DEI Document - USD ($)	12 Months Ended
DEI Document - USD ($)	Dec. 31, 2016	Feb. 28, 2017	Jun. 30, 2016
Entity [Abstract]
Entity Registrant Name	Bellicum Pharmaceuticals, Inc.
Entity Central Index Key	0001358403
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2016
Document Fiscal Year Focus	2016
Document Fiscal Period Focus	Q4
Amendment Flag	false
Entity Common Stock, Shares Outstanding		27,157,680
Entity Well-known Seasoned Issuer	No
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 251,404,832

Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 33,140	$ 70,241
Investment securities, available for sale	70,632	23,820
Accounts receivable, interest and other receivables	334	440
Prepaid expenses and other current assets	1,504	2,389
Total current assets	105,610	96,890
Investment securities, available for sale - long-term	0	56,304
Property and equipment, net	16,504	6,882
Restricted cash	9,640	0
Other assets	283	330
TOTAL ASSETS	132,037	160,406
Current liabilities:
Accounts payable	3,623	2,106
Accrued expenses and other current liabilities	9,363	5,080
Current maturity of long-term debt	1,787	0
Current portion of capital lease obligations	21	13
Current portion of deferred rent	319	246
Total current liabilities	15,113	7,445
Long-term liabilities:
Long-term debt	18,436	0
Capital lease obligations	141	118
Deferred rent	1,773	826
TOTAL LIABILITIES	35,463	8,389
Commitments and contingencies: (Note 12)
Stockholders’ Equity:
Preferred stock: $0.01 par value; 10,000,000 shares authorized: no shares issued and outstanding	0	0
Common stock: $0.01 par value; 200,000,000 shares authorized at December 31, 2016 and 2015; 27,833,028 shares issued and 27,155,565 shares outstanding at December 31, 2016; 27,609,344 shares issued and 26,931,881 shares outstanding at December 31, 2015	278	276
Treasury stock: 677,463 shares held at December 31, 2016 and 2015	(5,056)	(5,056)
Additional paid-in capital	332,068	318,591
Accumulated other comprehensive income (loss)	17	(302)
Accumulated deficit	(230,733)	(161,492)
Total stockholders’ equity	96,574	152,017
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY	$ 132,037	$ 160,406

Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Common stock, par value (in usd per share)	$ 0.01	$ 0.01
Common stock, authorized (in shares)	200,000,000	200,000,000
Common stock, issued (in shares)	27,833,028	27,609,344
Common stock, outstanding (in shares)	27,155,565	26,931,881
Treasury stock (in shares)	677,463	677,463

Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
REVENUES
Grants	$ 388	$ 282	$ 1,780
Total revenues	388	282	1,780
OPERATING EXPENSES
Research and development	51,263	33,561	12,071
License fees	580	3,184	0
ARIAD restructuring costs	0	0	43,212
General and administrative	16,925	12,672	4,335
Total operating expenses	68,768	49,417	59,618
LOSS FROM OPERATIONS	(68,380)	(49,135)	(57,838)
OTHER INCOME (EXPENSE)
Interest income	909	641	35
Interest expense	(1,760)	(12)	(1,791)
Loss on disposal of assets	(10)	(42)	0
Change in fair value of warrant liability	0	0	(24,371)
Total other income (expense)	(861)	587	(26,127)
NET LOSS	(69,241)	(48,548)	(83,965)
Preferred stock dividends	0	0	(1,432)
Net loss attributable to common stockholders	$ (69,241)	$ (48,548)	$ (85,397)
Net loss per share attributable to common shareholders - basic and diluted	$ (2.57)	$ (1.84)	$ (34.04)
Weighted-average shares outstanding-basic and diluted	26,950,906	26,346,603	2,508,960
Net Loss	$ (69,241)	$ (48,548)	$ (83,965)
Other comprehensive loss:
Unrealized gain (loss) on securities, net	319	(302)	0
Comprehensive loss	$ (68,922)	$ (48,850)	$ (83,965)

Statements of Redeemable and Convertible Preferred Stock and Stockholders’ Equity (Deficit) - USD ($) $ in Thousands	Total	Preferred Stock Series A Preferred Stock	Preferred Stock Series B Preferred Stock	Preferred Stock Series C Preferred Stock	Common Stock	Treasury Stock	Additional Paid-in Capital	Accumulated Deficit	Other Comprehensive Loss
Balance, beginning of period (in shares) at Dec. 31, 2013		(2,544,539)	(6,563,283)	0	(1,725,992)	0
Balance, beginning of period at Dec. 31, 2013	$ (28,152)	$ 7,634	$ 32,292	$ 0	$ 17	$ 0	$ 810	$ (28,979)	$ 0
Increase (Decrease) in Stockholders' Equity
Share-based compensation	911						911
Issuance of restricted stock grant (in shares)					117,647
Issuance of restricted stock grant	0				$ 1		(1)
Exercise of stock options (in shares)					12,615
Exercise of stock options	11						11
Issuance of common stock in an IPO, net of issuance costs (in shares)					8,452,500
Issuance of common stock in an IPO, net of issuance costs	146,303				$ 85		146,218
Issuance of preferred stock, net of issuance costs (in shares)			1,582,706	10,091,743
Issuance of preferred stock, net of issuance costs	0		$ 7,320	$ 42,074
Exercise of Series C warrants, net of issuance costs (in shares)				6,524,195
Exercise of Series C warrants, net of issuance costs	0			$ 72,187
Exercise of common warrants (in shares)					510,524
Exercise of common warrants	250				$ 5		245
Accretion of Series B dividend	(1,432)		1,432				(1,432)
Payment of Series B dividend	0		$ (173)
Repurchase of common stock held by ARIAD (in shares)						(677,463)
Repurchase of common stock held by ARIAD	(5,056)					$ (5,056)
Conversion of preferred stock (in shares)		(2,544,539)	(8,145,989)	(16,615,938)	16,230,777
Conversion of preferred stock	162,766	$ (7,634)	$ (40,871)	$ (114,261)	$ 163		162,603
Net Loss	(83,965)							(83,965)
Balance, end of period (in shares) at Dec. 31, 2014		0	0	0	(27,050,055)	(677,463)
Balance, end of period at Dec. 31, 2014	191,636	$ 0	$ 0	$ 0	$ 271	$ (5,056)	309,365	(112,944)	0
Increase (Decrease) in Stockholders' Equity
Share-based compensation	$ 8,409						8,409
Exercise of stock options (in shares)	182,238				182,238
Exercise of stock options	$ 482				$ 1		481
Issuance of common stock - Employee Stock Purchase Plan (in shares)					21,690
Issuance of common stock - Employee Stock Purchase Plan	347						347
Exercise of common warrants (in shares)					355,361
Exercise of common warrants	0				$ 4		(4)
Net Loss	(48,548)
Other	(7)						(7)
Comprehensive income (loss)	(48,850)							(48,548)	(302)
Balance, end of period (in shares) at Dec. 31, 2015		0	0	0	(27,609,344)	(677,463)
Balance, end of period at Dec. 31, 2015	152,017	$ 0	$ 0	$ 0	$ 276	$ (5,056)	318,591	(161,492)	(302)
Increase (Decrease) in Stockholders' Equity
Share-based compensation	$ 12,337						12,337
Exercise of stock options (in shares)	190,055				190,055
Exercise of stock options	$ 773				$ 2		771
Issuance of common stock - Employee Stock Purchase Plan (in shares)					33,629
Issuance of common stock - Employee Stock Purchase Plan	369						369
Net Loss	(69,241)
Comprehensive income (loss)	(68,922)							(69,241)	319
Balance, end of period (in shares) at Dec. 31, 2016		0	0	0	(27,833,028)	(677,463)
Balance, end of period at Dec. 31, 2016	$ 96,574	$ 0	$ 0	$ 0	$ 278	$ (5,056)	$ 332,068	$ (230,733)	$ 17

Statements of Cash Flows - USD ($)	12 Months Ended
Statements of Cash Flows - USD ($)	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (69,241,000)	$ (48,548,000)	$ (83,965,000)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation	12,337,000	8,409,000	911,000
Depreciation expense	2,306,000	1,199,000	667,000
Amortization of premium on investment securities, net	539,000	573,000	0
Amortization of lease liability	(119,000)	(94,000)	(89,000)
Amortization of deferred financing costs	422,000	0	0
Loss on disposal of property and equipment	10,000	42,000	0
Loss on disposition of investment securities	0	33,000	0
Change in fair value of warrant liability	0	0	24,371,000
Changes in operating assets and liabilities:
Accounts receivable	106,000	(142,000)	448,000
Prepaid expenses and other current assets	885,000	(1,067,000)	(1,068,000)
Other assets	47,000	(185,000)	339,000
Accounts payable	931,000	897,000	659,000
Accrued liabilities and other	1,336,000	2,778,000	225,000
Deferred revenue – grants	0	(13,000)	13,000
Deferred rent	0	859,000	5,000
Deferred manufacturing costs	0	(467,000)	176,000
NET CASH USED IN OPERATING ACTIVITIES	(50,441,000)	(35,726,000)	(57,308,000)
CASH FLOWS FROM INVESTING ACTIVITIES:
Proceeds from sale of investment securities	42,548,000	20,617,000	0
Purchases of investment securities	(33,276,000)	(101,649,000)	0
Purchases of property and equipment	(7,220,000)	(5,421,000)	(804,000)
CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES	2,052,000	(86,453,000)	(804,000)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from debt	20,000,000	0	386,000
Payments on debt	0	0	(1,187,000)
Payment of debt issuance costs	(199,000)	0	0
Payment on capital lease obligations	(15,000)	(4,000)	0
Proceeds from issuance of common stock	0	0	160,609,000
Proceeds from exercise of stock options	773,000	482,000	0
Proceeds from issuance of common stock - ESPP	369,000	347,000	0
Payment of issuance costs on common stock	0	(7,000)	(14,242,000)
Proceeds from issuance of preferred stock	0	0	62,320,000
Payment of issuance costs on preferred stock	0	0	(3,524,000)
Proceeds from exercise of preferred warrants	0	0	39,145,000
Proceeds from exercise of common warrants	0	0	249,701
Payment for repurchase of common stock	0	0	(5,056,000)
Payment of preferred dividends	0	0	(155,000)
NET CASH PROVIDED BY FINANCING ACTIVITIES	20,928,000	818,000	238,546,000
NET CHANGE IN CASH, CASH EQUIVALENTS AND RESTRICTED CASH	(27,461,000)	(121,361,000)	180,434,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT BEGINNING OF YEAR	70,241,000	191,602,000	11,168,000
CASH, CASH EQUIVALENTS AND RESTRICTED CASH AT END OF YEAR	42,780,000	70,241,000	191,602,000
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid during the period for interest	1,136,000	0	1,767,000
NON-CASH INVESTING AND FINANCING ACTIVITIES
Purchases of property and equipment in accounts payables and accrued liabilities	3,533,000	139,000	0
Leasehold improvements paid by landlord	1,139,000	0	0
Accrued debt issuance costs	1,390,000	0	0
Capital lease obligations incurred for equipment	46,000	135,000	0
Preferred stock dividends paid in common stock	0	0	3,196,000
Dividends accreted on preferred stock	$ 0	$ 0	$ 1,432,000

ORGANIZATION AND BUSINESS DESCRIPTION	12 Months Ended
ORGANIZATION AND BUSINESS DESCRIPTION	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ORGANIZATION AND BUSINESS DESCRIPTION	ORGANIZATION AND BUSINESS DESCRIPTION Bellicum Pharmaceuticals, Inc. (the Company or Bellicum), was incorporated in Delaware in July 2004 and is based in Houston, Texas. The Company is a clinical stage biopharmaceutical company focused on discovering and developing novel cellular immunotherapies for various forms of cancer, including both hematological cancers and solid tumors, as well as orphan inherited blood disorders. The Company is devoting substantially all of its present efforts to developing next-generation product candidates in some of the most important areas of cellular immunotherapy, including, hematopoietic stem cell transplantation, CAR T and TCR cell therapy. The Company has not generated any revenue from product sales to date and if the Company does not successfully commercialize any of the Company's product candidates, the Company will not be able to generate product revenue or achieve profitability. As of December 31, 2016, the Company had an accumulated deficit of $230.7 million. The Company is subject to risks common to companies in the biotechnology industry and the future success of the Company is dependent on its ability to successfully complete the development of and obtain regulatory approval for its product candidates, manage the growth of the organization, obtain additional financing necessary in order to develop, launch and commercialize its product candidates, and compete successfully with other companies in its industry.

SIGNIFICANT ACCOUNTING POLICIES

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America. Any reference in these footnotes to applicable guidance is meant to refer to the authoritative U.S. generally accepted accounting principles (GAAP) as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB).

Use of Estimates

The preparation of the financial statements in accordance with GAAP requires management to make certain estimates and judgments that affect the reported amounts of assets, liabilities, and expenses. Actual results could differ from those estimates.

Revenue Recognition

The Company has not yet generated any revenue from product sales. The Company’s sole source of revenue has been grant revenue related to a $5.7 million research grant received from the Cancer Prevention and Research Institute of Texas (CPRIT), covering a three-year period from July 1, 2011 through June 30, 2017, and a $1.3 million research grant from the National Institutes of Health (NIH) covering the period from April 2013 to March 2017. Grant payments received prior to the Company’s performance of work required by the terms of the research grant are recorded as deferred revenue and recognized as grant revenue once work is performed and qualifying costs are incurred. (See Note 10).

Cash and Cash Equivalents

The Company considers all short-term, highly liquid investments with maturity of three months or less from the date of purchase to be cash equivalents.

Investment Securities

Consistent with its investment policy, the Company invests its cash allocated to fund its short-term liquidity requirements with prominent financial institutions in bank depository accounts and institutional money market funds. The Company invests the remainder of its cash in corporate debt securities and municipal bonds rated at least A quality or equivalent, U.S. Treasury notes and bonds and U.S. and state government agency-backed securities.

The Company determines the appropriate classification of investment securities based on whether they represent the investment of funds available for current operations, as defined in ASC 210-10-45-1 and ASC 210-10-45-2. The Company reevaluates its classification as of each balance sheet date. All investment securities owned are classified as available-for-sale. The cost of securities sold is based on the specific identification method. Investment securities are recorded as of each balance sheet date at fair value, with unrealized gains and, to the extent deemed temporary, unrealized losses reported as accumulated other comprehensive gain (loss), a separate component of stockholders' equity. Interest and dividend income on investment securities, accretion of discounts and amortization of premiums and realized gains and losses are included in interest income in the statements of operations and comprehensive income (loss).

An investment security is considered to be impaired when a decline in fair value below its cost basis is determined to be other than temporary. The Company evaluates whether a decline in fair value of an investment security is below its cost basis is other than temporary using available evidence. In the event that the cost basis of the investment security exceeds its fair value, the Company evaluates, among other factors, the amount and duration of the period that the fair value is less than the cost basis, the financial health of and business outlook for the issuer, including industry and sector performance, and operational and financing cash flow factors, overall market conditions and trends, the Company’s intent to sell the investment security and whether it is more likely than not the Company would be required to sell the investment security before its anticipated recovery. If a decline in fair value is determined to be other than temporary, the Company records an impairment charge in the statement of operations and comprehensive loss and establishes a new cost basis in the investment.

Property and Equipment

Leasehold improvements, furniture, equipment and software are recorded at cost and are depreciated using the straight-line method over the estimated useful lives of the related assets, which range from three to five years. Leasehold improvements are amortized over the shorter of the estimated useful life or the remaining lease term.

Impairment of Long-Lived Assets

The Company reviews long-lived assets for impairment when events or changes in business conditions indicate that their carrying value may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset. There were no impairment charges related to long-lived assets for the years ended December 31, 2016, 2015 and 2014.

