Tesaro (TSRO) 10-K 25 Feb 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Feb. 19, 2015	Jun. 30, 2014
Document and Entity Information
Entity Registrant Name	TESARO, Inc.
Entity Central Index Key	1491576
Document Type	10-K
Document Period End Date	31-Dec-14
Amendment Flag	FALSE
Current Fiscal Year End Date	-19
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Filer Category	Accelerated Filer
Entity Public Float			$631,362,000
Entity Common Stock, Shares Outstanding		36,110,407
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:
Cash and cash equivalents	$256,861	$130,310
Other current assets	1,735	4,029
Total current assets	258,596	134,339
Property and equipment, net	1,022	440
Other assets	4,284	799
Total assets	263,902	135,578
Current liabilities:
Accounts payable	6,089	1,869
Accrued expenses	16,750	10,541
Other current liabilities	1,526	13
Total current liabilities	24,365	12,423
Convertible notes, net	115,481
Other non-current liabilities		3
Commitments and contingencies (Notes 9 and 10)
Total liabilities	139,846	12,426
Stockholders' equity:
Preferred stock, $0.0001 par value; 10,000,000 shares authorized at both December 31, 2013 and December 31, 2014; no shares issued or outstanding at both December 31, 2013 and December 31, 2014
Common stock, $0.0001 par value; 100,000,000 shares authorized at both December 31, 2013 and December 31, 2014; 32,739,008 and 36,110,082 shares issued and outstanding at December 31, 2013 and December 31, 2014, respectively	4	3
Additional paid-in capital	474,562	302,647
Accumulated deficit	-350,510	-179,498
Total stockholders' equity	124,056	123,152
Total liabilities and stockholders' equity	$263,902	$135,578

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Condensed Consolidated Balance Sheets
Preferred stock, par value (in dollars per share)	$0.00	$0.00
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$0.00	$0.00
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	36,110,082	32,739,008
Common stock, shares outstanding	36,110,082	32,739,008

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Expenses:
Research and development	$118,425	$75,725	$47,200
General and administrative	23,935	14,780	6,715
Acquired in-process research and development	24,900	1,940	8,000
Total expenses	167,260	92,445	61,915
Loss from operations	-167,260	-92,445	-61,915
Interest expense	-3,776
Interest income	24	83	152
Net loss	-171,012	-92,362	-61,763
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	($4.79)	($2.93)	($4.51)
Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted (in shares)	35,739	31,559	13,696
Comprehensive loss	($171,012)	($92,362)	($61,763)

Consolidated_Statements_of_Con

Consolidated Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity (USD $)	Convertible Preferred Stock	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Accumulated Deficit [Member]	Series B Preferred Stock	Total
	Series B Preferred Stock	USD ($)	USD ($)	USD ($)	USD ($)		USD ($)
	USD ($)
Balance at Dec. 31, 2011		$64,348,000		$305,000	($25,373,000)		($25,068,000)
Balance (in shares) at Dec. 31, 2011		41,052,319
Balance (in shares) at Dec. 31, 2011			1,259,996
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of issuance costs	58,349,000		1,000	77,959,000			77,960,000
Shares sold	26,884,442		6,430,183
Conversion of convertible preferred stock into common stock		-122,697,000	2,000	122,695,000			122,697,000
Conversion of convertible preferred stock into common stock (in shares)		-67,936,761	19,410,490
Issuance of common stock resulting from exercise of stock options			19,016	33,000			33,000
Issuance of common stock as payment of Board of Directors fees in lieu of cash				253,000			253,000
Issuance of common stock as payment of Board of Directors fees in lieu of cash (in shares)			16,644
Stock-based compensation expense				1,550,000			1,550,000
Net loss					-61,763,000		-61,763,000
Balance at Dec. 31, 2012			3,000	202,795,000	-87,136,000		115,662,000
Balance (in shares) at Dec. 31, 2012			27,136,329
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of issuance costs				91,312,000			91,312,000
Shares sold			5,428,000
Issuance of common stock resulting from exercise of stock options				634,000			634,000
Issuance of common stock resulting from exercise of common stock (in shares)			162,480
Issuance of common stock resulting from Employee Stock Purchase Plan				147,000			147,000
Issuance of common stock resulting from Employee Stock Purchase Plan (in shares)			7,831
Issuance of common stock as payment of Board of Directors fees in lieu of cash				253,000			253,000
Issuance of common stock as payment of Board of Directors fees in lieu of cash (in shares)			4,368
Stock-based compensation expense				7,506,000			7,506,000
Net loss					-92,362,000		-92,362,000
Balance at Dec. 31, 2013			3,000	302,647,000	-179,498,000		123,152,000
Balance (in shares) at Dec. 31, 2013							0
Balance (in shares) at Dec. 31, 2013			32,739,008				32,739,008
Increase (Decrease) in Stockholders' Equity
Issuance of common stock, net of issuance costs			1,000	94,198,000			94,199,000
Shares sold			3,200,000
Issuance of common stock resulting from exercise of stock options				1,630,000			1,630,000
Issuance of common stock resulting from exercise of common stock (in shares)			159,747
Issuance of common stock resulting from Employee Stock Purchase Plan				249,000			249,000
Issuance of common stock resulting from Employee Stock Purchase Plan (in shares)			9,845
Issuance of common stock as payment of Board of Directors fees in lieu of cash				274,000			274,000
Issuance of common stock as payment of Board of Directors fees in lieu of cash (in shares)			10,411
Conversion option of convertible notes				84,984,000			84,984,000
Capped calls transaction cost charged to stockholders' equity				-20,829,000			-20,829,000
Cancellation of unvested restricted stock			-8,929
Stock-based compensation expense				11,409,000			11,409,000
Net loss					-171,012,000		-171,012,000
Balance at Dec. 31, 2014			$4,000	$474,562,000	($350,510,000)		$124,056,000
Balance (in shares) at Dec. 31, 2014							0
Balance (in shares) at Dec. 31, 2014			36,110,082				36,110,082

Consolidated_Statements_of_Con1

Consolidated Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity (Parenthetical) (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013
Convertible Preferred Stock | Series B Preferred Stock
Issuance of stock, price per share (in dollars per share)	$2.17
Issuance of stock, offering costs	$110
Common Stock
Issuance of stock, offering costs		6,601	6,392
Debt issuance costs paid		$2,859

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating activities
Net loss	($171,012)	($92,362)	($61,763)
Adjustments to reconcile net loss to net cash used in operating activities:
Acquired in-process research and development	24,900	1,940	8,000
Depreciation expense	349	179	64
Stock-based compensation expense	11,683	7,759	1,803
Non-cash interest expense	2,249
Loss on disposal of equipment	80
Changes in operating assets and liabilities:
Other assets	2,327	-3,112	1,020
Accounts payable	4,220	-1,301	2,565
Accrued expenses	6,209	1,996	5,565
Other liabilities	1,510	13	-11
Net cash used in operating activities	-117,485	-84,888	-42,757
Investing activities
Acquisition of product candidate and technology licenses and milestone payments	-24,900	-1,940	-8,000
Purchase of property and equipment	-1,011	-400	-165
Change in restricted cash			-200
Net cash used in investing activities	-25,911	-2,340	-7,965
Financing activities
Proceeds from issuance of convertible notes, net of issuance costs	194,698
Purchase of capped call options	-20,829
Proceeds from sale of common stock, net of issuance costs	94,199	91,312	77,960
Proceeds from exercise of stock options	1,663	634	33
Proceeds from issuance of common stock under Employee Stock Purchase Plan	249	147
Minimum tax withholding on share-based awards	-33
Proceeds from sale of convertible preferred stock, net of issuance costs			58,349
Net cash provided by financing activities	269,947	92,093	136,342
Increase in cash and cash equivalents	126,551	4,865	85,620
Cash and cash equivalents at beginning of period	130,310	125,445	39,825
Cash and cash equivalents at end of period	256,861	130,310	125,445
Non-cash investing and financing activities
Conversion of convertible preferred stock to common stock			$122,697

Nature_of_Business

Nature of Business	12 Months Ended
	Dec. 31, 2014
Nature of Business
Nature of Business
	1. Nature of Business
	The Company
	TESARO, Inc., or the Company or TESARO, was incorporated in Delaware on March 26, 2010 and commenced operations in May 2010.  Headquartered in Waltham, Massachusetts, TESARO is an oncology-focused biopharmaceutical company dedicated to improving the lives of cancer patients.  TESARO acquires, in-licenses and develops oncology product candidates and, if approved for marketing, intends to commercialize these products.  Since incorporation, primary activities have consisted of acquiring product candidates, advancing development of these product candidates, developing intellectual property, recruiting personnel and raising capital.  The Company intends to in-license or acquire additional product candidates across various stages of development, operates in one segment and has never earned revenue from its activities.  The Company is subject to a number of risks, including dependence on key individuals, the need to develop commercially viable products, competition from other companies, many of whom are larger and better capitalized, and the need to obtain adequate additional financing to fund the development and potential commercialization of its product candidates and further its in-licensing and acquisition activities.
	Public Offerings of Common Stock
	On June 27, 2012, the Company priced its initial public offering whereby it sold 6,000,000 shares of common stock at a price of $13.50 per share.  The shares began trading on the NASDAQ Global Select Market on June 28, 2012, and the transaction closed on July 3, 2012.  Immediately prior to the closing of the offering, all outstanding shares of convertible preferred stock converted into 19,410,490 shares of common stock.  On July 23, 2012, the underwriters purchased an additional 430,183 shares by exercising a portion of the over-allotment option granted to them in connection with the initial public offering.  As a result of the closing of the initial public offering and subsequent exercise of the over-allotment option, the Company received aggregate net proceeds of approximately $78.0 million, which is net of underwriting discounts and commissions and offering expenses.
	In connection with the completion of its initial public offering, on July 3, 2012, the Company filed an amended and restated certificate of incorporation, which, among other things, changed the number of authorized shares of common stock to 100,000,000 shares and preferred stock to 10,000,000 shares, both with a par value of $0.0001 per share.
	In March 2013, the Company sold 5,428,000 shares of common stock in an underwritten public offering pursuant to a registration statement on Form S-1, at a price of $18.00 per share, resulting in net proceeds of approximately $91.3 million, which is net of underwriting discounts and commissions and offering expenses.  In February 2014, the Company sold 3,200,000 shares of common stock in an underwritten public offering pursuant to an automatic shelf registration statement on Form S-3, at a price of $31.50 per share, resulting in net proceeds of approximately $94.2 million, which is net of underwriting discounts and commissions and offering expenses.
	Liquidity
	The Company has incurred significant operating losses since inception and has relied on its ability to fund its operations through private and public equity and debt financings, and management expects operating losses and negative operating cash flows to continue for the foreseeable future.  As the Company continues to incur losses, transition to profitability is dependent upon the successful development, approval, and commercialization of its product candidates and the achievement of a level of revenues adequate to support its cost structure.  The Company may never achieve profitability, and unless and until it does, the Company will continue to need to raise additional capital.  Management intends to fund future operations through additional public or private equity or debt offerings and may seek additional capital through arrangements with strategic partners or from other sources.
	Reverse Stock Split
	On June 19, 2012, the Company effected a 1 for 3.50 reverse stock split of its common stock.  The Company’s historical share and per share information has been retroactively adjusted to give effect to this reverse stock split.

