OncoMed Pharmaceuticals 10-Q 2 Aug 17 2017 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2017	Aug. 01, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q2
Trading Symbol	OMED
Entity Registrant Name	OncoMed Pharmaceuticals Inc
Entity Central Index Key	1,302,573
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		37,630,443

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 31,940	$ 36,953
Short-term investments	97,828	147,620
Accounts receivable and other receivables	1,990	2,515
Prepaid and other current assets	3,220	2,495
Total current assets	134,978	189,583
Property and equipment, net	3,783	4,471
Other assets	584	1,428
Total assets	139,345	195,482
Current liabilities:
Accounts payable	2,115	4,890
Accrued liabilities	5,136	8,599
Accrued clinical liabilities	12,558	21,854
Current portion of deferred revenue	20,053	20,510
Total current liabilities	39,862	55,853
Deferred revenue, less current portion	149,347	159,373
Deferred rent, less current portion	3,548	2,917
Non-current income tax payable	375	367
Total liabilities	193,132	218,510
Stockholders’ equity (deficit):
Preferred stock, $0.001 par value; 5,000,000 shares authorized at June 30, 2017 and December 31, 2016; no shares issued and outstanding at June 30, 2017 and December 31, 2016
Common stock, $0.001 par value; 145,000,000 shares authorized at June 30, 2017 and December 31, 2016; 37,626,943 shares and 37,114,589 shares issued and outstanding at June 30, 2017 and December 31, 2016, respectively	37	37
Additional paid-in capital	396,683	389,620
Accumulated other comprehensive income	272	260
Accumulated deficit	(450,779)	(412,945)
Total stockholders’ equity (deficit)	(53,787)	(23,028)
Total liabilities and stockholders' equity (deficit)	$ 139,345	$ 195,482

Condensed Balance Sheets (Unau3

Condensed Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Jun. 30, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Preferred stock, par value	$ 0.001	$ 0.001
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.001	$ 0.001
Common stock, shares authorized	145,000,000	145,000,000
Common stock, shares issued	37,626,943	37,114,589
Common stock, shares outstanding	37,626,943	37,114,589

Condensed Statements of Operati

Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Revenue:
Collaboration revenue	$ 5,152	$ 5,348	$ 10,454	$ 10,696
Other revenue	1,043	1,317	1,954	2,319
Total revenue	6,195	6,665	12,408	13,015
Operating expenses:
Research and development	15,090	29,708	39,077	58,106
General and administrative	4,097	4,773	9,081	9,971
Restructuring charges	2,443		2,443
Total operating expenses	21,630	34,481	50,601	68,077
Loss from operations	(15,435)	(27,816)	(38,193)	(55,062)
Interest and other income, net	214	129	368	166
Loss before provision for income taxes	(15,221)	(27,687)	(37,825)	(54,896)
Provision for income taxes	4	4	8	6
Net loss	$ (15,225)	$ (27,691)	$ (37,833)	$ (54,902)
Net loss per common share, basic and diluted	$ (0.40)	$ (0.91)	$ (1.01)	$ (1.81)
Shares used to compute net loss per common share, basic and diluted	37,623,751	30,300,754	37,448,342	30,261,194

Condensed Statements of Compreh

Condensed Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (15,225)	$ (27,691)	$ (37,833)	$ (54,902)
Other comprehensive income:
Unrealized gain on available-for-sale securities, net of tax	4	27	12	142
Total comprehensive loss	$ (15,221)	$ (27,664)	$ (37,821)	$ (54,760)

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating activities
Net loss	$ (37,833)	$ (54,902)
Adjustments to reconcile net loss to net cash (used in) provided by operating activities:
Depreciation and amortization	861	880
Stock-based compensation	5,325	5,947
Changes in operating assets and liabilities:
Accounts receivable and other receivables	525	68,678
Prepaid and other current assets	(725)	743
Other assets	844	639
Accounts payable	(2,785)	(2,209)
Accrued liabilities	(3,154)	(2,207)
Accrued clinical liabilities	(9,296)	6,578
Deferred revenue	(10,483)	(10,696)
Deferred rent	631	(367)
Net cash (used in) provided by operating activities	(56,090)	13,084
Investing activities
Purchases of property and equipment	(464)	(698)
Purchases of short-term investments	(37,851)	(129,635)
Maturities of short-term investments	87,654	114,856
Net cash provided by (used in) investing activities	49,339	(15,477)
Financing activities
Proceeds from issuance of common stock related to the exercise of options and employee stock plan purchases	1,738	786
Net proceeds from issuance of common stock		934
Net cash provided by financing activities	1,738	1,720
Net decrease in cash and cash equivalents	(5,013)	(673)
Cash and cash equivalents at beginning of period	36,953	38,444
Cash and cash equivalents at end of period	31,940	$ 37,771
Supplemental cash flow information:
Accrued liabilities for purchase of property and equipment	$ 10

Organization

Organization	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization	1. Organization OncoMed Pharmaceuticals, Inc. (“OncoMed”, the “Company”, “us”, “we”, or “our”) is a clinical-stage biopharmaceutical company focused on discovering and developing novel therapeutics that address the fundamental biology driving cancer’s growth, resistance, recurrence and metastasis. The Company currently has three internally discovered therapeutic candidates in clinical development targeting cancer stem cell, or CSC, pathways and immuno-oncology targets. The Company recently filed an investigational new drug, or IND, application with the U.S. Food and Drug Administration, or FDA, for a fourth therapeutic candidate, GITRL‑Fc (OMP‑336B11), and plans to initiate clinical trials for GITRL‑Fc in the second half of 2017. The Company is also pursuing discovery of additional novel approaches to cancer treatment, including new immuno-oncology therapeutic candidates. The Company was incorporated in July 2004 in Delaware. The Company’s operations are based in Redwood City, California, and it operates in one segment.

