Document and Entity Information - USD ($)	12 Months Ended
Document and Entity Information - USD ($)	Dec. 31, 2018	Mar. 01, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Entity Registrant Name	FATE THERAPEUTICS INC
Entity Central Index Key	0001434316
Document Type	10-K
Document Period End Date	Dec. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Shell Company	false
Entity Small Business	true
Entity Emerging Growth Company	false
Trading Symbol	FATE
Entity Public Float			$ 488,652,000
Entity Common Stock, Shares Outstanding		64,999,547
Document Fiscal Year Focus	2018
Document Fiscal Period Focus	FY

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 190,514	$ 88,952
Accounts receivable	500
Short-term investments and related maturity receivables	10,493	11,997
Prepaid expenses and other current assets	3,689	1,647
Total current assets	205,196	102,596
Property and equipment, net	5,125	2,550
Restricted cash	227	122
Collaboration contract asset	1,958
Other assets	526	24
Total assets	213,032	105,292
Current liabilities:
Accounts payable	4,205	1,678
Accrued expenses	10,926	7,254
Current portion of CIRM award liability	2,106
Current portion of deferred rent		12
Current portion of deferred revenue	7,588	2,105
Long–term debt, current portion	2,438
Total current liabilities	27,263	11,049
Deferred rent	3,401	1,347
Deferred revenue	7,500	724
Accrued expenses	549	175
CIRM award liability, net of current portion	1,404
Long–term debt, net of current portion	12,446	14,808
Commitments and contingencies (Note 6)
Stockholders’ Equity:
Preferred stock, $0.001 par value; authorized shares—5,000,000 at December 31, 2018 and December 31, 2017; 2,819,549 Class A convertible preferred shares issued and outstanding at December 31, 2018 and December 31, 2017	3	3
Common stock, $0.001 par value; authorized shares—150,000,000 at December 31, 2018 and December 31, 2017; issued and outstanding—64,693,681 at December 31, 2018 and 52,648,601 at December 31, 2017	65	53
Additional paid–in capital	445,799	295,934
Accumulated other comprehensive loss	(2)	(3)
Accumulated deficit	(285,396)	(218,798)
Total stockholders’ equity	160,469	77,189
Total liabilities and stockholders’ equity	$ 213,032	$ 105,292

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2018	Dec. 31, 2017
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	64,693,681	52,648,601
Common stock, outstanding shares	64,693,681	52,648,601
Class A Convertible Preferred Shares
Preferred stock, issued shares	2,819,549	2,819,549
Preferred stock, outstanding shares	2,819,549	2,819,549

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Collaboration revenue	$ 4,740	$ 4,106	$ 4,402
Type of Revenue [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember
Operating expenses:
Research and development	$ 56,024	$ 34,358	$ 26,452
General and administrative	15,808	11,873	9,913
Total operating expenses	71,832	46,231	36,365
Loss from operations	(67,092)	(42,125)	(31,963)
Other income (expense):
Interest income	2,190	559	138
Interest expense	(1,696)	(1,268)	(1,637)
Loss on extinguishment of debt		(118)
Total other income (expense), net	494	(827)	(1,499)
Net loss	(66,598)	(42,952)	(33,462)
Other comprehensive income (loss):
Unrealized gain (loss) on available-for-sale securities, net	1	(2)	(1)
Comprehensive loss	$ (66,597)	$ (42,954)	$ (33,463)
Net loss per common share, basic and diluted	$ (1.19)	$ (1.02)	$ (1.05)
Weighted-average common shares used to compute basic and diluted net loss per share	56,195,650	41,982,167	31,754,140

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, 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
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 gain (loss) on short-terminvestments	(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
Exercise of stock options, net of issuance costs	226		226
Exercise of stock options, net of issuance costs (in shares)		83,220
Issuance of common stock upon vesting of restricted stock units		$ 1	(1)
Issuance of common stock upon vesting of restricted stock units (in shares)		225,125
Stock–based compensation	3,606		3,606
Issuance of warrants for common stock	217		217
Public offerings of common stock, net of offering costs	42,979	$ 11	42,968
Public offerings of common stock, net of offering costs (in shares)		10,953,750
Private placement issuances of common stock, net of offering costs	(13)		(13)
Private placement issuance of Series A convertible preferred stock, net of offering costs	(26)		(26)
Unrealized gain (loss) on short-terminvestments	(2)			(2)
Net loss	(42,952)				(42,952)
Balance at Dec. 31, 2017	77,189	$ 53	295,934	(3)	(218,798)	$ 3
Balance (in shares) at Dec. 31, 2017		52,648,601				2,819,549
Exercise of stock options, net of issuance costs	2,693	$ 1	2,692
Exercise of stock options, net of issuance costs (in shares)		694,830
Issuance of common stock upon cashless warrant exercises (in shares)		102,101
Stock–based compensation	6,293		6,293
Issuance of common stock for license agreements	6,100		6,100
Issuance of common stock for license agreements (in shares)		600,000
Public offerings of common stock, net of offering costs	134,791	$ 11	134,780
Public offerings of common stock, net of offering costs (in shares)		10,648,149
Unrealized gain (loss) on short-terminvestments	1			1
Net loss	(66,598)				(66,598)
Balance at Dec. 31, 2018	$ 160,469	$ 65	$ 445,799	$ (2)	$ (285,396)	$ 3
Balance (in shares) at Dec. 31, 2018		64,693,681				2,819,549

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities
Net loss	$ (66,598)	$ (42,952)	$ (33,462)
Adjustments to reconcile net loss to net cash used in operating activities
Depreciation and amortization	1,204	971	881
Stock–based compensation	6,293	3,606	3,184
Amortization of debt discounts and debt issuance costs	76	81	139
Amortization of premiums and discounts on investments, net	(335)	(25)	171
Amortization of collaboration contract asset	42
Noncash interest expense	373	321	492
Deferred rent	192	1,085	(7)
Deferred revenue	12,259	(2,105)	(2,401)
Issuance of common stock for license agreements	6,100
Cash payments included in loss on extinguishment of debt		88
Non-cash loss on extinguishment of debt		30
Changes in assets and liabilities:
Accounts receivable	(500)
Prepaid expenses and other assets	(2,010)	(428)	(381)
Accounts payable and accrued expenses	4,254	2,511	1,561
Net cash used in operating activities	(38,650)	(36,817)	(29,823)
Cash flows from investing activities
Proceeds from sale of property and equipment			18
Purchase of property and equipment	(2,303)	(1,725)	(457)
Purchases of short-term investments	(55,660)	(39,971)	(19,675)
Maturities of short-term investments	57,500	31,500	16,000
Net cash used in investing activities	(463)	(10,196)	(4,114)
Cash flows from financing activities
Issuance of common stock from equity incentive plans, net of repurchases and issuance costs	2,693	205	186
Proceeds from public offerings of common stock, net of issuance costs	134,577	43,206
Proceeds from CIRM award	3,510
Proceeds from long–term debt		15,000
Payments on long–term debt		(10,764)	(7,689)
Cash payments included in loss on extinguishment of debt		(88)
Payments of debt issuance costs		(10)
Net cash provided by financing activities	140,780	47,356	57,737
Net change in cash, cash equivalents and restricted cash	101,667	343	23,800
Cash, cash equivalents and restricted cash at beginning of the period	89,074	88,731	64,931
Cash, cash equivalents and restricted cash at end of the period	190,741	89,074	88,731
Supplemental disclosure of cash flow information
Interest paid	$ 1,242	2,314	1,067
Supplemental schedule of noncash investing and financing activities
Issuance of warrants for common stock in connection with long–term debt		217
Common Stock
Cash flows from financing activities
Proceeds from private placement issuances of stock, net of issuance costs		(65)	28,849
Preferred Stock
Cash flows from financing activities
Proceeds from private placement issuances of stock, net of issuance costs		$ (128)	$ 36,391

Organization and Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2018

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 cell therapy pipeline is comprised of NK- and T-cell immuno-oncology programs, including off-the-shelf engineered product candidates derived from clonal master iPSC lines, and immuno-regulatory programs, including product candidates to prevent life-threatening complications in patients undergoing hematopoietic cell transplantation and to induce immune tolerance in patients with autoimmune disease. Its adoptive cell therapy programs are based on the Company’s novel ex vivo cell programming approach, which it applies to modulate the therapeutic function and direct the fate of immune cells.

As of December 31, 2018, 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.

Public Equity Offerings

In September 2018, the Company completed a public offering of common stock in which investors, including investors affiliated with the directors of the Company, purchased 10,648,149 shares of its common stock at a price of $13.50 per share under a shelf registration statement. Gross proceeds from the offering were $143.8 million, and, after giving effect to $8.9 million of costs related to the offering, net proceeds were $134.9 million.

In December 2017, the Company completed a public offering of common stock in which investors purchased 10,953,750 shares of its common stock at a price of $4.20 per share under a shelf registration statement. Gross proceeds from the offering were $46.0 million, and after giving effect to $3.0 million of costs related to the offering (of which $0.3 million was paid during the year ended December 31, 2018), net proceeds were $43.0 million.

Private Placements of Common Stock and Convertible Preferred Stock

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 $54.9 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 7 to the Consolidated Financial Statements for additional information related to this offering.

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.

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 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 and reportable 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, 2018 and 2017 (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, 2018:
Cash equivalents	$	190,514	$	190,514	$	—	$	—
U.S. Treasury debt securities		10,493		10,493		—		—
Total assets measured at fair value on a recurring basis	$	201,007	$	201,007	$	—	$	—

As of December 31, 2017:
Cash equivalents	$	88,952	$	88,952	$	—	$	—
U.S. Treasury debt securities		11,997		11,997		—		—
Total assets measured at fair value on a recurring basis	$	100,949	$	100,949	$	—	$	—

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, 2018 and 2017, the Company had no material liabilities measured at fair value on a recurring basis.

Cash, Cash Equivalents and Restricted Cash

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.

The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the Consolidated Balance Sheets that sum to the total of the same such amounts shown in the Consolidated Statements of Cash Flows as of December 31, 2018, 2017 and 2016 (in thousands):

	December 31, 2018		December 31, 2017		December 31, 2016
Cash and cash equivalents	$	190,514	$	88,952	$	88,609
Restricted cash		227		122		122
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$	190,741	$	89,074	$	88,731

Amounts included in restricted cash represent security deposits required to secure the Company’s credit card limit and its facilities lease.

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 a significant concentration of credit risk, consist primarily of cash and 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, scientific and office equipment, and in-process costs related to facilities construction. 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. If the carrying amount is not recoverable, the Company measures the amount of any impairment by comparing the carrying value of the asset to the present value of the expected future cash flows associated with the use of the asset. 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, lease incentives, and the recognition of rent expense on a straight-line basis for the facilities the Company occupies. The Company’s lease for its facilities provides for fixed increases in minimum annual rental payments. The total amount of rental payments due over the lease term are charged to rent expense ratably over the life of the lease.

Revenue Recognition

The Company recognizes revenue in a manner that depicts the transfer of control of a product or a service to a customer and reflects the amount of the consideration the Company is entitled to receive in exchange for such product or service. In doing so, the Company follows a five-step approach: (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 when (or as) the customer obtains control of the product or service. The Company considers the terms of a contract and all relevant facts and circumstances when applying the revenue recognition standard. The Company applies the revenue recognition standard, including the use of any practical expedients, consistently to contracts with similar characteristics and in similar circumstances.

A customer is a party that has entered into a contract with the Company, where the purpose of the contract is to obtain a product or a service that is an output of the Company’s ordinary activities in exchange for consideration. To be considered a contract, (i) the contract must be approved (in writing, orally, or in accordance with other customary business practices), (ii) each party’s rights regarding the product or the service to be transferred can be identified, (iii) the payment terms for the product or the service to be transferred can be identified, (iv) the contract must have commercial substance (that is, the risk, timing or amount of future cash flows is expected to change as a result of the contract), and (v) it is probable that the Company will collect substantially all of the consideration to which it is entitled to receive in exchange for the transfer of the product or the service.

A performance obligation is defined as a promise to transfer a product or a service to a customer. The Company identifies each promise to transfer a product or a service (or a bundle of products or services, or a series of products and services that are substantially the same and have the same pattern of transfer) that is distinct. A product or a service is distinct if both (i) the customer can benefit from the product or the service either on its own or together with other resources that are readily available to the customer and (ii) the Company’s promise to transfer the product or the service to the customer is separately identifiable from other promises in the contract. Each distinct promise to transfer a product or a service is a unit of accounting for revenue recognition. If a promise to transfer a product or a service is not separately identifiable from other promises in the contract, such promises should be combined into a single performance obligation.

The transaction price is the amount of consideration the Company is entitled to receive in exchange for the transfer of control of a product or a service to a customer. To determine the transaction price, the Company considers the existence of any significant financing component, the effects of any variable elements, noncash considerations and consideration payable to the customer. If a significant financing component exists, the transaction price is adjusted for the time value of money. If an element of variability exists, the Company must estimate the consideration it expects to receive and uses that amount as the basis for recognizing revenue as the product or the service is transferred to the customer. There are two methods for determining the amount of variable consideration: (i) the expected value method, which is the sum of probability-weighted amounts in a range of possible consideration amounts, and (ii) the mostly likely amount method, which identifies the single most likely amount in a range of possible consideration amounts.

