OncoMed Pharmaceuticals 10-Q 1 Nov 18 2018 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2018	Oct. 31, 2018
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	Q3
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 Small Business	false
Entity Emerging Growth Company	true
Entity Ex Transition Period	true
Entity Common Stock, Shares Outstanding		38,630,145

Condensed Balance Sheets (Unaud

Condensed Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents	$ 8,406	$ 13,277
Short-term investments	62,450	89,814
Accounts receivable and other receivables	416	405
Prepaid and other current assets	1,913	1,709
Total current assets	73,185	105,205
Property and equipment, net	2,362	3,275
Other assets	1,606	1,842
Total assets	77,153	110,322
Current liabilities:
Accounts payable	3,163	2,565
Accrued liabilities	4,571	3,940
Accrued clinical liabilities	2,327	4,434
Current portion of deferred revenue	11,278	82,193
Total current liabilities	21,339	93,132
Deferred revenue, less current portion		61,645
Deferred rent	4,090	3,765
Non-current income tax payable		383
Total liabilities	25,429	158,925
Stockholders’ equity (deficit):
Preferred stock, $0.001 par value; 5,000,000 shares authorized at September 30, 2018 and December 31, 2017; no shares issued and outstanding at September 30, 2018 and December 31, 2017
Common stock, $0.001 par value; 145,000,000 shares authorized at September 30, 2018 and December 31, 2017; 38,525,781 and 38,212,505 shares issued and outstanding at September 30, 2018 and December 31, 2017, respectively	38	38
Additional paid-in capital	408,868	403,077
Accumulated other comprehensive income (loss)	(62)	289
Accumulated deficit	(357,120)	(452,007)
Total stockholders’ equity (deficit)	51,724	(48,603)
Total liabilities and stockholders' equity (deficit)	$ 77,153	$ 110,322

Condensed Balance Sheets (Una_2

Condensed Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Sep. 30, 2018	Dec. 31, 2017
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	38,525,781	38,212,505
Common stock, shares outstanding	38,525,781	38,212,505

Condensed Statements of Operati

Condensed Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Revenue:
Revenue	$ 19,518	$ 5,106	$ 34,237	$ 17,515
Operating expenses:
Research and development	10,025	12,191	26,466	51,268
General and administrative	3,702	3,871	12,800	12,952
Restructuring charges		69		2,513
Total operating expenses	13,727	16,131	39,266	66,733
Income (loss) from operations	5,791	(11,025)	(5,029)	(49,218)
Interest and other income, net	324	337	1,211	705
Income (loss) before provision for income taxes	6,115	(10,688)	(3,818)	(48,513)
Income tax provision (benefit)		4	(383)	12
Net income (loss)	$ 6,115	$ (10,692)	$ (3,435)	$ (48,525)
Net income (loss) per common share, basic and diluted	$ 0.16	$ (0.28)	$ (0.09)	$ (1.29)
Shares used to compute net income (loss) per common share, basic	38,508,204	37,662,868	38,381,374	37,520,608
Shares used to compute net income (loss) per common share, diluted	38,512,526	37,662,868	38,381,374	37,520,608
Collaboration Revenue [Member]
Revenue:
Revenue	$ 19,518	$ 5,013	$ 34,237	$ 15,467
Other Revenue [Member]
Revenue:
Revenue		$ 93		$ 2,048

Condensed Statements of Compreh

Condensed Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income (loss)	$ 6,115	$ (10,692)	$ (3,435)	$ (48,525)
Other comprehensive income (loss):
Unrealized loss on available-for-sale securities, net of tax	(5)	(97)	(351)	(85)
Total comprehensive income (loss)	$ 6,110	$ (10,789)	$ (3,786)	$ (48,610)

Condensed Statements of Cash Fl

Condensed Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities
Net loss	$ (3,435)	$ (48,525)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	1,288	1,286
Stock-based compensation	5,702	7,278
Changes in operating assets and liabilities:
Accounts receivable and other receivables	(11)	2,167
Prepaid and other current assets	(204)	65
Other assets	236	680
Accounts payable	598	(4,111)
Accrued liabilities	394	(3,651)
Accrued clinical liabilities	(2,107)	(12,975)
Deferred revenue	(34,237)	(15,497)
Deferred rent	325	662
Net cash used in operating activities	(31,451)	(72,621)
Investing activities
Purchases of property and equipment	(522)	(484)
Purchases of short-term investments	(77,379)	(107,502)
Maturities of short-term investments	104,392	157,327
Net cash provided by investing activities	26,491	49,341
Financing activities
Proceeds from issuance of common stock related to the exercise of options and employee stock plan purchases	89	2,204
Net cash provided by financing activities	89	2,204
Net decrease in cash and cash equivalents	(4,871)	(21,076)
Cash and cash equivalents at beginning of period	13,277	36,953
Cash and cash equivalents at end of period	8,406	$ 15,877
Supplemental cash flow information:
Accrued liabilities for purchase of property and equipment	$ 26