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The Company’s financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim reporting. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or for any subsequent interim period. The condensed balance sheet data as of December 31, 2016 was derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016, filed with the Securities and Exchange Commission (the “SEC”) on March 9, 2017. There have been no material changes to our significant accounting policies as of and for the three and six months ended June 30, 2017, except for the inclusion of policies related to restructuring charges. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including, but not limited to, those related to revenue recognition, preclinical study and clinical trial accruals, fair value of assets and liabilities, restructuring charges, stock-based compensation and income taxes. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates. Restructuring Charges The Company recognizes a liability for exit and disposal activities when the liability is incurred. Restructuring charges consist of severance, other one-time benefits and other employee related charges. Liabilities for costs associated with a restructuring activity are measured at fair value and are recognized when the liability is incurred. One-time termination benefits are expensed at the date the Company notifies the employee, unless the employee must provide future service, in which case the benefits are expensed ratably over the future service period. The Company continually evaluates the adequacy of the remaining liabilities under its restructuring initiatives. Although the Company believes that these estimates accurately reflect the costs of the Company’s restructuring plan, actual results may differ and thereby require the Company to record an additional provision or reverse a portion of such a provision. Customer Concentration Customers whose revenue accounted for 10% or more of total revenues were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Bayer Pharma AG ("Bayer") 19% * 16% * Celgene Corporation ("Celgene") 81% 89% 83% 88% * Net Loss per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per common share is computed by dividing the net loss by the weighted-average number of common shares and common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, potentially dilutive securities consisting of common stock subject to repurchase, stock options and restricted stock units are considered to be common stock equivalents and were excluded in the calculation of diluted net loss per common share because their effect would be anti-dilutive for all periods presented. Newly Adopted and Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers: Topic 606 08, Revenue from Contracts with Customers: Principal versus Agent Considerations , ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing , ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients to provide supplemental adoption guidance and clarification to ASU 2014-09 and ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers , respectively. The effective date for these new standards is the same as the effective date for ASU 2014-09, within the same transition requirements. The Company will adopt ASU 2014-09 in the first quarter of 2018 using the modified retrospective method. The adoption of ASU 2014-09 may have a material effect on the Company’s financial statements. To date, the Company has derived its revenues from collaboration agreements. The consideration that the Company is eligible to receive under these agreements includes upfront payments, research and development funding, and milestone payments. Each collaboration agreement is unique and will need to be assessed separately under the five-step process under the new standard. The Company has started its preliminary assessment of its active collaboration agreements. The Company expects that its evaluation of the accounting for collaboration agreements under the new revenue standard could identify material changes from the current accounting treatment. ASU 2014-09 differs from the current accounting standard in many respects, such as in the accounting for variable consideration, including milestone payments. Under the Company’s current accounting policy, milestone revenue is recognized using the milestone method specified in ASC 605-28, which generally results in the recognition of the milestone payment as revenue in the period that the milestone is achieved. However, under ASU 2014-09, it is possible to start to recognize milestone revenue before the milestone is achieved, subject to management’s assessment that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. In addition, ASC 605-28 includes a presumption that revenue from up-front non-refundable fees would be recognized ratably over the performance period, unless another attribution method was determined to more closely approximate the delivery of the goods or services to the customer. ASU 2014-09 does not have a presumption that entities would default to a ratable attribution approach and will require entities to determine an appropriate attribution method using either output or input methods. As such, the amount and timing of revenue recognition for the Company’s collaboration agreements may change under ASU 2014-09. In February 2016, the FASB issued ASU 2016-02, Leases accounting In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting

Cash, Cash Equivalents and Inve

Cash, Cash Equivalents and Investments	6 Months Ended
	Jun. 30, 2017
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents and Investments	3. Cash, Cash Equivalents and Investments The fair value of securities at June 30, 2017 and December 31, 2016, were as follows (in thousands): June 30, 2017 Amortized Gross Unrealized Fair Cost Gains Losses Value Money market funds $ 117 $ — $ — $ 117 U.S. treasury bills 97,556 272 — 97,828 Total available-for-sale securities $ 97,673 $ 272 $ — $ 97,945 Classified as: Cash equivalents $ 117 Short-term investments 97,828 Total cash equivalents and investments $ 97,945 As of June 30, 2017, the Company had a total of $129.8 million in cash, cash equivalents and short-term investments, which includes $31.9 million in cash and cash equivalents and $97.8 million short-term investments. December 31, 2016 Amortized Gross Unrealized Fair Cost Gains Losses Value U.S. treasury bills $ 147,360 $ 260 $ — $ 147,620 Total available-for-sale securities $ 147,360 $ 260 $ — $ 147,620 Classified as: Short-term investments $ 147,620 As of December 31, 2016, the Company had a total of $184.6 million in cash and short-term investments, which includes $37.0 million in cash and $147.6 million in short-term investments. All available-for-sale securities held as of June 30, 2017 and December 31, 2016 had contractual maturities of less than one year. There have been no significant realized gains or losses on available-for-sale securities for the periods presented.

Fair Value Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements	4. Fair Value Measurements The Company records its financial assets and liabilities at fair value. The accounting guidance for fair value provides a framework for measuring fair value, clarifies the definition of fair value, and expands disclosures regarding fair value measurements. Fair value is defined as the price that would be received to sell an asset or paid to transfer a liability (an exit price) in an orderly transaction between market participants at the reporting date. The Company applies the following hierarchy for disclosure of the inputs used to measure fair value, which prioritizes the inputs used into three broad levels as follows: • Level 1: Inputs which include quoted prices in active markets for identical assets and liabilities. • Level 2: Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices 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. • 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. The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): June 30, 2017 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 117 $ — $ — $ 117 U.S. treasury bills — 97,828 — 97,828 Total $ 117 $ 97,828 $ — $ 97,945 December 31, 2016 Level 1 Level 2 Level 3 Total Assets: U.S. treasury bills $ — $ 147,620 $ — $ 147,620 Total $ — $ 147,620 $ — $ 147,620 Where quoted prices are available in an active market, securities are classified as Level 1. The Company classifies money market funds as Level 1. When quoted market prices are not available for the specific security, then the Company estimates fair value by using benchmark yields, reported trades, broker/dealer quotes, and issuer spreads. The Company classifies U.S. Treasury securities as Level 2 .