If a contract has multiple performance obligations, the Company allocates the transaction price to each distinct performance obligation in an amount that reflects the consideration the Company is entitled to receive in exchange for satisfying each distinct performance obligation. For each distinct performance obligation, revenue is recognized when (or as) the Company transfers control of the product or the service applicable to such performance obligation.

In those instances where the Company first receives consideration in advance of satisfying its performance obligation, the Company classifies such consideration as deferred revenue until (or as) the Company satisfies such performance obligation. In those instances where the Company first satisfies its performance obligation prior to its receipt of consideration, the consideration is recorded as accounts receivable.

The Company expenses incremental costs of obtaining and fulfilling a contract as and when incurred if the expected amortization period of the asset that would be recognized is one year or less, or if the amount of the asset is immaterial. Otherwise, such costs are capitalized as contract assets if they are incremental to the contract and amortized to expense proportionate to revenue recognition of the underlying contract.

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. 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 recognizes forfeitures for all awards as such forfeitures occur.

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 for the year ended December 31, 2016. 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,
	2018		2017		2016
Warrants for common stock		85,094		225,756		134,113
Common stock options		6,980,581		5,458,043		3,910,350
Restricted stock units		188,625		212,625		525,250
Series A convertible preferred stock (if converted)		14,097,745		14,097,745		14,097,745
		21,352,045		19,994,169		18,667,458

Going Concern Assessment

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 as of the date of the issuance of these financial statements.

Recently Adopted Accounting Pronouncements

In November 2016, the Financial Accounting Standards Board (FASB) issued Accounting Standards Update (ASU) No. 2016-18 (ASU 2016-18), which requires that a statement of cash flows explain the change during the period in the total of cash, cash equivalents, and amounts generally described as restricted cash or restricted cash equivalents. ASU 2016-18 is effective for fiscal years beginning after December 15, 2017. The Company adopted the update retrospectively to each period presented. The adoption of this guidance did not have a material impact on the Company’s consolidated financial statements.

In August 2016, the FASB issued ASU 2016-15, which clarifies how entities should classify certain cash receipts and cash payments on the statement of cash flows and how the predominance principle should be applied when cash receipts and cash payments have aspects of more than one class of cash flows. The Company adopted ASU 2016-15 on January 1, 2018. The Company adopted the update retrospectively to each period presented and adjusted the Consolidated Statements of Cash Flows for the year ended December 31, 2017 to reclassify cash payments included in the loss on extinguishment of debt from an operating activity to a financing activity.

In May 2014, the FASB issued ASU 2014-09 related to Accounting Standards Codification (ASC) Topic 606, 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 and reflects the amount of the consideration 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 when (or as) the customer obtains control of the product or service. 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 adopted ASU 2014-09 in the first quarter of 2018 using the full retrospective method. The Company has evaluated the effect that the updated standard had on its internal processes, financial statements and related disclosures, and has determined that the adoption did not have a material impact on the Company’s historical consolidated financial statements.

Recently Issued Accounting Pronouncements

In November 2018, the FASB issued ASU 2018-18, which clarifies the interaction between ASC Topic 808, Collaborative Arrangements, and ASC Topic 606, Revenue from Contracts with Customers. The guidance, among other items, clarifies that certain transactions between collaborative participants should be accounted for as revenue under Topic 606 when the collaborative arrangement participant is a customer in the context of a unit of account. ASU 2018-18 is effective for fiscal years beginning after December 15, 2019. The Company believes that the adoption of this guidance will not have a material impact on the Company’s consolidated financial statements.

In August 2018, the FASB issued ASU 2018-13, which amends the disclosure requirements in ASC Topic 820 by adding, changing, or removing certain disclosures. ASU 2018-13 is effective for fiscal years beginning after December 15, 2019. The Company believes that the adoption of this guidance will not have a material impact on the Company’s consolidated financial statements.

In June 2018, the FASB issued ASU 2018-07. ASU 2018-07 expands the scope of ASC 718, Compensation- Stock Compensation, to include share-based payment transactions for acquiring goods and services from nonemployees. Consistent with the accounting requirement for employee share-based payment awards, nonemployee share-based payment awards within the scope of ASC 718 will be measured at the grant-date fair value of the equity instruments that an entity is obligated to issue when the good has been delivered or the service has been rendered. ASU 2018-07 is effective for fiscal years beginning after December 15, 2018. The Company believes that the adoption of this guidance will not have a material impact on the Company’s consolidated financial statements.

In February 2016, the FASB issued ASU 2016-02, Leases, which requires a lessee to recognize a lease liability and a right-of-use asset for all leases with lease terms of more than 12 months. This guidance is effective for annual reporting periods beginning after December 15, 2018, including interim periods within those years, and early adoption is permitted. Companies may adopt this guidance using a modified retrospective approach for leases that exist or are entered into after the beginning of the earliest comparative period in the financial statements. In July 2018, the FASB issued ASU 2018-11, which provides the option of an additional transition method that allows entities to initially apply the new lease guidance at the adoption date and recognize a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. While the Company is continuing to evaluate its significant lease arrangement to assess the potential impact of the adoption of the new lease guidance on its consolidated financial statements, the Company adopted the new lease guidance on January 1, 2019, using a modified retrospective approach, using the effective date as the date of initial application. Consequently, financial information and disclosures required under the new guidance will not be provided for dates and periods prior to January 1, 2019. The Company anticipates that the adoption will result in an increase in assets of approximately $17.0 million and an increase of liabilities of approximately $19.0 million recorded on its Consolidated Balance Sheet for leases commencing prior to the effective date. The Company does not expect the guidance to have a material effect on the Consolidated Statements of Operations and Comprehensive Loss or the Consolidated Statements of Cash Flows.

Collaboration and License Agreements

12 Months Ended

Dec. 31, 2018

Collaboration And License Agreements Disclosure [Abstract]

Collaboration and License Agreements

2. Collaboration and License Agreements

Ono Collaboration and Option Agreement

On September 14, 2018, the Company entered into a Collaboration and Option Agreement (the Ono Agreement) with Ono Pharmaceutical Co. Ltd. (Ono) for the joint development and commercialization of two off-the-shelf, iPSC-derived CAR T-cell product candidates. The first off-the-shelf, iPSC-derived CAR T-cell candidate (Candidate 1) targets an antigen expressed on certain lymphoblastic leukemias, and the second off-the-shelf, iPSC-derived CAR T-cell candidate (Candidate 2) targets a novel antigen identified by Ono expressed on certain solid tumors (each a Candidate and, collectively, the Candidates).

Pursuant to the Ono Agreement, the Company and Ono are jointly conducting research and development activities under a joint development plan, with the goal of advancing each Candidate to a pre-defined preclinical milestone. The Company has granted to Ono, during a specified period of time, an option to obtain an exclusive license under certain intellectual property rights to develop and commercialize (a) Candidate 1 in Asia, with the Company retaining rights for development and commercialization in all other territories of the world and (b) Candidate 2 in all territories of the world, with the Company retaining the right to co-develop and co-commercialize Candidate 2 in the United States and Europe under a joint arrangement whereby it is eligible to share at least 50% of the profits and losses (each, an Option).

For each Candidate, the Option will expire upon the earliest of: (a) the achievement of the pre-defined preclinical milestone, (b) termination by Ono of research and development activities for the Candidate and (c) the date that is the later of (i) four years after the Effective Date and (ii) completion of all applicable activities contemplated under the joint development plan (the Option Period). The Company has maintained worldwide rights of manufacture for both Candidates.

Under the terms of the Ono Agreement, Ono paid the Company an upfront, non-refundable and non-creditable payment of $10.0 million in connection with entering into the Ono Agreement. Additionally, as consideration for the Company’s conduct of research and preclinical development under a joint development plan, Ono pays the Company annual research and development fees set forth in the annual budget included in the joint development plan, which fees are estimated to be $20.0 million in aggregate over the course of the joint development plan. The Company received $5.0 million in October 2018 as a prepayment for the first year of research and development.

Further, under the terms of the Ono Agreement, Ono has agreed to pay the Company up to an additional $40.0 million, subject to the achievement of a preclinical milestone (Option Milestone) and the exercise by Ono of the Options (Option Exercise Fees) during the Option Period. Such fees are in addition to the upfront payment and research and development fees.

Subject to Ono’s exercise of the Options and to the achievement of certain clinical, regulatory and commercial milestones (Milestones) with respect to each Candidate in specified territories, the Company is entitled to receive an aggregate of up to $285.0 million in milestone payments for Candidate 1 and an aggregate of up to $895.0 million in milestone payments for Candidate 2, with the applicable milestone payments for Candidate 2 for the United States and Europe subject to reduction by 50% if the Company elects to co-develop and co-commercialize Candidate 2 as described above. The Company is also eligible to receive tiered royalties (Royalties) ranging from the mid-single digits to the low-double digits based on annual net sales by Ono of each Candidate in specified territories, with such royalties subject to certain reductions.

The Ono Agreement will terminate with respect to a Candidate if Ono does not exercise its Option for a Candidate within the Option Period, or in its entirety if Ono does not exercise any of its Options for the Candidates within their respective Option Periods. In addition, either party may terminate the Ono Agreement in the event of breach, insolvency or patent challenges by the other party; provided, that Ono may terminate the Ono Agreement in its sole discretion (x) on a Candidate-by-Candidate basis at any time after the second anniversary of the effective date of the Ono Agreement or (y) on a Candidate-by-Candidate or country-by-country basis at any time after the expiration of the Option Period, subject to certain limitations. The Ono Agreement will expire on a Candidate-by-Candidate and country-by-country basis upon the expiration of the applicable royalty term, or in its entirety upon the expiration of all applicable payment obligations under the Ono Agreement.

The Company applied Accounting Standards Codification (ASC) 808, Collaborative Arrangements and determined that the Ono Agreement is applicable to such guidance. The Company concluded that Ono represented a customer and applied relevant guidance from ASC 606, Revenue from Contracts with Customers (ASC 606) to evaluate the appropriate accounting for the Ono Agreement. In accordance with this guidance, the Company identified its performance obligations, including its grant of a license to Ono to certain of its intellectual property subject to certain conditions, its conduct of research services, and its participation in a joint steering committee. The Company determined that its grant of a license to Ono to certain of its intellectual property subject to certain conditions was not distinct from other performance obligations because such grant is dependent on the conduct and results of the research services. As a result, the license is classified as symbolic intellectual property under ASC 606. Additionally, the Company determined that its conduct of research services was not distinct from other performance obligations since such conduct is dependent on the guidance of the joint steering committee. Accordingly, the Company determined that all performance obligations should be accounted for as one combined performance obligation, and that the combined performance obligation is transferred over the expected term of the conduct of the research services, which is estimated to be four years.

The Company also assessed, in connection with the upfront, non-refundable and non-creditable payment of $10.0 million received in September 2018 and the $5.0 million prepayment of the first-year research and development fees in October 2018, whether a significant financing component exists under the Ono Agreement. Such assessment evaluated whether: (i) a substantial amount of the consideration is variable, (ii) the amount, or timing of payment, of the consideration would have varied based on the occurrence or non-occurrence of future events that are not substantially within the control of the Company or Ono, and (iii) the timing of the transfer of the performance obligations is at the discretion of Ono. Based on its assessment, the Company concluded that there was not a significant financing component.

The Company also assessed the effects of any variable elements under the Ono Agreement. Such assessment evaluated, among other things, the likelihood of receiving (i) preclinical milestone and option fees, (ii) various clinical, regulatory and commercial milestone payments, and (iii) royalties on net sales of either product Candidate. Based on its assessment, the Company concluded that, based on the likelihood of these variable components occurring, there has not been a significant variable element included in the transaction price to date.

In accordance with ASC 606, the Company determined that the initial transaction price under the Ono Agreement equals $30.0 million, consisting of the upfront, non-refundable and non-creditable payment of $10.0 million and the aggregate estimated research and development fees of $20.0 million. The upfront payment of $10.0 million was recorded as deferred revenue and will be recognized as revenue over time in conjunction with the Company’s conduct of research services over the estimated four-year period based on actual costs incurred compared to estimated total costs expected to be incurred under the Ono Agreement, as the research and development activities are the primary component of the combined performance obligation. The Company recorded the $5.0 million prepayment of the first-year research and development fees as deferred, and such fees will be recognized as revenue as the research services are delivered.

The Company has not assigned a transaction price to any Option Milestone, Milestones or Option Exercise Fees given the substantial uncertainty related to their achievement and has not assigned a transaction price to any Royalties.

As a direct result of the Company’s entry into the Ono Agreement, the Company incurred an aggregate of $2.0 million in sublicense consideration to existing licensors of the Company, of which $1.0 million was paid during the year ended December 31, 2018. The $2.0 million in sublicense consideration represents an asset under ASC 340, Other Assets and Deferred Costs. As such, the $2.0 million asset will be amortized to research and development expense in conjunction with the Company’s revenue recognition under the Ono Agreement. As of December 31, 2018, the contract asset had a balance of $2.0 million.

