Puma Biotechnology (PBYI) 10-Q 10 May 17 2017 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2017	May 04, 2017
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q1
Trading Symbol	PBYI
Entity Registrant Name	PUMA BIOTECHNOLOGY, INC.
Entity Central Index Key	1,401,667
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		36,966,278

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 105,086	$ 194,494
Marketable securities	88,894	34,982
Prepaid expenses and other, current	10,654	6,998
Total current assets	204,634	236,474
Property and equipment, net	5,000	5,153
Prepaid expenses and other, long-term	2,674	6,846
Restricted cash	4,316	4,317
Total assets	216,624	252,790
Current liabilities:
Accounts payable	23,970	20,035
Accrued expenses	19,760	17,426
Total current liabilities	43,730	37,461
Deferred rent	5,502	5,505
Total liabilities	49,232	42,966
Commitments and contingencies (Note 8)
Stockholders' equity:
Common stock - $.0001 par value; 100,000,000 shares authorized; 36,963,278 shares issued and outstanding at March 31, 2017 and 36,826,010 issued and outstanding at December 31, 2016	4	4
Additional paid-in capital	1,036,825	1,006,344
Receivables from the exercise of options	(11)
Accumulated other comprehensive loss	(50)	(13)
Accumulated deficit	(869,376)	(796,511)
Total stockholders' equity	167,392	209,824
Total liabilities and stockholders' equity	$ 216,624	$ 252,790

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - $ / shares	Mar. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	36,963,278	36,826,010
Common stock, shares outstanding	36,963,278	36,826,010

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating expenses:
General and administrative	$ 18,401	$ 11,039
Research and development	54,801	60,207
Total Operating Expense	73,202	71,246
Loss from operations	(73,202)	(71,246)
Other (expenses) income:
Interest income	350	282
Other (expenses) income	(13)	(8)
Total Other Income	337	274
Net loss	(72,865)	(70,972)
Net loss applicable to common stock	$ (72,865)	$ (70,972)
Net loss per common share—basic and diluted	$ (1.97)	$ (2.19)
Weighted-average common shares outstanding—basic and diluted	36,931,167	32,478,408

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (72,865)	$ (70,972)
Other comprehensive loss
Unrealized gain (loss) on available-for-sale securities	(37)	176
Comprehensive loss	$ (72,902)	$ (70,796)

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 3 months ended Mar. 31, 2017 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Receivables from the Exercises of Options	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2016	$ 209,824	$ 4	$ 1,006,344		$ (13)	$ (796,511)
Beginning Balance (in shares) at Dec. 31, 2016	36,826,010	36,826,010
Stock-based compensation	$ 29,764		29,764
Exercises of stock options/issuances of RSUs	$ 706		717	$ (11)
Exercises of stock options/issuances of RSUs (in shares)	33,468	137,268
Unrealized gain on available-for-sale securities	$ (37)				(37)
Net loss	(72,865)					(72,865)
Ending Balance at Mar. 31, 2017	$ 167,392	$ 4	$ 1,036,825	$ (11)	$ (50)	$ (869,376)
Ending Balance (in shares) at Mar. 31, 2017	36,963,278	36,963,278

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net loss	$ (72,865)	$ (70,972)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	277	208
Stock-based compensation	29,764	29,510
Changes in operating assets and liabilities:
Prepaid expenses and other	516	(170)
Accounts payable	3,935	7,034
Accrued expenses	2,334	(571)
Accrual of deferred rent	(3)	(67)
Net cash used in operating activities	(36,042)	(35,028)
Investing activities:
Purchase of property and equipment	(124)	(44)
Restricted cash	1	(1)
Purchase of available-for-sale securities	(79,728)	(36,768)
Sale/maturity of available-for-sale securities	25,779	118,269
Net cash (used in) provided by investing activities	(54,072)	81,456
Financing activities:
Net proceeds from exercise of options	706	222
Net cash provided by financing activities	706	222
Net increase in cash and cash equivalents	(89,408)	46,650
Cash and cash equivalents, beginning of period	194,494	31,569
Cash and cash equivalents, end of period	$ 105,086	$ 78,219

