Puma Biotechnology (PBYI) 10-Q 9 Nov 15 2015 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2015	Nov. 02, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2015
Document Fiscal Year Focus	2,015
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		32,435,748

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 23,598	$ 38,539
Marketable securities	224,177	102,788
Prepaid expenses and other, current	6,888	6,292
Licensor receivable		1,760
Total current assets	254,663	149,379
Property and equipment, net	2,532	2,157
Prepaid expenses and other, long-term	10,117	10,007
Restricted cash	4,312	1,215
Total assets	271,624	162,758
Current liabilities:
Accounts payable	9,783	14,997
Accrued expenses	15,548	29,444
Total current liabilities	25,331	44,441
Deferred rent	1,452	1,269
Total liabilities	26,783	45,710
Stockholders' equity:
Common stock - $.0001 par value; 100,000,000 shares authorized; 32,423,527 shares issued and outstanding at September 30, 2015 and 30,548,309 issued and outstanding at December 31, 2014	3	3
Additional paid-in capital	703,651	399,191
Receivables from the exercises of options		(835)
Accumulated other comprehensive loss	(32)	(95)
Accumulated deficit	(458,781)	(281,216)
Total stockholders' equity	244,841	117,048
Total liabilities and stockholders' equity	$ 271,624	$ 162,758

Condensed Consolidated Balance3

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2015	Dec. 31, 2014
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	32,423,527	30,548,309
Common stock, shares outstanding	32,423,527	30,548,309

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating expenses:
General and administrative	$ 8,809	$ 3,867	$ 22,212	$ 11,296
Research and development	51,924	32,092	156,033	83,387
Totals	60,733	35,959	178,245	94,683
Loss from operations	(60,733)	(35,959)	(178,245)	(94,683)
Other income (expenses):
Interest income	318	111	654	223
Other income (expense)	(2)	4	26	(22)
Totals	316	115	680	201
Net loss	(60,417)	(35,844)	(177,565)	(94,482)
Net loss applicable to common stock	$ (60,417)	$ (35,844)	$ (177,565)	$ (94,482)
Net loss per common share—basic and diluted	$ (1.87)	$ (1.19)	$ (5.55)	$ (3.16)
Weighted-average common shares outstanding—basic and diluted	32,303,203	30,117,819	32,018,869	29,936,254

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (60,417)	$ (35,844)	$ (177,565)	$ (94,482)
Other comprehensive loss
Unrealized gain (loss) on available-for-sale securities	149	(41)	63	(121)
Comprehensive loss	$ (60,268)	$ (35,885)	$ (177,502)	$ (94,603)

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Stockholders' Equity - 9 months ended Sep. 30, 2015 - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-in Capital	Receivables from the Exercise of Options	Accumulated Other Comprehensive Loss	Accumulated Deficit
Beginning Balance at Dec. 31, 2014	$ 117,048	$ 3	$ 399,191	$ (835)	$ (95)	$ (281,216)
Beginning Balance (in shares) at Dec. 31, 2014	30,548,309	30,548,309
Stock-based compensation	$ 73,254		73,254
Exercises of stock options	$ 26,908		26,073	$ 835
Exercises of stock options (in shares)	720,253	720,253
Issuance of performance shares (in shares)		4,965
Issuance of common stock	$ 205,133		205,133
Issuance of common stock (in shares)		1,150,000
Unrealized gain on available for sale securities	63				63
Net loss	(177,565)					(177,565)
Ending Balance at Sep. 30, 2015	$ 244,841	$ 3	$ 703,651		$ (32)	$ (458,781)
Ending Balance (in shares) at Sep. 30, 2015	32,423,527	32,423,527

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical)	Sep. 30, 2015$ / shares
Statement Of Stockholders Equity [Abstract]
Issuance of common stock, per share	$ 190