The Company recognized revenue of $0.6 million under the Ono Agreement for the year ended December 31, 2018. Such revenue was comprised of $0.4 million associated with research services and $0.2 million associated with the upfront payment. These amounts were initially recorded in deferred revenue. As of December 31, 2018, aggregate deferred revenue related to the Ono Agreement was $14.4 million, of which $6.9 million is classified as current.

Juno Collaboration and License Agreement

On May 4, 2015, the Company entered into a strategic research collaboration and license agreement (the Juno 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. Under the Juno Agreement, the Company is primarily responsible for screening and identifying small molecule modulators of immunological cells, while Juno is primarily responsible for the development and commercialization of engineered T-cell immunotherapies incorporating the Company’s modulators. Subject to the selection by Juno of designated tumor-associated antigen targets which selection may be made by Juno on a target-by-target basis, the Company agreed to grant 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 such designated tumor-associated antigen targets. The Company 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 designated tumor-associated antigen targets selected by Juno. The Juno Agreement will end on the date that no further payments are due under the Juno Agreement, unless terminated earlier pursuant to the terms of the Juno Agreement.

Pursuant to the terms of the Juno Agreement, Juno paid the Company an upfront, non-refundable and non-creditable 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 for an aggregate purchase price of $8.0 million. The Company determined that this common stock purchase represented a premium of $3.40 per share, or $3.4 million in aggregate (Equity Premium), and the remaining $4.6 million was recorded as issuance of common stock in shareholders’ equity.

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 Juno 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 a one-time, non-refundable 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.

Under the Juno Agreement, the Company is eligible 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 (Selection Fees). Additionally, 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 (Milestone Fees). 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 (Bonus Milestone Fees).

Under the Juno Agreement, 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 (Royalty Payments).

The Company applied ASC 606 to evaluate the appropriate accounting for the Juno Agreement. In accordance with this guidance, the Company identified its performance obligations, including its grant of an exclusive worldwide license to certain of its intellectual property subject to certain conditions, its conduct of research services and its participation in a joint research committee. The Company determined that its grant of an exclusive worldwide license to certain of its intellectual property subject to certain conditions was not distinct from other performance obligations because such grant is dependent on the conduct and results of the research services. As a result, the exclusive worldwide license is classified as symbolic intellectual property under ASC 606. Additionally, the Company determined that its conduct of research services was not distinct from other performance obligations since such conduct is dependent on the guidance of the joint research committee. Accordingly, the Company determined that all performance obligations should be accounted for as one combined performance obligation since no individual performance obligation is distinct, and that the combined performance obligation is transferred ratably over the expected term of conduct of the research services, which is four years.

The Company also assessed, in connection with the upfront, non-refundable and non-creditable payment of $5.0 million and the $3.4 million Equity Premium, whether a significant financing component exists under the Juno Agreement. Such assessment evaluated whether: (i) a substantial amount of the consideration is variable, (ii) the amount, or timing of payment, of the consideration would have varied based on the occurrence or non-occurrence of future events that are not substantially within the control of the Company or Juno, and (iii) the timing of the transfer of the performance obligations is at the discretion of Juno. Based on its assessment, the Company concluded that there was not a significant financing component.

The Company also assessed the effects of any variable elements under the Juno Agreement. Such assessment evaluated, among other things, the likelihood of receiving (i) various clinical, regulatory and commercial milestone payments and (ii) royalties on net sales of any Juno therapies that use or incorporate the Company’s small molecule modulators. Based on its assessment, the Company concluded that based on the likelihood of these variable components occurring there was not a significant variable element included in the transaction price.

In accordance with ASC 606, the Company determined that the initial transaction price under the Juno Agreement equals $16.4 million, consisting of the upfront, non-refundable and non-creditable payment of $5.0 million, the $3.4 million Equity Premium and $8.0 million of estimated payments for the conduct of research services during the initial four-year term. The upfront, non-refundable and non-creditable payment of $5.0 million and the $3.4 million Equity Premium were recorded as deferred revenue, and are being recognized as revenue ratably over four years, which approximates the level of effort to satisfy the Company’s performance obligation relative to the total effort expected to satisfy the Company’s performance obligation.

The Company has not assigned a transaction price to any Selection Fees given the substantial uncertainty related to their occurrence. Since the Selection Fees are closely aligned with the previously discussed combined performance obligation, any such future consideration in connection with selection fees will be recognized in conjunction with the combined performance obligation. Additionally, the Company has not assigned a transaction price to any Milestone Fees or Bonus Milestone Fees given the substantial uncertainty related to their achievement. Since any performance obligation would be complete at the time of milestone achievement, any future consideration in connection with milestone payments will be recognized on the date of achievement. Finally, the Company has not assigned a transaction price to any Royalty Payments given the substantial uncertainty related to their achievement. Since any performance obligation would be complete at the time of potential sale of each Juno therapy that uses or incorporates the Company’s small molecule modulators, any future consideration in connection with Royalty Payments will be recognized on the date of sale.

Total revenue recognized under the Juno Agreement for the years ended December 31, 2018, 2017 and 2016 was $4.1 million, $4.1 million, and $4.4 million, respectively. Such revenue for each period presented included $2.1 million associated with the upfront fee and the Equity Premium, and $2.0 million, $2.0 million, and $2.3 million for the years ended December 31, 2018, 2017, and 2016, respectively, associated with research services. As of December 31, 2018, aggregate deferred revenue related to the Juno Agreement was $0.7 million, all of which is classified as current.

In March 2018, Juno was acquired by Celgene Corporation (Celgene). This acquisition did not affect the terms of the Juno Agreement. On January 3, 2019, Celgene announced that it had entered into a definitive merger agreement with Bristol-Myers Squibb Company (BMS), under which BMS will acquire Celgene.

Memorial Sloan Kettering Cancer Center License Agreement

On May 15, 2018, the Company entered into an Amended and Restated Exclusive License Agreement (the Amended MSK License) with Memorial Sloan Kettering Cancer Center (MSK). The Amended MSK License amends and restates the Exclusive License Agreement entered into between the Company and MSK on August 19, 2016 (the Original MSK License), pursuant to which the Company entered into an exclusive license agreement with MSK for rights relating to compositions and methods covering iPSC-derived iPSC-derived cellular immunotherapy, including T cells and NK cells derived from iPSCs engineered with CARs.

Pursuant to the Amended MSK License, MSK granted to the Company additional licenses to certain patents and patent applications relating to new CAR constructs and off-the-shelf CAR T cells, including the use of CRISPR and other innovative technologies for their production, in each case to research, develop, and commercialize licensed products in the field of all human therapeutic uses worldwide. The Company has the right to grant sublicenses to certain licensed rights in accordance with the terms of the Amended MSK License, in which case it is obligated to pay MSK a percentage of certain sublicense income received by the Company.

The Company issued 500,000 shares of the Company’s common stock to MSK (the MSK Shares) and, in return, MSK returned its entire interest in Tfinity Therapeutics, Inc. (Tfinity) to the Company. As a result, as of the effective date of the Amended MSK License, Tfinity is a wholly-owned subsidiary of the Company. The MSK Shares were issued pursuant to an exemption from registration under the Securities Act of 1933, as amended (the Securities Act), in reliance on Section 4(a)(2) of the Securities Act regarding transactions by an issuer not involving a public offering.

Additionally, the Company paid an upfront fee of $0.5 million. The Company is also obligated to pay to MSK an annual license maintenance fee during the term of the agreement, and milestone payments upon the achievement of specified clinical, regulatory and commercial milestones for licensed products as well as royalty payments on net sales of licensed products.

Furthermore, in the event a licensed product achieves a specified clinical milestone, MSK is then eligible to receive additional milestone payments, where the amount of such payments owed to MSK are contingent upon certain increases in the price of the Company’s common stock following the date of achievement of such clinical milestone.

Given the high degree of uncertainty surrounding the achievement of clinical milestones and the requisite increase in the price of the Company’s common stock, the Company has not recorded a liability for such payments.

During the year ended December 31, 2018, the Company recognized an aggregate of $5.3 million of research and development expenses, consisting of the $0.5 million upfront cash payment to MSK and the issuance of the MSK Shares, valued at $4.8 million, associated with the Amended MSK License.

Gladstone License Agreement

On September 11, 2018, the Company entered into an exclusive license agreement (the Gladstone License Agreement) with the J. David Gladstone Institutes (Gladstone).

Pursuant to the Gladstone License Agreement, Gladstone granted to the Company exclusive licenses to certain patents and patent applications (the Patent Rights) for the research, development, manufacturing, and commercialization of human therapeutics derived from iPSCs. The Patent Rights cover the use of the clustered regularly interspaced short palindromic repeat (CRISPR) and engineered nuclease-deactivated CRISPR-associated protein-9 (dCas9) system, known as the CRISPR activation (CRISPRa) system, for cellular reprogramming and iPSC generation.

In consideration for the rights granted under the Gladstone License Agreement, the Company issued to Gladstone 100,000 shares of the Company’s common stock (the Gladstone Shares). The Gladstone Shares were issued pursuant to an exemption from registration under the Securities Act, in reliance on Section 4(a)(2) of the Securities Act regarding transactions by an issuer not involving a public offering.

Additionally, the Company paid Gladstone an upfront fee of $0.1 million and is obligated to pay Gladstone milestone payments in an aggregate amount of up to approximately $1.9 million upon the achievement of specified clinical, regulatory and commercial milestones as well as tiered royalties in the low single digits on net sales of human therapeutic products covered by the Patent Rights. The Company is also obligated to pay Gladstone a tiered percentage in the low- to mid-single digits of certain income received by the Company in connection with the sublicense of the Patent Rights.

During the year ended December 31, 2018, the Company recognized an aggregate of $1.4 million of research and development expenses, consisting of the $0.1 million upfront cash payment to Gladstone and the issuance of the Gladstone Shares, valued at $1.3 million, associated with the Gladstone License Agreement.

California Institute for Regenerative Medicine Award

12 Months Ended

Dec. 31, 2018

Award From Regenerative Medicine Institute [Abstract]

California Institute for Regenerative Medicine Award

3.	California Institute for Regenerative Medicine Award

On April 5, 2018, the Company executed an award agreement with the California Institute for Regenerative Medicine (CIRM) pursuant to which CIRM awarded the Company $4.0 million to advance the Company’s FT516 product candidate into a first-in-human clinical trial for the treatment of subjects with advanced solid tumors, including in combination with monoclonal antibody therapy (the Award). Pursuant to the terms of the Award, the Company is eligible to receive five disbursements in varying amounts totaling $4.0 million, with one disbursement receivable upon the execution of the Award, and four disbursements receivable upon the completion of certain milestones throughout the project period, which was estimated to be from April 1, 2018, to June 30, 2019 (the Project Period). The Award is subject to certain co-funding requirements by the Company, and the Company is required to provide CIRM progress and financial update reports throughout the Project Period. In December 2018, the Company discussed with CIRM its intent to pursue the clinical development of FT516 in relapsed / refractory hematologic malignancies in addition to advanced solid tumors, and the Company’s preference to first submit an IND application for FT516 in relapsed / refractory hematologic malignancies rather than in advanced solid tumors. In January 2019, the Company submitted its IND application for FT516 in relapsed / refractory hematologic malignancies, which IND submission was allowed by the FDA in February 2019. The Company and CIRM have agreed to suspend the Award until such time as the Company elects to proceed with its submission of an IND application for FT516 in advanced solid tumors. At the time of suspension, an additional $0.5 million was available for funding under the Award.

Pursuant to the terms of the Award, the Company, in its sole discretion, has the option to treat the Award either as a loan or as a grant. In the event the Company elects to treat the Award as a loan, the Company will be obligated to repay i) 60%, ii) 80%, iii) 100% or iv) 100% plus interest at 7% plus LIBOR, of the total Award to CIRM, where such repayment rate is dependent upon the phase of clinical development of FT516 at the time of the Company’s election. If the Company does not elect to treat the Award as a loan within 10 years of the date of the Award, the Award will be considered a grant and the Company will be obligated to pay to CIRM a royalty on commercial sales of FT516 until such royalty payments equal nine times the total amount awarded to the Company under the Award.

Since the Company may, at its election, repay some or all of the Award, the Company accounts for the Award as a liability until the time of election. As of December 31, 2018, the Company has received aggregate disbursements under the Award in the amount of $3.5 million. The aggregate amount received is recorded as a CIRM Liability on the accompanying Consolidated Balance Sheets and classified as current or non-current based on the potential amount payable within twelve months of the current balance sheet date.

Short-term Investments

12 Months Ended

Dec. 31, 2018

Short Term Investments [Abstract]

Short-term Investments

4. Short-term Investments

The Company invests portions of excess cash in United States treasuries with maturities ranging from three 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, 2018 and 2017 (in thousands):

	Maturity (in years)	Amortized Cost		Unrealized Losses			Unrealized Gains		Estimated Fair Value
December 31, 2018
U.S. Treasury debt securities	1 or less		10,495		(2	)		—		10,493
Total		$	10,495	$	(2	)	$	—	$	10,493

December 31, 2017
U.S. Treasury debt securities	1 or less		12,000		(3	)		—		11,997
Total		$	12,000	$	(3	)	$	—	$	11,997

The Company reviewed its investment holdings as of December 31, 2018 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 years ended December 31, 2018 and 2017, the Company did not recognize any impairment or gains or losses on sales of available-for-sale securities.