Debt Issuance Costs

Costs related to debt issuance are presented in the balance sheet as a direct deduction from the carrying amount of the debt liability, consistent with debt discounts and are amortized using the effective interest method. Amortization of debt issuance costs are included in interest expense.

Deferred Rent and Rent

The Company recognizes rent expense for leases with increasing annual rents on a straight-line basis over the term of the lease. The amount of rent expense in excess of cash payments is classified as deferred rent. Any lease incentives received are deferred and amortized over the term of the lease.

Fair Value of Financial Instruments

Accounting standards include disclosure requirements around fair values used for certain financial instruments and establish a fair value hierarchy. The three-tier hierarchy prioritizes valuation inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market, as described further in Note 4.

The Company believes the recorded values of its financial instruments, including cash and cash equivalents, accounts payable and accrued liabilities approximate their fair values due to the short-term nature of these instruments.

Financial Instruments and Credit Risks

Financial instruments that potentially subject the Company to credit risk include cash and cash equivalents, investment securities, and accounts receivable. Cash is deposited in demand accounts in federally insured domestic institutions to minimize risk. Insurance is provided through the Federal Deposit Insurance Corporation (FDIC) and Security Investor Protection Corporation (SIPC). Although the balances in these accounts exceed the federally insured limit from time to time, the Company has not incurred losses related to these deposits.

Equity Issuance Costs

Equity issuance costs represent costs paid to third parties in order to obtain equity financing. These costs have been netted against the proceeds of the equity issuances.

Licenses and Patents

Licenses and patent costs for technologies that are utilized in research and development and have no alternative future use are expensed as incurred. Costs related to the license of patents from third parties and internally developed patents are classified as research and development expenses. Legal costs related to patent applications and maintenance are classified as general and administrative expenses.

Clinical Trials

The Company estimates its clinical trial expense accrual for a given period based on the number of patients enrolled at each site, estimated cost per patient, and the length of time each patient has been in the trial, less amounts previously billed. These accruals are recorded in accrued expenses and other current liabilities, and the related expense is recorded in research and development expense.

Research and Development

Research and development expenses consist of expenses incurred in performing research and development activities, including compensation and benefits for research and development employees and consultants, facilities expenses, overhead expenses, cost of laboratory supplies, manufacturing expenses, fees paid to third parties and other outside expenses.

Research and development costs are expensed as incurred. Clinical trial and other development costs incurred by third parties are expensed as the contracted work is performed. The Company accrues for costs incurred as the services are being provided by monitoring the status of the clinical trial or project and the invoices received from its external service providers. The Company estimates depend on the timeliness and accuracy of the data provided by the vendors regarding the status of each project and total project spending. The Company adjusts its accrual as actual costs become known. Where contingent milestone payments are due to third parties under research and development arrangements, the milestone payment obligations are expensed when the milestone events are achieved.

Collaboration Agreements

The Company enters into collaboration agreements that include varying arrangements regarding which parties perform and bear the costs of research and development activities. The Company may share the costs of research and development activities with a collaborator, or the Company may be reimbursed for all or a significant portion of the costs of the Company's research and development activities. The Company records its internal and third-party development costs associated with these collaborations as research and development expenses. When the Company is entitled to reimbursement of all or a portion of the research and development expenses that it incurs under a collaboration, the Company records those reimbursable amounts as a deduction to the research and development expenses. If the collaboration is a cost-sharing arrangement in which both the Company and its collaborator perform development work and share costs, the Company also recognizes, as research and development expenses in the period when its collaborator incurs development expenses, the portion of the collaborator's development expenses that the Company is obligated to reimburse.

Reclassifications

Certain research and development indirect costs, including facilities and overhead, were previously included in general and administrative costs. These research and development indirect costs are included in research and development expense for the year ended December 31, 2016 and 2015. The results for the year ended December 31, 2014 have been reclassified to conform to the current year presentation. The effect of the reclassification of the results for the year ended December 31, 2014 was to increase research and development expense and reduce general and administrative expense by $1.1 million with no change in total operating expense or net loss.

Contract Manufacturing Services

Contract manufacturing services are expensed as incurred. Prepaid expenses are capitalized and amortized as services are performed.

Share-Based Compensation

The Company accounts for its share-based compensation in accordance with ASC 718, Compensation — Stock Compensation, which requires the measurement and recognition of compensation expense for all share-based payment awards made to employees and directors to be recognized in the financial statements, based on their fair value. The Company measures share-based compensation to consultants in accordance with ASC 505-50, Equity-Based Payments to Non-Employees, and recognizes the fair value of the award over the period the services are rendered.

The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock option awards. The fair value is recognized as expense, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award on a straight-line basis. Prior to the Company’s IPO on December 23, 2014, the determination of the grant date fair value of options using the Black-Scholes option-pricing model was affected by the Company’s estimated common stock fair value, as well as assumptions regarding a number of other complex and subjective variables.

Income Taxes

Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. This method also requires the recognition of future tax benefits such as net operating loss and tax credit carry forwards, to the extent that realization of such benefits is more likely than not. A valuation allowance is recorded when the realization of future tax benefits is uncertain. The Company records a valuation allowance for the full amount of deferred tax assets, which would otherwise be recorded for tax benefits relating to the operating loss and tax credit carryforwards, as realization of such deferred tax assets cannot be determined to be more likely than not.

Deferred tax assets and liabilities are measured using enacted tax rates expected to apply 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 the statement of operations in the period that includes the enactment date.

The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740, Income Taxes. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2016, 2015 and 2014, the Company had no uncertain tax positions and no interest or penalties have been charged to the Company for the years ended December 31, 2016, 2015 and 2014. If incurred, the Company will classify any interest and penalties as a component of interest expense and operating expense, respectively. The Company is subject to routine audits by taxing jurisdictions; however, there are currently no audits for any tax periods in progress. The tax years 2005 through 2016 remain open to examination by the Internal Revenue Service.

Comprehensive Loss

Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period, from transactions, and other events and circumstances from non-owner sources. Components of comprehensive income (loss) includes, among other items, unrealized gains and losses on the changes in fair value of investments. These components are added, net of their related tax effect, to the reported net income (loss) to arrive at comprehensive income (loss). The components of accumulated other comprehensive loss at December 31, 2016 and 2015, on the Company’s balance sheet was comprised of the net unrealized holding losses on the Company’s investment securities. See Note 4 for further detail of the unrealized holding gains and losses on the Company’s investment securities.

Net Loss and Net Loss per Share of Common Stock Attributable to Common Stockholders

Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of share of common stock outstanding during the period without consideration for common stock equivalents. Diluted net loss per share of common stock is the same as basic net loss per share of common stock, since the effects of potentially dilutive securities are antidilutive. The net loss per share of common stock attributable to common stockholders is computed using the two-class method required for participating securities. All series of the Company’s convertible preferred stock are considered to be participating securities as they are entitled to participate in undistributed earnings with shares of common stock. Due to the Company’s net loss, there is no impact on the earnings per share calculation in applying the two-class method since the participating securities have no legal requirement to share in any losses.

The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per shares of common stock attributable to common stockholders for the periods presented as the effect of including such securities would be anti-dilutive.



	Number of shares
	December 31, 2016	December 31, 2015	December 31, 2014
Options to purchase common stock	4,532,120	3,628,973	2,733,793
Unvested shares of restricted stock	58,825	88,236	117,647
Total common stock equivalents	4,590,945	3,717,209	2,851,440

Application of New Accounting Standards

ASU No. 2014-15, “Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern,” became effective for the Company in 2016. ASU No. 2014-15 requires management to evaluate the Company’s ability to meet its obligations as they become due within one year after the date that financial statements are issued. Accordingly, management has assessed the Company’s ability to continue as a going concern through March 31, 2018. In making its assessment, management evaluated the Company’s liquid assets, the Company’s obligations expected to become payable within the period, and the probability of other conditions and events, and concluded that the Company’s ability to continue as a going concern is not in substantial doubt.

ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash,” requires restricted cash to be included with cash and cash equivalents when reconciling the beginning and ending amounts on the statement of cash flows, and requires additional disclosures in the notes to the financial statements. The Company adopted this standard during 2016. See Note 3 to the financial statements included herein.

ASU No. 2015-03, “Simplifying the Presentation of Debt Issuance Costs,” requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. See Note 7 to the financial statements included herein.

ASU No. 2015-17, "Balance Sheet Classification of Deferred Taxes," requires that deferred income tax liabilities and assets be classified as noncurrent in a classified statement of financial position. The Company adopted this standard as of December 31, 2015, prospectively. See Note 13 to the financial statements included herein.

New Accounting Requirements and Disclosures

In January 2016, the FASB issued ASU No. 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 requires that most equity investments be measured at fair value, with subsequent changes in fair value recognized in net income. The pronouncement also impacts financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is not permitted. The Company does not believe that the adoption of this pronouncement will have a material impact on the Company’s financial statements.

In February 2016, the FASB issued ASU No. 2016-02, “Leases,” which requires companies that lease assets to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments, in its balance sheet. The pronouncement will also require additional disclosures about the amount, timing and uncertainty of cash flows arising from leases. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. The Company is currently evaluating the impact of this pronouncement on the Company's financial statements.

In March 2016, the FASB issued ASU No. 2016-09, “Compensation-Stock Compensation,” which simplifies accounting for share-based compensation arrangements, primarily as it relates to accounting for the income tax effects of share-based compensation. Under the pronouncement, an entity can make an entity-wide accounting policy decision to either estimate the number of awards that are expected to vest (current GAAP) or account for forfeitures as they occur. The pronouncement is effective for annual periods beginning after December 31, 2016, with earlier adoption permitted. The Company does not believe the adoption of this standard will have a material impact on the Company's financial statements.

In August 2016, the FASB issued ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments,” which provides guidance on the classification of certain cash receipts and payments in the statement of cash flows. The pronouncement is effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods. Earlier application is permitted in any interim or annual period. The Company does not believe the adoption of this standard will have a material impact on the Company's financial statements.

CASH AND CASH EQUIVALENTS AND RESTRICTED CASH

12 Months Ended

Dec. 31, 2016

Cash and Cash Equivalents [Abstract]

CASH, CASH EQUIVALENTS AND RESTRICTED CASH

As of December 31, 2016, the Company maintained $9.6 million as restricted cash. The funds are being held with an escrow agent to cover the construction of certain manufacturing costs related to the facility lease. This amount is subject to the terms of the escrow agreement in the lease and the requirements specified therein. This amount may decrease as the Company and landlord authorize completion of certain aspects of the building improvements. See Note 12 to the financial statements included herein.

The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the balance sheets that sum to the total of the same such amounts shown in the statements of cash flows.



	December 31, 2016		December 31, 2015
	(in thousands)
Cash and cash equivalents (1)	$	33,140	$	70,241
Restricted cash, noncurrent	9,640		—
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$	42,780	$	70,241

(1) As of December 31, 2016 and 2015, the Company invested approximately $23.5 million and $62.2 million, respectively, in cash equivalent instruments.

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES

The Company follows ASC, Topic 820, Fair Value Measurements and Disclosures, or ASC 820, for application to financial assets. ASC 820 defines fair value, provides a consistent framework for measuring fair value under GAAP and requires fair value financial statement disclosures. ASC 820 applies only to the measurement and disclosure of financial assets that are required or permitted to be measured and reported at fair value under other ASC topics (except for standards that relate to share-based payments such as ASC Topic 718, Compensation – Stock Compensation).

The valuation techniques required by ASC 820 may be based on either observable or unobservable inputs. Observable inputs reflect readily obtainable data from independent sources, and unobservable inputs reflect the Company’s market assumptions.

These inputs are classified into the following hierarchy:

Level 1 Inputs – quoted prices (unadjusted) in active markets for identical assets that the reporting entity has the ability to access at the measurement date;

Level 2 Inputs – inputs other than quoted prices included within Level 1 that are observable for the asset, either directly or indirectly; and

Level 3 Inputs – unobservable inputs for the assets.

The following tables present the Company’s investment securities (including, if applicable, those classified on the Company’s balance sheet as cash equivalents) that are measured at fair value on a recurring basis as of December 31, 2016 and 2015:



			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2016		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)
Cash Equivalents:
Money market funds	23,459		23,459		—		—
U.S. government agency-backed securities	—		—		—		—
Total Cash Equivalents	$	23,459	$	23,459	$	—	$	—

Investment Securities:
U.S. government agency-backed securities	$	25,908	$	—	$	25,908	$	—
Corporate debt securities	42,053		—		42,053		—
Municipal bonds	2,671		—		2,671		—
Total Investment Securities	$	70,632	$	—	$	70,632	$	—

			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2015		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)
Cash Equivalents:
Money market funds	$	52,714	$	52,714	$	—	$	—
U.S. government agency-backed securities	9,500		—		9,500		—
Total Cash Equivalents	$	62,214	$	52,714	$	9,500	$	—

Investment Securities:
U.S. government agency-backed securities	$	22,388	$	—	$	22,388	$	—
Corporate debt securities	51,547		—		51,547		—
Municipal bonds	6,189		—		6,189		—
Total Investment Securities	$	80,124	$	—	$	80,124	$	—

U.S. Treasury, U.S. government agency-backed securities, corporate debt securities and municipal bonds are valued based on various observable inputs such as benchmark yields, reported trades, broker/dealer quotes, benchmark securities and bids.

Management believes that the carrying value of the debt facility approximates its fair value, as the Company's debt facility bears interest at a rate that approximates prevailing market rates for instruments with similar characteristics. The fair value of the Company's debt facility is determined under Level 2 in the fair value hierarchy.



Investment securities, all classified as available-for-sale, consisted of the following as of December 31, 2016 and 2015:

Description	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Estimated Fair Value
December 31, 2016	(in thousands)
U.S. government agency-backed securities	$	25,906	$	7	$	(5	)	$	25,908
Corporate debt securities	42,040		41		(28		)	42,053
Municipal bonds	2,669		2		—			2,671
Total	$	70,615	$	50	$	(33	)	$	70,632

December 31, 2015
U.S. government agency-backed securities	$	22,417	$	1	$	(30	)	$	22,388
Corporate debt securities	51,807		1		(261		)	51,547
Municipal bonds	6,200		—		(11		)	6,189
Total	$	80,424	$	2	$	(302	)	$	80,124

During the year ended December 31, 2016, the Company realized approximately $6,700 of the unrealized loss at December 31, 2015. The Company's investment securities as of December 31, 2016, will reach maturity between January 2017 and January 2019, with a weighted-average maturity date in August 2017.

The Company has classified all of its available -for-sale investment securities, including those with maturities beyond one year, as current assets on the accompanying balance sheets based on the highly liquid nature of the investment securities and because these investment securities are considered available for use in current operations.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

+ References + Details

PROPERTY AND EQUIPMENT

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

PROPERTY AND EQUIPMENT



Property and equipment consists of the following:					December 31,
					2016			2015
	Estimated Useful Lives				(in thousands)
Leasehold improvements			5	years	$	12,131		$	4,092
Lab equipment			5	years	5,397			3,741
Office furniture			5	years	1,560			931
Manufacturing equipment			5	years	1,275			0
Computer and office equipment	3	to	5	years	623			401
Equipment held under capital leases			5	years	181			135
Software			3	years	85			109
Total					21,252			9,409
Less: accumulated depreciation					(4,748		)	(2,527		)
Property and equipment, net					$	16,504		$	6,882

During the years ended December 31, 2016, 2015, and 2014, the Company recorded $2.3 million, $1.2 million and $0.7 million of depreciation expense, respectively. Leasehold improvements at December 31, 2016 includes $2.5 million related to costs incurred by the landlord. Please refer to Note 12, “Commitments and contingencies,” for further information.

