Puma Biotechnology (PBYI) 10-Q 9 Nov 16 2016 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2016	Nov. 04, 2016
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2016
Document Fiscal Year Focus	2,016
Document Fiscal Period Focus	Q3
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		36,818,092

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 52,541	$ 31,569
Marketable securities	56,390	184,320
Prepaid expenses and other, current	7,290	7,660
Receivables	1,179
Total current assets	117,400	223,549
Property and equipment, net	5,180	2,383
Prepaid expenses and other, long-term	7,135	9,597
Restricted cash	4,316	4,313
Total assets	134,031	239,842
Current liabilities:
Accounts payable	20,878	17,803
Accrued expenses	16,721	14,639
Total current liabilities	37,599	32,442
Deferred rent	5,284	1,393
Total liabilities	42,883	33,835
Commitments and contingencies
Stockholders' equity:
Common stock - $.0001 par value; 100,000,000 shares authorized; 32,503,092 shares issued and outstanding at September 30, 2016 and 32,466,842 issued and outstanding at December 31, 2015	3	3
Additional paid-in capital	814,992	726,651
Accumulated other comprehensive income (loss)	3	(147)
Accumulated deficit	(723,850)	(520,500)
Total stockholders' equity	91,148	206,007
Total liabilities and stockholders' equity	$ 134,031	$ 239,842

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2016	Dec. 31, 2015
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	32,503,092	32,466,842
Common stock, shares outstanding	32,503,092	32,466,842

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Operating expenses:
General and administrative	$ 14,022	$ 8,809	$ 37,326	$ 22,212
Research and development	51,977	51,924	166,400	156,033
Totals	65,999	60,733	203,726	178,245
Loss from operations	(65,999)	(60,733)	(203,726)	(178,245)
Other (expenses) income:
Interest income	214	318	756	654
Other (expenses) income	4	(2)	(380)	26
Totals	218	316	376	680
Net loss	(65,781)	(60,417)	(203,350)	(177,565)
Net loss applicable to common stock	$ (65,781)	$ (60,417)	$ (203,350)	$ (177,565)
Net loss per common share—basic and diluted	$ (2.02)	$ (1.87)	$ (6.26)	$ (5.55)
Weighted-average common shares outstanding—basic and diluted	32,497,168	32,303,203	32,489,584	32,018,869

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (65,781)	$ (60,417)	$ (203,350)	$ (177,565)
Other comprehensive loss
Unrealized gain (loss) on available-for-sale securities	(28)	149	150	63
Comprehensive loss	$ (65,809)	$ (60,268)	$ (203,200)	$ (177,502)

Condensed Consolidated Stateme6

Condensed Consolidated Statement of Stockholders' Equity (Unaudited) - 9 months ended Sep. 30, 2016 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning Balance at Dec. 31, 2015	$ 206,007	$ 3	$ 726,651	$ (147)	$ (520,500)
Beginning Balance (in shares) at Dec. 31, 2015	32,466,842	32,466,842
Stock-based compensation	$ 87,990		87,990
Exercises of stock options	$ 351		351
Exercises of stock options (in shares)	36,250	36,250
Unrealized gain on available-for-sale securities	$ 150			150
Net loss	(203,350)				(203,350)
Ending Balance at Sep. 30, 2016	$ 91,148	$ 3	$ 814,992	$ 3	$ (723,850)
Ending Balance (in shares) at Sep. 30, 2016	32,503,092	32,503,092

