 1.44 Cancelled (785,996 ) 3.58 Outstanding at December 31, 2016 3,910,350 $ 3.77 8.28 $ 682 Options vested and expected to vest at December 31, 2016 3,785,029 $ 3.78 8.33 $ 679 Options exercisable at December 31, 2016 1,469,829 $ 4.61 7.39 $ 231
Schedule of common stock reserved for future issuance	December 31, 2016 2015 Common stock warrants 134,113 134,113 Convertible preferred stock (if converted) 14,097,745 — Common stock options 3,910,350 2,587,474 Restricted stock units 525,250 525,250 Awards available under the 2013 Plan 760,065 908,288 Awards available under the Inducement Plan 300,000 — Employee stock purchase plan 729,000 729,000 20,456,523 4,884,125
Warrant
Stockholders' Equity
Schedule of weighted-average assumptions used to determine the fair value of stock option grants	As of December 24, 2014 Risk–free interest rate 2.1 % Expected volatility 85 % Expected term (in years) 7.0 Expected dividend yield 0.0 %
Employee Stock Option
Stockholders' Equity
Schedule of weighted-average assumptions used to determine the fair value of stock option grants	Years Ended December 31, 2016 2015 2014 Risk–free interest rate 1.6 % 1.6 % 1.9 % Expected volatility 80 % 81 % 94 % Expected term (in years) 6.0 6.0 6.0 Expected dividend yield 0.0 % 0.0 % 0.0 %
Non Employee Stock Option
Stockholders' Equity
Schedule of weighted-average assumptions used to determine the fair value of stock option grants	Years Ended December 31, 2016 2015 2014 Risk–free interest rate 1.5 % 0.8 % 2.1 % Expected volatility 83 % 72 % 87 % Expected term (in years) 6.4 2.7 6.5 Expected dividend yield 0.0 % 0.0 % 0.0 %
Stock Option And Incentive Plan 2007 And 2013
Stockholders' Equity
Summary of outstanding restricted stock awards granted under the plan	The allocation of stock-based compensation for all stock awards is as follows (in thousands): Years Ended December 31, 2016 2015 2014 Research and development $ 1,802 $ 1,241 $ 1,416 General and administrative 1,382 1,159 1,018 Total stock-based compensation expense $ 3,184 $ 2,400 $ 2,434

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of reconciliation of the Company's expected federal income tax provision (benefit) to the actual income tax provision	The following is a reconciliation of the Company’s expected federal income tax provision (benefit) to the actual income tax provision (in thousands): Years Ended December 31, 2016 2015 2014 Tax computed at federal statutory rate $ (11,377 ) $ (10,198 ) $ (8,800 ) State tax, net of federal tax benefit (2,089 ) 2,226 (1,311 ) Permanent differences 292 43 159 Stock compensation 968 213 426 R&D tax credits (971 ) (594 ) (596 ) Reserve for uncertain tax positions 2,076 1,733 — Tax attribute limitation 54 2,727 — Other (74 ) (37 ) (256 ) Valuation allowance 11,121 3,887 10,378 Income tax expense $ — $ — $ —
Summary of significant components of the Company's deferred tax assets	Significant components of the Company’s deferred tax assets are summarized as follows (in thousands): As of December 31, 2016 2015 Deferred tax assets: Section 59e amortization $ 17,699 $ 13,042 Net operating losses 35,049 28,963 R&D tax credits 2,175 1,274 Depreciation and amortization 1,020 921 Deferred revenue 1,677 2,494 Stock compensation 1,222 1,109 Other (76 ) (159 ) Deferred tax assets 58,766 47,644 Valuation allowance (58,766 ) (47,644 ) Net deferred tax assets $ — $ —
Summary of the change in the Company's unrecognized tax benefits	The change in the Company’s unrecognized tax benefits is summarized as follows (in thousands): Balance at December 31, 2013 $ 1,329 Increase related to current year tax positions 491 Balance at December 31, 2014 $ 1,820 Increase related to current year tax positions 374 Increase related to prior year tax positions 2,624 Decrease related to prior year tax positions (949 ) Balance at December 31, 2015 $ 3,869 Increase related to current year tax positions 2,268 Increase related to prior year tax positions 1,625 Decrease related to prior year tax positions (32 ) Balance at December 31, 2016 $ 7,730