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Operating activities:
Net loss	$ (177,565)	$ (94,482)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	568	438
Build-out allowance received from landlord	179
Stock-based compensation	73,254	22,779
Changes in operating assets and liabilities:
Licensor receivable	1,760	8,053
Prepaid expenses and other	(706)	(5,593)
Accounts payable	(5,214)	7,756
Accrued expenses	(13,896)	2,332
Accrual of deferred rent	183	(25)
Net cash used in operating activities	(121,437)	(58,742)
Investing activities:
Purchase of property and equipment	(943)	(554)
Restricted cash	(3,097)	(1)
Expenditures for leasehold improvements	(179)	(110)
Purchase of available-for-sale securities	(211,783)	(132,260)
Sale/maturity of available-for-sale securities	90,457	47,446
Net cash used in investing activities	(125,545)	(85,479)
Financing activities:
Net proceeds from issuance of common stock	205,133	129,440
Net proceeds from exercise of options	26,908
Net cash provided by financing activities	232,041	129,440
Net decrease in cash and cash equivalents	(14,941)	(14,781)
Cash and cash equivalents, beginning of period	38,539	43,044
Cash and cash equivalents, end of period	$ 23,598	$ 28,263

Business and Basis of Presentat

Business and Basis of Presentation	9 Months Ended
	Sep. 30, 2015
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 acquisition, development and commercialization of innovative products to enhance cancer care. The Company aims to acquire proprietary rights to these products, by license or otherwise, fund their research and development and bring the products to market. 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 $60.4 million and $177.6 million and negative cash flows from operations of approximately $36.8 million and $121.4 million for the three and nine months ended September 30, 2015, respectively. 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 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, 2015, 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, 2014. The condensed consolidated balance sheet at December 31, 2014, 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, 2014. 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, 2015, the Company’s financing was primarily through public offerings of Company common stock and private equity placements. The Company sold additional shares of its common stock through an underwritten public offering in January 2015 (see Note 6). As a result, the Company received net proceeds of approximately $205.1 million. Given the current and desired pace of clinical development of its product candidates, management believes that the cash and cash equivalents and marketable securities on hand at September 30, 2015, are sufficient to fund clinical development through 2016 and into 2017. 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, 2015
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 financial statements in conformity with accounting principles generally accepted in the United States, or 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. Licensor Receivable: The Company licenses its lead product candidate, neratinib, from Pfizer, Inc., or Licensor. At the time the license agreement was entered, Licensor agreed to pay certain external “out of pocket” clinical trial costs in excess of an agreed upon “cap” for clinical trials that were ongoing at the time the license agreement with the Licensor was reached. In July 2014, the license agreement was amended to make the Company solely responsible for the expenses incurred or accrued in conducting the ongoing legacy clinical trials after December 31, 2013, and to fix the future royalty rate that must be paid to the Licensor upon commercialization in the low to mid-teens. The balance of licensor receivable at December 31, 2014, of approximately $1.8 million, represented the unpaid portion of these trial costs that remained Licensor’s responsibility after the amendment of the license agreement. The amounts were fully collected during June 2015. 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, 2015 and December 31, 2014, 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, 2015 Level 1 Level 2 Level 3 Total Cash equivalents $ 20,135 $ — $ — $ 20,135 Commercial paper — 2,992 — 2,992 Marketable securities - U.S. government — 11,525 — 11,525 Marketable securities - corporate bonds — 209,660 — 209,660 $ 20,135 $ 224,177 $ — $ 244,312 December 31, 2014 Level 1 Level 2 Level 3 Total Cash equivalents $ 20,874 $ — $ — $ 20,874 Marketable securities - U.S. government — 11,496 — 11,496 Marketable securities - corporate bonds — 91,292 — 91,292 $ 20,874 $ 102,788 $ — $ 123,662 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, 2015, were approximately $27.8 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, 2015. 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 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 common stock shares from the reserve for the Company’s 2011 Incentive Award 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 August the Financial Accounting Standards Board, or the FASB, In May 2014, the FASB issued guidance for revenue recognition for contracts, superseding the previous revenue recognition requirements, along with most existing industry-specific guidance. The guidance requires an entity to review contracts in five steps: (1) identify the contract, (2) identify performance obligations, (3) determine the transaction price, (4) allocate the transaction price, and (5) recognize revenue. The new standard will result in enhanced disclosures regarding the nature, amount, timing and uncertainty of revenue arising from contracts with customers. The standard is effective for our reporting year beginning January 1, 2017 and early adoption is not permitted. On July 9, 2015, the FASB voted to defer the effective date of the above mentioned revenue recognition guidance by one year to December 15, 2017 for interim and annual reporting periods beginning after the date and permitted early adoption of the standard, but not before the original effective date of December 15, 2016. The Company is currently evaluating the impact, if any, that this standard will have on its consolidated financial statements. In June 2014, the FASB issued ASU No. 2014-10, Development Stage Entities The Company adopted this standard on December 31, 2014, and it did not have a material impact on its consolidated financial statements.

