Five Prime Therapeutics (FPRX) 10-Q 7 Aug 15 2015 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2015	Jul. 31, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2015
Document Fiscal Year Focus	2,015
Document Fiscal Period Focus	Q2
Trading Symbol	FPRX
Entity Registrant Name	FIVE PRIME THERAPEUTICS INC
Entity Central Index Key	1,175,505
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		25,805,249

Condensed Balance Sheets

Condensed Balance Sheets - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 19,096	$ 15,267
Marketable securities	188,310	133,787
Receivable from collaborative partners	718	410
Prepaid and other current assets	2,587	1,794
Total current assets	210,711	151,258
Property and equipment, net	4,387	3,794
Other long-term assets	423	579
Total assets	215,521	155,631
Current liabilities:
Accounts payable	1,353	1,096
Accrued personnel-related expenses	3,094	4,618
Other accrued liabilities	3,344	1,531
Deferred revenue, current portion	12,601	11,938
Deferred rent, current portion	719	632
Total current liabilities	21,111	19,815
Deferred revenue, long-term portion	46,800	48,628
Deferred rent, long-term portion	1,249	1,514
Other long-term liabilities	$ 442	$ 469
Commitments
Stockholders' equity:
Common stock	$ 26	$ 22
Preferred stock
Additional paid-in capital	$ 357,329	$ 274,180
Accumulated other comprehensive income	72	1
Accumulated deficit	(211,508)	(188,998)
Total stockholders' equity	145,919	85,205
Total liabilities and stockholders' equity	$ 215,521	$ 155,631

Condensed Statements of Operati

Condensed Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Income Statement [Abstract]
Collaboration and license revenue	$ 6,315	$ 4,981	$ 10,602	$ 8,527
Operating expenses:
Research and development	13,310	11,873	24,521	20,799
General and administrative	4,596	3,024	8,816	6,304
Total operating expenses	17,906	14,897	33,337	27,103
Loss from operations	(11,591)	(9,916)	(22,735)	(18,576)
Interest income	117	55	225	91
Other expense, net		(5)		(25)
Net loss	$ (11,474)	$ (9,866)	$ (22,510)	$ (18,510)
Basic and diluted net loss per common share	$ (0.45)	$ (0.46)	$ (0.89)	$ (0.92)
Shares used to compute basic and diluted net loss per common share	25,690	21,465	25,383	20,160

Condensed Statements of Compreh

Condensed Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (11,474)	$ (9,866)	$ (22,510)	$ (18,510)
Other comprehensive income:
Net unrealized gain on marketable securities	41	22	71	38
Comprehensive loss	$ (11,433)	$ (9,844)	$ (22,439)	$ (18,472)

Condensed Statement of Cash Flo

Condensed Statement of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014
Operating activities
Net loss	$ (22,510)	$ (18,510)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	823	772
Stock-based compensation expense	2,203	1,376
Amortization of premium on marketable securities	1,042	628
Changes in operating assets and liabilities:
Receivable from collaborative partners	(308)	119
Prepaid, other current assets, and other long-term assets	(637)	(33)
Accounts payable	257	419
Accrued personnel-related expenses	(1,524)	(638)
Deferred revenue	(1,165)	19,660
Deferred rent	(178)	(275)
Other accrued liabilities and other long-term liabilities	1,786	2,940
Net cash provided by (used in) operating activities	(20,211)	6,458
Investing activities
Purchases of marketable securities	(102,994)	(106,451)
Maturities of marketable securities	47,500	45,900
Purchases of property and equipment	(1,416)	(985)
Net cash used in investing activities	(56,910)	(61,536)
Financing activities
Proceeds from public offering of common stock, net	78,693	40,099
Proceeds from the sale of common stock to collaborative partner		18,629
Proceeds from issuance of common stock under equity incentive plans	2,257	1,248
Net cash provided by financing activities	80,950	59,976
Net increase in cash and cash equivalents	3,829	4,898
Cash and cash equivalents at beginning of period	15,267	8,161
Cash and cash equivalents at end of period	$ 19,096	$ 13,059

