Document and Entity Information Document	6 Months Ended
Document and Entity Information Document	Jun. 30, 2015	Jul. 31, 2015
Entity Information [Line Items]
Entity Registrant Name	Bellicum Pharmaceuticals, Inc.
Entity Central Index Key	0001358403
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Document Type	10-Q
Document Period End Date	Jun. 30, 2015
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q2
Amendment Flag	false
Entity Common Stock, Shares Outstanding		26,493,493

Balance Sheets (USD $)	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 101,646,000	$ 191,602,000
Investment securities, available for sale - short-term	17,649,000	0
Accounts receivable, interest and other receivables	462,000	298,000
Prepaid expenses and other current assets	2,182,000	1,322,000
Total current assets	121,939,000	193,222,000
Investment securities, available for sale - long-term	53,270,000	0
Property and equipment, net of accumulated depreciation	4,798,000	2,427,000
Other assets	230,000	145,000
TOTAL ASSETS	180,237,000	195,794,000
Current liabilities:
Accounts payable	814,000	1,209,000
Accrued expenses	1,754,000	2,163,000
Deferred revenue	0	13,000
Current portion of deferred rent	30,000	97,000
Current portion of deferred manufacturing costs	376,000	154,000
Total current liabilities	2,974,000	3,636,000
Long-term liabilities:
Deferred rent	254,000	209,000
Deferred manufacturing costs	0	313,000
Total long-term liabilities	254,000	522,000
TOTAL LIABILITIES	3,228,000	4,158,000
Commitments and Contingencies
Stockholders’ equity:
Common stock, $0.01 par value; 200,000,000 shares authorized at June 30, 2015 and December 31, 2014, respectively; 27,098,200 shares issued and 26,420,737 shares issued and outstanding at June 30, 2015; 27,050,055 issued and 26,372,592 issued and outstanding at December 31, 2014	271,000	271,000
Treasury stock: 677,463 shares held at June 30, 2015 and December 31, 2014	(5,056,000)	(5,056,000)
Additional paid-in capital	313,234,000	309,365,000
Accumulated other comprehensive loss	(204,000)	0
Accumulated deficit	(131,236,000)	(112,944,000)
Total stockholders’ equity	177,009,000	191,636,000
Total liabilities and stockholders’ equity	$ 180,237,000	$ 195,794,000

Balance Sheets Balance Sheet Parenthetical (USD $)	Jun. 30, 2015	Dec. 31, 2014
Statement of Financial Position [Abstract]
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, authorized (shares)	200,000,000	200,000,000
Common stock, issued (shares)	27,098,200	26,420,737
Common stock, outstanding (shares)	27,050,055	26,372,592
Treasury Stock, shares (shares)	677,463	677,463

Statements of Operations (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants	$ 84	$ 554	$ 191	$ 1,106
Total revenues	84	554	191	1,106
Operating Expenses [Abstract]
Research and development (includes share-based compensation of $962 and $72 for the three months ended June 30, 2015 and 2014, respectively and $1,561 and $138 for the six months ended June 30, 2015 and 2014, respectively)	8,012	3,235	13,730	5,624
General and administrative (includes share-based compensation of $1,186 and $9 for the three months ended June 30, 2015 and 2014, respectively and $2,075 and $19 for the six months ended June 30, 2015 and 2014, respectively)	2,777	592	4,974	1,032
OPERATING EXPENSES	10,789	3,827	18,704	6,656
Loss from operations	(10,705)	(3,273)	(18,513)	(5,550)
OTHER INCOME (EXPENSE):
Interest income	171	3	221	6
Interest expense	0	(11)	0	(27)
Total other income (expense)	171	(8)	221	(21)
NET LOSS	(10,534)	(3,281)	(18,292)	(5,571)
Preferred stock dividends	0	(564)	0	(1,104)
Net loss attributable to common shareholders, basic and diluted	(10,534)	(3,845)	(18,292)	(6,675)
Net loss per common share attributable to common shareholders, basic and diluted (usd per share)	$ (0.40)	$ (1.81)	$ (0.70)	$ (3.35)
Weighted-average shares outstanding, basic and diluted (shares)	26,268,610	2,119,518	26,264,025	1,992,142
Unrealized loss on investment securities	(204)	0	(204)	0
Comprehensive loss	(10,738)	(3,281)	(18,496)	(5,571)
General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	1,186	9	2,075	19
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost	$ 962	$ 72	$ 1,561	$ 138

Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Net Cash Provided by (Used in) Operating Activities [Abstract]
Net loss	$ (18,292)	$ (5,571)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation expense	375	321
Share-based compensation	3,636	157
Amortization of lease liability	(22)	(48)
Amortization of premium on investment securities, net	169	0
Changes in operating assets and liabilities:
Accounts receivable	(164)	(1,018)
Prepaid expenses and other assets	(945)	294
Accounts payable	(395)	(12)
Accrued liabilities	(409)	(624)
Deferred costs	(104)	291
NET CASH USED IN OPERATING ACTIVITIES	(16,151)	(6,210)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of investment securities	(73,619)	0
Proceeds from sale of investment securities	2,327	0
Purchases of property and equipment	(2,746)	(122)
CASH USED IN INVESTING ACTIVITIES	(74,038)	(122)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of common stock	241	0
Proceeds from issuance of Series B preferred stock	0	7,320
Payment of issuance costs of common stock	(8)	0
Proceeds from exercise of common warrants	0	201
Payments on line of credit	0	(200)
NET CASH PROVIDED BY FINANCING ACTIVITIES	233	7,321
NET CHANGE IN CASH AND CASH EQUIVALENTS	(89,956)	989
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD	191,602	11,168
CASH AND CASH EQUIVALENTS AT END OF PERIOD	101,646	12,157
Noncash Investing and Financing Items [Abstract]
Dividends accrued on preferred stock (usd per share)	$ 0	$ 1,104

Organization and Business Description	6 Months Ended
Organization and Business Description	Jun. 30, 2015
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 and dendritic cell vaccines. The Company has not generated any revenue from product sales to date and does not anticipate generating revenues from product sales in the foreseeable future. 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

6 Months Ended

Jun. 30, 2015

Accounting Policies [Abstract]

Significant Accounting Policies

SIGNIFICANT ACCOUNTING POLICIES

Basis of Presentation

The accompanying interim financial statements are unaudited. These unaudited interim financial statements have been prepared in accordance with U.S. generally accepted accounting principles (GAAP) and following the requirements of the U.S. Securities and Exchange Commission (SEC) for interim reporting. As permitted under those rules, certain footnotes or other financial information that are normally required by GAAP have been omitted. In management’s opinion, the unaudited interim financial statements have been prepared on the same basis as the audited financial statements and include all adjustments, which include only normal recurring adjustments, necessary for the fair presentation of the Company’s financial position and its results of operations and its cash flows for the periods presented. These statements do not include all disclosures required by GAAP and should be read in conjunction with the Company’s Annual Report on Form 10-K filed for the fiscal year ended December 31, 2014 (the Annual Report). A copy of the Annual Report is available on the SEC’s website, www.sec.gov, under the Company’s ticker symbol (BLCM) or on Bellicum’s website, www.bellicum.com. The results for the interim periods are not necessarily indicative of the results expected for the full fiscal year or any other interim period. Any reference in these footnotes to applicable guidance is meant to refer to 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.

Historically, prior to the Company’s initial public offering of its common stock, or IPO, in December 2014, the fair values of the shares of common stock underlying the Company’s share-based awards were estimated on each grant date by its board of directors. Given the absence of a public trading market for the Company’s common stock, its board of directors exercised reasonable judgment and considered a number of objective and subjective factors to determine the best estimate of the fair value of its common stock, including the following:


•	its stage of development;


•	its operational and financial performance;


•	the nature of its services and its competitive position in the marketplace;


•	the value of companies that it considers peers based on a number of factors, including similarity to the Company with respect to industry and business model;


•	the likelihood of achieving a liquidity event, such as an initial public offering and the nature and history of its business;


•	issuances of preferred stock and the rights, preferences, and privileges of its preferred stock relative to those of its common stock;


•	business conditions and projections;


•	the history of the Company and progress of its research and development efforts and clinical trials; and


•	the lack of marketability of its common stock.