Selected Quarterly Financial 23

Selected Quarterly Financial Data (Tables)	12 Months Ended
	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of selected quarterly financial data	(in thousands, except per share data) (unaudited) First Quarter Second Quarter Third Quarter Fourth Quarter 2016 Revenues $ 1,322 $ 1,027 $ 1,026 $ 1,027 Total operating expenses 9,238 9,031 9,415 8,681 Net loss (8,377 ) (8,408 ) (8,737 ) (7,940 ) Basic and diluted net loss per common share $ (0.29 ) $ (0.29 ) $ (0.27 ) $ (0.21 ) 2015 Revenues $ — $ 329 $ 1,026 $ 1,076 Total operating expenses 7,324 7,547 7,354 7,988 Net loss (7,881 ) (7,779 ) (6,886 ) (7,446 ) Basic and diluted net loss per common share $ (0.38 ) $ (0.33 ) $ (0.24 ) $ (0.26 )

Organization and Summary of S24

Organization and Summary of Significant Accounting Policies (Details) $ / shares in Units, $ in Thousands	1 Months Ended			12 Months Ended
	Nov. 30, 2016USD ($)$ / sharesshares	Aug. 31, 2016USD ($)$ / sharesshares	May 31, 2015USD ($)$ / sharesshares	Dec. 31, 2016USD ($)item	Dec. 31, 2015USD ($)shares	Dec. 31, 2014USD ($)
Equity transactions
Gross proceeds from issuance of shares					$ 4,580
Net proceeds from issuance of shares after related cash costs				$ 186	$ 420	$ 142
Segment Reporting
Number of operating segments | item				1
Common Stock
Equity transactions
Shares sold | shares					6,900,000
Follow on public equity offering
Equity transactions
Shares sold | shares			6,900,000
Share issue price (in dollars per share) | $ / shares			$ 5
Gross proceeds from issuance of shares			$ 34,500
Net proceeds from issuance of shares after related cash costs			2,400
Financing And Stock Issuance Costs			$ 32,100
Private Placement | Non-Voting Class A Preferred Stock
Equity transactions
Share issue price (in dollars per share) | $ / shares	$ 13.30
Preferred stock, issued shares | shares	2,819,549
Preferred stock convertible into common stock, shares | shares	5
Private Placement | Common Stock
Equity transactions
Shares sold | shares	7,236,837	5,250,000
Share issue price (in dollars per share) | $ / shares	$ 2.66	$ 1.96
Gross proceeds from issuance of shares		$ 10,300
Net proceeds from issuance of shares after related cash costs	$ 55,000	$ 10,200
Gross proceeds from issuance of shares	$ 56,700

Organization and Summary of S25

Organization and Summary of Significant Accounting Policies (Details 2) - Fair Value Measurements Recurring - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 88,609	$ 35,257
Total assets	92,112	35,257
U.S. Treasury debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasury debt securities	3,503
Quoted prices in Active Market for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	88,609	35,257
Total assets	92,112	$ 35,257
Quoted prices in Active Market for Identical Assets (Level 1) | U.S. Treasury debt securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasury debt securities	$ 3,503

Organization and Summary of S26

Organization and Summary of Significant Accounting Policies (Details 3) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfer of assets from level 1 to level 2	$ 0
Transfer of assets from level 2 to level 1	0
Transfer of liabilities from level 1 to level 2	0
Transfer of liabilities from level 2 to level 1	0
Fair Value Measurements Nonrecurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Non-financial assets	0
Non-financial liabilities	0
Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Liabilities measured at fair value	$ 0	$ 0