Organization

Organization	9 Months Ended
	Sep. 30, 2018
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 anti-cancer therapeutic candidates in active clinical development. The Company is also pursuing discovery of additional novel approaches to cancer treatment, including new immuno-oncology therapeutic candidates. 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	9 Months Ended
	Sep. 30, 2018
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, 2018 or for any subsequent interim period. The condensed balance sheet data as of December 31, 2017 was derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. 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, 2017, filed with the Securities and Exchange Commission (the “SEC”) on March 9, 2018. There have been no material changes to our significant accounting policies as of and for the nine months ended September 30, 2018, except for the policy related to revenue recognition. 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. Revenue Recognition Effective January 1, 2018, the Company adopted Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers, using the modified retrospective transition method. Under this method, the Company recorded a cumulative adjustment to the opening balance of accumulated deficit and to deferred revenue. Under Topic 606, the Company recognizes revenue when it transfers control of promised goods or services to its customers in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of Topic 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once a contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within the contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. The Company evaluated its existing contracts and only applied Topic 606 to those contracts that were not completed at January 1, 2018. As a result of this evaluation, the Company determined that only its collaboration with Celgene Corporation (“Celgene”) is within the scope of Topic 606. The Company the five-step model Milestone Payments At the inception of each arrangement that includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or partner, such as regulatory approvals, are not considered probable of being achieved until those approvals or the underlying activity has been completed Customer Concentration Customers whose revenue accounted for 10% or more of total revenues were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Celgene Corporation ("Celgene") 100% 100% 100% 88% Bayer Pharma AG ("Bayer") — — — 11% Net Income (Loss) per Common Share Basic net income (loss) per common share is calculated by dividing the net income (loss) by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net income (loss) per common share is computed by dividing the net income (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 stock options and restricted stock units are considered to be common stock equivalents. Common stock equivalents were excluded in the calculation of diluted net loss per common share because their effect would be anti-dilutive. Newly Adopted and Recent Accounting Pronouncements Accounting Standard Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition. Collaboration with Celgene The Company adopted the accounting standard update on January 1, 2018 using the modified retrospective approach, for its collaboration agreement with Celgene. Therefore, comparative historical information will not be adjusted and will continue to be reported under ASC 605 with the impact of the transition reflected in the opening balance of accumulated deficit as of January 1, 2018. The Company is eligible to receive consideration under this agreement that includes non-refundable upfront payments; development, regulatory, and sales milestone payments; and program opt-in payments; and royalties on net product sales. The new revenue recognition standard differs from ASC 605 in many respects, such as in the accounting for variable consideration and the measurement of progress toward completion of performance obligations. The most significant impact of the standard relates to the Company’s method of revenue recognition for performance obligations that are delivered over time. Under the new standard, milestone payments are included in the transaction price as variable consideration, subject to a constraint, and are allocated to the performance obligations in the contract when recognized. Through December 31, 2017, the Company also received payments from Celgene to reimburse the costs of research and development services performed by the Company; these payments were historically recorded as other revenue. As the performance of these research and development services was at the Company's discretion and is not reflective of a commitment or performance obligation pursuant to the Celgene agreement, the reimbursement paid to the Company has been excluded from the transaction price. The Company’s deferred revenue associated with its Celgene collaboration agreement as of December 31, 2017 under Topic 605 was $143.8 million. As a result of adopting Topic 606, the Company recorded a $98.3 million reduction to its deferred revenue and opening accumulated deficit on January 1, 2018 as a result of the cumulative impact of the change in the recognition of the upfront and milestone payments using the input method (described further in Note 5, “Collaborations” Collaborations with Bayer and GlaxoSmithKline (“GSK”) As the GSK collaboration was terminated in its entirety on October 28, 2017, this arrangement was outside the scope of Topic 606 as of the adoption date. For the Bayer collaboration, Bayer terminated all biologic therapeutic programs under the collaboration effective June 16, 2017, while the small molecule therapeutics program remained active. Refer to Note 5, “Collaborations,” for further details. The Company has determined that the small molecule therapeutic program remaining as of December 31, 2017 is immaterial in the context of the collaboration agreement relative to the biologics therapeutic programs that was terminated during 2017. The Company’s performance obligations under the small molecule therapeutic program with respect to Bayer were substantially complete at December 31, 2017, and any future receipts in the form of milestones or royalties are contingent upon the achievement of specified development, commercial and/or sales targets. The Company has concluded that there was no transition adjustment to be recognized on January 1, 2018 for these two agreements. Impact of Adoption The following table summarizes Balance at December 31, 2017 Adjustment Balance at January 1, 2018 Condensed Balance Sheets: Deferred revenue, current portion $ 82,193 $ (51,299 ) $ 30,894 Deferred revenue, non-current portion 61,645 (47,023 ) 14,622 Accumulated deficit (452,007 ) 98,322 (353,685 ) Three months ended September 30, 2018 As reported under Topic 606 Adjustment Balances without the adoption of Topic 606 Condensed Statements of Operations: Collaboration revenue $ 19,518 $ 1,031 $ 20,549 Income from operations 5,791 1,031 6,822 Net income 6,115 1,031 7,146 Net income per common shares, basic and diluted $ 0.16 $ 0.03 $ 0.19 Nine months ended September 30, 2018 As reported under Topic 606 Adjustment Balances without the adoption of Topic 606 Condensed Statements of Operations: Collaboration revenue $ 34,237 $ 27,410 $ 61,647 Income (loss) from operations (5,029 ) 27,410 22,381 Net income (loss) (3,435 ) 27,410 23,975 Net income (loss) per common shares, basic and diluted $ (0.09 ) $ 0.71 $ 0.62 Contract Balances Upfront payments and fees may be required to be recorded as deferred revenue upon receipt or when due, and recognized in a future period when or as the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. As of September 30, 2018, the contract liabilities, which consisted of deferred revenue, decreased by a total of $132.6 million from December 31, 2017, of which $98.3 million was related to the cumulative adjustment to the opening balance of accumulated deficit upon the adoption of Topic 606 on January 1, 2018 and $34.2 million related to revenue recognized for the nine months ended September 30, 2018. Upon adoption of the standard as of January 1, 2018, ASU No. 2016-02, Leases (Topic 842 ) In February 2016, the FASB issued ASU No. 2016-02, Leases accounting lease Leases (Topic 842) Targeted Improvements ASU No. 2018-07, Improvement to Nonemployees Share-based Payment Accounting (Topic 718 ) In June 2018, the FASB issued ASU No. 2018-07, Stock Compensation ASU No. 2018-13, Fair Value Measurements (Topic 820 ) In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement . ASU 2018-13 eliminates certain disclosure requirements for fair value measurements for all entities, requires public entities to disclose certain new information and modifies some disclosure requirements. This guidance will become effective The Company plans to adopt the guidance in the first quarter of 2020. The Company does not expect that the adoption of this standard will have a material impact on its financial statements.

