Mirati Therapeutics (MRTX) 10-Q 7 May 18 2018 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2018	Apr. 30, 2018
Document and Entity Information
Entity Registrant Name	Mirati Therapeutics, Inc.
Entity Central Index Key	1,576,263
Document Type	10-Q
Document Period End Date	Mar. 31, 2018
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		29,052,131
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q1

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Current assets
Cash and cash equivalents	$ 20,567	$ 107,703
Short-term investments	128,085	43,134
Other current assets	4,421	4,922
Total current assets	153,073	155,759
Property and equipment, net	484	525
Other long-term assets	987	962
Total assets	154,544	157,246
Current liabilities
Accounts payable and accrued liabilities	15,761	13,644
Deferred revenue and other current liabilities	249	0
Total current liabilities	16,010	13,644
Other liability	693
Other Liabilities, Noncurrent	400	314
Total liabilities	16,703	13,958
Stockholders’ equity
Preferred stock, $0.001 par value, 10,000,000 shares authorized; none issued and outstanding at both March 31, 2018 and December 31, 2017	0	0
Common stock, $0.001 par value; 100,000,000 shares authorized; 29,025,834 and 28,622,886 issued and outstanding at March 31, 2018 and December 31, 2017, respectively	29	29
Additional paid-in capital	603,957	594,407
Accumulated other comprehensive income	9,191	9,479
Accumulated deficit	(475,336)	(460,627)
Total stockholders’ equity	137,841	143,288
Total liabilities and stockholders’ equity	$ 154,544	$ 157,246

CONDENSED CONSOLIDATED BALANCE3

CONDENSED CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Mar. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized (in shares)	100,000,000	100,000,000
Common stock, shares issued (in shares)	29,025,834	28,622,886
Common stock, shares outstanding (in shares)	29,025,834	28,622,886

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
License and collaboration revenues	$ 9,467	$ 0
Total revenue	9,467	0
Expenses
Research and development	19,659	14,397
General and administrative	5,154	3,693
Total operating expenses	24,813	18,090
Loss from operations	(15,346)	(18,090)
Other income, net	637	244
Net loss	(14,709)	(17,846)
Unrealized gain (loss) on available-for-sale investments	(288)	71
Comprehensive loss	$ (14,997)	$ (17,775)
Basic and diluted net loss per share	$ (0.51)	$ (0.73)
Weighted average number of shares used in computing net loss per share, basic and diluted	28,843,578	24,383,941

CONDENSED CONSOLIDATED STATEME5

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Operating activities:
Net loss	$ (14,709)	$ (17,846)
Non-cash adjustments reconciling net loss to operating cash flows:
Depreciation	41	45
Amortization of premium on investments	(162)	(71)
Share-based compensation expense	3,660	1,766
Changes in operating assets and liabilities:
Other current assets	502	704
Other long-term assets	25	(710)
Accounts payable, accrued liabilities, deferred revenue and other liabilities	2,745	(3,540)
Cash flows used in operating activities	(7,948)	(18,232)
Investing activities:
Purchases of short-term investments	(102,820)	(63,310)
Disposal and maturities of short-term investments	17,742	22,100
Cash flows used in investing activities	(85,078)	(41,210)
Financing activities:
Proceeds from sale of common stock, net	0	66,816
Proceeds from exercise of common stock options and warrants	5,890	0
Cash flows provided by financing activities	5,890	66,816
Decrease in cash and cash equivalents	(87,136)	7,374
Cash and cash equivalents, beginning of period	107,703	22,383
Cash and cash equivalents, end of period	20,567	29,757
Supplemental disclosures of non-cash investing activities:
Fixed asset additions included within accounts payable	$ 0	$ 54

Description of Business

Description of Business	3 Months Ended
	Mar. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Description of Business	Description of Business Mirati Therapeutics, Inc. ("Mirati" or the "Company") is a clinical-stage oncology company developing product candidates to address the genetic, epigenetic and immunological promoters of cancer. The Company was incorporated under the laws of the State of Delware on April 29, 2013 as Mirati Therapeutics, Inc. and is located in San Diego, California. The Company has a wholly owned subsidiary in Canada, MethylGene, Inc., and operates in one business segment, primarily in the United States. The Company's common stock has been listed on the NASDAQ Capital Market since July 15, 2013 under the ticker symbol "MRTX."