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating activities:
Net loss	$ (203,350)	$ (177,565)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	565	568
Build-out allowance received from landlord	2,997	179
Stock-based compensation	87,990	73,254
Disposal of leasehold improvements	368
Changes in operating assets and liabilities:
Receivables	(1,179)	1,760
Prepaid expenses and other	2,832	(706)
Accounts payable	3,075	(5,214)
Accrued expenses	2,082	(13,896)
Accrual of deferred rent	3,891	183
Net cash used in operating activities	(100,729)	(121,437)
Investing activities:
Purchase of property and equipment	(3,730)	(943)
Restricted cash	(3)	(3,097)
Expenditures for leasehold improvements	(2,997)	(179)
Purchase of available-for-sale securities	(81,794)	(211,783)
Sale/maturity of available-for-sale securities	209,874	90,457
Net cash provided by (used in) investing activities	121,350	(125,545)
Financing activities:
Net proceeds from issuance of common stock		205,133
Net proceeds from exercise of options	351	26,908
Net cash provided by financing activities	351	232,041
Net increase in cash and cash equivalents	20,972	(14,941)
Cash and cash equivalents, beginning of period	31,569	38,539
Cash and cash equivalents, end of period	$ 52,541	$ 23,598

Business and Basis of Presentat

Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2016
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 $65.8 million and $203.4 million for the three and nine months ended September 30, 2016, respectively, and negative cash flows from operations of approximately $100.7 million for the nine months ended September 30, 2016. 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, 2016, 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, 2015. The condensed consolidated balance sheet at December 31, 2015, 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, 2015. The Company has spent and expects to continue to spend substantial amounts in connection with implementing its business strategy, including planned product development efforts, clinical trials and preparation for commercialization. The Company’s continued operations will depend on its ability to raise funds through various potential sources, such as equity and debt financing. Through September 30, 2016, the Company’s financing was primarily through public offerings of Company common stock and private equity placements. Given the current and desired pace of clinical development of its product candidates and efforts to prepare for commercialization, management believes that the cash and cash equivalents and marketable securities on hand at September 30, 2016, together with the approximately $161.8 million in net proceeds the Company received from the issuance and sale of its common stock in October 2016, are sufficient to fund the Company’s operations for the next 12 to 18 months. 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	9 Months Ended
	Sep. 30, 2016
Accounting Policies [Abstract]
Significant Accounting Policies	Note 2—Significant Accounting Policies: The significant accounting policies followed in the preparation of these 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 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 and long 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. Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the straight-line method. Interest income is recognized when earned. 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 September 30, 2016 and December 31, 2015, 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): September 30, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 40,457 $ — $ — $ 40,457 Commercial paper — 15,368 — 15,368 Marketable securities - U.S. government — 6,022 — 6,022 Marketable securities - corporate bonds — 35,000 — 35,000 $ 40,457 $ 56,390 $ — $ 96,847 December 31, 2015 Level 1 Level 2 Level 3 Total Cash equivalents $ 29,166 $ — $ — $ 29,166 Commercial paper — 2,996 — 2,996 Marketable securities - U.S. government — 11,500 — 11,500 Marketable securities - corporate bonds — 169,824 — 169,824 $ 29,166 $ 184,320 $ — $ 213,486 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, exclusive of any transaction costs and without any adjustments to reflect discounts that may be applied to selling a large block of securities at one time. 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 September 30, 2016, were approximately $56.8 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 September 30, 2016. 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 match the recording of expenses in the condensed consolidated financial statements to the actual services received and efforts expended. As actual costs become known, the Company adjusts its accruals 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 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 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 condensed consolidated balance sheet. Recently Issued Accounting Standards: In January 2016, the Financial Accounting Standards Board, or FASB, issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities In February 2016, the FASB issued ASU No. 2016-02, Leases In March 2016, the FASB issued ASU No. 2016-06, Derivatives and Hedging Contingent Put and Call Options in Debt Instruments In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Deferral of the Effective Date In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Deferral of the Effective Date In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows : Classification of Certain Cash Receipts and Cash Payments

Prepaid Expenses and Other

Prepaid Expenses and Other	9 Months Ended
	Sep. 30, 2016
Banking And Thrift [Abstract]
Prepaid Expenses and Other	Note 3—Prepaid Expenses and Other: Prepaid expenses and other consisted of the following (in thousands): September 30, 2016 December 31, 2015 Current: CRO services $ 3,902 $ 2,969 Other clinical development 1,541 2,309 Insurance — 1,138 Other 1,847 1,244 7,290 7,660 Long-term: CRO services 4,975 5,754 Other clinical development 1,606 3,005 Insurance 36 87 Other 518 751 7,135 9,597 Totals $ 14,425 $ 17,257

