Mirati Therapeutics (MRTX) 10-K9 Mar 172016 FY Annual reportFinancial data

Company Profile

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
Document and Entity Information - USD ($) $ in Millions	Dec. 31, 2016	Mar. 03, 2017	Jun. 30, 2016
Document and Entity Information
Entity Registrant Name	MIRATI THERAPEUTICS, INC.
Entity Central Index Key	1,576,263
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	FY
Entity Filer Category	Accelerated Filer
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Common Stock, Shares Outstanding		24,939,797
Entity Public Float			$ 77

CONSOLIDATED BALANCE SHEETS

CONSOLIDATED BALANCE SHEETS - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets
Cash and cash equivalents	$ 22,383	$ 49,493
Short-term investments	34,351	72,834
Other current assets	2,821	3,075
Total current assets	59,555	125,402
Property and equipment, net	629	614
Other long-term assets	3,260	2,001
Total assets	63,444	128,017
Current liabilities
Accounts payable and accrued liabilities	15,002	9,798
Total current liabilities	15,002	9,798
Other liabilities	133	43
Total current liabilities	15,135	9,841
Commitments and contingencies
Stockholders' equity
Preferred stock, $0.001 par value, 10,000,000 shares authorized; none issued and outstanding at both December 31, 2016 and December 31, 2015	0	0
Common stock, $0.001 par value; 100,000,000 authorized; 19,937,095 and 19,282,935 issued and outstanding at December 31, 2016 and December 31, 2015, respectively	20	19
Additional paid-in capital	428,507	415,232
Accumulated other comprehensive income	9,533	9,558
Accumulated deficit	(389,751)	(306,633)
Total stockholders' equity	48,309	118,176
Total liabilities and stockholders' equity	$ 63,444	$ 128,017

CONSOLIDATED BALANCE SHEETS (Pa

CONSOLIDATED BALANCE SHEETS (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	19,937,095	19,282,935
Common stock, shares outstanding	19,937,095	19,282,935

CONSOLIDATED STATEMENTS OF OPER

CONSOLIDATED STATEMENTS OF OPERATIONS AND COMPREHENSIVE LOSS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Expenses
Research and development	$ 68,487	$ 48,959	$ 26,071
General and administrative	15,292	15,755	12,699
Restructuring costs	0	0	334
Total operating expenses	83,779	64,714	39,104
Loss from operations	(83,779)	(64,714)	(39,104)
Other income (expense), net	661	170	(77)
Change in fair value of warrant liability	0	0	(4,517)
Loss before income taxes	(83,118)	(64,544)	(43,698)
Income tax benefit	0	0	0
Net loss	(83,118)	(64,544)	(43,698)
Unrealized gain (loss) on available-for-sale investments	25	(37)	(14)
Comprehensive loss	$ (83,143)	$ (64,507)	$ (43,684)
Loss per share, basic (in US$ per share)	$ (4.20)	$ (3.82)
Basic and diluted net loss per share (in dollars per share)			$ (3.24)
Weighted average number of shares used in computing net loss per share, basic and diluted (in shares)	19,787,349	16,901,826	13,483,467

CONSOLIDATED STATEMENTS OF CHAN

CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Common Stock	Additional paid-in capital	Accumulated other comprehensive income	Accumulated deficit
Beginning balance at Dec. 31, 2013	$ 25,885	$ 13	$ 214,756	$ 9,507	$ (198,391)
Beginning balance (in shares) at Dec. 31, 2013		13,446,976
Increase (Decrease) in Stockholders' Equity
Net loss	(43,698)				(43,698)
Stock-based compensation expense	7,050		7,050
Reclassification of warrants	36,931		36,931
Exercise of options for cash	887	$ 1	886
Exercise of options for cash (in shares)		76,224
Net exercise of warrants	$ 993		993
Net exercise of warrants (in shares)	43,526	43,526
Unrealized gain on investments	$ 14			14
Ending balance at Dec. 31, 2014	28,062	$ 14	260,616	9,521	(242,089)
Ending balance (in shares) at Dec. 31, 2014		13,566,726
Increase (Decrease) in Stockholders' Equity
Net loss	(64,544)				(64,544)
Stock-based compensation expense	10,254		10,254
Exercise of options for cash	552		552
Exercise of options for cash (in shares)		36,566
Issuance of common stock, net of costs	143,293	$ 4	143,289
Issuance of common stock, net of costs (in shares)		4,837,500
Issuance of common stock from ESPP	522		522
Issuance of common stock from ESPP purchase (in shares)		32,645
Net exercise of warrants	$ 0	$ 1	(1)
Net exercise of warrants (in shares)	809,498	809,498
Unrealized gain on investments	$ 37			37
Ending balance at Dec. 31, 2015	$ 118,176	$ 19	415,232	9,558	(306,633)
Ending balance (in shares) at Dec. 31, 2015	19,282,935	19,282,935
Increase (Decrease) in Stockholders' Equity
Net loss	$ (83,118)				(83,118)
Stock-based compensation expense	10,624		10,624
Exercise of options for cash	$ 240		240
Exercise of options for cash (in shares)	22,132	22,132
Issuance of common stock from ESPP	$ 297		297
Issuance of common stock from ESPP purchase (in shares)		28,483
Net exercise of warrants	$ 0
Net exercise of warrants (in shares)	603,545	289,789
Exercise of warrants for cash	$ 2,115	$ 1	2,114
Exercise of warrants for cash (in shares)	313,756	313,756
Unrealized gain on investments	$ (25)			(25)
Ending balance at Dec. 31, 2016	$ 48,309	$ 20	$ 428,507	$ 9,533	$ (389,751)
Ending balance (in shares) at Dec. 31, 2016	19,937,095	19,937,095

CONSOLIDATED STATEMENTS OF CASH

CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating activities
Net loss	$ (83,118)	$ (64,544)	$ (43,698)
Non-cash adjustments reconciling net loss to operating cash flows
Depreciation of property and equipment	180	212	199
Amortization of premium on investments	7	337	534
Share-based compensation expense	10,624	10,254	7,050
Change in fair value of warrant liability	0	0	4,517
Changes in operating assets and liabilities
Other current assets	254	279	(1,209)
Other long-term assets	(1,259)	(1,675)	(326)
Accounts payable and accrued liabilities	5,196	4,370	151
Other current and long term liabilities	99	53	21
Cash flows used in operating activities	(68,017)	(50,714)	(32,748)
Investing activities:
Purchases of short-term investments	(70,269)	(104,954)	(10,468)
Disposal and maturities of short-term investments	108,720	54,530	35,073
Purchases of property and equipment	(196)	(329)	(386)
Cash flows provided by (used in) investing activities	38,255	(50,753)	24,219
Financing activities:
Proceeds from issuance of common stock, net of issuance costs	0	143,293	0
Proceeds from issuance under employee stock purchase plan	297	522	0
Proceeds from exercise of common stock options and warrants	2,355	552	887
Cash flows provided by financing activities	2,652	144,367	887
Increase (decrease) in cash and cash equivalents	(27,110)	42,900	(7,642)
Cash and cash equivalents, beginning of year	49,493	6,593	14,235
Cash and cash equivalents, end of year	22,383	49,493	6,593
Net exercise of warrants	$ 0	$ 0	$ 993

DESCRIPTION OF BUSINESS

DESCRIPTION OF BUSINESS	12 Months Ended
DESCRIPTION OF BUSINESS	Dec. 31, 2016
DESCRIPTION OF BUSINESS
DESCRIPTION OF BUSINESS	Description of Business Mirati Therapeutics, Inc. ("Mirati" or the "Company") is a clinical-stage biopharmaceutical company focused on developing a pipeline of targeted oncology products. The Company focuses its development programs on drugs intended to treat specific genetically defined and selected subsets of cancer patients with unmet needs. The Company's common stock has been listed on the NASDAQ Capital Market since July 15, 2013 under the ticker symbol "MRTX." The Company has a wholly owned subsidiary in Canada, MethylGene, Inc. ("MethylGene"). The Company also has an indirect, wholly-owned subsidiary, MethylGene US Inc., which was incorporated in Princeton, New Jersey on December 20, 2011 and started business activity in 2012. MethylGene US Inc. ceased operations effective January 1, 2014. As a result of the arrangement agreement discussed in Note 2 under the heading "Basis of Presentation," Mirati became the parent company and the primary operating company during 2013. Refer to Note 2 for further discussion of the Company’s corporate structure.