Description of Business

Description of Business	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Description of Business	1. Description of Business Five Prime Therapeutics, Inc. (we, us, our or the Company) is a clinical-stage biotechnology company focused on discovering and developing novel protein therapeutics. Protein therapeutics are antibodies or drugs developed from extracellular proteins or protein fragments that block disease processes, including cancer and inflammatory diseases. We were incorporated in December 2001 in Delaware. Our operations are based in South San Francisco, California and we operate in one segment. Unaudited Interim Financial Information The accompanying financial information as of June 30, 2015 is unaudited. The Condensed Financial Statements included in this report reflect all adjustments (consisting only of normal recurring adjustments) that our management considers necessary for the fair statement of the results of operations for the interim periods covered and of the financial condition of the Company at the date of the interim balance sheet. The Condensed Balance Sheet as of December 31, 2014 was derived from audited financial statements, but does not include all disclosures required by generally accepted accounting principles in the United States of America, or GAAP. The results for interim periods are not necessarily indicative of the results for the entire year or any other interim period. The accompanying Condensed Financial Statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 filed with the U.S. Securities and Exchange Commission. Follow-on Public Offering In January 2015, we closed an underwritten public offering of 3,829,994 78.7

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions about future events that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements as well as reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates. Fair Value of Financial Instruments We determine the fair value of financial and nonfinancial assets and liabilities using the fair value hierarchy, which describes three levels of inputs that may be used to measure fair value, as follows: Level 1 —Quoted prices in active markets for identical assets or liabilities; Level 2 —Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. We determine the fair value of Level 1 assets using quoted prices in active markets for identical assets. We review trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data. In certain cases where there is limited activity or less transparency around inputs to valuation, we classify securities as Level 3 within the valuation hierarchy. We do not have any Level 3 securities as of June 30, 2015. The following table summarizes, for assets recorded at fair value, the respective fair values and the classifications by level of input within the fair value hierarchy defined above (in thousands): June 30, 2015 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 9,842 $ 9,842 $ — $ — U.S. Treasury securities 188,310 188,310 — — Total cash equivalents and marketable securities $ 198,152 $ 198,152 $ — $ — December 31, 2014 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 9,996 $ 9,996 $ — $ — U.S. Treasury securities 130,786 130,786 — — U.S. government agency securities 3,001 — 3,001 — Total cash equivalents and marketable securities $ 143,783 $ 140,782 $ 3,001 $ — Net Loss Per Share of Common Stock We compute basic net loss per common share by dividing net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. We excluded the following options and restricted stock awards, or RSAs, to purchase shares of common stock (in thousands) from the calculation of diluted net loss per share for all periods presented as the effect would have been antidilutive: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Options and RSAs to purchase common stock 2,604 2,141 2,635 2,177 2,604 2,141 2,635 2,177 Recently Issued Accounting Standards In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers: Topic

Cash Equivalents and Marketable

Cash Equivalents and Marketable Securities	6 Months Ended
	Jun. 30, 2015
Cash And Cash Equivalents [Abstract]
Cash Equivalents and Marketable Securities	3. Cash Equivalents and Marketable Securities The following is a summary of our cash equivalents and marketable securities (in thousands): June 30, 2015 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 9,842 $ — $ — $ 9,842 U.S. Treasury securities 188,238 72 — 188,310 198,080 72 — 198,152 Less: cash equivalents (9,842 ) — — (9,842 ) Total marketable securities $ 188,238 $ 72 $ — $ 188,310 December 31, 2014 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 9,996 $ — $ — $ 9,996 U.S. Treasury securities 130,785 18 (17 ) 130,786 U.S. government agency securities 3,001 — — 3,001 143,782 18 (17 ) 143,783 Less: cash equivalents (9,996 ) — — (9,996 ) Total marketable securities $ 133,786 $ 18 $ (17 ) $ 133,787 As of June 30, 2015, the amortized cost and estimated fair value of our available-for-sale securities by contractual maturity are shown below (in thousands): Amortized Estimated Cost Fair Value Debt securities maturing: In one year or less $ 167,407 $ 167,466 In one to two years 20,831 20,844 Total marketable securities $ 188,238 $ 188,310 We did not have any gross unrealized losses from our marketable securities as of June 30, 2015. We made no sales of available-for-sale securities in any of the periods presented.