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2016
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: September 30, 2016 December 31, 2015 Leasehold improvements $ 3,760 $ 1,502 Computer equipment 1,781 1,646 Telephone equipment 169 169 Furniture and fixtures 2,136 1,167 7,846 4,484 Less: accumulated depreciation and amortization (2,666 ) (2,101 ) Totals $ 5,180 $ 2,383 During the nine months ended September 30, 2016, the Company disposed of leasehold improvements that were surrendered as a result of the amended lease in its South San Francisco location (see Note 9 – Commitments and Contingencies of the Consolidated Financial Statements section of the Annual Report on Form 10-K for the year ended December 31, 2015). The loss on the disposal of leasehold improvements was approximately $0.4 million.

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2016
Payables And Accruals [Abstract]
Accrued Expenses	Note 5—Accrued Expenses: Accrued expenses consisted of the following (in thousands): September 30, 2016 December 31, 2015 Accrued CRO services $ 7,098 $ 8,436 Accrued other clinical development 3,820 3,618 Accrued legal fees 517 443 Accrued compensation 5,256 1,970 Other 30 172 Totals $ 16,721 $ 14,639 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	9 Months Ended
	Sep. 30, 2016
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 and nonqualified stock options, 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 under Employee stock-based compensation for the three and nine months ended September 30, 2016 and 2015 were as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Stock-based compensation: Options - Research and development, or R&D $ 20,258 $ 19,867 $ 66,376 $ 60,594 General and administrative, or G&A 6,802 4,747 18,852 12,173 Restricted stock units - R&D 1,754 — 1,754 — G&A 869 — 869 — Performance shares - R&D 68 342 139 487 Total stock-based compensation expense $ 29,751 $ 24,956 $ 87,990 $ 73,254 Impact on basic and diluted net loss per share $ 0.92 $ 0.77 $ 2.71 $ 2.29 Weighted average shares (basic and diluted) 32,497,168 32,303,203 32,489,584 32,018,869 Performance Shares: During January 2014, performance share awards that provide for a maximum of 28,411 shares of common stock to be issued were granted to certain employees. These shares vest over three years on the first, second and third anniversary of December 15, 2013. On each vesting date, if the Company’s closing common stock price is equal to $102.46 per share, one-third of the 28,411 shares will be awarded. If the Company’s closing common stock price on a vesting date is either lesser or greater than $102.46 per share, the number of shares of common stock to be issued will be adjusted to be less than one-third of the 28,411 shares. No shares will be awarded on a vesting date if the Company’s closing common stock price is less than $47.53 per share at such vesting dates. The performance shares are valued on the grant date and the fair value of the performance award is equal to the market price of the Company’s common stock on the grant date. The performance share expense is recognized based on the Company’s estimate of a range of probabilities that the Company’s closing common stock price will be lower or higher than $102.46 on the vesting dates. Based on the range of probabilities, the expense is calculated and recognized over the three-year vesting period. On December 15, 2015, the second vesting occurred and the calculations were performed. As a result, 6,530 shares of common stock were issued to the employees and 2,943 performance shares were cancelled. The third and final vesting event will occur on December 15, 2016. Weighted Average Grant-Date Performance shares Shares Fair Value Nonvested shares at December 31, 2015 9,469 $ 102.46 Granted — — Vested/Issued — — Cancelled — — Nonvested shares at September 30, 2016 9,469 $ 102.46 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 nine months ended September 30, 2016 and 2015: 2016 2015 Dividend yield 0.0 % 0.0 % Expected volatility 67.3 % 63.4 % Risk-free interest rate 1.4 % 1.6 % Expected life in years 5.72 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, 2015 5,542,285 $ 105.59 8.6 $ 87,632 Granted 712,417 $ 45.02 9.0 — Forfeited (416,501 ) $ 123.67 Exercised (36,250 ) $ 9.71 $ 1,268 Expired (71,800 ) $ 169.60 Outstanding at September 30, 2016 5,730,151 $ 96.55 7.9 $ 79,721 Nonvested at September 30, 2016 2,736,716 $ 99.35 9.0 $ 16,048 Exercisable at September 30, 2016 2,993,435 $ 94.00 7.0 $ 63,673 At September 30, 2016, total estimated unrecognized employee compensation cost related to nonvested stock options and performance shares granted prior to that date were approximately $138.8 million and $0.3 million, respectively. These unrecognized expenses are expected to be recognized over a weighted-average period of 1.7 years for stock options and 0.3 years for performance shares. The weighted-average grant date fair value of options granted during the nine months ended September 30, 2016 and 2015, were $26.79 per share and $89.17 per share, respectively. Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2015 3,572,202 $ 73.59 Granted 712,417 26.79 Vested/Issued (1,131,402 ) 85.08 Forfeited (416,501 ) 74.02 Nonvested shares at September 30, 2016 2,736,716 59.27 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. Because the service period began on the vesting start date of July 19, 2016, and the award date did not occur until October 14, 2016, the restricted stock units are valued using the fair value on September 30, 2016, and will be adjusted to the fair value on the award date, October 14, 2016. Weighted Average Grant-Date Restricted stock units Shares Fair Value 1 Nonvested shares at December 31, 2015 — $ — Granted 640,644 54.35 Vested/Issued — — Cancelled — — Nonvested shares at September 30, 2016 640,644 $ 54.35 1 As the service inception date preceded the grant date, the Company’s accrual of compensation cost for the periods before the grant date was based on the fair value of the awards at the reporting date.