Collaborations

Collaborations	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Collaborations	5. Collaborations Summary of Collaboration Related Revenue The Company has recognized the following revenues from its collaboration agreements during the three and six months ended June 30, 2017 and 2016 (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 GlaxoSmithKline (“GSK”): Recognition of upfront payments $ — $ 150 $ 150 $ 300 Other revenue — 150 3 617 GSK total — 300 153 917 Bayer: Recognition of upfront payments 139 185 278 370 Other revenue 1,036 254 1,734 307 Bayer total 1,175 439 2,012 677 Celgene: Recognition of upfront payments 5,013 5,013 10,026 10,026 Other revenue 7 913 217 1,395 Celgene total 5,020 5,926 10,243 11,421 Total collaboration related revenue $ 6,195 $ 6,665 $ 12,408 $ 13,015 GSK Strategic Alliance On July 7, 2017, the Company received a letter, dated June 30, 2017, from GSK indicating that GSK was terminating the Company’s collaboration agreement with GSK in its entirety. Such termination will become effective on the date that is 120 days after the date of the letter. As a result of such termination, as of October 28, 2017, the Company will retain worldwide rights to tarextumab (anti-Notch2/3, OMP-59R5). The Company will no longer be eligible to receive up to $344.5 million in aggregate development milestone payments and contingent consideration with respect to tarextumab, including a $25.0 million opt-in payment. The Company has decided to discontinue its tarextumab program, as well as its brontictuzumab (anti-Notch1, OMP-52M51) program, which was also previously subject to the collaboration agreement with GSK, and will not conduct any further development activities relating to either program. Bayer Strategic Alliance On April 7, 2017, Bayer notified the Company of its decision not to exercise its option to license vantictumab and ipafricept and of its termination of all Wnt pathway biologic programs under the Company’s collaboration with Bayer, including vantictumab and ipafricept. As a result, effective June 16, 2017, the Company retained worldwide rights to develop and commercialize vantictumab and ipafricept. The Company is no longer eligible to receive any payments under its collaboration with Bayer with respect to biologic therapeutic candidates, including vantictumab and ipafricept. With respect to Wnt pathway small molecule candidates, the Company remains eligible to receive up to $22.0 million in certain development milestone payments as well as contingent consideration payments of up to $50.0 million for the achievement of certain development and regulatory events and up to $140.0 million upon the achievement of specified future product sales. As all such contingent consideration is based solely on the performance of Bayer, the Company would recognize the contingent payments upon receipt immediately as collaboration revenue if the Company had no further performance obligations under the agreement with Bayer. Celgene Strategic Alliance As of June 30, 2017, the Company is eligible to receive in its collaboration with Celgene up to $15.0 million in future development milestones across all biologic programs, prior to the point that Celgene exercises its options. The Company is also eligible to receive up to $240.0 million of contingent consideration if Celgene exercises all its options for the biologic and small molecule therapeutic programs. Following Celgene’s exercise of its option for a biologic therapeutic program, the Company will have co-development and co-commercialization rights for five of the six biologic therapeutic programs in the U.S. Celgene will be responsible for all further development and commercialization following the exercise of the options for specified programs. For programs subject to the Company’s co-development and co-commercialization rights, the Company will be responsible for one-third and Celgene will be responsible for two-thirds of worldwide development costs, and the Company and Celgene will share 50% of all product profits and losses in the U.S. Outside the U.S., Celgene will have exclusive development and commercialization rights for such programs, with the Company eligible to receive milestones and tiered royalties on product sales. With respect to one of the six biologic therapeutic programs, and any of the other biologic therapeutic programs if the Company elects not to co-develop and co-commercialize products arising from such program, Celgene will have exclusive development and commercialization rights worldwide, with the Company eligible to receive milestones and tiered royalties on worldwide product sales. If Celgene successfully develops and commercializes all of the product candidates, the Company could receive additional contingent consideration of up to $2.8 billion for the achievement of post-option exercise development, regulatory events and sales milestones (up to $2.7 billion for biologics and $95.0 million for small molecules). As all contingent consideration is based solely on the performance of Celgene, the Company would recognize the contingent payments upon receipt immediately as collaboration revenue if the Company had no further performance obligations under the agreement with Celgene. On April 10, 2017, the Company announced that the Phase II “YOSEMITE” clinical trial of demcizumab (anti-DLL4, OMP-21M18) in combination with Abraxane ® Celgene notified the Company on June 29, 2017 that it does not intend to exercise its option for demcizumab, and the Company has decided to discontinue its demcizumab program entirely. Of the potential payments the Company is eligible to receive in its collaboration with Celgene, summarized above, demcizumab accounts for $70.0 million of contingent consideration for Celgene’s exercise of its option and up to $721.0 million in aggregate payments for the achievement of development, regulatory, and commercial milestones.