Summary_of_Significant_Account

Summary of Significant Accounting Policies

12 Months Ended

Dec. 31, 2014

Summary of Significant Accounting Policies

Summary of Significant Accounting Policies

2. Summary of Significant Accounting Policies

Basis of Presentation

The Company’s consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiaries: TESARO UK Limited, TESARO Securities Corporation and TESARO Development, Ltd.  All significant intercompany balances and transactions have been eliminated in consolidation.  The consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP.

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance.  The Company views its operations and manages its business in one operating segment, which is the business of developing and commercializing safer and more effective oncology-focused therapeutics.

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, other comprehensive income and the related disclosures.  On an ongoing basis, management evaluates its estimates, including estimates related to accrued clinical trial and manufacturing development expenses and stock-based compensation expense.  Significant estimates in these consolidated financial statements include estimates made in connection with accrued research and development expenses, stock-based compensation expense and valuation of convertible notes.  The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances.  Actual results may differ from those estimates or assumptions.

Concentrations of Credit Risk and Off-Balance Sheet Risk

Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and cash equivalents.  The Company maintains its cash and cash equivalent balances primarily in the form of money market fund accounts with financial institutions that management believes are creditworthy.  The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimizes the exposure to concentration of credit risk.  The Company has no financial instruments with off-balance-sheet risk of loss.

Cash and Cash Equivalents

The Company considers all highly-liquid investments with original or remaining maturity from the date of purchase of three months or less to be cash equivalents.  Cash and cash equivalents include bank demand deposits and money market funds that invest primarily in certificate of deposits, commercial paper and U.S. government and U.S. government agency obligations.  Cash equivalents are reported at fair value.

Fair Value of Financial Instruments

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values.  The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs.  The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of investment credit quality.  The hierarchy defines three levels of valuation inputs:

Level 1 inputsQuoted prices in active markets for identical assets or liabilities

Level 2 inputsObservable inputs other than Level 1 inputs, including quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active

Level 3 inputsUnobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability

The following table presents information about the Company’s financial assets and liabilities that have been measured at fair value at December 31, 2013 and 2014 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):

December 31, 2013

Description

Balance Sheet Classification

Total

Level 1

Level 2

Level 3

Assets:

Money market funds

Cash and cash equivalents

$

128,801

$

128,801

$

—

$

—

Total assets

$

128,801

$

128,801

$

—

$

—

December 31, 2014

Description

Balance Sheet Classification

Total

Level 1

Level 2

Level 3

Assets:

Money market funds

Cash and cash equivalents

$

254,840

$

254,840

$

—

$

—

Total assets

$

254,840

$

254,840

$

—

$

—

The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term maturities.

In September 2014, the Company issued $201.3 million aggregate principal amount of 3.00% convertible senior notes due October 1, 2021, or the Convertible Notes.  Interest is payable semi-annually in arrears on April 1 and October 1 of each year, beginning on April 1, 2015.  As of December 31, 2014, the carrying value of the Convertible Notes was $115.5 million, net of unamortized discount, and the fair value of the principal amount was $251.1 million.  The Convertible Notes are discussed in more detail in Note 5, “Convertible Notes.”

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation.  Property and equipment are depreciated using the straight-line method over the estimated useful lives of the assets.  Leasehold improvements are amortized over the economic life of the asset or the remaining lease term, whichever is shorter.  Maintenance and repairs are expensed as incurred.  The following estimated useful lives were used to depreciate the Company’s assets:

Estimated Useful Life

Furniture and fixtures

5 years

Computer equipment and software

3 years

Leasehold improvements

Shorter of the useful life or the remaining lease term

Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized in income.

The Company reviews long-lived assets when events or changes in circumstances indicate the carrying value of the assets may not be recoverable.  Recoverability is measured by comparison of an asset’s book value to the estimated undiscounted future net cash flows that the asset is expected to generate.  If the estimated future undiscounted net cash flows are less than the book value, the asset is considered to be impaired, and the impairment loss to be recognized in income is measured as the amount by which the book value of the asset exceeds its fair value, which is measured based on the estimated discounted future net cash flows that the asset is expected to generate.  The Company recognized approximately $0.1 million of loss on the disposal of certain equipment during the year ended December 31, 2014.  No other impairment losses have been recorded through December 31, 2014.

Research and Development Expenses

Research and development costs are charged to expense as incurred and include:

·

license fees and milestone payments related to the acquisition of in-licensed products, which are reported on the statements of operations as acquired in-process research and development;

·

employee-related expenses, including salaries, bonuses, benefits, travel and stock-based compensation expense;

·

fees and expenses incurred under agreements with contract research organizations, investigative sites, research consortia and other entities in connection with the conduct of clinical trials and preclinical studies and related services, such as data management, laboratory and biostatistics services;

·

the cost of acquiring, developing and manufacturing active pharmaceutical ingredients, clinical trial materials and other research and development materials;

·

fees and costs related to regulatory filings and activities;

·

facilities, depreciation and other expenses, which include direct and allocated expenses for rent, utilities, maintenance of facilities, insurance and other supplies; and

·

other costs associated with clinical and preclinical activities.

Costs for certain development activities, such as clinical trials and manufacturing development activities, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors on their actual costs incurred or level of effort expended.  Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated balance sheets as prepaid or accrued research and development expenses.

Acquired In-Process Research and Development Expense

The Company has acquired the rights to develop and commercialize new product candidates.  Up-front payments that relate to the acquisition of a new drug compound, as well as milestone payments, are immediately expensed as acquired in-process research and development in the period in which they are incurred, provided that the new drug compound did not also include processes or activities that would constitute a “business” as defined under GAAP, the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no alternative future use. Royalties owed on future sales of the products licensed pursuant to the agreements are expensed in the period the related revenues are recognized.

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources.  Comprehensive loss was equal to net loss for all periods presented.

Income Taxes

The Company accounts for income taxes under the asset and liability method.  Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to affect taxable income.  Tax benefits are recognized when it is more likely than not that a tax position will be sustained during an audit.  Deferred tax assets are reduced by a valuation allowance if current evidence indicates that it is considered more likely than not that these benefits will not be realized.

Stock-Based Compensation Expense

Stock-based compensation is recognized as expense for each stock-based award based on its estimated fair value.  The Company determines the fair value of each equity-based award at its grant date using the Black-Scholes option pricing model.  The value of the award that is ultimately expected to vest is recognized as expense on a straight-line basis over the requisite service period.  The cumulative effect of any changes to the estimated forfeiture rates are accounted for as an adjustment to expense in the period of the change.

Net Loss Per Share

Basic and diluted net loss per common share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents.  The Company’s potentially dilutive shares, which include outstanding stock options, unvested restricted stock, and shares issuable upon conversion of the Convertible Notes, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.

The following table presents amounts that were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect (in thousands):

Years Ended December 31,

2012

2013

2014

Outstanding stock awards

2,134

2,853

3,742

Unvested restricted stock

349

102

4

2,483

2,955

3,746

In September 2014, in conjunction with the issuance of the Convertible Notes, the Company entered into capped call option transactions, or Capped Calls, with certain counterparties.  The Capped Calls are expected generally to reduce the potential dilution, and/or offset to an extent, the cash payments the Company is required to make in excess of the principal amount, upon conversion of the Convertible Notes in the event that the market price of the Company’s common stock is greater than the floor price of the Capped Calls.  See Note 5, “Convertible Notes”, for additional information.  As provided by the terms of the indenture underlying the Convertible Notes, the Company has a choice to settle the conversion obligation for the Convertible Notes in cash, shares or any combination of the two. The Company currently intends to settle the par value of the Convertible Notes in cash and any excess conversion premium in shares.  Accordingly, the par value of the Convertible Notes will not be included in the calculation of diluted income per share, but the dilutive effect of the conversion premium will be considered in the calculation of diluted net income per share using the treasury stock method.  During the period between issuance and December 31, 2014, the requisite criteria for conversion had not been met, and thus there would be no shares issuable under the conversion premium.  As such, no shares have been presented in the table above.

New Accounting Pronouncements - Recently Adopted

In June 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2014-10, which eliminates the concept of a development stage entity, or DSE, in its entirety from GAAP.  Under prior guidance, DSEs are required to report incremental information, including inception-to-date financial information, in their financial statements.  A DSE is an entity devoting substantially all of its efforts to establishing a new business and for which either planned principal operations have not yet commenced or have commenced but there has been no significant revenues generated from that business.  Entities classified as DSEs will no longer be subject to these incremental reporting requirements after adopting ASU No. 2014-10.  ASU No. 2014-10 is effective for fiscal years beginning after December 15, 2014, with early adoption permitted.  Retrospective application is required for the elimination of incremental DSE disclosures.  Prior to the issuance of ASU No. 2014-10, the Company had met the definition of a DSE since its inception.  The Company elected to adopt this ASU early, and therefore it has eliminated the incremental disclosures previously required of DSEs.