Prepaid Expenses and Other

Prepaid Expenses and Other	9 Months Ended
	Sep. 30, 2015
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, 2015 December 31, 2014 Current: CRO services $ 2,946 $ 2,451 Other clinical development 2,798 2,525 Insurance 247 1,007 Other 897 309 6,888 6,292 Long-term: CRO services 5,786 6,352 Other clinical development 3,418 3,464 Insurance 94 130 Other 819 61 10,117 10,007 Totals $ 17,005 $ 16,299

Property and Equipment

Property and Equipment	9 Months Ended
	Sep. 30, 2015
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, 2015 December 31, 2014 Leasehold improvements $ 1,502 $ 1,217 Computer equipment 1,590 1,272 Telephone equipment 169 145 Furniture and fixtures 1,164 848 4,425 3,482 Less: accumulated depreciation and amortization (1,893 ) (1,325 ) Totals $ 2,532 $ 2,157

Accrued Expenses

Accrued Expenses	9 Months Ended
	Sep. 30, 2015
Payables And Accruals [Abstract]
Accrued Expenses	Note 5—Accrued Expenses: Accrued expenses consisted of the following (in thousands): September 30, 2015 December 31, 2014 Accrued CRO services $ 8,813 $ 7,764 Accrued other clinical development 2,610 2,541 Accrued legal fees 334 195 Accrued compensation 3,735 2,449 Payroll taxes withheld for options exercised — 16,414 Other 56 81 Totals $ 15,548 $ 29,444 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 on the employee’s anniversary of hire, 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, 2015
Equity [Abstract]
Stockholders' Equity	Note 6—Stockholders’ Equity: Common Stock: January 2015 Common Stock Offering. On January 21, 2015, the Company entered into an underwriting agreement with Merrill Lynch, Pierce, Fenner & Smith Incorporated and J.P. Morgan Securities LLC, as representatives of several underwriters, providing for the offer and sale in a firm-commitment underwritten public offering of 1,000,000 shares of the Company’s common stock, par value $0.0001 per share, at a price of $190.00 per share, less the underwriting discount. The underwriters exercised the option granted to the underwriters to purchase an additional 150,000 shares of Company common stock from the Company at $190.00 per share, less the underwriting discount. The transaction was completed on January 27, 2015; the Company received net proceeds of approximately $205.1 million, which is comprised of gross proceeds of approximately $218.5 million, offset by the underwriting discount and offering expenses of $13.4 million payable by the Company. Stock-Based Compensation: The Company’s 2011 Incentive Award Plan, or the 2011 Plan, was adopted by the Board of Directors and stockholders of the Company on September 15, 2011. An amendment to the 2011 Plan was adopted by the Board of Directors on June 4, 2014 and the stockholders of the Company on June 10, 2014 which increased the number of shares reserved from 3,529,412 to 6,529,412. A second amendment to the 2011 Plan was adopted by the Board of Directors on April 20, 2015 and the stockholders of the Company on June 9, 2015, which increased the shares reserved from 6,529,412 to 10,529,412. Pursuant to the amended 2011 Plan (referred to hereafter as the 2011 Plan), the Company may grant incentive stock options and nonqualified stock options, as well as other forms of equity-based compensation such as performance shares. Incentive stock options may be granted only to employees, while consultants, employees, officers and directors are eligible for the grant of nonqualified options 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. The performance shares are valued at market value less par value and vest over three years, with the number of shares to be issued determined by the market price on the vesting date. The maximum number of shares issuable pursuant to a performance share award is established on the grant date. Employee stock-based compensation for the three and nine months ended September 30, 2015 and 2014, were as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Stock-based compensation: Options - Research and development, or R&D $ 19,867 $ 8,726 $ 60,594 $ 17,690 General and administrative, or G&A 4,747 1,377 12,173 4,081 Performance shares - R&D 342 346 487 1,008 Total stock-based compensation expense $ 24,956 $ 10,449 $ 73,254 $ 22,779 Impact on basic and diluted net loss per share $ 0.77 $ 0.35 $ 2.29 $ 0.76 Weighted average shares (basic and diluted) 32,303,203 30,117,819 32,018,869 29,936,254 Performance Shares: During January 2014, performance share awards were granted to certain employees that provide for a maximum of 28,411 common stock shares to be issued. 