Equity Incentive Plans

Equity Incentive Plans	6 Months Ended
	Jun. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Equity Incentive Plans	4. Equity Incentive Plans The following table summarizes option activity under our stock plans and related information: Options Outstanding Weighted Weighted Average Average Number of Exercise Price Remaining Shares Per Share Term Balance at December 31, 2014 2,684,812 $ 7.85 Options granted 143,288 $ 22.27 Options exercised (210,704 ) $ 6.77 Options forfeited (75,895 ) $ 8.76 Options expired (10,465 ) $ 8.03 Balance at June 30, 2015 2,531,036 $ 8.73 Options exercisable 1,502,968 $ 6.78 5.79 We have granted restricted stock awards, or RSAs, to certain employees. RSAs are share awards that entitle the holder to receive freely tradable shares of our common stock upon vesting and are unforfeitable once fully vested. We based the fair value of RSAs on the closing sales price of our common stock on the grant date. The following table summarizes the RSAs activity under our stock plans and related information: RSAs Outstanding Weighted-Average Number Grant-Date of Shares Fair Value Unvested balance at January 1, 2015 24,000 $ 12.18 RSAs granted 70,370 $ 20.06 RSAs vested — $ — RSAs forfeited (4,120 ) $ 20.06 Unvested balance at June 30, 2015 90,250 $ 18.07 As of June 30, 2015, there were 4,102,609 shares of common stock available for future issuance under our 2013 Omnibus Incentive Plan. Stock-Based Compensation We calculate employee stock-based compensation expense based on awards ultimately expected to vest reduced by estimated forfeitures. We estimate forfeitures at the time of grant and revise forfeitures, if necessary, in subsequent periods if actual forfeitures differ from those estimates. Total stock-based compensation expense recognized was as follows (in thousands): Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Research and development $ 596 $ 369 $ 1,105 $ 729 General and administrative 616 371 1,098 647 Total $ 1,212 $ 740 $ 2,203 $ 1,376 We estimated the fair value of each stock option using the Black-Scholes option-pricing model based on the date of grant of such stock option with the following assumptions: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Expected term (years) 5.5-6.1 5.3-6.1 5.5-6.1 5.3-6.1 Expected volatility 71 % 85 % 71-73% 85 % Risk-free interest rate 1.4-1.9 1.6-1.9% 1.4-1.9 1.6-1.9% Expected dividend yield 0 % 0 % 0 % 0 % As of June 30, 2015, we had $7.2 million of total unrecognized compensation expense related to nonvested employee and director stock options that we expect to recognize over a weighted-average period of 2.5 years.

License Agreement

License Agreement	6 Months Ended
	Jun. 30, 2015
License Agreement [Abstract]
License Agreement	5. License Agreement bluebird bio, Inc. In May 2015, we entered into an exclusive license agreement, referred to as the license agreement, with bluebird bio, Inc., or bluebird, under which we licensed to bluebird human antibodies to an undisclosed cancer target to research, develop and commercialize chimeric antigen receptor (CAR) T cell therapies using these antibodies. Under the license agreement, bluebird paid us a $1.5 million upfront fee and is obligated to pay us subsequent milestone payments, which together could total up to $131.0 million per licensed product if bluebird achieves certain development, regulatory and commercial milestones. We are also eligible to receive tiered royalties on product sales. bluebird will conduct and fund clinical development as well as regulatory and commercial activities. There are no other deliverables under the agreement other than the license grant. We recognized the $1.5 million upfront fee as revenue upon delivery of the license grant, which was completed in the three months ended June 30, 2015. In accordance with ASU No. 2010-17, Milestone Method of Revenue Recognition The license agreement will expire upon the fulfillment of all payment obligations under the license agreement. In addition, bluebird may terminate the license agreement in its entirety without cause at any time with advance written notice and either party may terminate the license agreement in its entirety with written notice for the other party’s material breach if such party fails to cure the breach or immediately upon certain insolvency events.