401(k) Savings Plan

401(k) Savings Plan	9 Months Ended
	Sep. 30, 2016
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 $0.7 million and $0.5 million for the nine months ended September 30, 2016 and 2015, respectively.

Receivables

Receivables	9 Months Ended
	Sep. 30, 2016
Receivables [Abstract]
Receivables	On April 1, 2016, the Company took possession of additional office space pursuant to the amendments to the leases entered into in July 2015 (see Note 9 – Commitments and Contingencies of the Consolidated Financial Statements section of the Annual Report on Form 10-K for the year ended December 31, 2015). This office space increased the leased square footage in the Los Angeles and South San Francisco offices by approximately 26,000 square feet and 13,000 square feet, respectively. Pursuant to the terms of these amended leases, the landlords provided tenant improvement allowances. One of the tenant improvement allowances was prepaid by the Company and will be reimbursed by the landlord prior to December 31, 2016. The total of this landlord receivable is approximately $1.2 million.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2016
Subsequent Events [Abstract]
Subsequent Events	Note 9—Subsequent Events: On October 19, 2016, the Company entered into an underwriting agreement in connection with the public offering, issuance and sale by the Company of 3,750,000 shares of the Company’s common stock, par value $0.0001 per share, at a public offering price of $40.00 per share, less underwriting discounts and commissions. Under the terms of the underwriting agreement, the Company also granted the underwriters an option exercisable for 30 days to purchase up to an additional 562,500 shares of its common stock at the public offering price, less underwriting discounts and commissions. On October 20, 2016, the underwriters exercised their option to purchase additional shares in full. The Company received net proceeds