Business and Basis of Presentat

Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Business and Basis of Presentation	Note 1—Business and Basis of Presentation: Business: Puma Biotechnology, Inc., or Puma, is a biopharmaceutical company based in Los Angeles, California with a focus on the development and commercialization of innovative products to enhance cancer care. The Company in-licenses the global development and commercialization rights to three drug candidates—PB272 (neratinib (oral)), PB272 (neratinib (intravenous)) and PB357. Neratinib is a potent irreversible tyrosine kinase inhibitor that blocks signal transduction through the epidermal growth factor receptors, HER1, HER2 and HER4. Currently, the Company is primarily focused on the development of the oral version of neratinib, and its most advanced drug candidates are directed at the treatment of HER2-positive breast cancer. The Company believes that neratinib has clinical application in the treatment of several other cancers as well, including non-small cell lung cancer and other tumor types that over-express or have a mutation in HER2. In November 2012, the Company established and incorporated Puma Biotechnology Ltd., a wholly owned subsidiary, for the sole purpose of serving as Puma’s legal representative in the United Kingdom and the European Union in connection with Puma’s clinical trial activity in those countries. Basis of Presentation: The Company is initially focused on developing neratinib for the treatment of patients with human epidermal growth factor receptor type 2, or HER2-positive, breast cancer, HER2 mutated non-small cell lung cancer, HER2-negative breast cancer that has a HER2 mutation and other solid tumors that have an activating mutation in HER2. The Company has reported a net loss of approximately $72.9 million for the three months ended March 31, 2017, and negative cash flows from operations of approximately $36.0 million for the three months ended March 31, 2017. Management believes that the Company will continue to incur net losses and negative net cash flows from operating activities through the drug development process. The accompanying unaudited condensed consolidated interim financial statements have been prepared in accordance with accounting principles generally accepted in the United States of America, or GAAP, pursuant to the rules and regulations of the Securities and Exchange Commission, or the SEC, for interim financial information. Accordingly, the unaudited condensed consolidated financial statements do not include all information and footnotes required by GAAP for complete annual financial statements. In the opinion of management, the accompanying unaudited condensed consolidated interim financial statements reflect all adjustments, consisting of normal recurring adjustments, considered necessary for a fair presentation. Interim operating results are not necessarily indicative of results that may be expected for the year ending December 31, 2017, or for any subsequent period. These unaudited condensed consolidated interim financial statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2016. The condensed consolidated balance sheet at December 31, 2016, has been derived from the audited consolidated financial statements included in the Annual Report on Form 10-K for the fiscal year ended December 31, 2016. The Company has incurred significant operating losses since its inception, which raises substantial doubt about its ability to continue as a going concern. The Company has not yet launched its first commercial product and is currently exploring methods by which to commercialize its product candidates if approved by the United States Food and Drug Administration, or FDA, or the European Medicines Agency, or EMA. These methods may require funding in addition to the cash and cash equivalents and marketable securities totaling approximately $194.0 million available at March 31, 2017. While the consolidated financial statements have been prepared on a going concern basis, the Company continues to remain dependent on its ability to obtain sufficient funding to sustain operation and successfully commercially launch neratinib if approved by the FDA or EMA. While the Company has been successful in raising financing in the past, there can be no assurance that it will be able to do so in the future. The Company’s ability to obtain funding may be adversely impacted by uncertain market conditions, unfavorable decisions of regulatory authorities or adverse clinical trial results. The outcome of these matters cannot be predicted at this time. The Company’s continued operations will depend on its ability to raise funds through various potential sources, such as equity and debt financing. Since its inception through March 31, 2017, the Company’s financing was primarily through public offerings of Company common stock and private equity placements. The Company sold shares of its common stock through an underwritten public offering in October 2016 (see Note 6 to the Annual Report on Form 10-K for the year ended December 31, 2016). As a result, the Company received net proceeds of approximately $161.9 million. The Company may need additional financing until it can achieve profitability, if ever. There can be no assurance that additional capital will be available on favorable terms or at all or that any additional capital that the Company is able to obtain will be sufficient to meet its needs. If it is unable to raise additional capital, the Company could likely be forced to curtail desired development activities, which will delay the development of its product candidates.