SUMMARY OF SIGNIFICANT ACCOUNTI

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Dec. 31, 2016
Accounting Policies [Abstract]
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES	Summary of Significant Accounting Policies Basis of Presentation These consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP"). These consolidated financial statements include the accounts of the Company, MethylGene and MethylGene US Inc. All significant inter-company transactions, balances and expenses have been eliminated upon consolidation. Mirati was incorporated under the laws of the State of Delaware on April 29, 2013. On May 8, 2013, the Company's Board of Directors approved and the Company entered into an arrangement agreement ("Arrangement") with MethylGene. Upon completion of the Arrangement, MethylGene became the Company's wholly-owned subsidiary. These consolidated financial statements are presented in United States ("U.S.") Dollars, which effective January 1, 2013, is also the functional currency of the Company. Use of Estimates The preparation of the Company's audited consolidated financial statements in conformity with U.S. GAAP 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 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, with unrealized gains and losses included as a separate component of stockholders’ equity. Realized gains and losses from the sale of available-for-sale securities or the amounts, net of tax, reclassified out of accumulated other comprehensive income, 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. Property and Equipment, Net Property and equipment is stated at historical cost less accumulated depreciation. Historical cost includes expenditures that are directly attributable to the acquisition of the items. All repairs and maintenance are charged to net loss during the financial period in which they are incurred. Depreciation of property and equipment is calculated using the straight-line method over the estimated useful lives of the assets, as follows: Computer equipment 3 years Office and other equipment 6 years Laboratory equipment 6 years Leasehold improvements The lesser of the lease term or the life of the asset On disposal or impairment of property and equipment, the cost and related accumulated depreciation is removed from the consolidated financial statements and the net amount, less any proceeds, is included in net loss. Impairment of Long-Lived Assets The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. If such circumstances are determined to exist, an estimate of undiscounted future cash flows produced by the long-lived asset, including its eventual residual value, is compared to the carrying value to determine whether impairment exists. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. Fair value is estimated through discounted cash flow models to project cash flows from the asset. The Company recognized no impairment charges for the years ended December 31, 2016 and 2015 and immaterial impairment charges related to property and equipment for the year ended December 31, 2014 . Reclassification of Warrants In 2011 and 2012, MethylGene issued common stock warrants in connection with the issuance of common stock through private placements (the "2011 Warrants" and the "2012 Warrants"). The exercise prices of the 2011 and 2012 Warrants were denominated in Canadian dollars. Upon the issuance of the 2011 and 2012 Warrants, the net proceeds were allocated to common stock and warrants based on their relative fair values, and the fair value of the issued common stock warrants was calculated utilizing the Black-Scholes option-pricing model. The allocated fair value was then recorded as warrants within stockholders’ equity on the consolidated balance sheet. Effective January 1, 2013, the Company changed its functional currency which changed how the 2011 and 2012 warrants were accounted for as they continued to have exercise prices denominated in Canadian dollars. At each reporting period subsequent to January 1, 2013, the fair value of the warrant liability was recalculated and any corresponding increase or decrease to the warrant liability was recorded as change in fair value of warrant liability on the consolidated statement of operations and comprehensive loss. The estimated fair value was determined using the Black-Scholes option-pricing model based on the estimated value of the underlying common stock at the valuation measurement date, the remaining contractual term of the warrants, risk-free interest rates, expected dividends and expected volatility of the price of the underlying common stock. During the second half of 2014, the Company amended all of its outstanding warrant agreements to allow for the warrants to be denominated in U.S. Dollars. As a result of this amendment, the amended warrants qualified for equity classification and were reclassified into stockholders’ equity at their fair value as of the amendment date, and as of the amendment date, revaluations of fair value are no longer required. For the years ended December 31, 2016 and 2015, the company recorded no warrant valuation expense. For the year ended December 31, 2014, the Company recorded warrant valuation expense of $4.5 million , which is reported as change in fair value of warrant liability in the condensed consolidated statement of operations and comprehensive loss. Share-Based Compensation We measure and recognize compensation expense for share-based payments based on estimated fair value. We estimate the fair value of stock options granted using the Black-Scholes option-pricing model. The Black-Scholes option-pricing model requires the use of certain estimates and highly judgmental assumptions that affect the amount of share-based compensation expense recognized in our consolidated financial statements. These assumptions include the historical volatility of our stock price, expected term of the options, the risk-free interest rate and expected dividend yields. Share-based compensation is recognized using the graded accelerated vesting method. If any of the assumptions used in our calculation change significantly, share-based compensation expense may differ materially from what we have recorded in the current period. Investment Tax Credits The Company's accounts include claims for investment tax credits ("ITCs") relating to scientific research and experimental development activities of the Company. The qualification and recording of these activities for investment tax credit purposes are established by the Canadian federal and Provincial Tax Acts and are subject to audit by the taxation authorities. Refundable ITCs are reflected as reductions of expenses or reductions of the cost of the assets to which they relate when there is reasonable assurance that the assistance will be received and all conditions have been complied with. The non-refundable ITCs are carried forward for a time and will be recognized when it is more likely than not that the Company will become subject to Canadian federal taxes, at which time, these ITCs will be applied as a reduction of tax expense. As operations in Canada ceased in early 2014, there were no new ITCs earned for the years ended December 31, 2016 or 2015 . Research and Development Expenses Research and development expenditures are charged to net loss in the period in which they are incurred and are comprised of the following types of costs incurred in performing research and development activities: clinical trial and related clinical manufacturing costs, salaries and benefits including share-based compensation expense, costs for allocated facilities and depreciation of equipment, contract services, license fees paid in connection with our early discovery efforts and data management costs. Income Taxes Income taxes have been accounted for using the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates applicable to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in net loss in the period that includes the enactment date. A valuation allowance against deferred tax assets is recorded if, based upon the weight of all available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. For uncertain tax positions that meet "a more likely than not" threshold, the Company recognizes the benefit of uncertain tax positions in the consolidated financial statements. Segment Reporting Operating segments are components of a business where separate discrete financial information is available for evaluation by the chief operating decision-maker for purposes of making decisions regarding resource allocation and assessing performance. To date, the Company has viewed its operations and managed its business as one segment operating primarily in the United States. Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities 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 potentially dilutive securities not included in the calculation of diluted net loss per share due to the anti-dilutive effect of the securities: Year ended December 31, 2016 2015 2014 Common stock options 173,776 582,662 253,595 Common stock warrants 315,834 1,546,201 1,515,445 Total 489,610 2,128,863 1,769,040

RECENTLY ISSUED AND RECENTLY AD

RECENTLY ISSUED AND RECENTLY ADOPTED ACCOUNTING PRONOUNCEMENTS	12 Months Ended
	Dec. 31, 2016
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
RECENTLY ISSUED ACCOUNTING PRONOUNCEMENTS AND RECENTLY ADOPTED ACCOUNTING PRONOUNCEMENTS	Recently Issued and Recently Adopted Accounting Pronouncements 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. In March 2016, the FASB issued Accounting Standard Update ("ASU") 2016-09, Compensation-Stock Compensation (Topic 718). The new guidance changes the accounting and simplifies various aspects of the accounting for share-based payments to employees. The guidance allows for a policy election to account for forfeitures as they occur or based on an estimated number of awards that are expected to vest. ASU 2016-09 is effective for annual periods beginning after December 15, 2016, with early adoption permitted. The Company will adopt this standard as of January 1, 2017 and will begin to account for forfeitures as they occur beginning on that date. We expect the adoption of this standard will result in an adjustment to beginning retained earnings of $0.4 million . In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842). Under the new guidance, lessees are required to recognize most lease assets and lease liabilities on their balance sheets and record expenses on their income statements in a manner similar to current accounting. The new guidance is effective for fiscal years beginning after December 15, 2018, with early adoption permitted. The primary impact of this new accounting guidance will be related to our facilities lease and the Company is currently evaluating the impact that this guidance will have on its consolidated financial statements and related financial statement disclosures. In January 2016, the FASB issued ASU No. 2016-01, Financial Instruments - Overall (Subtopic 825-10): Recognition and Measurement of Financial Assets and Financial Liabilities. The new guidance enhances the reporting model for financial instruments and includes amendments to address aspects of recognition, measurement, presentation and disclosure. The update to the standard is effective for public companies for interim and annual periods beginning after December 15, 2017. The Company does not believe the adoption of this standard will have a material impact on its financial position, results of operations or related financial statement disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which will replace numerous requirements in U.S. GAAP, including industry-specific requirements, and provide companies with a single revenue recognition model for recognizing revenue from contracts with customers. The core principle of the new standard is that a company should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the company expects to be entitled in exchange for those goods or services. In August 2015, the FASB approved a proposal to defer the effective date of the guidance until annual and interim reporting periods beginning after December 15, 2017. Although we currently do not have any revenue contracts, we anticipate early adopting this standard effective January 1, 2017 using the full retrospective method of adoption so that, in the event we enter into any revenue contracts, the contracts will be accounted for under the new guidance from inception of the contract. Recently Adopted Accounting Pronouncements In August 2014, the FASB issued ASU 2014-15, Presentation of Financial Statements-Going Concern (Subtopic 205-40): Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. Under the new guidance, management is required to assess an entity’s ability to continue as a going concern, and to provide related footnote disclosures in certain circumstances. The provisions of this ASU are effective for annual periods ending after December 15, 2016, and for annual and interim periods thereafter; early adoption is permitted. We adopted this guidance as of December 31, 2016 and the adoption did not require any additional disclosures in our consolidated financial statements for the year ended December 31, 2016. In November 2015, the FASB issued ASU No. 2015-17, Balance Sheet Classification of Deferred Taxes, to simplify the presentation of deferred taxes. This amendment requires that all deferred tax assets and liabilities, along with any related valuation allowances, be classified as noncurrent on the balance sheet. ASU 2015-17 is effective for annual and interim reporting periods ending after December 15, 2016. Early adoption is permitted, and the new guidance may be applied either prospectively or retrospectively. We have adopted this guidance prospectively as of December 31, 2015 and the adoption has no impact on our consolidated balance sheet since we have a full valuation allowance.