New Accounting Pronouncements - Recently Issued

In April 2014, the FASB issued ASU No. 2014-08, which amends guidance for reporting discontinued operations and disposals of components of an entity.  The amended guidance requires that a disposal representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results or a business activity classified as held for sale should be reported as discontinued operations.  The amendments also expand the disclosure requirements for discontinued operations and add new disclosure requirements for individually significant dispositions that do not qualify as discontinued operations.  This guidance is effective prospectively for fiscal years beginning after December 15, 2014 (early adoption is permitted only for disposals that have not been previously reported).  The Company does not expect the adoption of this guidance to have a material effect on its consolidated financial statements.

In May 2014, the FASB issued ASU No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers.  This ASU supersedes the revenue recognition requirements in Accounting Standards Codification, or ASC, Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers.  This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted.  Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application.  The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its potential future revenue streams and consolidated financial statements.

In June 2014, the FASB issued ASU No. 2014-12.  The amendments in this ASU apply to reporting entities that grant their employees share-based payments in which the terms of the award provide that a performance target can be achieved after a requisite service period.  The amendments require an entity to treat a performance target that affects vesting, and that could be achieved after the requisite service period, as a performance condition.  A reporting entity should apply existing guidance in ASC Topic 718 relating to awards with performance conditions that affect vesting to account for such awards.  The performance target should not be reflected in estimating the grant-date fair value of the award.  Compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered.  The amendments in this ASU are effective for annual reporting periods and interim periods within those annual reporting periods beginning after December 15, 2015, and early adoption is permitted.  The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements.

In August 2014, the FASB issued ASU No. 2014-15, which is intended to define management’s responsibility to evaluate whether there is substantial doubt about an organization’s ability to continue as a going concern and to provide related footnote disclosures.  Substantial doubt about an entity’s ability to continue as a going concern exists when relevant conditions and events, considered in the aggregate, indicate that it is probable that the entity will be unable to meet its obligations as they become due within one year after the date that the financial statements are issued (or are available to be issued).  ASU No. 2014-15 provides guidance to an organization’s management, with principles and definitions intended to reduce diversity in the timing and content of disclosures commonly provided by organizations in the footnotes of their financial statements.  ASU No. 2014-15 is effective for annual reporting periods ending after December 15, 2016, and for annual and interim periods thereafter.  Early adoption is permitted.  The Company is currently in the process of evaluating the impact of adoption of this guidance on its consolidated financial statements and related disclosures.

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2014
Property and Equipment
Property and Equipment
	3. Property and Equipment
	The following table presents property and equipment, at cost, and related accumulated depreciation (in thousands):
		December 31,
		2013			2014
	Furniture and fixtures	$	244		$	821
	Computer equipment and software	404			672
	Leasehold improvements	67			115
		715			1,608
	Less accumulated depreciation and amortization	(275		)	(586		)
	Total property and equipment, net	$	440		$	1,022
	Total depreciation expense amounted to $64,000, $179,000 and $349,000 for the years ended December 31, 2012, 2013 and 2014, respectively.

Accrued_Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2014
Accrued Expenses
Accrued Expenses
	4. Accrued Expenses
	The following table presents the components of accrued expenses (in thousands):
		December 31,
		2013		2014
	Research and development	$	7,422	$	11,433
	Salaries, bonuses and other compensation	2,462		4,012
	Professional services	389		529
	Other accrued expenses	268		776
	Total accrued expenses	$	10,541	$	16,750

Convertible_Notes

Convertible Notes	12 Months Ended
	Dec. 31, 2014
Convertible Notes
Convertible notes.
	5.  Convertible Notes
	On September 29, 2014, in a registered underwritten public offering, the Company completed the issuance of $201.3 million aggregate principal amount of Convertible Notes, which includes $26.3 million principal amount of Convertible Notes issued pursuant to the full exercise of an over-allotment option granted to the underwriters in the offering.  The Company received net proceeds of $194.7 million from the sale of the Convertible Notes, after deducting discounts, commissions and other expenses of $6.6 million.  In conjunction with the sale of the Convertible Notes, the Company used $20.8 million of the net proceeds to enter into separate Capped Calls, as described below.
	The Convertible Notes are governed by the terms of a Senior Debt Securities Indenture, or the Base Indenture, as supplemented by the First Supplemental Indenture relating to the Convertible Notes, or the Supplemental Indenture, and together with the Base Indenture, the Indenture, between the Company and U.S. Bank National Association, as trustee.  The Convertible Notes bear interest at a rate of 3.00% per annum, payable semi-annually on April 1 and October 1, beginning from April 1, 2015, and will be convertible into cash, shares of the Company’s common stock or a combination of cash and shares of the Company’s common stock, at the Company’s election.  The Convertible Notes will mature on October 1, 2021, unless earlier converted or repurchased in accordance with their terms.  Prior to the close of business on the business day immediately preceding April 1, 2021, the Convertible Notes will be convertible only upon the occurrence of certain events and during certain periods as discussed below, and thereafter, at any time until the close of business on the second scheduled trading day immediately preceding the maturity date.  The initial conversion price of the Convertible Notes is approximately $35.13 per share of common stock at an initial conversion rate of 28.4627 shares of the Company’s common stock per $1,000 principal amount of Convertible Notes, which represents a premium of approximately 35% over the last reported sale price of the Company’s common stock on September 23, 2014.
	The conversion rate is subject to adjustment from time to time upon the occurrence of certain events, including, but not limited to, the issuance of stock dividends and payment of cash dividends.  At any time prior to the close of business on the business day immediately preceding April 1, 2021, holders may convert their Convertible Notes at their option only under the following circumstances:
		-1		during any calendar quarter commencing after the calendar quarter ending on December 31, 2014 (and only during such calendar quarter), if the closing sale price of the Company’s common stock for at least 20 trading days (whether or not consecutive) during a period of 30 consecutive trading days ending on the last trading day of the immediately preceding calendar quarter in which the conversion occurs is greater than 130% of the conversion price on each applicable trading day;
		-2		during the five business day period after any ten consecutive trading day period, or the measurement period, in which the trading price per $1,000 principal amount of the Convertible Notes for each trading day of the measurement period was less than 98% of the product of the closing sale price of the Company’s common stock and the conversion rate on each such trading day; or
		-3		upon the occurrence of specified corporate events.
	On or after April 1, 2021 until the close of business on the second scheduled trading day immediately preceding the maturity date, holders may convert all or any portion of their Convertible Notes, in multiples of $1,000 principal amount, at the option of the holder regardless of the foregoing circumstances.
	If a make-whole adjustment event, as described in the Indenture, occurs and a holder elects to convert its Convertible Notes in connection with such make-whole adjustment event, such holder may be entitled to an increase in the conversion rate as described in the Indenture.
	The Company may not redeem the Convertible Notes prior to the maturity date and no “sinking fund” is provided for the Convertible Notes, which means that the Company is not required to periodically redeem or retire the Convertible Notes.  Upon the occurrence of certain fundamental changes involving the Company, holders of the Convertible Notes may require the Company to repurchase for cash all or part of their Convertible Notes at a repurchase price equal to 100% of the principal amount of the Convertible Notes to be repurchased, plus accrued and unpaid interest.
	The Indenture does not contain any financial covenants or restrictions on the payments of dividends, the incurrence of indebtedness or the issuance or repurchase of securities by the Company or any of its subsidiaries.  The Indenture contains customary terms and covenants and events of default.  If an event of default (other than certain events of bankruptcy, insolvency or reorganization involving the Company) occurs and is continuing, the Trustee by notice to the Company, or the holders of at least 25% in principal amount of the outstanding Convertible Notes by written notice to the Company and the Trustee, may declare 100% of the principal and accrued and unpaid interest, if any, on all of the Convertible Notes to be due and payable immediately.  Upon the occurrence of certain events of bankruptcy, insolvency or reorganization involving the Company, 100% of the principal and accrued and unpaid interest, if any, on all of the Convertible Notes will become due and payable automatically.  Notwithstanding the foregoing, the Indenture provides that, to the extent the Company elects and for up to 180 days after the occurrence of an event of default relating to certain failures by the Company to comply with certain reporting covenants, the remedy for such an event of default consists exclusively of the right to receive additional interest on the Convertible Notes.
	The terms of the Indenture provide the Company with the option to settle the Convertible Notes in cash, common stock, or a combination of cash and common stock.  As a result, in accordance with Accounting Standards Codification, or ASC, 470-20, Debt with Conversion and Other Options, the Company separately accounts for the liability and equity components of the Convertible Notes by allocating the principal between the liability component and the embedded conversion option, or equity component. Based on market data available for publicly traded, senior, unsecured corporate bonds issued by companies in the same industry and with similar maturity, the Company estimated the implied interest rate, assuming no conversion option. Assumptions used in the estimate represent what market participants would use in pricing the liability component, including market interest rates, credit standing, and yield curves, all of which are defined as Level 2 observable inputs. The estimated implied interest rate was applied to the Convertible Notes, which resulted in a fair value of the liability component of $113.4 million upon issuance, calculated as the present value of implied future payments based on the $201.3 million aggregate principal amount. The equity component of the Convertible Notes was recognized as a debt discount, recorded in additional paid-in capital, and represents the difference between the aggregate principal of the Convertible Notes and the fair value of the Convertible Notes without conversion option on their issuance date.  The debt discount is amortized to interest expense using the effective interest method over seven years, or the life of the Convertible Notes.  The equity component is not remeasured as long as it continues to meet the conditions for equity classification.  As of December 31, 2014 it continues to meet the conditions for equity classification. In addition, third-party transaction costs are required to be allocated to the liability and equity components based on their relative values.
	The Company’s outstanding convertible note balances at December 31, 2014 consisted of the following (in thousands):
			December 31, 2014
	Liability component:
	Principal		$	201,250
	Less: debt discount, net		(85,769		)
	Net carrying amount		$	115,481
	Equity component		$	87,843
	In connection with the issuance of the Convertible Notes, the Company incurred approximately $6.6 million of debt issuance costs, which primarily consisted of underwriting, legal and other professional fees, which the Company allocated to the liability and equity components in a manner consistent with the allocation of the principal, as described above.  Of the total $6.6 million of debt issuance costs, $2.9 million were allocated to the equity component and recorded as a reduction to additional paid-in capital and $3.7 million were allocated to the liability component and recorded as non-current assets on the balance sheet.  The portion allocated to the liability component is amortized to interest expense over the expected life of the Convertible Notes using the effective interest method.
	The Company determined the expected life of the debt was equal to the seven year contractual term of the Convertible Notes. As of December 31, 2014, the carrying value of the Convertible Notes was $115.5 million and the fair value of the Convertible Notes approximated $251.1 million.  The effective interest rate on the liability component is 12.9%. The following table sets forth total interest expense recognized related to the Convertible Notes during the year ended December 31, 2014 (in thousands):
			Year Ended
			December 31, 2014
	Contractual interest expense		$	1,526
	Amortization of debt discount		2,074
	Amortization of debt issuance costs		176
	Total interest expense		$	3,776
	The Company has evaluated the Indenture for derivatives pursuant to ASC 815, Derivatives and Hedging, and identified an embedded derivative that requires bifurcation as the feature is not clearly and closely related to the host instrument. The embedded derivative is a default provision, which could require additional interest payments. The Company has determined that the fair value of this embedded derivative was nominal as of December 31, 2014.
	In conjunction with the offering of the Convertible Notes, the Company entered into privately-negotiated Capped Calls with certain counterparties.  Each Capped Call is an integrated instrument consisting of a call option on the Company’s common stock purchased by the Company from the counterparties with an exercise price equal to the conversion price of $35.13 per share for the underlying number of shares and a cap component that incorporates a cap price of $45.54 per share.  The cap component is economically equivalent to a call option sold by the Company to the counterparties for the underlying number of shares with an exercise price of $45.54 per share.  As an integrated instrument, the settlement of the Capped Calls coincides with the maturity date of the Convertible Notes.  The aggregate cost of the Capped Calls of $20.8 million was recorded in stockholders’ equity and will not be remeasured.