Significant Accounting Policies

Significant Accounting Policies	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2—Significant Accounting Policies: The significant accounting policies followed in the preparation of these unaudited condensed consolidated financial statements are as follows: Use of Estimates: The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the balance sheet, and reported amounts of expenses for the period presented. Accordingly, actual results could differ from those estimates. Significant estimates include accrued expenses for the cost of services provided by consultants who manage clinical trials and conduct research and clinical trials on behalf of the Company that are billed on a delayed basis. As the actual costs become known, the Company adjusts its estimated cost in that period. The value of stock-based compensation includes estimates based on future events, which are difficult to predict. It is at least reasonably possible that a change in the estimates used to record accrued expenses and to value the stock-based compensation will occur in the near term. Principles of Consolidation: The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All significant intercompany balances and transactions have been eliminated in consolidation. Cash and Cash Equivalents: The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. Cash equivalents are carried at cost, which approximates fair value. Investment Securities: The Company classifies all investment securities (short term) as available-for-sale, as the sale of such securities may be required prior to maturity to implement management’s strategies. These securities are carried at fair value, with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity until realized. Realized gains and losses from the sale of available-for-sale securities, if any, are determined on a specific identification basis. A decline in the market value of any available-for-sale security below cost that is determined to be other than temporary results in a revaluation of its carrying amount to fair value. The impairment is charged to earnings and a new cost basis for the security is established. Assets Measured at Fair Value on a Recurring Basis: Accounting Standards Codification, or ASC, 820, Fair Value Measurement Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets. Level 3: Valuations derived from valuation techniques in which one or more significant inputs are unobservable. Following are the major categories of assets measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016, using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3) (in thousands): March 31, 2017 Level 1 Level 2 Level 3 Total Cash equivalents $ 96,932 $ — $ — $ 96,932 Commercial paper — 39,828 — 39,828 Marketable securities - corporate bonds — 49,066 — 49,066 $ 96,932 $ 88,894 $ — $ 185,826 December 31, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper — 5,998 — 5,998 Marketable securities - corporate bonds — 28,984 — 28,984 $ 188,543 $ 34,982 $ - $ 223,525 The Company’s investments in commercial paper, corporate bonds and U.S. government securities are exposed to price fluctuations. The fair value measurements for commercial paper, corporate bonds and U.S. government securities are based upon the quoted prices of similar items in active markets multiplied by the number of securities owned. The Company invests its excess cash in commercial paper and debt instruments of corporations. As of March 31, 2017, the Company’s short-term investments had a weighted average maturity of less than one year. The following tables summarize the Company’s short-term investments (in thousands): Maturity Amortized Unrealized Estimated March 31, 2017 (in years) cost Gains Losses fair value Cash equivalents $ 96,932 $ 1 $ — $ 96,933 Commercial paper Less than 1 39,828 — — 39,828 Marketable securities - corporate bonds Less than 1 49,066 3 (54 ) 49,015 $ 185,826 $ 4 $ (54 ) $ 185,776 Maturity Amortized Unrealized Estimated December 31, 2016 (in years) cost Gains Losses fair value Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper Less than 1 5,998 — — 5,998 Marketable securities - corporate bonds Less than 1 28,984 — (13 ) 28,971 $ 223,525 $ — $ (13 ) $ 223,512 Concentration of Risk: Financial instruments, which potentially subject the Company to concentrations of credit risk, principally consist of cash and cash equivalents. The Company’s cash and cash equivalents in excess of the Federal Deposit Insurance Corporation and the Securities Investor Protection Corporation insured limits at March 31, 2017, were approximately $109.4 million. The Company does not believe it is exposed to any significant credit risk due to the quality of the financial instruments in which the money is held. Pursuant to the Company’s internal investment policy, investments must be rated A-1/P-1 or better by Standard and Poor’s Corporation and Moody’s Investors Service at the time of purchase. Property and Equipment: Property and equipment are recorded at cost and depreciated over estimated useful lives ranging from three to five years using the straight-line method. Leasehold improvements are recorded at cost and amortized over the shorter of their useful lives or the term of the lease by use of the straight-line method. Maintenance and repair costs are charged to operations as incurred. The Company assesses the impairment of long-lived assets, primarily property and equipment, whenever events or changes in business circumstances indicate that carrying amounts of the assets may not be fully recoverable. When such events occur, management determines whether there has been impairment by comparing the asset’s carrying value with its fair value, as measured by the anticipated undiscounted net cash flows of the asset. Should impairment exist, the asset is written down to its estimated fair value. The Company has not recognized any impairment losses through March 31, 2017. Research and Development Expenses: Research and development expenses are charged to operations as incurred. The major components of research and development costs include clinical manufacturing costs, clinical trial expenses, consulting and other third-party costs, salaries and employee benefits, stock-based compensation expense, supplies and materials, and allocations of various overhead costs. Clinical trial expenses include, but are not limited to, investigator fees, site costs, comparator drug costs, and clinical research organization, or CRO, costs. In the normal course of business, the Company contracts with third parties to perform various clinical trial activities in the ongoing development of potential products. The financial terms of these agreements are subject to negotiation and variations from contract to contract and may result in uneven payment flows. Payments under the contracts depend on factors such as the achievement of certain events, the successful enrollment of patients and the completion of portions of the clinical trial or similar conditions. The Company’s accruals for clinical trials are based on estimates of the services received and efforts expended pursuant to contracts with numerous clinical trial sites, cooperative groups and CROs. The objective of the Company’s accrual policy is to record expenses in the unaudited condensed consolidated financial statements as the actual services are performed and efforts expended. As actual costs become known, the Company records the actual expenses in that period. In instances where the Company enters into agreements with third parties for clinical trials and other consulting activities, upfront amounts are recorded to prepaid expenses and other in the accompanying unaudited condensed consolidated balance sheets and expensed as services are performed or as the underlying goods are delivered. If the Company does not expect the services to be rendered or goods to be delivered, any remaining capitalized amounts for non-refundable upfront payments are charged to expense immediately. Amounts due under such arrangements may be either fixed fee or fee for service, and may include upfront payments, monthly payments and payments upon the completion of milestones or receipt of deliverables. Costs related to the acquisition of technology rights and patents for which development work is still in process are charged to operations as incurred and considered a component of research and development costs. Stock-Based Compensation: Stock option awards: ASC 718, Compensation — Stock Compensation Performance shares: The performance Restricted stock units: The restricted stock units, or RSUs, Net Loss per Common Share: Basic net loss per common share is computed by dividing net loss applicable to common stockholders by the weighted average number of common shares outstanding during the periods presented as required by ASC 260, Earnings per Share Deferred Rent: The Company has entered into operating lease agreements for its corporate offices in Los Angeles and South San Francisco that contain provisions for future rent increases, leasehold improvement allowances and rent abatements. The Company records monthly rent expense equal to the total of the payments due over the lease term, divided by the number of months of the lease term. The difference between the rent expense recorded and the amount paid is credited or charged to deferred rent, which is reflected as a separate line item in the accompanying unaudited condensed consolidated balance sheets. Additionally, the Company recorded as deferred rent the cost of the leasehold improvements paid by the landlord, which is amortized on a straight-line basis over the term of the lease. Issuance of Common Stock Upon Exercise of Stock Option Grants: When a stock option grant is exercised, the Company notifies its transfer agent to release the required number of shares of common stock from the reserve for the Company’s 2011 Incentive Award Plan, as amended, or the 2011 Plan. The Company records the transaction for the cash received and the issuance of common shares. Should there be a delay in the cash receipts due to the settlement period, the Company records a receivable from the exercise of an option as part of stockholders’ equity on the unaudited condensed consolidated balance sheet. Recently Issued Accounting Standards: In May 2014, the Financial Accounting Standards Board (FASB) issued a new accounting standard that amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB has subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The new revenue recognition standard and clarifying standards are effective for interim and annual periods beginning on January 1, 2018, but could have been adopted early beginning January 1, 2017. The new standards are required to be adopted using either a full retrospective or a modified retrospective approach. The Company expects to adopt this standard beginning in 2017 if and when it begins to generate revenue. The Company continues to review the impact that this new standard will have on collaborations and license arrangements, as well as its consolidated financial statements. As the Compay completes its assessment, the Company is also identifying and preparing to implement changes to its accounting policies, business processes, and internal controls to support the new accounting and disclosure requirements. In February 2016, the FASB issued Accounting Standards Update, or ASU, No. 2016-02, Leases In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation: Improvements to Employee Share-Based Payment Accounting, In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows Topic 230 : Classification of Certain Cash Receipts and Cash Payments a consensus of the Emerging Issues Task Force In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows Topic 230 Restricted Cash In January 2017 Business Combinations (Topic 805): Clarifying the Definition of a Business

Prepaid Expenses and Other

Prepaid Expenses and Other	3 Months Ended
	Mar. 31, 2017
Banking And Thrift [Abstract]
Prepaid Expenses and Other	Note 3—Prepaid Expenses and Other: The Company, from time to time, makes payments to certain vendors for which the service relates to future periods. In these cases, the Company classifies these expenses as prepaid and other and amortizes those payments over the period for which the services relate. In some cases, the vendors require an upfront payment to be applied to the final invoices under the agreements. In those cases, if the contract extends beyond the period of one year, the prepayments are classified as long-term. Prepaid expenses and other consisted of the following (in thousands): March 31, 2017 December 31, 2016 Current: CRO services $ 7,285 $ 3,471 Other clinical development 1,109 1,069 Insurance 865 1,159 Other 1,395 1,299 10,654 6,998 Long-term: CRO services 1,152 5,077 Other clinical development 1,077 1,243 Insurance 28 40 Other 417 486 2,674 6,846 Totals $ 13,328 $ 13,844