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 in the three and six months ended June 30, 2015, and results for the three and six months ended June 30, 2014 have been reclassified to conform to the current year presentation. The effect of the reclassification of the results for the three and six months ended June 30, 2014 was to increase research and development expense and reduce general and administrative expense by $0.4 million and $0.8 million, respectively, with no change in total operating expense or net loss.

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 were considered to be participating securities as they were 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.



	As of June 30,
Common Stock Equivalents:	2015	2014
Series A Preferred Stock Convertible Preferred Stock - as converted to common stock	—	1,496,782
Series B Preferred Stock Convertible Preferred Stock - as converted to common stock	—	4,791,740
Warrants to purchase common stock	355,392	473,031
Unvested shares of restricted stock	117,647	—
Options to purchase common stock	3,541,577	1,614,118
	4,014,616	8,375,671

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 and 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 at the time of purchase and reevaluates its classification as of each balance sheet date. All investment securities owned during the six months ended June 30, 2015, were 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 included in 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 statement of 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 comprehensive income (loss) and establishes a new cost basis in the investment.

Fair Value of Financial Instruments

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Fair Value of Financial Instruments

FAIR VALUE MEASUREMENTS AND INVESTMENT SECURITIES

Fair Value Measurement

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 June 30, 2015 and December 31, 2014, respectively (in thousands):



			Fair Value Measurements at Reporting Date Using
	Balance at June 30, 2015		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash Equivalents:
Money market funds	$	80,619	$	80,619	$	—	$	—
Government sponsored securities	17,000		—		17,000		—
Commercial paper	800		—		800		—
Total Cash Equivalents	$	98,419	$	80,619	$	17,800	$	—

Investment Securities:
U.S. Treasury and state government agency-backed securities	$	13,368	$	—	$	13,368	$	—
Corporate debt securities	51,306		—		51,306		—
Municipal bonds	6,245		—		6,245		—
Total Investment Securities	$	70,919	$	—	$	70,919	$	—



			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2014		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash Equivalents:
Money market funds	$	43,587	$	43,587	$	—	$	—
Total Cash Equivalents	$	43,587	$	43,587	$	—	$	—

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.

Investment securities, all classified as available-for-sale, consisted of the following as of June 30, 2015 (in thousands):



	June 30, 2015
Investment Securities:	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Estimated Fair Value
U.S. Treasury and U.S. or state government agency-backed securities	$	13,368	$	1	$	(1	)	$	13,368
Corporate debt securities	51,493		1		(188		)	51,306
Municipal bonds	6,262		—		(17		)	6,245
Total Investment Securities	$	71,123	$	2	$	(206	)	$	70,919

The Company's investment securities as of June 30, 2015, will reach maturity between July 2015 and June 2018, with a weighted-average maturity date in October 2017. There were no investment securities at December 31, 2014.

Stockholders' Equity	6 Months Ended
Stockholders' Equity	Jun. 30, 2015
Stockholders' Equity Attributable to Parent [Abstract]
Stockholders' Equity	STOCKHOLDERS' EQUITY Preferred Stock As of June 30, 2015 and December 31, 2014, the Company had 10,000,000 authorized shares of preferred stock, with none outstanding and a par value of $0.01 per share. Common Stock As of June 30, 2015 and December 31, 2014, the Company had 200,000,000 authorized shares of common stock with a par value of $0.01 per share. Reverse Stock Split On December 4, 2014, the Company’s board of directors and stockholders approved an amendment to the Company’s amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s common stock on a 1-for-1.7 basis (the Reverse Stock Split). The par value and the authorized shares of the common stock were not adjusted as a result of the Reverse Stock Split. All issued and outstanding common stock, options for common stock, warrants for common stock, and per share amounts contained in the financial statements have been retroactively adjusted to reflect this Reverse Stock Split for all periods presented.

