Puma Biotechnology (PBYI) 10-Q 11 May 15 2015 Q1 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	3 Months Ended
	Mar. 31, 2015	Apr. 30, 2015
Document And Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	FALSE
Document Period End Date	31-Mar-15
Document Fiscal Year Focus	2015
Document Fiscal Period Focus	Q1
Trading Symbol	PBYI
Entity Registrant Name	PUMA BIOTECHNOLOGY, INC.
Entity Central Index Key	1401667
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		32,150,946

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$155,466	$38,539
Marketable securities	154,863	102,788
Prepaid expenses and other, current	6,357	6,292
Licensor receivable		1,760
Total current assets	316,686	149,379
Property and equipment, net	2,412	2,157
Prepaid expenses and other, long-term	9,811	10,007
Licensor receivable	1,760
Restricted cash	1,215	1,215
Total assets	331,884	162,758
Current liabilities:
Accounts payable	12,608	14,997
Accrued expenses	13,469	29,444
Total current liabilities	26,077	44,441
Deferred rent	1,471	1,269
Total liabilities	27,548	45,710
Stockholders' equity:
Common stock - $.0001 par value; 100,000,000 shares authorized; 32,089,629 shares issued and outstanding at March 31, 2015 and 30,548,309 issued and outstanding at December 31, 2014	3	3
Additional paid-in capital	638,092	399,191
Receivables from the exercise of options		-835
Accumulated other comprehensive loss	-89	-95
Accumulated deficit	-333,670	-281,216
Total stockholders' equity	304,336	117,048
Total liabilities and stockholders' equity	$331,884	$162,758

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Statement Of Financial Position [Abstract]
Common stock, par value	$0.00	$0.00
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	32,089,629	30,548,309
Common stock, shares outstanding	32,089,629	30,548,309

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating expenses:
General and administrative	$7,871	$3,525
Research and development	44,728	16,294
Totals	52,599	19,819
Loss from operations	-52,599	-19,819
Other income (expenses):
Interest income	123	46
Other income (expense)	22	-21
Totals	145	25
Net loss	-52,454	-19,794
Net loss applicable to common stock	($52,454)	($19,794)
Net loss per common sharebbasic and diluted	($1.66)	($0.67)
Weighted-average common shares outstandingbbasic and diluted	31,588,315	29,567,071

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Comprehensive Loss (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Statement Of Income And Comprehensive Income [Abstract]
Net loss	($52,454)	($19,794)
Other comprehensive income (loss)
Unrealized gain (loss) on available-for-sale securities	6	-9
Comprehensive loss	($52,448)	($19,803)

Condensed_Consolidated_Stateme2

Condensed Consolidated Statements of Stockholders' Equity (USD $)	Total	Common Stock	Additional Paid-in Capital	Receivables from the Exercise of Options	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
In Thousands, except Share data
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 option compensation	20,103		20,103
Exercises of stock options	14,437		13,602	835
Exercises of stock options (in shares)	386,355	386,355
Issuance of performance shares (in shares)		4,965
Issuance of common stock	205,196		205,196
Issuance of common stock (in shares)		1,150,000
Unrealized gain (loss) on available-for-sale securities	6				6
Net loss	-52,454					-52,454
Ending Balance at Mar. 31, 2015	$304,336	$3	$638,092		($89)	($333,670)
Ending Balance (in shares) at Mar. 31, 2015	32,089,629	32,089,629

Condensed_Consolidated_Stateme3

Condensed Consolidated Statements of Stockholders' Equity (Parenthetical) (USD $)	3 Months Ended
	Mar. 31, 2015
Statement Of Stockholders Equity [Abstract]
Issuance of common stock, per share	$190