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The unaudited condensed consolidated financial statements contained in this Quarterly Report on Form 10-Q have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission ("SEC") and, therefore, certain information and disclosures normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been omitted. In the opinion of management, the information reflects all adjustments necessary to make the results of operations for the interim periods a fair statement of such operations. All such adjustments are of a normal recurring nature. Interim results are not necessarily indicative of results for the full year. The condensed consolidated balance sheet at December 31, 2017 has been derived from the audited consolidated financial statements at that date, but does not include all information and footnotes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the audited financial statements included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2017 . Use of Estimates The preparation of the Company's unaudited condensed consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. Reported amounts and note disclosures reflect the overall economic conditions that are most likely to occur and anticipated measures management intends to take. Actual results could differ materially from those estimates. Estimates and assumptions are reviewed quarterly. Any revisions to accounting estimates are recognized in the period in which the estimates are revised and in any future periods affected. Cash, Cash Equivalents and Short-term Investments Cash and cash equivalents consist of cash and highly liquid securities with original maturities at the date of acquisition of ninety days or less. Investments with an original maturity of more than ninety days are considered short-term investments and have been classified by management as available-for-sale. These investments are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund its operations, as necessary. Such investments are carried at fair value, and the unrealized gains and losses are reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity until realized. Realized gains and losses from the sale of available-for-sale securities, if any, are determined on a specific identification basis. Concentration of Credit Risk The Company invests its excess cash in accordance with its investment policy. The Company's investments are comprised primarily of commercial paper and debt instruments of financial institutions, corporations, U.S. government-sponsored agencies and the U.S. Treasury. The Company mitigates credit risk by maintaining a diversified portfolio and limiting the amount of investment exposure as to institution, maturity and investment type. Financial instruments that potentially subject the Company to significant credit risk consist principally of cash equivalents and short-term investments. Revenue Recognition Effective January 1, 2017, the Company adopted Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers , using the full retrospective transition method. As the Company did not have any revenue contracts prior to the first quarter of 2018, an adjustment to prior periods under this method was not applicable. This standard applies to all contracts with customers, except for contracts that are within the scope of other standards, such as leases, insurance, collaboration arrangements and financial instruments. Under Topic 606, an entity recognizes revenue when its customer obtains control of promised goods or services, in an amount that reflects the consideration that the entity expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that an entity determines are within the scope of Topic 606, the entity performs the following five steps: (i) identify the contract(s) 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 in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the entity will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once the contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within each contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. See footnote 9 for a complete discussion of the revenue recognition for the Company’s collaboration and license agreement. Net loss per share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for common share equivalents. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and common share equivalents outstanding for the period. Common share equivalents outstanding, determined using the treasury stock method, are comprised of shares that may be issued under the Company’s stock option and warrant agreements. The following table presents the weighted average number of common share equivalents, calculated using the treasury stock method, not included in the calculation of diluted net loss per share due to the anti-dilutive effect of the securities: Three Months Ended March 31, 2018 2017 Common stock options 1,458,774 — Common stock warrants 11,395,851 6,450,612 Total 12,854,625 6,450,612

Recent Accounting Pronouncement

Recent Accounting Pronouncements	3 Months Ended
	Mar. 31, 2018
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recent Accounting Pronouncements	Recently Adopted and Recently Issued Accounting Pronouncements From time to time, new accounting pronouncements are issued by the Financial Accounting Standards Board ("FASB") or other standard setting bodies that are adopted by the Company as of the specified effective date. Recently Adopted Accounting Pronouncements In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation, to provide clarity and reduce both 1) diversity in practice and 2) cost and complexity when applying the guidance in Topic 718 to a change in the terms or conditions of a share-based payment award. ASU 2017-09 provided guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under Topic 718. The amendments in ASU 2017-09 were effective for fiscal and interim reporting periods in fiscal years beginning after December 15, 2017. The amendments in ASU 2017-09 should be applied prospectively to an award modified on or after the adoption date. Effective January 1, 2018, the Company adopted the provisions of ASU 2017-09. The adoption did not have a material impact on the Company's consolidated financial statements or related financial statement disclosure. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The new guidance enhanced the reporting model for financial instruments and includes amendments to address aspects of recognition, measurement, presentation and disclosure. The update to the standard was effective for public companies for interim and annual periods beginning after December 15, 2017. Effective January 1, 2018, the Company adopted the provisions of ASU 2016-01. The adoption did not have a material impact on the Company's consolidated financial statements or related financial statement disclosure. Recently Issued Accounting Pronouncements In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features, (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Non-controlling Interests with a Scope Exception. The ASU allows companies to exclude a down round feature when determining whether a financial instrument (or embedded conversion feature) is considered indexed to the entity’s own stock. As a result, financial instruments (or embedded conversion features) with down round features may no longer be required to be classified as liabilities. A company will recognize the value of a down round feature only when it is triggered and the strike price has been adjusted downward. For equity-classified freestanding financial instruments, such as warrants, an entity will treat the value of the effect of the down round, when triggered, as a dividend and a reduction of income available to common shareholders in computing basic earnings per share. For convertible instruments with embedded conversion features containing down round provisions, entities will recognize the value of the down round as a beneficial conversion discount to be amortized to earnings. The guidance in ASU 2017-11 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted, and the guidance is to be applied using a full or modified retrospective approach. The Company does not anticipate that the adoption of ASU 2017-11 will have a material impact on its consolidated financial statements unless a transaction occurs that would need to be evaluated under this guidance at which time the Company will assess the impact of this standard. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous GAAP. ASU 2016-02 requires that a lessee should recognize a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term on the balance sheet. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 (including interim periods within those periods) using a modified retrospective approach and early adoption is permitted. The Company will adopt ASU 2016-02 in the first quarter of 2019. Although the Company is in the process of evaluating the impact of adoption of the ASU on its consolidated financial statements, the Company currently believes the most significant changes will be related to the recognition of new right-of-use assets and lease liabilities on the Company's balance sheet for real estate operating leases.