Employee Benefit Plans

Employee Benefit Plans	6 Months Ended
	Jun. 30, 2015
Postemployment Benefits [Abstract]
Employee Benefit Plans	6 . Employee Benefit Plans We sponsor a 401(k) plan under which eligible employees may elect to contribute to the 401(k) plan, subject to certain limitations, up to the lesser of the statutory maximum or 100% of eligible compensation on a pre-tax basis. We pay the administrative costs for the plan. Effective January 1, 2015, we elected to match employee contributions to the 401(k) plan, or the Company Match, as permitted by the plan. We plan to make matching contributions on June 15 and December 15 each year in an amount equal to 50% of the amount contributed by the employee up to an annual maximum Company Match per employee equal to the lesser of (i) 4% of such employee’s compensation; or (ii) $6,000. We deliver the Company Match through the issuance of shares of our common stock. We delivered 13,720 shares of our common stock as the Company Match on June 15, 2015 and recorded 401(k) plan Company Match expense of $157,000 and $336,000 for the three and six months ended June 30, 2015.

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2015
Subsequent Events [Abstract]
Subsequent Events	7 . Subsequent Event In July 2015, we entered into a research collaboration and license agreement with INBRX 110 LP, or Inhibrx, to obtain (a) an exclusive, worldwide license to antibodies to glucocorticoid-induced tumor necrosis factor receptor, or GITR, for therapeutic and diagnostic uses, which we refer to respectively as licensed therapeutic products and licensed diagnostic products, and (b) an exclusive option, or the option, to obtain exclusive, worldwide licenses to multi-specific antibodies developed by Inhibrx that bind to both GITR and other targets, each of which we refer to as a multi-specific product. We can exercise an option with respect to a multi-specific product within a limited period of time after (i) certain activities related to initiating clinical manufacturing of such multi-specific product or (ii) if not earlier exercised, the dosing of the first patient in a Phase 2 clinical trial of such multi-specific product. Pursuant to the collaboration agreement, we paid Inhibrx an upfront fee of $10.0 million. Additionally, with respect to each licensed therapeutic product, we will be obligated to pay up to $62.5 million in specified development milestone payments and (i) if such licensed therapeutic product does not receive a Breakthrough Therapy Designation from the U.S. Food and Drug Administration, or FDA, up to $280.0 million in specified regulatory and commercial milestone payments, or (ii) if such licensed therapeutic product receives a Breakthrough Therapy Designation from the FDA, up to $380.0 million in specified regulatory and commercial milestone payments. Inhibrx is also eligible for low double-digit tiered royalties on future product sales. We may pay all or a portion of milestone payments for development and regulatory events in shares of our common stock, subject to certain limitations and conditions. We would be obligated to register for resale under the Securities Act of 1933, as amended, or the Securities Act, any such shares of our common stock.