Property and Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	Note 4—Property and Equipment: Property and equipment consisted of the following (in thousands): Property and Equipment: March 31, 2017 December 31, 2016 Leasehold improvements $ 3,878 $ 3,878 Computer equipment 1,890 1,822 Telephone equipment 262 256 Furniture and fixtures 2,196 2,146 8,226 8,102 Less: accumulated depreciation and amortization (3,226 ) (2,949 ) Totals $ 5,000 $ 5,153

Accrued Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2017
Payables And Accruals [Abstract]
Accrued Expenses	Note 5—Accrued Expenses: Accrued expenses consisted of the following (in thousands): March 31, 2017 December 31, 2016 Accrued CRO services $ 7,864 $ 6,609 Accrued other clinical development 6,225 7,015 Accrued legal fees 1,579 706 Accrued compensation 3,982 3,058 Other 110 38 Totals $ 19,760 $ 17,426 Accrued CRO services represent the Company’s estimate of such costs and will be adjusted in the period the actual costs become known. Accrued compensation includes estimated bonus and earned but unused vacation for full-time employees. When actual performance bonuses are paid out to employees, the bonus expense will be adjusted to reflect the actual expense for the year. Additionally, vacation is accrued at the rate the employee earns vacation and reduced as vacation is used by the employee.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Stockholders' Equity	Note 6—Stockholders’ Equity: Stock-Based Compensation: The Company’s 2011 Plan was adopted by the Board of Directors on September 15, 2011. Pursuant to the 2011 Plan, the Company may grant incentive stock options, nonqualified stock options and restricted stock units, as well as other forms of equity-based compensation. Incentive stock options may be granted only to employees, while consultants, employees, officers and directors are eligible for the grant of nonqualified options and restricted stock units under the 2011 Plan. The maximum term of stock options granted under the 2011 Plan is 10 years. The exercise price of incentive stock options granted under the 2011 Plan must be at least equal to the fair value of such shares on the date of grant. Through March 31, 2017, a total of 10,529,412 shares of the Company’s common stock have been reserved for issuance under the 2011 Plan. Employee stock-based compensation for the three months ended March 31, 2017 and 2016 were as follows (in thousands, except share and per share data): Three Months Ended March 31, 2017 2016 Stock-based compensation: Options - Research and development, or R&D $ 20,356 $ 23,556 General and administrative, or G&A 6,189 5,882 Performance shares - R&D — 72 Restricted stock units - R&D 2,124 — G&A 1,095 — Total stock-based compensation expense $ 29,764 $ 29,510 Stock Options: The fair value of options granted to employees was estimated using the Black-Scholes Option Pricing Method (see Note 2—Significant Accounting Policies) with the following weighted-average assumptions used during the three months ended March 31, 2017 and 2016: 2017 2016 Dividend yield 0.0 % 0.0 % Expected volatility 70.1 % 66.1 % Risk-free interest rate 2.0 % 1.6 % Expected life in years 5.85 5.85 Activity with respect to options granted under the 2011 Plan is summarized as follows: Shares Weighted Average Exercise Price Weighted Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2016 6,578,522 $ 87.52 8.0 $ 18,442 Granted 459,375 $ 36.46 Forfeited (60,498 ) $ 66.73 Exercised (33,468 ) $ 21.44 $ 481 Expired (28,066 ) $ 125.43 Outstanding at March 31, 2017 6,915,865 $ 84.47 7.9 $ 26,584 Nonvested at March 31, 2017 3,136,492 $ 69.39 9.1 $ 2,329 Exercisable at March 31, 2017 3,779,373 $ 97.16 6.9 $ 24,255 At March 31, 2017, total estimated unrecognized employee compensation cost related to nonvested stock options and restricted stock units granted prior to that date were approximately $114.6 million and $23.9 million, respectively. These unrecognized expenses are expected to be recognized over a weighted-average period of 1.7 years for stock options and 2.3 years for restricted stock units. The weighted-average grant date fair value of options granted during the three months ended March 31, 2017 and 2016, were $22.86 per share and $36.28 per share, respectively. Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2016 3,106,083 $ 47.78 Granted 459,375 22.86 Vested/Issued (368,468 ) 72.27 Forfeited (60,498 ) 39.80 Nonvested shares at March 31, 2017 3,136,492 41.50 Restricted stock units: On October 14, 2016, restricted stock units were awarded to certain employees. These restricted stock units vest over three years in six equal installments on each six month anniversary of the vesting start date, July 19, 2016. Weighted Average Grant-Date Restricted stock units Shares Fair Value Nonvested shares at December 31, 2016 630,508 $ 54.35 Granted — — Vested/Issued (106,800 ) 54.35 Forfeited (6,747 ) 54.35 Nonvested shares at March 31, 2017 516,961 $ 54.35

401(k) Savings Plan

401(k) Savings Plan	3 Months Ended
	Mar. 31, 2017
Postemployment Benefits [Abstract]
401(k) Savings Plan	Note 7—401(k) Savings Plan: During 2012, the Company adopted a 401(k) savings plan for the benefit of its employees. The Company is required to make matching contributions to the 401(k) plan equal to 100% of the first 3% of wages deferred by each participating employee and 50% on the next 2% of wages deferred by each participating employee. The Company incurred expenses for employer matching contributions of approximately $0.2 million and $0.3 million for the three months ended March 31, 2017 and 2016, respectively.

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 8—Commitments and Contingencies: The Company is involved in various lawsuits, claims and other legal matters from time to time that arise in the ordinary course of conducting business. The Company records a liability when a particular contingency is probable and estimable. The Company has not accrued for any contingency at March 31, 2017, as the Company does not consider any contingency to be probable or estimable. The Company faces contingencies that are reasonably possible to occur; however, they cannot currently be estimated. While complete assurance cannot be given to the outcome of these proceedings, management does not currently believe that any of these matters, individually or in the aggregate, will have a material adverse effect on the Company’s financial condition, liquidity or results of operations.