Share-Based Compensation

6 Months Ended

Jun. 30, 2015

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

Share-based Compensation

SHARE-BASED COMPENSATION

At June 30, 2015, the Company had share-based awards outstanding under four share-based compensation plans as follows:

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. As of June 30, 2015, 160,174 shares of common stock were reserved for issuance pursuant to outstanding options previously granted under the 2006 Plan to purchase common stock of the Company. The 2006 Plan was terminated by the Board in October 2014.

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. As of June 30, 2015, 2,394,127 shares of common stock were reserved for issuance pursuant to outstanding options previously granted under the 2011 Plan to purchase common stock of the Company. The 2011 Plan terminated upon the effectiveness of the 2014 Plan described below.

The 2014 Equity Incentive Plan (the 2014 Plan) became effective in December 2014, upon the closing of our initial public offering. 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.

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 our 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 our common stock, pursuant to purchase rights granted to our employees. The ESPP was approved by our board of directors and our stockholders in December 2014 and employee payroll deductions of approximately $195,000 were withheld during the first six months of 2015. During the three and six months ended June 30, 2015, 9,829 stock purchases were made under the ESPP and the company received $159,000 in proceeds. The Company recorded share-based compensation expense of $109,000 for shares purchased for less than fair market value under the ESPP, during the three and six months ended June 30, 2015. There was $0.3 million of unrecognized compensation expense related to the ESPP as of June 30, 2015, which will be recognized over the remaining 18 months of the plan.

The Company granted options to purchase 132,000 and 847,100 shares of its common stock during the three and six months ended June 30, 2015, respectively. The fair value of the option grants during the three and six months ended June 30, 2015 and 2014 was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:



	Six months ended June 30,
	2015		2014
Expected volatility	75.9	%	95.0	%
Expected term (in years)	6.08		6.25
Risk-free interest rate	1.74	%	1.68	%
Expected dividend yield	—	%	—	%

At June 30, 2015, there was $29.1 million of unrecognized compensation expense related to unvested stock options and stock that is expected to be recognized over a weighted-average period of 3.5 years.

During the three and six months ended June 30, 2015, the company received cash proceeds from the exercise of stock options of approximately $81,000 and $83,000, respectively. The aggregate intrinsic value of options exercised during the three and six months ended June 30, 2015 was $0.7 million and $0.8 million, respectively.

The following table summarizes the stock option activity for all stock plans during the six months ended June 30, 2015:



	Options		Weighted- Average Exercise Price Per Share		(in years) Weighted- Average Contractual Life	(in thousands) Aggregate Intrinsic Value ⁽¹⁾
Outstanding at December 31, 2014	2,733,793		$	5.09	8.39	$	49,076
Granted	847,100		$	23.62
Exercised	(38,316	)	$	2.16
Canceled or forfeited	(1,000	)	$	23.36
Outstanding at June 30, 2015	3,541,577		$	9.55	8.35	$	43,505
Exercisable at June 30, 2015	1,303,423		$	2.30	6.67	$	24,720

⁽¹⁾The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value

of the common stock for the options that were in the money at June 30, 2015.

At June 30, 2015 and December 31, 2014, there were 117,647 shares of unvested common stock outstanding.

Grant Revenue	6 Months Ended
Grant Revenue	Jun. 30, 2015
Grant Revenue [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. In addition, CPRIT could award supplemental funding not to exceed ten percent of the total grant amount based upon the Company’s progress. The Grant Contract terminated on June 30, 2014. The terms of the Grant Contract require the Company to pay back two times the grant award through an initial mid-single digit royalty and then pay an ongoing low single digit royalty on revenues from sales and licenses of intellectual property facilitated by the Grant Contract. During the three and six months ended June 30, 2014, the Company incurred $0.4 million and $0.9 million, respectively, of expenses under the Grant Contract. As of June 30, 2015 and December 31, 2014, the Company had an outstanding grant receivable of $- and $0.3 million respectively, for grant expenditures that were paid but had not yet been reimbursed. NIH Grant During each of the years 2015 and 2014, the Company was awarded $0.3 million under a grant from the National Institutes of Health (NIH). The awards cover the period from April 2014 through March 2016. 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 June 30, 2015 and 2014, funds spent under the grant were $0.2 million each. As of June 30, 2015 and December 31, 2014, the Company had a receivable of $44,000 and $-, respectively.