INVESTMENTS

INVESTMENTS	12 Months Ended
INVESTMENTS	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
INVESTMENTS	Investments The following tables summarize our short-term investments (in thousands): As of December 31, 2016 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 1 year or less $ 20,622 $ — $ (3 ) $ 20,619 Commercial paper 1 year or less 13,717 15 — 13,732 $ 34,339 $ 15 $ (3 ) $ 34,351 As of December 31, 2015 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 1 year or less $ 27,644 $ — $ (22 ) $ 27,622 Commercial paper 1 year or less 45,158 54 — 45,212 $ 72,802 $ 54 $ (22 ) $ 72,834 Unrealized gains and losses on available-for-sale securities are included as a component of comprehensive loss. At December 31, 2016 , 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	12 Months Ended
FAIR VALUE MEASUREMENTS	Dec. 31, 2016
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, 2 or 3 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 table summarizes the assets and liabilities measured at fair value on a recurring basis (in thousands): December 31, 2016 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 2,728 $ 2,728 $ — $ — Money market funds 19,655 19,655 — — Total cash and cash equivalents 22,383 22,383 — — Short-term investments: Corporate debt securities 20,619 — 20,619 — Commercial paper 13,732 — 13,732 — Total short-term investments 34,351 — 34,351 — Total $ 56,734 $ 22,383 $ 34,351 $ — December 31, 2015 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 875 $ 875 $ — $ — Money market funds 18,875 18,875 — — Corporate debt securities 6,749 — 6,749 — Commercial paper 22,994 — 22,994 Total cash and cash equivalents 49,493 19,750 29,743 — Short-term investments: Corporate debt securities 27,622 — 27,622 — Commercial paper 45,212 — 45,212 — Total short-term investments 72,834 — 72,834 — Total $ 122,327 $ 19,750 $ 102,577 $ — The Company’s investments in Level 1 assets are valued based on publicly available quoted market prices for identical securities as of December 31, 2016 and 2015 . 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 for the years ended December 31, 2016 and 2015 .

OTHER CURRENT ASSETS AND LONG-T

OTHER CURRENT ASSETS AND LONG-TERM ASSETS	12 Months Ended
OTHER CURRENT ASSETS AND LONG-TERM ASSETS	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
OTHER CURRENT ASSETS AND LONG-TERM ASSETS	Other Current Assets and Other Long-Term Assets Other current assets consisted of the following (in thousands): December 31, 2016 2015 Prepaid expenses $ 1,879 $ 2,287 Deposits and other receivables 759 551 Interest receivables 183 237 $ 2,821 $ 3,075 The other long-term assets balance as of December 31, 2016 consists of $3.3 million in deposits paid in conjunction with the Company's research and development activities compared to $2.0 million as of December 31, 2015 .

PROPERTY AND EQUIPMENT

PROPERTY AND EQUIPMENT	12 Months Ended
PROPERTY AND EQUIPMENT	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
PROPERTY AND EQUIPMENT	Property and Equipment, Net Property and equipment, net consisted of the following (in thousands): December 31, 2016 2015 Computer equipment $ 329 $ 329 Office and other equipment 301 256 Laboratory equipment 563 425 Leasehold improvements 63 51 Gross property and equipment 1,256 1,061 Less: Accumulated depreciation (627 ) (447 ) Property and equipment, net $ 629 $ 614 The Company incurred depreciation expense of $0.2 million during the years ended December 31, 2016 , 2015 and 2014 , respectively.

ACCOUNTS PAYABLE AND ACCRUED LI

ACCOUNTS PAYABLE AND ACCRUED LIABILITIES	12 Months Ended
ACCOUNTS PAYABLE AND ACCRUED LIABILITIES	Dec. 31, 2016
Payables and Accruals [Abstract]
ACCOUNTS PAYABLE AND ACCRUED LIABILITIES	Accounts Payable and Accrued Liabilities Accounts payable and accrued liabilities consisted of the following (in thousands): December 31, 2016 2015 Accounts payable $ 6,296 $ 2,104 Accrued clinical, development and other expenses 5,743 5,311 Accrued compensation and benefits 2,923 2,352 Other current liabilities 40 31 $ 15,002 $ 9,798

STOCKHOLDERS' EQUITY

STOCKHOLDERS' EQUITY	12 Months Ended
STOCKHOLDERS' EQUITY	Dec. 31, 2016
Stockholders' Equity Note [Abstract]
STOCKHOLDERS' EQUITY	Stockholders' Equity Common Stock The following shares were reserved for future issuance: December 31, 2016 Common stock options outstanding and available for future grant 3,452,409 Warrants to purchase common stock 695,383 Employee Stock Purchase Plan 238,872 4,386,664 Warrants The Company issued warrants in connection with private placements of common stock in November 2012. As of December 31, 2016 the following warrants for common stock were issued and outstanding: Issue date Expiration date Exercise price Number of warrants outstanding November 21, 2012 November 21, 2017 $ 7.86 695,383 During the year ended December 31, 2016 , warrants for 289,789 shares of the Company's common stock were exercised via cashless exercises and 313,756 shares were exercised for cash generating proceeds of $2.1 million and the Company issued a total of 603,545 shares of common stock. During the years ended December 31, 2015 and 2014, warrants for 1,037,330 and 73,964 shares of the Company's common stock were exercised via cashless exercises and the Company issued a total of 809,498 and 43,526 shares of common stock, respectively.

SHARE-BASED COMPENSATION

SHARE-BASED COMPENSATION	12 Months Ended
SHARE-BASED COMPENSATION	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
SHARE-BASED COMPENSATION	Share-Based Compensation Equity Incentive Plan The Company has in place a stock option plan (the "Stock Option Plan") for the benefit of employees, directors, officers and consultants of the Company. In May 2013 our Board of Directors adopted the 2013 Equity Incentive Plan (the "2013 Plan"). The 2013 Plan was approved by our stockholders in connection with the Arrangement. The 2013 Plan is a continuation of and successor to the Stock Option Plan and no further grants will be made under the Stock Option Plan. As of December 31, 2016 , there were approximately 0.6 million stock options available to be issued. To date, share-based compensation awards under either the Stock Option Plan or the 2013 Plan consist of incentive and non-qualified stock options. Stock options granted under each of the plans must have an exercise price equal to at least 100% of the fair market value of our common stock on the date of grant and generally vest over four years. The Stock Option Plan has contractual terms ranging from five to seven years and the 2013 Plan has contractual terms ranging from seven to ten years. The following table summarizes our stock option activity and related information for the year ended December 31, 2016 : Number of options Weighted average exercise price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (millions) Balance outstanding as of December 31, 2015 1,932,880 $ 16.71 Granted 1,082,724 $ 16.90 Exercised (22,132 ) $ 10.85 Canceled/forfeited (172,642 ) $ 20.61 Expired (7,488 ) $ 23.28 Balance outstanding as of December 31, 2016 2,813,342 $ 16.57 7.0 $ 21.95 Options exercisable at December 31, 2016 1,402,702 $ 15.42 5.3 $ — Options vested and expected to vest at December 31, 2016 2,813,342 $ 16.57 7.0 $ 21.95 The total intrinsic value of stock options exercised was $0.3 million for the year ended December 31, 2016 and $0.6 million for the years ended December 31, 2015 and 2014 , respectively. The Company received total cash of $0.2 million , $0.6 million and $0.9 million for the exercise of options for the years ended December 31, 2016 , 2015 and 2014 , respectively. The total fair value of options vested during the years ended December 31, 2016 , 2015 and 2014 was $8.6 million , $6.5 million and $3.0 million , respectively. Upon option exercise, the Company issues new shares of our common stock. Total share-based compensation expense by statement of operations classification is presented below (in thousands): Year ended December 31, 2016 2015 2014 Research and development expense $ 5,461 $ 3,669 $ 2,565 General and administrative expense 5,163 6,585 4,485 $ 10,624 $ 10,254 $ 7,050 For the years ended December 31, 2016 , 2015 and 2014 , no share-based compensation expense was capitalized and there were no recognized tax benefits associated with the share-based compensation charge. The fair value of options granted is estimated at the date of grant using the Black-Scholes option pricing model. The assumptions used for the specified reporting periods and the resulting estimates of weighted-average estimated fair value per share of options granted during those periods are as follows: Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.5% 1.5% 2.1% Dividend yield —% —% —% Volatility factor 101.7% 104.3% 113.0% Expected term (in years) 6.0 6.0 6.7 Weighted average estimated fair value per share $13.32 $19.44 $16.09 Risk-Free Interest Rate - The risk-free interest rate is the rate for periods equal to the expected term of the stock option based on U.S. Treasury zero-coupon bonds. Dividend Yield - The dividend yield is based on the Company’s history and expectation of dividend payouts. The Company has not paid, and does not intend to pay dividends. Volatility Factor - The expected volatility assumption was determined by examining the historical volatility of the Company's stock. Expected Term - The expected term represents the weighted average period the stock options are expected to be outstanding. The Company uses the simplified method for estimating the expected term as provided by the Securities and Exchange Commission. The simplified method calculates the expected term as the average time-to-vesting and the contractual life of the options. The Company believes this methodology is appropriate given the Company's limited history as a U.S. public company. The total compensation cost not yet recognized as of December 31, 2016 related to non-vested option awards was $8.0 million which will be recognized over a weighted-average period of 1.3 years. 2013 Employee Stock Purchase Plan In May 2013, the Company's Board of Directors adopted the ESPP. The ESPP was approved by the Company's stockholders in connection with the Arrangement. In December 2014, the ESPP became effective and the first purchase period began. The ESPP permits eligible employees to make payroll deductions to purchase up to $25,000 of the Company’s common stock on regularly scheduled purchase dates at a discount. Offering periods under the ESPP are not more than six months in duration and shares are purchased at 85% of the lower of the closing price for the Company’s common stock on the first day of the offering period or the date of purchase. The ESPP initially authorized the issuance of 300,000 shares of the Company’s common stock pursuant to rights granted to employees for their payroll deductions. As of December 31, 2016 , 61,128 shares have been issued out of the plan.

EMPLOYEE BENEFIT PLAN

EMPLOYEE BENEFIT PLAN	12 Months Ended
EMPLOYEE BENEFIT PLAN	Dec. 31, 2016
Compensation and Retirement Disclosure [Abstract]
EMPLOYEE BENEFIT PLAN	Employee Benefit Plan The Company has a defined contribution 401(k) plan (the "Plan") for all employees. Employees are eligible to participate in the Plan if they are at least 21 years of age or older. Under the terms of the Plan, employees may make voluntary contributions as a percentage of compensation. The Company matches up to 4% of an employee's contributions, subject to a limit of $2,500 per year. Expense associated with the Company's matching contribution totaled $0.1 million for the years ended December 31, 2016 , 2015 and 2014 , respectively.