Short-term Investments

Short-term Investments	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Short-term Investments	Short-term Investments The following tables summarize the Company's short-term investments (dollars in thousands): As of March 31, 2018 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 2 year or less $ 86,479 $ — $ (260 ) $ 86,219 Commercial paper 1 year or less 41,936 — (70 ) 41,866 $ 128,415 $ — $ (330 ) $ 128,085 As of December 31, 2017 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 1 year or less $ 24,264 $ — $ (23 ) $ 24,241 Commercial paper 1 year or less 18,912 — (19 ) 18,893 $ 43,176 $ — $ (42 ) $ 43,134 Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At March 31, 2018 , the Company did not have any securities in material unrealized loss positions. The Company reviews its investments to identify and evaluate investments that have an indication of possible other-than-temporary impairment. Factors considered in determining whether a loss is other-than-temporary include the length of time and extent to which fair value has been less than the cost basis, the financial condition and near-term prospects of the investee, and the Company’s intent and ability to hold the investment for a period of time sufficient to allow for any anticipated recovery in market value. The Company does not intend to sell any investments prior to recovery of their amortized cost basis for any investments in an unrealized loss position.

Fair value measurements

Fair value measurements	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Fair value measurements	Fair value measurements The Company has certain financial assets and liabilities recorded at fair value which have been classified as Level 1 or 2 within the fair value hierarchy as described in the accounting standards for fair value measurements. The authoritative guidance for fair value measurements defines fair value as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or the most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Market participants are buyers and sellers in the principal market that are (i) independent, (ii) knowledgeable, (iii) able to transact, and (iv) willing to transact. The guidance prioritizes the inputs used in measuring fair value into the following hierarchy: • Level 1- Quoted prices (unadjusted) in active markets for identical assets or liabilities; • Level 2- Inputs other than quoted prices included within Level 1 that are either directly or indirectly observable; and • Level 3- Unobservable inputs in which little or no market activity exists, therefore requiring an entity to develop its own assumptions about the assumptions that market participants would use in pricing. The following tables summarize the assets measured at fair value on a recurring basis (in thousands): March 31, 2018 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 3,721 $ 3,721 $ — $ — Money market funds 16,846 16,846 — — Total cash and cash equivalents 20,567 20,567 — — Short-term investments: Corporate debt securities 86,219 — 86,219 — Commercial paper 41,866 — 41,866 — Total short-term investments 128,085 — 128,085 — Total $ 148,652 $ 20,567 $ 128,085 $ — December 31, 2017 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 1,026 $ 1,026 $ — $ — Money market funds 106,677 106,677 — — Total cash and cash equivalents 107,703 107,703 — — Short-term investments: Corporate debt securities 24,241 — 24,241 — Commercial paper 18,893 — 18,893 — Total short-term investments 43,134 — 43,134 — Total $ 150,837 $ 107,703 $ 43,134 $ — The Company’s investments in Level 1 assets are valued based on publicly available quoted market prices for identical securities as of March 31, 2018 and December 31, 2017 . The Company determines the fair value of Level 2 related securities with the aid of valuations provided by third parties using proprietary valuation models and analytical tools. These valuation models and analytical tools use market pricing or prices for similar instruments that are both objective and publicly available, including matrix pricing or reported trades, benchmark yields, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids and/or offers. There were no transfers between fair value measurement levels during the three months ended March 31, 2018 or the year ended December 31, 2017 .

Other current assets and other

Other current assets and other long-term assets	3 Months Ended
	Mar. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other current assets and other long-term assets	Other current assets and other long-term assets Other current assets consisted of the following (in thousands): March 31, December 31, 2018 2017 Prepaid expenses $ 2,693 $ 3,085 Deposits and other receivables 1,325 1,600 Interest receivable 403 237 $ 4,421 $ 4,922 The other long-term assets balance consisted of $1.0 million in deposits paid in conjunction with the Company's research and development activities at each period March 31, 2018 and December 31, 2017 , respectively.

Property and equipment, net

Property and equipment, net	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Property and equipment, net	Property and equipment, net Property and equipment consisted of the following (in thousands): March 31, December 31, 2018 2017 Computer equipment $ 329 $ 329 Office and other equipment 301 301 Laboratory equipment 643 643 Leasehold improvements 63 63 Gross property and equipment 1,336 1,336 Less: Accumulated depreciation (852 ) (811 ) Property and equipment, net $ 484 $ 525 The Company incurred immaterial depreciation expense for both the three months ended March 31, 2018 and 2017 .