DEBT

12 Months Ended

Dec. 31, 2016

Debt Disclosure [Abstract]

DEBT

On March 10, 2016 (the Closing Date), the Company entered into a Loan and Security Agreement (the Loan Agreement) with Hercules Capital, Inc., Hercules Technology II, L.P., and Hercules Technology III, L.P., or collectively, Hercules, as a lender, under which the Company borrowed $15.0 million. The Company borrowed an additional $5.0 million and $10.0 million on September 15, 2016 and March 8, 2017, respectively. The total debt is secured by a lien covering substantially all of our assets, excluding intellectual property, but including proceeds from the sale, license, or disposition of our intellectual property. The Company intends to use the proceeds received under the Loan Agreement for funding the build-out of our manufacturing facilities and general corporate purposes. Please refer to Note 15, “Subsequent events” for further information.

The interest rate will be calculated at a rate equal to the greater of either (i) 9.35% plus the prime rate as reported in The Wall Street Journal minus 3.50%, or (ii) 9.35%. The interest rate on amounts borrowed under the Loan Agreement was 9.6% at December 31, 2016. Payments under the Loan Agreement are interest only for 18 months from the Closing Date, extendable to 24 months upon the Company achieving the Milestones. The interest only period will be followed by equal monthly payments of principal and interest amortized over a 30 months schedule through the maturity date of March 1, 2020 (the Loan Maturity Date); provided that if the Milestones are achieved, the Company will make equal monthly payments of principal and interest amortized over a 24 months schedule through the Loan Maturity Date. The remaining principal balance will be due and payable on the Loan Maturity Date. In addition, upon the Loan Maturity date or such earlier date specified in the Loan Agreement, a final payment equal to $1,390,000 (the Final Facility Charge), plus, an additional facility charge of $695,000, for an aggregate end-of-term charge of $2,085,000. The Company’s obligations under the Loan Agreement are secured by a security interest in substantially all of its assets, other than its intellectual property.

If the Company prepays the loan, including interest, prior to the date that is 24 months following March 10, 2016, it will pay Hercules a prepayment charge based on a prepayment fee equal to 2.00% of the amount prepaid; if the prepayment occurs thereafter, it will pay Hercules a prepayment charge based on a prepayment fee equal to 1.00% of the amount prepaid. The prepayment charge is also applicable upon the occurrence of a change of control of the Company. In addition to a prepayment charge, if any, the Company will pay Hercules the Final Facility Charge.

The Loan Agreement includes customary affirmative and restrictive covenants, but does not include any financial maintenance covenants, and also includes standard events of default, including payment defaults. Upon the occurrence of an event of default, a default interest rate of an additional 5% may be applied to the outstanding loan balance and Hercules may declare all outstanding obligations immediately due and payable and take such other actions as set forth in the Loan Agreement. The Company paid expenses related to the Loan Agreement of $199,000, which, along with the Final Facility Charge of $1,390,000, have been recorded as deferred financing costs, which offset long-term debt on the Company's balance sheet. Deferred financing costs of $1,589,000 are being amortized over the term of the loan, and are included in interest expenses. During the year ended December 31, 2016, interest expense included $422,000 of amortized deferred financing costs.



The total gross payments due under our debt arrangements are as follows:
	As of December 31, 2016
Year	(in thousands)
2017	$	1,787
2018	7,590
2019	8,363
2020	3,650
Total	$	21,390

COMMON STOCK, PREFERRED STOCK AND WARRANTS	12 Months Ended
COMMON STOCK, PREFERRED STOCK AND WARRANTS	Dec. 31, 2016
Equity [Abstract]
COMMON STOCK, PREFERRED STOCK AND WARRANTS	COMMON STOCK, PREFERRED STOCK AND WARRANTS Common Stock During the year ended December 31, 2014, the Company issued 8,452,500 shares of its common stock upon closing of its IPO for net proceeds of $146.3 million and 510,524 shares of its common stock for an aggregate of $249,701 in connection with the exercise of warrants. Exercise of Common Warrants During the year ended December 31, 2015, the Company issued 355,361 shares of its common stock to the Texas Treasury Safekeeping Trust Company (a transferee of the Office of the Governor - Economic Development and Tourism), pursuant to the cashless exercise provision of a warrant to purchase shares of the Company’s common stock issued to the State of Texas on September 27, 2007. The Company did not receive any cash or other consideration. Initial Public Offering On December 17, 2014, the Company commenced its initial public offering (IPO) pursuant to a registration statement on Form S-1 (File No. 333- 200328) that was declared effective by the SEC on December 17, 2014 and that registered an aggregate of 7,350,000 shares of the Company’s common stock for sale to the public at a price of $19.00 per share. In addition, at the closing of the IPO on December 23, 2014, the underwriters exercised their over-allotment option to purchase 1,102,500 additional shares of the Company’s common stock at a price to the public of $19.00 per share, for an aggregate offering price of $160.6 million. The net offering proceeds to the Company, after deducting underwriting discounts, commissions and offering costs, were approximately $146.3 million. Treasury Stock In December 2014, in connection with the restructuring of the license agreement with ARIAD Pharmaceuticals, Inc. (ARIAD), the Company repurchased from ARIAD 677,463 shares of its common stock valued at approximately $5.1 million. See Note 11 to the financial statements included herein. Preferred Stock Upon the closing of the IPO on December 17, 2014, all outstanding convertible preferred stock was converted into 16,230,777 shares of common stock on a one-to-one basis. No convertible preferred stock was outstanding as of December 31, 2016 and 2015.

- Definition

The entire disclosure for shareholders' equity comprised of portions attributable to the parent entity and noncontrolling interest, including other comprehensive income. Includes, but is not limited to, balances of common stock, preferred stock, additional paid-in capital, other capital and retained earnings, accumulated balance for each classification of other comprehensive income and amount of comprehensive income.

+ References

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Reference 8: http://www.xbrl.org/2003/role/presentationRef
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+ Details

SHARE-BASED COMPENSATION PLANS

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

SHARE-BASED COMPENSATION PLANS

The Company has four share-based compensation plans, which authorize the granting of shares of common stock and options to purchase common stock to employees and directors of the Company, as well as non-employee consultants, and allows the holder of the option to purchase common stock at a stated exercise price. Options vest according to the terms of the grant, which may be immediately or based on the passage of time, generally over four years, and have a term of up to 10 years. Unexercised stock options terminate on the expiration date of the grant. The Company recognizes the share-based compensation expense over the requisite service period of the individual grantees, which generally equals the vesting period.

2006 Stock Option Plan

The 2006 Stock Option Plan (the 2006 Plan) provided for the issuance of non-qualified stock options to employees, including officers, non-employee directors and consultants to the Company. A total of 146,210 and 151,410 options were outstanding under this plan as of December 31, 2016 and 2015. As of December 31, 2016, there were no additional shares available for grant under the 2006 Plan. During 2016 and 2015, a total of 5,200 and 15,646 options, respectively, were exercised for cash proceeds to the company of $2,652 and $6,980, respectively.

2011 Stock Option Plan

The 2011 Stock Option Plan (the 2011 Plan) provided for the issuance of incentive and non-qualified stock options to employees, including officers, non-employee directors and consultants to the Company. The 2011 Plan replaced the 2006 Plan. There were 2,051,413 and 2,256,120 outstanding options under this plan at December 31, 2016 and 2015, respectively. As of December 31, 2016, there were no additional shares available for grant under this plan. During 2016 and 2015, a total of 179,002 and 166,592 options, respectively, were exercised for cash proceeds to the company of $0.7 million and $0.5 million, respectively.

2014 Equity Incentive Plan

The 2014 Equity Incentive Plan (the 2014 Plan) became effective in December 2014, upon the closing of the IPO. The 2014 Plan provides for the issuance of equity awards, including incentive and non-qualified stock options and restricted stock awards to employees, including officers, non-employee directors and consultants to the Company or its affiliates. The 2014 Plan also provides for the grant of performance cash awards and performance-based stock awards. The aggregate number of shares of common stock that are authorized for issuance under the 2014 Plan is 2,990,354 shares, plus any shares subject to outstanding options that were granted under the 2011 Plan or 2006 Plan that are forfeited, terminated, expired or are otherwise not issued. There were 2,334,497 and 1,221,443 outstanding options under this plan at December 31, 2016 and 2015, respectively. During 2016, a total of 5,853 options were exercised for cash proceeds to the company of $0.1 million. No shares were exercised for cash proceeds in 2015. There were 58,825 and 88,236 shares of restricted stock outstanding under the Plan at December 31, 2016 and 2015, respectively. As of December 31, 2016, there were 560,911 shares remaining to be issued.

2014 Employee Stock Purchase Plan

The 2014 Employee Stock Purchase Plan (the ESPP) provides for eligible Company employees, as defined by the ESPP, to be given an opportunity to purchase the Company's common stock at a discount, through payroll deductions, with stock purchases being made upon defined purchase dates. The ESPP authorizes the issuance of up to 550,000 shares of the Company's common stock to participating employees, and allows eligible employees to purchase shares of common stock at a 15% discount from the grant date fair market value. As of December 31, 2016, there were 494,681 shares remaining to be issued.



A summary of activity within the ESPP follows:	Year Ended December 31,
	2016		2015
	(amounts in thousands)
Deductions from employees	$	375	$	381
Share-based compensation expense recognized	$	244	$	242
Remaining share-based compensation expense	$	406	$	267
Proceeds received by the Company for ESPP	$	369	$	347
Weighted-average purchase price per common share	$	10.97	$	16.01
Number of shares purchased by employees under ESPP	33,629		21,690

Share-Based Compensation Expense

The valuation of the share-based compensation awards is a significant accounting estimate that requires the use of judgment and assumptions that are likely to have a material impact on the financial statements. The fair value of option grants is determined using the Black-Scholes option-pricing model. Expected volatilities utilized in the model are based on implied volatilities from traded stocks of peer companies. Similarly, the dividend yield is based on historical experience and the estimate of future dividend yields. The risk-free interest rate is derived from the U.S. Treasury yield curve in effect at the time of grant. The expected term of the options is based on the average period the stock options are expected to remain outstanding. As the Company does not have sufficient historical information to develop reasonable expectations about future exercise patterns and post-vesting employment termination behavior, the expected term is calculated as the midpoint between the weighted-average vesting term and the contractual expiration period also known as the simplified method.

The fair value of the option grants have been estimated, with the following weighted-average assumptions:



	Year Ended December 31,
	2016		2015		2014
Risk-free interest rate	1.77	%	1.71	%	1.86	%
Volatility	72	%	74	%	95	%
Expected life (years)	6.08		6.08		6.09
Expected dividend yield	0	%	0	%	0	%

Share-based compensation for the years ended December 31, 2016, 2015 and 2014, are as follows:



	Year Ended December 31,
	2016		2015		2014
	(in thousands)
General and administrative	$	6,681	$	4,832	$	386
Research and development	$	5,656	3,577		525
Total	$	12,337	$	8,409	$	911

Stock option activity for the years ended December 31, 2016 and 2015 is as follows:



Options	Outstanding Stock Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	(in thousands) Aggregate Intrinsic Value
Balance at December 31, 2014	2,733,793	$	5.09	8.39	$	49,076
Granted	1,089,767	$	22.23
Exercised	(182,238)	$	2.64
Forfeited	(12,349)	$	14.99
Balance at December 31, 2015	3,628,973	$	10.32	8.03	$	39,021
Granted	1,159,957	$	17.43
Exercised	(190,055)	$	4.07		$	2,448
Forfeited	(66,755)	$	12.46
Balance at December 31, 2016	4,532,120	$	12.37	7.58	$	20,453
Exercisable as of December 31, 2016	2,302,155	$	8.22	6.59	$	17,095

Restricted stock share activity for the year ended December 31, 2016 and 2015 is as follows:



Restricted Stock Shares	Outstanding Restricted Shares		Weighted-Average Fair Value at Date of Grant Per Share
Balance at December 31, 2014	—
Granted	117,647		$	19.00
Vested	(29,411	)	$	19.00
Forfeited	—
Balance at December 31, 2015	88,236		$	19.00
Granted	—		—
Vested	(29,411)		$	19.00
Forfeited	—		—
Balance at December 31, 2016	58,825		$	19.00

The following table includes share-based payment activity for the years ended December 31, 2016, 2015 and 2014:



	Year Ended December 31,
	2016		2015		2014
	(in thousands, except per share)
Weighted-average grant date fair value of options granted	$	11.24	$	16.09	$	13.30
Weighted-average grant date fair value of restricted shares granted	$	—	$	—	$	19.00
Aggregate intrinsic value of options exercised	$	2,448	$	3,236	$	59
Total fair value of restricted shares vested	$	607	$	656	$	—
Cash received by Company upon option exercises	$	774	$	482	$	11

The following table summarizes the options outstanding and exercisable at December 31, 2016:



Options Outstanding					Options Exercisable
Exercise Price	Total Shares	Weighted- Average Remaining Contractual Term (in years)	Weighted-Average Exercise Price		Total Shares	Weighted- Average Remaining Contractual Term (in years)	Weighted-Average Exercise Price
$ .51 to $2.55	1,268,465	5.34	$	2.31	1,252,742	5.32	$	2.31
$ 7.47 to $19.85	2,337,638	8.54	$	13.46	616,076	8.02	$	9.60
$ 20.09 to $24.48	926,017	8.23	$	23.42	433,337	8.24	$	23.36
Total	4,532,120	7.58	Total		2,302,155	6.59

At December 31, 2016, total compensation cost not yet recognized was $27.4 million and the weighted average period over which this amount is expected to be recognized is 2.37 years. The aggregate fair value of options and restricted shares vesting in the years ended December 31, 2016, 2015 and 2014 was $12.2 million, $5.5 million and $0.3 million, respectively.

- Definition

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.

+ References + Details

GRANT REVENUE	12 Months Ended
GRANT REVENUE	Dec. 31, 2016
Deferred Revenue Disclosure [Abstract]
GRANT REVENUE	GRANT REVENUE CPRIT Grant On July 27, 2011, the Company entered into a Cancer Research Grant Contract (Grant Contract) with the Cancer Prevention and Research Institute of Texas (CPRIT) under which CPRIT awarded a grant not to exceed approximately $5.7 million to be used by the Company for the execution of defined clinical development of BPX-501. The Grant Contract terminated on June 30, 2014. The terms of the Grant Contract require the Company to pay tiered royalties on revenues from sales and licenses of intellectual property facilitated by the Grant Contract. During 2014, the Company incurred $1.4 million of expenses under the Grant Contract. There were no expenses under the Grant Contract in 2015 and 2016. On November 16, 2016, the Company received notice of a Product Development award totaling approximately $16.9 million from the Cancer Prevention and Research Institute of Texas, CPRIT. Assuming successful contract negotiations and execution, the CPRIT award would fund a portion of a three-year global clinical program comprising clinical trials for adult and pediatric patients with high-risk and intermediate-risk acute myeloid leukemia. The proposed studies are designed to evaluate the benefit of BPX-501 and rimiducid in the context of in vivo and ex vivo T cell depleted haploidentical hematopoietic stem cell transplantation. The CPRIT oversight committee met in February 2017 and agreed to move forward with the proposed terms of the grant agreement. The Company is currently in the process of completing a new contract with CPRIT and expects to begin a clinical development program supported by the CPRIT funding in the second half of 2017. NIH Grant During 2016, 2015 and 2014, the Company was awarded $0.3 million, $0.3 million and $0.3 million, respectively, under a grant from the National Institutes of Health (NIH). The awards cover the period from April 2013 through March 2017. The awards were made pursuant to the authority of 42 USC 241 42 CFR 52, and are subject to the requirements of the statute. Funds spent on the grant are reimbursed through monthly reimbursement requests. As of December 31, 2016, 2015 and 2014, funds spent under the grant were $0.4 million, $0.3 million and $0.3 million, respectively. As of December 31, 2016 and 2015, the Company had an outstanding grant receivable of $30,000 and $57,000, respectively for grant expenditures that were paid and not yet been reimbursed.