Stockholder_s Equity

Stockholder’s Equity	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Stockholder’s Equity	6. Stockholder’s Equity Equity Incentive Plans As of June 30, 2017, a total of 5,694,538 shares of common stock have been authorized under the 2013 Equity Incentive Award Plan (the “2013 Plan”), including the additional 1,484,583 shares of common stock that became available on January 1, 2017 for future issuance under the 2013 Plan as a result of an annual automatic increase provision in the 2013 Plan. As of June 30, 2017, a total of 4,750,825 shares are subject to options and restricted stock units (“RSUs”) outstanding under the 2013 Plan. There are 1,474,502 shares subject to options outstanding under the 2004 Stock Incentive Plan (the “2004 Plan”) as of June 30, 2017, which will become available for issuance under the 2013 Plan to the extent the options are forfeited or lapse unexercised without issuance of such shares under the 2004 Plan. The following table summarizes the Company’s stock option and RSU award activity under the 2004 Plan and 2013 Plan including grants to nonemployees during the six months ended June 30, 2017 (in thousands): Shares Available for Grant Options and of Options and Awards Awards Outstanding Balance at December 31, 2016 971 4,900 Additional shares authorized 1,485 — RSUs awarded (532 ) 532 Options granted (1,753 ) 1,753 Options exercised — (269 ) RSUs vested — (184 ) Options forfeited 367 (367 ) RSUs forfeited 140 (140 ) Balance at June 30, 2017 678 6,225 The weighted-average grant date estimated fair value of options granted during the six months ended June 30, 2017 was $3.96 per share. Employee Stock Purchase Plan As of June 30, 2017, a total of 1,543,620 shares of common stock have been authorized and 1,235,717 shares of common stock are available for future issuance under the Company’s Employee Stock Purchase Plan (the “ESPP”). This authorized number includes the additional 350,000 shares of common stock that became available for future issuance under the ESPP as of January 1, 2017 as a result of an annual automatic increase provision in the ESPP. The ESPP allows eligible employees to purchase shares of the Company’s common stock at a discount through payroll deductions of up to 15% of their eligible compensation, subject to any plan limitations. The ESPP provides for six-month offering periods, and at the end of each offering period, employees are able to purchase shares at 85% of the lower of the fair market value of the Company’s common stock on the first trading day of the offering period or on the last day of the offering period. During the six months ended June 30, 2017, the Company issued 59,135 shares under the ESPP. Restricted Stock Units In March 2014, the Company awarded 293,980 RSUs under the 2013 Plan. The RSUs fully vested on March 31, 2017. Each vested RSU represents the right to receive one share of common stock. The Company recognized stock-based compensation expense related to these RSUs of $0.4 million for the six months ended June 30, 2017. Stock-Based Compensation Employee stock-based compensation expense was calculated based on awards expected to vest and has been reduced for estimated forfeitures. Forfeitures are estimated at the time of grant and revised, if necessary, in subsequent periods if actual forfeitures are expected to differ from those estimates. Stock-based compensation expense recognized was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Research and development $ 1,132 $ 1,598 $ 2,549 $ 3,241 General and administrative 1,064 1,354 2,770 2,706 Restructuring charges 6 — 6 — Total $ 2,202 $ 2,952 $ 5,325 $ 5,947 As of June 30, 2017, the Company had $14.1 million, $3.9 million and $0.1 million of unrecognized stock-based compensation expense related to stock options, RSUs and ESPP shares, respectively, which are expected to be recognized over an estimated weighted-average period of 3.1 years, 1.4 years and 0.2 years, respectively. Fair Value Disclosures The fair value of stock options granted under the 2013 Plan and purchases under the Company’s ESPP were estimated at grant date using the Black-Scholes option-pricing model. The fair value of stock-based awards was estimated using the following weighted average assumptions for the three and six months ended June 30, 2017 and 2016: Three Months Ended June 30, Six Months Ended June 30, Stock Option Plan: 2017 2016 2017 2016 Weighted-average volatility 77.2% 71.6% 75.3% 67.8% Weighted-average expected term (years) 6.2 6.2 6.2 6.2 Risk-free interest rate 2.1% 1.5% 2.2% 1.6% Expected dividend yield — — — — Three Months Ended June 30, Six Months Ended June 30, ESPP 2017 2016 2017 2016 Weighted-average volatility 54.0% 104.5% 63.9% 75.0% Weighted-average expected term (years) 0.5 0.5 0.5 0.5 Risk-free interest rate 0.5% 0.5% 0.5% 0.4% Expected dividend yield — — — —

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes During the three and six months ended June 30, 2017, the Company recorded an income tax provision of $4,000 and $8,000, respectively, related to discrete items resulting from interest on prior years’ uncertain tax positions. The Company’s deferred tax assets continue to be fully offset by a valuation allowance.

Net Loss per Common Share

Net Loss per Common Share	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Net Loss per Common Share	8. Net Loss per Common Share The following outstanding common stock equivalents were excluded from the computation of diluted net loss per common share for the periods presented because including them would have been anti-dilutive (in thousands): As of June 30, 2017 2016 Options to purchase common stock 5,441 4,541 RSUs 784 212 6,225 4,753

Restructuring Charges

Restructuring Charges	6 Months Ended
	Jun. 30, 2017
Restructuring And Related Activities [Abstract]
Restructuring Charges	9. Restructuring Charges On April 24, 2017, the Company’s Board of Directors approved a restructuring plan to reduce operating costs and better align its workforce with the needs of its business following the Company’s recent announcements that its Phase II “YOSEMITE” clinical trial of demcizumab (anti-DLL4, OMP-21M18) in combination with Abraxane ® ® Under The following table provides a summary of restructuring activity during the six months ended June 30, 2017 (in thousands): Employee Severance and Other Costs Balance at January 1, 2017 $ — Costs incurred 2,443 Less cash payments (2,110 ) Less non-cash charges (6 ) Balance at June 30, 2017 $ 327