Accounts payable and accrued li

Accounts payable and accrued liabilities	3 Months Ended
	Mar. 31, 2018
Payables and Accruals [Abstract]
Accounts payable and accrued liabilities	Accounts payable, accrued liabilities and long-term liabilities Accounts payable and accrued liabilities consisted of the following (in thousands): March 31, December 31, 2018 2017 Accounts payable $ 4,731 $ 4,344 Accrued clinical, development and other expenses 9,058 6,279 Accrued compensation and benefits 1,972 3,021 $ 15,761 $ 13,644 The long-term liabilities balance of $0.7 million as of March 31, 2018 consisted of $0.3 million in deferred revenue and $0.4 million in other liabilities. As of December 31, 2017 the long-term liabilities balance consisted of $0.3 million in other liabilities.

Collaboration and License Agree

Collaboration and License Agreement	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Collaboration and License Agreement	Agreement Terms of Agreement On January 7, 2018, the Company and BeiGene Ltd, ("BeiGene") entered into a Collaboration and License Agreement (the “Agreement”), pursuant to which the Company and BeiGene agreed to collaboratively develop sitravatinib in Asia (excluding Japan and certain other countries), Australia and New Zealand (the “Licensed Territory”). BeiGene is considered a related party as the Company and BeiGene have a common investor. Under the Agreement, the Company granted BeiGene an exclusive license to develop, manufacture and commercialize sitravatinib in the Licensed Territory, with Mirati retaining exclusive rights for the development, manufacture and commercialization of sitravatinib outside the Licensed Territory. As consideration for the rights granted to BeiGene under the Agreement, BeiGene paid the Company a non-refundable, non-creditable upfront fee of $10.0 million . BeiGene is also required to make milestone payments to the Company of up to an aggregate of $123.0 million upon the first achievement of specified clinical, regulatory and sales milestones. The Agreement additionally provides that BeiGene is obligated to pay to the Company royalties at tiered percentage rates ranging from mid-single digits to twenty percent on annual net sales of licensed products in the Licensed Territory, subject to reduction under specified circumstances. The Agreement also provides that the Company will supply BeiGene with sitravatinib for use in BeiGene’s development activities in the Licensed Territory. The Agreement will terminate upon the expiration of the last royalty term for the licensed products, which is the latest of (i) the date of expiration of the last valid patent claim related to the licensed products under the Agreement, (ii) 10 years after the first commercial sale of a licensed product and (iii) the expiration of any regulatory exclusivity as to a licensed product. BeiGene may terminate the Agreement at any time by providing 60 days prior written notice to the Company. Either party may terminate the Agreement upon a material breach by the other party that remains uncured following 60 days after the date of written notice of such breach or upon certain bankruptcy events. In addition, the Company may terminate the Agreement upon written notice to BeiGene under specified circumstances if BeiGene challenges the licensed patent rights. Revenue Recognition The Company evaluated the Agreement under Topic 606. In determining the appropriate amount of revenue to be recognized as the Company fulfills its obligations under the Agreement, the Company performed the following steps: (i) identified the promised goods or services in the contract; (ii) determined whether the promised goods or services are performance obligations including whether they are distinct in the context of the contract; (iii) measured the transaction price, including any constraints on variable consideration; (iv) allocated the transaction price to the performance obligations; and (v) recognizes revenue when (or as) the Company satisfies each performance obligation. The Company determined the transaction price is equal to the up-front fee of $10.0 million . The transaction price was allocated to the performance obligations on the basis of the relative stand-alone selling price estimated for each performance obligation. In estimating the stand-alone selling price for each performance obligation, the Company developed assumptions that require judgment and included forecasted revenues, expected development timelines, discount rates, probabilities of technical and regulatory success and costs for manufacturing clinical supplies. A description of the performance obligations identified under the Agreement, as well as the amount of revenue allocated to each performance obligation, follows: Licenses of Intellectual Property. The license to the Company’s intellectual property, bundled with the associated know-how, represents a distinct performance obligation. The license and associated know-how was transferred to BeiGene during the three months ended March 31, 2018, therefore the Company recognized revenue related to this performance obligation in the amount of $9.5 million during the three months ended March 31, 2018. Manufacturing Supply Services. The Company's initial obligation to supply sitravatinb for clinical development in the Licensed Territory represents a distinct performance obligation. As such, the Company will defer $0.5 million of revenue related to the manufacturing supply services, and will recognize revenue when BeiGene obtains control of the goods, upon delivery, and which is expected to occur in late 2018 and continue into 2020. The Company may also become responsible for manufacturing sitravatinib for clinical and commercial supply and will receive reimbursement that approximates stand-alone selling prices. Milestone Payments. The Company evaluated whether the milestones are considered probable of being reached and determined that since the milestone payments are not within the control of the Company or BeiGene (due to the requirement for regulatory approvals), the milestones are not considered probable of being achieved, therefore no revenue was recorded related to the milestones at the inception of the Agreement. At the end of each subsequent reporting period, the Company will re-evaluate the probability of achievement of each milestone and any related constraint, and if necessary, adjust its estimate of the overall transaction price. Any such adjustments are recorded on a cumulative catch-up basis, which would affect the reported amount of license and collaboration revenues in the period of adjustment. Royalties. As the license is deemed to be the predominant item to which sales-based royalties relate, the Company will recognize revenue when the related sales occur. No royalty revenue was recognized during the three months ended March 31, 2018. The following table presents a summary of the activity in the Company's contract liabilities during the three months ended March 31, 2018 (in thousands): Balance at Beginning of Period Additions Deductions Balance at End of Period Contract liabilities: Deferred revenue - current $ — $ 229 $ — $ 229 Deferred revenue - non-current — 304 — 304 Total contract liabilities: $ — $ 533 $ — $ 533