Description of Business (Polici

Description of Business (Policies)	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Unaudited Interim Financial Information	Unaudited Interim Financial Information The accompanying financial information as of June 30, 2015 is unaudited. The Condensed Financial Statements included in this report reflect all adjustments (consisting only of normal recurring adjustments) that our management considers necessary for the fair statement of the results of operations for the interim periods covered and of the financial condition of the Company at the date of the interim balance sheet. The Condensed Balance Sheet as of December 31, 2014 was derived from audited financial statements, but does not include all disclosures required by generally accepted accounting principles in the United States of America, or GAAP. The results for interim periods are not necessarily indicative of the results for the entire year or any other interim period. The accompanying Condensed Financial Statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2014 filed with the U.S. Securities and Exchange Commission.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with GAAP requires management to make estimates and assumptions about future events that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities as of the date of the financial statements as well as reported amounts of revenue and expenses during the reporting period. Actual results could differ materially from those estimates.
Fair Value of Financial Instruments	Fair Value of Financial Instruments We determine the fair value of financial and nonfinancial assets and liabilities using the fair value hierarchy, which describes three levels of inputs that may be used to measure fair value, as follows: Level 1 —Quoted prices in active markets for identical assets or liabilities; Level 2 —Observable inputs other than Level 1 prices such as quoted prices for similar assets or liabilities, quoted prices for identical or similar assets or liabilities in markets that are not active, or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities; and Level 3 —Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. We determine the fair value of Level 1 assets using quoted prices in active markets for identical assets. We review trading activity and pricing for Level 2 investments as of each measurement date. Level 2 inputs, obtained from various third-party data providers, represent quoted prices for similar assets in active markets and were derived from observable market data, or, if not directly observable, were derived from or corroborated by other observable market data. In certain cases where there is limited activity or less transparency around inputs to valuation, we classify securities as Level 3 within the valuation hierarchy. We do not have any Level 3 securities as of June 30, 2015. The following table summarizes, for assets recorded at fair value, the respective fair values and the classifications by level of input within the fair value hierarchy defined above (in thousands): June 30, 2015 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 9,842 $ 9,842 $ — $ — U.S. Treasury securities 188,310 188,310 — — Total cash equivalents and marketable securities $ 198,152 $ 198,152 $ — $ — December 31, 2014 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 9,996 $ 9,996 $ — $ — U.S. Treasury securities 130,786 130,786 — — U.S. government agency securities 3,001 — 3,001 — Total cash equivalents and marketable securities $ 143,783 $ 140,782 $ 3,001 $ —
Net Loss Per Share of Common Stock	Net Loss Per Share of Common Stock We compute basic net loss per common share by dividing net loss attributable to common stockholders by the weighted-average number of shares of common stock outstanding during the period. We excluded the following options and restricted stock awards, or RSAs, to purchase shares of common stock (in thousands) from the calculation of diluted net loss per share for all periods presented as the effect would have been antidilutive: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Options and RSAs to purchase common stock 2,604 2,141 2,635 2,177 2,604 2,141 2,635 2,177
Recently Issued Accounting Standards	Recently Issued Accounting Standards In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers: Topic

Summary of Significant Accoun14

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2015
Accounting Policies [Abstract]
Summary of Assets Recorded at Fair Value	The following table summarizes, for assets recorded at fair value, the respective fair values and the classifications by level of input within the fair value hierarchy defined above (in thousands): June 30, 2015 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 9,842 $ 9,842 $ — $ — U.S. Treasury securities 188,310 188,310 — — Total cash equivalents and marketable securities $ 198,152 $ 198,152 $ — $ — December 31, 2014 Basis of Fair Value Measurements Total Level 1 Level 2 Level 3 Assets Money market funds $ 9,996 $ 9,996 $ — $ — U.S. Treasury securities 130,786 130,786 — — U.S. government agency securities 3,001 — 3,001 — Total cash equivalents and marketable securities $ 143,783 $ 140,782 $ 3,001 $ —
Options and Restricted Stock Awards Excluded from Calculation of Diluted Net Loss Per Share	We excluded the following options and restricted stock awards, or RSAs, to purchase shares of common stock (in thousands) from the calculation of diluted net loss per share for all periods presented as the effect would have been antidilutive: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Options and RSAs to purchase common stock 2,604 2,141 2,635 2,177 2,604 2,141 2,635 2,177

Cash Equivalents and Marketab15

Cash Equivalents and Marketable Securities (Tables)	6 Months Ended
	Jun. 30, 2015
Cash And Cash Equivalents [Abstract]
Summary of Cash Equivalents and Marketable Securities	The following is a summary of our cash equivalents and marketable securities (in thousands): June 30, 2015 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 9,842 $ — $ — $ 9,842 U.S. Treasury securities 188,238 72 — 188,310 198,080 72 — 198,152 Less: cash equivalents (9,842 ) — — (9,842 ) Total marketable securities $ 188,238 $ 72 $ — $ 188,310 December 31, 2014 Amortized Unrealized Unrealized Estimated Cost Basis Gains Losses Fair Value Money market funds $ 9,996 $ — $ — $ 9,996 U.S. Treasury securities 130,785 18 (17 ) 130,786 U.S. government agency securities 3,001 — — 3,001 143,782 18 (17 ) 143,783 Less: cash equivalents (9,996 ) — — (9,996 ) Total marketable securities $ 133,786 $ 18 $ (17 ) $ 133,787
Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale Securities by Contractual Maturity	As of June 30, 2015, the amortized cost and estimated fair value of our available-for-sale securities by contractual maturity are shown below (in thousands): Amortized Estimated Cost Fair Value Debt securities maturing: In one year or less $ 167,407 $ 167,466 In one to two years 20,831 20,844 Total marketable securities $ 188,238 $ 188,310