Significant Accounting Polici16

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates: The preparation of consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect reported amounts of assets and liabilities, and disclosure of contingent assets and liabilities at the date of the balance sheet, and reported amounts of expenses for the period presented. Accordingly, actual results could differ from those estimates. Significant estimates include accrued expenses for the cost of services provided by consultants who manage clinical trials and conduct research and clinical trials on behalf of the Company that are billed on a delayed basis. As the actual costs become known, the Company adjusts its estimated cost in that period. The value of stock-based compensation includes estimates based on future events, which are difficult to predict. It is at least reasonably possible that a change in the estimates used to record accrued expenses and to value the stock-based compensation will occur in the near term.
Principles of Consolidation	Principles of Consolidation: The unaudited condensed consolidated financial statements include the accounts of the Company and its wholly owned subsidiary. All significant intercompany balances and transactions have been eliminated in consolidation.
Cash and Cash Equivalents	Cash and Cash Equivalents: The Company considers all highly liquid investments with original maturities of three months or less to be cash equivalents. Cash equivalents are carried at cost, which approximates fair value.
Investment Securities	Investment Securities: The Company classifies all investment securities (short term) as available-for-sale, as the sale of such securities may be required prior to maturity to implement management’s strategies. These securities are carried at fair value, with the unrealized gains and losses reported as a component of accumulated other comprehensive income (loss) in stockholders’ equity until realized. Realized gains and losses from the sale of available-for-sale securities, if any, are determined on a specific identification basis. A decline in the market value of any available-for-sale security below cost that is determined to be other than temporary results in a revaluation of its carrying amount to fair value. The impairment is charged to earnings and a new cost basis for the security is established.
Assets Measured at Fair Value on a Recurring Basis	Assets Measured at Fair Value on a Recurring Basis: Accounting Standards Codification, or ASC, 820, Fair Value Measurement Level 1: Quoted prices in active markets for identical assets or liabilities. Level 2: Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets. Level 3: Valuations derived from valuation techniques in which one or more significant inputs are unobservable. Following are the major categories of assets measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016, using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3) (in thousands): March 31, 2017 Level 1 Level 2 Level 3 Total Cash equivalents $ 96,932 $ — $ — $ 96,932 Commercial paper — 39,828 — 39,828 Marketable securities - corporate bonds — 49,066 — 49,066 $ 96,932 $ 88,894 $ — $ 185,826 December 31, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper — 5,998 — 5,998 Marketable securities - corporate bonds — 28,984 — 28,984 $ 188,543 $ 34,982 $ - $ 223,525 The Company’s investments in commercial paper, corporate bonds and U.S. government securities are exposed to price fluctuations. The fair value measurements for commercial paper, corporate bonds and U.S. government securities are based upon the quoted prices of similar items in active markets multiplied by the number of securities owned. The Company invests its excess cash in commercial paper and debt instruments of corporations. As of March 31, 2017, the Company’s short-term investments had a weighted average maturity of less than one year. The following tables summarize the Company’s short-term investments (in thousands): Maturity Amortized Unrealized Estimated March 31, 2017 (in years) cost Gains Losses fair value Cash equivalents $ 96,932 $ 1 $ — $ 96,933 Commercial paper Less than 1 39,828 — — 39,828 Marketable securities - corporate bonds Less than 1 49,066 3 (54 ) 49,015 $ 185,826 $ 4 $ (54 ) $ 185,776 Maturity Amortized Unrealized Estimated December 31, 2016 (in years) cost Gains Losses fair value Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper Less than 1 5,998 — — 5,998 Marketable securities - corporate bonds Less than 1 28,984 — (13 ) 28,971 $ 223,525 $ — $ (13 ) $ 223,512
Concentration of Risk	Concentration of Risk: Financial instruments, which potentially subject the Company to concentrations of credit risk, principally consist of cash and cash equivalents. The Company’s cash and cash equivalents in excess of the Federal Deposit Insurance Corporation and the Securities Investor Protection Corporation insured limits at March 31, 2017, were approximately $109.4 million. The Company does not believe it is exposed to any significant credit risk due to the quality of the financial instruments in which the money is held. Pursuant to the Company’s internal investment policy, investments must be rated A-1/P-1 or better by Standard and Poor’s Corporation and Moody’s Investors Service at the time of purchase.
Property and Equipment	Property and Equipment: Property and equipment are recorded at cost and depreciated over estimated useful lives ranging from three to five years using the straight-line method. Leasehold improvements are recorded at cost and amortized over the shorter of their useful lives or the term of the lease by use of the straight-line method. Maintenance and repair costs are charged to operations as incurred. The Company assesses the impairment of long-lived assets, primarily property and equipment, whenever events or changes in business circumstances indicate that carrying amounts of the assets may not be fully recoverable. When such events occur, management determines whether there has been impairment by comparing the asset’s carrying value with its fair value, as measured by the anticipated undiscounted net cash flows of the asset. Should impairment exist, the asset is written down to its estimated fair value. The Company has not recognized any impairment losses through March 31, 2017.
Research and Development Expenses	Research and Development Expenses: Research and development expenses are charged to operations as incurred. The major components of research and development costs include clinical manufacturing costs, clinical trial expenses, consulting and other third-party costs, salaries and employee benefits, stock-based compensation expense, supplies and materials, and allocations of various overhead costs. Clinical trial expenses include, but are not limited to, investigator fees, site costs, comparator drug costs, and clinical research organization, or CRO, costs. In the normal course of business, the Company contracts with third parties to perform various clinical trial activities in the ongoing development of potential products. The financial terms of these agreements are subject to negotiation and variations from contract to contract and may result in uneven payment flows. Payments under the contracts depend on factors such as the achievement of certain events, the successful enrollment of patients and the completion of portions of the clinical trial or similar conditions. The Company’s accruals for clinical trials are based on estimates of the services received and efforts expended pursuant to contracts with numerous clinical trial sites, cooperative groups and CROs. The objective of the Company’s accrual policy is to record expenses in the unaudited condensed consolidated financial statements as the actual services are performed and efforts expended. As actual costs become known, the Company records the actual expenses in that period. In instances where the Company enters into agreements with third parties for clinical trials and other consulting activities, upfront amounts are recorded to prepaid expenses and other in the accompanying unaudited condensed consolidated balance sheets and expensed as services are performed or as the underlying goods are delivered. If the Company does not expect the services to be rendered or goods to be delivered, any remaining capitalized amounts for non-refundable upfront payments are charged to expense immediately. Amounts due under such arrangements may be either fixed fee or fee for service, and may include upfront payments, monthly payments and payments upon the completion of milestones or receipt of deliverables. Costs related to the acquisition of technology rights and patents for which development work is still in process are charged to operations as incurred and considered a component of research and development costs.
Stock-Based Compensation	Stock-Based Compensation: Stock option awards: ASC 718, Compensation — Stock Compensation Performance shares: The performance Restricted stock units: The restricted stock units, or RSUs,
Net Loss per Common Share	Net Loss per Common Share: Basic net loss per common share is computed by dividing net loss applicable to common stockholders by the weighted average number of common shares outstanding during the periods presented as required by ASC 260, Earnings per Share
Deferred Rent	Deferred Rent: The Company has entered into operating lease agreements for its corporate offices in Los Angeles and South San Francisco that contain provisions for future rent increases, leasehold improvement allowances and rent abatements. The Company records monthly rent expense equal to the total of the payments due over the lease term, divided by the number of months of the lease term. The difference between the rent expense recorded and the amount paid is credited or charged to deferred rent, which is reflected as a separate line item in the accompanying unaudited condensed consolidated balance sheets. Additionally, the Company recorded as deferred rent the cost of the leasehold improvements paid by the landlord, which is amortized on a straight-line basis over the term of the lease.
Issuance of Common Stock Upon Exercise of Stock Option Grants	Issuance of Common Stock Upon Exercise of Stock Option Grants: When a stock option grant is exercised, the Company notifies its transfer agent to release the required number of shares of common stock from the reserve for the Company’s 2011 Incentive Award Plan, as amended, or the 2011 Plan. The Company records the transaction for the cash received and the issuance of common shares. Should there be a delay in the cash receipts due to the settlement period, the Company records a receivable from the exercise of an option as part of stockholders’ equity on the unaudited condensed consolidated balance sheet.
Recently Issued Accounting Standards	Recently Issued Accounting Standards: In May 2014, the Financial Accounting Standards Board (FASB) issued a new accounting standard that amends the guidance for the recognition of revenue from contracts with customers to transfer goods and services. The FASB has subsequently issued additional, clarifying standards to address issues arising from implementation of the new revenue recognition standard. The new revenue recognition standard and clarifying standards are effective for interim and annual periods beginning on January 1, 2018, but could have been adopted early beginning January 1, 2017. The new standards are required to be adopted using either a full retrospective or a modified retrospective approach. The Company expects to adopt this standard beginning in 2017 if and when it begins to generate revenue. The Company continues to review the impact that this new standard will have on collaborations and license arrangements, as well as its consolidated financial statements. As the Compay completes its assessment, the Company is also identifying and preparing to implement changes to its accounting policies, business processes, and internal controls to support the new accounting and disclosure requirements. In February 2016, the FASB issued Accounting Standards Update, or ASU, No. 2016-02, Leases In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation: Improvements to Employee Share-Based Payment Accounting, In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows Topic 230 : Classification of Certain Cash Receipts and Cash Payments a consensus of the Emerging Issues Task Force In November 2016, the FASB issued ASU No. 2016-18, Statement of Cash Flows Topic 230 Restricted Cash In January 2017 Business Combinations (Topic 805): Clarifying the Definition of a Business