Condensed_Consolidated_Stateme4

Condensed Consolidated Statements of Cash Flows (USD $)	3 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Operating activities:
Net loss	($52,454)	($19,794)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	180	133
Build-out allowance received from landlord	179
Stock option expense	20,103	5,163
Changes in operating assets and liabilities:
Licensor receivable		-3,483
Prepaid expenses and other	131	-145
Accounts payable	-2,389	4,500
Accrued expenses	-15,975	-3,528
Accrual of deferred rent	202	107
Net cash used in operating activities	-50,023	-17,047
Investing activities:
Purchase of property and equipment	-435	-214
Expenditures for leasehold improvements	-179	-4
Purchase of available-for-sale securities	-104,838
Sale/maturity of available-for-sale securities	52,769	8,161
Net cash (used in) provided by investing activities	-52,683	7,943
Financing activities:
Net proceeds from issuance of common stock	205,196	129,440
Net proceeds from exercise of options	14,437
Net cash provided by financing activities	219,633	129,440
Net increase in cash and cash equivalents	116,927	120,336
Cash and cash equivalents, beginning of period	38,539	43,044
Cash and cash equivalents, end of period	$155,466	$163,380

Business_and_Basis_of_Presenta

Business and Basis of Presentation	3 Months Ended
	Mar. 31, 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. References in these Notes to Condensed Consolidated Financial Statements to the “Company” refer to Puma Biotechnology, Inc., a private Delaware company formed on September 15, 2010, or Private Puma, for periods prior to the merger of Private Puma with Public Puma (as defined below), which took place on October 4, 2011, or the Merger, and Puma Biotechnology, Inc., a Delaware company formed on April 27, 2007, and formerly known as Innovative Acquisitions Corp., or Public Puma, for periods following the Merger. The Company is a biopharmaceutical company with a focus on the acquisition, development and commercialization of innovative products to enhance cancer care. The Company focuses on in-licensing drug candidates that are undergoing or have already completed initial clinical testing for the treatment of cancer and then seeks to further develop those drug candidates for commercial use.
	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 $52.5 million and negative cash flows from operations of approximately $50.0 million for the three months ended March 31, 2015. 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 March 31, 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 $205.2 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 March 31, 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_Policie