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 is either lesser or greater than $102.46 per share, the number of common stock shares to be issued will be adjusted to be less than one-third of the 28,411 shares. No shares will be awarded if the Company’s closing common stock price is less than $47.53 per share at the 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, 2014, the first vesting occurred and the calculations were performed. As a result, 4,965 shares of common stock were issued to the employees and 4,504 performance shares were cancelled. Weighted Average Grant-Date Performance shares Shares Fair Value Nonvested shares at December 31, 2014 18,942 $ 102.46 Granted — — Vested/Issued — — Cancelled — — Nonvested shares at September 30, 2015 18,942 $ 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, 2015 and 2014: 2015 2014 Dividend yield 0.0 % 0.0 % Expected volatility 63.4 % 81.8 % Risk-free interest rate 1.6 % 1.8 % 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, 2014 3,978,126 $ 89.55 8.7 $ 431,635 Granted 1,402,786 $ 153.65 9.5 — Forfeited (214,110 ) $ 188.10 — — Exercised (720,253 ) $ 36.20 — $ 93,368 Expired (2,291 ) $ 117.84 Outstanding at September 30, 2015 4,444,258 $ 70.12 8.5 $ 80,264 Nonvested at September 30, 2015 2,802,984 $ 150.43 9.2 $ 10,135 Exercisable at September 30, 2015 1,641,274 $ 50.87 7.3 $ 70,129 At September 30, 2015, total estimated unrecognized employee compensation cost related to nonvested stock options and performance shares granted prior to that date were approximately $208.2 million and $0.7 million, respectively. These unrecognized expenses are expected to be recognized over a weighted-average period of 2.2 years for stock options and 0.9 years for performance shares. The weighted-average grant date fair value of options granted during the nine months ended September 30, 2015 and 2014, were $89.17 per share and $86.83 per share, respectively. Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2014 2,591,565 $ 81.33 Granted 1,402,786 89.17 Vested/Issued (977,257 ) 61.22 Forfeited (214,110 ) 110.20 Nonvested shares at September 30, 2015 2,802,984 90.95

401(k) Savings Plan

401(k) Savings Plan	9 Months Ended
	Sep. 30, 2015
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 $0.5 million and $0.4 million for the nine months ended September 30, 2015 and 2014, respectively.

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2015
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 8—Commitments and Contingencies: In July 2015, the Company amended its lease with CA-10880 Wilshire Limited Partnership to expand the rented square feet in its Los Angeles office by approximately 26,000 square feet. The lease is expected to commence on or about April 1, 2016, and increases the monthly rent in the Los Angeles location by approximately $150,000 per month with annual increases of approximately 3% per year for the 10-year lease term. In addition, in July 2015, the Company amended its office lease with PR 701 Gateway, LLC (as successor in interest to DWF III Gateway, LLC) to expand the rented square feet in its South San Francisco location by approximately 13,000 square feet. The lease is expected to commence on or about April 1, 2016, and increases the monthly rent in the South San Francisco location by approximately $51,400 with annual increases of approximately 3% per year for the 10-year lease term.