INCOME TAXES

INCOME TAXES	12 Months Ended
INCOME TAXES	Dec. 31, 2016
Income Tax Disclosure [Abstract]
INCOME TAXES	Income Taxes The Company had no federal income tax expense and immaterial state tax expense for the years ended December 31, 2016 , 2015 and 2014 . The differences between the effective income tax rate and the statutory tax rates during the years ended 2016 , 2015 and 2014 are as follows (in thousands): Year Ended December 31, 2016 2015 2014 Net loss before tax $ (83,118 ) $ (64,544 ) $ (43,698 ) Statutory combined US federal and state tax rate 34.00 % 34.00 % 39.83 % Statutory federal and state taxes (28,260 ) (21,945 ) (17,405 ) Increase (decrease) in taxes recoverable resulting from: Effect of change in valuation allowance 28,446 22,350 12,273 Non-deductible share-based compensation 1,247 923 930 Non-deductible warrant expenses for tax purposes — — 1,799 Tax credits (2,906 ) (2,430 ) (227 ) Share issue costs - temporary difference (78 ) (184 ) (184 ) Differential in income tax rates of foreign subsidiary 261 31 3,047 Uncertain Tax Positions 3,921 1,961 47 Return to provision and other true-ups (2,619 ) (899 ) — Other differences (12 ) 193 (280 ) Income tax benefit $ — $ — $ — Deferred Tax The following table summarizes the significant components of our deferred tax assets (in thousands): December 31, 2016 2015 Deferred tax assets: Tangible and intangible depreciable assets $ 990 $ 199 Stock compensation 6,635 4,429 Provisions 853 725 Financing fees — 78 Net operating loss carry forwards 66,489 42,864 Capital loss carryforward 51 102 Scientific research and experimental development expenditures 5,531 5,552 Research and development tax credits 4,266 2,411 Total gross deferred tax assets 84,815 56,360 Less valuation allowance (84,815 ) (56,360 ) Net deferred tax assets $ — $ — Total valuation allowance increased by $28.5 million for the year ended December 31, 2016 . The Company has established a full valuation allowance against its deferred tax assets as of December 31, 2016 due to the uncertainty surrounding the realization of such assets as evidenced by the cumulative losses from operations through December 31, 2016 . For Canadian federal income tax purposes, the Company's Canadian federal scientific research and experimental development expenditures amounted to $19.9 million at December 31, 2016 and 2015 and $20.1 million at December 31, 2014 and for provincial income tax purposes amounted to $21.6 million at December 31, 2016 and 2015 and $22.7 million at December 31, 2014 . As operations in Canada ceased during 2014, the expenditures incurred for the year ended December 31, 2016 and 2015 were much lower than previous years. These expenditures are available to reduce future taxable income and have an unlimited carry forward period. Scientific research and development expenditures are subject to verification by the taxation authorities, and accordingly, these amounts may vary by a material amount. In addition, the Company has research and development tax credit carryforwards for U.S. federal and state income tax purposes as of December 31, 2016 of $4.4 million and $2.0 million , respectively. The federal credits will begin to expire in 2034 unless utilized and the state credits have an indefinite life. At December 31, 2016 , the Company's net operating loss carry forwards ("NOLs") for U.S. federal and state income taxes were $133.4 million and $77.3 million , respectively and the Company's NOLs for Canadian federal and provincial income tax purposes were $79.2 million and $78.5 million , respectively. The NOLs are available to offset future taxable income from both U.S. federal and state tax sources, as well as Canadian federal and provincial tax sources and the tax benefits of which have not been recognized in the consolidated financial statements. The NOLs expire as follows (in thousands): US Canada Federal State Federal Provincial Expires in: 2030 $ — $ — $ 5,907 $ 5,985 2031 — — 7,059 7,066 2032 — — 13,308 12,433 2033 3,261 2,286 18,623 19,385 2034 7,260 22,162 32,401 31,809 2035 53,345 52,878 1,084 1,084 2036 69,508 — 777 777 $ 133,374 $ 77,326 $ 79,159 $ 78,539 The future utilization of the US federal and state NOL carryforwards to offset future taxable income may be subject to an annual limitation as a result of ownership changes that may have occurred previously or may occur in the future. The Tax Reform Act of 1986 (the "Act") limits a company's ability to utilize certain tax credit carryforwards and net operating loss carryforwards in the event of a cumulative change in ownership in excess of 50% as defined in the Act. The Canadian Federal and Provincial Tax Acts maintain similar rules in the case of acquisition of control. The Company files income tax returns in the U.S. (federal and state) and Canada (federal and provincial). The Company’s U.S. operations have not been audited for any open taxation years. The Company has experienced losses for U.S. tax purposes and therefore, the taxation authorities may review any loss year, if and when the losses are utilized. For Canadian tax purposes, the Company remains subject to federal and provincial audit for the December 31, 2012 and subsequent taxable years. Where taxation years remain open, the Company considers it reasonably possible that issues may be raised or tax positions agreed to with the taxation authorities, which may result in increases or decreases of the balance of non-refundable ITCs and NOLs. However, an estimate of such increases and decreases cannot be currently made. A reconciliation of the beginning and ending amounts of unrecognized tax positions are as follows (in thousands): Federal Provincial/State December 31, December 31, 2016 2015 2014 2016 2015 2014 Unrecognized tax positions, beginning of year $ 509 $ 42 $ 35 $ 2,274 $ 18 $ 6 Gross increase — current period tax positions 598 445 35 195 259 12 Gross decrease — prior period tax positions (9 ) (4 ) (28 ) — (3 ) — Gross increase — prior period tax positions — 26 — 4,866 2,000 — Expiration of statute of limitations (3 ) — — (2 ) — — Unrecognized tax positions, end of year $ 1,095 $ 509 $ 42 $ 7,333 $ 2,274 $ 18 If recognized, none of the unrecognized tax positions would impact the Company's income tax benefit or effective tax rate as long as the Company's deferred tax assets remain subject to a full valuation allowance. The Company does not expect any significant increases or decreases to the Company's unrecognized tax positions within the next 12 months. The Company recognizes interest and penalties related to unrecognized tax benefits in income tax expense. The Company had no accrual for interest or penalties on tax matters as of December 31, 2016 and 2015 and the Company had no ongoing tax audits as of December 31, 2016 .

INVESTMENT TAX CREDITS

INVESTMENT TAX CREDITS	12 Months Ended
INVESTMENT TAX CREDITS	Dec. 31, 2016
INVESTMENT TAX CREDITS
INVESTMENT TAX CREDITS	Investment Tax Credits In prior years, the Company was entitled to claim Canadian federal and provincial ITCs for eligible scientific research and development expenditures. The Company recorded ITCs based on management's best estimates of the amount to be recovered and ITCs claimed are subject to audit by the taxation authorities and accordingly, may vary by a material amount. The Company has not recorded federal or provincial ITCs since the year ended December 31, 2013, as the primary operations of the Company were moved from Canada to San Diego, California in early 2014. The Company's non-refundable Canadian federal ITCs as of December 31, 2016 are $3.9 million and relate to scientific research and development expenditures, which may be utilized to reduce Canadian federal income taxes payable in future years. The benefits of the non-refundable Canadian federal ITCs have not been recognized in the financial statements and will be recorded as a reduction of tax expense when realized. The non-refundable investment tax credits expire as follows (in thousands): FEDERAL ITC Expires in: 2030 $ 764 2031 1,000 2032 1,125 2033 1,018 $ 3,907

COMMITMENTS AND CONTINGENCIES

COMMITMENTS AND CONTINGENCIES	12 Months Ended
COMMITMENTS AND CONTINGENCIES	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	Commitments and Contingencies On June 24, 2014, the Company entered into a lease agreement for approximately 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 phases, 2,300 square feet of space which commenced on July 1, 2014 at an initial monthly rent of $5,900 per month and 15,600 square feet of space which commenced on March 27, 2015 at an initial monthly rent of $18,200 per month. The leased property is subject to a 3% annual rent increase following availability that result 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 lease will expire on January 31, 2018. Future minimum payments required under the lease are summarized as follows (in thousands): Year Ending December 31: 2017 $ 305 2018 25 Thereafter — Total minimum lease payments $ 330 Total lease expense for the years ended December 31, 2016 , 2015 and 2014 was $0.8 million , $0.6 million and $ 0.4 million , respectively.

QUARTERLY FINANCIAL DATA

QUARTERLY FINANCIAL DATA	12 Months Ended
QUARTERLY FINANCIAL DATA	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Data	Selected Quarterly Financial Data (Unaudited) The following is a summary of the quarterly results of the Company for the years ended December 31, 2016 and 2015 (unaudited, in thousands, except for per share data): Three Months Ended Year Ended 3/31/16 6/30/16 9/30/16 12/31/16 December 31, 2016 Operating Loss $ (22,118 ) $ (22,227 ) $ (19,581 ) $ (19,853 ) $ (83,779 ) Net loss (21,914 ) (22,061 ) (19,421 ) (19,722 ) (83,118 ) Per common share: Loss per share, basic and diluted (1) $ (1.13 ) $ (1.11 ) $ (0.97 ) $ (0.99 ) $ (4.20 ) Three Months Ended Year Ended 3/31/15 6/30/15 9/30/15 12/31/15 December 31, 2015 Operating Loss $ (11,986 ) $ (15,516 ) $ (18,724 ) $ (18,488 ) $ (64,714 ) Net loss (11,940 ) (15,446 ) (18,741 ) (18,417 ) (64,544 ) Per common share: Loss per share, basic and diluted (1) $ (0.77 ) $ (0.95 ) $ (1.11 ) $ (0.96 ) $ (3.82 ) (1) Net loss per share is computed independently for each of the quarters presented. Therefore, the sum of the quarterly per-share calculations will not necessarily equal the annual per share calculation.