Warrants

Warrants	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Warrants	Warrants As of March 31, 2018 , the following warrants for common stock were issued and outstanding: Issue date Expiration date Exercise price Number of warrants outstanding January 11, 2017 None $ 0.001 7,258,263 November 20, 2017 None $ 0.001 4,137,999 11,396,262 During the three months ended March 31, 2018 and 2017, no warrants were exercised. Stockholders' Equity Share-based Compensation Total share-based compensation expense by statement of operations classification is presented below (in thousands): Three Months Ended March 31, 2018 2017 Research and development expense $ 1,493 $ 982 General and administrative expense 2,167 784 $ 3,660 $ 1,766 During the three months ended March 31, 2018 , 402,948 shares were issued pursuant to stock option exercises, generating net proceeds of $5.9 million . During the three months ended March 31, 2017 , no shares were issued pursuant to stock option exercises.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2018
Leases [Abstract]
Commitments and Contingencies	Commitments and Contingencies On June 24, 2014, the Company entered into a lease agreement for 18,000 square feet of completed office and laboratory space located in San Diego, California. The office space under the lease is the Company's corporate headquarters. The lease commenced in two phases (in July 2014 and March 2015) at a combined total initial monthly rent of $24,100 per month. The leased property is subject to a 3% annual rent increase following availability that results in the Company recording deferred rent over the term of the lease. In addition to such base monthly rent, the Company is obligated to pay certain customary amounts for its share of operating expenses and facility amenities. The original lease provided for expiration on January 31, 2018. On March 23, 2017, the Company entered into a First Amendment to Lease Agreement to amend the original lease agreement. This amendment extended the term of the original lease for one year through January 31, 2019. Subsequently, on April 5, 2018, the Company entered into a Second Amendment to Lease Agreement to extend the lease term through January 31, 2020. All other material terms and covenants from the original lease agreement remain unchanged. Future minimum payments required under the lease are summarized as follows (in thousands): Year Ending December 31: 2018 $ 210 2019 315 2020 26 Total minimum lease payments $ 551

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stockholders' Equity	Warrants As of March 31, 2018 , the following warrants for common stock were issued and outstanding: Issue date Expiration date Exercise price Number of warrants outstanding January 11, 2017 None $ 0.001 7,258,263 November 20, 2017 None $ 0.001 4,137,999 11,396,262 During the three months ended March 31, 2018 and 2017, no warrants were exercised. Stockholders' Equity Share-based Compensation Total share-based compensation expense by statement of operations classification is presented below (in thousands): Three Months Ended March 31, 2018 2017 Research and development expense $ 1,493 $ 982 General and administrative expense 2,167 784 $ 3,660 $ 1,766 During the three months ended March 31, 2018 , 402,948 shares were issued pursuant to stock option exercises, generating net proceeds of $5.9 million . During the three months ended March 31, 2017 , no shares were issued pursuant to stock option exercises.