Property and Equipment

12 Months Ended

Dec. 31, 2018

Property Plant And Equipment [Abstract]

Property and Equipment

5. Property and Equipment

Property and equipment consist of the following (in thousands):

	December 31,
	2018			2017
Furniture and fixtures	$	516		$	508
Computer and office equipment		688			527
Software		103			103
Leasehold improvements—building		288			180
Scientific equipment		7,868			6,371
Construction-in-process		1,987			—
Property and equipment, gross		11,450			7,689
Less accumulated depreciation and amortization		(6,325	)		(5,139	)
Property and equipment, net	$	5,125		$	2,550

Depreciation expense related to property and equipment was $1.2 million, $1.0 million, and $0.9 million, for the years ended December 31, 2018, 2017, and 2016, respectively. No material gains or losses on the disposal of property and equipment have been recorded for the years ended December 31, 2018, 2017, and 2016. As of December 31, 2018, $0.2 million of fixed assets had not been paid.

Construction-in-process represents cost incurred under a tenant improvement allowance and costs incurred by the Company in connection with the construction of its expanded facility space, which the Company began to occupy in January 2019 (see Note 6 for further details).

Accrued Expenses, Long-Term Debt, Commitments and Contingencies

12 Months Ended

Dec. 31, 2018

Accrued Expenses Long Term Debt Commitments And Contingencies Disclosure [Abstract]

Accrued Expenses, Long-Term Debt, Commitments and Contingencies

6. Accrued Expenses, Long-Term Debt, Commitments and Contingencies

Accrued Expenses

Current accrued expenses consist of the following (in thousands):

	December 31, 2018		December 31, 2017
Accrued payroll and other employee benefits	$	2,938	$	1,761
Accrued clinical trial related costs		4,729		3,323
Accrued other		3,259		2,170
Accrued expenses	$	10,926	$	7,254

Long-term accrued expenses consist primarily of the accrual for the final payment fee associated with our long-term debt.

Long-Term Debt

Long-term debt and unamortized discount balances are as follows (in thousands):

	December 31, 2018			December 31, 2017
Long-term debt	$	15,000		$	15,000
Less debt issuance costs and discount, net of current portion		(54	)		(192	)
Long-term debt, net of long-term portion of debt issuance costs and discount		14,946			14,808
Less current portion of long-term debt		(2,500	)		—
Long-term debt, net	$	12,446		$	14,808
Current portion of long-term debt	$	2,500		$	—
Less current portion of debt issuance costs and discount		(62	)		—
Current portion of long-term debt, net	$	2,438		$	—

SVB Loan Amendment

On July 14, 2017 (the First Amendment Effective Date), the Company entered into the First Amendment (the SVB Loan Amendment) to the Amended and Restated Loan and Security Agreement (the Restated LSA) between the Company and Silicon Valley Bank (the Bank) dated July 30, 2014. The SVB Loan Amendment amends the Restated LSA.

Pursuant to the SVB Loan Amendment, the Bank extended an additional term loan to the Company on July 14, 2017 in the principal amount of $15.0 million (the 2017 Term Loan), a portion of which was applied to repay in full the Company’s existing outstanding debt with the Bank under the Restated LSA, which included outstanding principal, accrued interest, and final payment fees. Following such repayment in full of the Company’s existing outstanding debt with the Bank under the Restated LSA, cash proceeds to the Company from the remaining portion of the 2017 Term Loan were $7.5 million.

The 2017 Term Loan matures on January 1, 2022 (the Term Loan Maturity Date) and bears interest at a floating per annum rate equal to the greater of (i) 3.50% above the Prime Rate (as defined in the SVB Loan Amendment) or (ii) 7.25%; provided, however, that in no event shall such interest rate exceed 8.25%. Interest is payable on a monthly basis on the first day of each month. The interest rate as of December 31, 2018 was 8.25%.

From August 1, 2017 through January 1, 2019 (the Interest-only Period), the Company was required to make monthly payments of interest only. In January 2019, after achievement of a product development milestone, the Company elected to extend the Interest-only Period from January 1, 2019 through and including to July 31, 2019. The Company is required to repay the principal, plus monthly payments of accrued interest, in 30 equal monthly installments based on a 30-month amortization schedule.

The Company’s final payment, due on the Term Loan Maturity Date, shall include all outstanding principal and accrued and unpaid interest under the 2017 Term Loan, plus a 7.5%, or $1.1 million, final payment fee. This final payment fee is being accrued as interest expense over the term of the 2017 Term Loan and recorded in accrued expenses.

In connection with the SVB Loan Amendment, the Company issued to the Bank on the First Amendment Effective Date a fully exercisable warrant (the 2017 Warrant), expiring in July 2024, to purchase up to an aggregate of 91,463 shares of the Company’s common stock, subject to adjustment, at an exercise price equal to $3.28 per share. The aggregate fair value of the 2017 Warrant was determined to be $0.2 million using the Black-Scholes option pricing model and was recorded as a debt discount on the 2017 Term Loan. This debt discount is amortized to interest expense over the term of the 2017 Term Loan using the effective interest method. The Company determined the effective interest rate of the 2017 Term Loan to be 10.2% as of the First Amendment Effective Date. In September 2018, the 2017 Warrant was fully exercised in exchange for 67,952 shares of the Company’s common stock in a cashless transaction.

The Company determined the repayment of the Restated LSA and issuance of the 2017 Term Loan was a debt extinguishment and accounted for the 2017 Term Loan at fair value as of the First Amendment Effective Date, accordingly. During the year ended December 31, 2017, the Company recorded a loss on debt extinguishment of $0.1 million, which was primarily related to the unaccrued amount of the final payment fee under the Restated LSA that was paid in connection with the 2017 Term Loan.

The Company is required under its loan agreement with the Bank 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 agreement, which would cause all of the outstanding indebtedness under the facility to become immediately due and payable. The Company has maintained compliance with all such covenants and clauses to date.

For the years ended December 31, 2018 and 2017, the Company recorded $1.7 million and $0.8 million, respectively, in aggregate interest expense related to the 2017 Term Loan.

Restated LSA

On July 30, 2014, the Company entered into the Restated LSA with the Bank, collateralized by substantially all of the Company’s assets, excluding certain intellectual property. 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, 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 were scheduled to mature on January 1, 2018 and June 1, 2018, respectively.

The Company was 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. These final payment fees were accrued as interest expense over the terms of the loans and recorded in accrued expenses.

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 2014 Warrants) at an exercise price of $4.08 per share. In March 2018, a portion of the 2014 Warrants were exercised in exchange for 34,149 shares of the Company’s common stock in a cashless transaction. As of December 31, 2018, warrants to purchase 49,020 shares of the Company’s common stock remain outstanding subject to the 2014 Warrants. The 2014 Warrants expire in December 2021.

For the years ended December 2017, and 2016, the Company recorded $0.5 million and $1.6 million, respectively, in aggregate interest expense related to the Term A and Term B Loans.

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 a prior debt agreement between the Company and the Bank in 2009 remain outstanding as of December 31, 2018, with such warrants to purchase 5,305 and 30,769 shares of the Company’s common stock having expiration dates in January 2019 and August 2021, respectively.

Facility Lease

The Company leases certain office and laboratory space under a non-cancelable operating lease. In May 2018, the Company amended the operating lease, extending the term of the lease through 2028 and agreeing to lease additional space in the same building as its existing space. With respect to the construction of the additional space, the Company received a $1.9 million tenant improvement allowance from its landlord and accounts for such costs as property and equipment with an offset to deferred rent as incurred. Costs under the tenant improvement allowance were paid directly by the landlord. As of December 31, 2018, the full tenant improvement allowance had been utilized, and the Company has spent $0.1 million on construction related costs. The Company began to occupy this additional space in January 2019.

The lease is subject to additional charges for common area maintenance and other costs. In connection with the lease, the Company has a cash-collateralized irrevocable standby letter of credit in the amount of $0.2 million. As of December 31, 2018, future minimum rent and fixed amenities payments, assuming no early termination, under the operating lease are $41.2 million. The Company maintains the right to terminate the lease after October 2025, subject to the Company’s delivery to the landlord of twelve months’ prior written notice and an early termination payment of $2.5 million.

In January 2015, the Company entered into a sublease for additional laboratory space. The sublease was accounted for as an operating lease and expired in September 2017. No future payments remain under the sublease.

Aggregate contractual rent expense was $2.3 million, $2.3 million, and $1.3 million for the years ended December 31, 2018, 2017, and 2016, 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, 2018 are as follows (in thousands):

	Long–Term Debt			Operating Leases		Total
Years Ending December 31,
2019	$	3,720		$	3,019	$	6,739
2020		6,818			3,761		10,579
2021		6,313			3,873		10,186
2022		1,629			3,989		5,618
2023		—			4,109		4,109
Thereafter		—			22,470		22,470
Total	$	18,480		$	41,221	$	59,701
Less interest		(2,355	)
Less additional payments due upon maturity		(1,125	)
Less unamortized debt discount and debt issuance costs		(116	)
Less current portion of long-term debt, net		(2,438	)
Long–term debt, net of current portion	$	12,446

The Company’s long-term debt bears interest at a floating per annum rate equal to the greater of (i) 3.50% above the Prime Rate (as defined in the SVB Loan Amendment) or (ii) 7.25%; provided, however, that in no event shall such interest rate exceed 8.25%. The amounts in the table above assume payment at the current interest rate, which is subject to change. The amounts in the above table reflect the Interest-only Period through July 31, 2019.

Under the Company’s non-cancelable facilities operating lease, in addition to rent, the lease is subject to certain fixed amenities fees. The above table includes all such fixed fees. The lease is subject to additional variable charges for common area maintenance and other costs. The Company maintains the right to terminate the lease after October 2025, subject to our delivery to the landlord of twelve months’ prior written notice and an early termination payment of $2.5 million.

Convertible Preferred Stock and Stockholders' Equity

12 Months Ended

Dec. 31, 2018

Convertible Preferred Stock And Stockholders Deficit Disclosure [Abstract]

Convertible Preferred Stock and Stockholders’ Equity

7. Convertible Preferred Stock and Stockholders’ Equity

Convertible Preferred Stock

In November 2016, the Company completed a private placement of stock in which investors, including investors 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). The terms of the CoD prohibited Redmile 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 could 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%. On May 2, 2017, the Company’s stockholders approved the issuance of up to an aggregate of 14,097,745 shares of common stock upon the conversion of the outstanding shares of Class A Preferred. As a result, Redmile has the right to increase the Redmile Percentage Limitation to any percentage in excess of 19.99% at its election. 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 $54.9 million.

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 among holders of the Company’s common stock and holders of the Class A Preferred, pro rata based on the number of shares held by each such holder (treated for this purpose as if the Class A Preferred had been converted to common stock).

The Company evaluated the Class A Preferred for liability or equity classification under ASC 480, Distinguishing Liabilities from Equity, and determined that equity treatment was appropriate because the Class A Preferred did not meet the definition of the liability instruments defined thereunder for convertible instruments. Specifically, the Class A Preferred are not mandatorily redeemable and do not embody an obligation to buy back the shares outside of the Company’s control in a manner that could require the transfer of assets. Additionally, the Company determined that the Class A Preferred would be recorded as permanent equity, not temporary equity, based on the guidance of ASC 480 given that they are not redeemable for cash or other assets (i) on a fixed or determinable date, (ii) at the option of the holder, and (iii) upon the occurrence of an event that is not solely within control of the Company.

The Company also evaluated the Class A Preferred in accordance with the provisions of ASC 815, Derivatives and Hedging, including the consideration of embedded derivatives requiring bifurcation from the equity host. Based on this assessment, the Company determined that the conversion option is clearly and closely related to the equity host, and thus, bifurcation is not required.

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 was 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 November 2016 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, 2018, the Board of Directors of the Company has not declared any dividends.

2013 Stock Option and Incentive Plan, and Inducement Equity 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). The 2013 Plan became effective immediately prior to the Company’s IPO. The 2013 Plan was subsequently amended in May 2017. 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, and in May 2017, stockholders approved an additional 2,500,000 shares of common stock 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 a previously existing equity plan from 2007 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) 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 2013 Plan 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 2013 Plan, 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 2013 Plan is ten years.

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. In January 2019 and January 2018, an additional 200,000 shares and 400,000 shares, respectively, of common stock were 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 Unit Awards

Stock Options. The following table summarizes stock option activity and related information under all equity plans for the years ended December 31, 2018, 2017 and 2016:

	Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value (in 000s)
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
Granted		2,522,920			3.09
Exercised		(83,220	)		2.79
Cancelled		(892,007	)		3.50
Outstanding at December 31, 2017		5,458,043		$	3.52		7.99	$	14,754
Granted		3,251,980			8.30
Exercised		(694,830	)		3.88
Cancelled		(1,034,612	)		4.36
Outstanding at December 31, 2018		6,980,581		$	5.58		7.87	$	51,497
Options vested and expected to vest at December 31, 2018		6,916,914		$	5.59		7.86	$	50,985
Options exercisable at December 31, 2018		3,430,415		$	4.24		7.00	$	29,470

As of December 31, 2018, 2017 and 2016, the outstanding options included zero, 73,600, and 73,600, 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, 2018, 2017 and 2016, was zero, $0.1 million and $0.1 million, respectively.