SUBSEQUENT EVENTS

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2016
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events Sale of Common Stock In January 2017, the Company sold 5,002,702 million shares of our common stock at a public offering price of $5.60 per share and sold warrants to purchase up to 7,258,263 shares of our common stock at a public offering price of $5.599 per warrant share. The public offering price for the warrants was equal to the public offering price of the common stock, less the $0.001 per share exercise price of each warrant. After deducting underwriter discounts and offering expenses, the Company received net proceeds from the transaction of $66.8 million .

SUMMARY OF SIGNIFICANT ACCOUN23

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of presentation	Basis of Presentation These consolidated financial statements are prepared in accordance with accounting principles generally accepted in the United States ("U.S. GAAP"). These consolidated financial statements include the accounts of the Company, MethylGene and MethylGene US Inc. All significant inter-company transactions, balances and expenses have been eliminated upon consolidation. Mirati was incorporated under the laws of the State of Delaware on April 29, 2013. On May 8, 2013, the Company's Board of Directors approved and the Company entered into an arrangement agreement ("Arrangement") with MethylGene. Upon completion of the Arrangement, MethylGene became the Company's wholly-owned subsidiary. These consolidated financial statements are presented in United States ("U.S.") Dollars, which effective January 1, 2013, is also the functional currency of the Company.
Use of Estimates	Use of Estimates The preparation of the Company's audited consolidated financial statements in conformity with U.S. GAAP 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 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. 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, with unrealized gains and losses included as a separate component of stockholders’ equity. Realized gains and losses from the sale of available-for-sale securities or the amounts, net of tax, reclassified out of accumulated other comprehensive income, if any, are determined on a specific identification basis.
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.
Property and equipment	Property and Equipment, Net Property and equipment is stated at historical cost less accumulated depreciation. Historical cost includes expenditures that are directly attributable to the acquisition of the items. All repairs and maintenance are charged to net loss during the financial period in which they are incurred. Depreciation of property and equipment is calculated using the straight-line method over the estimated useful lives of the assets, as follows: Computer equipment 3 years Office and other equipment 6 years Laboratory equipment 6 years Leasehold improvements The lesser of the lease term or the life of the asset On disposal or impairment of property and equipment, the cost and related accumulated depreciation is removed from the consolidated financial statements and the net amount, less any proceeds, is included in net loss.
Impairment of long-lived assets	Impairment of Long-Lived Assets The Company reviews its long-lived assets for impairment whenever events or changes in circumstances indicate that the carrying value of an asset may not be recoverable. If such circumstances are determined to exist, an estimate of undiscounted future cash flows produced by the long-lived asset, including its eventual residual value, is compared to the carrying value to determine whether impairment exists. In the event that such cash flows are not expected to be sufficient to recover the carrying amount of the assets, the assets are written-down to their estimated fair values. Fair value is estimated through discounted cash flow models to project cash flows from the asset.
Reclassification of warrants	Reclassification of Warrants In 2011 and 2012, MethylGene issued common stock warrants in connection with the issuance of common stock through private placements (the "2011 Warrants" and the "2012 Warrants"). The exercise prices of the 2011 and 2012 Warrants were denominated in Canadian dollars. Upon the issuance of the 2011 and 2012 Warrants, the net proceeds were allocated to common stock and warrants based on their relative fair values, and the fair value of the issued common stock warrants was calculated utilizing the Black-Scholes option-pricing model. The allocated fair value was then recorded as warrants within stockholders’ equity on the consolidated balance sheet. Effective January 1, 2013, the Company changed its functional currency which changed how the 2011 and 2012 warrants were accounted for as they continued to have exercise prices denominated in Canadian dollars. At each reporting period subsequent to January 1, 2013, the fair value of the warrant liability was recalculated and any corresponding increase or decrease to the warrant liability was recorded as change in fair value of warrant liability on the consolidated statement of operations and comprehensive loss. The estimated fair value was determined using the Black-Scholes option-pricing model based on the estimated value of the underlying common stock at the valuation measurement date, the remaining contractual term of the warrants, risk-free interest rates, expected dividends and expected volatility of the price of the underlying common stock. During the second half of 2014, the Company amended all of its outstanding warrant agreements to allow for the warrants to be denominated in U.S. Dollars. As a result of this amendment, the amended warrants qualified for equity classification and were reclassified into stockholders’ equity at their fair value as of the amendment date, and as of the amendment date, revaluations of fair value are no longer required.
Share-based compensation	Share-Based Compensation We measure and recognize compensation expense for share-based payments based on estimated fair value. We estimate the fair value of stock options granted using the Black-Scholes option-pricing model. The Black-Scholes option-pricing model requires the use of certain estimates and highly judgmental assumptions that affect the amount of share-based compensation expense recognized in our consolidated financial statements. These assumptions include the historical volatility of our stock price, expected term of the options, the risk-free interest rate and expected dividend yields. Share-based compensation is recognized using the graded accelerated vesting method. If any of the assumptions used in our calculation change significantly, share-based compensation expense may differ materially from what we have recorded in the current period.
Investment tax credits	Investment Tax Credits The Company's accounts include claims for investment tax credits ("ITCs") relating to scientific research and experimental development activities of the Company. The qualification and recording of these activities for investment tax credit purposes are established by the Canadian federal and Provincial Tax Acts and are subject to audit by the taxation authorities. Refundable ITCs are reflected as reductions of expenses or reductions of the cost of the assets to which they relate when there is reasonable assurance that the assistance will be received and all conditions have been complied with. The non-refundable ITCs are carried forward for a time and will be recognized when it is more likely than not that the Company will become subject to Canadian federal taxes, at which time, these ITCs will be applied as a reduction of tax expense.
Research and development expenses	Research and Development Expenses Research and development expenditures are charged to net loss in the period in which they are incurred and are comprised of the following types of costs incurred in performing research and development activities: clinical trial and related clinical manufacturing costs, salaries and benefits including share-based compensation expense, costs for allocated facilities and depreciation of equipment, contract services, license fees paid in connection with our early discovery efforts and data management costs.
Income taxes	Income Taxes Income taxes have been accounted for using the asset and liability method. Under the asset and liability method, deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial carrying amounts of existing assets and liabilities and their respective tax bases and operating loss and tax credit carryforwards. Deferred tax assets and liabilities are measured using enacted tax rates applicable to taxable income in the years in which those temporary differences are expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in net loss in the period that includes the enactment date. A valuation allowance against deferred tax assets is recorded if, based upon the weight of all available evidence, it is more likely than not that some or all of the deferred tax assets will not be realized. For uncertain tax positions that meet "a more likely than not" threshold, the Company recognizes the benefit of uncertain tax positions in the consolidated financial statements.
Segment Reporting	Segment Reporting Operating segments are components of a business where separate discrete financial information is available for evaluation by the chief operating decision-maker for purposes of making decisions regarding resource allocation and assessing performance. To date, the Company has viewed its operations and managed its business as one segment operating primarily in the United States.
Net loss per share	Net Loss Per Share Basic net loss per common share is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration for potentially dilutive securities. Diluted net loss per share is computed by dividing the net loss attributable to common stockholders by the weighted-average number of common shares and potentially dilutive securities 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.
Fair value measurement	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.

SUMMARY OF SIGNIFICANT ACCOUN24

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Tables)	Dec. 31, 2016
Accounting Policies [Abstract]
Schedule of estimated useful lives of assets	Depreciation of property and equipment is calculated using the straight-line method over the estimated useful lives of the assets, as follows: Computer equipment 3 years Office and other equipment 6 years Laboratory equipment 6 years Leasehold improvements The lesser of the lease term or the life of the asset
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 potentially dilutive securities not included in the calculation of diluted net loss per share due to the anti-dilutive effect of the securities: Year ended December 31, 2016 2015 2014 Common stock options 173,776 582,662 253,595 Common stock warrants 315,834 1,546,201 1,515,445 Total 489,610 2,128,863 1,769,040

INVESTMENTS (Tables)

INVESTMENTS (Tables)	12 Months Ended
INVESTMENTS (Tables)	Dec. 31, 2016
Investments, Debt and Equity Securities [Abstract]
Schedule of Available-for-sale and Trading Securities Reconciliation	The following tables summarize our short-term investments (in thousands): As of December 31, 2016 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 1 year or less $ 20,622 $ — $ (3 ) $ 20,619 Commercial paper 1 year or less 13,717 15 — 13,732 $ 34,339 $ 15 $ (3 ) $ 34,351 As of December 31, 2015 Maturity Amortized cost Gross unrealized gains Gross unrealized losses Estimated fair value Corporate debt securities 1 year or less $ 27,644 $ — $ (22 ) $ 27,622 Commercial paper 1 year or less 45,158 54 — 45,212 $ 72,802 $ 54 $ (22 ) $ 72,834