Significant Accounting Policies	3 Months Ended
	Mar. 31, 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 Pfizer, Inc., or Licensor, receivable represents the remaining external “out of pocket” clinical trial costs in excess of an agreed upon “cap” for clinical trials that were ongoing at the time the licensing 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 Company has not established a reserve against this receivable as it is deemed to be fully collectible and is considered non-current as of March 31, 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, or ASC 820, provides a single definition of fair value and a common framework for measuring fair value as well as new disclosure requirements for fair value measurements used in financial statements. Under ASC 820, fair value is determined based upon the exit price that would be received by a company to sell an asset or paid by a company to transfer a liability in an orderly transaction between market participants, exclusive of any transaction costs. Fair value measurements are determined by either the principal market or the most advantageous market. The principal market is the market with the greatest level of activity and volume for the asset or liability. Absent a principal market to measure fair value, the Company uses the most advantageous market, which is the market from which the Company would receive the highest selling price for the asset or pay the lowest price to settle the liability, after considering transaction costs. However, when using the most advantageous market, transaction costs are only considered to determine which market is the most advantageous and these costs are then excluded when applying a fair value measurement. ASC 820 creates a three-level hierarchy to prioritize the inputs used in the valuation techniques to derive fair values. The basis for fair value measurements for each level within the hierarchy is described below, with Level 1 having the highest priority and Level 3 having the lowest.
	Level 1:	Quoted prices in active markets for identical assets or liabilities.
	Level 2:	Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets.
	Level 3:	Valuations derived from valuation techniques in which one or more significant inputs are unobservable.
	Following are the major categories of assets measured at fair value on a recurring basis as of March 31, 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):
	31-Mar-15	Level 1		Level 2		Level 3		Total
	Cash equivalents	$	146,906	$	—	$	—	$	146,906
	Agency bond		—		5,002		—		5,002
	Marketable securities - U.S. government		—		11,518		—		11,518
	Marketable securities - corporate bonds		—		138,343		—		138,343
		$	146,906	$	154,863	$	—	$	301,769
	31-Dec-14	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 agency bonds, corporate bonds and U.S. government securities are exposed to price fluctuations. The fair value measurements for agency bonds, 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 March 31, 2015, were approximately $156.8 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 March 31, 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, or ASC 718, requires the fair value of all share-based payments to employees, including grants of stock options, to be recognized in the statement of operations over the requisite service period. Under ASC 718, employee option grants are generally valued at the grant date and those valuations do not change once they have been established. The fair value of each option award is estimated on the grant date using the Black-Scholes Option Pricing Method. As allowed by ASC 718 for companies with a short period of publicly traded stock history, the Company’s estimate of expected volatility is based on the average expected volatilities of a sampling of seven companies with similar attributes to the Company, including industry, stage of life cycle, size and financial leverage. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant valuation. Option forfeitures are calculated when the option is granted to reduce the option expense to be recognized over the life of the award and updated upon receipt of further information as to the amount of options expected to be forfeited. The option expense is “trued-up” upon the actual forfeiture of a stock option grant. Due to its limited history, the Company uses the simplified method to determine the expected life of the option grants.
	Performance shares:
	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 on the vesting dates will be lower or higher than the Company’s common stock price on the grant date. Based on the range of probabilities, the expense is calculated and recognized over the three-year vesting period.
	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. Diluted earnings per common share are the same as basic earnings per share because the assumed exercise of the Company’s outstanding options are anti-dilutive. For the three months ended March 31, 2015, potentially dilutive securities excluded from the calculations were 3,832,073 shares issuable upon exercise of options, 18,942 shares issuable as performance awards and 2,116,250 shares issuable upon exercise of a warrant. For the three months ended March 31, 2014, potentially dilutive securities excluded from the earnings per common share calculation were 3,059,849 issuable upon exercise of options, 28,411 issuable as performance shares and 2,116,250 shares issuable upon exercise of a warrant.
	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 or partial 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 2014, the Financial Accounting Standards Board, or the FASB, issued guidance requiring management to evaluate on a regular basis whether any conditions or events have arisen that could raise substantial doubt about the entity’s ability to continue as a going concern. The guidance (1) provides a definition for the term “substantial doubt,” (2) requires an evaluation every reporting period, interim periods included, (3) provides principles for considering the mitigating effect of management’s plans to alleviate the substantial doubt, (4) requires certain disclosures if the substantial doubt is alleviated as a result of management’s plans, (5) requires an express statement, as well as other disclosures, if the substantial doubt is not alleviated, and (6) requires an assessment period of one year from the date the financial statements are issued. The standard is effective for the Company’s reporting year beginning January 1, 2017 and early adoption is permitted. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements.
	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. 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, or ASU No. 2014-10, which eliminated certain financial reporting requirements of companies previously identified as development stage entities ( Topic 915 ). The amendments in this ASU simplify accounting guidance by removing all incremental financial reporting requirements for development stage entities. The amendments also reduce data maintenance and, for those entities subject to audit, audit costs by eliminating the requirement for development stage entities to present inception-to-date information in the statements of income, cash flows, and stockholder equity.  For public entities, these amendments begin to be effective for periods after December 31, 2014.  Early application of each of the amendments is permitted for any annual reporting period or interim period for which the entity’s financial statements have not yet been issued (public business entities) or made available for issuance (other entities). Upon adoption, entities will no longer present or disclose any information required by Topic 915.  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	3 Months Ended
	Mar. 31, 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):
		31-Mar-15		December 31, 2014
	Current:
	CRO services	$	2,486	$	2,451
	Other clinical development		2,757		2,525
	Insurance		800		1,007
	Other		314		309
			6,357		6,292
	Long-term:
	CRO services		6,290		6,352
	Other clinical development		3,352		3,464
	Insurance		113		130
	Other		56		61
			9,811		10,007
	Totals	$	16,168	$	16,299

Property_and_Equipment

Property and Equipment	3 Months Ended
	Mar. 31, 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:	31-Mar-15			December 31, 2014
	Leasehold improvements	$	1,438		$	1,217
	Computer equipment		1,315			1,272
	Telephone equipment		148			145
	Furniture and fixtures		1,016			848
			3,917			3,482
	Less: accumulated depreciation and amortization		(1,505	)		(1,325	)
	Totals	$	2,412		$	2,157