For the years ended December 31, 2018, 2017 and 2016, the Company granted its employees and directors 3.3 million, 2.5 million and 2.2 million stock options, respectively, at a weighted-average grant date fair value per share equal to $8.28, $2.29 and $1.80, respectively.

As of December 31, 2018, 2017 and 2016, the unrecognized compensation cost related to outstanding options (excluding those with unachieved performance-based conditions) was $15.9 million, $5.8 million and $4.9 million, respectively, which was expected to be recognized as expense over approximately 3.1 years, 2.6 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, 2018 was $5.5 million. Total cash received upon the exercise of stock options was $2.7 million for the year ended December 31, 2018.

Restricted Stock Units. The following table summarizes Restricted Stock Unit activity and related information under all equity plans for the years ended December 31, 2018, 2017 and 2016:

	Number of Restricted Stock Units			Weighted Average Grant Date Fair Value Per Share		Weighted Average Remaining Vesting Period		Aggregate Intrinsic Value (in 000s)
Outstanding at December 31, 2015		525,250		$	4.89		3.80	$	1,770
Granted		—			—
Vested		—			—
Cancelled		—			—
Outstanding at December 31, 2016		525,250		$	4.89		2.80	$	1,318
Granted		—			—
Vested		(225,125	)		4.89
Cancelled		(87,500	)		4.89
Outstanding at December 31, 2017		212,625		$	4.89		1.80	$	1,299
Granted		—			—
Vested		—			—
Cancelled		(24,000	)		4.89
Outstanding at December 31, 2018		188,625		$	4.89		0.80	$	2,420
Restricted Stock Units expected to vest at December 31, 2018		180,625		$	4.89		0.80	$	2,317

As of December 31, 2018, 2017 and 2016, the unrecognized compensation cost related to outstanding restricted stock units was $0.4 million, $0.9 million, and $1.8 million respectively, which was expected to be recognized as expense over approximately 0.8 years, 1.8 years, and 2.8 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,
	2018		2017		2016
Research and development	$	3,654	$	2,095	$	1,802
General and administrative		2,639		1,511		1,382
Total stock-based compensation expense	$	6,293	$	3,606	$	3,184

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,
	2018			2017			2016
Risk–free interest rate		2.5	%		2.0	%		1.6	%
Expected volatility		79.3	%		90.1	%		79.9	%
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.

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,
	2018			2017			2016
Risk–free interest rate		2.7	%		2.1	%		1.5	%
Expected volatility		79.7	%		87.4	%		83.1	%
Expected term (in years)		7.9			8.5			6.4
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 Loan Amendment on July 14, 2017, the Company issued SVB fully-exercisable warrants to purchase an aggregate of 91,463 shares of the Company’s common stock at an exercise price of $3.28 per share. The warrants would have expired in July 2024. In September 2018, the 2017 Warrant was fully exercised in exchange for 67,952 shares of the Company’s common stock in a cashless transaction. See Note 6 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 $0.2 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 July 14, 2017
Risk–free interest rate		2.1	%
Expected volatility		88	%
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,
	2018		2017
Common stock warrants		85,094		225,756
Convertible preferred stock (if converted)		14,097,745		14,097,745
Common stock options		6,980,581		5,458,043
Restricted stock units		188,625		212,625
Awards available under the 2013 Plan		3,605,510		3,572,112
Awards available under the Inducement Plan		379,178		100,000
Employee stock purchase plan		729,000		729,000
		26,065,733		24,395,281

Income Taxes

12 Months Ended

Dec. 31, 2018

Income Tax Disclosure [Abstract]

Income Taxes

8. 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,
	2018			2017			2016
Tax computed at federal statutory rate	$	(13,985	)	$	(14,603	)	$	(11,377	)
State tax, net of federal tax benefit		(1,620	)		(1,315	)		(2,089	)
Permanent differences		22			795			292
Stock compensation		(307	)		539			968
R&D tax credits		(3,301	)		(2,934	)		(971	)
Reserve for uncertain tax positions		1,160			1,326			2,076
Tax attribute limitation		—			—			54
Tax Cuts and Jobs Act		—			25,280			—
Other		304			46			(74	)
Valuation allowance		17,727			(9,134	)		11,121
Income tax expense	$	—		$	—		$	—

Significant components of the Company’s deferred tax assets are summarized as follows (in thousands):

	As of December 31,
	2018			2017
Deferred tax assets:
Section 59e amortization	$	19,069		$	14,365
Net operating losses		30,981			27,699
R&D tax credits		9,163			5,421
Depreciation and amortization		1,653			581
Deferred revenue		3,906			594
Stock compensation		1,482			876
Other		1,106			96
Deferred tax assets		67,360			49,632
Valuation allowance		(67,360	)		(49,632	)
Net deferred tax assets	$	—		$	—

A valuation allowance of $67.4 million and $49.6 million at December 31, 2018 and 2017, respectively, has been established to offset the deferred tax assets, as realization of such assets is uncertain.

At December 31, 2018, the Company had federal and California net operating loss (NOL) carryforwards of $136.8 million and $137.5 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, 2018, the Company had federal and California research and development (R&D) credit carryforwards of $8.2 million and $5.4 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, (the Code), substantial changes in the Company’s 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 Code, 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, 2018 and concluded there were no ownership changes during the years ended December 31, 2016, 2017, and 2018. 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 and California, and has historically filed income tax returns in 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 2015, 2014, and 2014, 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, 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
Increase related to current year tax positions		4,077
Increase related to prior year tax positions		6
Decrease related to prior year tax positions		(13	)
Balance at December 31, 2017	$	11,800
Increase related to current year tax positions		1,798
Increase related to prior year tax positions		148
Decrease related to prior year tax positions		(199	)
Balance at December 31, 2018	$	13,547

The Company does not anticipate that the amount of unrecognized tax benefits as of December 31, 2018 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, 2018 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.

The Company adopted ASU No. 2016-09 on January 1, 2017. ASU 2016-09 simplifies how several aspects of share-based payments are accounted for and presented in the financial statements. The Company had excess tax benefits for which a benefit could not be previously recognized of $0.1 million. Due to the full valuation allowance on the deferred tax assets, there was no impact to the Company’s consolidated financial statements as a result of the adoption.

The Tax Cuts and Jobs Act (the Act) was enacted on December 22, 2017. The Act reduces the US federal corporate tax rate from 34% to 21%. The reduction in the federal tax rate caused the Company to remeasure its deferred tax assets and liabilities at December 31, 2017. The remeasurement resulted in a provisional income tax expense of $25.3 million, offset by an equal reduction in the valuation allowance during the year ended December 31, 2017. During 2018, the Company finalized its analysis of the provisional impact associated with the remeasurement of deferred tax assets. There was no change in the provisional remeasurement amount previously recorded during 2017.

On December 22, 2017, SEC Staff Accounting Bulletin No. 118 (SAB 118) was issued to address the application of US GAAP in situations when a registrant does not have the necessary information available, prepared, or analyzed (including computations) in reasonable detail to complete the accounting for certain income tax effect of the Act. The impact of the Act was finalized during the year ended December 31, 2018, and no change was made from the previously reported provisional amount.

Selected Quarterly Financial Data

12 Months Ended

Dec. 31, 2018

Quarterly Financial Information Disclosure [Abstract]

Selected Quarterly Financial Data

10. Selected Quarterly Financial Data

(in thousands, except per share data) (unaudited)	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
2018
Revenues	$	1,026		$	1,027		$	1,026		$	1,661
Total operating expenses		15,080			20,632			17,718			18,402
Net loss		(14,135	)		(19,654	)		(16,782	)		(16,027	)
Basic and diluted net loss per common share	$	(0.27	)	$	(0.37	)	$	(0.31	)	$	(0.25	)
2017
Revenues	$	1,027		$	1,026		$	1,026		$	1,027
Total operating expenses		10,998			10,596			11,366			13,271
Net loss		(10,126	)		(9,645	)		(10,684	)		(12,497	)
Basic and diluted net loss per common share	$	(0.24	)	$	(0.23	)	$	(0.26	)	$	(0.29	)

Organization and Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2018

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Public Equity Offerings

Private Placement of Common Stock and Convertible Preferred Stock

Private Placements of Common Stock and Convertible Preferred Stock

Use of Estimates

Principles of Consolidation

Segment Reporting

Fair Value of Financial Instruments

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.

			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, 2018:
Cash equivalents	$	190,514	$	190,514	$	—	$	—
U.S. Treasury debt securities		10,493		10,493		—		—
Total assets measured at fair value on a recurring basis	$	201,007	$	201,007	$	—	$	—

As of December 31, 2017:
Cash equivalents	$	88,952	$	88,952	$	—	$	—
U.S. Treasury debt securities		11,997		11,997		—		—
Total assets measured at fair value on a recurring basis	$	100,949	$	100,949	$	—	$	—

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, 2018 and 2017, the Company had no material liabilities measured at fair value on a recurring basis.

Cash, Cash Equivalents and Restricted Cash

	December 31, 2018		December 31, 2017		December 31, 2016
Cash and cash equivalents	$	190,514	$	88,952	$	88,609
Restricted cash		227		122		122
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$	190,741	$	89,074	$	88,731

Amounts included in restricted cash represent security deposits required to secure the Company’s credit card limit and its facilities lease.

Short-Term Investments

Concentration of Credit Risk

Property and Equipment

Impairment of Long-Lived Assets

Deferred Rent

Revenue Recognition

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

Convertible Preferred Stock

Income Taxes

Comprehensive Loss

Net Loss Per Common Share

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,
	2018		2017		2016
Warrants for common stock		85,094		225,756		134,113
Common stock options		6,980,581		5,458,043		3,910,350
Restricted stock units		188,625		212,625		525,250
Series A convertible preferred stock (if converted)		14,097,745		14,097,745		14,097,745
		21,352,045		19,994,169		18,667,458

Going Concern Assessment

Recently Adopted and Issued Accounting Pronouncements

Recently Adopted Accounting Pronouncements

Recently Issued Accounting Pronouncements

Organization and Summary of Significant Accounting Policies (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018 and 2017 (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, 2018:
Cash equivalents	$	190,514	$	190,514	$	—	$	—
U.S. Treasury debt securities		10,493		10,493		—		—
Total assets measured at fair value on a recurring basis	$	201,007	$	201,007	$	—	$	—

As of December 31, 2017:
Cash equivalents	$	88,952	$	88,952	$	—	$	—
U.S. Treasury debt securities		11,997		11,997		—		—
Total assets measured at fair value on a recurring basis	$	100,949	$	100,949	$	—	$	—

Reconciliation of Cash, Cash Equivalents, and Restricted Cash

	December 31, 2018		December 31, 2017		December 31, 2016
Cash and cash equivalents	$	190,514	$	88,952	$	88,609
Restricted cash		227		122		122
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$	190,741	$	89,074	$	88,731

Schedule of Anti-Dilutive Securities not Included in Calculation of Diluted Net Loss Per Common Share

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,
	2018		2017		2016
Warrants for common stock		85,094		225,756		134,113
Common stock options		6,980,581		5,458,043		3,910,350
Restricted stock units		188,625		212,625		525,250
Series A convertible preferred stock (if converted)		14,097,745		14,097,745		14,097,745
		21,352,045		19,994,169		18,667,458

Short-term Investments (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018 and 2017 (in thousands):

	Maturity (in years)	Amortized Cost		Unrealized Losses			Unrealized Gains		Estimated Fair Value
December 31, 2018
U.S. Treasury debt securities	1 or less		10,495		(2	)		—		10,493
Total		$	10,495	$	(2	)	$	—	$	10,493

December 31, 2017
U.S. Treasury debt securities	1 or less		12,000		(3	)		—		11,997
Total		$	12,000	$	(3	)	$	—	$	11,997

Property and Equipment (Tables)

12 Months Ended

Dec. 31, 2018

Property Plant And Equipment [Abstract]

Schedule of property and equipment

Property and equipment consist of the following (in thousands):

	December 31,
	2018			2017
Furniture and fixtures	$	516		$	508
Computer and office equipment		688			527
Software		103			103
Leasehold improvements—building		288			180
Scientific equipment		7,868			6,371
Construction-in-process		1,987			—
Property and equipment, gross		11,450			7,689
Less accumulated depreciation and amortization		(6,325	)		(5,139	)
Property and equipment, net	$	5,125		$	2,550

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2018

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, 2018		December 31, 2017
Accrued payroll and other employee benefits	$	2,938	$	1,761
Accrued clinical trial related costs		4,729		3,323
Accrued other		3,259		2,170
Accrued expenses	$	10,926	$	7,254

Schedule of long-term debt and unamortized discount balances

Long-term debt and unamortized discount balances are as follows (in thousands):

	December 31, 2018			December 31, 2017
Long-term debt	$	15,000		$	15,000
Less debt issuance costs and discount, net of current portion		(54	)		(192	)
Long-term debt, net of long-term portion of debt issuance costs and discount		14,946			14,808
Less current portion of long-term debt		(2,500	)		—
Long-term debt, net	$	12,446		$	14,808
Current portion of long-term debt	$	2,500		$	—
Less current portion of debt issuance costs and discount		(62	)		—
Current portion of long-term debt, net	$	2,438		$	—

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, 2018 are as follows (in thousands):

	Long–Term Debt			Operating Leases		Total
Years Ending December 31,
2019	$	3,720		$	3,019	$	6,739
2020		6,818			3,761		10,579
2021		6,313			3,873		10,186
2022		1,629			3,989		5,618
2023		—			4,109		4,109
Thereafter		—			22,470		22,470
Total	$	18,480		$	41,221	$	59,701
Less interest		(2,355	)
Less additional payments due upon maturity		(1,125	)
Less unamortized debt discount and debt issuance costs		(116	)
Less current portion of long-term debt, net		(2,438	)
Long–term debt, net of current portion	$	12,446

- Definition

Tabular disclosure of long-debt instruments or arrangements, including identification, terms, features, collateral requirements and other information necessary to a fair presentation. These are debt arrangements that originally required repayment more than twelve months after issuance or greater than the normal operating cycle of the entity, if longer.