Summary of Significant Accoun16

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company’s financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim reporting. These financial statements have been prepared on the same basis as the Company’s annual financial statements and, in the opinion of management, reflect all adjustments, consisting only of normal recurring adjustments that are necessary for a fair statement of the Company’s financial information. These interim results are not necessarily indicative of the results to be expected for the year ending December 31, 2017 or for any subsequent interim period. The condensed balance sheet data as of December 31, 2016 was derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. The accompanying condensed financial statements and related financial information should be read in conjunction with the audited financial statements and the related notes thereto contained in the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2016, filed with the Securities and Exchange Commission (the “SEC”) on March 9, 2017. There have been no material changes to our significant accounting policies as of and for the three and six months ended June 30, 2017, except for the inclusion of policies related to restructuring charges.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and judgments that affect the amounts reported in the financial statements and accompanying notes. On an ongoing basis, management evaluates its estimates, including, but not limited to, those related to revenue recognition, preclinical study and clinical trial accruals, fair value of assets and liabilities, restructuring charges, stock-based compensation and income taxes. Management bases its estimates on historical experience and on various other market-specific and relevant assumptions that management believes to be reasonable under the circumstances. Actual results may differ from those estimates.
Restructuring Charges	Restructuring Charges The Company recognizes a liability for exit and disposal activities when the liability is incurred. Restructuring charges consist of severance, other one-time benefits and other employee related charges. Liabilities for costs associated with a restructuring activity are measured at fair value and are recognized when the liability is incurred. One-time termination benefits are expensed at the date the Company notifies the employee, unless the employee must provide future service, in which case the benefits are expensed ratably over the future service period. The Company continually evaluates the adequacy of the remaining liabilities under its restructuring initiatives. Although the Company believes that these estimates accurately reflect the costs of the Company’s restructuring plan, actual results may differ and thereby require the Company to record an additional provision or reverse a portion of such a provision.
Customer Concentration	Customer Concentration Customers whose revenue accounted for 10% or more of total revenues were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Bayer Pharma AG ("Bayer") 19% * 16% * Celgene Corporation ("Celgene") 81% 89% 83% 88% *
Net Loss per Common Share	Net Loss per Common Share Basic net loss per common share is calculated by dividing the net loss by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net loss per common share is computed by dividing the net loss by the weighted-average number of common shares and common share equivalents outstanding for the period determined using the treasury-stock method. For purposes of this calculation, potentially dilutive securities consisting of common stock subject to repurchase, stock options and restricted stock units are considered to be common stock equivalents and were excluded in the calculation of diluted net loss per common share because their effect would be anti-dilutive for all periods presented.
Newly Adopted and Recent Accounting Pronouncements	Newly Adopted and Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, 2014-09, Revenue from Contracts with Customers: Topic 606 08, Revenue from Contracts with Customers: Principal versus Agent Considerations , ASU 2016-10, Revenue from Contracts with Customers: Identifying Performance Obligations and Licensing , ASU 2016-12, Revenue from Contracts with Customers: Narrow-Scope Improvements and Practical Expedients to provide supplemental adoption guidance and clarification to ASU 2014-09 and ASU 2016-20, Technical Corrections and Improvements to Topic 606, Revenue from Contracts with Customers , respectively. The effective date for these new standards is the same as the effective date for ASU 2014-09, within the same transition requirements. The Company will adopt ASU 2014-09 in the first quarter of 2018 using the modified retrospective method. The adoption of ASU 2014-09 may have a material effect on the Company’s financial statements. To date, the Company has derived its revenues from collaboration agreements. The consideration that the Company is eligible to receive under these agreements includes upfront payments, research and development funding, and milestone payments. Each collaboration agreement is unique and will need to be assessed separately under the five-step process under the new standard. The Company has started its preliminary assessment of its active collaboration agreements. The Company expects that its evaluation of the accounting for collaboration agreements under the new revenue standard could identify material changes from the current accounting treatment. ASU 2014-09 differs from the current accounting standard in many respects, such as in the accounting for variable consideration, including milestone payments. Under the Company’s current accounting policy, milestone revenue is recognized using the milestone method specified in ASC 605-28, which generally results in the recognition of the milestone payment as revenue in the period that the milestone is achieved. However, under ASU 2014-09, it is possible to start to recognize milestone revenue before the milestone is achieved, subject to management’s assessment that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur when the uncertainty associated with the variable consideration is subsequently resolved. In addition, ASC 605-28 includes a presumption that revenue from up-front non-refundable fees would be recognized ratably over the performance period, unless another attribution method was determined to more closely approximate the delivery of the goods or services to the customer. ASU 2014-09 does not have a presumption that entities would default to a ratable attribution approach and will require entities to determine an appropriate attribution method using either output or input methods. As such, the amount and timing of revenue recognition for the Company’s collaboration agreements may change under ASU 2014-09. In February 2016, the FASB issued ASU 2016-02, Leases accounting In March 2016, the FASB issued ASU No. 2016-09, Compensation—Stock Compensation (Topic 718): Improvements to Employee Share-Based Payment Accounting

Summary of Significant Accoun17

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2017
Accounting Policies [Abstract]
Schedule of Customer Concentration of Revenue	Customers whose revenue accounted for 10% or more of total revenues were as follows: Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Bayer Pharma AG ("Bayer") 19% * 16% * Celgene Corporation ("Celgene") 81% 89% 83% 88% *

Cash, Cash Equivalents and In18

Cash, Cash Equivalents and Investments (Tables)	6 Months Ended
	Jun. 30, 2017
Cash And Cash Equivalents [Abstract]
Schedule of Fair Value of Securities, Not Including Cash	The fair value of securities at June 30, 2017 and December 31, 2016, were as follows (in thousands): June 30, 2017 Amortized Gross Unrealized Fair Cost Gains Losses Value Money market funds $ 117 $ — $ — $ 117 U.S. treasury bills 97,556 272 — 97,828 Total available-for-sale securities $ 97,673 $ 272 $ — $ 97,945 Classified as: Cash equivalents $ 117 Short-term investments 97,828 Total cash equivalents and investments $ 97,945 As of June 30, 2017, the Company had a total of $129.8 million in cash, cash equivalents and short-term investments, which includes $31.9 million in cash and cash equivalents and $97.8 million short-term investments. December 31, 2016 Amortized Gross Unrealized Fair Cost Gains Losses Value U.S. treasury bills $ 147,360 $ 260 $ — $ 147,620 Total available-for-sale securities $ 147,360 $ 260 $ — $ 147,620 Classified as: Short-term investments $ 147,620