ARIAD RESTRUCTURING COSTS	12 Months Ended
ARIAD RESTRUCTURING COSTS	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
ARIAD RESTRUCTURING COSTS	ARIAD RESTRUCTURING COSTS On March 7, 2011, the Company entered into an amended and restated exclusive license agreement with ARIAD (Amended ARIAD License) which amended a license agreement entered into by the parties in 2006. Under the Amended ARIAD License, ARIAD granted to the Company an exclusive (even as to the ARIAD) license, with the right to grant sublicenses, under ARIAD’s patent rights relating to dimerizers, genetic constructs coding for dimerizer binding domains, vectors containing said constructs, cells containing said constructs and methods of inducing biological processes in cells containing said constructs. These licensed patent rights were initially limited to the fields of cell transplantation and certain types of cancer. In connection with the initial license, in 2006, the Company issued 121,241 shares of its common stock to ARIAD which were subject to antidilution protection that ultimately resulted in additional issuances to ARIAD by the Company of 556,222 shares of the Company’s common stock, such that ARIAD received a total of 677,463 shares of common stock under the license agreement. In addition, the Company paid ARIAD a license fee of $250,000 in connection with the amendment in 2011. The Amended ARIAD license also provided for certain royalty and milestone payments, which were subsequently terminated pursuant to an omnibus amendment agreement with ARIAD. Under the Amended ARIAD License, the Company is required to diligently proceed with the development, manufacture and sale of licensed products. The Amended ARIAD License is subject at all times to restrictions and obligations under a license agreement by and between ARIAD Gene Therapeutics, Inc. (one of ARIAD’s affiliates which merged into ARIAD) and the academic institution from which ARIAD obtained its license to the underlying technology. While the Company is not required to pay royalties or fees to such academic institution, no sublicensee of the Company’s may enter into a sublicense with respect to any intellectual property owned by the academic institution without its consent, which terms must be consistent with those included in the agreement between ARIAD and such academic institution. The Amended ARIAD License will expire upon expiration of the last license term of a licensed product covered by the agreement, which is either the later of (i) 12 years from the date of the first commercial sale of the licensed product, or (ii) expiration of a valid claim on the licensed product. Either party to the license may terminate or modify the Amended ARIAD License upon a material breach by the other party that remains uncured following the date that is 30 days after written notice of a payment breach and 90 days for any other breach, and effective immediately upon bankruptcy of the other party. The Company may terminate the amended ARIAD license in its sole discretion at any time if the Company determines not to develop or commercialize any licensed product. In addition, upon termination of the amended ARIAD license prior to expiration, the Company must transfer any ownership and any beneficial ownership in any orphan drug designation or any similar designation in any jurisdiction of orphan drug status of the ARIAD dimerizer to ARIAD. On October 3, 2014, the Company entered into an omnibus amendment agreement with ARIAD, under which the Company agreed to make payments of $50.0 million in exchange for an expansion of the license field, the termination of all obligations to make milestone and royalty payments to ARIAD in the future and the return of 677,463 shares of common stock held by ARIAD. In connection with the amendment, the Company made an initial payment of $15.0 million and issued a promissory note to ARIAD for a principal amount of $35.0 million. Per the promissory note terms, the principal would not accrue interest unless the Company was in default, in which case it would accrue at a rate of 10% per annum. In December 2014, following the Company’s IPO, the Company paid the remaining $35.0 million and ARIAD returned all 677,463 shares of common stock of the Company that ARIAD held. The license transaction was valued on the date of the transaction and the note was discounted to fair market value at a 10% rate. This resulted in the ARIAD license expense of $43.2 million, repurchase of common stock for $5.1 million and interest expense of $1.7 million. The Company has recorded the returned shares of common stock as treasury stock.

COMMITMENTS AND CONTINGENCIES

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

COMMITMENTS AND CONTINGENCIES

Operating Lease Agreements

The Company leases its office and manufacturing facilities under non-cancelable operating leases that expire January 31, 2020 and August 31, 2026, respectively. Rent expense for non-cancelable operating leases with scheduled rent increases is recognized on a straight-line basis over the terms of the leases. Improvement reimbursements from the landlord of $2.5 million are being amortized on a straight-line basis into rent expense over the terms of the leases. The difference between required lease payments and rent expense has been recorded as deferred rent. Rent expense was $1.8 million in 2016, $1.2 million in 2015, and $0.4 million in 2014. Deferred rent was $2.1 million as of December 31, 2016 and $ 1.1 million as of December 31, 2015.

Escrow agreement related to the operating lease dated May 2015

According to the escrow agreements in the operating leases, the Company agreed to deposit into escrow a total of approximately $9.6 million, which represents 110% of the Company’s remaining share of the estimated build-out costs. The funds were deposited into an escrow account in December 2016 and reported as restricted cash as of December 31, 2016.

Escrow agreement related to the First Amendment of the operating lease dated July 2016

The Company agreed to deposit into escrow a total of approximately $1.4 million, which represents 110% of the Company’s remaining share of the estimated build-out costs. The $1.4 million was deposited into an escrow account in January 2017.

Capital Lease Agreements - Equipment

The Company entered into multiple office equipment leases during both 2016 and 2015, which expire in 2021. The office equipment leases are being accounted for as capital leases under FASB Topic ASC 840 - Leases. The present value of the minimum lease payments are greater than 90% or more than the fair market value of the leased equipment and the lease terms are 6 years or the remaining term of the lease.

Aggregate future minimum annual payments under operating and capital leases at December 31, 2016, are as follows:



Year	Operating Leases		Capital Leases
	(in thousands)
2017	$	1,982	$	59
2018	2,033		59
2019	2,087		59
2020	1,124		59
2021	1,079		37
Thereafter	5,448		0
Total minimum rentals	$	13,753	$	273

Co-Development and Co-Commercialization Agreement - Adaptimmune Therapeutics plc

On December 16, 2016, the Company entered into a Co-Development and Co-Commercialization Agreement with and Adaptimmune Therapeutics plc (Adaptimmune) in order to facilitate a staged collaboration to evaluate, develop and commercialize next generation T cell therapies. Under the Agreement, the parties agreed to evaluate the Company’s GoTCR technology (inducible MyD88/CD40 co-stimulation, or iMC) with Adaptimmune’s affinity-optimized SPEAR® T cells for the potential to create enhanced TCR product candidates. Depending on results of the preclinical proof-of-concept phase, the parties expect to progress to a two-target co-development and co-commercialization phase. To the extent necessary, and in furtherance of the parties’ proof-of-concept and co-development efforts, the parties granted each other a royalty-free, non-transferable, non-exclusive license covering their respective technologies for purposes of facilitating such proof-of-concept and co-development efforts. In addition, as to covered therapies developed under the agreement, the parties granted each other a reciprocal exclusive license for the commercialization of such therapies. With respect to any joint commercialization of a covered therapy, the parties agreed to negotiate in good faith the commercially reasonable terms of a co-commercialization agreement. The parties also agreed that any such agreement shall provide for, among other things, equal sharing of the costs of any such joint commercialization and the calculation of profit shares as set forth in the Agreement. The Agreement will expire on a country-by-country basis once the parties cease commercialization of the T cell therapies covered by the Agreement, unless earlier terminated by either party for material breach, non-performance or cessation of development, bankruptcy/insolvency, or failure to progress to co-development phase. There were no expenses recognized under the Adaptimmune agreement for the year ended December 31, 2016.

Collaboration Agreement - OPBG

In October 2016, the Company entered into a collaboration agreement with and Ospedale Pediatrico Bambino Gesú (OPBG), pursuant to which the Company and OPBG agreed to collaborate on research projects and early stage clinical trials for the design and development of various T cell immunotherapies. As consideration for OPBG’s performance of the research under the agreement and grant of certain licenses to the Company, the Company agreed to fund an aggregate of up to $4.7 million in project costs payable to OPBG or certain third party service providers, as applicable, over the term of the research, estimated to be 4 years. With respect to any inventions arising from the research, OPBG agreed to grant the Company an exclusive license to any such inventions, the terms of which will be set forth in a separate agreement. In addition, OPBG granted the Company paid-up, worldwide co-exclusive licenses for non-commercial development of OPBG’s CD19 and GD2 CAR-T technologies, as well as paid-up, worldwide exclusive licenses to commercialize its CD19 and GD2 CAR-T technologies, each to be governed by a separate agreement. The expenses recognized under the OPBG Collaboration Agreement was $0.6 million for the year ended December 31, 2016.

Collaboration Agreement - Leiden

In May 2016, the Company and Academisch Ziekenhuis Leiden (Leiden) entered into a research collaboration agreement pursuant to which the Company will provide Leiden with financial support for research to discover and validate high-affinity TCR product candidates targeting several cancer-associated antigens. The Company agreed to pay Leiden an aggregate of EURO 2,547,415 in quarterly installments during the three-year term of the research, which will be recognized as services are incurred. During the year ended December 31, 2016, $0.1 million of research services were recognized. With respect to any inventions arising from the research that are relevant to or useful for any high affinity TCR that is studied in the research, Leiden granted the Company an exclusive option to obtain an exclusive, worldwide license to practice and exploit such inventions. The parties agreed to negotiate in good faith the commercially reasonable terms of each such license agreement entered into between the parties, based on terms similar to those set forth in the previously executed license agreement between the parties and those specified in the agreement. The expenses recognized under the Leiden license agreement were $0.9 million and $0.2 million for the years ended December 31, 2016 and 2015, respectively.

License Agreement - Baylor

In March 2016, the Company and Baylor College of Medicine (BCM) entered into two additional license agreements pursuant to

which the Company obtained exclusive rights to technologies and patent rights owned by BCM. The Company paid BCM a nonrefundable license fee of $0.1 million, and could incur additional payments upon the achievement of certain milestone events as set forth in the agreement. If the Company is successful in developing any of the licensed technologies, resulting sales would be

subject to a royalty payment in the low single digits. The expenses recognized under the Baylor License Agreement was $0.1 million for the year ended December 31, 2016.

License Agreement - Agensys, Inc.

On December 10, 2015, the Company and Agensys, Inc. (Agensys), entered into a license agreement (the Agreement), pursuant to which (i) Agensys granted the Company, within the field of cell and gene therapy of diseases in humans, an exclusive, worldwide license and sublicense to its patent rights directed to prostate stem cell antigen 1 (“PSCA”) and related antibodies, and (ii) the Company granted Agensys a non-exclusive, fully paid license to the Company’s patents directed to inventions that were made by the Company in the course of developing the Company’s licensed products, solely for use with Agensys therapeutic products containing a soluble antibody that binds to PSCA or, to the extent not based upon Bellicum’s other proprietary technology, to non-therapeutic applications of antibodies not used within the field. As consideration for the rights granted to the Company under the Agreement, the Company agreed to pay to Agensys a non-refundable upfront fee of $3,000,000, which is included in license fee expense. The Company is also required to make aggregate milestone payments to Agensys of up to (i) $5,000,000 upon the first achievement of certain specified clinical milestones for its licensed products, (ii) $50,000,000 upon the achievement of certain specified clinical milestones for each licensed product, and (iii) $75,000,000 upon the achievement of certain sales milestones for each licensed product. The Agreement additionally provides that the Company will pay to Agensys a royalty that ranges from the mid to high single digits based on the level of annual net sales of licensed products by the Company, its affiliates or permitted sublicensees. The royalty payments are subject to reduction under specified circumstances. These milestone and royalty payments will be expensed as incurred. Under the Agreement, Agensys also was granted the option to obtain an exclusive license, on a product-by-product basis, from the Company to commercialize in Japan each licensed product developed under the Agreement that has completed a phase 2 clinical trial. As to each such licensed product, if Agensys or its affiliate, Astellas Pharma, Inc., exercises the option, the Agreement provides that the Company will be paid an option exercise fee of $5,000,000. In addition, the Agreement provides that the Company will be paid a royalty that ranges from the mid to high single digits based on the level of annual net sales in Japan of each such licensed product. If the option is exercised, the aggregate milestone payments payable by the Company to Agensys, described above with respect to each licensed product, would be reduced by up to an aggregate of $65,000,000 upon the achievement of certain specified clinical and sales milestones. The Agreement will terminate upon the expiration of the last royalty term for the products covered by the Agreement, which is the earlier of (i) the date of expiration or abandonment of the last valid claim within the licensed patent rights covering any licensed products under the Agreement, (ii) the expiration of regulatory exclusivity as to a licensed product, and (iii) 10 years after the first commercial sale of a licensed product. Either party may terminate the Agreement upon a material breach by the other party that remains uncured following 60 days after the date of written notice of such breach (or 30 days if such material breach is related to failure to make payment of amounts due under the Agreement) or upon certain insolvency events. In addition, Agensys may terminate the Agreement immediately upon written notice to the Company if the Company or any of its affiliates or permitted sublicensees commences an interference proceeding or challenges the validity or enforceability of any of Agensys’ patent rights. There were no expenses recognized under the Agensys License Agreement for the year ended December 31, 2016. For the year ended December 31, 2015, $3.0 million of license expenses were recognized.

License Agreement - BioVec

On June 10, 2015, the Company and BioVec Pharma, Inc. (BioVec) entered into a license agreement (the BioVec Agreement) pursuant to which BioVec agreed to supply the Company with certain proprietary cell lines and granted to the Company a non-exclusive, worldwide license to certain of its patent rights and related know-how related to such proprietary cell lines. As consideration for the products supplied and rights granted to the Company under the BioVec Agreement, the Company agreed to pay to BioVec an upfront fee of $100,000 within ten business days of the effective date of the BioVec Agreement and a fee of $300,000 within ten business days of its receipt of the first release of GMP lot of the products licensed under the BioVec Agreement. In addition, the Company agreed to pay to BioVec an annual fee of $150,000, commencing 30 days following the first filing of an Investigational New Drug Application (an IND filing), or its foreign equivalent, for a product covered by the license; with such annual fees being creditable against any royalties payable by the Company to BioVec under the BioVec Agreement. The Company also is required to make a $250,000 milestone payment to BioVec for each of the first three licensed products to enter into a clinical phase trial and one-time milestone payments of $2,000,000 upon receipt of a registration granted by the Federal Drug Administration or European Medicines Agency on each of the Company’s first three licensed products. The BioVec Agreement additionally provides that the Company will pay to BioVec a royalty in the low single digits on net sales of products covered by the BioVec Agreement. The Company may also grant sublicenses under the licensed patent rights and know-how to third parties for limited purposes related to the use, sale and other exploitation of the products licensed under the BioVec Agreement. The BioVec Agreement will continue until terminated. The BioVec Agreement may be terminated by the Company, in its sole discretion, at any time upon 90 days written notice to BioVec. Either party may terminate the BioVec Agreement in the event of a breach by the other party of any material provision of the BioVec Agreement that remains uncured on the date that is 60 days after written notice of such failure or upon certain insolvency events that remain uncured following the date that is 30 days after the date of written notice to a party regarding such insolvency event. The Company recognized expenses of $0.1 million and $0.5 million, respectively, in connection with the BioVec License Agreement for the year ended December 31, 2015 and 2016, respectively.