Significant Accounting Polici17

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2015
Accounting Policies [Abstract]
Use of Estimates	Use of Estimates: The preparation of financial statements in conformity with accounting principles generally accepted in the United States, or 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.
Licensor Receivable	Licensor Receivable: The Company licenses its lead product candidate, neratinib, from Pfizer, Inc., or Licensor. At the time the license agreement was entered, Licensor agreed to pay certain external “out of pocket” clinical trial costs in excess of an agreed upon “cap” for clinical trials that were ongoing at the time the license agreement with the Licensor was reached. In July 2014, the license agreement was amended to make the Company solely responsible for the expenses incurred or accrued in conducting the ongoing legacy clinical trials after December 31, 2013, and to fix the future royalty rate that must be paid to the Licensor upon commercialization in the low to mid-teens. The balance of licensor receivable at December 31, 2014, of approximately $1.8 million, represented the unpaid portion of these trial costs that remained Licensor’s responsibility after the amendment of the license agreement. The amounts were fully collected during June 2015.
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, 2015 and December 31, 2014, 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, 2015 Level 1 Level 2 Level 3 Total Cash equivalents $ 20,135 $ — $ — $ 20,135 Commercial paper — 2,992 — 2,992 Marketable securities - U.S. government — 11,525 — 11,525 Marketable securities - corporate bonds — 209,660 — 209,660 $ 20,135 $ 224,177 $ — $ 244,312 December 31, 2014 Level 1 Level 2 Level 3 Total Cash equivalents $ 20,874 $ — $ — $ 20,874 Marketable securities - U.S. government — 11,496 — 11,496 Marketable securities - corporate bonds — 91,292 — 91,292 $ 20,874 $ 102,788 $ — $ 123,662 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, 2015, were approximately $27.8 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, 2015.
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
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 common stock shares from the reserve for the Company’s 2011 Incentive Award 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 August the Financial Accounting Standards Board, or the FASB, In May 2014, the FASB issued guidance for revenue recognition for contracts, superseding the previous revenue recognition requirements, along with most existing industry-specific guidance. The guidance requires an entity to review contracts in five steps: (1) identify the contract, (2) identify performance obligations, (3) determine the transaction price, (4) allocate the transaction price, and (5) recognize revenue. The new standard will result in enhanced disclosures regarding the nature, amount, timing and uncertainty of revenue arising from contracts with customers. The standard is effective for our reporting year beginning January 1, 2017 and early adoption is not permitted. On July 9, 2015, the FASB voted to defer the effective date of the above mentioned revenue recognition guidance by one year to December 15, 2017 for interim and annual reporting periods beginning after the date and permitted early adoption of the standard, but not before the original effective date of December 15, 2016. The Company is currently evaluating the impact, if any, that this standard will have on its consolidated financial statements. In June 2014, the FASB issued ASU No. 2014-10, Development Stage Entities The Company adopted this standard on December 31, 2014, and it did not have a material impact on its consolidated financial statements.

Significant Accounting Polici18

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2015
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, 2015 and December 31, 2014, 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, 2015 Level 1 Level 2 Level 3 Total Cash equivalents $ 20,135 $ — $ — $ 20,135 Commercial paper — 2,992 — 2,992 Marketable securities - U.S. government — 11,525 — 11,525 Marketable securities - corporate bonds — 209,660 — 209,660 $ 20,135 $ 224,177 $ — $ 244,312 December 31, 2014 Level 1 Level 2 Level 3 Total Cash equivalents $ 20,874 $ — $ — $ 20,874 Marketable securities - U.S. government — 11,496 — 11,496 Marketable securities - corporate bonds — 91,292 — 91,292 $ 20,874 $ 102,788 $ — $ 123,662