Organization and Summary of S27

Organization and Summary of Significant Accounting Policies (Details 4)	12 Months Ended
	Dec. 31, 2016
Furniture And Fixtures | Minimum
Property and equipment
Estimated useful lives	2 years
Furniture And Fixtures | Maximum
Property and equipment
Estimated useful lives	5 years
Computer Equipment | Minimum
Property and equipment
Estimated useful lives	2 years
Computer Equipment | Maximum
Property and equipment
Estimated useful lives	5 years
Scientific Equipment | Minimum
Property and equipment
Estimated useful lives	2 years
Scientific Equipment | Maximum
Property and equipment
Estimated useful lives	5 years
Office Equipment | Minimum
Property and equipment
Estimated useful lives	2 years
Office Equipment | Maximum
Property and equipment
Estimated useful lives	5 years

Organization and Summary of S28

Organization and Summary of Significant Accounting Policies (Details 5) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue Recognition [Abstract]
Four criteria needed for Company to recognize revenue	(i) persuasive evidence that an agreement exists; (ii) delivery of the products and/or services has occurred; (iii) the selling price is fixed or determinable; and (iv) collectability is reasonably assured.
Uncertain tax position description	more than 50 percent
Anti-dilutive securities (in shares)	18,667,458	3,246,837	2,560,082
Series A Convertible Preferred Stock (if converted)
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	14,097,745
Employee Stock Option
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	3,284	44,381	76,947
Warrants For Common Stock
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	134,113	134,113	134,113
Stock Compensation Plan
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	3,910,350	2,587,474	2,425,969
Restricted Stock Units (RSUs)
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	525,250	525,250

Juno Collaboration and Licens29

Juno Collaboration and License Agreement (Details) - USD ($)	May 04, 2015	Dec. 31, 2016	Dec. 31, 2015
Collaboration agreement
Issuance of common stock			$ 4,580,000
Juno Therapeutics, Inc
Collaboration agreement
Common stock issued	1,000,000
Research term	4 years
Minimum annual research payments receivable	$ 2,000,000
Extended term of research	2 years
Extension fee	$ 3,000,000
Minimum annual payments receivable for extended term of research	$ 4,000,000
Common stock premium percentage on trading price upon exercise of extension	120.00%
Trailing trading period considered for premium	30 days
Upfront payments recorded as deferred revenue	$ 5,000,000
Recognition period of deferred revenue	4 years
Proceeds from sale of common stock	$ 8,000,000
Premium on share price (in dollars per share)	$ 3.40
Aggregate premium on shares issued recorded as deferred revenue	$ 3,400,000
Issuance of common stock	$ 4,600,000
Term of royalties payable after first commercial sale	10 years
Juno Therapeutics, Inc | Maximum
Collaboration agreement
Common stock issued upon exercise of extension	$ 10,000,000
Aggregate milestone payments	51,000,000
Juno Therapeutics, Inc | Maximum | Third Juno Product
Collaboration agreement
Additional aggregate milestone payments	116,000,000
Juno Therapeutics, Inc | Maximum | Fifth Juno Product
Collaboration agreement
Additional aggregate milestone payments	137,500,000
Juno Therapeutics, Inc | Collaborative Arrangement
Collaboration agreement
Proceeds from non refundable upfront fee	$ 5,000,000
Share Price	$ 8
Revenue recognized		$ 4,400,000	$ 2,400,000
Aggregate deferred revenue		$ 4,900,000

Short-term Investments (Details

Short-term Investments (Details)	12 Months Ended
	Dec. 31, 2016USD ($)
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, impairment	$ 0
Available-for-sale securities, gains (losses) on sales	$ 0
U.S. Treasury debt securities
Schedule Of Available For Sale Securities [Line Items]
Short term investments, maturity start range	6 months
Short term investments, maturity end range	12 months