Significant Accounting Polici17

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2016
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 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 and long 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. Premiums and discounts are amortized or accreted over the life of the related security as an adjustment to yield using the straight-line method. Interest income is recognized when earned.
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 September 30, 2016 and December 31, 2015, 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): September 30, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 40,457 $ — $ — $ 40,457 Commercial paper — 15,368 — 15,368 Marketable securities - U.S. government — 6,022 — 6,022 Marketable securities - corporate bonds — 35,000 — 35,000 $ 40,457 $ 56,390 $ — $ 96,847 December 31, 2015 Level 1 Level 2 Level 3 Total Cash equivalents $ 29,166 $ — $ — $ 29,166 Commercial paper — 2,996 — 2,996 Marketable securities - U.S. government — 11,500 — 11,500 Marketable securities - corporate bonds — 169,824 — 169,824 $ 29,166 $ 184,320 $ — $ 213,486 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, exclusive of any transaction costs and without any adjustments to reflect discounts that may be applied to selling a large block of securities at one time.
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 September 30, 2016, were approximately $56.8 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 September 30, 2016.
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 match the recording of expenses in the condensed consolidated financial statements to the actual services received and efforts expended. As actual costs become known, the Company adjusts its accruals 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 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 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 condensed consolidated balance sheet.
Recently Issued Accounting Standards	Recently Issued Accounting Standards: In January 2016, the Financial Accounting Standards Board, or FASB, issued ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities In February 2016, the FASB issued ASU No. 2016-02, Leases In March 2016, the FASB issued ASU No. 2016-06, Derivatives and Hedging Contingent Put and Call Options in Debt Instruments In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation In April 2016, the FASB issued ASU No. 2016-10, Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Deferral of the Effective Date In May 2016, the FASB issued ASU No. 2016-12, Revenue from Contracts with Customers Revenue from Contracts with Customers Revenue from Contracts with Customers Deferral of the Effective Date In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows : Classification of Certain Cash Receipts and Cash Payments

Significant Accounting Polici18

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2016
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 September 30, 2016 and December 31, 2015, 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): September 30, 2016 Level 1 Level 2 Level 3 Total Cash equivalents $ 40,457 $ — $ — $ 40,457 Commercial paper — 15,368 — 15,368 Marketable securities - U.S. government — 6,022 — 6,022 Marketable securities - corporate bonds — 35,000 — 35,000 $ 40,457 $ 56,390 $ — $ 96,847 December 31, 2015 Level 1 Level 2 Level 3 Total Cash equivalents $ 29,166 $ — $ — $ 29,166 Commercial paper — 2,996 — 2,996 Marketable securities - U.S. government — 11,500 — 11,500 Marketable securities - corporate bonds — 169,824 — 169,824 $ 29,166 $ 184,320 $ — $ 213,486

Prepaid Expenses and Other (Tab

Prepaid Expenses and Other (Tables)	9 Months Ended
	Sep. 30, 2016
Banking And Thrift [Abstract]
Components of Prepaid Expenses and Other	Prepaid expenses and other consisted of the following (in thousands): September 30, 2016 December 31, 2015 Current: CRO services $ 3,902 $ 2,969 Other clinical development 1,541 2,309 Insurance — 1,138 Other 1,847 1,244 7,290 7,660 Long-term: CRO services 4,975 5,754 Other clinical development 1,606 3,005 Insurance 36 87 Other 518 751 7,135 9,597 Totals $ 14,425 $ 17,257

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2016
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following (in thousands): Property and Equipment: September 30, 2016 December 31, 2015 Leasehold improvements $ 3,760 $ 1,502 Computer equipment 1,781 1,646 Telephone equipment 169 169 Furniture and fixtures 2,136 1,167 7,846 4,484 Less: accumulated depreciation and amortization (2,666 ) (2,101 ) Totals $ 5,180 $ 2,383

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2016
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses consisted of the following (in thousands): September 30, 2016 December 31, 2015 Accrued CRO services $ 7,098 $ 8,436 Accrued other clinical development 3,820 3,618 Accrued legal fees 517 443 Accrued compensation 5,256 1,970 Other 30 172 Totals $ 16,721 $ 14,639