Prepaid Expenses and Other (Tab

Prepaid Expenses and Other (Tables)	9 Months Ended
	Sep. 30, 2015
Banking And Thrift [Abstract]
Components of Prepaid Expenses and Other	Prepaid expenses and other consisted of the following (in thousands): September 30, 2015 December 31, 2014 Current: CRO services $ 2,946 $ 2,451 Other clinical development 2,798 2,525 Insurance 247 1,007 Other 897 309 6,888 6,292 Long-term: CRO services 5,786 6,352 Other clinical development 3,418 3,464 Insurance 94 130 Other 819 61 10,117 10,007 Totals $ 17,005 $ 16,299

Property and Equipment (Tables)

Property and Equipment (Tables)	9 Months Ended
	Sep. 30, 2015
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following (in thousands): Property and Equipment: September 30, 2015 December 31, 2014 Leasehold improvements $ 1,502 $ 1,217 Computer equipment 1,590 1,272 Telephone equipment 169 145 Furniture and fixtures 1,164 848 4,425 3,482 Less: accumulated depreciation and amortization (1,893 ) (1,325 ) Totals $ 2,532 $ 2,157

Accrued Expenses (Tables)

Accrued Expenses (Tables)	9 Months Ended
	Sep. 30, 2015
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses consisted of the following (in thousands): September 30, 2015 December 31, 2014 Accrued CRO services $ 8,813 $ 7,764 Accrued other clinical development 2,610 2,541 Accrued legal fees 334 195 Accrued compensation 3,735 2,449 Payroll taxes withheld for options exercised — 16,414 Other 56 81 Totals $ 15,548 $ 29,444

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2015
Equity [Abstract]
Recognized Expense of Share Based Compensation	Employee stock-based compensation for the three and nine months ended September 30, 2015 and 2014, were as follows (in thousands, except share and per share data): Three Months Ended September 30, Nine Months Ended September 30, 2015 2014 2015 2014 Stock-based compensation: Options - Research and development, or R&D $ 19,867 $ 8,726 $ 60,594 $ 17,690 General and administrative, or G&A 4,747 1,377 12,173 4,081 Performance shares - R&D 342 346 487 1,008 Total stock-based compensation expense $ 24,956 $ 10,449 $ 73,254 $ 22,779 Impact on basic and diluted net loss per share $ 0.77 $ 0.35 $ 2.29 $ 0.76 Weighted average shares (basic and diluted) 32,303,203 30,117,819 32,018,869 29,936,254
Stock Options	Weighted Average Grant-Date Performance shares Shares Fair Value Nonvested shares at December 31, 2014 18,942 $ 102.46 Granted — — Vested/Issued — — Cancelled — — Nonvested shares at September 30, 2015 18,942 $ 102.46 Weighted Average Grant-Date Stock options Shares Fair Value Nonvested shares at December 31, 2014 2,591,565 $ 81.33 Granted 1,402,786 89.17 Vested/Issued (977,257 ) 61.22 Forfeited (214,110 ) 110.20 Nonvested shares at September 30, 2015 2,802,984 90.95
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, 2015 and 2014: 2015 2014 Dividend yield 0.0 % 0.0 % Expected volatility 63.4 % 81.8 % Risk-free interest rate 1.6 % 1.8 % 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, 2014 3,978,126 $ 89.55 8.7 $ 431,635 Granted 1,402,786 $ 153.65 9.5 — Forfeited (214,110 ) $ 188.10 — — Exercised (720,253 ) $ 36.20 — $ 93,368 Expired (2,291 ) $ 117.84 Outstanding at September 30, 2015 4,444,258 $ 70.12 8.5 $ 80,264 Nonvested at September 30, 2015 2,802,984 $ 150.43 9.2 $ 10,135 Exercisable at September 30, 2015 1,641,274 $ 50.87 7.3 $ 70,129

Business and Basis of Present23

Business and Basis of Presentation - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 27, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net loss		$ (60,417)	$ (35,844)	$ (177,565)	$ (94,482)
Net cash used in operating activities		$ (36,800)		(121,437)	(58,742)
Net proceeds from issuance of common stock				$ 205,133	$ 129,440
Underwritten Public Offering
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceeds from issuance of common stock	$ 205,100