Short-term Investments (Detai31

Short-term Investments (Details 2) $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 3,504
Unrealized Losses	(1)
Estimated Fair Value	$ 3,503
U.S. Treasury debt securities
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	1 or less
Amortized Cost	$ 3,504
Unrealized Losses	(1)
Estimated Fair Value	$ 3,503

Property and Equipment (Details

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and equipment
Property and equipment, gross	$ 5,783	$ 5,632
Less accumulated depreciation and amortization	(4,204)	(3,472)
Property, Plant and Equipment, Net	1,579	2,160
Depreciation expense	881	687	$ 496
Furniture And Fixtures
Property and equipment
Property and equipment, gross	324	324
Computer And Office Equipment
Property and equipment
Property and equipment, gross	318	300
Software And Software Development Costs
Property and equipment
Property and equipment, gross	103	103
Leasehold Improvements
Property and equipment
Property and equipment, gross	180	180
Scientific Equipment
Property and equipment
Property and equipment, gross	$ 4,858	$ 4,725

Accrued Expenses, Long-Term D33

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current accrued expenses
Accrued payroll and other employee benefits	$ 1,505	$ 993
Accrued clinical trial related costs	1,043	446
Accrued other	1,409	1,000
Accrued expenses	$ 3,957	$ 2,439

Accrued Expenses, Long-Term D34

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details 2)	Dec. 24, 2014USD ($)$ / sharesshares	Jul. 30, 2014USD ($)	Jun. 30, 2016USD ($)ft²	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Current accrued expenses
Common stock issued to senior executives | shares				37,641
Principal payment on long-term debt				$ 7,689,000	$ 1,546,000	$ 1,750,000
Net Proceeds after repayment of loans outstanding and transaction fees						20,000,000
Loss on extinguishment of debt						(432,000)
Aggregate interest expense				1,600,000	2,200,000	500,000
Cash-collateralized irrevocable standby letter of credit			$ 100,000
Future minimum payments				14,165,000
Rent expense				1,300,000	1,200,000	900,000
Minimum annual payments to maintain cancelable licenses				300,000
Non-Cancelable Operating Lease
Current accrued expenses
Lease expiration period			2023-06
Additional leased space | ft²			24,000
Future minimum payments				13,900,000
Sublease Lease
Current accrued expenses
Future minimum payments				$ 200,000
Sublease expiration date				2017-09
Warrants Expiration Period January 2019
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion | shares				5,305
Warrants expiration date				2019-01
Warrants Expiration Period August 2021
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion | shares				30,769
Warrants expiration date				2021-08
Warrant
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion | shares				36,074
Exercise price (in dollars per share) | $ / shares				$ 7.21
Term A Loan
Current accrued expenses
Effective interest rate				10.30%
Term B Loan
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion | shares	98,039
Warrants expiration date				2021-12
Effective interest rate				12.00%
Term B Loan | Warrant
Current accrued expenses
Exercise price (in dollars per share) | $ / shares	$ 4.08			$ 4.08
Fair values of warrants issued	$ 400,000			$ 400,000
Amended And Restated Loan And Security Agreement
Current accrued expenses
Commitment fee		$ 400,000
Aggregate interest expense						100,000
Amended And Restated Loan And Security Agreement | Maximum
Current accrued expenses
Principal amount		20,000,000
Amended And Restated Loan And Security Agreement | Term A Loan
Current accrued expenses
Principal amount		$ 10,000,000
Debt instrument, maturity date				Jan. 1, 2018
Interest rate (as a percent)		6.94%
Principal payment on long-term debt				$ 3,900,000	$ 1,500,000
Final payment fee (amounts in dollars)				$ 800,000
Final payment fee				7.50%
Net Proceeds after repayment of loans outstanding and transaction fees		$ 8,800,000
Loss on extinguishment of debt						$ (400,000)
Amended And Restated Loan And Security Agreement | Term B Loan
Current accrued expenses
Debt instrument, maturity date				Jun. 1, 2018
Interest rate (as a percent)		7.07%
Principal payment on long-term debt				$ 3,800,000
Final payment fee (amounts in dollars)				$ 800,000
Final payment fee				7.50%
Net Proceeds after repayment of loans outstanding and transaction fees				$ 10,000,000
Warrants to purchase shares of common stock issued on conversion | shares				98,039
Amended And Restated Loan And Security Agreement | Term B Loan | Maximum
Current accrued expenses
Principal amount		$ 10,000,000
Amended And Restated Loan And Security Agreement | Term B Loan Tranche 1 | Minimum
Current accrued expenses
Principal amount	$ 10,000,000
Amended And Restated Loan And Security Agreement | Secured Debt
Current accrued expenses
Number of monthly payment of interest		12 months
Number of equal monthly installments to repay principal and accrued interest		30 months