License Agreements	6 Months Ended
License Agreements	Jun. 30, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
License Agreements	LICENSE AGREEMENTS 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. 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 also agreed to enter into a sponsored research agreement, to be separately negotiated, pursuant to which the Company would be required to pay Leiden up to EUR 300,000 over a three-year 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.

Commitments and Contingencies	6 Months Ended
Commitments and Contingencies	Jun. 30, 2015
Commitments and Contingencies Disclosure [Abstract]
Commitments Contingencies	COMMITMENTS AND CONTINGENCIES Lease Agreement On May 6, 2015, the Company entered into a lease agreement (the Lease) with Sheridan Hills Developments L.P. (the Landlord) for the lease of three spaces of approximately 25,304 square feet (the Manufacturing Space), 705 square feet (the Interior Mechanical Space) and 808 square feet (the Exterior Mechanical Space), respectively, which the Company will use to enable in-house cell therapy manufacturing. The term of the Lease will begin on September 1, 2015 and continue for an initial term of five years, which may be renewed for five additional one-year periods. For the Manufacturing Space, the Company is required to remit base monthly rent of approximately $64,841 which will increase at an average approximate rate of 3.5% each year. For the Interior Mechanical Space, the Company is required to remit base monthly rent of approximately $1,219, which will increase at an average approximate rate of 5% each year. The monthly base rent for the Exterior Mechanical Space is approximately $471. The Company is also required to pay additional rent in the form of its pro rata share of certain specified operating expenses of the Landlord. An early termination right is available to the Company upon certain events, including the Landlord’s default on its obligations under the Lease. The newly leased spaces are located within the same building as the Company’s current headquarters in Houston, Texas and are accounted for as operating leases. 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.

Significant Accounting Policies (Policies)

6 Months Ended

Jun. 30, 2015

Accounting Policies [Abstract]

Basis of Presentation

Use of Estimates


•	its stage of development;


•	its operational and financial performance;


•	the nature of its services and its competitive position in the marketplace;


•	the value of companies that it considers peers based on a number of factors, including similarity to the Company with respect to industry and business model;


•	the likelihood of achieving a liquidity event, such as an initial public offering and the nature and history of its business;


•	issuances of preferred stock and the rights, preferences, and privileges of its preferred stock relative to those of its common stock;


•	business conditions and projections;


•	the history of the Company and progress of its research and development efforts and clinical trials; and


•	the lack of marketability of its common stock.

Reclassifications

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

Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2015

Accounting Policies [Abstract]

Earnings Per Share, Potentially Dilutive Securities



	As of June 30,
Common Stock Equivalents:	2015	2014
Series A Preferred Stock Convertible Preferred Stock - as converted to common stock	—	1,496,782
Series B Preferred Stock Convertible Preferred Stock - as converted to common stock	—	4,791,740
Warrants to purchase common stock	355,392	473,031
Unvested shares of restricted stock	117,647	—
Options to purchase common stock	3,541,577	1,614,118
	4,014,616	8,375,671

Fair Value of Financial Instruments (Tables)

6 Months Ended

Jun. 30, 2015

Fair Value Disclosures [Abstract]

Fair Value, by Balance Sheet Grouping



			Fair Value Measurements at Reporting Date Using
	Balance at June 30, 2015		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash Equivalents:
Money market funds	$	80,619	$	80,619	$	—	$	—
Government sponsored securities	17,000		—		17,000		—
Commercial paper	800		—		800		—
Total Cash Equivalents	$	98,419	$	80,619	$	17,800	$	—

Investment Securities:
U.S. Treasury and state government agency-backed securities	$	13,368	$	—	$	13,368	$	—
Corporate debt securities	51,306		—		51,306		—
Municipal bonds	6,245		—		6,245		—
Total Investment Securities	$	70,919	$	—	$	70,919	$	—