Accrued_Expenses

Accrued Expenses	3 Months Ended
	Mar. 31, 2015
Payables And Accruals [Abstract]
Accrued Expenses	Note 5—Accrued Expenses:
	Accrued expenses consisted of the following (in thousands):
		31-Mar-15		December 31, 2014
	Accrued CRO/licensor services	$	6,194	$	7,764
	Accrued other clinical development		3,787		2,541
	Accrued legal fees		357		195
	Accrued compensation		3,040		2,449
	Payroll taxes withheld for options exercised		—		16,414
	Other		91		81
	Totals	$	13,469	$	29,444
	Accrued CRO/licensor services represent the Company’s estimate of such costs as of March 31, 2015, 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	3 Months Ended
	Mar. 31, 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 $205.2 million, which is comprised of gross proceeds of approximately $218.5 million, offset by the underwriting discount and offering expenses of $13.3 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, or the 2011 Plan Amendment, was adopted by the Board of Directors on June 4, 2014, and the stockholders of the Company on June 10, 2014.    The 2011 Plan Amendment increased the number of shares reserved from 3,529,412 to 6,529,412.  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 months ended March 31, 2015 and 2014, were as follows (in thousands, except share and per share data):
		2015			2014
	Stock-based compensation:
	Options -
	Research and development, or R&D	$	15,254		$	3,226
	General and administrative, or G&A		4,704			1,341
	Performance shares: R&D		145			596
	Total share-based compensation expense	$	20,103		$	5,163
	Impact on basic and diluted net loss per share	$	0.64		$	0.17
	Weighted average shares (basic and diluted)		31,588,315			29,567,071
	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 March 31, 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 three months ended March 31, 2015 and 2014:
		2015			2014
	Dividend yield		0	%		0	%
	Expected volatility		63.1	%		81.3	%
	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			Weighted Average Remaining		Aggregate
					Average			Contractual Term (years)		Intrinsic Value
					Exercise					(in thousands)
					Price
	Outstanding at December 31, 2014		3,978,126		$	89.55			8.7	$	431,635
	Granted		270,500		$	218.13			9.5		—
	Forfeited		(30,198	)	$	146.5			—		—
	Exercised		(386,355	)	$	35.27			—	$	62,707
	Outstanding at March 31, 2015		3,832,073		$	103.65			8.6	$	513,719
	Unvested at March 31, 2015		2,523,156		$	145.01			9.2	$	236,086
	Exercisable at March 31, 2015		1,308,917		$	23.91			7.5	$	277,748
	At March 31, 2015, total estimated unrecognized employee compensation cost related to non-vested stock options and performance shares granted prior to that date were approximately $200.0 million and $0.8 million, respectively. These unrecognized expenses are expected to be recognized over a weighted-average period of 2.3 years for stock options and 1.3 years for performance shares. The weighted-average grant date fair value of options granted during the three months ended March 31, 2015 and 2014, were $125.41 per share and $73.89 per share, respectively.
					Weighted
					Average
					Grant-Date
	Stock options	Shares			Fair Value
	Nonvested shares at December 31, 2014		2,591,565		$	81.33
	Granted		270,500			125.41
	Vested/Issued		(308,711	)		44.13
	Forfeited		(30,198	)		88.17
	Nonvested shares at March 31, 2015		2,523,156		$	90.53

401k_Savings_Plan

401(k) Savings Plan	3 Months Ended
	Mar. 31, 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 $0.2 million and $0.1 million for the three months ended March 31, 2015 and 2014, respectively.