Accrued Expenses, Long-Term D35

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details 3) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Debt Disclosure [Abstract]
Long-term debt	$ 10,765	$ 18,454
Less debt issuance costs and discount, net of current portion	(7)	(77)
Long-term debt, net of long-term portion of debt issuance costs and discount	10,758	18,377
Less current portion of long-term debt	(8,257)	(7,689)
Long-term debt, net	2,501	10,688
Current portion of long-term debt	8,257	7,689
Less current portion of debt issuance costs and discount	(70)	(139)
Current portion of long-term debt, net	$ 8,187	$ 7,550

Accrued Expenses, Long-Term D36

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details 4) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Long-Term Debt
Years Ending December 31, 2017	$ 8,757
Years Ending December 31, 2018	4,055
Long-term debt	12,812
Less interest	(547)
Less additional payments due upon maturity	(1,500)
Less unamortized debt discount and debt issuance costs	(77)
Less current portion of long–term debt	(8,187)	$ (7,550)
Long–term debt, net of current portion	2,501	$ 10,688
Operating Leases
Years Ending December 31, 2017	1,237
Years Ending December 31, 2018	2,116
Years Ending December 31, 2019	2,278
Years Ending December 31, 2020	2,346
Years Ending December 31, 2021	2,417
Years Ending December 31, 2022	2,489
Years Ending December 31, 2023	1,282
Total	14,165
Total
Years Ending December 31, 2017	9,994
Years Ending December 31, 2018	6,171
Years Ending December 31, 2019	2,278
Years Ending December 31, 2020	2,346
Years Ending December 31, 2021	2,417
Years Ending December 31, 2022	2,489
Years Ending December 31, 2023	1,282
Total	$ 26,977

Convertible Preferred Stock a37

Convertible Preferred Stock and Stockholders' Equity (Details) - USD ($)	1 Months Ended		12 Months Ended
	Nov. 30, 2016	Aug. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Convertible preferred stock
Net proceeds from issuance of shares after related cash costs			$ 186,000	$ 420,000	$ 142,000
Preferred stock, par value (in dollars per share)			$ 0.001	$ 0.001
Dividends declared			$ 0
Common Stock
Convertible preferred stock
Public offering of common stock, net of offering costs (in shares)				6,900,000
Non-Voting Class A Preferred Stock
Convertible preferred stock
Preferred stock, par value (in dollars per share)	$ 0.001
Conversion price	2.66
Non-Voting Class A Preferred Stock | Redmile Group, LLC and Affiliates
Convertible preferred stock
Terms of conversion			The Class A Preferred were purchased exclusively by entities affiliated with Redmile Group, LLC (collectively, “Redmile”). Redmile is prohibited from converting the Class A Preferred into shares of the Company’s common stock if, as a result of conversion, Redmile, together with its affiliates, would own more than 9.99% of the Company’s common stock then issued and outstanding (the “Redmile Percentage Limitation”), which percentage may change at Redmile’s election upon 61 days’ notice to the Company to i) any other number less than or equal to 19.99% or (ii) subject to approval of the Company’s stockholders to the extent required in accordance with the NASDAQ Global Market rules, any number in excess of 19.99%.
Non-Voting Class A Preferred Stock | Maximum | Redmile Group, LLC and Affiliates
Convertible preferred stock
Percentage of common stock ownership upon preferred stock conversion			9.99%
Preferred shares converted into common stock percentage of ownership change upon notice			19.99%
Private Placement | Common Stock
Convertible preferred stock
Share issue price (in dollars per share)	$ 2.66	$ 1.96
Public offering of common stock, net of offering costs (in shares)	7,236,837	5,250,000
Net proceeds from issuance of shares after related cash costs	$ 55,000,000	$ 10,200,000
Gross proceeds from issuance of shares	$ 56,700,000
Private Placement | Non-Voting Class A Preferred Stock
Convertible preferred stock
Preferred stock, issued shares	2,819,549
Share issue price (in dollars per share)	$ 13.30
Number of shares to be issued upon conversion	5