Summary of Significant Accoun18

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The unaudited condensed consolidated financial statements contained in this Quarterly Report on Form 10-Q have been prepared in accordance with the rules and regulations of the Securities and Exchange Commission ("SEC") and, therefore, certain information and disclosures normally included in annual financial statements prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") have been omitted. In the opinion of management, the information reflects all adjustments necessary to make the results of operations for the interim periods a fair statement of such operations. All such adjustments are of a normal recurring nature. Interim results are not necessarily indicative of results for the full year. The condensed consolidated balance sheet at December 31, 2017 has been derived from the audited consolidated financial statements at that date, but does not include all information and footnotes required by U.S. GAAP for complete financial statements. These unaudited condensed consolidated financial statements should be read in conjunction with the audited financial statements included in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2017 .
Use of Estimates	Use of Estimates The preparation of the Company's unaudited condensed consolidated financial statements requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expenses during the reporting period. Reported amounts and note disclosures reflect the overall economic conditions that are most likely to occur and anticipated measures management intends to take. Actual results could differ materially from those estimates. Estimates and assumptions are reviewed quarterly. Any revisions to accounting estimates are recognized in the period in which the estimates are revised and in any future periods affected.
Cash and Cash Equivalents	Cash, Cash Equivalents and Short-term Investments Cash and cash equivalents consist of cash and highly liquid securities with original maturities at the date of acquisition of ninety days or less.
Short-term Investments	Investments with an original maturity of more than ninety days are considered short-term investments and have been classified by management as available-for-sale. These investments are classified as current assets, even though the stated maturity date may be one year or more beyond the current balance sheet date, which reflects management’s intention to use the proceeds from sales of these securities to fund its operations, as necessary.
Concentration of Credit Risk	Concentration of Credit Risk The Company invests its excess cash in accordance with its investment policy. The Company's investments are comprised primarily of commercial paper and debt instruments of financial institutions, corporations, U.S. government-sponsored agencies and the U.S. Treasury. The Company mitigates credit risk by maintaining a diversified portfolio and limiting the amount of investment exposure as to institution, maturity and investment type. Financial instruments that potentially subject the Company to significant credit risk consist principally of cash equivalents and short-term investments.
New accounting pronouncements	Recently Adopted Accounting Pronouncements In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation, to provide clarity and reduce both 1) diversity in practice and 2) cost and complexity when applying the guidance in Topic 718 to a change in the terms or conditions of a share-based payment award. ASU 2017-09 provided guidance about which changes to the terms or conditions of a share-based payment award require an entity to apply modification accounting under Topic 718. The amendments in ASU 2017-09 were effective for fiscal and interim reporting periods in fiscal years beginning after December 15, 2017. The amendments in ASU 2017-09 should be applied prospectively to an award modified on or after the adoption date. Effective January 1, 2018, the Company adopted the provisions of ASU 2017-09. The adoption did not have a material impact on the Company's consolidated financial statements or related financial statement disclosure. In January 2016, the FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The new guidance enhanced the reporting model for financial instruments and includes amendments to address aspects of recognition, measurement, presentation and disclosure. The update to the standard was effective for public companies for interim and annual periods beginning after December 15, 2017. Effective January 1, 2018, the Company adopted the provisions of ASU 2016-01. The adoption did not have a material impact on the Company's consolidated financial statements or related financial statement disclosure. Recently Issued Accounting Pronouncements In July 2017, the FASB issued ASU 2017-11, Earnings Per Share (Topic 260); Distinguishing Liabilities from Equity (Topic 480); Derivatives and Hedging (Topic 815): (Part I) Accounting for Certain Financial Instruments with Down Round Features, (Part II) Replacement of the Indefinite Deferral for Mandatorily Redeemable Financial Instruments of Certain Nonpublic Entities and Certain Mandatorily Redeemable Non-controlling Interests with a Scope Exception. The ASU allows companies to exclude a down round feature when determining whether a financial instrument (or embedded conversion feature) is considered indexed to the entity’s own stock. As a result, financial instruments (or embedded conversion features) with down round features may no longer be required to be classified as liabilities. A company will recognize the value of a down round feature only when it is triggered and the strike price has been adjusted downward. For equity-classified freestanding financial instruments, such as warrants, an entity will treat the value of the effect of the down round, when triggered, as a dividend and a reduction of income available to common shareholders in computing basic earnings per share. For convertible instruments with embedded conversion features containing down round provisions, entities will recognize the value of the down round as a beneficial conversion discount to be amortized to earnings. The guidance in ASU 2017-11 is effective for fiscal years beginning after December 15, 2018, and interim periods within those fiscal years. Early adoption is permitted, and the guidance is to be applied using a full or modified retrospective approach. The Company does not anticipate that the adoption of ASU 2017-11 will have a material impact on its consolidated financial statements unless a transaction occurs that would need to be evaluated under this guidance at which time the Company will assess the impact of this standard. In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) in order to increase transparency and comparability among organizations by recognizing lease assets and lease liabilities on the balance sheet for those leases classified as operating leases under previous GAAP. ASU 2016-02 requires that a lessee should recognize a liability to make lease payments (the lease liability) and a right-of-use asset representing its right to use the underlying asset for the lease term on the balance sheet. ASU 2016-02 is effective for fiscal years beginning after December 15, 2018 (including interim periods within those periods) using a modified retrospective approach and early adoption is permitted. The Company will adopt ASU 2016-02 in the first quarter of 2019. Although the Company is in the process of evaluating the impact of adoption of the ASU on its consolidated financial statements, the Company currently believes the most significant changes will be related to the recognition of new right-of-use assets and lease liabilities on the Company's balance sheet for real estate operating leases.
Net loss per share	Net loss per share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for common share equivalents. Diluted net loss per share is computed by dividing the net loss by the weighted-average number of common shares and common share equivalents outstanding for the period. Common share equivalents outstanding, determined using the treasury stock method, are comprised of shares that may be issued under the Company’s stock option and warrant agreements.

Summary of Significant Accoun19

Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2018
Accounting Policies [Abstract]
Schedule of potentially dilutive securities not included in the calculation of diluted net loss per share because to do so would be anti-dilutive	The following table presents the weighted average number of common share equivalents, calculated using the treasury stock method, not included in the calculation of diluted net loss per share due to the anti-dilutive effect of the securities: Three Months Ended March 31, 2018 2017 Common stock options 1,458,774 — Common stock warrants 11,395,851 6,450,612 Total 12,854,625 6,450,612

Short-term Investments (Tables)