Equity Incentive Plans (Tables)

Equity Incentive Plans (Tables)	6 Months Ended
	Jun. 30, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Schedule of Option Activity under Stock Plans and Related Information	The following table summarizes option activity under our stock plans and related information: Options Outstanding Weighted Weighted Average Average Number of Exercise Price Remaining Shares Per Share Term Balance at December 31, 2014 2,684,812 $ 7.85 Options granted 143,288 $ 22.27 Options exercised (210,704 ) $ 6.77 Options forfeited (75,895 ) $ 8.76 Options expired (10,465 ) $ 8.03 Balance at June 30, 2015 2,531,036 $ 8.73 Options exercisable 1,502,968 $ 6.78 5.79
Schedule of Restricted Stock Award Activity under Stock Plans and Related Information	The following table summarizes the RSAs activity under our stock plans and related information: RSAs Outstanding Weighted-Average Number Grant-Date of Shares Fair Value Unvested balance at January 1, 2015 24,000 $ 12.18 RSAs granted 70,370 $ 20.06 RSAs vested — $ — RSAs forfeited (4,120 ) $ 20.06 Unvested balance at June 30, 2015 90,250 $ 18.07
Schedule of Stock-Based Compensation Expenses Recognized	Total stock-based compensation expense recognized was as follows (in thousands) Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Research and development $ 596 $ 369 $ 1,105 $ 729 General and administrative 616 371 1,098 647 Total $ 1,212 $ 740 $ 2,203 $ 1,376
Schedule of Stock Option Weighted-Average Assumptions	We estimated the fair value of each stock option using the Black-Scholes option-pricing model based on the date of grant of such stock option with the following assumptions: Three Months Ended Six Months Ended June 30, June 30, 2015 2014 2015 2014 Expected term (years) 5.5-6.1 5.3-6.1 5.5-6.1 5.3-6.1 Expected volatility 71 % 85 % 71-73% 85 % Risk-free interest rate 1.4-1.9 1.6-1.9% 1.4-1.9 1.6-1.9% Expected dividend yield 0 % 0 % 0 % 0 %

Description of Business - Addit

Description of Business - Additional Information (Detail) $ in Thousands	1 Months Ended	6 Months Ended
	Jan. 31, 2015USD ($)shares	Jun. 30, 2015Segment	Jun. 30, 2014USD ($)
Description Of Business [Line Items]
Number of operating segment | Segment		1
Proceeds from the sale of common stock to collaborative partner			$ 18,629
Underwritten Public Offering [Member]
Description Of Business [Line Items]
Issuance of stock, Shares | shares	3,829,994
Proceeds from the sale of common stock to collaborative partner	$ 78,700

Summary of Significant Accoun18

Summary of Significant Accounting Policies - Summary of Assets Recorded at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Money market funds [Member]
Assets
Assets	$ 9,842	$ 9,996
U.S. Treasury securities [Member]
Assets
Assets	188,310	130,786
U.S. government agency securities [Member]
Assets
Assets		3,001
Total cash equivalents and marketable securities [Member]
Assets
Assets	198,152	143,783
Level 1 [Member] | Money market funds [Member]
Assets
Assets	9,842	9,996
Level 1 [Member] | U.S. Treasury securities [Member]
Assets
Assets	188,310	130,786
Level 1 [Member] | Total cash equivalents and marketable securities [Member]
Assets
Assets	$ 198,152	140,782
Level 2 [Member] | U.S. government agency securities [Member]
Assets
Assets		3,001
Level 2 [Member] | Total cash equivalents and marketable securities [Member]
Assets
Assets		$ 3,001