Convertible_Preferred_Stock_an

Convertible Preferred Stock and Stockholders' Equity	12 Months Ended
	Dec. 31, 2014
Convertible Preferred Stock and Stockholders' Equity
Convertible Preferred Stock and Stockholders' Equity
	6. Convertible Preferred Stock and Stockholders’ Equity
	As of December 31, 2014, the authorized capital stock of the Company consisted of 10,000,000 shares of preferred stock and 100,000,000 shares of common stock, both with a par value of $0.0001, of which no shares of preferred stock were issued or outstanding and 36,110,082 shares of common stock were issued and outstanding.
	Convertible Preferred Stock
	On March 21, 2012, the Company sold 26,884,442 shares of Series B convertible preferred stock to existing investors pursuant to the Series B Purchase Agreement at a price of $2.175 per share, resulting in net proceeds to the Company of approximately $58.3 million.  The Company evaluated the terms of the Series B convertible preferred stock and concluded that an investor’s right to acquire additional shares of Series B convertible preferred stock was not legally detachable and therefore was embedded and not required to be separated from Series B convertible preferred stock.
	The Company accounts for potentially beneficial conversion features in accordance with Accounting Standards Codification, or ASC, 470-20, Debt with Conversion and Other Options.  At the time of each of the issuances of convertible preferred stock, the common stock into which the Series A and B convertible preferred stock is convertible had a fair value less than the effective conversion price of the convertible preferred stock and, as such, there was no intrinsic value on the respective commitment dates.
	On July 3, 2012, immediately prior to the closing of the Company’s initial public offering, all 67,936,761 shares outstanding of all series of the Company’s convertible preferred stock were converted into 19,410,490 shares of its common stock.  As of December 31, 2014, the Company did not have any convertible preferred stock authorized, issued or outstanding.
	Preferred Stock
	The Company’s certificate of incorporation authorizes its board of directors to issue preferred stock from time to time in one or more series.  The rights, preferences, restrictions, qualifications and limitations of such stock are determined by the board of directors.
	Common Stock
	On June 27, 2012, the Company priced its initial public offering whereby the Company sold 6,000,000 shares of common stock at a price of $13.50 per share.  The shares began trading on the NASDAQ Global Select Market on June 28, 2012, and the transaction closed on July 3, 2012.  Immediately prior to the closing of the offering, all outstanding shares of convertible preferred stock converted into 19,410,490 shares of common stock.  On July 23, 2012, the underwriters purchased an additional 430,183 shares of common stock by exercising a portion of the over-allotment option granted to them in connection with the initial public offering.  As a result of the closing of the initial public offering and subsequent exercise of the over-allotment option, the Company received aggregate net proceeds of approximately $78.0 million, which is net of underwriting discounts and commissions and offering expenses.
	In March 2013, the Company sold 5,428,000 shares of common stock, in an underwritten public offering at a price to the public of $18.00 per share, resulting in gross proceeds of approximately $97.7 million.  Net proceeds to the Company after deducting fees, commissions and other expenses related to the offering were approximately $91.3 million.  The shares were issued pursuant to a registration statement on Form S-1.
	In February 2014, the Company sold 3,200,000 shares of common stock, in an underwritten public offering at a price to the public of $31.50 per share, resulting in gross proceeds of approximately $100.8 million.  Net proceeds to the Company after deducting fees, commissions and other expenses related to the offering were approximately $94.2 million. The shares were issued pursuant to an automatic shelf registration statement on Form S-3.
	The holders of common stock are entitled to one vote per share on all matters to be voted upon by the stockholders of the Company.  Subject to the preferences that may be applicable to any outstanding shares of preferred stock, the holders of common stock are entitled to receive ratably such dividends, if any, as may be declared by the Company’s board of directors.