Cash, Cash Equivalents and Inve

Cash, Cash Equivalents and Investments	9 Months Ended
	Sep. 30, 2018
Cash And Cash Equivalents [Abstract]
Cash, Cash Equivalents and Investments	3. Cash, Cash Equivalents and Investments The fair value of securities at September 30, 2018 and December 31, 2017, was as follows (in thousands): September 30, 2018 Amortized Gross Unrealized Fair Cost Gains Losses Value Money market funds $ 169 $ — $ — $ 169 U.S. treasury bills 62,512 — (62 ) 62,450 Total available-for-sale securities $ 62,681 $ — $ (62 ) $ 62,619 Classified as: Cash equivalents $ 169 Short-term investments 62,450 Total $ 62,619 As of September 30, 2018, the Company had a total of $70.9 million in cash, cash equivalents and short-term investments, which includes $8.4 million in cash and cash equivalents and $62.5 million in short-term investments. December 31, 2017 Amortized Gross Unrealized Fair Cost Gains Losses Value Money market funds $ 99 $ — $ — $ 99 U.S. treasury bills 89,525 289 — 89,814 Total available-for-sale securities $ 89,624 $ 289 $ — $ 89,913 Classified as: Cash equivalents $ 99 Short-term investments 89,814 Total $ 89,913 As of December 31, 2017, the Company had a total of $103.1 million in cash, cash equivalents and short-term investments, which includes $13.3 million in cash and cash equivalents and $89.8 million in short-term investments. All available-for-sale securities held as of September 30, 2018 and December 31, 2017 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	9 Months Ended
	Sep. 30, 2018
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): September 30, 2018 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 169 $ — $ — $ 169 U.S. treasury bills — 62,450 — 62,450 Total $ 169 $ 62,450 $ — $ 62,619 December 31, 2017 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 99 $ — $ — $ 99 U.S. treasury bills — 89,814 — 89,814 Total $ 99 $ 89,814 $ — $ 89,913 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	9 Months Ended
	Sep. 30, 2018
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 nine months ended September 30, 2018 and 2017 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Celgene: Recognition of upfront payments $ 19,518 $ 5,013 $ 34,237 $ 15,039 Other revenue — 93 — 311 Celgene total 19,518 5,106 34,237 15,350 Bayer: Recognition of upfront payments — — — 278 Other revenue — — — 1,734 Bayer total — — — 2,012 GSK: Recognition of upfront payments — — — 150 Other revenue — — — 3 GSK total — — — 153 Total collaboration related revenue $ 19,518 $ 5,106 $ 34,237 $ 17,515 Adoption of ASU No. 2014-09 On January 1, 2018, the Company adopted ASU No. 2014-09 using the modified retrospective method. Results for reporting periods beginning after January 1, 2018 are presented under Topic 606, while prior period amounts are not adjusted and continue to be reported in accordance with Topic 605. Celgene Strategic Alliance In December 2013, the Company entered into a collaboration agreement with Celgene pursuant to which the Company and Celgene are collaborating on research and development programs directed to the discovery and development of novel biologic therapeutics. In September 2018, Celgene informed the Company of Celgene’s decision not to exercise its option to license the navicixizumab program due to strategic product portfolio considerations. The Company and Celgene have formalized the termination of the collaboration agreement with respect to the navicixizumab program, and as a result, effective January 23, 2019, the Company will retain worldwide rights to navicixizumab. In October 2018, Celgene notified the Company of its decision not to exercise its option to license rosmantuzumab (anti-RSPO3, OMP-131R10) and terminated the companies’ collaboration agreement with respect to rosmantuzumab, effective February 12, 2019. The Company will retain worldwide rights to rosmantuzumab upon termination. The etigilimab (anti-TIGIT, OMP-313M32) program is the only program remaining under the collaboration. As of September 30, 2018, the Company is not eligible to receive any milestone payments under its collaboration with Celgene prior to the point that Celgene exercises its remaining option. The Company is eligible to receive up to approximately $35.0 million of contingent consideration if Celgene exercises its options for the etigilimab program. Following Celgene’s exercise of its option for the etigilimab program, Celgene will have exclusive development and commercialization rights worldwide, with the Company eligible to receive milestones and tiered royalties equal to a percentage of net product sales worldwide in the high-single digits to the mid-teens. If Celgene successfully develops and commercializes product candidates in the etigilimab program, the Company could receive additional contingent consideration of up to $402.5 million for the achievement of post-option exercise development, regulatory events and sales milestones. 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. The Company assessed its collaboration agreement with Celgene in accordance with Topic 606 and concluded that Celgene is a customer. The Company determined that its performance obligation under the arrangement with Celgene is research and development services. to assist Celgene in determining whether or not to exercise its options Prior to recognizing revenue, the Company estimates the transaction price, including variable consideration that is subject to a constraint. Amounts of variable consideration are included in the transaction price to the extent 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. Variable consideration includes payments based upon the achievement of specified milestones, and royalty payments based on product sales derived from the collaboration. Under the collaboration agreement, the Company determined that the non-refundable upfront cash payment of $155.0 million and stock premium of $1.7 million received in December 2013 constitute consideration to be included in the transaction price. The Company also included in the transaction price the $70.0 million demcizumab (anti-DLL4, OMP-21M18) safety milestone that was achieved in December 2015 and the two designation milestone payments of $2.5 million each for the designation of rosmantuzumab and etigilimab as clinical candidates in 2014 and 2015, respectively. The total consideration received of $231.7 million constitutes the transaction price at the transition date for Topic 606. Through December 31, 2017, the Company also received a total of $2.5 million in the aggregate from Celgene to reimburse the costs of research and development services performed by the Company; these reimbursements have historically been recorded as other revenue. As the performance of these research and development services was at the Company's discretion and is not a commitment or performance obligation pursuant to the Celgene collaboration agreement, the reimbursement paid to the Company has been excluded from the transaction price. None of the remaining development and regulatory milestone amounts have been included in the transaction price, as all milestone amounts were fully constrained as of January 1, 2018 and September 30, 2018. As part of the Company’s evaluation of the constraint, the Company considered numerous factors, including that receipt of the milestone amounts is outside the control of the Company and contingent upon success in future clinical trials. Any consideration related to sales milestones and royalties on net product sales will be recognized at the later of when the related sales occur or the performance obligation to which some or all of the sales milestone or royalty has been allocated is satisfied (in whole or in part) and therefore have also been excluded from the transaction price. The Company will re-evaluate the transaction price in each reporting period and as uncertain events are resolved or other changes in circumstances occur. Following the adoption of Topic 606, the Company recognizes collaboration revenue by measuring the progress toward complete satisfaction of the performance obligation using an input measure. The Company concluded the method that best correlates with progress of the services provided to Celgene is the input method, based on actual costs incurred to date compared to the overall total expected costs to satisfy the performance obligation. The Company will evaluate the estimate of expected costs to satisfy the performance obligation each reporting period and make adjustments for any significant changes. Under Topic 606, collaboration revenue under the Company’s collaboration agreement with Celgene was $34.2 million for the nine months ended September 30, 2018 and deferred revenue balance was $11.3 million as of September 30, 2018. The performance obligation under the contract is estimated to be substantially complete by the third quarter of 2019. The impact of adopting Topic 606 on the accounting treatment of the Company’s collaboration agreement with Celgene primarily relates to the change in the timing of revenue recognition of the transaction price. The Company’s deferred revenue associated with its Celgene collaboration agreement as of December 31, 2017 under Topic 605 was $143.8 million. Upon adoption of the standard as of January 1, 2018, the Company recognized a cumulative catch up adjustment of $98.3 million, which was recorded as a decrease to the opening balance of accumulated deficit, and a corresponding decrease in the deferred revenue balance from the Company’s collaboration with Celgene. Bayer Strategic Alliance In June 2010, the Company entered into a strategic alliance with Bayer to discover, develop and commercialize novel anti-CSC biologic and small molecule therapeutics targeting the Wnt signaling pathway. Effective June 16, 2017, Bayer terminated all biologic therapeutic programs under its collaboration with the Company. The Company is no longer eligible to receive any payments under its collaboration with Bayer with respect to biologic therapeutic candidates. With respect to the Wnt pathway small molecule program, the Company remains eligible to receive up to $27.0 million in development milestone payments for each small molecule candidate as well as contingent consideration payments for each small molecule candidate of up to $15.0 million for the achievement of certain regulatory events and up to $70.0 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. The Company evaluated the agreement under Topic 606, and determined that the small molecule therapeutic program remaining as of December 31, 2017 is immaterial in the context of the collaboration GSK Strategic Alliance Effective October 28, 2017, GSK terminated its collaboration agreement with the Company in its entirety. As a result of such termination, the Company is no longer eligible to receive any payments under the collaboration agreement with GSK and the Company has no remaining performance obligations. As the GSK collaboration was terminated in its entirety on October 28, 2017, this arrangement is outside the scope of Topic 606 as of the adoption date.