+ References

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+ Details

Convertible Preferred Stock and Stockholders' Equity (Tables)

12 Months Ended

Dec. 31, 2018

Stockholders' Equity

Summary of stock option activity and related information under all equity plans

The following table summarizes stock option activity and related information under all equity plans for the years ended December 31, 2018, 2017 and 2016:

	Options			Weighted Average Exercise Price Per Share		Weighted Average Remaining Contractual Term		Aggregate Intrinsic Value (in 000s)
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
Granted		2,522,920			3.09
Exercised		(83,220	)		2.79
Cancelled		(892,007	)		3.50
Outstanding at December 31, 2017		5,458,043		$	3.52		7.99	$	14,754
Granted		3,251,980			8.30
Exercised		(694,830	)		3.88
Cancelled		(1,034,612	)		4.36
Outstanding at December 31, 2018		6,980,581		$	5.58		7.87	$	51,497
Options vested and expected to vest at December 31, 2018		6,916,914		$	5.59		7.86	$	50,985
Options exercisable at December 31, 2018		3,430,415		$	4.24		7.00	$	29,470

Summary of restricted stock unit activity and related information under all equity plans

The following table summarizes Restricted Stock Unit activity and related information under all equity plans for the years ended December 31, 2018, 2017 and 2016:

	Number of Restricted Stock Units			Weighted Average Grant Date Fair Value Per Share		Weighted Average Remaining Vesting Period		Aggregate Intrinsic Value (in 000s)
Outstanding at December 31, 2015		525,250		$	4.89		3.80	$	1,770
Granted		—			—
Vested		—			—
Cancelled		—			—
Outstanding at December 31, 2016		525,250		$	4.89		2.80	$	1,318
Granted		—			—
Vested		(225,125	)		4.89
Cancelled		(87,500	)		4.89
Outstanding at December 31, 2017		212,625		$	4.89		1.80	$	1,299
Granted		—			—
Vested		—			—
Cancelled		(24,000	)		4.89
Outstanding at December 31, 2018		188,625		$	4.89		0.80	$	2,420
Restricted Stock Units expected to vest at December 31, 2018		180,625		$	4.89		0.80	$	2,317

Schedule of common stock reserved for future issuance

Common stock reserved for future issuance is as follows:

	December 31,
	2018		2017
Common stock warrants		85,094		225,756
Convertible preferred stock (if converted)		14,097,745		14,097,745
Common stock options		6,980,581		5,458,043
Restricted stock units		188,625		212,625
Awards available under the 2013 Plan		3,605,510		3,572,112
Awards available under the Inducement Plan		379,178		100,000
Employee stock purchase plan		729,000		729,000
		26,065,733		24,395,281

Warrant

Stockholders' Equity

Schedule of weighted-average assumptions used to determine the fair value of stock option grants

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 July 14, 2017
Risk–free interest rate		2.1	%
Expected volatility		88	%
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

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,
	2018			2017			2016
Risk–free interest rate		2.5	%		2.0	%		1.6	%
Expected volatility		79.3	%		90.1	%		79.9	%
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

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,
	2018			2017			2016
Risk–free interest rate		2.7	%		2.1	%		1.5	%
Expected volatility		79.7	%		87.4	%		83.1	%
Expected term (in years)		7.9			8.5			6.4
Expected dividend yield		0.0	%		0.0	%		0.0	%

Stock Option And Incentive Plan 2013

Stockholders' Equity

Schedule of allocation of stock-based compensation for all stock awards

The allocation of stock-based compensation for all stock awards is as follows (in thousands):

	Years Ended December 31,
	2018		2017		2016
Research and development	$	3,654	$	2,095	$	1,802
General and administrative		2,639		1,511		1,382
Total stock-based compensation expense	$	6,293	$	3,606	$	3,184

Income Taxes (Tables)

12 Months Ended

Dec. 31, 2018

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,
	2018			2017			2016
Tax computed at federal statutory rate	$	(13,985	)	$	(14,603	)	$	(11,377	)
State tax, net of federal tax benefit		(1,620	)		(1,315	)		(2,089	)
Permanent differences		22			795			292
Stock compensation		(307	)		539			968
R&D tax credits		(3,301	)		(2,934	)		(971	)
Reserve for uncertain tax positions		1,160			1,326			2,076
Tax attribute limitation		—			—			54
Tax Cuts and Jobs Act		—			25,280			—
Other		304			46			(74	)
Valuation allowance		17,727			(9,134	)		11,121
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,
	2018			2017
Deferred tax assets:
Section 59e amortization	$	19,069		$	14,365
Net operating losses		30,981			27,699
R&D tax credits		9,163			5,421
Depreciation and amortization		1,653			581
Deferred revenue		3,906			594
Stock compensation		1,482			876
Other		1,106			96
Deferred tax assets		67,360			49,632
Valuation allowance		(67,360	)		(49,632	)
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, 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
Increase related to current year tax positions		4,077
Increase related to prior year tax positions		6
Decrease related to prior year tax positions		(13	)
Balance at December 31, 2017	$	11,800
Increase related to current year tax positions		1,798
Increase related to prior year tax positions		148
Decrease related to prior year tax positions		(199	)
Balance at December 31, 2018	$	13,547

Selected Quarterly Financial Data (Tables)

12 Months Ended

Dec. 31, 2018

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
2018
Revenues	$	1,026		$	1,027		$	1,026		$	1,661
Total operating expenses		15,080			20,632			17,718			18,402
Net loss		(14,135	)		(19,654	)		(16,782	)		(16,027	)
Basic and diluted net loss per common share	$	(0.27	)	$	(0.37	)	$	(0.31	)	$	(0.25	)
2017
Revenues	$	1,027		$	1,026		$	1,026		$	1,027
Total operating expenses		10,998			10,596			11,366			13,271
Net loss		(10,126	)		(9,645	)		(10,684	)		(12,497	)
Basic and diluted net loss per common share	$	(0.24	)	$	(0.23	)	$	(0.26	)	$	(0.29	)

Organization and Summary of Significant Accounting Policies (Details) $ / shares in Units, $ in Thousands	1 Months Ended				12 Months Ended
	Sep. 30, 2018 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Nov. 30, 2016 USD ($) $ / shares shares	Aug. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2018 USD ($) segment shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)
Equity transactions
Net proceeds from issuance of shares after related cash costs					$ 2,693	$ 205	$ 186
Segment Reporting
Number of operating segments \| segment					1
Number of reportable segments \| segment					1
New Accounting Pronouncements and Changes in Accounting Principles
Assets		$ 105,292			$ 213,032	$ 105,292
ASU 2016-02 \| Difference Between Lease Guidance in Effect Before and After Topic 842
New Accounting Pronouncements and Changes in Accounting Principles
Assets					17,000
Liabilities					$ 19,000
Common Stock
Equity transactions
Shares sold \| shares					10,648,149	10,953,750
September 2018 Public Equity Offering \| Investors Affiliated with Directors
Equity transactions
Shares sold \| shares	10,648,149
Share issue price (in dollars per share) \| $ / shares	$ 13.50
Gross proceeds from issuance of shares	$ 143,800
Net proceeds from issuance of shares after related cash costs	134,900
Costs related to equity offering	$ 8,900
December 2017 Public Equity Offering
Equity transactions
Shares sold \| shares		10,953,750
Share issue price (in dollars per share) \| $ / shares		$ 4.20				$ 4.20
Gross proceeds from issuance of shares		$ 46,000
Net proceeds from issuance of shares after related cash costs		43,000
Costs related to equity offering		$ 3,000
Costs related to equity offering paid					$ 300
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			$ 54,900	$ 10,200
Gross proceeds from issuance of shares			$ 56,700

Organization and Summary of Significant Accounting Policies (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasury debt securities	$ 10,493	$ 11,997
Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	190,514	88,952
Total assets measured at fair value on a recurring basis	201,007	100,949
U.S. Treasury debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasury debt securities	10,493	11,997
Quoted prices in Active Market for Identical Assets (Level 1) \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	190,514	88,952
Total assets measured at fair value on a recurring basis	201,007	100,949
Quoted prices in Active Market for Identical Assets (Level 1) \| U.S. Treasury debt securities \| Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
U.S. Treasury debt securities	$ 10,493	$ 11,997

Organization and Summary of Significant Accounting Policies (Details 3) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
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]
Non-financial assets	201,007,000	$ 100,949,000
Liabilities measured at fair value	$ 0	$ 0

Organization and Summary of Significant Accounting Policies (Details 4) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Cash and cash equivalents	$ 190,514	$ 88,952	$ 88,609
Restricted cash	227	122	122
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows	$ 190,741	$ 89,074	$ 88,731	$ 64,931

Organization and Summary of Significant Accounting Policies (Details 5)	12 Months Ended
	Dec. 31, 2018
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
Construction-in-Process \| Minimum
Property and equipment
Estimated useful lives	2 years
Construction-in-Process \| Maximum
Property and equipment
Estimated useful lives	5 years

Organization and Summary of Significant Accounting Policies (Details 6) - shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue Recognition [Abstract]
Uncertain tax position description	more than 50 percent
Anti-dilutive securities (in shares)	21,352,045	19,994,169	18,667,458
Series A Convertible Preferred Stock (if converted)
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	14,097,745	14,097,745	14,097,745
Employee Stock Option
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)			3,284
Warrants For Common Stock
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	85,094	225,756	134,113
Stock Compensation Plan
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	6,980,581	5,458,043	3,910,350
Restricted Stock Units (RSUs)
Revenue Recognition [Abstract]
Anti-dilutive securities (in shares)	188,625	212,625	525,250

Collaboration and License Agreements (Details) - USD ($)					1 Months Ended	3 Months Ended								12 Months Ended
	Sep. 14, 2018	Sep. 11, 2018	May 15, 2018	May 04, 2015	Oct. 31, 2018	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Collaboration agreement
Research and development														$ 56,024,000	$ 34,358,000	$ 26,452,000
Collaboration contract asset						$ 1,958,000								1,958,000
Revenue recognized						1,661,000	$ 1,026,000	$ 1,027,000	$ 1,026,000	$ 1,027,000	$ 1,026,000	$ 1,026,000	$ 1,027,000	4,740,000	4,106,000	4,402,000
Common stock issued, amount														134,791,000	42,979,000
Aggregate deferred revenue, current						$ 7,588,000				$ 2,105,000				$ 7,588,000	$ 2,105,000
Common stock issued						64,693,681				52,648,601				64,693,681	52,648,601
Issuance of common stock for license agreements														$ 6,100,000
Ono Pharmaceutical Co. Ltd
Collaboration agreement
Aggregate research and development fees payments receivable	$ 20,000,000
Payments for research and development fees					$ 5,000,000
Collaborative arrangement potential additional milestones	40,000,000
Non-refundable upfront payments recorded as deferred revenue	$ 10,000,000
Recognition period of deferred revenue	4 years
Collaborative arrangement annual payments receivable recorded as deferred revenue					$ 5,000,000
Ono Pharmaceutical Co. Ltd \| Candidate 2
Collaboration agreement
Percentage of reduction on milestone payments	50.00%
Ono Pharmaceutical Co. Ltd \| Maximum \| Candidate 1
Collaboration agreement
Aggregate milestone payments	$ 285,000,000
Ono Pharmaceutical Co. Ltd \| Maximum \| Candidate 2
Collaboration agreement
Aggregate milestone payments	895,000,000
Ono Pharmaceutical Co. Ltd \| Collaborative Arrangement
Collaboration agreement
Upfront non-refundable, non-creditable payment receivable	10,000,000
Transaction price of the agreement	30,000,000
Research and development	$ 20,000,000
Sub license consideration payable						$ 2,000,000								2,000,000
Sub license consideration paid						1,000,000								1,000,000
Asset corresponding to sub license consideration						2,000,000								2,000,000
Revenue recognized														600,000
Estimated research payments received under agreement														400,000
Proceeds from non refundable upfront fee														200,000
Ono Pharmaceutical Co. Ltd \| Collaborative Arrangement \| Research services
Collaboration agreement
Revenue recognized														14,400,000
Ono Pharmaceutical Co. Ltd \| Collaborative Arrangement \| Upfront Fee
Collaboration agreement
Revenue recognized														6,900,000
Ono Pharmaceutical Co. Ltd \| Collaborative Arrangement \| Minimum
Collaboration agreement
Profits and losses sharing percentage	50.00%
Juno Therapeutics, Inc
Collaboration agreement
Common stock issued				1,000,000
Common stock issued, amount				$ 8,000,000
Issuance of common stock				$ 4,600,000
Research term				4 years
Minimum annual research payments receivable				$ 2,000,000
Extended term of research				2 years
One-time, non-refundable 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
Term of royalties payable after first commercial sale				10 years
Juno Therapeutics, Inc \| Maximum
Collaboration agreement
Aggregate milestone payments				$ 51,000,000
Common stock issued upon exercise of extension				10,000,000
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
Transaction price of the agreement				16,400,000
Non-refundable upfront payments recorded as deferred revenue				$ 5,000,000
Recognition period of deferred revenue				4 years
Revenue recognized														4,100,000	$ 4,100,000	4,400,000
Estimated research payments received under agreement				$ 8,000,000
Proceeds from non refundable upfront fee				$ 5,000,000
Share Price				$ 8.00
Equity premium on share price (in dollars per share)				$ 3.40
Aggregate equity premium on shares issued under agreement				$ 3,400,000
Combined performance obligation occurrence period				4 years
Aggregate equity premium on shares issued recorded as deferred revenue				$ 3,400,000
Aggregate deferred revenue, current						$ 700,000								700,000
Juno Therapeutics, Inc \| Collaborative Arrangement \| Research services
Collaboration agreement
Revenue recognized														2,000,000	2,000,000	2,300,000
Juno Therapeutics, Inc \| Collaborative Arrangement \| Upfront Fee and Equity Premium
Collaboration agreement
Revenue recognized														2,100,000	$ 2,100,000	$ 2,100,000
MSK \| Amended MSK License
Collaboration agreement
Research and development														5,300,000
Common stock issued			500,000
Upfront cash payment			$ 500,000											4,800,000
Issuance of common stock for license agreements														500,000
Gladstone \| Gladstone License Agreement
Collaboration agreement
Aggregate milestone payments		$ 1,900,000
Research and development														1,400,000
Common stock issued		100,000
Upfront cash payment		$ 100,000												100,000
Issuance of common stock for license agreements														$ 1,300,000