License Agreement - Leiden

On April 23, 2015, the Company and Academisch Ziekenhuis Leiden, also acting under the name Leiden University Medical Centre (Leiden), entered into a license agreement (the Leiden Agreement), pursuant to which Leiden granted to the Company an exclusive, worldwide license to its patent rights covering high affinity T-cell receptors targeting preferentially-expressed antigen in melanoma, (PRAME) and POU2AF1 epitopes. The license granted under the Leiden Agreement is subject to certain restrictions and to Leiden’s retained right to use the licensed patents solely for academic research and teaching purposes, including research collaborations by Leiden with academic, non-profit research third parties; provided that Leiden provides 30 days advance written notice to the Company of such academic research collaborations. As consideration for the rights granted to the Company under the Leiden Agreement, the Company agreed to pay to Leiden an aggregate of EUR 75,000 in upfront fees within 30 days of the effective date of the Leiden Agreement. In addition, the Company agreed to pay to Leiden, beginning on the eighth anniversary of the effective date of the Leiden Agreement, annual minimum royalty payments of EUR 30,000. The Company also is required to make milestone payments to Leiden of up to an aggregate of EUR 1,025,000 for each of the first licensed product that is specific to PRAME and to POU2AF1. The Leiden Agreement additionally provides that the Company will pay to Leiden a royalty in the low single digits on net sales of products covered by the Leiden Agreement. If the Company enters into a sublicensing agreement with a third party related to a product covered by the Leiden Agreement, the Company agreed to pay Leiden a percentage ranging in the low double digits on all non-royalty income received from sublicensing revenue directly attributable to the sublicense, dependent on whether the Company is in phase 1/2, phase 2 or phase 3 at the time that the Company enters into any such sublicensing agreement. Under the Leiden Agreement, the Company and Leiden entered into a sponsored research agreement, pursuant to which the Company is required to pay Leiden up to EUR 300,000 over a three years period during the term of the sponsored research agreement. The Leiden Agreement will expire upon the expiration of the last patent included in the licensed patent rights. The Leiden Agreement may be terminated earlier upon mutual written agreement between the Company and Leiden, and at any time by the Company upon six months written notice to Leiden. Leiden may terminate the Leiden Agreement in the event of a failure by the Company to pay any amounts due under the Leiden Agreement that remains uncured on the date that is 30 days after written notice of such failure. Either party may terminate the Leiden Agreement upon a material breach by the other party that remains uncured following 30 days after the date of written notice of such breach or upon certain insolvency events that remain uncured following the date that is 45 days after the date of written notice to a party of such insolvency event. The Company recognized $84,000 of expenses in connection with the Leiden License Agreement for the year ended December 31, 2015. The Company was not required to make any milestone payments for the year ended December 31, 2015.

Employment agreements

The Company has signed agreements with thirteen of its officers and key employees to provide certain benefits in the event of a “change of control” as defined in these agreements and the occurrence of certain other events. The agreements provide for a lump-sum payment in cash equal to 6 to 18 months of annual base salary and annual cash bonus, if any. The annual base salary and annual cash bonus portion of the agreements would aggregate approximately $4.9 million at the rate of compensation in effect at December 31, 2016. In addition, the agreements provide for continuation of certain insurance and other benefits for periods of 6 to 18 months.

Litigation

The Company, from time to time, may be involved in litigation relating to claims arising out of its ordinary course of business. Management believes that there are no material claims or actions pending or threatened against the Company.

INCOME TAXES

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

INCOME TAXES

The Company did not recognize tax expense during 2016, 2015 or 2014.

The reconciliation between federal income taxes at the statutory rate and the Company’s income tax expense for the year is as follows:



	December 31,
	2016			2015			2014
	(in thousands)
U.S. tax benefit at statutory rate	$	(23,542	)	$	(16,506	)	$	(28,548	)
Meals and entertainment	22			24			10
Stock options	394			12			98
Warrant expense	—			—			8,286
Federal deferred tax true-up	32			(187		)	—
Return to provision	—			(2		)	—
Deferred tax valuation allowances	24,872			17,920			20,586
Research and development credit	(1,778		)	(1,261		)	(432		)
Income tax expense	$	—		$	—		$	—

Deferred income taxes reflect the net tax effect of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes, and the amounts used for income tax purposes. Significant components of the Company’s deferred taxes as of December 31, 2016 and 2015 are as follows:



	December 31,
	2016			2015
	(in thousands)
Deferred tax liabilities:
Unrealized gain on investment securities	$	(6	)	$	—
Depreciation	(4		)	(933		)
Total deferred tax liabilities	(10		)	(933		)

Deferred tax assets:
Net operating loss carryforward	48,152			28,229
Nonqualified stock options	5,126			2,248
Restricted stock expense	20			20
Employee stock purchase plan	—			82
Tenant improvement liability	645			341
Intangible assets	14,920			15,716
Unrealized loss on investment securities	—			103
Research and development credit	4,296			2,519
Other	67			23
Total deferred tax assets	73,226			49,281
Valuation allowance	(73,216		)	(48,348		)
Total deferred tax	$	—		$	—
Net current deferred tax liability	$	—		$	—
Net non-current deferred tax asset	—			—
Total deferred tax	$	—		$	—

As of December 31, 2016 and 2015, the Company had gross federal income tax net operating loss (NOL) carryforwards of $142.2 million and $83.0 million, respectively, and federal research tax credits of $4.3 million and $2.5 million, respectively. The NOL carryforwards will expire beginning in 2025, if not utilized. In assessing the realization of deferred tax assets, management considers whether it is more likely than not that some portion or all of the deferred tax asset will be realized. The ultimate realization of deferred tax assets is dependent upon the Company attaining future taxable income during periods in which those temporary differences become deductible.

Due to the uncertainty surrounding the realization of the benefits of its deferred assets, including NOL carryforwards, the Company has provided a 100% valuation allowance on its deferred tax assets at December 31, 2016 and 2015. The increases in the valuation allowance were $24.9 million and $18.0 million for the years ended December 31, 2016 and 2015, respectively.

The Internal Revenue Code Section 382 limits NOL and tax credit carry forwards when an ownership change of more than 50% of the value of the stock in a loss corporation occurs. Accordingly, the ability to utilize remaining NOL and tax credit carryforwards may be significantly restricted.

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED)

Selected quarterly financial data (unaudited) for the year ended December 31, 2016 and 2015 is presented below:



	(in thousands except per share data)
2016	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Total revenues	$	92		$	101		$	114		$	81
Loss from operations	$	(15,180	)	$	(16,259	)	$	(17,428	)	$	(19,513	)
Net loss	$	(15,075	)	$	(16,509	)	$	(17,719	)	$	(19,938	)
Net loss per share attributable to common shareholders - basic and diluted	$	(0.56	)	$	(0.61	)	$	(0.66	)	$	(0.74	)

2015	First Quarter			Second Quarter			Third Quarter			Fourth Quarter (1)
Total revenues	$	107		$	84		$	57		$	34
Loss from operations	$	(7,808	)	$	(10,705	)	$	(13,617	)	$	(17,005	)
Net loss	$	(7,758	)	$	(10,534	)	$	(13,408	)	$	(16,848	)
Net loss per share attributable to common shareholders - basic and diluted	$	(0.30	)	$	(0.40	)	$	(0.51	)	$	(0.63	)


(1)	The 2015 fourth quarter results include a non-refundable upfront fee to Agensys of $3.0 million under the license agreement. See Note 12 to the financial statements included herein.

SUBSEQUENT EVENTS	12 Months Ended
SUBSEQUENT EVENTS	Dec. 31, 2016
Subsequent Events [Abstract]
SUBSEQUENT EVENTS	SUBSEQUENT EVENTS Effective January 30, 2017, Thomas J. Farrell, resigned from his position as the President and Chief Executive Officer of the Company. In connection with Mr. Farrell’s resignation, effective January 30, 2017 the Board of Directors of the Company, appointed Richard A. Fair to serve as the Company’s President and Chief Executive Officer. On March 8, 2017, the Company borrowed an additional $10.0 million under its Loan Agreement with Hercules. The Company now has total outstanding principal under the Loan Agreement of approximately $30.0 million and an additional end of term commitment of $695,000 and a facility charge of $75,000. In addition, the interest only period was extended for another six months.

SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
SIGNIFICANT ACCOUNTING POLICIES (Policies)	Dec. 31, 2016
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America. Any reference in these footnotes to applicable guidance is meant to refer to the authoritative U.S. generally accepted accounting principles (GAAP) as found in the Accounting Standards Codification (ASC) and Accounting Standards Update (ASU) of the Financial Accounting Standards Board (FASB).
Use of Estimates	Use of Estimates The preparation of the financial statements in accordance with GAAP requires management to make certain estimates and judgments that affect the reported amounts of assets, liabilities, and expenses. Actual results could differ from those estimates.
Revenue Recognition	Revenue Recognition The Company has not yet generated any revenue from product sales. The Company’s sole source of revenue has been grant revenue related to a $5.7 million research grant received from the Cancer Prevention and Research Institute of Texas (CPRIT), covering a three-year period from July 1, 2011 through June 30, 2017, and a $1.3 million research grant from the National Institutes of Health (NIH) covering the period from April 2013 to March 2017. Grant payments received prior to the Company’s performance of work required by the terms of the research grant are recorded as deferred revenue and recognized as grant revenue once work is performed and qualifying costs are incurred. (See Note 10).
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all short-term, highly liquid investments with maturity of three months or less from the date of purchase to be cash equivalents.
Investment Securities	Investment Securities Consistent with its investment policy, the Company invests its cash allocated to fund its short-term liquidity requirements with prominent financial institutions in bank depository accounts and institutional money market funds. The Company invests the remainder of its cash in corporate debt securities and municipal bonds rated at least A quality or equivalent, U.S. Treasury notes and bonds and U.S. and state government agency-backed securities. The Company determines the appropriate classification of investment securities based on whether they represent the investment of funds available for current operations, as defined in ASC 210-10-45-1 and ASC 210-10-45-2. The Company reevaluates its classification as of each balance sheet date. All investment securities owned are classified as available-for-sale. The cost of securities sold is based on the specific identification method. Investment securities are recorded as of each balance sheet date at fair value, with unrealized gains and, to the extent deemed temporary, unrealized losses reported as accumulated other comprehensive gain (loss), a separate component of stockholders' equity. Interest and dividend income on investment securities, accretion of discounts and amortization of premiums and realized gains and losses are included in interest income in the statements of operations and comprehensive income (loss). An investment security is considered to be impaired when a decline in fair value below its cost basis is determined to be other than temporary. The Company evaluates whether a decline in fair value of an investment security is below its cost basis is other than temporary using available evidence. In the event that the cost basis of the investment security exceeds its fair value, the Company evaluates, among other factors, the amount and duration of the period that the fair value is less than the cost basis, the financial health of and business outlook for the issuer, including industry and sector performance, and operational and financing cash flow factors, overall market conditions and trends, the Company’s intent to sell the investment security and whether it is more likely than not the Company would be required to sell the investment security before its anticipated recovery. If a decline in fair value is determined to be other than temporary, the Company records an impairment charge in the statement of operations and comprehensive loss and establishes a new cost basis in the investment.
Property and Equipment	Property and Equipment Leasehold improvements, furniture, equipment and software are recorded at cost and are depreciated using the straight-line method over the estimated useful lives of the related assets, which range from three to five years. Leasehold improvements are amortized over the shorter of the estimated useful life or the remaining lease term.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews long-lived assets for impairment when events or changes in business conditions indicate that their carrying value may not be recoverable. Recoverability of assets to be held and used is measured by a comparison of the carrying amount of an asset to the estimated undiscounted future cash flows expected to be generated by the asset. If the carrying amount of an asset exceeds its estimated future cash flows, an impairment charge is recognized in the amount by which the carrying amount of the asset exceeds the fair value of the asset. There were no impairment charges related to long-lived assets for the years ended December 31, 2016, 2015 and 2014.
Debt Issuance Costs	Debt Issuance Costs Costs related to debt issuance are presented in the balance sheet as a direct deduction from the carrying amount of the debt liability, consistent with debt discounts and are amortized using the effective interest method. Amortization of debt issuance costs are included in interest expense
Deferred Rent and Rent	Deferred Rent and Rent The Company recognizes rent expense for leases with increasing annual rents on a straight-line basis over the term of the lease. The amount of rent expense in excess of cash payments is classified as deferred rent. Any lease incentives received are deferred and amortized over the term of the lease.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Accounting standards include disclosure requirements around fair values used for certain financial instruments and establish a fair value hierarchy. The three-tier hierarchy prioritizes valuation inputs into three levels based on the extent to which inputs used in measuring fair value are observable in the market, as described further in Note 4. The Company believes the recorded values of its financial instruments, including cash and cash equivalents, accounts payable and accrued liabilities approximate their fair values due to the short-term nature of these instruments.
Financial Instruments and Credit Risks	Financial Instruments and Credit Risks Financial instruments that potentially subject the Company to credit risk include cash and cash equivalents, investment securities, and accounts receivable. Cash is deposited in demand accounts in federally insured domestic institutions to minimize risk. Insurance is provided through the Federal Deposit Insurance Corporation (FDIC) and Security Investor Protection Corporation (SIPC). Although the balances in these accounts exceed the federally insured limit from time to time, the Company has not incurred losses related to these deposits.
Equity Issuance Costs	Equity Issuance Costs Equity issuance costs represent costs paid to third parties in order to obtain equity financing. These costs have been netted against the proceeds of the equity issuances.
Licenses and Patents	Licenses and Patents Licenses and patent costs for technologies that are utilized in research and development and have no alternative future use are expensed as incurred. Costs related to the license of patents from third parties and internally developed patents are classified as research and development expenses. Legal costs related to patent applications and maintenance are classified as general and administrative expenses.
Clinical Trials	Clinical Trials The Company estimates its clinical trial expense accrual for a given period based on the number of patients enrolled at each site, estimated cost per patient, and the length of time each patient has been in the trial, less amounts previously billed. These accruals are recorded in accrued expenses and other current liabilities, and the related expense is recorded in research and development expense.
Research and Development	Research and Development Research and development expenses consist of expenses incurred in performing research and development activities, including compensation and benefits for research and development employees and consultants, facilities expenses, overhead expenses, cost of laboratory supplies, manufacturing expenses, fees paid to third parties and other outside expenses. Research and development costs are expensed as incurred. Clinical trial and other development costs incurred by third parties are expensed as the contracted work is performed. The Company accrues for costs incurred as the services are being provided by monitoring the status of the clinical trial or project and the invoices received from its external service providers. The Company estimates depend on the timeliness and accuracy of the data provided by the vendors regarding the status of each project and total project spending. The Company adjusts its accrual as actual costs become known. Where contingent milestone payments are due to third parties under research and development arrangements, the milestone payment obligations are expensed when the milestone events are achieved.
Collaboration Agreements	Collaboration Agreements The Company enters into collaboration agreements that include varying arrangements regarding which parties perform and bear the costs of research and development activities. The Company may share the costs of research and development activities with a collaborator, or the Company may be reimbursed for all or a significant portion of the costs of the Company's research and development activities. The Company records its internal and third-party development costs associated with these collaborations as research and development expenses. When the Company is entitled to reimbursement of all or a portion of the research and development expenses that it incurs under a collaboration, the Company records those reimbursable amounts as a deduction to the research and development expenses. If the collaboration is a cost-sharing arrangement in which both the Company and its collaborator perform development work and share costs, the Company also recognizes, as research and development expenses in the period when its collaborator incurs development expenses, the portion of the collaborator's development expenses that the Company is obligated to reimburse.
Reclassifications	Reclassifications Certain research and development indirect costs, including facilities and overhead, were previously included in general and administrative costs. These research and development indirect costs are included in research and development expense for the year ended December 31, 2016 and 2015. The results for the year ended December 31, 2014 have been reclassified to conform to the current year presentation. The effect of the reclassification of the results for the year ended December 31, 2014 was to increase research and development expense and reduce general and administrative expense by $1.1 million with no change in total operating expense or net loss.
Contract Manufacturing Services	Contract Manufacturing Services Contract manufacturing services are expensed as incurred. Prepaid expenses are capitalized and amortized as services are performed.
Share-Based Compensation	Share-Based Compensation The Company accounts for its share-based compensation in accordance with ASC 718, Compensation — Stock Compensation, which requires the measurement and recognition of compensation expense for all share-based payment awards made to employees and directors to be recognized in the financial statements, based on their fair value. The Company measures share-based compensation to consultants in accordance with ASC 505-50, Equity-Based Payments to Non-Employees, and recognizes the fair value of the award over the period the services are rendered. The Company uses the Black-Scholes option-pricing model to estimate the fair value of stock option awards. The fair value is recognized as expense, net of estimated forfeitures, over the requisite service period, which is generally the vesting period of the respective award on a straight-line basis. Prior to the Company’s IPO on December 23, 2014, the determination of the grant date fair value of options using the Black-Scholes option-pricing model was affected by the Company’s estimated common stock fair value, as well as assumptions regarding a number of other complex and subjective variables.
Income Taxes	Income Taxes Income taxes are accounted for under the asset and liability method. Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. This method also requires the recognition of future tax benefits such as net operating loss and tax credit carry forwards, to the extent that realization of such benefits is more likely than not. A valuation allowance is recorded when the realization of future tax benefits is uncertain. The Company records a valuation allowance for the full amount of deferred tax assets, which would otherwise be recorded for tax benefits relating to the operating loss and tax credit carryforwards, as realization of such deferred tax assets cannot be determined to be more likely than not. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply 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 the statement of operations in the period that includes the enactment date. The Company accounts for uncertain tax positions in accordance with the provisions of ASC 740, Income Taxes. When uncertain tax positions exist, the Company recognizes the tax benefit of tax positions to the extent that the benefit will more likely than not be realized. The determination as to whether the tax benefit will more likely than not be realized is based upon the technical merits of the tax position as well as consideration of the available facts and circumstances. As of December 31, 2016, 2015 and 2014, the Company had no uncertain tax positions and no interest or penalties have been charged to the Company for the years ended December 31, 2016, 2015 and 2014. If incurred, the Company will classify any interest and penalties as a component of interest expense and operating expense, respectively. The Company is subject to routine audits by taxing jurisdictions; however, there are currently no audits for any tax periods in progress. The tax years 2005 through 2016 remain open to examination by the Internal Revenue Service.
Comprehensive Loss	Comprehensive Loss Comprehensive income (loss) is defined as the change in equity of a business enterprise during a period, from transactions, and other events and circumstances from non-owner sources. Components of comprehensive income (loss) includes, among other items, unrealized gains and losses on the changes in fair value of investments. These components are added, net of their related tax effect, to the reported net income (loss) to arrive at comprehensive income (loss). The components of accumulated other comprehensive loss at December 31, 2016 and 2015, on the Company’s balance sheet was comprised of the net unrealized holding losses on the Company’s investment securities. See Note 4 for further detail of the unrealized holding gains and losses on the Company’s investment securities.
Net Loss and Net Loss per Share of Common Stock Attributable to Common Stockholders	Net Loss and Net Loss per Share of Common Stock Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of share of common stock outstanding during the period without consideration for common stock equivalents. Diluted net loss per share of common stock is the same as basic net loss per share of common stock, since the effects of potentially dilutive securities are antidilutive. The net loss per share of common stock attributable to common stockholders is computed using the two-class method required for participating securities. All series of the Company’s convertible preferred stock are considered to be participating securities as they are entitled to participate in undistributed earnings with shares of common stock. Due to the Company’s net loss, there is no impact on the earnings per share calculation in applying the two-class method since the participating securities have no legal requirement to share in any losses. The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per shares of common stock attributable to common stockholders for the periods presented as the effect of including such securities would be anti-dilutive. Net Loss and Net Loss per Share of Common Stock Attributable to Common Stockholders Basic net loss per share attributable to common stockholders is calculated by dividing the net loss attributable to common stockholders by the weighted-average number of share of common stock outstanding during the period without consideration for common stock equivalents. Diluted net loss per share of common stock is the same as basic net loss per share of common stock, since the effects of potentially dilutive securities are antidilutive. The net loss per share of common stock attributable to common stockholders is computed using the two-class method required for participating securities. All series of the Company’s convertible preferred stock are considered to be participating securities as they are entitled to participate in undistributed earnings with shares of common stock. Due to the Company’s net loss, there is no impact on the earnings per share calculation in applying the two-class method since the participating securities have no legal requirement to share in any losses. The following outstanding shares of common stock equivalents were excluded from the computations of diluted net loss per shares of common stock attributable to common stockholders for the periods presented as the effect of including such securities would be anti-dilutive.
Recently Issued Accounting Pronouncements	Application of New Accounting Standards ASU No. 2014-15, “Disclosures of Uncertainties about an Entity’s Ability to Continue as a Going Concern,” became effective for the Company in 2016. ASU No. 2014-15 requires management to evaluate the Company’s ability to meet its obligations as they become due within one year after the date that financial statements are issued. Accordingly, management has assessed the Company’s ability to continue as a going concern through March 31, 2018. In making its assessment, management evaluated the Company’s liquid assets, the Company’s obligations expected to become payable within the period, and the probability of other conditions and events, and concluded that the Company’s ability to continue as a going concern is not in substantial doubt. ASU No. 2016-18, “Statement of Cash Flows (Topic 230): Restricted Cash,” requires restricted cash to be included with cash and cash equivalents when reconciling the beginning and ending amounts on the statement of cash flows, and requires additional disclosures in the notes to the financial statements. The Company adopted this standard during 2016. See Note 3 to the financial statements included herein. ASU No. 2015-03, “Simplifying the Presentation of Debt Issuance Costs,” requires that debt issuance costs related to a recognized debt liability be presented in the balance sheet as a direct deduction from the carrying amount of that debt liability, consistent with debt discounts. See Note 7 to the financial statements included herein. ASU No. 2015-17, "Balance Sheet Classification of Deferred Taxes," requires that deferred income tax liabilities and assets be classified as noncurrent in a classified statement of financial position. The Company adopted this standard as of December 31, 2015, prospectively. See Note 13 to the financial statements included herein. New Accounting Requirements and Disclosures In January 2016, the FASB issued ASU No. 2016-01, “Recognition and Measurement of Financial Assets and Financial Liabilities.” ASU 2016-01 requires that most equity investments be measured at fair value, with subsequent changes in fair value recognized in net income. The pronouncement also impacts financial liabilities under the fair value option and the presentation and disclosure requirements for financial instruments. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2017, and early adoption is not permitted. The Company does not believe that the adoption of this pronouncement will have a material impact on the Company’s financial statements. In February 2016, the FASB issued ASU No. 2016-02, “Leases,” which requires companies that lease assets to recognize a right-of-use asset and a lease liability, initially measured at the present value of the lease payments, in its balance sheet. The pronouncement will also require additional disclosures about the amount, timing and uncertainty of cash flows arising from leases. This pronouncement is effective for fiscal years, and interim periods within those years, beginning after December 15, 2018, and early adoption is permitted. The Company is currently evaluating the impact of this pronouncement on the Company's financial statements. In March 2016, the FASB issued ASU No. 2016-09, “Compensation-Stock Compensation,” which simplifies accounting for share-based compensation arrangements, primarily as it relates to accounting for the income tax effects of share-based compensation. Under the pronouncement, an entity can make an entity-wide accounting policy decision to either estimate the number of awards that are expected to vest (current GAAP) or account for forfeitures as they occur. The pronouncement is effective for annual periods beginning after December 31, 2016, with earlier adoption permitted. The Company does not believe the adoption of this standard will have a material impact on the Company's financial statements. In August 2016, the FASB issued ASU 2016-15, “Classification of Certain Cash Receipts and Cash Payments,” which provides guidance on the classification of certain cash receipts and payments in the statement of cash flows. The pronouncement is effective for annual periods beginning after December 15, 2017, and interim periods within those annual periods. Earlier application is permitted in any interim or annual period. The Company does not believe the adoption of this standard will have a material impact on the Company's financial statements.

SIGNIFICANT ACCOUNTING POLICIES (Tables)

12 Months Ended

Dec. 31, 2016

Accounting Policies [Abstract]

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share



	Number of shares
	December 31, 2016	December 31, 2015	December 31, 2014
Options to purchase common stock	4,532,120	3,628,973	2,733,793
Unvested shares of restricted stock	58,825	88,236	117,647
Total common stock equivalents	4,590,945	3,717,209	2,851,440

CASH AND CASH EQUIVALENTS AND RESTRICTED CASH (Tables)

12 Months Ended

Dec. 31, 2016

Cash and Cash Equivalents [Abstract]

Schedule of Cash, Cash Equivalents & Restricted Cash



	December 31, 2016		December 31, 2015
	(in thousands)
Cash and cash equivalents (1)	$	33,140	$	70,241
Restricted cash, noncurrent	9,640		—
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$	42,780	$	70,241

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES (Tables)

12 Months Ended

Dec. 31, 2016

Fair Value Disclosures [Abstract]

Fair Value, Assets Measured on Recurring Basis



			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2016		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)
Cash Equivalents:
Money market funds	23,459		23,459		—		—
U.S. government agency-backed securities	—		—		—		—
Total Cash Equivalents	$	23,459	$	23,459	$	—	$	—

Investment Securities:
U.S. government agency-backed securities	$	25,908	$	—	$	25,908	$	—
Corporate debt securities	42,053		—		42,053		—
Municipal bonds	2,671		—		2,671		—
Total Investment Securities	$	70,632	$	—	$	70,632	$	—

			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2015		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
	(in thousands)
Cash Equivalents:
Money market funds	$	52,714	$	52,714	$	—	$	—
U.S. government agency-backed securities	9,500		—		9,500		—
Total Cash Equivalents	$	62,214	$	52,714	$	9,500	$	—

Investment Securities:
U.S. government agency-backed securities	$	22,388	$	—	$	22,388	$	—
Corporate debt securities	51,547		—		51,547		—
Municipal bonds	6,189		—		6,189		—
Total Investment Securities	$	80,124	$	—	$	80,124	$	—

Available-for-sale Securities



Investment securities, all classified as available-for-sale, consisted of the following as of December 31, 2016 and 2015:

Description	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Estimated Fair Value
December 31, 2016	(in thousands)
U.S. government agency-backed securities	$	25,906	$	7	$	(5	)	$	25,908
Corporate debt securities	42,040		41		(28		)	42,053
Municipal bonds	2,669		2		—			2,671
Total	$	70,615	$	50	$	(33	)	$	70,632

December 31, 2015
U.S. government agency-backed securities	$	22,417	$	1	$	(30	)	$	22,388
Corporate debt securities	51,807		1		(261		)	51,547
Municipal bonds	6,200		—		(11		)	6,189
Total	$	80,424	$	2	$	(302	)	$	80,124

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

+ References + Details

PROPERTY AND EQUIPMENT (Tables)

12 Months Ended

Dec. 31, 2016

Property, Plant and Equipment [Abstract]

Property and Equipment



Property and equipment consists of the following:					December 31,
					2016			2015
	Estimated Useful Lives				(in thousands)
Leasehold improvements			5	years	$	12,131		$	4,092
Lab equipment			5	years	5,397			3,741
Office furniture			5	years	1,560			931
Manufacturing equipment			5	years	1,275			0
Computer and office equipment	3	to	5	years	623			401
Equipment held under capital leases			5	years	181			135
Software			3	years	85			109
Total					21,252			9,409
Less: accumulated depreciation					(4,748		)	(2,527		)
Property and equipment, net					$	16,504		$	6,882

SHARE-BASED COMPENSATION PLANS (Tables)

12 Months Ended

Dec. 31, 2016

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Employee Stock Purchase Plan, Activity



A summary of activity within the ESPP follows:	Year Ended December 31,
	2016		2015
	(amounts in thousands)
Deductions from employees	$	375	$	381
Share-based compensation expense recognized	$	244	$	242
Remaining share-based compensation expense	$	406	$	267
Proceeds received by the Company for ESPP	$	369	$	347
Weighted-average purchase price per common share	$	10.97	$	16.01
Number of shares purchased by employees under ESPP	33,629		21,690

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The fair value of the option grants have been estimated, with the following weighted-average assumptions:



	Year Ended December 31,
	2016		2015		2014
Risk-free interest rate	1.77	%	1.71	%	1.86	%
Volatility	72	%	74	%	95	%
Expected life (years)	6.08		6.08		6.09
Expected dividend yield	0	%	0	%	0	%

Schedule of Compensation Cost for Share-based Payment Arrangements, Allocation of Share-based Compensation Costs by Plan

Share-based compensation for the years ended December 31, 2016, 2015 and 2014, are as follows:



	Year Ended December 31,
	2016		2015		2014
	(in thousands)
General and administrative	$	6,681	$	4,832	$	386
Research and development	$	5,656	3,577		525
Total	$	12,337	$	8,409	$	911

Schedule of Share-based Compensation, Stock Options, Activity

Stock option activity for the years ended December 31, 2016 and 2015 is as follows:



Options	Outstanding Stock Options	Weighted-Average Exercise Price		Weighted-Average Remaining Contractual Term (in years)	(in thousands) Aggregate Intrinsic Value
Balance at December 31, 2014	2,733,793	$	5.09	8.39	$	49,076
Granted	1,089,767	$	22.23
Exercised	(182,238)	$	2.64
Forfeited	(12,349)	$	14.99
Balance at December 31, 2015	3,628,973	$	10.32	8.03	$	39,021
Granted	1,159,957	$	17.43
Exercised	(190,055)	$	4.07		$	2,448
Forfeited	(66,755)	$	12.46
Balance at December 31, 2016	4,532,120	$	12.37	7.58	$	20,453
Exercisable as of December 31, 2016	2,302,155	$	8.22	6.59	$	17,095

Schedule of Nonvested Restricted Stock Units Activity

Restricted stock share activity for the year ended December 31, 2016 and 2015 is as follows:



Restricted Stock Shares	Outstanding Restricted Shares		Weighted-Average Fair Value at Date of Grant Per Share
Balance at December 31, 2014	—
Granted	117,647		$	19.00
Vested	(29,411	)	$	19.00
Forfeited	—
Balance at December 31, 2015	88,236		$	19.00
Granted	—		—
Vested	(29,411)		$	19.00
Forfeited	—		—
Balance at December 31, 2016	58,825		$	19.00

Disclosure of Share-based Compensation Arrangements by Share-based Payment Award

The following table includes share-based payment activity for the years ended December 31, 2016, 2015 and 2014:



	Year Ended December 31,
	2016		2015		2014
	(in thousands, except per share)
Weighted-average grant date fair value of options granted	$	11.24	$	16.09	$	13.30
Weighted-average grant date fair value of restricted shares granted	$	—	$	—	$	19.00
Aggregate intrinsic value of options exercised	$	2,448	$	3,236	$	59
Total fair value of restricted shares vested	$	607	$	656	$	—
Cash received by Company upon option exercises	$	774	$	482	$	11

Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range

The following table summarizes the options outstanding and exercisable at December 31, 2016:



Options Outstanding					Options Exercisable
Exercise Price	Total Shares	Weighted- Average Remaining Contractual Term (in years)	Weighted-Average Exercise Price		Total Shares	Weighted- Average Remaining Contractual Term (in years)	Weighted-Average Exercise Price
$ .51 to $2.55	1,268,465	5.34	$	2.31	1,252,742	5.32	$	2.31
$ 7.47 to $19.85	2,337,638	8.54	$	13.46	616,076	8.02	$	9.60
$ 20.09 to $24.48	926,017	8.23	$	23.42	433,337	8.24	$	23.36
Total	4,532,120	7.58	Total		2,302,155	6.59

COMMITMENTS AND CONTINGENCIES (Tables)

12 Months Ended

Dec. 31, 2016

Commitments and Contingencies Disclosure [Abstract]

Schedule of Future Minimum Lease Payments for Capital Leases

Aggregate future minimum annual payments under operating and capital leases at December 31, 2016, are as follows:



Year	Operating Leases		Capital Leases
	(in thousands)
2017	$	1,982	$	59
2018	2,033		59
2019	2,087		59
2020	1,124		59
2021	1,079		37
Thereafter	5,448		0
Total minimum rentals	$	13,753	$	273

Schedule of Future Minimum Rental Payments for Operating Leases

Aggregate future minimum annual payments under operating and capital leases at December 31, 2016, are as follows:



Year	Operating Leases		Capital Leases
	(in thousands)
2017	$	1,982	$	59
2018	2,033		59
2019	2,087		59
2020	1,124		59
2021	1,079		37
Thereafter	5,448		0
Total minimum rentals	$	13,753	$	273

INCOME TAXES (Tables)

12 Months Ended

Dec. 31, 2016

Income Tax Disclosure [Abstract]

Schedule of Effective Income Tax Rate Reconciliation [Table Text Block]

The reconciliation between federal income taxes at the statutory rate and the Company’s income tax expense for the year is as follows:



	December 31,
	2016			2015			2014
	(in thousands)
U.S. tax benefit at statutory rate	$	(23,542	)	$	(16,506	)	$	(28,548	)
Meals and entertainment	22			24			10
Stock options	394			12			98
Warrant expense	—			—			8,286
Federal deferred tax true-up	32			(187		)	—
Return to provision	—			(2		)	—
Deferred tax valuation allowances	24,872			17,920			20,586
Research and development credit	(1,778		)	(1,261		)	(432		)
Income tax expense	$	—		$	—		$	—

Schedule of Deferred Tax Assets and Liabilities [Table Text Block]



	December 31,
	2016			2015
	(in thousands)
Deferred tax liabilities:
Unrealized gain on investment securities	$	(6	)	$	—
Depreciation	(4		)	(933		)
Total deferred tax liabilities	(10		)	(933		)

Deferred tax assets:
Net operating loss carryforward	48,152			28,229
Nonqualified stock options	5,126			2,248
Restricted stock expense	20			20
Employee stock purchase plan	—			82
Tenant improvement liability	645			341
Intangible assets	14,920			15,716
Unrealized loss on investment securities	—			103
Research and development credit	4,296			2,519
Other	67			23
Total deferred tax assets	73,226			49,281
Valuation allowance	(73,216		)	(48,348		)
Total deferred tax	$	—		$	—
Net current deferred tax liability	$	—		$	—
Net non-current deferred tax asset	—			—
Total deferred tax	$	—		$	—

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (Tables)

12 Months Ended

Dec. 31, 2016

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

Selected quarterly financial data (unaudited) for the year ended December 31, 2016 and 2015 is presented below:



	(in thousands except per share data)
2016	First Quarter			Second Quarter			Third Quarter			Fourth Quarter
Total revenues	$	92		$	101		$	114		$	81
Loss from operations	$	(15,180	)	$	(16,259	)	$	(17,428	)	$	(19,513	)
Net loss	$	(15,075	)	$	(16,509	)	$	(17,719	)	$	(19,938	)
Net loss per share attributable to common shareholders - basic and diluted	$	(0.56	)	$	(0.61	)	$	(0.66	)	$	(0.74	)

2015	First Quarter			Second Quarter			Third Quarter			Fourth Quarter (1)
Total revenues	$	107		$	84		$	57		$	34
Loss from operations	$	(7,808	)	$	(10,705	)	$	(13,617	)	$	(17,005	)
Net loss	$	(7,758	)	$	(10,534	)	$	(13,408	)	$	(16,848	)
Net loss per share attributable to common shareholders - basic and diluted	$	(0.30	)	$	(0.40	)	$	(0.51	)	$	(0.63	)


(1)	The 2015 fourth quarter results include a non-refundable upfront fee to Agensys of $3.0 million under the license agreement. See Note 12 to the financial statements included herein.

SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended			48 Months Ended	72 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 31, 2017	Jun. 30, 2017
Property, Plant and Equipment [Line Items]
Revenue from grants	$ 388	$ 282	$ 1,780
Reclassification from general and administrative to research and development expense			$ 1,100
Minimum
Property, Plant and Equipment [Line Items]
Estimated useful lives	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated useful lives	5 years
Forecast
Property, Plant and Equipment [Line Items]
Revenue from grants				$ 1,300	$ 5,700
Revenue from grants, period					3 years

SIGNIFICANT ACCOUNTING POLICIES - Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share (Details) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,590,945	3,717,209	2,851,440
Equity Option
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	4,532,120	3,628,973	2,733,793
Restricted Stock
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from computation of earnings per share (in shares)	58,825	88,236	117,647

CASH AND CASH EQUIVALENTS AND RESTRICTED CASH (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Restricted cash	$ 10.0
Cash equivalent instruments	$ 23.5	$ 62.2

CASH AND CASH EQUIVALENTS AND RESTRICTED CASH - Schedule of Cash, Cash Equivalents & Restricted Cash (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 33,140	$ 70,241
Restricted cash, noncurrent	9,640	0
Total cash, cash equivalents and restricted cash shown in the statements of cash flows	$ 42,780	$ 70,241

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Available-for-sale Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	$ 70,615	$ 80,424
Available-for-sale Securities, Gross Unrealized Gains	50	2
Available-for-sale Securities, Gross Unrealized Losses	(33)	(302)
Available-for-sale Securities	70,632	80,124
US Treasury and Government
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	25,906	22,417
Available-for-sale Securities, Gross Unrealized Gains	7	1
Available-for-sale Securities, Gross Unrealized Losses	(5)	(30)
Available-for-sale Securities	25,908	22,388
Corporate Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	42,040	51,807
Available-for-sale Securities, Gross Unrealized Gains	41	1
Available-for-sale Securities, Gross Unrealized Losses	(28)	(261)
Available-for-sale Securities	42,053	51,547
Municipal Bonds
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	2,669	6,200
Available-for-sale Securities, Gross Unrealized Gains	2	0
Available-for-sale Securities, Gross Unrealized Losses	0	(11)
Available-for-sale Securities	$ 2,671	$ 6,189

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, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 21,252	$ 9,409
Less: accumulated depreciation	(4,748)	(2,527)
Property and equipment, net	16,504	6,882
Depreciation expense	2,306	1,199	$ 667
Leasehold improvements	$ 2,500
Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	3 years
Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Leasehold improvements
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Property, plant and equipment, gross	$ 12,131	4,092
Lab equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Property, plant and equipment, gross	$ 5,397	3,741
Office furniture
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Property, plant and equipment, gross	$ 1,560	931
Manufacturing equipment
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Property, plant and equipment, gross	$ 1,275	0
Computer and office equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 623	401
Computer and office equipment \| Minimum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	3 years
Computer and office equipment \| Maximum
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Equipment held under capital leases
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	5 years
Property, plant and equipment, gross	$ 181	135
Software
Property, Plant and Equipment [Line Items]
Estimated Useful Lives	3 years
Property, plant and equipment, gross	$ 85	$ 109

ACCRUED EXPENSES AND OTHER CURRENT LIABILITIES (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Payables and Accruals [Abstract]
Accrued construction costs	$ 3,120	$ 0
Accrued manufacturing costs	1,704	2,412
Accrued payroll	1,568	1,332
Accrued patient treatment costs	1,006	333
Accrued other	1,965	1,003
Total accrued expenses and other current liabilities	$ 9,363	$ 5,080

DEBT (Details) - USD ($)		12 Months Ended
DEBT (Details) - USD ($)	Mar. 10, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Mar. 08, 2017	Sep. 15, 2016
Debt Instrument [Line Items]
Long-term debt	$ 15,000,000	$ 18,436,000	$ 0
Debt Instrument, Additional Borrowing, Second Draw						$ 5,000,000
Fixed interest	9.35%	10.00%
Interest only payments, period	18 months
Interest only payments, extended period, if milestones are achieved	24 months
Principal and interest payment period	30 months
Principal and interest payment period, if milestones are achieved	24 months
Final payment at maturity date	$ 1,390,000
Final payment at maturity date, additional amount subject to and contingent on funding of additional $10.0 million	695,000
Debt Instrument, Aggregate Payment Amount on Final Facility Charge	$ 2,085,000
Period threshold for prepayment penalty percentage evaluation	24 months
Early repayment fee, percentage of prepaid amount, period one	2.00%
Early repayment fee, percentage of prepaid amount, period two	1.00%
Default interest rate		5.00%
Payment of debt issuance costs		$ 199,000	$ 0	$ 0
Final facility charge		1,390,000
Deferred financing costs		1,589,000
Amortization of debt issuance costs		$ 422,000
Prime Rate
Debt Instrument [Line Items]
Basis spread on variable rate	(3.50%)
Subsequent Event
Debt Instrument [Line Items]
Long-term debt					$ 30,000,000.0
Debt Instrument, Additional Borrowing, Third Draw					$ 10,000,000

DEBT Schedule of Debt Maturities (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Debt Disclosure [Abstract]
2017	$ 1,787
2018	7,590
2019	8,363
2020	3,650
Total	$ 21,390

COMMON STOCK, PREFERRED STOCK AND WARRANTS - Narrative (Details)				1 Months Ended	12 Months Ended
	Dec. 23, 2014 USD ($) $ / shares	Dec. 23, 2014 $ / shares shares	Dec. 17, 2014 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Dec. 31, 2014 USD ($) shares
Class of Stock [Line Items]
Shares issued in connection with exercise of warrants \| shares				510,524		355,361	510,524
Proceeds from exercise of common warrants \| $					$ 0	$ 0	$ 249,701
Issuance of common stock in an IPO, net of issuance costs \| $							146,303,000
Repurchase of common stock held by ARIAD \| $							$ 5,056,000
Conversion ratio			1
Convertible preferred stock, outstanding \| shares					0	0
IPO
Class of Stock [Line Items]
Issuance of common stock in an IPO, net of issuance costs (in shares) \| shares			7,350,000		8,452,500
Net offering proceeds \| $			$ 146,300,000		$ 146,300,000
Issuance of common stock, price (in usd per share) \| $ / shares			$ 19.00
Issuance of common stock in an IPO, net of issuance costs \| $	$ 160,600,000
Over-Allotment Option
Class of Stock [Line Items]
Issuance of common stock in an IPO, net of issuance costs (in shares) \| shares		1,102,500
Issuance of common stock, price (in usd per share) \| $ / shares	$ 19.00	$ 19.00
Common Stock
Class of Stock [Line Items]
Issuance of common stock in an IPO, net of issuance costs (in shares) \| shares							8,452,500
Issuance of common stock in an IPO, net of issuance costs \| $							$ 85,000
Conversion of preferred stock (in shares) \| shares			16,230,777				16,230,777
Common Stock \| ARIAD Pharmaceuticals, Inc.
Class of Stock [Line Items]
Repurchase of common stock held by ARIAD (in shares) \| shares				677,463
Repurchase of common stock held by ARIAD \| $				$ 5,100,000

SHARE-BASED COMPENSATION PLANS Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Goods and Nonemployee Services Transaction [Line Items]
Options outstanding (in shares)	4,532,120	3,628,973	2,733,793
Exercise of stock options (in shares)	190,055	182,238
Cash received by Company upon option exercises	$ 774,000	$ 482,000	$ 11,000
Proceeds from exercise of stock options	773,000	482,000	0
Total compensation cost not yet recognized	$ 27,400,000
Compensation cost not yet recognized, period for recognition	2 years 4 months 13 days
Aggregate fair value of fair value of options vesting	$ 12,200,000	$ 5,500,000	$ 300,000
2006 Stock Option Plan
Share-based Goods and Nonemployee Services Transaction [Line Items]
Options outstanding (in shares)	146,210	151,410
Number of shares available for grant	0
Exercise of stock options (in shares)	5,200	15,646
Cash received by Company upon option exercises	$ 2,652	$ 6,980
2011 Stock Option Plan
Share-based Goods and Nonemployee Services Transaction [Line Items]
Options outstanding (in shares)	2,051,413	2,256,120
Number of shares available for grant	0
Exercise of stock options (in shares)	179,002	166,592
Proceeds from exercise of stock options	$ 700,000	$ 474,447
2014 Stock Option Plan
Share-based Goods and Nonemployee Services Transaction [Line Items]
Options outstanding (in shares)	2,334,497	1,221,443
Exercise of stock options (in shares)	5,853
Proceeds from exercise of stock options	$ 100,000
Aggregate number of shares authorized for issuance	2,990,354
Restricted shares outstanding (in shares)	58,825	88,236
Shares remaining to be issued	560,911
2014 Employee Stock Purchase Plan
Share-based Goods and Nonemployee Services Transaction [Line Items]
Number of shares available for grant			550,000
Shares remaining to be issued	494,681
Employee Stock Option
Share-based Goods and Nonemployee Services Transaction [Line Items]
Award vesting period	4 years
Award expiration period (up to)	10 years

SHARE-BASED COMPENSATION PLANS Summary of Activity within ESPP (Details) - 2014 Employee Stock Purchase Plan - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Deductions from employees	$ 375	$ 381
Share-based compensation expense recognized	244	242
Remaining share-based compensation expense	406	267
Proceeds received by the Company for ESPP	$ 369	$ 347
Weighted-average purchase price per common share	$ 10.97	$ 16.01
Number of shares purchased by employees under ESPP	33,629	21,690

SHARE-BASED COMPENSATION PLANS Option Weighted Average Assumptions (Details) - Employee Stock Option	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Risk-free interest rate	1.77%	1.71%	1.86%
Volatility	72.00%	74.00%	95.00%
Expected life (years)	6 years 29 days	6 years 29 days	6 years 1 month 2 days
Expected dividend yield	0.00%	0.00%	0.00%

SHARE-BASED COMPENSATION PLANS Share-Based Compensation Expense (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	$ 12,337	$ 8,409	$ 911
General and administrative
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	6,681	4,832	386
Research and development
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Share-based compensation	$ 5,656	$ 3,577	$ 525

SHARE-BASED COMPENSATION PLANS Stock Options Rollforward (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Outstanding Stock Options
Beginning Balance (in shares)	3,628,973	2,733,793
Granted (in shares)	1,159,957	1,089,767
Exercised (in shares)	(190,055)	(182,238)
Forfeited (in shares)	(66,755)	(12,349)
Ending Balance (in shares)	4,532,120	3,628,973	2,733,793
Exercisable as of December 31, 2016 (in shares)	2,302,155
Weighted-Average Exercise Price
Weighted-Average Exercise Price Outstanding (usd per share)	$ 10.32	$ 5.09
Granted (usd per share)	17.43	22.23
Exercised (usd per share)	4.07	2.64
Forfeited (usd per share)	12.46	14.99
Weighted-Average Exercise Price Outstanding (usd per share)	$ 12.37	10.32	$ 5.09
Exercisable as of December 31, 2016 (usd per share)		$ 8.22
Outstanding Stock Options, Other Disclosures
Weighted- Average Remaining Contractual Term (in years)	7 years 6 months 29 days	8 years 11 days	8 years 4 months 21 days
Weighted Average Remaining Contractual Term Exercisable	6 years 215 days
Aggregate Intrinsic Value Outstanding	$ 20,453	$ 39,021	$ 49,076
Aggregate intrinsic value of options exercised	$ 2,448	3,236	$ 59
Aggregate Intrinsic Value Exercisable		$ 17,095