Significant Accounting Polici17

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2017
Accounting Policies [Abstract]
Assets Measured at Fair Value on Recurring Basis	Following are the major categories of assets measured at fair value on a recurring basis as of March 31, 2017 and December 31, 2016, using quoted prices in active markets for identical assets (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3) (in thousands): March 31, 2017 Level 1 Level 2 Level 3 Total Cash equivalents $ 96,932 $ — $ — $ 96,932 Commercial paper — 39,828 — 39,828 Marketable securities - corporate bonds — 49,066 — 49,066 $ 96,932 $ 88,894 $ — $ 185,826 December 31, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper — 5,998 — 5,998 Marketable securities - corporate bonds — 28,984 — 28,984 $ 188,543 $ 34,982 $ - $ 223,525
Summary of Short-term Investments	The following tables summarize the Company’s short-term investments (in thousands): Maturity Amortized Unrealized Estimated March 31, 2017 (in years) cost Gains Losses fair value Cash equivalents $ 96,932 $ 1 $ — $ 96,933 Commercial paper Less than 1 39,828 — — 39,828 Marketable securities - corporate bonds Less than 1 49,066 3 (54 ) 49,015 $ 185,826 $ 4 $ (54 ) $ 185,776 Maturity Amortized Unrealized Estimated December 31, 2016 (in years) cost Gains Losses fair value Cash equivalents $ 188,543 $ — $ — $ 188,543 Commercial paper Less than 1 5,998 — — 5,998 Marketable securities - corporate bonds Less than 1 28,984 — (13 ) 28,971 $ 223,525 $ — $ (13 ) $ 223,512