Significant Accounting Polici24

Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Significant Accounting Policies [Line Items]
Licensor receivable collected	$ 1.8
Cash and cash equivalents in excess of insured limits		$ 27.8		$ 27.8
Performance share expense recognition period				3 years
Employee Stock Option
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share		4,444,258	3,778,307	4,444,258	3,778,307
Performance Awards
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share		18,942	28,411	18,942	28,411
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
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

Assets Measured at Fair Value o

Assets Measured at Fair Value on Recurring Basis (Detail) - Fair Value, Measurements, Recurring - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$ 20,135	$ 20,874
Total	244,312	123,662
Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	2,992
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	209,660	91,292
U.S. government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	11,525	11,496
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	20,135	20,874
Total	20,135	20,874
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	224,177	102,788
Level 2 | Commercial paper
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	2,992
Level 2 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	209,660	91,292
Level 2 | U.S. government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$ 11,525	$ 11,496

Components of Prepaid Expenses

Components of Prepaid Expenses and Other (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	$ 6,888	$ 6,292
Prepaid expenses and other, long-term	10,117	10,007
Totals	17,005	16,299
CRO services
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	2,946	2,451
Prepaid expenses and other, long-term	5,786	6,352
Other clinical development
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	2,798	2,525
Prepaid expenses and other, long-term	3,418	3,464
Insurance
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	247	1,007
Prepaid expenses and other, long-term	94	130
Other
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	897	309
Prepaid expenses and other, long-term	$ 819	$ 61

Property and Equipment (Detail)

Property and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 4,425	$ 3,482
Less: accumulated depreciation and amortization	(1,893)	(1,325)
Totals	2,532	2,157
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	1,502	1,217
Computer Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	1,590	1,272
Telephone Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	169	145
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$ 1,164	$ 848

Accrued Expenses (Detail)

Accrued Expenses (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Payables And Accruals [Abstract]
Accrued CRO services	$ 8,813	$ 7,764
Accrued other clinical development	2,610	2,541
Accrued legal fees	334	195
Accrued compensation	3,735	2,449
Payroll taxes withheld for options exercised		16,414
Other	56	81
Totals	$ 15,548	$ 29,444

Stockholders Equity - Additiona

Stockholders Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Jan. 27, 2015	Jan. 21, 2015	Dec. 15, 2014	Jan. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 09, 2015	Dec. 31, 2014	Jun. 10, 2014
Stockholders Equity Note [Line Items]
Common stock, par value					$ 0.0001			$ 0.0001
Issuance of common stock, per share					$ 190
Net proceeds from issuance of common stock					$ 205,133	$ 129,440
Performance share expense recognition period					3 years
Weighted-average grant date fair value of options granted					$ 89.17	$ 86.83
Performance Awards
Stockholders Equity Note [Line Items]
Shares issued to the employees			4,965
Shares cancelled			4,504
Estimated unrecognized employee compensation cost related to non-vested stock options granted					$ 700
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition					10 months 24 days
Performance Awards | Employees
Stockholders Equity Note [Line Items]
Performance share expense recognition 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					$ 208,200
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition					2 years 2 months 12 days
2011 Incentive Award Plan
Stockholders Equity Note [Line Items]
Common stock shares authorized reserved for issuance									3,529,412
Amended 2011 Incentive Award Plan
Stockholders Equity Note [Line Items]
Common stock shares authorized reserved for issuance									6,529,412
Second Amendment 2011 Incentive Award Plan
Stockholders Equity Note [Line Items]
Common stock shares authorized 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 Incentive Award 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
Underwritten Public Offering
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)		1,000,000
Common stock, par value		$ 0.0001
Issuance of common stock, per share		$ 190
Net proceeds from issuance of common stock	$ 205,100
Gross proceeds from issuance of common stock	218,500
Public offering, underwriting discount and estimated offering expenses	$ 13,400
Overallotment Option Exercise by Underwriters
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)		150,000