Significant_Accounting_Policie1

Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 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 Pfizer, Inc., or Licensor, receivable represents the remaining external “out of pocket” clinical trial costs in excess of an agreed upon “cap” for clinical trials that were ongoing at the time the licensing 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 Company has not established a reserve against this receivable as it is deemed to be fully collectible and is considered non-current as of March 31, 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, or ASC 820, provides a single definition of fair value and a common framework for measuring fair value as well as new disclosure requirements for fair value measurements used in financial statements. Under ASC 820, fair value is determined based upon the exit price that would be received by a company to sell an asset or paid by a company to transfer a liability in an orderly transaction between market participants, exclusive of any transaction costs. Fair value measurements are determined by either the principal market or the most advantageous market. The principal market is the market with the greatest level of activity and volume for the asset or liability. Absent a principal market to measure fair value, the Company uses the most advantageous market, which is the market from which the Company would receive the highest selling price for the asset or pay the lowest price to settle the liability, after considering transaction costs. However, when using the most advantageous market, transaction costs are only considered to determine which market is the most advantageous and these costs are then excluded when applying a fair value measurement. ASC 820 creates a three-level hierarchy to prioritize the inputs used in the valuation techniques to derive fair values. The basis for fair value measurements for each level within the hierarchy is described below, with Level 1 having the highest priority and Level 3 having the lowest.
	Level 1:	Quoted prices in active markets for identical assets or liabilities.
	Level 2:	Quoted prices for similar assets or liabilities in active markets; quoted prices for identical or similar instruments in markets that are not active; and model-derived valuations in which all significant inputs are observable in active markets.
	Level 3:	Valuations derived from valuation techniques in which one or more significant inputs are unobservable.
	Following are the major categories of assets measured at fair value on a recurring basis as of March 31, 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):
	31-Mar-15	Level 1		Level 2		Level 3		Total
	Cash equivalents	$	146,906	$	—	$	—	$	146,906
	Agency bond		—		5,002		—		5,002
	Marketable securities - U.S. government		—		11,518		—		11,518
	Marketable securities - corporate bonds		—		138,343		—		138,343
		$	146,906	$	154,863	$	—	$	301,769
	31-Dec-14	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 agency bonds, corporate bonds and U.S. government securities are exposed to price fluctuations. The fair value measurements for agency bonds, 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 March 31, 2015, were approximately $156.8 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 March 31, 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, or ASC 718, requires the fair value of all share-based payments to employees, including grants of stock options, to be recognized in the statement of operations over the requisite service period. Under ASC 718, employee option grants are generally valued at the grant date and those valuations do not change once they have been established. The fair value of each option award is estimated on the grant date using the Black-Scholes Option Pricing Method. As allowed by ASC 718 for companies with a short period of publicly traded stock history, the Company’s estimate of expected volatility is based on the average expected volatilities of a sampling of seven companies with similar attributes to the Company, including industry, stage of life cycle, size and financial leverage. The risk-free rate for periods within the contractual life of the option is based on the U.S. Treasury yield curve in effect at the time of grant valuation. Option forfeitures are calculated when the option is granted to reduce the option expense to be recognized over the life of the award and updated upon receipt of further information as to the amount of options expected to be forfeited. The option expense is “trued-up” upon the actual forfeiture of a stock option grant. Due to its limited history, the Company uses the simplified method to determine the expected life of the option grants.
	Performance shares:
	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 on the vesting dates will be lower or higher than the Company’s common stock price on the grant date. Based on the range of probabilities, the expense is calculated and recognized over the three-year vesting period.
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. Diluted earnings per common share are the same as basic earnings per share because the assumed exercise of the Company’s outstanding options are anti-dilutive. For the three months ended March 31, 2015, potentially dilutive securities excluded from the calculations were 3,832,073 shares issuable upon exercise of options, 18,942 shares issuable as performance awards and 2,116,250 shares issuable upon exercise of a warrant. For the three months ended March 31, 2014, potentially dilutive securities excluded from the earnings per common share calculation were 3,059,849 issuable upon exercise of options, 28,411 issuable as performance shares and 2,116,250 shares issuable upon exercise of a warrant.
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 or partial 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 2014, the Financial Accounting Standards Board, or the FASB, issued guidance requiring management to evaluate on a regular basis whether any conditions or events have arisen that could raise substantial doubt about the entity’s ability to continue as a going concern. The guidance (1) provides a definition for the term “substantial doubt,” (2) requires an evaluation every reporting period, interim periods included, (3) provides principles for considering the mitigating effect of management’s plans to alleviate the substantial doubt, (4) requires certain disclosures if the substantial doubt is alleviated as a result of management’s plans, (5) requires an express statement, as well as other disclosures, if the substantial doubt is not alleviated, and (6) requires an assessment period of one year from the date the financial statements are issued. The standard is effective for the Company’s reporting year beginning January 1, 2017 and early adoption is permitted. The Company does not expect the adoption of this standard to have a material impact on its consolidated financial statements.
	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. 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, or ASU No. 2014-10, which eliminated certain financial reporting requirements of companies previously identified as development stage entities ( Topic 915 ). The amendments in this ASU simplify accounting guidance by removing all incremental financial reporting requirements for development stage entities. The amendments also reduce data maintenance and, for those entities subject to audit, audit costs by eliminating the requirement for development stage entities to present inception-to-date information in the statements of income, cash flows, and stockholder equity.  For public entities, these amendments begin to be effective for periods after December 31, 2014.  Early application of each of the amendments is permitted for any annual reporting period or interim period for which the entity’s financial statements have not yet been issued (public business entities) or made available for issuance (other entities). Upon adoption, entities will no longer present or disclose any information required by Topic 915.  The Company adopted this standard on December 31, 2014, and it did not have a material impact on its consolidated financial statements.