FAIR VALUE MEASUREMENTS (Tables

FAIR VALUE MEASUREMENTS (Tables)	12 Months Ended
FAIR VALUE MEASUREMENTS (Tables)	Dec. 31, 2016
Fair Value Disclosures [Abstract]
Fair Value, Assets Measured on Recurring Basis	The following table summarizes the assets and liabilities measured at fair value on a recurring basis (in thousands): December 31, 2016 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 2,728 $ 2,728 $ — $ — Money market funds 19,655 19,655 — — Total cash and cash equivalents 22,383 22,383 — — Short-term investments: Corporate debt securities 20,619 — 20,619 — Commercial paper 13,732 — 13,732 — Total short-term investments 34,351 — 34,351 — Total $ 56,734 $ 22,383 $ 34,351 $ — December 31, 2015 Total Level 1 Level 2 Level 3 Assets Cash and cash equivalents: Cash $ 875 $ 875 $ — $ — Money market funds 18,875 18,875 — — Corporate debt securities 6,749 — 6,749 — Commercial paper 22,994 — 22,994 Total cash and cash equivalents 49,493 19,750 29,743 — Short-term investments: Corporate debt securities 27,622 — 27,622 — Commercial paper 45,212 — 45,212 — Total short-term investments 72,834 — 72,834 — Total $ 122,327 $ 19,750 $ 102,577 $ —

OTHER CURRENT ASSETS AND LONG27

OTHER CURRENT ASSETS AND LONG-TERM ASSETS (Tables)	12 Months Ended
OTHER CURRENT ASSETS AND LONG-TERM ASSETS (Tables)	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of other current assets	Other current assets consisted of the following (in thousands): December 31, 2016 2015 Prepaid expenses $ 1,879 $ 2,287 Deposits and other receivables 759 551 Interest receivables 183 237 $ 2,821 $ 3,075

PROPERTY AND EQUIPMENT (Tables)

PROPERTY AND EQUIPMENT (Tables)	12 Months Ended
PROPERTY AND EQUIPMENT (Tables)	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Schedule of property and equipment	Property and equipment, net consisted of the following (in thousands): December 31, 2016 2015 Computer equipment $ 329 $ 329 Office and other equipment 301 256 Laboratory equipment 563 425 Leasehold improvements 63 51 Gross property and equipment 1,256 1,061 Less: Accumulated depreciation (627 ) (447 ) Property and equipment, net $ 629 $ 614

ACCOUNTS PAYABLE AND ACCRUED 29

ACCOUNTS PAYABLE AND ACCRUED LIABILITIES (Tables)	12 Months Ended
ACCOUNTS PAYABLE AND ACCRUED LIABILITIES (Tables)	Dec. 31, 2016
Payables and Accruals [Abstract]
Schedule of accounts payable and accrued liabilities	Accounts payable and accrued liabilities consisted of the following (in thousands): December 31, 2016 2015 Accounts payable $ 6,296 $ 2,104 Accrued clinical, development and other expenses 5,743 5,311 Accrued compensation and benefits 2,923 2,352 Other current liabilities 40 31 $ 15,002 $ 9,798

STOCKHOLDERS' EQUITY (Tables)

STOCKHOLDERS' EQUITY (Tables)	12 Months Ended
STOCKHOLDERS' EQUITY (Tables)	Dec. 31, 2016
Stockholders' Equity Note [Abstract]
Schedule of Shares Reserved for Future Issuance	The following shares were reserved for future issuance: December 31, 2016 Common stock options outstanding and available for future grant 3,452,409 Warrants to purchase common stock 695,383 Employee Stock Purchase Plan 238,872 4,386,664
Schedule of warrants issued and outstanding	As of December 31, 2016 the following warrants for common stock were issued and outstanding: Issue date Expiration date Exercise price Number of warrants outstanding November 21, 2012 November 21, 2017 $ 7.86 695,383

SHARE-BASED COMPENSATION (Table

SHARE-BASED COMPENSATION (Tables)	12 Months Ended
SHARE-BASED COMPENSATION (Tables)	Dec. 31, 2016
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of changes to the number of stock options granted by the Company and their weighted average exercise price	The following table summarizes our stock option activity and related information for the year ended December 31, 2016 : Number of options Weighted average exercise price Weighted-Average Remaining Contractual Term (years) Aggregate Intrinsic Value (millions) Balance outstanding as of December 31, 2015 1,932,880 $ 16.71 Granted 1,082,724 $ 16.90 Exercised (22,132 ) $ 10.85 Canceled/forfeited (172,642 ) $ 20.61 Expired (7,488 ) $ 23.28 Balance outstanding as of December 31, 2016 2,813,342 $ 16.57 7.0 $ 21.95 Options exercisable at December 31, 2016 1,402,702 $ 15.42 5.3 $ — Options vested and expected to vest at December 31, 2016 2,813,342 $ 16.57 7.0 $ 21.95
Schedule of Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Table Text Block]	Total share-based compensation expense by statement of operations classification is presented below (in thousands): Year ended December 31, 2016 2015 2014 Research and development expense $ 5,461 $ 3,669 $ 2,565 General and administrative expense 5,163 6,585 4,485 $ 10,624 $ 10,254 $ 7,050
Schedule of assumptions used to estimate the fair value of options granted at the date of grant using the Black-Scholes option pricing model	The assumptions used for the specified reporting periods and the resulting estimates of weighted-average estimated fair value per share of options granted during those periods are as follows: Year Ended December 31, 2016 2015 2014 Risk-free interest rate 1.5% 1.5% 2.1% Dividend yield —% —% —% Volatility factor 101.7% 104.3% 113.0% Expected term (in years) 6.0 6.0 6.7 Weighted average estimated fair value per share $13.32 $19.44 $16.09

INCOME TAXES (Tables)

INCOME TAXES (Tables)	12 Months Ended
INCOME TAXES (Tables)	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Schedule of Effective Income Tax Reconciliation	The differences between the effective income tax rate and the statutory tax rates during the years ended 2016 , 2015 and 2014 are as follows (in thousands): Year Ended December 31, 2016 2015 2014 Net loss before tax $ (83,118 ) $ (64,544 ) $ (43,698 ) Statutory combined US federal and state tax rate 34.00 % 34.00 % 39.83 % Statutory federal and state taxes (28,260 ) (21,945 ) (17,405 ) Increase (decrease) in taxes recoverable resulting from: Effect of change in valuation allowance 28,446 22,350 12,273 Non-deductible share-based compensation 1,247 923 930 Non-deductible warrant expenses for tax purposes — — 1,799 Tax credits (2,906 ) (2,430 ) (227 ) Share issue costs - temporary difference (78 ) (184 ) (184 ) Differential in income tax rates of foreign subsidiary 261 31 3,047 Uncertain Tax Positions 3,921 1,961 47 Return to provision and other true-ups (2,619 ) (899 ) — Other differences (12 ) 193 (280 ) Income tax benefit $ — $ — $ —
Schedule of deferred tax	The following table summarizes the significant components of our deferred tax assets (in thousands): December 31, 2016 2015 Deferred tax assets: Tangible and intangible depreciable assets $ 990 $ 199 Stock compensation 6,635 4,429 Provisions 853 725 Financing fees — 78 Net operating loss carry forwards 66,489 42,864 Capital loss carryforward 51 102 Scientific research and experimental development expenditures 5,531 5,552 Research and development tax credits 4,266 2,411 Total gross deferred tax assets 84,815 56,360 Less valuation allowance (84,815 ) (56,360 ) Net deferred tax assets $ — $ —
Schedule of expiration of NOLs	The NOLs expire as follows (in thousands): US Canada Federal State Federal Provincial Expires in: 2030 $ — $ — $ 5,907 $ 5,985 2031 — — 7,059 7,066 2032 — — 13,308 12,433 2033 3,261 2,286 18,623 19,385 2034 7,260 22,162 32,401 31,809 2035 53,345 52,878 1,084 1,084 2036 69,508 — 777 777 $ 133,374 $ 77,326 $ 79,159 $ 78,539
Schedule of reconciliation of the beginning and ending gross amounts of unrecognized tax positions	A reconciliation of the beginning and ending amounts of unrecognized tax positions are as follows (in thousands): Federal Provincial/State December 31, December 31, 2016 2015 2014 2016 2015 2014 Unrecognized tax positions, beginning of year $ 509 $ 42 $ 35 $ 2,274 $ 18 $ 6 Gross increase — current period tax positions 598 445 35 195 259 12 Gross decrease — prior period tax positions (9 ) (4 ) (28 ) — (3 ) — Gross increase — prior period tax positions — 26 — 4,866 2,000 — Expiration of statute of limitations (3 ) — — (2 ) — — Unrecognized tax positions, end of year $ 1,095 $ 509 $ 42 $ 7,333 $ 2,274 $ 18

INVESTMENT TAX CREDITS (Tables)

INVESTMENT TAX CREDITS (Tables)	12 Months Ended
INVESTMENT TAX CREDITS (Tables)	Dec. 31, 2016
INVESTMENT TAX CREDITS
Schedule of non-refundable investment tax credits expiration	The non-refundable investment tax credits expire as follows (in thousands): FEDERAL ITC Expires in: 2030 $ 764 2031 1,000 2032 1,125 2033 1,018 $ 3,907

COMMITMENTS AND CONTINGENCIES (

COMMITMENTS AND CONTINGENCIES (Tables)	12 Months Ended
COMMITMENTS AND CONTINGENCIES (Tables)	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Schedule of future minimum annual payment required in the next year	Future minimum payments required under the lease are summarized as follows (in thousands): Year Ending December 31: 2017 $ 305 2018 25 Thereafter — Total minimum lease payments $ 330

QUARTERLY FINANCIAL DATA (Table

QUARTERLY FINANCIAL DATA (Tables)	12 Months Ended
QUARTERLY FINANCIAL DATA (Tables)	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Data	The following is a summary of the quarterly results of the Company for the years ended December 31, 2016 and 2015 (unaudited, in thousands, except for per share data): Three Months Ended Year Ended 3/31/16 6/30/16 9/30/16 12/31/16 December 31, 2016 Operating Loss $ (22,118 ) $ (22,227 ) $ (19,581 ) $ (19,853 ) $ (83,779 ) Net loss (21,914 ) (22,061 ) (19,421 ) (19,722 ) (83,118 ) Per common share: Loss per share, basic and diluted (1) $ (1.13 ) $ (1.11 ) $ (0.97 ) $ (0.99 ) $ (4.20 ) Three Months Ended Year Ended 3/31/15 6/30/15 9/30/15 12/31/15 December 31, 2015 Operating Loss $ (11,986 ) $ (15,516 ) $ (18,724 ) $ (18,488 ) $ (64,714 ) Net loss (11,940 ) (15,446 ) (18,741 ) (18,417 ) (64,544 ) Per common share: Loss per share, basic and diluted (1) $ (0.77 ) $ (0.95 ) $ (1.11 ) $ (0.96 ) $ (3.82 ) (1) Net loss per share is computed independently for each of the quarters presented. Therefore, the sum of the quarterly per-share calculations will not necessarily equal the annual per share calculation.