Convertible Preferred Stock a38

Convertible Preferred Stock and Stockholders' Equity (Details 2) - USD ($) $ / shares in Units, $ in Thousands	Dec. 24, 2014	Sep. 13, 2013	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2016	May 10, 2016	Aug. 31, 2013	Aug. 28, 2013
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance			20,456,523	4,884,125			20,456,523
Stock purchases under the plan (in shares)							0
Aggregate Intrinsic Value
Total stock-based compensation expense			$ 3,184	$ 2,400	$ 2,434
Convertible Preferred Stock (if converted)
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance			14,097,745				14,097,745
Warrant
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance			134,113	134,113			134,113
Risk-free interest rate (as a percent)	2.10%
Expected volatility (as a percent)	85.00%
Expected term (in years)	7 years
Expected dividend yield (as a percent)	0.00%
Warrants to purchase shares of common stock issued on conversion			36,074
Exercise price (in dollars per share)			$ 7.21				$ 7.21
Term B Loan
Weighted-average assumptions to determine fair value of stock options
Warrants to purchase shares of common stock issued on conversion	98,039
Term B Loan | Warrant
Weighted-average assumptions to determine fair value of stock options
Exercise price (in dollars per share)	$ 4.08		$ 4.08				$ 4.08
Fair values of warrants issued	$ 400		$ 400				$ 400
Research And Development
Aggregate Intrinsic Value
Total stock-based compensation expense			1,802	$ 1,241	1,416
General And Administrative
Aggregate Intrinsic Value
Total stock-based compensation expense			1,382	$ 1,159	$ 1,018
Employee And Non Employee Stock Option
Aggregate Intrinsic Value
Total intrinsic value of stock options exercised			100
Cash received upon exercise of options (in dollars per share)			$ 200
Employee Stock
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance		729,000	729,000	729,000			729,000
Additional shares authorized (as a percent)		2.00%
Additional shares authorized		450,000
Employee Stock Option
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance			3,910,350	2,587,474			3,910,350
Risk-free interest rate (as a percent)			1.60%	1.60%	1.90%
Expected volatility (as a percent)			80.00%	81.00%	94.00%
Expected term (in years)			6 years	6 years	6 years
Expected dividend yield (as a percent)			0.00%	0.00%	0.00%
Estimated pre-vesting forfeitures percentage			0.00%	0.00%	0.00%
Restricted Stock Units (RSUs)
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance			525,250	525,250			525,250
Aggregate Intrinsic Value
Expected recognition period of unrecognized compensation cost			2 years 9 months 18 days	3 years 9 months 18 days
Unrecognized compensation cost related to unvested restricted shares			$ 1,800	$ 2,400			$ 1,800
Granted (in shares)			0	500,000
Weighted-average grant date fair value per share of employee other than options granted (in dollars per share)				$ 4.90
Canceled (in shares)			0
Vested (in shares)			0
Non Employee Stock Option
Weighted-average assumptions to determine fair value of stock options
Risk-free interest rate (as a percent)			1.50%	0.80%	2.10%
Expected volatility (as a percent)			83.00%	72.00%	87.00%
Expected term (in years)			6 years 4 months 24 days	2 years 8 months 12 days	6 years 6 months
Expected dividend yield (as a percent)			0.00%	0.00%	0.00%
Stock Compensation Plan
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance			760,065	908,288			760,065
Equity Incentive Plan 2007
Stockholders' Equity
Shares authorized									2,423,072
Stock Option And Incentive Plan 2013
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance										1,020,000
Additional shares authorized (as a percent)										4.00%