			Fair Value Measurements at Reporting Date Using
	Balance at December 31, 2014		Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)
Cash Equivalents:
Money market funds	$	43,587	$	43,587	$	—	$	—
Total Cash Equivalents	$	43,587	$	43,587	$	—	$	—

Available-for-sale Securities

Investment securities, all classified as available-for-sale, consisted of the following as of June 30, 2015 (in thousands):



	June 30, 2015
Investment Securities:	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Aggregate Estimated Fair Value
U.S. Treasury and U.S. or state government agency-backed securities	$	13,368	$	1	$	(1	)	$	13,368
Corporate debt securities	51,493		1		(188		)	51,306
Municipal bonds	6,262		—		(17		)	6,245
Total Investment Securities	$	71,123	$	2	$	(206	)	$	70,919

Share-Based Compensation (Tables)

6 Months Ended

Jun. 30, 2015

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

Valuation Assumptions

The fair value of the option grants during the three and six months ended June 30, 2015 and 2014 was estimated at the date of grant using the Black-Scholes option pricing model with the following weighted-average assumptions:



	Six months ended June 30,
	2015		2014
Expected volatility	75.9	%	95.0	%
Expected term (in years)	6.08		6.25
Risk-free interest rate	1.74	%	1.68	%
Expected dividend yield	—	%	—	%

Schedule of Share-based Compensation, Stock Options, Activity

The following table summarizes the stock option activity for all stock plans during the six months ended June 30, 2015:



	Options		Weighted- Average Exercise Price Per Share		(in years) Weighted- Average Contractual Life	(in thousands) Aggregate Intrinsic Value ⁽¹⁾
Outstanding at December 31, 2014	2,733,793		$	5.09	8.39	$	49,076
Granted	847,100		$	23.62
Exercised	(38,316	)	$	2.16
Canceled or forfeited	(1,000	)	$	23.36
Outstanding at June 30, 2015	3,541,577		$	9.55	8.35	$	43,505
Exercisable at June 30, 2015	1,303,423		$	2.30	6.67	$	24,720

⁽¹⁾The aggregate intrinsic value is calculated as the difference between the exercise price of the underlying options and the estimated fair value

of the common stock for the options that were in the money at June 30, 2015.

Significant Accounting Policies Common Stock Equivalents (Details) (USD $) In Millions, except Share data, unless otherwise specified	6 Months Ended												3 Months Ended	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015 Warrant [Member]	Jun. 30, 2014 Warrant [Member]	Jun. 30, 2015 Series A Preferred Stock [Member]	Jun. 30, 2014 Series A Preferred Stock [Member]	Jun. 30, 2015 Series B Preferred Stock [Member]	Jun. 30, 2014 Series B Preferred Stock [Member]	Jun. 30, 2015 Restricted Stock [Member]	Jun. 30, 2014 Restricted Stock [Member]	Jun. 30, 2015 Equity Option [Member]	Jun. 30, 2014 Equity Option [Member]	Jun. 30, 2014 Research and Development Expense [Member]	Jun. 30, 2014 Research and Development Expense [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Prior Period Reclassification Adjustment													$ 0.4	$ 0.8
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	4,014,616	8,375,671	355,392	473,031	0	1,496,782	0	4,791,740	117,647	0	3,541,577	1,614,118

Fair Value of Financial Instruments (Details) (Fair Value, Measurements, Recurring [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2015	Dec. 31, 2014
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Money Market Funds, at Carrying Value	$ 80,619	$ 43,587
US Government Agencies Securities, at Carrying Value	17,000
Commercial Paper	800
Assets, Fair Value Disclosure	98,419	43,587
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	13,368
Financial Instruments, Owned, Corporate Debt, at Fair Value	51,306
Municipal Investment Agreements	6,245
Investments, Fair Value Disclosure	70,919
Fair Value, Inputs, Level 1 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Money Market Funds, at Carrying Value	80,619	43,587
Commercial Paper	0
Assets, Fair Value Disclosure	80,619	43,587
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0
Financial Instruments, Owned, Corporate Debt, at Fair Value	0
Municipal Investment Agreements	0
Investments, Fair Value Disclosure	0
Fair Value, Inputs, Level 2 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Money Market Funds, at Carrying Value	0	0
US Government Agencies Securities, at Carrying Value	17,000
Commercial Paper	800
Assets, Fair Value Disclosure	17,800	0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	13,368
Financial Instruments, Owned, Corporate Debt, at Fair Value	51,306
Municipal Investment Agreements	6,245
Investments, Fair Value Disclosure	70,919
Fair Value, Inputs, Level 3 [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Money Market Funds, at Carrying Value	0	0
US Government Agencies Securities, at Carrying Value	0
Commercial Paper	0
Assets, Fair Value Disclosure	0	0
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	0
Financial Instruments, Owned, Corporate Debt, at Fair Value	0
Municipal Investment Agreements	0
Investments, Fair Value Disclosure	$ 0