SUMMARY OF SIGNIFICANT ACCOUN36

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	12 Months Ended
SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details)	Dec. 31, 2016
Computer equipment
Property and equipment
Estimated useful lives	3 years
Office and other equipment
Property and equipment
Estimated useful lives	6 years
Laboratory equipment
Property and equipment
Estimated useful lives	6 years

SUMMARY OF SIGNIFICANT ACCOUN37

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accounting Policies [Abstract]
Asset Impairment Charges	$ 0	$ 0
Change in fair value of warrant liability included in net loss	$ 0	$ 0	$ 4,517

SUMMARY OF SIGNIFICANT ACCOUN38

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Details 3) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share (in shares)	489,610	2,128,863	1,769,040
Common stock options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share (in shares)	173,776	582,662	253,595
Common stock warrants
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Potentially dilutive securities not included in the calculation of diluted net loss per share (in shares)	315,834	1,546,201	1,515,445

RECENTLY ISSUED AND RECENTLY 39

RECENTLY ISSUED AND RECENTLY ADOPTED ACCOUNTING PRONOUNCEMENTS RECENTLY ISSUED AND RECENTLY ADOPTED ACCOUNTING PRONOUNCEMENTS (Details) $ in Millions	Jan. 01, 2017USD ($)
Accounting Standards Update 2016-09 [Member] \| Accumulated deficit
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative Effect of New Accounting Principle in Period of Adoption	$ 0.4

INVESTMENTS (Details)

INVESTMENTS (Details) - USD ($) $ in Thousands	12 Months Ended
INVESTMENTS (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Amortized cost	$ 34,339	$ 72,802
Available-for-Sale, Gross unrealized gains	15	54
Available-for-Sale, Gross unrealized losses	(3)	(22)
Available-for-Sale, Estimated fair value	$ 34,351	$ 72,834
Corporate debt securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale, maximum maturity period	1 year	1 year
Available-for-Sale, Amortized cost	$ 20,622	$ 27,644
Available-for-Sale, Gross unrealized gains	0	0
Available-for-Sale, Gross unrealized losses	(3)	(22)
Available-for-Sale, Estimated fair value	$ 20,619	$ 27,622
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	$ 13,717	$ 45,158
Available-for-Sale, Gross unrealized gains	15	54
Available-for-Sale, Gross unrealized losses	0	0
Available-for-Sale, Estimated fair value	$ 13,732	$ 45,212

FAIR VALUE MEASUREMENTS (Detail

FAIR VALUE MEASUREMENTS (Details) - Recurring basis - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 22,383	$ 49,493
Short-term investments	34,351	72,834
Assets, Fair Value Disclosure, Recurring	56,734	122,327
Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	22,383	19,750
Assets, Fair Value Disclosure, Recurring	22,383	19,750
Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		29,743
Short-term investments	34,351	72,834
Assets, Fair Value Disclosure, Recurring	34,351	102,577
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	20,619	27,622
Corporate debt securities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	20,619	27,622
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	13,732	45,212
Commercial paper \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Short-term investments	13,732	45,212
Cash
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	2,728	875
Cash \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	2,728	875
Money market funds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	19,655	18,875
Money market funds \| Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure	$ 19,655	18,875
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		6,749
Corporate debt securities \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		6,749
Commercial paper
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		22,994
Commercial paper \| Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and Cash Equivalents, Fair Value Disclosure		$ 22,994

OTHER CURRENT ASSETS AND LONG42

OTHER CURRENT ASSETS AND LONG-TERM ASSETS (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 1,879	$ 2,287
Deposits and other receivables	759	551
Interest receivables	183	237
Other current assets	2,821	3,075
Other Assets, Noncurrent [Abstract]
Deposits paid for research and development	$ 3,300	$ 2,000

PROPERTY AND EQUIPMENT (Details

PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	12 Months Ended
PROPERTY AND EQUIPMENT (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Property and equipment
Property and equipment, gross	$ 1,256	$ 1,061
Less: Accumulated depreciation	(627)	(447)
Property and equipment, net	629	614
Depreciation expenses	180	212	$ 199
Computer equipment
Property and equipment
Property and equipment, gross	329	329
Office and other equipment
Property and equipment
Property and equipment, gross	301	256
Laboratory equipment
Property and equipment
Property and equipment, gross	563	425
Leasehold improvements
Property and equipment
Property and equipment, gross	$ 63	$ 51

ACCOUNTS PAYABLE AND ACCRUED 44

ACCOUNTS PAYABLE AND ACCRUED LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accounts payable	$ 6,296	$ 2,104
Accrued expenses	5,743	5,311
Accrued compensation and benefits	2,923	2,352
Other Accrued Liabilities, Current	40	31
Total accounts payable and accrued liabilities	$ 15,002	$ 9,798

STOCKHOLDERS' EQUITY (Details)

STOCKHOLDERS' EQUITY (Details)	Dec. 31, 2016shares
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	4,386,664
Warrants to purchase common stock
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	695,383
Stock Option Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	3,452,409
Employee Stock Purchase Plan
Class of Stock [Line Items]
Common stock reserved for future issuance (in shares)	238,872

STOCKHOLDERS' EQUITY (Details 2

STOCKHOLDERS' EQUITY (Details 2) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Nov. 21, 2012
Warrants - issued and outstanding
Exercise of warrants for cash (in shares)	313,756
Proceeds from issuance of common stock, net of issuance costs	$ 2.1
Number of warrants exercised (in shares)	289,789	1,037,330	73,964
Net exercise of warrants (in shares)	603,545	809,498	43,526
Common Stock
Warrants - issued and outstanding
Exercise of warrants for cash (in shares)	313,756
Net exercise of warrants (in shares)	289,789	809,498	43,526
Private Placement November 2012 \| November 21, 2012 Warrants
Warrants - issued and outstanding
Exercise price (in dollars per share)				$ 7.86
Number of warrants (in shares)	695,383

SHARE-BASED COMPENSATION (Detai

SHARE-BASED COMPENSATION (Details) - USD ($)	12 Months Ended
SHARE-BASED COMPENSATION (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	May 31, 2013
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for issue	600,000
Exercise price required percentage of fair market value	100.00%
Award vesting period	4 years
Intrinsic value of options exercised	$ 300,000	$ 600,000	$ 600,000
Cash received from exercise of stock options	200,000	600,000	900,000
Fair value of options vested	8,600,000	6,500,000	3,000,000
Capitalized costs	0	0	0
Tax benefit from compensation expense	0	$ 0	$ 0
Compensation cost not yet recognized	$ 8,000,000
Compensation cost not yet recognized, period for recognition	1 year 3 months
Stock Option Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option contractual terms	5 years
Stock Option Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option contractual terms	7 years
2013 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employee Stock Purchase Plan, Shares Authorized for Purchase	$ 25,000
Employee Stock Purchase Plan, Purchase Discount, Percent	85.00%
Employee Stock Purchase Plan, Shares Reserved for Future Issuance				300,000
Issuance of common stock from ESPP purchase (in shares)	61,128
2013 Plan \| Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option contractual terms	7 years
2013 Plan \| Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock option contractual terms	10 years

SHARE-BASED COMPENSATION (Det48

SHARE-BASED COMPENSATION (Details 2) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance, beginning of year (in shares) \| shares	1,932,880
Granted (in shares) \| shares	1,082,724
Exercise of options (in shares) \| shares	(22,132)
Canceled (in shares) \| shares	(172,642)
Expired (in shares) \| shares	(7,488)
Balance, end of year (in shares) \| shares	2,813,342
Options exercisable, end of year (in shares) \| shares	1,402,702
Vested and unvested expected to vest options outstanding (in shares) \| shares	2,813,342
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Balance, beginning of year (in dollars per share) \| $ / shares	$ 16.71
Granted (in dollars per share) \| $ / shares	16.90
Exercised (in dollars per share) \| $ / shares	10.85
Canceled (in dollars per share) \| $ / shares	20.61
Expired (in dollars per share) \| $ / shares	23.28
Balance, end of year (in dollars per share) \| $ / shares	16.57
Options exercisable, end of year (in dollars per share) \| $ / shares	15.42
Vested and unvested expected to vest options outstanding, Weighted-Average Exercise Price (in dollars per share) \| $ / shares	$ 16.57
Options outstanding, Weighted-Average Remaining Contractual Term (years)	7 years
Options exercisable, Weighted-Average Remaining Contractual Term (years)	5 years 3 months
Options vested and expected to vest, Weighted-Average Remaining Contractual Term (years)	7 years
Options outstanding, Aggregate Intrinsic Value \| $	$ 21,950
Options exercisable, Aggregate Intrinsic Value \| $	0
Options vested and expected to vest, Aggregate Intrinsic Value \| $	$ 21,950

SHARE-BASED COMPENSATION (Det49

SHARE-BASED COMPENSATION (Details 3) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 10,624	$ 10,254	$ 7,050
Research and development expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	5,461	3,669	2,565
General and administrative expense
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,163	$ 6,585	$ 4,485