Stock Option And Incentive Plan 2013 | Restricted Stock | Second Year Anniversary Vesting Date
Weighted-average assumptions to determine fair value of stock options
Stock options generally vested on anniversary grant date (as a percent)			50.00%
Stock Option And Incentive Plan 2013 | Restricted Stock | Fourth Year Anniversary Vesting Date
Weighted-average assumptions to determine fair value of stock options
Stock options generally vested on anniversary grant date (as a percent)			50.00%
Stock Option And Incentive Plan 2007 And 2013 | Employee And Non Employee Stock Option
Weighted-average assumptions to determine fair value of stock options
Stock options generally vested on anniversary grant date (as a percent)			25.00%
General vesting period after first year			3 years
Monthly vesting period			4 years
Number of Options
Balance at the beginning of the period (in shares)			2,587,474	2,425,969	1,726,991
Granted (in shares)			2,245,240	1,345,744	885,624
Exercised (in shares)			(136,368)	(227,215)	(96,856)
Cancelled (in shares)			(785,996)	(957,024)	(89,790)
Balance at the end of the period (in shares)			3,910,350	2,587,474	2,425,969	1,726,991	3,910,350
Vested and expected to vest at the end of the period (in shares)			3,785,029				3,785,029
Exercisable at the end of the period (in shares)			1,469,829				1,469,829
Weighted-Average Price
Balance at the beginning of the period (in dollars per share)			$ 4.59	$ 3.83	$ 2.30
Granted (in dollars per share)			2.62	5.23	6.62
Exercised (in dollars per share)			1.44	1.85	1.65
Cancelled (in dollars per share)			3.58	4.20	4.38
Balance at the end of the period (in dollars per share)			3.77	$ 4.59	$ 3.83	$ 2.30	$ 3.77
Vested and expected to vest at the end of the period (in dollars per share)			3.78				3.78
Exercisable at the end of the period (in dollars per share)			$ 4.61				$ 4.61
Weighted Average Remaining Contractual Term
Outstanding at the end of the period			8 years 3 months 11 days	6 years 11 months 1 day	8 years 22 days	8 years 5 months 19 days
Vested and expected to vest at the end of the period			8 years 3 months 29 days
Exercisable at the end of the period			7 years 4 months 21 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)			$ 682	$ 1,486	$ 4,839	$ 7,203	$ 682
Vested and expected to vest at the end of the period (in dollars)			679				679
Exercisable at the end of the period (in dollars)			231				231
Unrecognized compensation cost related to outstanding options			$ 4,900	$ 3,800	$ 4,100		$ 4,900
Expected recognition period of unrecognized compensation cost			2 years 7 months 6 days	2 years 9 months 18 days	2 years 7 months 6 days
Granted (in shares)			2,245,240	1,345,744	885,624
Stock Option And Incentive Plan 2007 And 2013 | Employee And Non Employee Stock Option | Vesting Based On Performance
Number of Options
Balance at the beginning of the period (in shares)			14,769	138,649
Balance at the end of the period (in shares)			73,600	14,769	138,649		73,600
Aggregate Intrinsic Value
Aggregate grant date fair value			$ 100	$ 100	$ 600
Stock Option And Incentive Plan 2007 And 2013 | Employee And Non Employee Stock Option | Maximum
Weighted-average assumptions to determine fair value of stock options
Term of stock awards			10 years
Stock Option And Incentive Plan 2007 And 2013 | Employee Stock Option
Number of Options
Granted (in shares)			2,200,000	1,200,000	900,000
Aggregate Intrinsic Value
Granted (in shares)			2,200,000	1,200,000	900,000
Weighted-average grant date fair value per share of employee options granted (in dollars per share)			$ 1.80	$ 3.54	$ 5.10
Inducement Plan
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance			300,000				300,000	500,000