Summary of Significant Accoun19

Summary of Significant Accounting Policies - Options and Restricted Stock Awards Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of diluted net (loss) income per share	2,604	2,141	2,635	2,177
Options and RSAs to purchase common stock [Member]
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Securities excluded from calculation of diluted net (loss) income per share	2,604	2,141	2,635	2,177

Cash Equivalents and Marketab20

Cash Equivalents and Marketable Securities - Summary of Cash Equivalents and Marketable Securities (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	$ 188,238	$ 133,786
Unrealized Gains	72	18
Unrealized Losses		(17)
Marketable securities	188,310	133,787
Money market funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	9,842	9,996
Marketable securities	9,842	9,996
U.S. Treasury securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	188,238	130,785
Unrealized Gains	72	18
Unrealized Losses		(17)
Marketable securities	188,310	130,786
Marketable securities including cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	198,080	143,782
Unrealized Gains	72	18
Unrealized Losses		(17)
Marketable securities	198,152	143,783
U.S. government agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis		3,001
Marketable securities		3,001
Cash equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost Basis	9,842	9,996
Marketable securities	$ 9,842	$ 9,996

Cash Equivalents and Marketab21

Cash Equivalents and Marketable Securities - Schedule of Amortized Cost and Estimated Fair Value of Available-for-Sale Securities by Contractual Maturity (Detail) $ in Thousands	Jun. 30, 2015USD ($)
Amortized Cost And Fair Value Debt Securities [Abstract]
Amortized Cost, In one year or less	$ 167,407
Amortized Cost, In one to two years	20,831
Total marketable securities, Amortized Cost	188,238
Estimated Fair Value, In one year or less	167,466
Estimated Fair Value, In one to two years	20,844
Total marketable securities, Estimated Fair Value	$ 188,310

Cash Equivalents and Marketab22

Cash Equivalents and Marketable Securities - Additional Information (Detail) - Jun. 30, 2015 - USD ($)	Total
Investments Debt And Equity Securities [Abstract]
Gross unrealized losses on marketable securities	$ 0
Sales of available-for-sale securities	$ 0

Equity Incentive Plans - Schedu

Equity Incentive Plans - Schedule of Option Activity under Stock Plans and Related Information (Detail) - Jun. 30, 2015 - $ / shares	Total
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Beginning balance	2,684,812
Number of Shares, Options granted	143,288
Number of Shares, Options exercised	(210,704)
Number of Shares, Options forfeited	(75,895)
Number of Shares, Options expired	(10,465)
Number of Shares, Ending balance	2,531,036
Number of Shares, Options exercisable	1,502,968
Weighted-Average Exercise Price Per Share, Options beginning balance	$ 7.85
Weighted-Average Exercise Price Per Share, Options granted	22.27
Weighted-Average Exercise Price Per Share, Options exercised	6.77
Weighted-Average Exercise Price Per Share, Options forfeited	8.76
Weighted-Average Exercise Price Per Share, Options expired	8.03
Weighted-Average Exercise Price Per Share, Options ending balance	8.73
Weighted-Average Exercise Price Per Share, Options exercisable	$ 6.78
Weighted-Average Remaining Contractual Terms, Options exercisable	5 years 9 months 15 days

Equity Incentive Plans - Sche24

Equity Incentive Plans - Schedule of Unvested Restricted Stock Awards (Detail) - 6 months ended Jun. 30, 2015 - Restricted Stock Awards [Member] - $ / shares	Total
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of Shares, Unvested, Beginning balance	24,000
Granted, Number of Shares	70,370
Forfeited, Number of Shares	(4,120)
Number of Shares, Unvested, Ending balance	90,250
Shares, Weighted-Average Grant-Date Fair Value balance at January 1, 2015	$ 12.18
Shares Granted, Weighted Average Grant Date Fair Value	20.06
Shares Forfeited, Weighted Average Grant Date Fair Value	20.06
Shares, Weighted-Average Grant-Date Fair Value balance at June 30, 2015	$ 18.07