StockBased_Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2014
Stock-Based Compensation
Stock-Based Compensation
	7. Stock-Based Compensation
	The following table presents stock-based compensation expense as reflected in the Company’s consolidated statements of operations and comprehensive loss (in thousands):
			Years Ended December 31,
			2012			2013			2014
	Research and development		$	544		$	2,034		$	4,954
	General and administrative		1,259			5,725			6,729
	Total stock-based compensation expense		$	1,803		$	7,759		$	11,683
	The Company maintains several equity compensation plans, including the TESARO, Inc. 2012 Omnibus Incentive Plan, or the 2012 Incentive Plan, the 2010 Stock Incentive Plan, or the 2010 Incentive Plan, and the 2012 Employee Stock Purchase Plan, or the 2012 ESPP.  Terms of stock award agreements, including vesting requirements, are determined by the board of directors, subject to the provisions of the individual plans.  To date, options granted to employees by the Company generally vest 25% one year from the vesting start date and 75% in equal installments over the subsequent 36 months and are exercisable from the date of grant for a period of ten years.
	2012 Omnibus Incentive Plan
	On April 27, 2012, the stockholders of the Company approved the 2012 Incentive Plan, which had been previously adopted by the board of directors.  Upon effectiveness of the 2012 Incentive Plan, the Company ceased making awards under the 2010 Incentive Plan.  The 2012 Incentive Plan allows the Company to grant awards for up to 1,428,571 shares of common stock plus the number of shares of common stock available for grant under the 2010 Incentive Plan as of the effectiveness of the 2012 Incentive Plan (which is an additional 6,857 shares) plus that number of shares of common stock related to awards outstanding under the 2010 Incentive Plan that terminate by expiration, forfeiture, cancellation, cash settlement or otherwise.  Each year starting with 2014, the number of shares available for grants of awards under the 2012 Incentive Plan will be increased automatically on January 1 by a number of shares of common stock equal to the lesser of 4% of the shares of common stock outstanding at such time or the number of shares determined by the Company’s board of directors.  Accordingly, effective January 1, 2014 and 2015, the number of shares authorized for issuance under the 2012 Incentive Plan was increased by 1,309,560 shares and 1,444,403 shares, respectively.  Awards under the 2012 Incentive Plan may include the following award types: stock options, which may be either incentive stock options or nonqualified stock options; stock appreciation rights; restricted stock; restricted stock units; dividend equivalent rights; performance shares; performance units; cash-based awards; other stock-based awards, including unrestricted shares; or any combination of the foregoing.  The exercise price of stock options granted under the 2012 Incentive Plan is equal to the closing price of a share of the Company’s common stock on the grant date.  As of December 31, 2014, there were 423,759 shares available for grant under the 2012 Incentive Plan, prior to taking into account the additional shares authorized for issuance as of January 1, 2015, as described above.
	2010 Stock Incentive Plan
	In connection with the Company’s formation, the Company adopted the TESARO, Inc. 2010 Incentive Plan, under which it was authorized to grant stock-based awards to purchase up to 1,981,130 shares of common stock as of January 1, 2012.  As of April 27, 2012, the Company ceased making awards under the 2010 Incentive Plan and the remaining 6,857 shares available for future grants were added to the total number of shares reserved for issuance under the 2012 Incentive Plan.  For options granted under the 2010 Incentive Plan, the exercise price equaled the estimated fair value of the common stock as determined by the board of directors on the date of grant.  As of December 31, 2014, there are no shares available for grant under the 2010 Incentive Plan.
	Restricted Common Stock
	In connection with the Company’s formation, the founders purchased an aggregate of 1,071 shares of common stock at a nominal per share purchase price.  On May 10, 2010, in connection with the Company’s sale of Series A-1 convertible preferred stock, each such share was reclassified into 1,000 shares of common stock, or an aggregate of 1,071,426 shares of common stock, or the Founder Common.  The shares of Founder Common were issued subject to restricted stock agreements between the Company and each founder.  The Founder Common shares vested in full as of March 26, 2014.
	On February 7, 2011, the Company granted to the founders and one employee an aggregate of 188,570 shares of common stock as compensation for services provided, or the 2011 Awards.  The 2011 Awards are subject to the 2010 Incentive Plan and various restrictions pursuant to restricted stock agreements between the Company and each recipient, including restrictions on transfer and a Company right of repurchase.  The 2011 Awards vested in full as of January 6, 2015.
	The Company records stock-based compensation expense for common stock subject to repurchase, or restricted common stock grants, based on the grant date intrinsic value for employees.  The Company recorded stock-based compensation expense of $24,000, $669,000 and $116,000, respectively, for the years ended December 31, 2012, 2013 and 2014 associated with restricted common stock grants.  The totals for the years ended December 31, 2013 and 2014 include $646,000 and $96,000, respectively, related to accounting for awards held by a non-employee consultant.
	The following table presents a summary of the Company’s restricted stock activity and related information:
					Weighted-average
					grant date fair
			Shares		value per share
	Unvested restricted stock at December 31, 2013		102,412		$	0.76
	Granted		—		—
	Vested		(89,332	)	0.23
	Forfeited		(8,929	)	0.53
	Unvested restricted stock at December 31, 2014		4,151		$	12.79
	The weighted-average grant date fair value of restricted stock granted during the year ended December 31, 2013 was $46.22 per share.  There were no grants of restricted stock during the years ended December 31, 2012 or 2014.  The total grant date fair value of restricted stock that vested during the years ended December 31, 2012, 2013 and 2014 was $47,000, $25,000, and $21,000, respectively.  At December 31, 2014, the total unrecognized compensation cost related to unvested restricted stock was insignificant.
	Stock Options
	The following table presents a summary of the Company’s stock option activity and related information:
			Shares		Weighted-average			Weighted-average		Aggregate
					exercise price per			remaining contractual		intrinsic value
					share			term (years)		(in thousands)
	Outstanding at December 31, 2013		2,852,793		$	12.77		8.4		$	46,708
	Granted		1,320,573		30.65
	Exercised		(157,113	)	10.59
	Cancelled		(289,924	)	17.75
	Outstanding at December 31, 2014		3,726,329		$	18.82		8.1		$	69,176
	Vested at December 31, 2014		1,552,249		$	10.16		7.2		$	42,428
	Vested and expected to vest at December 31, 2014 (a)		3,646,747		$	18.56		8		$	68,628
		(a)		This represents the number of vested options as of December 31, 2014, plus the number of unvested options expected to vest as of December 31, 2014, based on the unvested options at December 31, 2014, adjusted for the estimated forfeiture rate.
	The fair value of each stock option was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions:
			Years Ended December 31,
			2012		2013		2014
	Dividend yield		—		—		—
	Volatility		66% - 71%		73% - 78%		69% - 76%
	Risk-free interest rate		0.89% - 1.56%		1.07% - 2.05%		1.65% - 2.07%
	Expected term (years)		6.25		5.50 - 6.25		5.50 - 6.08
	The Company uses the simplified method as prescribed by SEC Staff Accounting Bulletin No. 107, Share-Based Payment, to calculate the expected term, as it does not have sufficient historical exercise data to provide a reasonable basis upon which to estimate the expected term for options granted.  The expected term is applied to all stock option grants as a whole, as the Company does not expect substantially different exercise or post-vesting termination behavior among its population.  The computation of expected volatility is based on the historical volatility of a representative group of public biotechnology and life sciences companies with similar characteristics to the Company, including early stage of product development and therapeutic focus.  The risk-free interest rate is based on a treasury instrument whose term is consistent with the expected term of the stock options.  Management assesses expected forfeitures based on the experience of the Company and recognizes compensation costs only for those equity awards expected to vest.
	The Company recorded stock-based compensation expense associated with stock options of $1,526,000, $6,770,000, and $11,081,000 for the years ended December 31, 2012, 2013 and 2014, respectively.  The totals for the years ended December 31, 2013 and 2014 include $1,132,000 and $297,000, respectively, related to accounting for awards held by a non-employee consultant.  The weighted-average grant date fair values of options granted in the years ended December 31, 2012, 2013 and 2014 were $5.29, $18.48 and $20.33 per share, respectively.  The aggregate intrinsic value of options exercised during the years ended December 31, 2012, 2013 and 2014 was $0.2 million, $4.8 million and $3.4 million, respectively.  The intrinsic value of a stock option is the amount by which the fair market value of the underlying stock on the exercise date exceeds the exercise price of the stock option.
	At December 31, 2014, there was $30.7 million of total unrecognized compensation cost related to unvested stock options, which the Company expects to recognize over a remaining weighted-average period of 2.5 years.
	In October 2012, June 2013 and June 2014, as provided for under the 2012 Incentive Plan, the Company issued 16,644, 4,368 and 10,411 shares of common stock, respectively, with aggregate values of $0.3 million for all three periods, to certain non-employee board members who elected to receive shares of common stock in lieu of cash, as payment of fees owed them for services as members of the Company’s board of directors.
	During September 2013, the Company’s former Executive Vice President, Chief Financial Officer, Treasurer and Secretary, or the former CFO, resigned from his employment with the Company effective August 31, 2013 and transitioned to serving the Company as a non-employee consultant through March 31, 2014.  In accordance with the terms of the 2012 Incentive Plan and the 2010 Incentive Plan, stock awards previously granted to the former CFO under these plans continued to vest through March 31, 2014.  As a result, beginning in September 2013, the Company accounted for unvested stock awards previously granted to the former CFO as non-employee awards.  The Company recorded stock-based compensation expense based on the fair values of awards as measured on their vesting dates, and the fair values of any unvested awards were remeasured at each financial reporting date until they vested, with any increases or decreases in fair value recorded as stock-based compensation expense.  Fair values of stock options were determined on each measurement date using the Black-Scholes option pricing model, and fair values of restricted stock awards were equal to the fair market value of the Company’s common stock on the measurement date.  During the years ended December 31, 2013 and 2014, the Company recorded incremental stock-based compensation expense of $1.8 million and $0.4 million, respectively, associated with these awards (options and restricted stock awards), as the result of the change in status of the former CFO.
	In August 2014, the Company granted 2,750 stock options to certain non-employee consultants, all of which were outstanding as of December 31, 2014 with a weighted-average exercise price of $29.04 per share.  The Company records stock-based compensation expense based on the fair values of awards as measured on their vesting dates.  Fair values of stock options are determined on each measurement date using the Black-Scholes option pricing model.  During the year ended December 31, 2014, 2,750 stock options were granted to certain non-employee consultants, with a weighted-average grant date fair value of $17.50, and no options were vested, exercised or forfeited.  The fair value of the shares was estimated using the Black-Scholes option-pricing model, using the fair value of the common stock and the following assumptions: zero dividend yield; volatility of 69%; risk-free interest rate of 1.87%; and expected term of 5.50 years.  There were no option grants to non-employee consultants during the years ended December 31, 2012 or 2013.
	Restricted Stock Units
	In August 2014, the Company issued 19,500 restricted stock units, or RSUs, to certain employees.  These stock awards have performance conditions, pursuant to which vesting of the award is contingent on the occurrence of certain milestone events. As a result, the related compensation cost is recognized as an expense, starting when the milestone becomes probable of being met, through the remaining performance period. The expense recognized for these awards is based on the grant date fair value of the Company’s common stock multiplied by the number of units granted, net of estimated forfeitures.
	The following table presents a summary of the Company’s restricted stock unit activity and related information:
					Weighted-average
					grant date fair
			Shares		value per share
	Unvested restricted stock units at December 31, 2013		—		$	—
	Granted		19,500		29.04
	Vested		(2,634	)	29.04
	Forfeited		—		—
	Withheld for taxes (a)		(1,266	)	29.04
Unvested restricted stock units at December 31, 2014		15,600		$	29.04
	(a)		The Company has elected to pay cash equal to the minimum amount required to be withheld for income tax purposes instead of issuing the shares of common stock. The cash is remitted to the appropriate taxing authority.
The weighted-average grant date fair values of RSUs granted during the year ended December 31, 2014 was $29.04 per share.  There were no grants of RSUs during the years ended December 31, 2012 or 2013.  The total grant date fair value of RSUs that vested during the years ended December 31, 2012, 2013 and 2014 was $0, $0, and $113,000, respectively, based upon the number of RSUs vested multiplied by the closing stock price of the Company’s common stock on the grant date.  As of December 31, 2014, there was approximately $453,000 of unrecognized compensation cost related to the RSU grants that is expected to be recognized over a weighted-average period of approximately 0.75 years.
Employee Stock Purchase Plan
On June 6, 2012, the board of directors adopted the 2012 ESPP, and the stockholders approved it on June 18, 2012, to be effective in connection with the closing of the Company’s initial public offering.  A total of 275,000 shares of common stock were originally approved for future issuance under the 2012 ESPP pursuant to purchase rights granted to the Company’s employees or to employees of the Company’s designated subsidiaries.  As of December 31, 2014, 257,324 shares remained available for issuance.  The 2012 ESPP provides for consecutive six-month offering periods, during which participating employees may elect to have a portion of their compensation withheld and used for the purchase of common stock at the end of each offering period.  The purchase price is equal to 85% of the lower of the fair market value of a share of common stock on the first trading day of each offering period or the fair market value of a share of common stock on the last trading day of the offering period, and is limited by participant to $25,000 in fair value of common stock per year.  The 2012 ESPP will terminate on June 6, 2022, the tenth anniversary of the date of initial adoption of the plan.  For the years ended December 31, 2013 and 2014, the Company issued a total of 7,831 and 9,845 shares, respectively, of common stock under the 2012 ESPP and recognized $67,000 and $99,000, respectively, in related stock-based compensation expense.
Due to its operating losses in all periods to date, the Company has not recorded any tax benefits associated with stock-based compensation expense and option exercises.  Tax benefits will be recorded when realized.