California Institute For Regenerative Medicine Award (Details) $ in Millions		1 Months Ended		12 Months Ended
	Apr. 05, 2018 USD ($) Disbursement	Jun. 30, 2019	Jan. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Award from regenerative medicine institute
Period to treat award as grant, if award not treated as loan				10 years
California Institute for Regenerative Medicine
Award from regenerative medicine institute
Receipt of first disbursement under the Award \| $				$ 3.5
California Institute for Regenerative Medicine \| LIBOR \| Scenario, Forecast
Award from regenerative medicine institute
Award considered as a loan, interest rate		7.00%
California Institute for Regenerative Medicine \| Loan Repayment Period One \| Scenario, Forecast
Award from regenerative medicine institute
Repayment percentage of award amount		60.00%
California Institute for Regenerative Medicine \| Loan Repayment Period Two \| Scenario, Forecast
Award from regenerative medicine institute
Repayment percentage of award amount		80.00%
California Institute for Regenerative Medicine \| Loan Repayment Period Three \| Scenario, Forecast
Award from regenerative medicine institute
Repayment percentage of award amount		100.00%
California Institute for Regenerative Medicine \| Loan Repayment Period Four \| Scenario, Forecast
Award from regenerative medicine institute
Repayment percentage of award amount		100.00%
California Institute for Regenerative Medicine \| FT516
Award from regenerative medicine institute
Award agreement executed date	Apr. 05, 2018
Award for first-in-human clinical trial \| $	$ 4.0
Number of disbursements \| Disbursement	5
Number of disbursement receivable upon the execution of the award \| Disbursement	1
Number of disbursements receivable based on completion of certain operating milestones \| Disbursement	4
Estimated project start date	Apr. 01, 2018
Estimated project end date	Jun. 30, 2019
California Institute for Regenerative Medicine \| FT516 \| Subsequent Event
Award from regenerative medicine institute
Addtional amount available for funding under award \| $			$ 0.5

Short-term Investments (Details) - USD ($)	12 Months Ended
Short-term Investments (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Available-for-sale securities, impairment	$ 0
Available-for-sale securities, gains (losses) on sales	$ 0	$ 0
U.S. Treasury debt securities
Schedule Of Available For Sale Securities [Line Items]
Short term investments, maturity start range	3 months
Short term investments, maturity end range	12 months

Short-term Investments (Details 2) - USD ($) $ in Thousands	12 Months Ended
Short-term Investments (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 10,495	$ 12,000
Unrealized Losses	(2)	(3)
Estimated Fair Value	$ 10,493	$ 11,997
U.S. Treasury debt securities
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	1 or less	1 or less
Amortized Cost	$ 10,495	$ 12,000
Unrealized Losses	(2)	(3)
Estimated Fair Value	$ 10,493	$ 11,997

Property and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property and equipment
Property and equipment, gross	$ 11,450	$ 7,689
Less accumulated depreciation and amortization	(6,325)	(5,139)
Property, Plant and Equipment, Net	5,125	2,550
Depreciation expense	1,204	971	$ 881
Fixed assets not yet paid	200
Furniture And Fixtures
Property and equipment
Property and equipment, gross	516	508
Computer And Office Equipment
Property and equipment
Property and equipment, gross	688	527
Software And Software Development Costs
Property and equipment
Property and equipment, gross	103	103
Leasehold Improvements
Property and equipment
Property and equipment, gross	288	180
Scientific Equipment
Property and equipment
Property and equipment, gross	7,868	$ 6,371
Construction-in-Process
Property and equipment
Property and equipment, gross	$ 1,987

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Current accrued expenses
Accrued payroll and other employee benefits	$ 2,938	$ 1,761
Accrued clinical trial related costs	4,729	3,323
Accrued other	3,259	2,170
Accrued expenses	$ 10,926	$ 7,254

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
Long-term debt	$ 15,000	$ 15,000
Less debt issuance costs and discount, net of current portion	(54)	(192)
Long-term debt, net of long-term portion of debt issuance costs and discount	14,946	14,808
Less current portion of long-term debt	(2,500)
Long-term debt, net	12,446	$ 14,808
Current portion of long-term debt	2,500
Less current portion of debt issuance costs and discount	(62)
Current portion of long-term debt, net	$ 2,438

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details 3) - USD ($)		1 Months Ended			12 Months Ended
	Jul. 14, 2017	Sep. 30, 2018	May 31, 2018	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 24, 2014	Jul. 30, 2014
Current accrued expenses
Loss on extinguishment of debt						$ (118,000)
Cash-collateralized irrevocable standby letter of credit			$ 200,000
Future minimum payments					$ 41,221,000
Payment for early termination of lease					2,500,000
Rent expense					2,300,000	2,300,000	$ 1,300,000
Minimum annual payments to maintain cancelable licenses					$ 300,000
Early termination payment description					The Company maintains the right to terminate the lease after October 2025, subject to our delivery to the landlord of twelve months’ prior written notice and an early termination payment of $2.5 million
Non-Cancelable Operating Lease
Current accrued expenses
Lease extended term			2028
Tenant improvement allowance			$ 1,900,000
Construction related cost					$ 100,000
Future minimum payments					41,200,000
Payment for early termination of lease					$ 2,500,000
Lease expiration period					2025-10
Sublease Lease
Current accrued expenses
Future minimum payments					$ 0
Sublease expiration date					2017-09
Term B Loan \| Warrant
Current accrued expenses
Fair values of warrants issued	$ 200,000
SVB Loan Amendment
Current accrued expenses
First amendment effective date					Jul. 14, 2017
Debt instrument, variable rate description					The Company’s long-term debt bears interest at a floating per annum rate equal to the greater of (i) 3.50% above the Prime Rate (as defined in the SVB Loan Amendment) or (ii) 7.25%; provided, however, that in no event shall such interest rate exceed 8.25%.
Debt instrument interest only payment period					through July 31, 2019
SVB Loan Amendment \| Greater of 7.25%
Current accrued expenses
Debt instrument, floating rate					7.25%
SVB Loan Amendment \| Minimum \| Prime Rate \| Greater of 3.50% Above Prime Rate
Current accrued expenses
Debt instrument, floating rate					3.50%
SVB Loan Amendment \| Maximum
Current accrued expenses
Debt instrument, floating rate					8.25%
SVB Loan Amendment \| 2017 Term Loan
Current accrued expenses
Principal amount	15,000,000
Cash proceeds from remaining portion of debt	$ 7,500,000
Debt instrument, maturity date	Jan. 01, 2022
Debt instrument, variable rate description					The 2017 Term Loan matures on January 1, 2022 (the Term Loan Maturity Date) and bears interest at a floating per annum rate equal to the greater of (i) 3.50% above the Prime Rate (as defined in the SVB Loan Amendment) or (ii) 7.25%; provided, however, that in no event shall such interest rate exceed 8.25%.
Debt instrument, interest payment terms					Interest is payable on a monthly basis on the first day of each month.
Debt instrument, frequency of periodic payment					monthly
Interest rate (as a percent)					8.25%
Debt instrument interest only payment period					August 1, 2017 through January 1, 2019
Debt instrument extended interest only payment period					January 1, 2019 through and including to July 31, 2019
Final payment fee					7.50%
Final payment fee (amounts in dollars)					$ 1,100,000
Effective interest rate	10.20%
Loss on extinguishment of debt						(100,000)
Aggregate interest expense					$ 1,700,000	800,000
SVB Loan Amendment \| 2017 Term Loan \| 2017 Warrant
Current accrued expenses
Exercise price (in dollars per share)	$ 3.28
Warrants expiration date	2024-07
Fair values of warrants issued	$ 200,000
Warrants issued to cashless exercised in exchange		67,952
SVB Loan Amendment \| 2017 Term Loan \| Product Development Milestone Achievement
Current accrued expenses
Number of equal monthly installments to repay principal and accrued interest	30 months
SVB Loan Amendment \| 2017 Term Loan \| Minimum
Current accrued expenses
Debt instrument, floating rate	7.25%
SVB Loan Amendment \| 2017 Term Loan \| Minimum \| Prime Rate
Current accrued expenses
Debt instrument, floating rate	3.50%
SVB Loan Amendment \| 2017 Term Loan \| Maximum
Current accrued expenses
Debt instrument, floating rate	8.25%
SVB Loan Amendment \| 2017 Term Loan \| Maximum \| 2017 Warrant
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion	91,463
Amended And Restated Loan And Security Agreement
Current accrued expenses
Aggregate interest expense						$ 500,000	$ 1,600,000
Amended And Restated Loan And Security Agreement \| Warrants Expiration Period January 2019
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion					5,305
Warrants expiration date					2019-01
Amended And Restated Loan And Security Agreement \| Warrants Expiration Period August 2021
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion					30,769
Warrants expiration date					2021-08
Amended And Restated Loan And Security Agreement \| Warrant
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion					36,074
Exercise price (in dollars per share)					$ 7.21
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. 01, 2018
Final payment fee					7.50%
Final payment fee (amounts in dollars)					$ 800,000
Amended And Restated Loan And Security Agreement \| Term B Loan
Current accrued expenses
Debt instrument, maturity date					Jun. 01, 2018
Final payment fee					7.50%
Final payment fee (amounts in dollars)					$ 800,000
Amended And Restated Loan And Security Agreement \| Term B Loan \| 2014 Warrants
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion					98,039
Exercise price (in dollars per share)					$ 4.08
Warrants expiration date					2021-12
Warrants issued to cashless exercised in exchange				34,149
Amended And Restated Loan And Security Agreement \| Term B Loan \| 2014 Warrants \| Warrants Expiration Period December 2021
Current accrued expenses
Warrants to purchase shares of common stock issued on conversion					49,020
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

Accrued Expenses, Long-Term Debt, Commitments and Contingencies (Details 4) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Long-Term Debt
Years Ending December 31, 2019	$ 3,720
Years Ending December 31, 2020	6,818
Years Ending December 31, 2021	6,313
Years Ending December 31, 2022	1,629
Long-term debt	18,480
Less interest	(2,355)
Less additional payments due upon maturity	(1,125)
Less unamortized debt discount and debt issuance costs	(116)
Less current portion of long-term debt, net	(2,438)
Long–term debt, net of current portion	12,446	$ 14,808
Operating Leases
Years Ending December 31, 2019	3,019
Years Ending December 31, 2020	3,761
Years Ending December 31, 2021	3,873
Years Ending December 31, 2022	3,989
Years Ending December 31, 2023	4,109
Thereafter	22,470
Total	41,221
Less current portion of long-term debt, net	(2,438)
Total
Years Ending December 31, 2019	6,739
Years Ending December 31, 2020	10,579
Years Ending December 31, 2021	10,186
Years Ending December 31, 2022	5,618
Years Ending December 31, 2023	4,109
Thereafter	22,470
Total	$ 59,701