Significant_Accounting_Policie2

Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 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 March 31, 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):
	31-Mar-15	Level 1		Level 2		Level 3		Total
	Cash equivalents	$	146,906	$	—	$	—	$	146,906
	Agency bond		—		5,002		—		5,002
	Marketable securities - U.S. government		—		11,518		—		11,518
	Marketable securities - corporate bonds		—		138,343		—		138,343
		$	146,906	$	154,863	$	—	$	301,769
	31-Dec-14	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)	3 Months Ended
	Mar. 31, 2015
Banking And Thrift [Abstract]
Components of Prepaid Expenses and Other	Prepaid expenses and other consisted of the following (in thousands):
		31-Mar-15		December 31, 2014
	Current:
	CRO services	$	2,486	$	2,451
	Other clinical development		2,757		2,525
	Insurance		800		1,007
	Other		314		309
			6,357		6,292
	Long-term:
	CRO services		6,290		6,352
	Other clinical development		3,352		3,464
	Insurance		113		130
	Other		56		61
			9,811		10,007
	Totals	$	16,168	$	16,299

Property_and_Equipment_Tables

Property and Equipment (Tables)	3 Months Ended
	Mar. 31, 2015
Property Plant And Equipment [Abstract]
Property and Equipment	Property and equipment consisted of the following (in thousands):
	Property and Equipment:	31-Mar-15			December 31, 2014
	Leasehold improvements	$	1,438		$	1,217
	Computer equipment		1,315			1,272
	Telephone equipment		148			145
	Furniture and fixtures		1,016			848
			3,917			3,482
	Less: accumulated depreciation and amortization		(1,505	)		(1,325	)
	Totals	$	2,412		$	2,157

Accrued_Expenses_Tables

Accrued Expenses (Tables)	3 Months Ended
	Mar. 31, 2015
Payables And Accruals [Abstract]
Accrued Expenses	Accrued expenses consisted of the following (in thousands):
		31-Mar-15		December 31, 2014
	Accrued CRO/licensor services	$	6,194	$	7,764
	Accrued other clinical development		3,787		2,541
	Accrued legal fees		357		195
	Accrued compensation		3,040		2,449
	Payroll taxes withheld for options exercised		—		16,414
	Other		91		81
	Totals	$	13,469	$	29,444

Stockholders_Equity_Tables

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2015
Equity [Abstract]
Recognized Expense of Share Based Compensation	Employee stock-based compensation for the three months ended March 31, 2015 and 2014, were as follows (in thousands, except share and per share data):
		2015			2014
	Stock-based compensation:
	Options -
	Research and development, or R&D	$	15,254		$	3,226
	General and administrative, or G&A		4,704			1,341
	Performance shares: R&D		145			596
	Total share-based compensation expense	$	20,103		$	5,163
	Impact on basic and diluted net loss per share	$	0.64		$	0.17
	Weighted average shares (basic and diluted)		31,588,315			29,567,071
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 March 31, 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		270,500			125.41
	Vested/Issued		(308,711	)		44.13
	Forfeited		(30,198	)		88.17
	Nonvested shares at March 31, 2015		2,523,156		$	90.53
Fair Value Options Weighted-Average Assumptions	The fair value of options granted to employees was estimated using the Black-Scholes Option Pricing Method (see Note 2—Significant Accounting Policies) with the following weighted-average assumptions used during the three months ended March 31, 2015 and 2014:
		2015			2014
	Dividend yield		0	%		0	%
	Expected volatility		63.1	%		81.3	%
	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			Weighted Average Remaining		Aggregate
					Average			Contractual Term (years)		Intrinsic Value
					Exercise					(in thousands)
					Price
	Outstanding at December 31, 2014		3,978,126		$	89.55			8.7	$	431,635
	Granted		270,500		$	218.13			9.5		—
	Forfeited		(30,198	)	$	146.5			—		—
	Exercised		(386,355	)	$	35.27			—	$	62,707
	Outstanding at March 31, 2015		3,832,073		$	103.65			8.6	$	513,719
	Unvested at March 31, 2015		2,523,156		$	145.01			9.2	$	236,086
	Exercisable at March 31, 2015		1,308,917		$	23.91			7.5	$	277,748