Fair Value of Financial Instruments - Fair Value (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2015
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 71,123
Gross Unrealized Gains	2
Gross Unrealized Losses	(206)
Aggregate Estimated Fair Value	70,919
US Treasury and U.S. or state government agency-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,368
Gross Unrealized Gains	1
Gross Unrealized Losses	(1)
Aggregate Estimated Fair Value	13,368
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	51,493
Gross Unrealized Gains	1
Gross Unrealized Losses	(188)
Aggregate Estimated Fair Value	51,306
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,262
Gross Unrealized Gains	0
Gross Unrealized Losses	(17)
Aggregate Estimated Fair Value	$ 6,245

Accrued Expenses (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2015	Dec. 31, 2014
Accrued Expenses [Abstract]
Accrued payroll	$ 0	$ 731
Commission on exercise of warrants	0	731
Medical facility fees	989	201
Patient treatment costs	261	128
Other	504	372
Total accrued expenses	$ 1,754	$ 2,163

Stockholders' Equity (Details) (USD $)	0 Months Ended
Stockholders' Equity (Details) (USD $)	Dec. 04, 2014	Jun. 30, 2015	Dec. 31, 2014
Stockholders' Equity Attributable to Parent [Abstract]
Preferred stock authorized (shares)		10,000,000	10,000,000
Preferred stock outstanding (shares)		0	0
Preferred stock par value (usd per share)		$ 0.01	$ 0.01
Common stock, authorized (shares)		200,000,000	200,000,000
Common stock, par value (usd per share)		$ 0.01	$ 0.01
Reverse stock split	1-for-1.7 basis
Stock split ratio	0.5882

Share-Based Compensation Narrative (Details) (USD $)	3 Months Ended	6 Months Ended	12 Months Ended
Share-Based Compensation Narrative (Details) (USD $)	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of share-based compensation plans		4
Granted (shares)	132,000	847,100
Compensation cost not yet recognized	$ 29,100,000	$ 29,100,000
Period for recognition		3 years 6 months
Cash received from exercise of stock options	81,000	83,000
Intrinsic value of options, exercises in period	700,000	800,000
Equity instruments other than options, nonvested	117,647	117,647	117,647
2006 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	160,174	160,174
2011 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	2,394,127	2,394,127
2014 Stock Option Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized	2,990,354	2,990,354
2014 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant			550,000
Employee stock purchase plan cash contributions	109,000	159,000	195,000
Allocated share-based compensation expense		109,000
Stock issued during period, shares, employee stock purchase plans	9,829	9,829
Compensation cost not yet recognized	$ 300,000	$ 300,000
Period for recognition		18 months

Share-Based Compensation Valuation Assumptions (Details)	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Expected volatility	75.90%	95.00%
Expected term (in years)	6 years 29 days	6 years 3 months
Risk-free interest rate	1.74%	1.68%
Expected dividend yield	0.00%	0.00%