SHARE-BASED COMPENSATION PLANS Restricted Stock Shares Roll Forward (Details) - Restricted Stock - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Outstanding Restricted Shares
Beginning Balance (in shares)	88,236	0
Granted (in shares)	0	117,647
Vested (in shares)	(29,411)	(29,411)
Forfeited (in shares)	0	0
Ending Balance (in shares)	58,825	88,236
Weighted-Average Fair Value at Date of Grant Per Share Granted (in usd per share)	$ 19.00	$ 19.00
Weighted-Average Fair Value at Date of Grant Per Share Nonvested (in usd per share)	$ 19.00	$ 19.00

SHARE-BASED COMPENSATION PLANS Share-Based Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of options granted (in usd per share)	$ 11.24	$ 16.09	$ 13.30
Aggregate intrinsic value of options exercised	$ 2,448	$ 3,236	$ 59
Cash received by Company upon option exercises	$ 774	$ 482	$ 11
Restricted Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average grant date fair value of restricted shares granted (in usd per share)	$ 0.00	$ 0.00	$ 19.00
Total fair value of restricted shares vested	$ 607	$ 656	$ 0

SHARE-BASED COMPENSATION PLANS Stock Options Outstanding And Exercisable (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding (in shares)	4,532,120
Weighted- Average Remaining Contractual Term (in years)	7 years 6 months 29 days	8 years 11 days	8 years 4 months 21 days
Options Exercisable (in shares)	2,302,155
Weighted- Average Remaining Contractual Term (in years)	6 years 7 months 2 days
.51 to $2.55
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding (in shares)	1,268,465
Weighted- Average Remaining Contractual Term (in years)	5 years 4 months 2 days
Weighted-Average Exercise Price (in usd per share)	$ 2.31
Options Exercisable (in shares)	1,252,742
Weighted- Average Remaining Contractual Term (in years)	5 years 3 months 26 days
Weighted-Average Exercise Price (in usd per share)	$ 2.31
$7.47 to $19.85
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding (in shares)	2,337,638
Weighted- Average Remaining Contractual Term (in years)	8 years 6 months 15 days
Weighted-Average Exercise Price (in usd per share)	$ 13.46
Options Exercisable (in shares)	616,076
Weighted- Average Remaining Contractual Term (in years)	8 years 7 days
Weighted-Average Exercise Price (in usd per share)	$ 9.60
$20.09 to 24.48
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options Outstanding (in shares)	926,017
Weighted- Average Remaining Contractual Term (in years)	8 years 2 months 23 days
Weighted-Average Exercise Price (in usd per share)	$ 23.42
Options Exercisable (in shares)	433,337
Weighted- Average Remaining Contractual Term (in years)	8 years 2 months 27 days
Weighted-Average Exercise Price (in usd per share)	$ 23.36
Minimum \| .51 to $2.55
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Exercise Price (in usd per share)		$ 0.51
Minimum \| $7.47 to $19.85
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Exercise Price (in usd per share)		7.47
Minimum \| $20.09 to 24.48
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Exercise Price (in usd per share)		20.09
Maximum \| .51 to $2.55
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Exercise Price (in usd per share)		2.55
Maximum \| $7.47 to $19.85
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Exercise Price (in usd per share)		19.85
Maximum \| $20.09 to 24.48
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-Average Exercise Price (in usd per share)		$ 24.48

GRANT REVENUE (Details) - USD ($) $ in Thousands			12 Months Ended
GRANT REVENUE (Details) - USD ($) $ in Thousands	Nov. 16, 2016	Jul. 27, 2011	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Grants			$ 388	$ 282	$ 1,780
Cancer Prevention and Research Institute of Texas
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Grants		$ 5,700		1,400
Grant award to be received	$ 16,900
Length of global clinical program (in years)	3 years
National Institutes of Health Grant
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Grants			300	300	300
Funds spent under the grant			400	300	$ 300
Grants receivable			$ 30	$ 57

ARIAD RESTRUCTURING COSTS (Details) - USD ($)			1 Months Ended	12 Months Ended
ARIAD RESTRUCTURING COSTS (Details) - USD ($)	Oct. 03, 2014	Mar. 07, 2011	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2006
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
License fees				$ 580,000	$ 3,184,000	$ 0
Debt paid			$ 35,000,000	0	0	1,187,000
Repurchase of common stock held by ARIAD						5,056,000
Interest expense				$ 1,760,000	$ 12,000	$ 1,791,000
ARIAD License Agreement
Collaborative Arrangements and Non-collaborative Arrangement Transactions [Line Items]
Shares issued subject to antidilution protection							121,241
Additional shares issued due to antidilution protection							556,222
Total number of shares issued under the license agreement							677,463
License fees	$ 43,200,000	$ 250,000
Term of license		12 years
Termination period after written notice of failure		30 days
Termination notice period for any other breach		90 days
Payment arrangement in exchange for an expansion of the license field	$ 50,000,000.0
Repurchase of common stock held by ARIAD (in shares)	677,463
Initial payment in connection with the amendment	$ 15,000,000
Promissory note, principal amount	$ 35,000,000
Interest rate in the event of default, percentage	10.00%
Fair value adjustment, percent	10.00%
Repurchase of common stock held by ARIAD	$ 5,100,000
Interest expense	$ 1,700,000

COMMITMENTS AND CONTINGENCIES - Lease Agreements, Narrative (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Jan. 31, 2017
Property Subject to or Available for Operating Lease [Line Items]
Landlord reimbursements	$ 2.5
Rent expense	1.8	$ 1.2	$ 0.4
Deferred rent	2.1	$ 1.1
Present value of minimum lease payments, percentage of fair market value of leased equipment (greater than)		90.00%
Capital lease, term		6 years
Operating Lease Dated May 2015
Property Subject to or Available for Operating Lease [Line Items]
Escrow deposit	$ 9.6
Estimated build-out costs (as a percent)	110.00%
Operating Lease Dated July 2016
Property Subject to or Available for Operating Lease [Line Items]
Escrow deposit	$ 1.4
Estimated build-out costs (as a percent)	110.00%
Subsequent Event \| Operating Lease Dated July 2016
Property Subject to or Available for Operating Lease [Line Items]
Escrow deposit				$ 1.4

COMMITMENTS AND CONTINGENCIES - Aggregate Future Minimum Annual Payments Under Operating and Capital Leases (Details) $ in Thousands	Dec. 31, 2016 USD ($)
Operating Leases
2017	$ 1,982
2018	2,033
2019	2,087
2020	1,124
2021	1,079
Thereafter	5,448
Total minimum rentals	13,753
Capital Leases
2017	59
2018	59
2019	59
2020	59
2021	37
Thereafter	0
Total minimum rentals	$ 273

COMMITMENTS AND CONTINGENCIES - Collaboration Agreement (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 EUR (€)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Long-term Purchase Commitment [Line Items]
Research and development expense	$ 51,263		$ 33,561	$ 12,071
OPBG \| Research and Development Arrangement
Long-term Purchase Commitment [Line Items]
Long-term purchase commitment, value (up to)	$ 4,700
Research term	4 years	4 years
OPBG \| Collaborative Arrangement
Long-term Purchase Commitment [Line Items]
License agreement expense	$ 600
Leiden
Long-term Purchase Commitment [Line Items]
Research and development expense	100
Leiden \| Collaborative Arrangement
Long-term Purchase Commitment [Line Items]
License agreement expense	$ 900		$ 200
Payments to acquire intangible assets \| €		€ 2,547,415

COMMITMENTS AND CONTINGENCIES - License Agreements (Details)				6 Months Ended	12 Months Ended
	Dec. 10, 2015 USD ($)	Jun. 10, 2015 USD ($) product	Apr. 23, 2015 EUR (€)	Jun. 30, 2015	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Long-term Purchase Commitment [Line Items]
Upfront fee					$ 0	$ 0	$ 43,212,000
Baylor \| Licensing Agreements
Long-term Purchase Commitment [Line Items]
Payments to acquire intangible assets					100,000
License agreement expense						100,000.0
Agensys \| Licensing Agreements
Long-term Purchase Commitment [Line Items]
Upfront fee	$ 3,000,000
Milestone payments upon first achievement of certain specified clinical milestones for licensed products	5,000,000
Milestone payments upon achievement of certain specified clinical milestones for each licensed product	50,000,000
Milestone payments for the achievement of sales milestones for each licensed product	75,000,000
Exclusive license, option exercise fee	5,000,000
Maximum reduction in aggregate milestone payments if exclusive license option is exercised	$ 65,000,000
Termination period, number of years after first commercial sale of licensed product	10 years
Termination period, notice of failure on uncured items	60 days
Period of notice of failure on uncured items, if material breach is related to failure to make payments	30 days
License agreement expense						3,000,000.0
BioVec \| Licensing Agreements
Long-term Purchase Commitment [Line Items]
Upfront fee		$ 100,000
Milestone payments upon first achievement of certain specified clinical milestones for licensed products		$ 250,000
Termination period, notice of failure on uncured items		60 days
Upfront fee payment period, number of days from effective date		10 days
License costs due upon first release of product		$ 300,000
License costs due upon first release of product, period of payment		10 days
License agreement, annual fee		$ 150,000
License agreement, annual fee period, from first IND filing				30 days
Milestone payments, number of initial products \| product		3
Milestone payments upon registration with FDA		$ 2,000,000
Termination notice period for any other breach		90 days
Termination period, after insolvency event		30 days
License agreement expense					$ 450,000	100,000
Leiden \| Licensing Agreements
Long-term Purchase Commitment [Line Items]
Upfront fee \| €			€ 75,000
Milestone payments upon first achievement of certain specified clinical milestones for licensed products \| €			€ 1,025,000
Termination period, notice of failure on uncured items			30 days
Upfront fee payment period, number of days from effective date			30 days
Termination notice period for any other breach			6 months
Termination period, after insolvency event			45 days
License agreement expense						$ 84,000
Advance notice of research collaborations, period			30 days
Annual minimum royalty payments (in EUR) \| €			€ 30,000
Leiden agreement, sponsored research \| €			€ 300,000
Period of payments under sponsored research Agreement			3 years
Termination period after written notice of failure			30 days

COMMITMENTS AND CONTINGENCIES - Employment Agreement (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) employe
Other Commitments [Line Items]
Postemployment agreement, number of officers and key employees \| employe	13
Estimated annual base salary and cash bonus compensation in the event of a change in control \| $	$ 4.9
Minimum
Other Commitments [Line Items]
Postemployment benefits, estimated liability, period	6 months
Continuation of certain insurance and other benefits, period	6 months
Maximum
Other Commitments [Line Items]
Postemployment benefits, estimated liability, period	18 months
Continuation of certain insurance and other benefits, period	18 months

INCOME TAXES - Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
U.S. tax benefit at statutory rate	$ (23,542)	$ (16,506)	$ (28,548)
Meals and entertainment	22	24	10
Stock options	394	12	98
Warrant expense	0	0	8,286
Federal deferred tax true-up	32	(187)	0
Return to provision	0	(2)	0
Deferred tax valuation allowances	24,872	17,920	20,586
Research and development credit	(1,778)	(1,261)	(432)
Income tax expense	$ 0	$ 0	$ 0

INCOME TAXES - Components of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax liabilities:
Unrealized gain on investment securities	$ (6)	$ 0
Depreciation	(4)	(933)
Total deferred tax liabilities	(10)	(933)
Deferred tax assets:
Net operating loss carryforward	48,152	28,229
Nonqualified stock options	5,126	2,248
Restricted stock expense	20	20
Employee stock purchase plan	0	82
Tenant improvement liability	645	341
Intangible assets	14,920	15,716
Unrealized loss on investment securities	0	103
Research and development credit	4,296	2,519
Other	67	23
Total deferred tax assets	73,226	49,281
Valuation allowance	(73,216)	(48,348)
Total deferred tax	0	0
Net current deferred tax liability	0	0
Net non-current deferred tax asset	$ 0	$ 0

INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
INCOME TAXES - Narrative (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Research tax credits	$ 4,296	$ 2,519
Net operating loss carry forwards, expiration year	2025
Increases in valuation allowance	$ 24,900	18,000
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Net operating loss carry forwards	142,200	83,000
Research tax credits	$ 4,300	$ 2,500

SELECTED QUARTERLY FINANCIAL DATA (UNAUDITED) (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]
Total revenues	$ 81	$ 114	$ 101	$ 92	$ 34	$ 57	$ 84	$ 107	$ 388	$ 282	$ 1,780
Loss from operations	(19,513)	(17,428)	(16,259)	(15,180)	(17,005)	(13,617)	(10,705)	(7,808)	(68,380)	(49,135)	(57,838)
Net loss	$ (19,938)	$ (17,719)	$ (16,509)	$ (15,075)	$ (16,848)	$ (13,408)	$ (10,534)	$ (7,758)	$ (69,241)	$ (48,548)	$ (83,965)
Net loss per share attributable to common shareholders - basic and diluted	$ (0.74)	$ (0.66)	$ (0.61)	$ (0.56)	$ (0.63)	$ (0.51)	$ (0.40)	$ (0.30)	$ (2.57)	$ (1.84)	$ (34.04)
License agreement upfront fee					$ 3,000

SUBSEQUENT EVENTS - Narrative (Details) - USD ($)	Mar. 08, 2017	Dec. 31, 2016	Mar. 10, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Long-term debt		$ 18,436,000	$ 15,000,000	$ 0
Subsequent Event
Subsequent Event [Line Items]
Additional borrowing capacity	$ 10,000,000
Long-term debt	30,000,000.0
End of term commitment fee	695,000
Facility charge	$ 75,000
Debt Instrument, Payment Terms, Interest Only Payments, Extension Period	6 months

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Assets Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	$ 70,632	$ 80,124
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	23,459	62,214
Available-for-sale Securities	70,632	80,124
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	23,459	52,714
Available-for-sale Securities	0	0
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	9,500
Available-for-sale Securities	70,632	80,124
Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	0
Available-for-sale Securities	0	0
US Treasury and Government
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	25,908	22,388
US Treasury and Government \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	25,908	22,388
US Treasury and Government \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
US Treasury and Government \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	25,908	22,388
US Treasury and Government \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Corporate Debt Securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	42,053	51,547
Corporate Debt Securities \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	42,053	51,547
Corporate Debt Securities \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Corporate Debt Securities \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	42,053	51,547
Corporate Debt Securities \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Municipal Bonds
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	2,671	6,189
Municipal Bonds \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	2,671	6,189
Municipal Bonds \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Municipal Bonds \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	2,671	6,189
Municipal Bonds \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available-for-sale Securities	0	0
Money Market Funds \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	23,459	52,714
Money Market Funds \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	23,459	52,714
Money Market Funds \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	0
Money Market Funds \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	0
US Government Corporations and Agencies Securities \| Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	9,500
US Government Corporations and Agencies Securities \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	0
US Government Corporations and Agencies Securities \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	0	9,500
US Government Corporations and Agencies Securities \| Fair Value, Measurements, Recurring \| Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash and cash equivalents, fair value disclosure	$ 0	$ 0

FAIR VALUE OF MEASUREMENTS AND INVESTMENT SECURITIES - Narrative (Details)	12 Months Ended
	Dec. 31, 2016 USD ($)
Fair Value Disclosures [Abstract]
Available-for-sale Securities, gross realized loss	$ 6,700