Business_and_Basis_of_Presenta1

Business and Basis of Presentation - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended
In Thousands, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014	Jan. 27, 2015
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net loss	($52,454)	($19,794)
Net cash used in operating activities	-50,023	-17,047
Net proceeds from issuance of common stock	205,196	129,440
Underwritten Public Offering
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Net proceeds from issuance of common stock			$205,200

Assets_Measured_at_Fair_Value_

Assets Measured at Fair Value on Recurring Basis (Detail) (Fair Value, Measurements, Recurring, USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	$146,906	$20,874
Total	301,769	123,662
U.S. government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	11,518	11,496
Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	138,343	91,292
Agency bond
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	5,002
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Cash equivalents	146,906	20,874
Total	146,906	20,874
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total	154,863	102,788
Level 2 | U.S. government
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	11,518	11,496
Level 2 | Corporate bonds
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	138,343	91,292
Level 2 | Agency bond
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Marketable securities	$5,002

Significant_Accounting_Policie3

Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended
In Millions, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Significant Accounting Policies [Line Items]
Cash and cash equivalents in excess of insured limits	156.8
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	3,832,073	3,059,849
Performance Awards
Significant Accounting Policies [Line Items]
Anti-dilutive securities excluded from the calculation of diluted earnings per share	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
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 $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	$6,357	$6,292
Prepaid expenses and other, long-term	9,811	10,007
Totals	16,168	16,299
CRO services
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	2,486	2,451
Prepaid expenses and other, long-term	6,290	6,352
Other clinical development
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	2,757	2,525
Prepaid expenses and other, long-term	3,352	3,464
Insurance
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	800	1,007
Prepaid expenses and other, long-term	113	130
Other
Prepaid Expenses [Line Items]
Prepaid expenses and other, current	314	309
Prepaid expenses and other, long-term	$56	$61

Property_and_Equipment_Detail

Property and Equipment (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$3,917	$3,482
Less: accumulated depreciation and amortization	-1,505	-1,325
Totals	2,412	2,157
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	1,438	1,217
Computer Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	1,315	1,272
Telephone Equipment
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	148	145
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property, Plant and Equipment, Gross	$1,016	$848

Accrued_Expenses_Detail

Accrued Expenses (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
In Thousands, unless otherwise specified
Payables And Accruals [Abstract]
Accrued CRO/licensor services	$6,194	$7,764
Accrued other clinical development	3,787	2,541
Accrued legal fees	357	195
Accrued compensation	3,040	2,449
Payroll taxes withheld for options exercised		16,414
Other	91	81
Totals	$13,469	$29,444

Stockholders_Equity_Additional

Stockholders Equity - Additional Information (Detail) (USD $)	3 Months Ended		0 Months Ended	1 Months Ended	0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 15, 2014	Jan. 31, 2014	Jan. 27, 2015	Jan. 21, 2015	Dec. 31, 2014
Stockholders Equity Note [Line Items]
Common stock, par value	$0.00						$0.00
Issuance of common stock, per share	$190
Net proceeds from issuance of common stock	$205,196,000	$129,440,000
Performance share expense recognition period	3 years
Weighted-average grant date fair value of options granted	$125.41	$73.89
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	800,000
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition	1 year 3 months 18 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	200,000,000
Estimated unrecognized employee compensation cost related to non-vested stock options granted, Weighted-average period of recognition	2 years 3 months 18 days
2011 Incentive Award Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance	3,529,412
Amended 2011 Incentive Award Plan
Stockholders Equity Note [Line Items]
Common stock shares reserved for issuance	6,529,412
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
Common stock price				$47.53
Maximum | 2011 Incentive Award Plan
Stockholders Equity Note [Line Items]
Stock options granted, term	10 years
Underwritten Public Offering
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)						1,000,000
Common stock, par value						$0.00
Issuance of common stock, per share						$190
Net proceeds from issuance of common stock					205,200,000
Gross proceeds from issuance of common stock					218,500,000
Public offering, underwriting discount and estimated offering expenses					$13,300,000
Underwritten Public Offering | Overallotment Option Exercise by Underwriters
Stockholders Equity Note [Line Items]
Issuance of common stock (in shares)						150,000