Income Taxes (Details)

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of the Company's expected federal income tax provision (benefit) to the actual income tax provision
Tax computed at federal statutory rate	$ (11,377)	$ (10,198)	$ (8,800)
State tax, net of federal tax benefit	(2,089)	2,226	(1,311)
Permanent differences	292	43	159
Stock compensation	968	213	426
R&D tax credits	(971)	(594)	(596)
Reserve for uncertain tax positions	2,076	1,733
Tax attribute limitation	54	2,727
Other	(74)	(37)	(256)
Valuation allowance	11,121	3,887	$ 10,378
Deferred tax assets:
Section 59e amortization	17,699	13,042
Net operating losses	35,049	28,963
R&D tax credits	2,175	1,274
Depreciation and amortization	1,020	921
Deferred revenue	1,677	2,494
Stock compensation	1,222	1,109
Other	(76)	(159)
Deferred tax assets	58,766	47,644
Valuation allowance	$ (58,766)	$ (47,644)

Income Taxes (Details 2)

Income Taxes (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 58,766	$ 47,644
U.S. Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 97,900
Net operating loss carryforward expiration year	2,027
California
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 98,000
Net operating loss carryforward expiration year	2,028

Income Taxes (Details 3)

Income Taxes (Details 3) - Research and development $ in Millions	12 Months Ended
	Dec. 31, 2016USD ($)
U.S. Federal
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 1.4
Tax credit carryforward expiration year	2,035
California
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 3.4

Income Taxes (Details 4)

Income Taxes (Details 4) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Change in the Company's unrecognized tax benefits
Balance at the beginning of the period	$ 3,869,000	$ 1,820,000	$ 1,329,000
Increase related to current year tax positions	2,268,000	374,000	491,000
Increase related to prior year tax positions	1,625,000	2,624,000
Decrease related to prior year tax positions	(32,000)	(949,000)
Balance at the end of the period	7,730,000	$ 3,869,000	$ 1,820,000
Income Taxes
Unrecognized tax benefit	0
Unrecognized tax benefits that, if recognized, would reduce the effective tax rate	$ 0

Income Taxes (Details 5)

Income Taxes (Details 5) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Income Tax Contingency [Line Items]
Excess tax benefit previously not recognized	$ 7,730	$ 3,869	$ 1,820	$ 1,329
ASU No. 2016-09
Income Tax Contingency [Line Items]
Excess tax benefit previously not recognized	$ 100

Employee Benefits (Details)

Employee Benefits (Details) - USD ($)	Jan. 02, 2009	Dec. 31, 2016
Compensation And Retirement Disclosure [Abstract]
Minimum age of employees	21 years
Matching contributions under 401(k) plan		$ 0

Selected Quarterly Financial 45

Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 1,027	$ 1,026	$ 1,027	$ 1,322	$ 1,076	$ 1,026	$ 329
Total operating expenses	8,681	9,415	9,031	9,238	7,988	7,354	7,547	$ 7,324	$ 36,365	$ 30,213	$ 24,904
Net loss	$ (7,940)	$ (8,737)	$ (8,408)	$ (8,377)	$ (7,446)	$ (6,886)	$ (7,779)	$ (7,881)	$ (33,462)	$ (29,992)	$ (25,883)
Basic and diluted net loss per common share (in dollars per share)	$ (0.21)	$ (0.27)	$ (0.29)	$ (0.29)	$ (0.26)	$ (0.24)	$ (0.33)	$ (0.38)	$ (1.05)	$ (1.18)	$ (1.27)