Short-term Investments (Tables)	3 Months Ended
	Mar. 31, 2018
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale Securities Reconciliation	The following tables summarize the Company's short-term investments (dollars in thousands): As of March 31, 2018 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 2 year or less $ 86,479 $ — $ (260 ) $ 86,219 Commercial paper 1 year or less 41,936 — (70 ) 41,866 $ 128,415 $ — $ (330 ) $ 128,085 As of December 31, 2017 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 1 year or less $ 24,264 $ — $ (23 ) $ 24,241 Commercial paper 1 year or less 18,912 — (19 ) 18,893 $ 43,176 $ — $ (42 ) $ 43,134

Fair value measurements (Tables

Fair value measurements (Tables)	3 Months Ended
	Mar. 31, 2018
Fair Value Disclosures [Abstract]
Schedule of assets and liabilities that are measured at fair value on a recurring basis	The following tables summarize the assets measured at fair value on a recurring basis (in thousands): March 31, 2018 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 3,721 $ 3,721 $ — $ — Money market funds 16,846 16,846 — — Total cash and cash equivalents 20,567 20,567 — — Short-term investments: Corporate debt securities 86,219 — 86,219 — Commercial paper 41,866 — 41,866 — Total short-term investments 128,085 — 128,085 — Total $ 148,652 $ 20,567 $ 128,085 $ — December 31, 2017 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 1,026 $ 1,026 $ — $ — Money market funds 106,677 106,677 — — Total cash and cash equivalents 107,703 107,703 — — Short-term investments: Corporate debt securities 24,241 — 24,241 — Commercial paper 18,893 — 18,893 — Total short-term investments 43,134 — 43,134 — Total $ 150,837 $ 107,703 $ 43,134 $ —

Other current assets (Tables)

Other current assets (Tables)	3 Months Ended
	Mar. 31, 2018
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of other current assets	Other current assets consisted of the following (in thousands): March 31, December 31, 2018 2017 Prepaid expenses $ 2,693 $ 3,085 Deposits and other receivables 1,325 1,600 Interest receivable 403 237 $ 4,421 $ 4,922

Property and Equipment, net (Ta

Property and Equipment, net (Tables)	3 Months Ended
	Mar. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of property and equipment	Property and equipment consisted of the following (in thousands): March 31, December 31, 2018 2017 Computer equipment $ 329 $ 329 Office and other equipment 301 301 Laboratory equipment 643 643 Leasehold improvements 63 63 Gross property and equipment 1,336 1,336 Less: Accumulated depreciation (852 ) (811 ) Property and equipment, net $ 484 $ 525

Accounts payable and accrued 24

Accounts payable and accrued liabilities (Tables)	3 Months Ended
	Mar. 31, 2018
Payables and Accruals [Abstract]
Schedule of accounts payable and accrued liabilities	Accounts payable and accrued liabilities consisted of the following (in thousands): March 31, December 31, 2018 2017 Accounts payable $ 4,731 $ 4,344 Accrued clinical, development and other expenses 9,058 6,279 Accrued compensation and benefits 1,972 3,021 $ 15,761 $ 13,644

Collaboration and License Agr25

Collaboration and License Agreement (Tables)	3 Months Ended
	Mar. 31, 2018
Revenue from Contract with Customer [Abstract]
Contract with Customer, Asset and Liability	The following table presents a summary of the activity in the Company's contract liabilities during the three months ended March 31, 2018 (in thousands): Balance at Beginning of Period Additions Deductions Balance at End of Period Contract liabilities: Deferred revenue - current $ — $ 229 $ — $ 229 Deferred revenue - non-current — 304 — 304 Total contract liabilities: $ — $ 533 $ — $ 533

Warrants (Tables)

Warrants (Tables)	3 Months Ended
	Mar. 31, 2018
Equity [Abstract]
Schedule of Warrants Issued and Outstanding	As of March 31, 2018 , the following warrants for common stock were issued and outstanding: Issue date Expiration date Exercise price Number of warrants outstanding January 11, 2017 None $ 0.001 7,258,263 November 20, 2017 None $ 0.001 4,137,999 11,396,262

Commitments and Contingencies (

Commitments and Contingencies (Tables)	3 Months Ended
	Mar. 31, 2018
Leases [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum payments required under the lease are summarized as follows (in thousands): Year Ending December 31: 2018 $ 210 2019 315 2020 26 Total minimum lease payments $ 551

Stock-based compensation (Table

Stock-based compensation (Tables)	3 Months Ended
	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Employee Service Share-based Compensation Allocation	Total share-based compensation expense by statement of operations classification is presented below (in thousands): Three Months Ended March 31, 2018 2017 Research and development expense $ 1,493 $ 982 General and administrative expense 2,167 784 $ 3,660 $ 1,766

Description of Business (Detail

Description of Business (Details)	3 Months Ended
	Mar. 31, 2018segment
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of operating segments	1

Summary of Significant Accoun30

Summary of Significant Accounting Policies - Narrative (Details)	3 Months Ended
	Mar. 31, 2018
Marketable Securities
Minimum original maturity period of marketable securities	90 days

Summary of Significant Accoun31

Summary of Significant Accounting Policies - Antidilutive Securities (Details) - shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	12,854,625	6,450,612
Common stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	1,458,774	0
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities	11,395,851	6,450,612