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2016
Equity [Abstract]
Employee Stock-based Compensation	Employee stock-based compensation for the three and nine months ended September 30, 2016 and 2015 were as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2016 2015 2016 2015 Stock-based compensation: Options - Research and development, or R&D $ 20,258 $ 19,867 $ 66,376 $ 60,594 General and administrative, or G&A 6,802 4,747 18,852 12,173 Restricted stock units - R&D 1,754 — 1,754 — G&A 869 — 869 — Performance shares - R&D 68 342 139 487 Total stock-based compensation expense $ 29,751 $ 24,956 $ 87,990 $ 73,254 Impact on basic and diluted net loss per share $ 0.92 $ 0.77 $ 2.71 $ 2.29 Weighted average shares (basic and diluted) 32,497,168 32,303,203 32,489,584 32,018,869
Performance Shares and Stock Options	Weighted Average Grant-Date Performance shares Shares Fair Value Nonvested shares at December 31, 2015 9,469 $ 102.46 Granted — — Vested/Issued — — Cancelled — — Nonvested shares at September 30, 2016 9,469 $ 102.46 The weighted-average grant date fair value of options granted during the nine months ended September 30, 2016 and 2015, were $26.79 per share and $89.17 per share, respectively. Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2015 3,572,202 $ 73.59 Granted 712,417 26.79 Vested/Issued (1,131,402 ) 85.08 Forfeited (416,501 ) 74.02 Nonvested shares at September 30, 2016 2,736,716 59.27
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 nine months ended September 30, 2016 and 2015: 2016 2015 Dividend yield 0.0 % 0.0 % Expected volatility 67.3 % 63.4 % Risk-free interest rate 1.4 % 1.6 % Expected life in years 5.72 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, 2015 5,542,285 $ 105.59 8.6 $ 87,632 Granted 712,417 $ 45.02 9.0 — Forfeited (416,501 ) $ 123.67 Exercised (36,250 ) $ 9.71 $ 1,268 Expired (71,800 ) $ 169.60 Outstanding at September 30, 2016 5,730,151 $ 96.55 7.9 $ 79,721 Nonvested at September 30, 2016 2,736,716 $ 99.35 9.0 $ 16,048 Exercisable at September 30, 2016 2,993,435 $ 94.00 7.0 $ 63,673
Restricted Stock Units	Weighted Average Grant-Date Restricted stock units Shares Fair Value 1 Nonvested shares at December 31, 2015 — $ — Granted 640,644 54.35 Vested/Issued — — Cancelled — — Nonvested shares at September 30, 2016 640,644 $ 54.35 1 As the service inception date preceded the grant date, the Company’s accrual of compensation cost for the periods before the grant date was based on the fair value of the awards at the reporting date.

Business and Basis of Present23

Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	Oct. 20, 2016	Oct. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net loss			$ (65,781)	$ (60,417)	$ (203,350)	$ (177,565)
Net cash used in operating activities					$ (100,729)	(121,437)
Net proceeds from issuance of common stock						$ 205,133
Subsequent Event | Underwritten Public Offering
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceeds from issuance of common stock	$ 161,800	$ 161,800

Assets Measured at Fair Value o

Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 40,457	$ 29,166
Total	96,847	213,486
Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	15,368	2,996
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	35,000	169,824
U.S. government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	6,022	11,500
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	40,457	29,166
Total	40,457	29,166
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	56,390	184,320
Level 2 | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	15,368	2,996
Level 2 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	35,000	169,824
Level 2 | U.S. government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 6,022	$ 11,500

Significant Accounting Polici25

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Significant Accounting Policies [Line Items]
Cash and cash equivalents in excess of insured limits	$ 56.8		$ 56.8
Performance Awards
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share	9,469	18,942	9,469	18,942
Warrants
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share	2,116,250	2,116,250	2,116,250	2,116,250
Restricted Stock Units
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share	640,644		640,644
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	5,730,151	4,444,258	5,730,151	4,444,258
Minimum
Significant Accounting Policies [Line Items]
Property and equipment, useful lives			3 years
Maximum
Significant Accounting Policies [Line Items]
Property and equipment, useful lives			5 years

Components of Prepaid Expenses

Components of Prepaid Expenses and Other (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	$ 7,290	$ 7,660
Prepaid expenses and other, long-term	7,135	9,597
Totals	14,425	17,257
CRO services
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	3,902	2,969
Prepaid expenses and other, long-term	4,975	5,754
Other clinical development
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	1,541	2,309
Prepaid expenses and other, long-term	1,606	3,005
Insurance
Prepaid Expenses [Line Items]
Prepaid expenses and other, current		1,138
Prepaid expenses and other, long-term	36	87
Other
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	1,847	1,244
Prepaid expenses and other, long-term	$ 518	$ 751