Share-Based Compensation Stock Option Activity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended	6 Months Ended	12 Months Ended
	Jun. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Options
December 31, 2014 (shares)		2,733,793
Granted (shares)	132,000	847,100
Exercised (shares)		(38,316)
Canceled or forfeited (shares)		(1,000)
Outstanding at June 30, 2015 (shares)	3,541,577	3,541,577	2,733,793
Exercisable at June 30, 2015 (shares)	1,303,423	1,303,423
Weighted- Average Exercise Price Per Share
December 31, 2014 (usd per share)		$ 5.09
Granted (usd per share)		$ 23.62
Exercised (usd per share)		$ 2.16
Canceled or forfeited (usd per share)		$ 23.36
Outstanding at June 30, 2015 (usd per share)	$ 9.55	$ 9.55	$ 5.09
Exercisable at June 30, 2015 (usd per share)	$ 2.30	$ 2.30
Additional Disclosures [Abstract]
Weighted Average Remaining Contractual Term, Outstanding		8 years 4 months 6 days	8 years 4 months 21 days
Weighted Average Remaining Contractual Term, Exercisable		6 years 8 months 1 day
Aggregate Intrinsic Value, Outstanding	$ 43,505	$ 43,505	$ 49,076
Aggregate Intrinsic Value, Exercisable	$ 24,720	$ 24,720

Grant Revenue (Details) (USD $)	3 Months Ended		6 Months Ended		0 Months Ended	3 Months Ended	6 Months Ended			6 Months Ended
Grant Revenue (Details) (USD $)	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Jul. 27, 2011 Cancer Prevention and Research Institute of Texas [Member]	Jun. 30, 2014 Cancer Prevention and Research Institute of Texas [Member]	Jun. 30, 2014 Cancer Prevention and Research Institute of Texas [Member]	Jun. 30, 2015 Cancer Prevention and Research Institute of Texas [Member]	Dec. 31, 2014 Cancer Prevention and Research Institute of Texas [Member]	Jun. 30, 2015 National Institutes of Health Grant [Member]	Jun. 30, 2014 National Institutes of Health Grant [Member]	Dec. 31, 2014 National Institutes of Health Grant [Member]
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue from grants	$ 84,000	$ 554,000	$ 191,000	$ 1,106,000	$ 5,700,000					$ 300,000	$ 300,000
Percentage of grant					0.1
Costs and expenses						400,000	900,000			200,000	100,000
Grants receivable								$ 0	$ 300,000	$ 44,000		$ 0

License Agreements (Details) (Licensing Agreements [Member])	0 Months Ended	6 Months Ended	0 Months Ended
	Jun. 10, 2015 BioVec Pharma Inc [Member] USD ($)	Jun. 30, 2015 BioVec Pharma Inc [Member]	Apr. 23, 2015 Academisch Ziekenhuis Leiden [Member] EUR (€)
Finite-Lived Intangible Assets [Line Items]
License costs due upon first release of product	$ 300,000
License agreement first release fee period	10 days
License costs for rights granted under agreement	100,000		75,000
License agreement upfront fee period	10 days		30 days
License agreement, annual fee	150,000
Annual fee period, duration after first IND filing		30 days
Milestone payments upon registration with FDA or EMA	2,000,000
License agreement advance notice of research collaborations			30 days
Minimum annual royalty payments beginning on eighth anniversary			30,000
Milestone payments for first licensed products	250,000		1,025,000
License agreement sponsored research			€ 300,000
Term of payments under sponsored research agreement			3 years
License agreement termination notice			6 months
License agreement period of notice of failure on uncured items			30 days
License agreement termination period after written notice of failure			30 days
License agreement period after insolvency event			45 days

Commitments and Contingencies (Details) (USD $)	0 Months Ended
Commitments and Contingencies (Details) (USD $)	May 06, 2015 renewal_option Location sqft
Commitments and Contingencies Disclosure [Abstract]
Number of spaces in manufacturing area	3
Number of square feet of manufacturing space	25,304
Number of square feet of exterior mechanical space	705
Number of square feet of interior mechanical space	808
Operating leases, number of renewal options	5
Operating leases, term of contract	5 years
Additional lease renewal periods	1 year
Lease monthly rent amount	$ 64,841
Average lease rent percentage annual increase	3.50%
Lease monthly rent amount - interior mechanical space	1,219
Annual lease rent percentage annual increase on interior mechanical space	5.00%
Lease monthly rent amount - exterior mechanical space	$ 471