Prepaid Expenses and Other (Tab

Prepaid Expenses and Other (Tables)	3 Months Ended
	Mar. 31, 2017
Banking And Thrift [Abstract]
Components of Prepaid Expenses and Other	Prepaid expenses and other consisted of the following (in thousands): March 31, 2017 December 31, 2016 Current: CRO services $ 7,285 $ 3,471 Other clinical development 1,109 1,069 Insurance 865 1,159 Other 1,395 1,299 10,654 6,998 Long-term: CRO services 1,152 5,077 Other clinical development 1,077 1,243 Insurance 28 40 Other 417 486 2,674 6,846 Totals $ 13,328 $ 13,844

Property and Equipment (Tables)

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2017
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following (in thousands): Property and Equipment: March 31, 2017 December 31, 2016 Leasehold improvements $ 3,878 $ 3,878 Computer equipment 1,890 1,822 Telephone equipment 262 256 Furniture and fixtures 2,196 2,146 8,226 8,102 Less: accumulated depreciation and amortization (3,226 ) (2,949 ) Totals $ 5,000 $ 5,153

Accrued Expenses (Tables)

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2017
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses consisted of the following (in thousands): March 31, 2017 December 31, 2016 Accrued CRO services $ 7,864 $ 6,609 Accrued other clinical development 6,225 7,015 Accrued legal fees 1,579 706 Accrued compensation 3,982 3,058 Other 110 38 Totals $ 19,760 $ 17,426

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2017
Equity [Abstract]
Employee Stock-based Compensation	Employee stock-based compensation for the three months ended March 31, 2017 and 2016 were as follows (in thousands, except share and per share data): Three Months Ended March 31, 2017 2016 Stock-based compensation: Options - Research and development, or R&D $ 20,356 $ 23,556 General and administrative, or G&A 6,189 5,882 Performance shares - R&D — 72 Restricted stock units - R&D 2,124 — G&A 1,095 — Total stock-based compensation expense $ 29,764 $ 29,510
Fair Value Options Weighted-Average Assumptions	The fair value of options granted to employees was estimated using the Black-Scholes Option Pricing Method (see Note 2—Significant Accounting Policies) with the following weighted-average assumptions used during the three months ended March 31, 2017 and 2016: 2017 2016 Dividend yield 0.0 % 0.0 % Expected volatility 70.1 % 66.1 % Risk-free interest rate 2.0 % 1.6 % Expected life in years 5.85 5.85
Activity with Respect to Options Granted	Activity with respect to options granted under the 2011 Plan is summarized as follows: Shares Weighted Average Exercise Price Weighted Contractual Term (years) Aggregate Intrinsic Value (in thousands) Outstanding at December 31, 2016 6,578,522 $ 87.52 8.0 $ 18,442 Granted 459,375 $ 36.46 Forfeited (60,498 ) $ 66.73 Exercised (33,468 ) $ 21.44 $ 481 Expired (28,066 ) $ 125.43 Outstanding at March 31, 2017 6,915,865 $ 84.47 7.9 $ 26,584 Nonvested at March 31, 2017 3,136,492 $ 69.39 9.1 $ 2,329 Exercisable at March 31, 2017 3,779,373 $ 97.16 6.9 $ 24,255
Stock Options	The weighted-average grant date fair value of options granted during the three months ended March 31, 2017 and 2016, were $22.86 per share and $36.28 per share, respectively. Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2016 3,106,083 $ 47.78 Granted 459,375 22.86 Vested/Issued (368,468 ) 72.27 Forfeited (60,498 ) 39.80 Nonvested shares at March 31, 2017 3,136,492 41.50
Restricted Stock Units	Weighted Average Grant-Date Restricted stock units Shares Fair Value Nonvested shares at December 31, 2016 630,508 $ 54.35 Granted — — Vested/Issued (106,800 ) 54.35 Forfeited (6,747 ) 54.35 Nonvested shares at March 31, 2017 516,961 $ 54.35

Business and Basis of Present22

Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended
	Oct. 31, 2016	Mar. 31, 2017	Mar. 31, 2016
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net loss		$ (72,865)	$ (70,972)
Net cash used in operating activities		(36,042)	$ (35,028)
Cash and cash equivalents and marketable securities		$ 194,000
Underwritten Public Offering
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceeds from issuance of common stock	$ 161,900

Assets Measured at Fair Value o

Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 96,932	$ 188,543
Total	185,826	223,525
Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	39,828	5,998
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	49,066	28,984
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	96,932	188,543
Total	96,932	188,543
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	88,894	34,982
Level 2 | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	39,828	5,998
Level 2 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 49,066	$ 28,984

Significant Accounting Polici24

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Significant Accounting Policies [Line Items]
Cash and cash equivalents in excess of insured limits	$ 109.4
Warrants
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share	2,116,250	2,116,250
Performance Awards
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share		9,469
Restricted Stock Units
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share	516,961
Performance Awards
Significant Accounting Policies [Line Items]
Shares, vesting period	3 years
Employee Stock Option
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share	6,915,865	5,675,393
Maximum
Significant Accounting Policies [Line Items]
Weighted average maturity period of short-term investments	1 year
Property and equipment, useful lives	5 years
Minimum
Significant Accounting Policies [Line Items]
Property and equipment, useful lives	3 years

Summary of Short-term Investmen

Summary of Short-term Investments (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	$ 185,826	$ 223,525
Unrealized Gains	4
Unrealized Losses	(54)	(13)
Estimated fair value	185,776	223,512
Cash Equivalents
Schedule Of Available For Sale Securities [Line Items]
Amortized cost	96,932	188,543
Unrealized Gains	1
Estimated fair value	$ 96,933	$ 188,543
Commercial paper
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	Less than 1	Less than 1
Amortized cost	$ 39,828	$ 5,998
Estimated fair value	$ 39,828	$ 5,998
Corporate bonds
Schedule Of Available For Sale Securities [Line Items]
Maturity (in years)	Less than 1	Less than 1
Amortized cost	$ 49,066	$ 28,984
Unrealized Gains	3
Unrealized Losses	(54)	(13)
Estimated fair value	$ 49,015	$ 28,971