Convertible Preferred Stock and Stockholders' Equity (Details) - USD ($)			1 Months Ended			12 Months Ended			64 Months Ended
	Jul. 14, 2017	Sep. 13, 2013	Sep. 30, 2018	Nov. 30, 2016	Aug. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2018	Jan. 31, 2019	Jan. 31, 2018	May 31, 2017	May 02, 2017	May 10, 2016	Dec. 31, 2015	Aug. 28, 2013
Convertible preferred stock
Net proceeds from issuance of shares after related cash costs						$ 2,693,000	$ 205,000	$ 186,000
Preferred stock, par value (in dollars per share)						$ 0.001	$ 0.001		$ 0.001
Dividends declared						$ 0
Shares reserved for issuance						26,065,733	24,395,281		26,065,733
Stock purchases under the plan (in shares)									0
SVB Loan Amendment
Convertible preferred stock
Warrants to purchase shares of common stock issued on conversion	91,463
Warrants expiration date	2024-07
Employee And Non Employee Stock Option
Convertible preferred stock
Total intrinsic value of stock options exercised						$ 5,500,000
Cash received upon exercise of options (in dollars per share)						$ 2,700,000
Employee Stock
Convertible preferred stock
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
Restricted Stock Units (RSUs)
Convertible preferred stock
Shares reserved for issuance						188,625	212,625		188,625
Expected recognition period of unrecognized compensation cost						9 months 18 days	1 year 9 months 18 days	2 years 9 months 18 days
Unrecognized compensation cost related to unvested restricted shares						$ 400,000	$ 900,000	$ 1,800,000	$ 400,000
Stock Option And Incentive Plan 2013
Convertible preferred stock
Shares reserved for issuance												2,500,000				1,020,000
Additional shares authorized (as a percent)																4.00%
Stock Option And Incentive Plan 2013 \| Employee And Non Employee Stock Option
Convertible preferred stock
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
Term of stock awards						10 years
Outstanding options						6,980,581	5,458,043	3,910,350	6,980,581						2,587,474
Granted						3,251,980	2,522,920	2,245,240
Unrecognized compensation cost related to outstanding options						$ 15,900,000	$ 5,800,000	$ 4,900,000	$ 15,900,000
Expected recognition period of unrecognized compensation cost						3 years 1 month 6 days	2 years 7 months 6 days	2 years 7 months 6 days
Stock Option And Incentive Plan 2013 \| Employee And Non Employee Stock Option \| Vesting Based On Performance
Convertible preferred stock
Outstanding options						0	73,600	73,600	0
Aggregate grant date fair value						$ 0	$ 100,000	$ 100,000
Stock Option And Incentive Plan 2013 \| Employee and Directors Stock Option
Convertible preferred stock
Granted						3,300,000	2,500,000	2,200,000
Weighted-average grant date fair value per share of employee options granted						$ 8.28	$ 2.29	$ 1.80
Inducement Plan
Convertible preferred stock
Shares reserved for issuance						379,178	100,000		379,178					500,000
Additional shares reserved for issuance											400,000
Inducement Plan \| Subsequent Event
Convertible preferred stock
Additional shares reserved for issuance										200,000
Common Stock
Convertible preferred stock
Common stock issued						10,648,149	10,953,750
Warrant
Convertible preferred stock
Shares reserved for issuance						85,094	225,756		85,094
Warrant \| SVB Loan Amendment
Convertible preferred stock
Exercise price (in dollars per share)	$ 3.28
Warrant \| Term B Loan
Convertible preferred stock
Fair values of warrants issued	$ 200,000
2017 Warrant \| SVB Loan Amendment
Convertible preferred stock
Warrants issued to cashless exercised in exchange			67,952
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). The terms of the CoD prohibited Redmile 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 could 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%. On May 2, 2017, the Company’s stockholders approved the issuance of up to an aggregate of 14,097,745 shares of common stock upon the conversion of the outstanding shares of Class A Preferred. As a result, Redmile has the right to increase the Redmile Percentage Limitation to any percentage in excess of 19.99% at its election.
Non-Voting Class A Preferred Stock \| Maximum
Convertible preferred stock
Number of shares to be issued upon conversion													14,097,745
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
Common stock issued				7,236,837	5,250,000
Net proceeds from issuance of shares after related cash costs				$ 54,900,000	$ 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 and Stockholders' Equity (Details 2) - Stock Option And Incentive Plan 2013 - Employee And Non Employee Stock Option - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Options
Balance at the beginning of the period	5,458,043	3,910,350	2,587,474
Granted	3,251,980	2,522,920	2,245,240
Exercised	(694,830)	(83,220)	(136,368)
Cancelled	(1,034,612)	(892,007)	(785,996)
Balance at the end of the period	6,980,581	5,458,043	3,910,350	2,587,474
Vested and expected to vest at the end of the period	6,916,914
Exercisable at the end of the period	3,430,415
Weighted-Average Price
Balance at the beginning of the period	$ 3.52	$ 3.77	$ 4.59
Granted	8.30	3.09	2.62
Exercised	3.88	2.79	1.44
Cancelled	4.36	3.50	3.58
Balance at the end of the period	5.58	$ 3.52	$ 3.77	$ 4.59
Vested and expected to vest at the end of the period	5.59
Exercisable at the end of the period	$ 4.24
Weighted Average Remaining Contractual Term
Outstanding at the end of the period	7 years 10 months 13 days	7 years 11 months 26 days	8 years 3 months 10 days	6 years 11 months 1 day
Vested and expected to vest at the end of the period	7 years 10 months 9 days
Exercisable at the end of the period	7 years
Aggregate Intrinsic Value
Outstanding at the end of the period	$ 51,497	$ 14,754	$ 682	$ 1,486
Vested and expected to vest at the end of the period	50,985
Exercisable at the end of the period	$ 29,470

Convertible Preferred Stock and Stockholders' Equity (Details 3) - Restricted Stock Units (RSUs) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Number of Restricted Stock Units
Balance at the beginning of the period	212,625	525,250	525,250
Vested		(225,125)
Cancelled	(24,000)	(87,500)
Balance at the end of the period	188,625	212,625	525,250	525,250
Expected to vest at the end of the period	180,625
Weighted-Average Grant Date Fair Value per Share
Balance at the beginning of the period	$ 4.89	$ 4.89	$ 4.89
Vested		4.89
Cancelled	4.89	4.89
Balance at the end of the period	4.89	$ 4.89	$ 4.89	$ 4.89
Expected to vest at the end of the period	$ 4.89
Weighted Average Remaining Vesting Period
Outstanding at the end of the period	9 months 18 days	1 year 9 months 18 days	2 years 9 months 18 days	3 years 9 months 18 days
Expected to vest at the end of the period	9 months 18 days
Aggregate Intrinsic Value
Outstanding at the end of the period (in dollars)	$ 2,420	$ 1,299	$ 1,318	$ 1,770
Restricted Stock Units expected to vest at December 31, 2018	$ 2,317

Convertible Preferred Stock and Stockholders' Equity (Details 4) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Convertible preferred stock
Total stock-based compensation expense	$ 6,293	$ 3,606	$ 3,184
Research And Development
Convertible preferred stock
Total stock-based compensation expense	3,654	2,095	1,802
General And Administrative
Convertible preferred stock
Total stock-based compensation expense	$ 2,639	$ 1,511	$ 1,382

Convertible Preferred Stock and Stockholders' Equity (Details 5)		12 Months Ended
	Jul. 14, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Warrant
Weighted-average assumptions to determine fair value of stock options
Risk–free interest rate	2.10%
Expected volatility	88.00%
Expected term (in years)	7 years
Expected dividend yield	0.00%
Employee Stock Option
Weighted-average assumptions to determine fair value of stock options
Risk–free interest rate		2.50%	2.00%	1.60%
Expected volatility		79.30%	90.10%	79.90%
Expected term (in years)		6 years	6 years	6 years
Expected dividend yield		0.00%	0.00%	0.00%
Non Employee Stock Option
Weighted-average assumptions to determine fair value of stock options
Risk–free interest rate		2.70%	2.10%	1.50%
Expected volatility		79.70%	87.40%	83.10%
Expected term (in years)		7 years 10 months 24 days	8 years 6 months	6 years 4 months 24 days
Expected dividend yield		0.00%	0.00%	0.00%

Convertible Preferred Stock and Stockholders' Equity (Details 6) - shares	Dec. 31, 2018	Dec. 31, 2017	May 10, 2016	Sep. 13, 2013
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance	26,065,733	24,395,281
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
Inducement Plan
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance	379,178	100,000	500,000
Employee Stock Option
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance	6,980,581	5,458,043
Stock Compensation Plan
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance	3,605,510	3,572,112
Restricted Stock Units (RSUs)
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance	188,625	212,625
Employee Stock
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance	729,000	729,000		729,000
Warrant
Weighted-average assumptions to determine fair value of stock options
Shares reserved for issuance	85,094	225,756

Income Taxes (Details) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of the Company's expected federal income tax provision (benefit) to the actual income tax provision
Tax computed at federal statutory rate	$ (13,985)	$ (14,603)	$ (11,377)
State tax, net of federal tax benefit	(1,620)	(1,315)	(2,089)
Permanent differences	22	795	292
Stock compensation	(307)	539	968
R&D tax credits	(3,301)	(2,934)	(971)
Reserve for uncertain tax positions	1,160	1,326	2,076
Tax attribute limitation			54
Tax Cuts and Jobs Act		25,280
Other	304	46	(74)
Valuation allowance	17,727	(9,134)	$ 11,121
Deferred tax assets:
Section 59e amortization	19,069	14,365
Net operating losses	30,981	27,699
R&D tax credits	9,163	5,421
Depreciation and amortization	1,653	581
Deferred revenue	3,906	594
Stock compensation	1,482	876
Other	1,106	96
Deferred tax assets	67,360	49,632
Valuation allowance	$ (67,360)	$ (49,632)

Income Taxes (Details 2) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details 2) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 67,360	$ 49,632
U.S. Federal
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 136,800
Net operating loss carryforward expiration year	2027
California
Operating Loss Carryforwards [Line Items]
Net operating loss carryforwards	$ 137,500
Net operating loss carryforward expiration year	2028

Income Taxes (Details 3) - USD ($) $ in Millions	12 Months Ended
Income Taxes (Details 3) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Tax Credit Carryforward [Line Items]
Cumulative changes in ownership percentage	50.00%
Period of change in ownership	3 years
Californian
Tax Credit Carryforward [Line Items]
Income tax examination, year under examination	2015
Canadian
Tax Credit Carryforward [Line Items]
Income tax examination, year under examination	2014
U.S. Federal
Tax Credit Carryforward [Line Items]
Income tax examination, year under examination	2014
U.S. Federal \| Research and development
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 8.2
Tax credit carryforward expiration year		2035
California \| Research and development
Tax Credit Carryforward [Line Items]
Tax credit carryforwards	$ 5.4

Income Taxes (Details 4) - USD ($)	12 Months Ended
Income Taxes (Details 4) - USD ($)	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in the Company's unrecognized tax benefits
Balance at the beginning of the period	$ 11,800,000	$ 7,730,000	$ 3,869,000
Increase related to current year tax positions	1,798,000	4,077,000	2,268,000
Increase related to prior year tax positions	148,000	6,000	1,625,000
Decrease related to prior year tax positions	(199,000)	(13,000)	(32,000)
Balance at the end of the period	13,547,000	$ 11,800,000	$ 7,730,000
Income Taxes
Unrecognized tax benefit	0
Unrecognized tax benefits that, if recognized, would reduce the effective tax rate	$ 0

Income Taxes (Details 5) - USD ($) $ in Thousands	12 Months Ended
Income Taxes (Details 5) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Excess tax benefit previously not recognized	$ 13,547	$ 11,800	$ 7,730	$ 3,869
Corporate tax rate	21.00%	34.00%
Remeasurement of deferred tax assets and liabilities		$ 25,300
ASU No. 2016-09
Income Tax Contingency [Line Items]
Excess tax benefit previously not recognized	$ 100

Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Collaboration revenue	$ 1,661	$ 1,026	$ 1,027	$ 1,026	$ 1,027	$ 1,026	$ 1,026	$ 1,027	$ 4,740	$ 4,106	$ 4,402
Type of Revenue [Extensible List]	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember	us-gaap:LicenseMember
Total operating expenses	$ 18,402	$ 17,718	$ 20,632	$ 15,080	$ 13,271	$ 11,366	$ 10,596	$ 10,998	$ 71,832	$ 46,231	$ 36,365
Net loss	$ (16,027)	$ (16,782)	$ (19,654)	$ (14,135)	$ (12,497)	$ (10,684)	$ (9,645)	$ (10,126)	$ (66,598)	$ (42,952)	$ (33,462)
Basic and diluted net loss per common share (in dollars per share)	$ (0.25)	$ (0.31)	$ (0.37)	$ (0.27)	$ (0.29)	$ (0.26)	$ (0.23)	$ (0.24)	$ (1.19)	$ (1.02)	$ (1.05)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Employee Benefits (Details) - USD ($)		12 Months Ended
Employee Benefits (Details) - USD ($)	Jan. 02, 2009	Dec. 31, 2018
Compensation And Retirement Disclosure [Abstract]
Minimum age of employees	21 years
Matching contributions under 401(k) plan		$ 0