Stockholder's Equity

Stockholder's Equity	9 Months Ended
	Sep. 30, 2018
Equity [Abstract]
Stockholder's Equity	6. Stockholder’s Equity Equity Incentive Plans As of September 30, 2018, a total of 7,537,838 shares of common stock have been authorized under the 2013 Equity Incentive Award Plan (the “2013 Plan”), including the additional 1,500,000 shares of common stock that became available on January 1, 2018 for future issuance under the 2013 Plan as a result of an annual automatic increase provision in the 2013 Plan. As of September 30, 2018, a total of 5,422,638 shares are subject to options and restricted stock units (“RSUs”) outstanding under the 2013 Plan. There are 989,854 shares subject to options outstanding under the 2004 Stock Incentive Plan (the “2004 Plan”) as of September 30, 2018, 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 nine months ended September 30, 2018 (in thousands): Shares Available for Grant Options and of Options and Awards Awards Outstanding Balance at December 31, 2017 606 6,097 Additional shares authorized 1,500 — RSUs awarded (70 ) 70 Options granted (1,744 ) 1,744 RSUs vested — (268 ) Options forfeited 1,089 (1,089 ) RSUs forfeited 142 (142 ) Balance at September 30, 2018 1,523 6,412 The weighted-average grant date estimated fair value of options granted during the nine months ended September 30, 2018 was $2.32 per share. Employee Stock Purchase Plan As of September 30, 2018, a total of 1,893,620 shares of common stock have been authorized and 1,510,518 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, 2018 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 trading day of the offering period. During the nine months ended September 30, 2018, the Company issued 45,352 shares under the ESPP. 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 September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Research and development $ 954 $ 970 $ 2,881 $ 3,739 General and administrative 638 983 2,821 3,533 Restructuring charges — — — 6 Total $ 1,592 $ 1,953 $ 5,702 $ 7,278 As of September 30, 2018, the Company had $7.3 million, $1.7 million and $19,000 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 2.8 years, 0.9 years and 0.4 years, respectively.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2018
Income Tax Disclosure [Abstract]
Income Taxes	7. Income Taxes For the nine months ended September 30, 2018, the Company recorded an income tax benefit of $0.4 million in the condensed statement of operations as a result of a lapse of statute of limitations on uncertain tax positions and accrued state minimum taxes, treated as a discrete item. The Company’s deferred tax assets continue to be fully offset by a valuation allowance. In the fourth quarter of 2017, the period in which the Tax Cuts and Jobs Act (“Tax Act”) was enacted, the Company calculated its best estimate of the impact of the Tax Act in accordance with its understanding of the Tax Act. As a result, the Company recorded $1.1 million as income tax benefit in the fourth quarter of 2017 and a corresponding receivable for the expected alternative minimum tax credit refund

Net Income (Loss) per Common Sh

Net Income (Loss) per Common Share	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Net Income (Loss) per Common Share	8. Net Income (Loss) per Common Share The following is a computation of basic and diluted net income (loss) per share (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Net income (loss) $ 6,115 $ (10,692 ) $ (3,435 ) $ (48,525 ) Basic: Weighted-average common stock outstanding 38,508 37,663 38,381 37,521 Net income (loss) per share, basic $ 0.16 $ (0.28 ) $ (0.09 ) $ (1.29 ) Diluted: Weighted-average common stock outstanding 38,508 37,663 38,381 37,521 Add: Common equivalent shares outstanding 5 — — — Weighted-average common stock outstanding and dilutive shares 38,513 37,663 38,381 37,521 Net income (loss) per share, diluted $ 0.16 $ (0.28 ) $ (0.09 ) $ (1.29 ) The following outstanding common stock equivalents were excluded from the computation of diluted net income (loss) per common share for the periods presented because including them would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Options to purchase common stock 5,753 4,987 5,873 4,987 RSUs 540 667 540 667 6,293 5,654 6,413 5,654