Stock-Based Compensation Expens

Stock-Based Compensation Expense (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 24,956	$ 10,449	$ 73,254	$ 22,779
Impact on basic and diluted net loss per share	$ 0.77	$ 0.35	$ 2.29	$ 0.76
Weighted average shares (basic and diluted)	32,303,203	30,117,819	32,018,869	29,936,254
Employee Stock Option | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 19,867	$ 8,726	$ 60,594	$ 17,690
Employee Stock Option | General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	4,747	1,377	12,173	4,081
Performance Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$ 342	$ 346	$ 487	$ 1,008

Performance Shares (Detail)

Performance Shares (Detail)	9 Months Ended
	Sep. 30, 2015$ / sharesshares
Performance shares
Beginning balance, shares | shares	18,942
Ending balance, shares | shares	18,942
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value	$ 102.46
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, 2015	Sep. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility	63.40%	81.80%
Risk-free interest rate	1.60%	1.80%
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	9 Months Ended	12 Months Ended
	Sep. 30, 2015	Dec. 31, 2014
Shares
Beginning balance, shares	3,978,126
Granted, shares	1,402,786
Forfeited, shares	(214,110)
Exercised, shares	(720,253)
Expired, shares	(2,291)
Ending balance, shares	4,444,258	3,978,126
Nonvested, shares	2,802,984	2,591,565
Exercisable, shares	1,641,274
Weighted Average Exercise Price
Beginning Balance, Weighted Average Exercise Price	$ 89.55
Granted, Weighted Average Exercise Price	153.65
Forfeited, Weighted Average Exercise Price	188.10
Exercised, Weighted Average Exercise Price	36.20
Expired, Weighted Average Exercise Price	117.84
Ending Balance, Weighted Average Exercise Price	70.12	$ 89.55
Nonvested, Weighted Average Exercise Price	150.43
Exercisable, Weighted Average Exercise Price	$ 50.87
Weighted Average Remaining Contractual Term (years)
Weighted Average Remaining Contractual Term (years)	8 years 6 months	8 years 8 months 12 days
Granted, Weighted Average Remaining Contractual Term (years)	9 years 6 months
Nonvested, Weighted Average Remaining Contractual Term (years)	9 years 2 months 12 days
Exercisable, Weighted Average Remaining Contractual Term (years)	7 years 3 months 18 days
Aggregate Intrinsic Value
Beginning balance, Aggregate Intrinsic Value	$ 431,635
Exercised	93,368
Ending balance, Aggregate Intrinsic Value	80,264	$ 431,635
Nonvested, Aggregate Intrinsic Value	10,135
Exercisable, Aggregate Intrinsic Value	$ 70,129

Stock Options (Detail)

Stock Options (Detail) - $ / shares	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Shares
Beginning balance, shares	2,591,565
Granted, shares	1,402,786
Vested/Issued	(977,257)
Forfeited	(214,110)
Ending balance, shares	2,802,984
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value	$ 81.33
Weighted-average grant date fair value of options granted	89.17	$ 86.83
Vested/Issued	61.22
Forfeited	110.20
Ending balance, Weighted Average Grant-Date Fair Value	$ 90.95

401(K) Savings Plan - Additiona

401(K) Savings Plan - Additional Information (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Defined Benefit Plan Disclosure [Line Items]
Employer matching contribution expenses	$ 0.5	$ 0.4
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%

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Apr. 01, 2016USD ($)	Sep. 30, 2015	Jul. 31, 2015ft²
Los Angeles
Commitments And Contingencies Disclosure [Line Items]
Additional square feet leased | ft²			26,000
Lease commencement date		Apr. 1, 2016
South San Francisco
Commitments And Contingencies Disclosure [Line Items]
Additional square feet leased | ft²			13,000
Lease commencement date		Apr. 1, 2016
Scenario, Forecast | Los Angeles
Commitments And Contingencies Disclosure [Line Items]
Additional lease rent per month	$ 150,000
Percentage of increase in annual rent	3.00%
Office lease, lease term	10 years
Scenario, Forecast | South San Francisco
Commitments And Contingencies Disclosure [Line Items]
Additional lease rent per month	$ 51,400
Percentage of increase in annual rent	3.00%
Office lease, lease term	10 years