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2017
Fair Value Disclosures [Abstract]
Summary of Company's Financial Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis	The Company’s financial assets and liabilities subject to fair value measurements on a recurring basis and the level of inputs used in such measurements were as follows (in thousands): June 30, 2017 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 117 $ — $ — $ 117 U.S. treasury bills — 97,828 — 97,828 Total $ 117 $ 97,828 $ — $ 97,945 December 31, 2016 Level 1 Level 2 Level 3 Total Assets: U.S. treasury bills $ — $ 147,620 $ — $ 147,620 Total $ — $ 147,620 $ — $ 147,620

Collaborations (Tables)

Collaborations (Tables)	6 Months Ended
	Jun. 30, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Company Recognized Revenues from Collaboration Agreements	The Company has recognized the following revenues from its collaboration agreements during the three and six months ended June 30, 2017 and 2016 (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 GlaxoSmithKline (“GSK”): Recognition of upfront payments $ — $ 150 $ 150 $ 300 Other revenue — 150 3 617 GSK total — 300 153 917 Bayer: Recognition of upfront payments 139 185 278 370 Other revenue 1,036 254 1,734 307 Bayer total 1,175 439 2,012 677 Celgene: Recognition of upfront payments 5,013 5,013 10,026 10,026 Other revenue 7 913 217 1,395 Celgene total 5,020 5,926 10,243 11,421 Total collaboration related revenue $ 6,195 $ 6,665 $ 12,408 $ 13,015

Stockholder_s Equity (Tables)

Stockholder’s Equity (Tables)	6 Months Ended
	Jun. 30, 2017
Equity [Abstract]
Summary of Stock Option and RSU Award Activity under 2004 Plan and 2013 Stock Plan	The following table summarizes the Company’s stock option and RSU award activity under the 2004 Plan and 2013 Plan including grants to nonemployees during the six months ended June 30, 2017 (in thousands): Shares Available for Grant Options and of Options and Awards Awards Outstanding Balance at December 31, 2016 971 4,900 Additional shares authorized 1,485 — RSUs awarded (532 ) 532 Options granted (1,753 ) 1,753 Options exercised — (269 ) RSUs vested — (184 ) Options forfeited 367 (367 ) RSUs forfeited 140 (140 ) Balance at June 30, 2017 678 6,225
Schedule of Stock-Based Compensation Expense	Stock-based compensation expense recognized was as follows (in thousands): Three Months Ended June 30, Six Months Ended June 30, 2017 2016 2017 2016 Research and development $ 1,132 $ 1,598 $ 2,549 $ 3,241 General and administrative 1,064 1,354 2,770 2,706 Restructuring charges 6 — 6 — Total $ 2,202 $ 2,952 $ 5,325 $ 5,947
Schedule of Weighted Average Assumptions Used under Black-Scholes Option-Pricing Model to Estimate Fair Value of Stock Options Granted Under 2013 Plan	The fair value of stock-based awards was estimated using the following weighted average assumptions for the three and six months ended June 30, 2017 and 2016: Three Months Ended June 30, Six Months Ended June 30, Stock Option Plan: 2017 2016 2017 2016 Weighted-average volatility 77.2% 71.6% 75.3% 67.8% Weighted-average expected term (years) 6.2 6.2 6.2 6.2 Risk-free interest rate 2.1% 1.5% 2.2% 1.6% Expected dividend yield — — — —
Schedule of Weighted Average Assumptions Used under Black-Scholes Option-Pricing Model to Estimate Fair Value of Company's ESPP at Grant Date	Three Months Ended June 30, Six Months Ended June 30, ESPP 2017 2016 2017 2016 Weighted-average volatility 54.0% 104.5% 63.9% 75.0% Weighted-average expected term (years) 0.5 0.5 0.5 0.5 Risk-free interest rate 0.5% 0.5% 0.5% 0.4% Expected dividend yield — — — —

Net Loss per Common Share (Tabl

Net Loss per Common Share (Tables)	6 Months Ended
	Jun. 30, 2017
Earnings Per Share [Abstract]
Outstanding Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Common Share	The following outstanding common stock equivalents were excluded from the computation of diluted net loss per common share for the periods presented because including them would have been anti-dilutive (in thousands): As of June 30, 2017 2016 Options to purchase common stock 5,441 4,541 RSUs 784 212 6,225 4,753

Restructuring Charges (Tables)

Restructuring Charges (Tables)	6 Months Ended
	Jun. 30, 2017
Restructuring And Related Activities [Abstract]
Summary of Restructuring Activity	The following table provides a summary of restructuring activity during the six months ended June 30, 2017 (in thousands): Employee Severance and Other Costs Balance at January 1, 2017 $ — Costs incurred 2,443 Less cash payments (2,110 ) Less non-cash charges (6 ) Balance at June 30, 2017 $ 327

Organization - Additional Infor

Organization - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2017Segment
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating segment	1
Incorporation date	Jul. 31, 2004

Summary of Significant Accoun25

Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2017USD ($)
ASU 2016-09 [Member] | Increase in Deferred Tax Asset [Member]
Summary Of Significant Accounting Policies [Line Items]
Effect of change in deferred tax asset	$ 3.9
Minimum [Member] | Revenue [Member] | Customer Concentration [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage of revenue represented by major customers	10.00%

Summary of Significant Accoun26

Summary of Significant Accounting Policies - Schedule of Customer Concentration of Revenue (Detail) - Revenue [Member] - Customer Concentration [Member] - Collaborative Arrangement [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Bayer [Member]
Concentration Risk [Line Items]
Collaborative research and development revenue, Percentage	19.00%		16.00%
Celgene [Member]
Concentration Risk [Line Items]
Collaborative research and development revenue, Percentage	81.00%	89.00%	83.00%	88.00%

Summary of Significant Accoun27

Summary of Significant Accounting Policies - Schedule of Customer Concentration of Revenue (Parenthetical) (Detail)	6 Months Ended
	Jun. 30, 2017
Minimum [Member] | Revenue [Member] | Customer Concentration [Member]
Concentration Risk [Line Items]
Concentration risk percentage of revenue represented by major customers	10.00%