Components of Prepaid Expenses

Components of Prepaid Expenses and Other (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	$ 10,654	$ 6,998
Prepaid expenses and other, long-term	2,674	6,846
Totals	13,328	13,844
CRO services
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	7,285	3,471
Prepaid expenses and other, long-term	1,152	5,077
Other clinical development
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	1,109	1,069
Prepaid expenses and other, long-term	1,077	1,243
Insurance
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	865	1,159
Prepaid expenses and other, long-term	28	40
Other
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	1,395	1,299
Prepaid expenses and other, long-term	$ 417	$ 486

Property and Equipment (Detail)

Property and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 8,226	$ 8,102
Less: accumulated depreciation and amortization	(3,226)	(2,949)
Totals	5,000	5,153
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	3,878	3,878
Computer Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	1,890	1,822
Telephone Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	262	256
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,196	$ 2,146

Accrued Expenses (Detail)

Accrued Expenses (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued CRO services	$ 7,864	$ 6,609
Accrued other clinical development	6,225	7,015
Accrued legal fees	1,579	706
Accrued compensation	3,982	3,058
Other	110	38
Totals	$ 19,760	$ 17,426

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Oct. 14, 2016	Mar. 31, 2017	Mar. 31, 2016
Stockholders Equity Note [Line Items]
Weighted-average grant date fair value of options granted		$ 22.86	$ 36.28
Non Vested Stock Options
Stockholders Equity Note [Line Items]
Estimated unrecognized employee compensation cost related to non-vested stock options granted		$ 114.6
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition		1 year 8 months 12 days
Restricted Stock Units
Stockholders Equity Note [Line Items]
Estimated unrecognized employee compensation cost related to non-vested stock options granted		$ 23.9
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition		2 years 3 months 18 days
Shares vesting period	3 years
Shares vesting start date	Jul. 19, 2016
Shares vesting description	These restricted stock units vest over three years in six equal installments on each six month anniversary of the vesting start date, July 19, 2016.
2011 Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance		10,529,412
Maximum | 2011 Plan
Stockholders Equity Note [Line Items]
Stock options granted, term		10 years

Employee Stock-based Compensati

Employee Stock-based Compensation (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 29,764	$ 29,510
Employee Stock Option | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	20,356	23,556
Employee Stock Option | General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	6,189	5,882
Performance Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense		$ 72
Restricted Stock Units | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	2,124
Restricted Stock Units | General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Total share-based compensation expense	$ 1,095

Fair Value Options Weighted-Ave

Fair Value Options Weighted-Average Assumptions (Detail) - Employee Stock Option	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility	70.10%	66.10%
Risk-free interest rate	2.00%	1.60%
Expected life in years	5 years 10 months 6 days	5 years 10 months 6 days

Activity with Respect to Option

Activity with Respect to Options Granted (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Shares
Beginning balance, shares	6,578,522
Granted, shares	459,375
Forfeited, shares	(60,498)
Exercised, shares	(33,468)
Expired, shares	(28,066)
Ending balance, shares	6,915,865	6,578,522
Nonvested, shares	3,136,492	3,106,083
Exercisable, shares	3,779,373
Weighted Average Exercise Price
Beginning Balance, Weighted Average Exercise Price	$ 87.52
Granted, Weighted Average Exercise Price	36.46
Forfeited, Weighted Average Exercise Price	66.73
Exercised, Weighted Average Exercise Price	21.44
Expired, Weighted Average Exercise Price	125.43
Ending Balance, Weighted Average Exercise Price	84.47	$ 87.52
Nonvested, Weighted Average Exercise Price	69.39
Exercisable, Weighted Average Exercise Price	$ 97.16
Weighted Average Remaining Contractual Term (years)
Weighted Average Remaining Contractual Term (years)	7 years 10 months 24 days	8 years
Nonvested, Weighted Average Remaining Contractual Term (years)	9 years 1 month 6 days
Exercisable, Weighted Average Remaining Contractual Term (years)	6 years 10 months 24 days
Aggregate Intrinsic Value
Beginning balance, Aggregate Intrinsic Value	$ 18,442
Exercised, Aggregate Intrinsic Value	481
Ending balance, Aggregate Intrinsic Value	26,584	$ 18,442
Nonvested, Aggregate Intrinsic Value	2,329
Exercisable, Aggregate Intrinsic Value	$ 24,255

Stock Options (Detail)

Stock Options (Detail) - $ / shares	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Shares
Beginning balance, shares	3,106,083
Granted, shares	459,375
Vested/Issued, shares	(368,468)
Forfeited, shares	(60,498)
Ending balance, shares	3,136,492
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value	$ 47.78
Granted, Weighted Average Grant-Date Fair Value	22.86	$ 36.28
Vested/Issued, Weighted Average Grant-Date Fair Value	72.27
Forfeited, Weighted Average Grant-Date Fair Value	39.80
Ending balance, Weighted Average Grant-Date Fair Value	$ 41.50

Restricted Stock Units (Detail)

Restricted Stock Units (Detail) - Restricted Stock Units	3 Months Ended
	Mar. 31, 2017$ / sharesshares
Shares
Beginning balance, shares | shares	630,508
Granted, shares | shares	0
Vested/Issued, shares | shares	(106,800)
Forfeited, shares | shares	(6,747)
Ending balance, shares | shares	516,961
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value | $ / shares	$ 54.35
Granted, Weighted Average Grant-Date Fair Value | $ / shares	0
Vested/Issued, Weighted Average Grant-Date Fair Value | $ / shares	54.35
Forfeited, Weighted Average Grant-Date Fair Value | $ / shares	54.35
Ending balance, Weighted Average Grant-Date Fair Value | $ / shares	$ 54.35

401(K) Savings Plan - Additiona

401(K) Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution expenses	$ 0.2	$ 0.3
First 3% of each Participant's Contributions
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions to the 401(k)plan	100.00%
Second 2% of each Participant's Contributions
Defined Benefit Plan Disclosure [Line Items]
Company's matching contributions to the 401(k)plan	50.00%