Property and Equipment (Detail)

Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 7,846	$ 4,484
Less: accumulated depreciation and amortization	(2,666)	(2,101)
Totals	5,180	2,383
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	3,760	1,502
Computer Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	1,781	1,646
Telephone Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	169	169
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 2,136	$ 1,167

Property and Equipment - Additi

Property and Equipment - Additional Information (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2016USD ($)
Property Plant And Equipment [Line Items]
Loss on disposal of leasehold improvements	$ 368
Leasehold Improvements
Property Plant And Equipment [Line Items]
Loss on disposal of leasehold improvements	$ 400

Accrued Expenses (Detail)

Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Payables And Accruals [Abstract]
Accrued CRO services	$ 7,098	$ 8,436
Accrued other clinical development	3,820	3,618
Accrued legal fees	517	443
Accrued compensation	5,256	1,970
Other	30	172
Totals	$ 16,721	$ 14,639

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Oct. 14, 2016	Dec. 15, 2015	Jan. 31, 2014	Sep. 30, 2016	Sep. 30, 2015
Stockholders Equity Note [Line Items]
Weighted-average grant date fair value of options granted				$ 26.79	$ 89.17
Performance Awards
Stockholders Equity Note [Line Items]
Number of shares granted to employees				0
Shares vesting period				3 years
Shares issued to the employees		6,530
Shares cancelled		2,943		0
Estimated unrecognized employee compensation cost related to non-vested stock options granted				$ 0.3
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition				3 months 18 days
Performance Awards | Employees
Stockholders Equity Note [Line Items]
Shares vesting period			3 years
Common stock price			$ 102.46
Non Vested Stock Options
Stockholders Equity Note [Line Items]
Estimated unrecognized employee compensation cost related to non-vested stock options granted				$ 138.8
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]
Number of shares granted to employees				640,644
Shares cancelled				0
Restricted Stock Units | Subsequent Event
Stockholders Equity Note [Line Items]
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. Because the service period began on the vesting start date of July 19, 2016, and the award date did not occur until October 14, 2016, the restricted stock units are valued using the fair value on September 30, 2016, and will be adjusted to the fair value on the award date, October 14, 2016.
2011 Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance				10,529,412
Maximum | Performance Awards
Stockholders Equity Note [Line Items]
Number of shares granted to employees					28,411
Maximum | Performance Awards | Employees
Stockholders Equity Note [Line Items]
Number of shares granted to employees			28,411
Maximum | 2011 Plan
Stockholders Equity Note [Line Items]
Stock options granted, term				10 years
Minimum | Performance Awards | Employees
Stockholders Equity Note [Line Items]
Common stock price			$ 47.53

Employee Stock-based Compensati

Employee Stock-based Compensation (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 29,751	$ 24,956	$ 87,990	$ 73,254
Impact on basic and diluted net loss per share	$ 0.92	$ 0.77	$ 2.71	$ 2.29
Weighted average shares (basic and diluted)	32,497,168	32,303,203	32,489,584	32,018,869
Employee Stock Option | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 20,258	$ 19,867	$ 66,376	$ 60,594
Employee Stock Option | General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	6,802	4,747	18,852	12,173
Restricted Stock Units | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	1,754		1,754
Restricted Stock Units | General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	869		869
Performance Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 68	$ 342	$ 139	$ 487

Performance Shares (Detail)

Performance Shares (Detail) - Performance Awards - $ / shares	Dec. 15, 2015	Sep. 30, 2016
Performance shares
Beginning balance, shares		9,469
Granted		0
Vested/Issued		0
Cancelled	(2,943)	0
Ending balance, shares		9,469
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value		$ 102.46
Granted		0
Vested/Issued		0
Cancelled		0
Ending balance, Weighted Average Grant-Date Fair Value		$ 102.46