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2018
Subsequent Events [Abstract]
Subsequent Events	9. Subsequent Events In October 2018, the Company signed an agreement to sublease a specified portion of the Company’s office facility located in Redwood City, California. The sublease has a term of 24 months and will expire in 2020. The aggregate sublease proceeds for the term of the lease are approximately $1.8 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2018
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, 2018 or for any subsequent interim period. The condensed balance sheet data as of December 31, 2017 was derived from the audited financial statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. 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, 2017, filed with the Securities and Exchange Commission (the “SEC”) on March 9, 2018. There have been no material changes to our significant accounting policies as of and for the nine months ended September 30, 2018, except for the policy related to revenue recognition.
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.
Revenue Recognition	Revenue Recognition Effective January 1, 2018, the Company adopted Accounting Standards Codification, or ASC, Topic 606, Revenue from Contracts with Customers, using the modified retrospective transition method. Under this method, the Company recorded a cumulative adjustment to the opening balance of accumulated deficit and to deferred revenue. Under Topic 606, the Company recognizes revenue when it transfers control of promised goods or services to its customers in an amount that reflects the consideration which the Company expects to receive in exchange for those goods or services. To determine revenue recognition for arrangements that the Company determines are within the scope of Topic 606, the Company performs the following five steps: (i) identify the contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when (or as) the entity satisfies a performance obligation. The Company only applies the five-step model to contracts when it is probable that the Company will collect the consideration it is entitled to in exchange for the goods or services it transfers to the customer. At contract inception, once a contract is determined to be within the scope of Topic 606, the Company assesses the goods or services promised within the contract and determines those that are performance obligations, and assesses whether each promised good or service is distinct. The Company then recognizes as revenue the amount of the transaction price that is allocated to the respective performance obligation when (or as) the performance obligation is satisfied. The Company evaluated its existing contracts and only applied Topic 606 to those contracts that were not completed at January 1, 2018. As a result of this evaluation, the Company determined that only its collaboration with Celgene Corporation (“Celgene”) is within the scope of Topic 606. The Company the five-step model Milestone Payments At the inception of each arrangement that includes development, regulatory or commercial milestone payments, the Company evaluates whether the milestones are considered probable of being reached and estimates the amount to be included in the transaction price using the most likely amount method. If it is probable that a significant reversal of cumulative revenue would not occur, the associated milestone value is included in the transaction price. Milestone payments that are not within the control of the Company or partner, such as regulatory approvals, are not considered probable of being achieved until those approvals or the underlying activity has been completed
Customer Concentration	Customer Concentration Customers whose revenue accounted for 10% or more of total revenues were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Celgene Corporation ("Celgene") 100% 100% 100% 88% Bayer Pharma AG ("Bayer") — — — 11%
Net Income (Loss) per Common Share	Net Income (Loss) per Common Share Basic net income (loss) per common share is calculated by dividing the net income (loss) by the weighted-average number of common shares outstanding during the period, without consideration for common stock equivalents. Diluted net income (loss) per common share is computed by dividing the net income (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 stock options and restricted stock units are considered to be common stock equivalents. Common stock equivalents were excluded in the calculation of diluted net loss per common share because their effect would be anti-dilutive.
Newly Adopted and Recent Accounting Pronouncements	Newly Adopted and Recent Accounting Pronouncements Accounting Standard Update (“ASU”) No. 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes the revenue recognition requirements in ASC 605, Revenue Recognition. Collaboration with Celgene The Company adopted the accounting standard update on January 1, 2018 using the modified retrospective approach, for its collaboration agreement with Celgene. Therefore, comparative historical information will not be adjusted and will continue to be reported under ASC 605 with the impact of the transition reflected in the opening balance of accumulated deficit as of January 1, 2018. The Company is eligible to receive consideration under this agreement that includes non-refundable upfront payments; development, regulatory, and sales milestone payments; and program opt-in payments; and royalties on net product sales. The new revenue recognition standard differs from ASC 605 in many respects, such as in the accounting for variable consideration and the measurement of progress toward completion of performance obligations. The most significant impact of the standard relates to the Company’s method of revenue recognition for performance obligations that are delivered over time. Under the new standard, milestone payments are included in the transaction price as variable consideration, subject to a constraint, and are allocated to the performance obligations in the contract when recognized. Through December 31, 2017, the Company also received payments from Celgene to reimburse the costs of research and development services performed by the Company; these payments were historically recorded as other revenue. As the performance of these research and development services was at the Company's discretion and is not reflective of a commitment or performance obligation pursuant to the Celgene agreement, the reimbursement paid to the Company has been excluded from the transaction price. The Company’s deferred revenue associated with its Celgene collaboration agreement as of December 31, 2017 under Topic 605 was $143.8 million. As a result of adopting Topic 606, the Company recorded a $98.3 million reduction to its deferred revenue and opening accumulated deficit on January 1, 2018 as a result of the cumulative impact of the change in the recognition of the upfront and milestone payments using the input method (described further in Note 5, “Collaborations” Collaborations with Bayer and GlaxoSmithKline (“GSK”) As the GSK collaboration was terminated in its entirety on October 28, 2017, this arrangement was outside the scope of Topic 606 as of the adoption date. For the Bayer collaboration, Bayer terminated all biologic therapeutic programs under the collaboration effective June 16, 2017, while the small molecule therapeutics program remained active. Refer to Note 5, “Collaborations,” for further details. The Company has determined that the small molecule therapeutic program remaining as of December 31, 2017 is immaterial in the context of the collaboration agreement relative to the biologics therapeutic programs that was terminated during 2017. The Company’s performance obligations under the small molecule therapeutic program with respect to Bayer were substantially complete at December 31, 2017, and any future receipts in the form of milestones or royalties are contingent upon the achievement of specified development, commercial and/or sales targets. The Company has concluded that there was no transition adjustment to be recognized on January 1, 2018 for these two agreements. Impact of Adoption The following table summarizes Balance at December 31, 2017 Adjustment Balance at January 1, 2018 Condensed Balance Sheets: Deferred revenue, current portion $ 82,193 $ (51,299 ) $ 30,894 Deferred revenue, non-current portion 61,645 (47,023 ) 14,622 Accumulated deficit (452,007 ) 98,322 (353,685 ) Three months ended September 30, 2018 As reported under Topic 606 Adjustment Balances without the adoption of Topic 606 Condensed Statements of Operations: Collaboration revenue $ 19,518 $ 1,031 $ 20,549 Income from operations 5,791 1,031 6,822 Net income 6,115 1,031 7,146 Net income per common shares, basic and diluted $ 0.16 $ 0.03 $ 0.19 Nine months ended September 30, 2018 As reported under Topic 606 Adjustment Balances without the adoption of Topic 606 Condensed Statements of Operations: Collaboration revenue $ 34,237 $ 27,410 $ 61,647 Income (loss) from operations (5,029 ) 27,410 22,381 Net income (loss) (3,435 ) 27,410 23,975 Net income (loss) per common shares, basic and diluted $ (0.09 ) $ 0.71 $ 0.62 Contract Balances Upfront payments and fees may be required to be recorded as deferred revenue upon receipt or when due, and recognized in a future period when or as the Company performs its obligations under these arrangements. Amounts payable to the Company are recorded as accounts receivable when the Company’s right to consideration is unconditional. As of September 30, 2018, the contract liabilities, which consisted of deferred revenue, decreased by a total of $132.6 million from December 31, 2017, of which $98.3 million was related to the cumulative adjustment to the opening balance of accumulated deficit upon the adoption of Topic 606 on January 1, 2018 and $34.2 million related to revenue recognized for the nine months ended September 30, 2018. Upon adoption of the standard as of January 1, 2018, ASU No. 2016-02, Leases (Topic 842 ) In February 2016, the FASB issued ASU No. 2016-02, Leases accounting lease Leases (Topic 842) Targeted Improvements ASU No. 2018-07, Improvement to Nonemployees Share-based Payment Accounting (Topic 718 ) In June 2018, the FASB issued ASU No. 2018-07, Stock Compensation ASU No. 2018-13, Fair Value Measurements (Topic 820 ) In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement . ASU 2018-13 eliminates certain disclosure requirements for fair value measurements for all entities, requires public entities to disclose certain new information and modifies some disclosure requirements. This guidance will become effective The Company plans to adopt the guidance in the first quarter of 2020. The Company does not expect that the adoption of this standard will have a material impact on its financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2018
ASU 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Impact of Adopting Topic 606 on Select Unaudited Condensed Balance Sheets and Condensed Statement of Operations	Impact of Adoption The following table summarizes Balance at December 31, 2017 Adjustment Balance at January 1, 2018 Condensed Balance Sheets: Deferred revenue, current portion $ 82,193 $ (51,299 ) $ 30,894 Deferred revenue, non-current portion 61,645 (47,023 ) 14,622 Accumulated deficit (452,007 ) 98,322 (353,685 ) Three months ended September 30, 2018 As reported under Topic 606 Adjustment Balances without the adoption of Topic 606 Condensed Statements of Operations: Collaboration revenue $ 19,518 $ 1,031 $ 20,549 Income from operations 5,791 1,031 6,822 Net income 6,115 1,031 7,146 Net income per common shares, basic and diluted $ 0.16 $ 0.03 $ 0.19 Nine months ended September 30, 2018 As reported under Topic 606 Adjustment Balances without the adoption of Topic 606 Condensed Statements of Operations: Collaboration revenue $ 34,237 $ 27,410 $ 61,647 Income (loss) from operations (5,029 ) 27,410 22,381 Net income (loss) (3,435 ) 27,410 23,975 Net income (loss) per common shares, basic and diluted $ (0.09 ) $ 0.71 $ 0.62
Revenue [Member] | Customer Concentration [Member]
Summary Of Significant Accounting Policies [Line Items]
Schedule of Customer Concentration of Revenue	Customers whose revenue accounted for 10% or more of total revenues were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Celgene Corporation ("Celgene") 100% 100% 100% 88% Bayer Pharma AG ("Bayer") — — — 11%