Cash, Cash Equivalents and In28

Cash, Cash Equivalents and Investments - Schedule of Fair Value of Securities, Not Including Cash (Detail) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 97,673	$ 147,360
Gross Unrealized Gains	272	260
Fair Value	97,945	147,620
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	117
Fair Value	117
U.S. Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	97,556	147,360
Gross Unrealized Gains	272	260
Fair Value	97,828	147,620
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	117
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 97,828	$ 147,620

Cash, Cash Equivalents and In29

Cash, Cash Equivalents and Investments - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Schedule of Available-for-sale Securities [Line Items]
Total cash, cash equivalents, and short-term investments	$ 129,800,000	$ 184,600,000
Cash and cash equivalents	31,940,000	36,953,000	$ 37,771,000	$ 38,444,000
Short-term investments	97,828,000	147,620,000
Realized gains or losses on available-for-sale securities	$ 0	$ 0
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Available for sale securities, contractual maturity period	1 year	1 year

Fair Value Measurements - Summa

Fair Value Measurements - Summary of Company's Financial Assets and Liabilities Subject to Fair Value Measurements on Recurring Basis (Detail) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Assets:
Assets fair value disclosure	$ 97,945	$ 147,620
Level 1 [Member]
Assets:
Assets fair value disclosure	117
Level 2 [Member]
Assets:
Assets fair value disclosure	97,828	147,620
Money Market Funds [Member]
Assets:
Assets fair value disclosure	117
Money Market Funds [Member] | Level 1 [Member]
Assets:
Assets fair value disclosure	117
U.S. Treasury Bills [Member]
Assets:
Assets fair value disclosure	97,828	147,620
U.S. Treasury Bills [Member] | Level 2 [Member]
Assets:
Assets fair value disclosure	$ 97,828	$ 147,620

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail)	Jun. 30, 2017USD ($)
Fair Value Disclosures [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	$ 0
Fair Value, Assets, Level 2 to Level 1 Transfers, Amount	0
Fair Value, Liabilities, Level 1 to Level 2 Transfers, Amount	0
Fair Value, Liabilities, Level 2 to Level 1 Transfers, Amount	$ 0

Collaborations - Company Recogn

Collaborations - Company Recognized Revenues from Collaboration Agreements (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	$ 5,152	$ 5,348	$ 10,454	$ 10,696
Collaborative Arrangement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	6,195	6,665	12,408	13,015
Collaborative Arrangement [Member] | GlaxoSmithKline [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue		300	153	917
Collaborative Arrangement [Member] | GlaxoSmithKline [Member] | Recognition of Upfront Payments [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue		150	150	300
Collaborative Arrangement [Member] | GlaxoSmithKline [Member] | Other Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue		150	3	617
Collaborative Arrangement [Member] | Bayer [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	1,175	439	2,012	677
Collaborative Arrangement [Member] | Bayer [Member] | Recognition of Upfront Payments [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	139	185	278	370
Collaborative Arrangement [Member] | Bayer [Member] | Other Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	1,036	254	1,734	307
Collaborative Arrangement [Member] | Celgene [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	5,020	5,926	10,243	11,421
Collaborative Arrangement [Member] | Celgene [Member] | Recognition of Upfront Payments [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	5,013	5,013	10,026	10,026
Collaborative Arrangement [Member] | Celgene [Member] | Other Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	$ 7	$ 913	$ 217	$ 1,395

Collaborations - GlaxoSmithKlin

Collaborations - GlaxoSmithKline Strategic Alliance - Additional Information (Detail) - Collaborative Arrangement [Member] - GlaxoSmithKline [Member] - Tarextumab [Member] - Subsequent Event [Member] $ in Millions	Jul. 07, 2017USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Effective date of termination	Oct. 28, 2017
Milestone payments under collaboration arrangement lapse due to termination of agreement	$ 344.5
Opt-in payment lapse due to termination of agreement	$ 25

Collaborations - Bayer Strategi

Collaborations - Bayer Strategic Alliance - Additional Information (Detail) - Collaborative Arrangement [Member] - Bayer [Member] - Small Molecules [Member] $ in Millions	Jun. 16, 2017USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future development milestone payments	$ 22
Contingent consideration payments for regulatory events	50
Achievement of Specified Future Product Sales [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent consideration payments for regulatory events	$ 140

Collaborations - Celgene Strate

Collaborations - Celgene Strategic Alliance - Additional Information (Detail) - Collaborative Arrangement [Member]	Jun. 29, 2017USD ($)	Jun. 30, 2017USD ($)Program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Percentage of sharing development cost		33.33%
Profits and losses sharing percentage		50.00%
Celgene [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional contingent consideration for regulatory events		$ 2,800,000,000
Number of biological program for which company can enter into co-commercialization and co-development agreements | Program		5
Number of biological program for which company not elects to co-develop and co-commercialize products | Program		1
Number of biologic programs | Program		6
Percentage of sharing development cost		66.66%
Profits and losses sharing percentage		50.00%
Celgene [Member] | Biologic Product [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future development milestone payments		$ 15,000,000
Celgene [Member] | Biologic and Small Molecule Therapeutic Programs [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future development milestone payments		240,000,000
Celgene [Member] | Small Molecules [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional contingent consideration for regulatory events		95,000,000
Celgene [Member] | Demcizumab [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Potential payment receivable for collaboration arrangement	$ 70,000,000
Milestone payments under collaboration arrangement lapse due to non exercise of option	$ 721,000,000
Maximum [Member] | Celgene [Member] | Biologic Product [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Additional contingent consideration for regulatory events		$ 2,700,000,000