SHARE-BASED COMPENSATION (Det50

SHARE-BASED COMPENSATION (Details 4) - $ / shares	12 Months Ended
SHARE-BASED COMPENSATION (Details 4) - $ / shares	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Risk-free interest rate	1.50%	1.50%	2.10%
Dividend yield	0.00%	0.00%	0.00%
Volatility factor	101.70%	104.30%	113.00%
Expected term (in years)	6 years	6 years	6 years 8 months 12 days
Weighted average estimated fair value per share	$ 13.32	$ 19.44	$ 16.09

EMPLOYEE BENEFIT PLAN (Details)

EMPLOYEE BENEFIT PLAN (Details) - USD ($)	12 Months Ended
EMPLOYEE BENEFIT PLAN (Details) - USD ($)	Dec. 31, 2016	Dec. 31, 2015
Compensation and Retirement Disclosure [Abstract]
Percentage of employee contributions matched	4.00%
Maximum employer contribution per employee	$ 2,500
Matching contribution amount	$ 100,000	$ 100,000

INCOME TAXES (Details)

INCOME TAXES (Details)	12 Months Ended
INCOME TAXES (Details)	Dec. 31, 2016USD ($)ongoing_tax_audit	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Net loss before tax	$ (83,118,000)	$ (64,544,000)	$ (43,698,000)
Statutory combined US federal and state tax rate (2012 - statutory combined Canadian federal and provincial tax rate)	34.00%	34.00%	39.83%
Statutory federal and provincial taxes	$ (28,260,000)	$ (21,945,000)	$ (17,405,000)
Effect of change in valuation allowance	28,446,000	22,350,000	12,273,000
Non-deductible share-based compensation	1,247,000	923,000	930,000
Non-deductible warrant expenses for tax purposes	0	0	1,799,000
Tax credits	(2,906,000)	(2,430,000)	(227,000)
Share issue costs - temporary difference	(78,000)	(184,000)	(184,000)
Differential in income tax rates of foreign subsidiary	261,000	31,000	3,047,000
Uncertain Tax Positions	3,921,000	1,961,000	47,000
Return to provision and other true-ups	(2,619,000)	(899,000)	0
Other differences	(12,000)	193,000	(280,000)
Income tax expense (benefit)	0	0	0
Deferred tax asset
Tangible and intangible depreciable assets	990,000	199,000
Stock compensation	6,635,000	4,429,000
Provisions	853,000	725,000
Financing fees	0	78,000
Net operating loss carry forwards	66,489,000	42,864,000
Capital loss carryforward	51,000	102,000
Scientific research and experimental development expenditures	5,531,000	5,552,000
Research and development tax credits	4,266,000	2,411,000
Total gross deferred tax assets	84,815,000	56,360,000
Less valuation allowance	(84,815,000)	(56,360,000)
Net deferred tax assets	0	0
Additional disclosures
Amount of increase in valuation allowance	(28,500,000)
Reconciliation of the beginning and ending gross amounts of unrecognized tax positions
Accrual for interest or penalties on tax matters	$ 0
Number of ongoing tax audits \| ongoing_tax_audit	0
Domestic Tax Authority
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Income tax expense (benefit)	$ 0	0	0
Canadian Federal
Additional disclosures
Scientific research and experimental development expenses deductible for income tax purposes	19,900,000	19,900,000	20,100,000
Net operating loss carry forwards (NOLs)	79,159,000
Reconciliation of the beginning and ending gross amounts of unrecognized tax positions
Unrecognized tax positions, beginning of year	509,000	42,000	35,000
Gross increase — current period tax positions	598,000	445,000	35,000
Gross decrease — prior period tax positions	(9,000)	(4,000)	(28,000)
Gross increase — prior period tax positions	0	26,000	0
Expiration of statute of limitations	(3,000)	0	0
Unrecognized tax positions, end of year	1,095,000	509,000	42,000
Canadian Federal \| 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	5,907,000
Canadian Federal \| 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	7,059,000
Canadian Federal \| 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	13,308,000
Canadian Federal \| 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	18,623,000
Canadian Federal \| 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	32,401,000
Canadian Federal \| 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	1,084,000
Canadian Federal \| 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	777,000
Canadian Provincial
Additional disclosures
Scientific research and experimental development expenses deductible for income tax purposes	21,600,000	21,600,000	22,700,000
Net operating loss carry forwards (NOLs)	78,539,000
Reconciliation of the beginning and ending gross amounts of unrecognized tax positions
Unrecognized tax positions, beginning of year	2,274,000	18,000	6,000
Gross increase — current period tax positions	195,000	259,000	12,000
Gross decrease — prior period tax positions	0	(3,000)	0
Gross increase — prior period tax positions	4,866,000	2,000,000	0
Expiration of statute of limitations	(2,000)	0	0
Unrecognized tax positions, end of year	7,333,000	$ 2,274,000	$ 18,000
Canadian Provincial \| 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	5,985,000
Canadian Provincial \| 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	7,066,000
Canadian Provincial \| 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	12,433,000
Canadian Provincial \| 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	19,385,000
Canadian Provincial \| 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	31,809,000
Canadian Provincial \| 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	1,084,000
Canadian Provincial \| 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	777,000
US Federal
Additional disclosures
Net operating loss carry forwards (NOLs)	133,374,000
US Federal \| 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal \| 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal \| 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US Federal \| 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	3,261,000
US Federal \| 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	7,260,000
US Federal \| 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	53,345,000
US Federal \| 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	69,508,000
US Federal \| Research Tax Credit Carryforward
Additional disclosures
Tax credit carryforward	4,400,000
US State
Additional disclosures
Net operating loss carry forwards (NOLs)	77,326,000
US State \| 2030
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State \| 2031
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State \| 2032
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State \| 2033
Additional disclosures
Net operating loss carry forwards (NOLs)	2,286,000
US State \| 2034
Additional disclosures
Net operating loss carry forwards (NOLs)	22,162,000
US State \| 2035
Additional disclosures
Net operating loss carry forwards (NOLs)	52,878,000
US State \| 2036
Additional disclosures
Net operating loss carry forwards (NOLs)	0
US State \| Research Tax Credit Carryforward
Additional disclosures
Tax credit carryforward	$ 2,000,000

INVESTMENT TAX CREDITS (Details

INVESTMENT TAX CREDITS (Details) - Canadian Federal $ in Thousands	12 Months Ended
	Dec. 31, 2016USD ($)
INVESTMENT TAX CREDITS
Non-refundable ITCs related to scientific research and development expenditures	$ 3,907
2,030
INVESTMENT TAX CREDITS
Non-refundable ITCs related to scientific research and development expenditures	764
2,031
INVESTMENT TAX CREDITS
Non-refundable ITCs related to scientific research and development expenditures	1,000
2,032
INVESTMENT TAX CREDITS
Non-refundable ITCs related to scientific research and development expenditures	1,125
2,033
INVESTMENT TAX CREDITS
Non-refundable ITCs related to scientific research and development expenditures	$ 1,018

COMMITMENTS AND CONTINGENCIES54

COMMITMENTS AND CONTINGENCIES (Details)	9 Months Ended		12 Months Ended
COMMITMENTS AND CONTINGENCIES (Details)	Sep. 30, 2015USD ($)	Mar. 26, 2015USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)	Mar. 27, 2015ft²	Jul. 01, 2014ft²	Jun. 24, 2014ft²
Future minimum annual payments
2,017			$ 305,000
2,018			25,000
Thereafter			0
Total minimum lease payments			330,000
Operating Leases, Rent Expense, Net [Abstract]
Lease expense			$ 800,000	$ 600,000	$ 400,000
Building
Operating Leased Assets [Line Items]
Area of space leased \| ft²								18,000
Annual rent increase (percent)	3.00%
Building \| Lease Agreement Phase One
Operating Leased Assets [Line Items]
Area of space leased \| ft²							2,300
Monthly lease rent		$ 5,900
Building \| Lease Agreement Phase Two
Operating Leased Assets [Line Items]
Area of space leased \| ft²						15,600
Monthly lease rent	$ 18,200

QUARTERLY FINANCIAL DATA (Detai

QUARTERLY FINANCIAL DATA (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Operating Loss	$ (19,853)	$ (19,581)	$ (22,227)	$ (22,118)	$ (18,488)	$ (18,724)	$ (15,516)	$ (11,986)	$ (83,779)	$ (64,714)	$ (39,104)
Net loss	$ (19,722)	$ (19,421)	$ (22,061)	$ (21,914)	$ (18,417)	$ (18,741)	$ (15,446)	$ (11,940)	$ (83,118)	$ (64,544)	$ (43,698)
Loss per share, basic (in US$ per share)	$ (0.99)	$ (0.97)	$ (1.11)	$ (1.13)	$ (0.96)	$ (1.11)	$ (0.95)	$ (0.77)	$ (4.20)	$ (3.82)

SUBSEQUENT EVENTS (Details)

SUBSEQUENT EVENTS (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	12 Months Ended
	Jan. 31, 2017	Dec. 31, 2015
Subsequent Event
Subsequent Event [Line Items]
Share Price	$ 5.599
Class of Warrant or Right, Number of Securities Called by Warrants or Rights	7,258,263
Class of Warrant or Right, Exercise Price of Warrants or Rights	$ 0.001
Sale of Stock, Consideration Received on Transaction	$ 66.8
Common Stock
Subsequent Event [Line Items]
Issuance of common stock, net of costs (in shares)		4,837,500
Common Stock \| Subsequent Event
Subsequent Event [Line Items]
Issuance of common stock, net of costs (in shares)	5,002,702
Share Price	$ 5.60