Short-term Investments (Details

Short-term Investments (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, Amortized cost	$ 128,415	$ 43,176
Available-for-sale, Gross unrealized gains	0	0
Available-for-sale, Gross unrealized losses	(330)	(42)
Available-for-sale, Estimated fair value	$ 128,085	$ 43,134
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, maximum maturity period	2 years	1 year
Available-for-sale, Amortized cost	$ 86,479	$ 24,264
Available-for-sale, Gross unrealized gains	0	0
Available-for-sale, Gross unrealized losses	(260)	(23)
Available-for-sale, Estimated fair value	$ 86,219	$ 24,241
Commercial paper
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, maximum maturity period	1 year	1 year
Available-for-sale, Amortized cost	$ 41,936	$ 18,912
Available-for-sale, Gross unrealized gains	0	0
Available-for-sale, Gross unrealized losses	(70)	(19)
Available-for-sale, Estimated fair value	$ 41,866	$ 18,893

Fair value measurements (Detail

Fair value measurements (Details) - Recurring basis - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 20,567	$ 107,703
Short-term investments	128,085	43,134
Total	148,652	150,837
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	86,219	24,241
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	41,866	18,893
Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	3,721	1,026
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	16,846	106,677
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	20,567	107,703
Short-term investments	0	0
Total	20,567	107,703
Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 1 | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	3,721	1,026
Level 1 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	16,846	106,677
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Short-term investments	128,085	43,134
Total	128,085	43,134
Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	86,219	24,241
Level 2 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	41,866	18,893
Level 2 | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Level 2 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Short-term investments	0	0
Total	0	0
Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 | Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	0	0
Level 3 | Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	0	0
Level 3 | Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents	$ 0	$ 0

Other current assets (Details)

Other current assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 2,693	$ 3,085
Security deposits and other receivables	1,325	1,600
Interest receivable	403	237
Other current assets	4,421	4,922
Deposits paid for research and development	$ 1,000	$ 1,000

Property and Equipment, net (De

Property and Equipment, net (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 1,336	$ 1,336
Less: Accumulated depreciation	(852)	(811)
Property and equipment, net	484	525
Computer equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	329	329
Office and other equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	301	301
Laboratory equipment
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	643	643
Leasehold improvements
Property, Plant and Equipment [Line Items]
Property and equipment, Gross	$ 63	$ 63

Accounts payable and accrued 36

Accounts payable and accrued liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Payables and Accruals [Abstract]
Other liability	$ 693
Accounts payable	4,731	$ 4,344
Accrued expenses	9,058	6,279
Accrued compensation and benefits	1,972	3,021
Total accounts payable and accrued liabilities	15,761	13,644
Deferred revenue	300
Other Liabilities, Noncurrent	$ 400	$ 314

Collaboration and License Agr37

Collaboration and License Agreement Narrative (Details) - BeiGene - USD ($)	Jan. 07, 2018	Mar. 31, 2018
Disaggregation of Revenue [Line Items]
Upfront fee received	$ 10,000,000
Milestone payments receivable	$ 123,000,000
Revenue from contract with customer		$ 9,500,000
Remaining performance obligation		$ 500,000

Collaboration and License Agr38

Collaboration and License Agreement (Details)	3 Months Ended
	Mar. 31, 2018USD ($)
Change in Contract with Customer Liability [Roll Forward]
Deferred revenue - current	$ 0
Additions	229,000
Deductions	0
Deferred revenue - current	229,000
Deferred revenue - non-current	0
Additions	304,000
Deductions	0
Deferred revenue - non-current	304,000
Total contract liabilities:	0
Additions	533,000
Deductions	0
Total contract liabilities:	$ 533,000

Warrants (Details)

Warrants (Details) - $ / shares	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Class of Warrant or Right [Line Items]
Number of warrants outstanding	11,396,262
Warrants exercised via cashless exercises	0	0
Class of Warrants Issued January 11, 2017
Class of Warrant or Right [Line Items]
Exercise price of warrants (in dollars per share)	$ 0.001
Number of warrants outstanding	7,258,263
November 21, 2012 Warrants
Class of Warrant or Right [Line Items]
Exercise price of warrants (in dollars per share)	$ 0
Number of warrants outstanding	4,137,999

Commitments and Contingencies N

Commitments and Contingencies Narrative (Details) - Building	3 Months Ended
	Mar. 31, 2018USD ($)	Jun. 24, 2014ft²
Operating Leased Assets [Line Items]
Square feet of space | ft²		18,000
Minimum monthly rental expense | $	$ 24,100
Annual rent increase (Percentage)	3.00%

Commitments and Contingencies F

Commitments and Contingencies Future Minimum Payments (Details) $ in Thousands	Mar. 31, 2018USD ($)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2,018	$ 210
2,019	315
2,020	26
Total minimum lease payments	$ 551

Stock-based compensation (Detai

Stock-based compensation (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$ 3,660	$ 1,766
Shares issued	402,948	0
Proceeds from stock options exercised	$ 5,900
Research and development expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	1,493	$ 982
General and administrative expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Allocated share-based compensation expense	$ 2,167	$ 784