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2014	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jan. 01, 2017	Dec. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock subject to options outstanding		6,225,000		6,225,000			4,900,000
Weighted-average grant-date fair value, granted				$ 3.96
Stock-based compensation expense		$ 2,202	$ 2,952	$ 5,325	$ 5,947
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Restricted stock units awarded	293,980			532,000
Right to receive number of shares of common stock upon vesting of each RSU	1
Restricted stock units vesting date				Mar. 31, 2017
Stock-based compensation expense				$ 400
Unrecognized stock-based compensation expense		3,900		$ 3,900
Estimated weighted-average period				1 year 4 months 24 days
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense		$ 14,100		$ 14,100
Estimated weighted-average period				3 years 1 month 6 days
Employees Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized		1,543,620		1,543,620
Common stock available for future issuance under plan		1,235,717		1,235,717		350,000
Common stock purchased at discount through payroll deductions				15.00%
Employee stock purchase plan, offering period				6 months
Shares purchased lower of the fair market value				85.00%
Common stock issued to employees under ESPP				59,135
Unrecognized stock-based compensation expense		$ 100		$ 100
Estimated weighted-average period				2 months 12 days
2013 Equity Incentive Award Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized		5,694,538		5,694,538
Common stock available for future issuance under plan						1,484,583
Common stock subject to options and restricted stock units outstanding		4,750,825		4,750,825
2004 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock subject to options outstanding		1,474,502		1,474,502

Stockholder's Equity - Summary

Stockholder's Equity - Summary of Stock Option and RSU Award Activity under 2004 Plan and 2013 Stock Plan (Detail) - shares	1 Months Ended	6 Months Ended
	Mar. 31, 2014	Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Beginning Balance		971,000
Shares Available for Grant, Additional Options authorized		1,485,000
Shares Available for Grant, Options granted		(1,753,000)
Shares Available for Grant, Options exercised		0
Shares Available for Grant, Options forfeited		367,000
Shares Available for Grant, Ending Balance		678,000
Options Outstanding, Beginning Balance		4,900,000
Options and Awards Outstanding, Additional Options authorized		0
Options Outstanding, Options granted		1,753,000
Options Outstanding, Options exercised		(269,000)
Options Outstanding, Options forfeited		(367,000)
Options Outstanding, Ending Balance		6,225,000
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant of Options and Awards, RSUs awarded	(293,980)	(532,000)
Shares Available for Grant of Options and Awards, RSU vested		0
Shares Available for Grant of Options and Awards, RSUs forfeited		140,000
Options and Awards Outstanding, RSUs awarded		532,000
Options and Awards Outstanding, RSU vested		(184,000)
Options and Awards Outstanding, RSUs forfeited		(140,000)

Stockholder's Equity - Schedule

Stockholder's Equity - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 2,202	$ 2,952	$ 5,325	$ 5,947
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	1,132	1,598	2,549	3,241
General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	1,064	$ 1,354	2,770	$ 2,706
Restructuring Charges [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 6		$ 6

Stockholder's Equity - Schedu39

Stockholder's Equity - Schedule of Weighted Average Assumptions Used under Black-Scholes Option-Pricing Model to Estimate Fair Value of Stock Options Granted Under 2013 Plan (Detail) - Stock Options [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average volatility	77.20%	71.60%	75.30%	67.80%
Weighted-average expected term (years)	6 years 2 months 12 days	6 years 2 months 12 days	6 years 2 months 12 days	6 years 2 months 12 days
Risk-free interest rate	2.10%	1.50%	2.20%	1.60%
Expected dividend yield

Stockholder's Equity - Schedu40

Stockholder's Equity - Schedule of Weighted Average Assumptions Used under Black-Scholes Option-Pricing Model to Estimate Fair Value of Company's ESPP at Grant Date (Detail) - Employees Stock Purchase Plan [Member]	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Weighted-average volatility	54.00%	104.50%	63.90%	75.00%
Weighted-average expected term (years)	6 months	6 months	6 months	6 months
Risk-free interest rate	0.50%	0.50%	0.50%	0.40%
Expected dividend yield

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Disclosure [Abstract]
Income tax provision (benefit)	$ 4	$ 4	$ 8	$ 6

Net Loss per Common Share - Out

Net Loss per Common Share - Outstanding Common Stock Equivalents Excluded from Computation of Diluted Net Loss per Common Share (Detail) - shares shares in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding shares of common stock equivalents	6,225	4,753
Options to purchase common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding shares of common stock equivalents	5,441	4,541
Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding shares of common stock equivalents	784	212

Restructuring Charges - Additio

Restructuring Charges - Additional Information (Detail) $ in Thousands	Apr. 24, 2017USD ($)Employee	Jun. 30, 2017USD ($)Employee	Jun. 30, 2017USD ($)Employee
Restructuring Cost And Reserve [Line Items]
Number of remaining employees	64
Percentage of reduction in workforce	48.00%
Restructuring plan, description			The Company is reducing its workforce by 60 employees (or 48%) to 64 employees. The affected employees were terminated as of April 25, 2017, with certain employees remaining with the Company for a limited time thereafter. As a result, the Company estimates that it will incur a total of approximately $2.5 million restructuring charges consisting of one-time severance payments and other employee related costs, and other charges. The Company incurred $2.4 million restructuring in charges during the six months ended June 30, 2017, of which a majority was paid out in cash during the second quarter of 2017. The Company expects the remainder of the amount to be incurred and paid out during the third and fourth quarters of 2017.
Number of affected employees terminated till date		53	53
Remaining number of employees to be terminated	7
Estimated restructuring charges | $	$ 2,500
Restructuring charges | $		$ 2,443	$ 2,443
Restructuring reserve | $		$ 300	$ 300
Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Number of workforce reduce	60

Restructuring Charges - Summary

Restructuring Charges - Summary of Restructuring Activity (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017
Restructuring Cost And Reserve [Line Items]
Costs incurred	$ 2,443	$ 2,443
Employee Severance and Other Costs [Member]
Restructuring Cost And Reserve [Line Items]
Costs incurred		2,443
Less cash payments		(2,110)
Less non-cash charges		(6)
Balance at June 30, 2017	$ 327	$ 327