StockBased_Compensation_Expens

Stock-Based Compensation Expense (Detail) (USD $)	3 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$20,103	$5,163
Impact on basic and diluted net loss per share	$0.64	$0.17
Weighted average shares (basic and diluted)	31,588,315	29,567,071
Employee Stock Option | Research and development
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	15,254	3,226
Employee Stock Option | General and administrative
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	4,704	1,341
Performance Awards
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-based compensation expense	$145	$596

Performance_Shares_Detail

Performance Shares (Detail) (USD $)	Mar. 31, 2015	Dec. 31, 2014
Performance shares
Beginning balance, shares	18,942	18,942
Ending balance, shares	18,942	18,942
Weighted Average Grant-Date Fair Value
Beginning balance, Weighted Average Grant-Date Fair Value	$102.46	$102.46
Ending balance, Weighted Average Grant-Date Fair Value	$102.46	$102.46

Fair_Value_Options_WeightedAve

Fair Value Options Weighted-Average Assumptions (Detail) (Employee Stock Option)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Employee Stock Option
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Dividend yield	0.00%	0.00%
Expected volatility	63.10%	81.30%
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_Optio

Activity with Respect to Options Granted (Detail) (USD $)	3 Months Ended	12 Months Ended
In Thousands, except Share data, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Shares
Beginning balance, shares	3,978,126
Granted, shares	270,500
Forfeited, shares	-30,198
Exercised, shares	-386,355
Ending balance, shares	3,832,073	3,978,126
Unvested, shares	2,523,156	2,591,565
Exercisable, shares	1,308,917
Weighted Average Exercise Price
Beginning Balance, Weighted Average Exercise Price	$89.55
Granted, Weighted Average Exercise Price	$218.13
Forfeited, Weighted Average Exercise Price	$146.50
Exercised, Weighted Average Exercise Price	$35.27
Ending Balance, Weighted Average Exercise Price	$103.65	$89.55
Unvested, Weighted Average Exercise Price	$145.01
Exercisable, Weighted Average Exercise Price	$23.91
Weighted Average Remaining Contractual Term (years)
Beginning balance, Weighted Average Remaining Contractual Term (years)	8 years 7 months 6 days	8 years 8 months 12 days
Granted, Weighted Average Remaining Contractual Term (years)	9 years 6 months
Ending balance, Weighted Average Remaining Contractual Term (years)	8 years 7 months 6 days	8 years 8 months 12 days
Unvested, Weighted Average Remaining Contractual Term (years)	9 years 2 months 12 days
Exercisable, Weighted Average Remaining Contractual Term (years)	7 years 6 months
Aggregate Intrinsic Value
Beginning balance, Aggregate Intrinsic Value	$431,635
Exercised	62,707
Ending balance, Aggregate Intrinsic Value	513,719	431,635
Unvested, Aggregate Intrinsic Value	236,086
Exercisable, Aggregate Intrinsic Value	$277,748

Stock_Options_Detail

Stock Options (Detail) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Shares
Beginning balance, shares	2,591,565
Granted, shares	270,500
Vested/Issued	-308,711
Forfeited	-30,198
Ending balance, shares	2,523,156
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	$125.41	$73.89
Vested/Issued	$44.13
Forfeited	$88.17
Ending balance, Weighted Average Grant-Date Fair Value	$90.53

401K_Savings_Plan_Additional_I

401(K) Savings Plan - Additional Information (Detail) (USD $)	3 Months Ended
In Millions, unless otherwise specified	Mar. 31, 2015	Mar. 31, 2014
Savings Plan [Line Items]
Employer matching contribution expenses	$0.20	$0.10
First 3% of each Participant's Contributions
Savings Plan [Line Items]
Company's matching contributions to the 401(k)plan	100.00%
Second 2% of each Participant's Contributions
Savings Plan [Line Items]
Company's matching contributions to the 401(k)plan	50.00%