Cash, Cash Equivalents and In_2

Cash, Cash Equivalents and Investments (Tables)	9 Months Ended
	Sep. 30, 2018
Cash And Cash Equivalents [Abstract]
Schedule of Fair Value of Securities, Not Including Cash	The fair value of securities at September 30, 2018 and December 31, 2017, was as follows (in thousands): September 30, 2018 Amortized Gross Unrealized Fair Cost Gains Losses Value Money market funds $ 169 $ — $ — $ 169 U.S. treasury bills 62,512 — (62 ) 62,450 Total available-for-sale securities $ 62,681 $ — $ (62 ) $ 62,619 Classified as: Cash equivalents $ 169 Short-term investments 62,450 Total $ 62,619 As of September 30, 2018, the Company had a total of $70.9 million in cash, cash equivalents and short-term investments, which includes $8.4 million in cash and cash equivalents and $62.5 million in short-term investments. December 31, 2017 Amortized Gross Unrealized Fair Cost Gains Losses Value Money market funds $ 99 $ — $ — $ 99 U.S. treasury bills 89,525 289 — 89,814 Total available-for-sale securities $ 89,624 $ 289 $ — $ 89,913 Classified as: Cash equivalents $ 99 Short-term investments 89,814 Total $ 89,913

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	9 Months Ended
	Sep. 30, 2018
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): September 30, 2018 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 169 $ — $ — $ 169 U.S. treasury bills — 62,450 — 62,450 Total $ 169 $ 62,450 $ — $ 62,619 December 31, 2017 Level 1 Level 2 Level 3 Total Assets: Money market funds $ 99 $ — $ — $ 99 U.S. treasury bills — 89,814 — 89,814 Total $ 99 $ 89,814 $ — $ 89,913

Collaborations (Tables)

Collaborations (Tables)	9 Months Ended
	Sep. 30, 2018
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 nine months ended September 30, 2018 and 2017 (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Celgene: Recognition of upfront payments $ 19,518 $ 5,013 $ 34,237 $ 15,039 Other revenue — 93 — 311 Celgene total 19,518 5,106 34,237 15,350 Bayer: Recognition of upfront payments — — — 278 Other revenue — — — 1,734 Bayer total — — — 2,012 GSK: Recognition of upfront payments — — — 150 Other revenue — — — 3 GSK total — — — 153 Total collaboration related revenue $ 19,518 $ 5,106 $ 34,237 $ 17,515

Stockholder's Equity (Tables)

Stockholder's Equity (Tables)	9 Months Ended
	Sep. 30, 2018
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 nine months ended September 30, 2018 (in thousands): Shares Available for Grant Options and of Options and Awards Awards Outstanding Balance at December 31, 2017 606 6,097 Additional shares authorized 1,500 — RSUs awarded (70 ) 70 Options granted (1,744 ) 1,744 RSUs vested — (268 ) Options forfeited 1,089 (1,089 ) RSUs forfeited 142 (142 ) Balance at September 30, 2018 1,523 6,412
Schedule of Stock-Based Compensation Expense	Stock-based compensation expense recognized was as follows (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Research and development $ 954 $ 970 $ 2,881 $ 3,739 General and administrative 638 983 2,821 3,533 Restructuring charges — — — 6 Total $ 1,592 $ 1,953 $ 5,702 $ 7,278

Net Income (Loss) per Common _2

Net Income (Loss) per Common Share (Tables)	9 Months Ended
	Sep. 30, 2018
Earnings Per Share [Abstract]
Schedule of Computation of Basic and Diluted Net Income (Loss) per Share	The following is a computation of basic and diluted net income (loss) per share (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Net income (loss) $ 6,115 $ (10,692 ) $ (3,435 ) $ (48,525 ) Basic: Weighted-average common stock outstanding 38,508 37,663 38,381 37,521 Net income (loss) per share, basic $ 0.16 $ (0.28 ) $ (0.09 ) $ (1.29 ) Diluted: Weighted-average common stock outstanding 38,508 37,663 38,381 37,521 Add: Common equivalent shares outstanding 5 — — — Weighted-average common stock outstanding and dilutive shares 38,513 37,663 38,381 37,521 Net income (loss) per share, diluted $ 0.16 $ (0.28 ) $ (0.09 ) $ (1.29 )
Outstanding Common Stock Equivalents Excluded from Computation of Diluted Net Income (Loss) per Common Share	The following outstanding common stock equivalents were excluded from the computation of diluted net income (loss) per common share for the periods presented because including them would have been anti-dilutive (in thousands): Three Months Ended September 30, Nine Months Ended September 30, 2018 2017 2018 2017 Options to purchase common stock 5,753 4,987 5,873 4,987 RSUs 540 667 540 667 6,293 5,654 6,413 5,654

Organization - Additional Infor

Organization - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018Segment
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Number of operating segment	1