Fair Value Options Weighted-Ave

Fair Value Options Weighted-Average Assumptions (Detail) - Employee Stock Option	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility	67.30%	63.40%
Risk-free interest rate	1.40%	1.60%
Expected life in years	5 years 8 months 19 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	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Shares
Beginning balance, shares	5,542,285
Granted, shares	712,417
Forfeited, shares	(416,501)
Exercised, shares	(36,250)
Expired, shares	(71,800)
Ending balance, shares	5,730,151	5,542,285
Nonvested, shares	2,736,716	3,572,202
Exercisable, shares	2,993,435
Weighted Average Exercise Price
Beginning Balance, Weighted Average Exercise Price	$ 105.59
Granted, Weighted Average Exercise Price	45.02
Forfeited, Weighted Average Exercise Price	123.67
Exercised, Weighted Average Exercise Price	9.71
Expired, Weighted Average Exercise Price	169.60
Ending Balance, Weighted Average Exercise Price	96.55	$ 105.59
Nonvested, Weighted Average Exercise Price	99.35
Exercisable, Weighted Average Exercise Price	$ 94
Weighted Average Remaining Contractual Term (years)
Weighted Average Remaining Contractual Term (years)	7 years 10 months 24 days	8 years 7 months 6 days
Granted, Weighted Average Remaining Contractual Term (years)	9 years
Nonvested, Weighted Average Remaining Contractual Term (years)	9 years
Exercisable, Weighted Average Remaining Contractual Term (years)	7 years
Aggregate Intrinsic Value
Beginning balance, Aggregate Intrinsic Value	$ 87,632
Exercised, Aggregate Intrinsic Value	1,268
Ending balance, Aggregate Intrinsic Value	79,721	$ 87,632
Nonvested, Aggregate Intrinsic Value	16,048
Exercisable, Aggregate Intrinsic Value	$ 63,673

Stock Options (Detail)

Stock Options (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Shares
Beginning balance, shares	3,572,202
Granted, shares	712,417
Vested/Issued	(1,131,402)
Forfeited	(416,501)
Ending balance, shares	2,736,716
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value	$ 73.59
Granted	26.79	$ 89.17
Vested/Issued	85.08
Forfeited	74.02
Ending balance, Weighted Average Grant-Date Fair Value	$ 59.27

Restricted Stock Units (Detail)

Restricted Stock Units (Detail) - Restricted Stock Units	9 Months Ended
	Sep. 30, 2016$ / sharesshares
Shares
Beginning balance, shares | shares	0
Granted | shares	640,644
Vested/Issued | shares	0
Cancelled | shares	0
Ending balance, shares | shares	640,644
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value | $ / shares	$ 0
Granted | $ / shares	54.35
Vested/Issued | $ / shares	0
Cancelled | $ / shares	0
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	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution expenses	$ 0.7	$ 0.5
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%

Receivables - Additional Inform

Receivables - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2016USD ($)	Apr. 01, 2016ft²
Loans And Leases Receivable Disclosure [Line Items]
Tenant improvement allowances | $	$ 1.2
Los Angeles
Loans And Leases Receivable Disclosure [Line Items]
Lease commencement date	Apr. 1, 2016
Additional square feet leased		26,000
South San Francisco
Loans And Leases Receivable Disclosure [Line Items]
Lease commencement date	Apr. 1, 2016
Additional square feet leased		13,000

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Oct. 20, 2016	Oct. 19, 2016	Oct. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Dec. 31, 2015
Subsequent Event [Line Items]
Common stock, par value					$ 0.0001	$ 0.0001
Net proceeds from issuance of common stock				$ 205,133
Subsequent Event
Subsequent Event [Line Items]
Underwriters option exercisable period		30 days
Subsequent Event | Underwritten Public Offering
Subsequent Event [Line Items]
Issuance of common stock (in shares)		3,750,000
Common stock, par value		$ 0.0001
Issuance of common stock, per share		$ 40
Net proceeds from issuance of common stock	$ 161,800		$ 161,800
Subsequent Event | Overallotment Option Exercise by Underwriters | Maximum
Subsequent Event [Line Items]
Issuance of common stock (in shares)	562,500