Income_Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2014
Income Taxes
Income Taxes
	The following table presents a reconciliation of income (loss) before the provision for (benefit from) income taxes during the years ended December 31, 2012, 2013 and 2014 (in thousands):
		Years Ended December 31,
		2012			2013			2014
	United States	$	(61,763	)	$	(87,953	)	$	(141,119	)
	Foreign	—			(4,409		)	(29,893		)
	(Loss) income before provision for (benefit from) income taxes	$	(61,763	)	$	(92,362	)	$	(171,012	)
	For the years ended December 31, 2012, 2013 and 2014, the Company did not record any current or deferred income tax provisions or benefits.
	The following table presents a reconciliation of income tax expense (benefit) at the statutory federal income tax rate to the effective income tax rate as reflected in the consolidated financial statements:
		Years Ended December 31,
		2012		2013		2014
	Federal income tax (benefit)/expense at statutory rate	(34.0	)%	(34.0	)%	(34.0	)%
	State income tax benefit	(5.4	)	(5.1	)	(4.4	)
	Permanent items	0.4		0.8		0.7
	Foreign rate differential	0		1.6		5.9
	Federal research and development credit	0		(2.5	)	(1.4	)
	Change in valuation allowance	39		39.2		33.2
	Effective income tax rate	0	%	0	%	0	%
	Deferred income tax assets and liabilities are determined based upon temporary differences between the financial reporting and tax bases of assets and liabilities and are measured using the enacted tax rates and laws that will be in effect when the differences are expected to reverse.
	The following table presents the principal components of the Company’s deferred tax assets and liabilities (in thousands):
		December 31,
		2013			2014
	Deferred tax assets:
	Federal net operating loss carryforwards	$	50,265		$	86,163
	State net operating loss carryforwards	7,762			13,270
	Depreciation and amortization	5,793			14,647
	Tax credit carryforwards	2,984			5,780
	Stock-based compensation	2,248			4,891
	Other	779			1,289
	Total deferred tax assets	69,831			126,040
	Less: valuation allowance	(69,831		)	(101,399		)
	Net deferred tax assets	$	—		$	24,641
	Deferred tax liability:
	Debt discount on convertible notes		—			(24,641	)
	Net deferred taxes	$	—		$	—
	As of December 31, 2014, the Company had federal net operating loss carryforwards of approximately $259.2 million and state net operating loss carryforwards of $257.6 million, which are available to reduce future taxable income.  Approximately $5.8 million of the federal and state net operating loss carryforwards will result in an increase to additional paid-in capital if and when these carryforwards are used to reduce federal and state income taxes payable. The Company also had federal research and development tax credit carryforwards of $5.9 million and state research and development tax credit carryforwards of $1.4 million, which may be used to offset future tax liabilities.
	These federal and state operating loss carryforwards, or NOL, and tax credit carryforwards will expire at various dates through 2034.  The NOL and tax credit carryforwards are subject to review and possible adjustment by the Internal Revenue Service, or the IRS, and state tax authorities.  These carryforwards may become subject to an annual limitation in the event of certain cumulative changes in the ownership interest of significant shareholders over a three-year period in excess of 50%, as defined under Sections 382 and 383 of the Internal Revenue Code, respectively, as well as similar state provisions.  This could limit the amount of tax attributes that can be utilized annually to offset future taxable income or tax liabilities.  The amount of the annual limitation is determined based on the value of the Company immediately prior to the ownership change.  Subsequent ownership changes may further affect the limitation in future years.
	ASC 740 requires a valuation allowance to reduce the deferred tax assets reported if, based on the weight of available evidence, it is more likely than not that some portion or all of the deferred tax assets will not be realized.  After consideration of all the evidence, both positive and negative, the Company continues to maintain a valuation allowance for the full amount of the 2014 deferred tax asset because it is more likely than not that the deferred tax asset will not be realized. The valuation allowance increased by $31.6 million from December 31, 2013 to December 31, 2014, primarily due to an increase in net operating losses.
	The Company has gross unrecognized tax benefits related to research and development credits of $1.0 million and $0.5 million, respectively, as of December 31, 2014 and 2013. At December 31, 2014, $1.0 million represented the amount of unrecognized tax benefits that, if recognized, would be offset by an adjustment to the valuation allowance.  The Company has not, as yet, conducted a study of its research and development credit carryforwards. Such a study could result in an adjustment to those carryforwards; however, until a study is completed and any adjustment is known, no amounts are being presented as an uncertain tax position. A full valuation allowance has been provided against all of the Company’s tax credit carryforwards, including its research and development credits and, if an adjustment is required, this adjustment would be offset by an adjustment to the valuation allowance. Thus, there would be no impact to the consolidated balance sheet position or statement of operations if an adjustment were required.
	The Company’s policy is to recognize both interest and penalties related to unrecognized tax benefits in income tax expense.  Due to its historical net loss position, the Company has not recognized any interest or penalties related to unrecognized tax benefits.
	The statute of limitations for assessment by the IRS and state tax authorities remains open for all tax years. Since the Company is in a loss carryforward position, the Company is generally subject to examination by the U.S. federal, state and local income tax authorities for all tax years in which a loss carryforward is available.  The Company files a United States federal income tax return and a Commonwealth of Massachusetts state income tax return.  There are currently no federal or state audits in process.

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2014
Employee Benefit Plan
Employee Benefit Plan
	9. Employee Benefit Plan
	In 2010, the Company adopted a retirement plan, which is qualified under section 401(k) of the Internal Revenue Code, for its U.S. employees.  The plan allows eligible employees to defer, at the employee’s discretion, pre-tax or post-tax compensation up to the IRS annual limits.  Company contributions may be made at the discretion of the board of directors.
	Effective as of January 1, 2012, the Company amended its 401(k) plan to provide for employer matching contributions equal to (1) 100% of employee deferral contributions up to a deferral rate of 3% of compensation, plus (2) 50% of employee deferral contributions up to a deferral rate of an additional 2% of compensation.  During the years ended December 31, 2012, 2013 and 2014, the Company made aggregate matching contributions of $137,000, $277,000 and $484,000, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies
Commitments and Contingencies
	10. Commitments and Contingencies
	The Company leases approximately 53,200 square feet of office space in Waltham, Massachusetts under a non-cancelable operating lease agreement.  The term of the lease commenced April 1, 2013 and continues through June 30, 2017.  The lease agreement provides for one month of free rent with respect to a portion of the leased premises.  The Company recognizes rental expense on a straight-line basis over the respective lease term including any free rent periods.  The following table presents future minimum rental commitments, by fiscal year and in the aggregate, as of December 31, 2014 (in thousands):
		Operating
		Leases
	2015	$	1,697
	2016	1,697
	2017	849
	Thereafter	—
	Total minimum lease payments	$	4,243
	The Company recorded $166,000, $647,000 and $1,525,000 in rent expense for the years ended December 31, 2012, 2013 and 2014, respectively.
	The Company has entered into agreements with certain vendors for the provision of services, including services related to data management, clinical operation support and companion diagnostic development, that the Company is not contractually able to terminate for convenience and avoid any and all future obligations to the vendors.  Under such agreements, the Company is contractually obligated to make certain minimum payments to the vendors, with the exact amounts in the event of termination to be based on the timing of the termination and the exact terms of the agreement.
	Litigation
	The Company may periodically become subject to legal proceedings and claims arising in connection with ongoing business activities, including claims or disputes related to patents that have been issued or that are pending in the field of research on which the Company is focused.  The Company is not a party to any litigation and does not have contingency reserves established for any litigation liabilities.