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	Jan. 01, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Summary Of Significant Accounting Policies [Line Items]
Contract liability		$ 11,300,000		$ 11,300,000
Decrease in deferred revenue				34,237,000	$ 15,497,000
Collaboration revenue		19,518,000	$ 5,106,000	34,237,000	17,515,000
Changes in transaction price		0		0
Collaboration Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaboration revenue		19,518,000	5,013,000	34,237,000	15,467,000
ASU 2014-09 [Member]
Summary Of Significant Accounting Policies [Line Items]
Decrease in accumulated deficit	$ 98,300,000
Decrease in deferred revenue				132,600,000
ASU 2014-09 [Member] | Topic 605 [Member] | Collaboration Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaboration revenue		20,549,000		61,647,000
ASU 2014-09 [Member] | Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract liability	45,500,000
Decrease in accumulated deficit	98,300,000
Decrease in deferred revenue	98,300,000
ASU 2014-09 [Member] | Adjustment [Member] | Collaboration Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaboration revenue		1,031,000		27,410,000
Collaborative Arrangement [Member] | Collaboration Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaboration revenue		19,518,000	5,106,000	34,237,000	17,515,000
Celgene [Member] | Collaborative Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract liability						$ 143,800,000
Celgene [Member] | Collaborative Arrangement [Member] | Collaboration Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaboration revenue		19,518,000	$ 5,106,000	34,237,000	$ 15,350,000
Celgene [Member] | Collaborative Arrangement [Member] | Topic 605 [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract liability						$ 143,800,000
Celgene [Member] | Collaborative Arrangement [Member] | ASU 2014-09 [Member] | Adjustment [Member]
Summary Of Significant Accounting Policies [Line Items]
Contract liability	45,500,000	$ 11,300,000		11,300,000
Decrease in accumulated deficit	$ 98,300,000
Celgene [Member] | Collaborative Arrangement [Member] | ASU 2014-09 [Member] | Adjustment [Member] | Collaboration Revenue [Member]
Summary Of Significant Accounting Policies [Line Items]
Collaboration revenue				$ 34,200,000
Revenue [Member] | Customer Concentration [Member] | Celgene [Member] | Collaborative Arrangement [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage of revenue represented by major customers		100.00%	100.00%	100.00%	88.00%
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 Accoun_5

Summary of Significant Accounting Policies - Schedule of Customer Concentration of Revenue (Detail) - Revenue [Member] - Customer Concentration [Member] - Collaborative Arrangement [Member]	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Bayer [Member]
Concentration Risk [Line Items]
Collaborative research and development revenue, Percentage				11.00%
Celgene [Member]
Concentration Risk [Line Items]
Collaborative research and development revenue, Percentage	100.00%	100.00%	100.00%	88.00%

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Impact of Adopting Topic 606 on Select Unaudited Condensed Balance Sheet and Condensed Statement of Operations (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Condensed Balance Sheets:
Deferred revenue, current portion	$ 11,278		$ 11,278			$ 82,193
Deferred revenue, non-current portion						61,645
Accumulated deficit	(357,120)		(357,120)			$ (452,007)
Condensed Statements of Operations:
Collaboration revenue	19,518	$ 5,106	34,237	$ 17,515
Income (loss) from operations	5,791	(11,025)	(5,029)	(49,218)
Net income (loss)	$ 6,115	$ (10,692)	$ (3,435)	$ (48,525)
Net income (loss) per common shares, basic and diluted	$ 0.16	$ (0.28)	$ (0.09)	$ (1.29)
Collaboration Revenue [Member]
Condensed Statements of Operations:
Collaboration revenue	$ 19,518	$ 5,013	$ 34,237	$ 15,467
ASU 2014-09 [Member]
Condensed Balance Sheets:
Deferred revenue, current portion					$ 30,894
Deferred revenue, non-current portion					14,622
Accumulated deficit					(353,685)
ASU 2014-09 [Member] | Adjustment [Member]
Condensed Balance Sheets:
Deferred revenue, current portion					(51,299)
Deferred revenue, non-current portion					(47,023)
Accumulated deficit					$ 98,322
Condensed Statements of Operations:
Income (loss) from operations	1,031		27,410
Net income (loss)	$ 1,031		$ 27,410
Net income (loss) per common shares, basic and diluted	$ 0.03		$ 0.71
ASU 2014-09 [Member] | Adjustment [Member] | Collaboration Revenue [Member]
Condensed Statements of Operations:
Collaboration revenue	$ 1,031		$ 27,410
ASU 2014-09 [Member] | Balances without the adoption of Topic 606 [Member]
Condensed Statements of Operations:
Income (loss) from operations	6,822		22,381
Net income (loss)	$ 7,146		$ 23,975
Net income (loss) per common shares, basic and diluted	$ 0.19		$ 0.62
ASU 2014-09 [Member] | Balances without the adoption of Topic 606 [Member] | Collaboration Revenue [Member]
Condensed Statements of Operations:
Collaboration revenue	$ 20,549		$ 61,647

Cash, Cash Equivalents and In_3

Cash, Cash Equivalents and Investments - Schedule of Fair Value of Securities, Not Including Cash (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 62,681	$ 89,624
Gross Unrealized Gains		289
Gross Unrealized Losses	(62)
Fair Value	62,619	89,913
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	169	99
Fair Value	169	99
U.S. Treasury Bills [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	62,512	89,525
Gross Unrealized Gains		289
Gross Unrealized Losses	(62)
Fair Value	62,450	89,814
Cash and Cash Equivalents [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	169	99
Short-Term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value	$ 62,450	$ 89,814

Cash, Cash Equivalents and In_4

Cash, Cash Equivalents and Investments - Additional Information (Detail) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]
Total cash, cash equivalents, and short-term investments	$ 70,900,000	$ 103,100,000
Cash and cash equivalents	8,406,000	13,277,000	$ 15,877,000	$ 36,953,000
Short-term investments	62,450,000	89,814,000
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	Sep. 30, 2018	Dec. 31, 2017
Assets:
Assets fair value disclosure	$ 62,619	$ 89,913
Level 1 [Member]
Assets:
Assets fair value disclosure	169	99
Level 2 [Member]
Assets:
Assets fair value disclosure	62,450	89,814
Money Market Funds [Member]
Assets:
Assets fair value disclosure	169	99
Money Market Funds [Member] | Level 1 [Member]
Assets:
Assets fair value disclosure	169	99
U.S. Treasury Bills [Member]
Assets:
Assets fair value disclosure	62,450	89,814
U.S. Treasury Bills [Member] | Level 2 [Member]
Assets:
Assets fair value disclosure	$ 62,450	$ 89,814

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Detail)	Sep. 30, 2018USD ($)
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		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	$ 19,518	$ 5,106	$ 34,237	$ 17,515
Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	19,518	5,013	34,237	15,467
Collaboration Revenue [Member] | Collaborative Arrangement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	19,518	5,106	34,237	17,515
Collaboration Revenue [Member] | Collaborative Arrangement [Member] | Celgene [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue	19,518	5,013	34,237	15,039
Collaboration revenue		93		311
Collaboration revenue	$ 19,518	$ 5,106	$ 34,237	15,350
Collaboration Revenue [Member] | Collaborative Arrangement [Member] | GlaxoSmithKline [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue				150
Collaboration revenue				3
Collaboration revenue				153
Collaboration Revenue [Member] | Collaborative Arrangement [Member] | Bayer [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue				278
Collaboration revenue				1,734
Collaboration revenue				$ 2,012