Equity Incentive Plans - Additi

Equity Incentive Plans - Additional Information (Detail) - Jun. 30, 2015 - USD ($) $ in Millions	Total
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation expense related to nonvested employee and director stock options	$ 7.2
Unrecognized compensation expense expected to recognize, weighted-average period	2 years 6 months
2013 Omnibus Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares of common stock reserved for future issuance	4,102,609

Equity Incentive Plans - Sche26

Equity Incentive Plans - Schedule of Stock-Based Compensation Expenses Recognized (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense recognized	$ 1,212	$ 740	$ 2,203	$ 1,376
Research and development [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense recognized	596	369	1,105	729
General and administrative [Member]
Employee Service Share-based Compensation, Allocation of Recognized Period Costs [Line Items]
Stock-based compensation expense recognized	$ 616	$ 371	$ 1,098	$ 647

Equity Incentive Plans - Sche27

Equity Incentive Plans - Schedule of Stock Option Assumptions (Detail) - Options [Member]	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]
Expected volatility	71.00%	85.00%		85.00%
Expected dividend yield	0.00%	0.00%	0.00%	0.00%
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	5 years 6 months	5 years 3 months 18 days	5 years 6 months	5 years 3 months 18 days
Expected volatility			71.00%
Risk-free interest rate	1.40%	1.60%	1.40%	1.60%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected term (years)	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days	6 years 1 month 6 days
Expected volatility			73.00%
Risk-free interest rate	1.90%	1.90%	1.90%	1.90%

License Agreement - Additional

License Agreement - Additional Information (Detail) - Bluebird Bio, Inc [Member] - USD ($) $ in Millions	May. 31, 2015	Jun. 30, 2015
License Agreements Transactions [Line Items]
Proceeds from upfront fee	$ 1.5
License upfront fee receivable upon achievement of certain milestones	$ 131
Recognized revenue under license agreement		$ 1.5

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($)	Jun. 15, 2015	Jan. 02, 2015	Jun. 30, 2015	Jun. 30, 2015
Compensation And Retirement Disclosure [Abstract]
Eligible employees contribution percentage				100.00%
Defined contribution plan, employer matching contribution, percent of match		50.00%
Defined contribution plan, employer matching contribution, percent of employees' gross pay		4.00%
Defined contribution plan, employer matching contribution, amount		$ 6,000
Defined contribution plan, employer matching contribution, shares	13,720
Defined contribution plan, company matching contribution expense			$ 157,000	$ 336,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Jul. 31, 2015 - Inhibrx [Member] - Subsequent Events [Member] - USD ($) $ in Millions	Total
Subsequent Event [Line Items]
Upfront fee paid	$ 10
Collaboration Fee, Payable	$ 62.5
Milestone payment method description	Additionally, with respect to each licensed therapeutic product, we will be obligated to pay up to $62.5 million in specified development milestone payments and (i) if such licensed therapeutic product does not receive a Breakthrough Therapy Designation from the U.S. Food and Drug Administration, or FDA, up to $280.0 million in specified regulatory and commercial milestone payments, or (ii) if such licensed therapeutic product receives a Breakthrough Therapy Designation from the FDA, up to $380.0 million in specified regulatory and commercial milestone payments. Inhibrx is also eligible for low double-digit tiered royalties on future product sales. We may pay all or a portion of milestone payments for development and regulatory events in shares of our common stock, subject to certain limitations and conditions. We would be obligated to register for resale under the Securities Act of 1933, as amended, or the Securities Act, any such shares of our common stock.
Not Receives Breakthrough Therapy Designation [Member] | Maximum [Member]
Subsequent Event [Line Items]
Estimated regulatory and commercial milestone payments	$ 280
Receives Breakthrough Therapy Designation [Member] | Maximum [Member]
Subsequent Event [Line Items]
Estimated regulatory and commercial milestone payments	$ 380