License_Agreements

License Agreements	12 Months Ended
	Dec. 31, 2014
License Agreements
License Agreements
	11. License Agreements
	Rolapitant In-License
	In December 2010, the Company entered into a license agreement with OPKO Health, Inc., or OPKO, to obtain an exclusive, royalty-bearing, sublicensable worldwide license to research, develop, manufacture, market and sell rolapitant.  The license agreement also extended to an additional, backup compound, SCH900978, to which the Company has the same rights and obligations as rolapitant, but which the Company is not currently advancing.  Under the OPKO license, the Company is obligated to use commercially reasonable efforts to conduct all preclinical, clinical, regulatory and other activities necessary to develop and commercialize rolapitant.  Under the terms of the OPKO license, the Company paid OPKO $6.0 million upon signing the agreement and issued 1,500,000 shares of its Series O convertible Preferred Stock.  At the time of the license transaction, the fair value of Series O convertible Preferred Stock was determined to be $630,000.  The Company is also required to make development milestone payments to OPKO of up to an aggregate of $30.0 million if specified regulatory and initial commercial sales milestones are achieved.  In addition, the Company is required to make additional milestone payments to OPKO of up to an aggregate of $85.0 million if specified levels of annual net sales of rolapitant are achieved.  If commercial sales of rolapitant commence, the Company is required to pay OPKO tiered royalties on the amount of annual net sales achieved in the United States and Europe at percentage rates that range from the low teens to the low twenties, which the Company expects will result in an effective royalty rate in the low teens.  The royalty rate on annual net sales outside of the United States and Europe is slightly above the single digits.  If the Company elects to develop and commercialize rolapitant in Japan through a third-party licensee the Company will share equally with OPKO all amounts received by it in connection with such activities under the Company’s agreement with such third party, subject to certain exceptions and deductions.  OPKO also retains an option to become the exclusive distributor of such products in Latin America, provided that OPKO exercises that option within a defined period following specified regulatory approvals in the United States.  The Company is responsible for all preclinical, clinical, regulatory and other activities necessary to develop and commercialize rolapitant.  There were no ongoing clinical trials for rolapitant at the time of its acquisition.  As of the date of acquisition, none of the assets acquired had alternative future uses, nor had they reached a stage of technological feasibility.  As no processes or activities that would constitute a “business” were acquired along with the license, the transaction was accounted for as an asset acquisition by recording the entire purchase price as acquired in-process research and development expense of $6.6 million.  As of December 31, 2014, the Company has made one milestone payment of $5.0 million under this license agreement, in connection with the acceptance of the oral rolapitant NDA for review by the FDA in November 2014.
	TSR-011 In-License
	In March 2011, the Company entered into a license agreement with Amgen, Inc., or Amgen, under which it received an exclusive, royalty bearing, sublicensable worldwide license under certain of Amgen’s patent rights to research, develop, manufacture, market and sell licensed ALK inhibitor compounds, including TSR-011.  The Company is also responsible for using commercially reasonable efforts to conduct all preclinical, clinical, regulatory and other activities necessary to develop and commercialize an ALK product.  In the event that the Company wishes to sublicense any of the development and commercialization rights to any third party, it is required to grant to Amgen a right of first negotiation with respect to the rights it proposes to sublicense.  Under the terms of the license agreement, in 2011 the Company made an up-front payment to Amgen of $0.5 million.  In November 2012, in connection with the initiation of its Phase 1/2a clinical trial for TSR-011, the Company made a milestone payment to Amgen of $1.0 million.  The Company is required to make total milestone payments to Amgen of up to an aggregate of $138.0 million if specified clinical development, regulatory, initial commercialization and annual net product sales milestones are achieved.  If commercial sales of a product commence, the Company will pay Amgen royalties at percentage rates ranging from the mid-single digits to slightly above the single digits based on cumulative worldwide net sales.  At the time of the license transaction, TSR-011 was a preclinical compound.  As of the date of acquisition, none of the assets acquired had alternative future uses, nor had they reached a stage of technological feasibility.  As no processes or activities that would constitute a “business” were acquired along with the license, the transaction was accounted for as an asset acquisition and the entire purchase price of $0.5 million was recorded as acquired in-process research and development expense.  Milestone payments are also recorded as acquired in-process research and development and expensed as achieved.
	Niraparib In-License
	In May 2012, the Company entered into a license agreement with Merck Sharp & Dohme Corp., a subsidiary of Merck & Co., Inc., or Merck, under which the Company obtained exclusive, worldwide rights to certain patents and non-exclusive rights to certain Merck know-how, to research, develop, manufacture, market and sell niraparib and a backup compound, MK-2512, for all therapeutic and prophylactic uses in humans.  The Company is not currently advancing MK-2512.  Under the Merck license, the Company is obligated to use diligent efforts to develop and commercialize a licensed product.  Under the terms of the license agreement, the Company was required to make an up-front payment to Merck of $7.0 million in June 2012.  The Company is also required to make milestone payments to Merck of up to $57.0 million in development and regulatory milestones for the first indication, up to $29.5 million in development and regulatory milestones for each successive indication, and up to $87.5 million in one-time sales milestones based on the achievement of annual sales objectives.  If commercial sales of niraparib commence, the Company will pay Merck tiered royalties at a percentage rate in the low teens based on worldwide annual net sales.  As of the date of acquisition, none of the assets acquired had alternative future uses, nor had they reached a stage of technological feasibility.  As no processes or activities that would constitute a “business” were acquired along with the license, the transaction has been accounted for as an asset acquisition and the entire purchase price of $7.0 million has been recorded as acquired in-process research and development expense.  The Company has made two milestone payments to Merck, one in the amount of $1.9 million upon dosing of the first patient in the Phase 3 ovarian cancer clinical trial in July 2013, which the Company refers to as its NOVA trial, and one in the amount of $0.9 million upon dosing of the first patient in the Phase 3 breast cancer clinical trial in April 2014, which the Company refers to as its BRAVO trial.
	Technology Licenses
	In October 2012, the Company entered into two license agreements with AstraZeneca UK Limited, having aggregate upfront payments of $0.4 million.  These agreements provide the Company with the exclusive right to certain methods of treating patients with PARP inhibitors solely with respect to niraparib.  Under certain circumstances, the Company may be required to make milestone and royalty payments to AstraZeneca UK Limited based on the achievement of certain development and regulatory milestone events with regard to niraparib, and on net sales of niraparib.  The Company made milestone payments totaling $0.2 million and $0.1 million to AstraZeneca during the years ended December 31, 2013 and 2014, respectively.
	Immuno-Oncology Platform License
	In March 2014, the Company entered into a collaboration and exclusive license agreement with AnaptysBio, Inc., or AnaptysBio, a privately-held therapeutic antibody company.  Under the terms of this agreement, the Company obtained an exclusive, royalty-bearing, sublicensable worldwide license to research, develop, manufacture, market and sell products based on AnaptysBio’s proprietary technology for the discovery, generation and optimization of certain specified immunotherapy antibodies.  Specifically, the Company received exclusive rights to monospecific antibody product candidates targeting TIM-3, LAG-3 and PD-1 (TSR-042) and dual-reactive antibody product candidates targeting PD-1/TIM-3 and PD-1/LAG-3.  The Company executed an amendment in November 2014 to add an additional dual-reactive combination.  Under the agreement, AnaptysBio is responsible for performing initial discovery and development of therapeutic antibodies, with the goal of generating immunotherapy antibodies for use in the treatment of cancer.  The Company is responsible for the performance and costs of all subsequent preclinical, clinical, regulatory, manufacturing and other activities necessary to develop and commercialize antibodies selected under each of four development programs and is obligated to use commercially reasonable efforts to research, develop or commercialize at least one product under each development program.
	Under the terms of the agreement, the Company made an up-front, non-creditable and non-refundable cash payment of $17.0 million to AnaptysBio in March 2014.  Under the terms of the amendment, the Company made an up-front, non-creditable and non-refundable cash payment of $2.0 million in December 2014.  The Company is also required to reimburse AnaptysBio on a quarterly basis for up to two years from the effective date of the agreement for specified costs incurred by AnaptysBio in its initial discovery and development activities covered by the agreement.  Programs may be extended by mutual agreement of the parties, and the Company can terminate on a program-by-program basis by providing 90 days prior written notice, subject to a wind-down period during which the Company’s obligation to reimburse AnaptysBio for specified costs would continue.  For each of the four development programs, the Company will be required to make milestone payments to AnaptysBio of up to $18.0 million if certain research and development milestone events are achieved, and up to an additional $90.0 million of milestone payments if certain U.S. and non-U.S. regulatory submissions and approvals occur in initial and subsequent indications.  The Company will be required to pay AnaptysBio tiered single-digit royalties, on a product-by-product basis, on worldwide annual net sales, and additional commercial milestone payments if specified levels of annual net sales of a product are attained.
	As of the date of the license transaction, none of the assets acquired had alternative future uses, nor had they reached a stage of technological feasibility.  As the processes or activities that were acquired along with the license do not constitute a “business”, the transaction has been accounted for as an asset acquisition.  In addition, the Company has concluded that it is reimbursing AnaptysBio at fair value for the research services called for under the agreement.  As a result of these factors, the up-front payments totaling $19.0 million have been recorded as acquired in-process research and development expense, and no portion of the payments has been ascribed to the future services to be provided to the Company by AnaptysBio.  For the year ended December 31, 2014, the Company recorded approximately $4.6 million of research and development expense, associated with amounts due to AnaptysBio under the collaboration.  As of December 31, 2014, the Company has not made any additional milestone payments under this agreement.

Consolidated_Quarterly_Financi

Consolidated Quarterly Financial Data - Unaudited	12 Months Ended
	Dec. 31, 2014
Consolidated Quarterly Financial Data - Unaudited
Consolidated Quarterly Financial Data - Unaudited
	12. Consolidated Quarterly Financial Data - Unaudited
	The following table presents unaudited consolidated quarterly financial data for the years ended December 31, 2013 and 2014 (in thousands, except per share data):
			Three Months Ended
			March 31,			June 30,			Sept. 30,			Dec. 31,			March 31,			June 30,			Sept. 30,			Dec. 31,
			2013			2013			2013			2013			2014			2014			2014			2014
	Expenses:
	Research and development		$	16,503		$	18,177		$	22,163		$	18,882		$	28,117		$	30,569		$	29,925		$	29,814
	General and administrative		2,400			3,412			4,503			4,465			4,688			5,587			6,263			7,397
	Acquired in-process research and development		—			—			1,940		(a)	—			17,000		(b)	900		(c)	—			7,000		(d)
	Total expenses		18,903			21,589			28,606			23,347			49,805			37,056			36,188			44,211
	Loss from operations		(18,903		)	(21,589		)	(28,606		)	(23,347		)	(49,805		)	(37,056		)	(36,188		)	(44,211		)
	Interest expense		—			—			—			—			—			—			(42		)	(3,734		)
	Interest income		34			25			17			7			5			5			4			10
	Net loss		$	(18,869	)	$	(21,564	)	$	(28,589	)	$	(23,340	)	$	(49,800	)	$	(37,051	)	$	(36,226	)	$	(47,935	)
	Net loss per share - basic and diluted		$	(0.66	)	$	(0.67	)	$	(0.88	)	$	(0.72	)	$	(1.43	)	$	(1.03	)	$	(1.01	)	$	(1.33	)
	Weighted-average shares - basic and diluted		28,798			32,336			32,453			32,597			34,856			35,982			36,029			36,071
		(a)		In the quarter ended September 30, 2013, the Company made a milestone payment to Merck for niraparib as a result of the first patient dosing in the NOVA trial, which occurred in July 2013.
		(b)		In the quarter ended March 31, 2014, the Company paid an up front fee of $17.0 million to AnaptysBio related to the immuno-oncology platform.
		(c)		In the quarter ended June 30, 2014, the Company made a milestone payment to Merck for niraparib as a result of the first patient dosing in the BRAVO trial, which occurred in April 2014.
		(d)		In the quarter ended December 31, 2014 the Company made a $5.0 million milestone payment to OPKO related to the acceptance of the oral rolapitant NDA for review by the FDA, as well as an up front payment of $2.0 million to AnaptysBio related to the immuno-oncology platform amendment.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)

12 Months Ended

Dec. 31, 2014

Summary of Significant Accounting Policies

Basis of Presentation

Basis of Presentation

The Company’s consolidated financial statements reflect the operations of the Company and its wholly-owned subsidiaries: TESARO UK Limited, TESARO Securities Corporation and TESARO Development, Ltd.  All significant intercompany balances and transactions have been eliminated in consolidation.  The consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP.

Segment Information

Segment Information

Operating segments are defined as components of an enterprise about which separate discrete information is available for evaluation by the chief operating decision maker, or decision-making group, in deciding how to allocate resources and in assessing performance.  The Company views its operations and manages its business in one operating segment, which is the business of developing and commercializing safer and more effective oncology-focused therapeutics.