Collaborations - Celgene Strate

Collaborations - Celgene Strategic Alliance - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 01, 2018	Dec. 31, 2013	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017	Dec. 31, 2015	Dec. 31, 2014
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability			$ 11,300		$ 11,300
Collaboration revenue			19,518	$ 5,106	34,237	$ 17,515
Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue			19,518	5,013	34,237	15,467
ASU 2014-09 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Decrease in accumulated deficit	$ 98,300
Topic 606 [Member] | ASU 2014-09 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability	45,500
Decrease in accumulated deficit	98,300
Topic 606 [Member] | ASU 2014-09 [Member] | Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue			1,031		27,410
Collaborative Arrangement [Member] | Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue			19,518	5,106	34,237	17,515
Celgene [Member] | Collaborative Arrangement [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Non-refundable upfront cash payment received		$ 155,000
Premium on closing price of common stock value		$ 1,700
Contract liability							$ 143,800
Reimbursement of research and development services costs							$ 2,500
Celgene [Member] | Collaborative Arrangement [Member] | Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue			19,518	$ 5,106	34,237	$ 15,350
Celgene [Member] | Collaborative Arrangement [Member] | Topic 606 [Member] | ASU 2014-09 [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability	45,500		11,300		11,300
Total consideration					231,700
Decrease in accumulated deficit	$ 98,300
Celgene [Member] | Collaborative Arrangement [Member] | Topic 606 [Member] | ASU 2014-09 [Member] | Collaboration Revenue [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Collaboration revenue					34,200
Celgene [Member] | Collaborative Arrangement [Member] | Etigilimab [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future development milestone payments			$ 35,000		35,000
Additional contingent consideration for regulatory events					$ 402,500
Payment receivable under agreement								$ 2,500
Celgene [Member] | Collaborative Arrangement [Member] | Demcizumab [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contract liability								$ 70,000
Celgene [Member] | Collaborative Arrangement [Member] | Rosmantuzumab [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Payment receivable under agreement									$ 2,500

Collaborations - Bayer Strategi

Collaborations - Bayer Strategic Alliance - Additional Information (Detail) - Bayer [Member] - Collaborative Arrangement [Member] - Small Molecules [Member] $ in Millions	Jun. 16, 2017USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Future development milestone payments	$ 27
Contingent consideration payments for regulatory events	15
Achievement of Specified Future Product Sales [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent consideration payments for regulatory events	$ 70

Collaborations - GSK Strategic

Collaborations - GSK Strategic Alliance - Additional Information (Detail)	9 Months Ended
	Sep. 30, 2018
Collaborative Arrangement [Member] | GlaxoSmithKline [Member]
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Effective date of termination	Oct. 28, 2017

Stockholder's Equity - Addition

Stockholder's Equity - Additional Information (Detail) - USD ($)	9 Months Ended
	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock subject to options outstanding	6,412,000		6,097,000
Weighted-average grant-date fair value, granted	$ 2.32
Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 7,300,000
Estimated weighted-average period	2 years 9 months 18 days
Restricted Stock Units [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized stock-based compensation expense	$ 1,700,000
Estimated weighted-average period	10 months 24 days
Employees Stock Purchase Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized	1,893,620
Common stock available for future issuance under plan	1,510,518	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	45,352
Unrecognized stock-based compensation expense	$ 19,000
Estimated weighted-average period	4 months 24 days
2013 Equity Incentive Award Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock shares authorized	7,537,838
Common stock available for future issuance under plan		1,500,000
Common stock subject to options and restricted stock units outstanding	5,422,638
2004 Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock subject to options outstanding	989,854

Stockholder's Equity - Summary

Stockholder's Equity - Summary of Stock Option and RSU Award Activity under 2004 Plan and 2013 Stock Plan (Detail)	9 Months Ended
	Sep. 30, 2018shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Shares Available for Grant, Beginning Balance	606,000
Shares Available for Grant, Additional Options authorized	1,500,000
Shares Available for Grant, Options granted	(1,744,000)
Shares Available for Grant, Options forfeited	1,089,000
Shares Available for Grant, Ending Balance	1,523,000
Options Outstanding, Beginning Balance	6,097,000
Options and Awards Outstanding, Additional Options authorized	0
Options Outstanding, Options granted	1,744,000
Options Outstanding, Options forfeited	(1,089,000)
Options Outstanding, Ending Balance	6,412,000
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	(70,000)
Shares Available for Grant of Options and Awards, RSU vested	0
Shares Available for Grant of Options and Awards, RSUs forfeited	142,000
Options and Awards Outstanding, RSUs awarded	70,000
Options and Awards Outstanding, RSU vested	(268,000)
Options and Awards Outstanding, RSUs forfeited	(142,000)

Stockholder's Equity - Schedule

Stockholder's Equity - Schedule of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 1,592	$ 1,953	$ 5,702	$ 7,278
Research and Development [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	954	970	2,881	3,739
General and Administrative [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation	$ 638	$ 983	$ 2,821	3,533
Restructuring Charges [Member]
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation				$ 6

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income tax provision (benefit)		$ 4	$ (383)	$ 12
Income tax benefit	$ (1,100)
Reduction in deferred tax assets			$ 51,700

Net Income (Loss) per Common _3

Net Income (Loss) per Common Share - Schedule of Computation of Basic and Diluted Net Income (Loss) per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Earnings Per Share [Abstract]
Net income (loss)	$ 6,115	$ (10,692)	$ (3,435)	$ (48,525)
Basic:
Weighted-average common stock outstanding	38,508,204	37,662,868	38,381,374	37,520,608
Net income (loss) per share, basic	$ 0.16	$ (0.28)	$ (0.09)	$ (1.29)
Diluted:
Weighted-average common stock outstanding	38,508,204	37,662,868	38,381,374	37,520,608
Add: Common equivalent shares outstanding	5,000
Weighted-average common stock outstanding and dilutive shares	38,512,526	37,662,868	38,381,374	37,520,608
Net income (loss) per share, diluted	$ 0.16	$ (0.28)	$ (0.09)	$ (1.29)

Net Income (Loss) per Common _4

Net Income (Loss) per Common Share - Outstanding Common Stock Equivalents Excluded from Computation of Diluted Net Income (Loss) per Common Share (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding shares of common stock equivalents	6,293	5,654	6,413	5,654
Options to purchase common stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding shares of common stock equivalents	5,753	4,987	5,873	4,987
Restricted Stock Units [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Outstanding shares of common stock equivalents	540	667	540	667

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event - Redwood City, California - Office Facility $ in Millions	1 Months Ended
	Oct. 31, 2018USD ($)
Subsequent Event [Line Items]
Sublease rentals term	24 months
Sub lease rentals expiration year	2,020
Aggregate sublease proceeds	$ 1.8