Use of Estimates

Use of Estimates

The preparation of financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities and expenses, other comprehensive income and the related disclosures.  On an ongoing basis, management evaluates its estimates, including estimates related to accrued clinical trial and manufacturing development expenses and stock-based compensation expense.  Significant estimates in these consolidated financial statements include estimates made in connection with accrued research and development expenses, stock-based compensation expense and valuation of convertible notes.  The Company bases its estimates on historical experience, known trends and other market-specific or other relevant factors that it believes to be reasonable under the circumstances.  Actual results may differ from those estimates or assumptions.

Concentrations of Credit Risk and Off-Balance Sheet Risk

Concentrations of Credit Risk and Off-Balance Sheet Risk

Financial instruments that potentially subject the Company to concentrations of credit risk are primarily cash and cash equivalents.  The Company maintains its cash and cash equivalent balances primarily in the form of money market fund accounts with financial institutions that management believes are creditworthy.  The Company’s investment policy includes guidelines on the quality of the institutions and financial instruments and defines allowable investments that the Company believes minimizes the exposure to concentration of credit risk.  The Company has no financial instruments with off-balance-sheet risk of loss.

Cash and Cash Equivalents

Cash and Cash Equivalents

The Company considers all highly-liquid investments with original or remaining maturity from the date of purchase of three months or less to be cash equivalents.  Cash and cash equivalents include bank demand deposits and money market funds that invest primarily in certificate of deposits, commercial paper and U.S. government and U.S. government agency obligations.  Cash equivalents are reported at fair value.

Fair Value of Financial Instruments

Fair Value of Financial Instruments

The Company is required to disclose information on all assets and liabilities reported at fair value that enables an assessment of the inputs used in determining the reported fair values.  The fair value hierarchy prioritizes valuation inputs based on the observable nature of those inputs.  The fair value hierarchy applies only to the valuation inputs used in determining the reported fair value of the investments and is not a measure of investment credit quality.  The hierarchy defines three levels of valuation inputs:

Level 1 inputsQuoted prices in active markets for identical assets or liabilities

Level 2 inputsObservable inputs other than Level 1 inputs, including quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active

Level 3 inputsUnobservable inputs that reflect the Company’s own assumptions about the assumptions market participants would use in pricing the asset or liability

The following table presents information about the Company’s financial assets and liabilities that have been measured at fair value at December 31, 2013 and 2014 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):

December 31, 2013

Description

Balance Sheet Classification

Total

Level 1

Level 2

Level 3

Assets:

Money market funds

Cash and cash equivalents

$

128,801

$

128,801

$

—

$

—

Total assets

$

128,801

$

128,801

$

—

$

—

December 31, 2014

Description

Balance Sheet Classification

Total

Level 1

Level 2

Level 3

Assets:

Money market funds

Cash and cash equivalents

$

254,840

$

254,840

$

—

$

—

Total assets

$

254,840

$

254,840

$

—

$

—

The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term maturities.

In September 2014, the Company issued $201.3 million aggregate principal amount of 3.00% convertible senior notes due October 1, 2021, or the Convertible Notes.  Interest is payable semi-annually in arrears on April 1 and October 1 of each year, beginning on April 1, 2015.  As of December 31, 2014, the carrying value of the Convertible Notes was $115.5 million, net of unamortized discount, and the fair value of the principal amount was $251.1 million.  The Convertible Notes are discussed in more detail in Note 5, “Convertible Notes.”

Property and Equipment

Property and Equipment

Property and equipment are stated at cost, less accumulated depreciation.  Property and equipment are depreciated using the straight-line method over the estimated useful lives of the assets.  Leasehold improvements are amortized over the economic life of the asset or the remaining lease term, whichever is shorter.  Maintenance and repairs are expensed as incurred.  The following estimated useful lives were used to depreciate the Company’s assets:

Estimated Useful Life

Furniture and fixtures

5 years

Computer equipment and software

3 years

Leasehold improvements

Shorter of the useful life or the remaining lease term

Upon retirement or sale, the cost of the disposed asset and the related accumulated depreciation are removed from the accounts and any resulting gain or loss is recognized in income.

The Company reviews long-lived assets when events or changes in circumstances indicate the carrying value of the assets may not be recoverable.  Recoverability is measured by comparison of an asset’s book value to the estimated undiscounted future net cash flows that the asset is expected to generate.  If the estimated future undiscounted net cash flows are less than the book value, the asset is considered to be impaired, and the impairment loss to be recognized in income is measured as the amount by which the book value of the asset exceeds its fair value, which is measured based on the estimated discounted future net cash flows that the asset is expected to generate.  The Company recognized approximately $0.1 million of loss on the disposal of certain equipment during the year ended December 31, 2014.  No other impairment losses have been recorded through December 31, 2014.

Research and Development Expenses

Research and Development Expenses

Research and development costs are charged to expense as incurred and include:

·

license fees and milestone payments related to the acquisition of in-licensed products, which are reported on the statements of operations as acquired in-process research and development;

·

employee-related expenses, including salaries, bonuses, benefits, travel and stock-based compensation expense;

·

fees and expenses incurred under agreements with contract research organizations, investigative sites, research consortia and other entities in connection with the conduct of clinical trials and preclinical studies and related services, such as data management, laboratory and biostatistics services;

·

the cost of acquiring, developing and manufacturing active pharmaceutical ingredients, clinical trial materials and other research and development materials;

·

fees and costs related to regulatory filings and activities;

·

facilities, depreciation and other expenses, which include direct and allocated expenses for rent, utilities, maintenance of facilities, insurance and other supplies; and

·

other costs associated with clinical and preclinical activities.

Costs for certain development activities, such as clinical trials and manufacturing development activities, are recognized based on an evaluation of the progress to completion of specific tasks using data such as patient enrollment, clinical site activations, or information provided to the Company by its vendors on their actual costs incurred or level of effort expended.  Payments for these activities are based on the terms of the individual arrangements, which may differ from the pattern of costs incurred, and are reflected in the consolidated balance sheets as prepaid or accrued research and development expenses.

Acquired In-Process Research and Development Expense

Acquired In-Process Research and Development Expense

The Company has acquired the rights to develop and commercialize new product candidates.  Up-front payments that relate to the acquisition of a new drug compound, as well as milestone payments, are immediately expensed as acquired in-process research and development in the period in which they are incurred, provided that the new drug compound did not also include processes or activities that would constitute a “business” as defined under GAAP, the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no alternative future use. Royalties owed on future sales of the products licensed pursuant to the agreements are expensed in the period the related revenues are recognized.

Comprehensive Loss

Comprehensive Loss

Comprehensive loss is defined as the change in equity of a business enterprise during a period from transactions and other events and circumstances from non-owner sources.  Comprehensive loss was equal to net loss for all periods presented.

Income Taxes

Income Taxes

The Company accounts for income taxes under the asset and liability method.  Deferred tax assets and liabilities are recognized for the future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases using enacted tax rates in effect for the year in which the differences are expected to affect taxable income.  Tax benefits are recognized when it is more likely than not that a tax position will be sustained during an audit.  Deferred tax assets are reduced by a valuation allowance if current evidence indicates that it is considered more likely than not that these benefits will not be realized.

Stock-Based Compensation Expense

Stock-Based Compensation Expense

Stock-based compensation is recognized as expense for each stock-based award based on its estimated fair value.  The Company determines the fair value of each equity-based award at its grant date using the Black-Scholes option pricing model.  The value of the award that is ultimately expected to vest is recognized as expense on a straight-line basis over the requisite service period.  The cumulative effect of any changes to the estimated forfeiture rates are accounted for as an adjustment to expense in the period of the change.

Net Loss Per Share

Net Loss Per Share

Basic and diluted net loss per common share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents.  The Company’s potentially dilutive shares, which include outstanding stock options, unvested restricted stock, and shares issuable upon conversion of the Convertible Notes, are considered to be common stock equivalents and are only included in the calculation of diluted net loss per share when their effect is dilutive.

The following table presents amounts that were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect (in thousands):

Years Ended December 31,

2012

2013

2014

Outstanding stock awards

2,134

2,853

3,742

Unvested restricted stock

349

102

4

2,483

2,955

3,746

In September 2014, in conjunction with the issuance of the Convertible Notes, the Company entered into capped call option transactions, or Capped Calls, with certain counterparties.  The Capped Calls are expected generally to reduce the potential dilution, and/or offset to an extent, the cash payments the Company is required to make in excess of the principal amount, upon conversion of the Convertible Notes in the event that the market price of the Company’s common stock is greater than the floor price of the Capped Calls.  See Note 5, “Convertible Notes”, for additional information.  As provided by the terms of the indenture underlying the Convertible Notes, the Company has a choice to settle the conversion obligation for the Convertible Notes in cash, shares or any combination of the two. The Company currently intends to settle the par value of the Convertible Notes in cash and any excess conversion premium in shares.  Accordingly, the par value of the Convertible Notes will not be included in the calculation of diluted income per share, but the dilutive effect of the conversion premium will be considered in the calculation of diluted net income per share using the treasury stock method.  During the period between issuance and December 31, 2014, the requisite criteria for conversion had not been met, and thus there would be no shares issuable under the conversion premium.  As such, no shares have been presented in the table above.

New Accounting Pronouncements - Recently Adopted

New Accounting Pronouncements - Recently Adopted

In June 2014, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update, or ASU, No. 2014-10, which eliminates the concept of a development stage entity, or DSE, in its entirety from GAAP.  Under prior guidance, DSEs are required to report incremental information, including inception-to-date financial information, in their financial statements.  A DSE is an entity devoting substantially all of its efforts to establishing a new business and for which either planned principal operations have not yet commenced or have commenced but there has been no significant revenues generated from that business.  Entities classified as DSEs will no longer be subject to these incremental reporting requirements after adopting ASU No. 2014-10.  ASU No. 2014-10 is effective for fiscal years beginning after December 15, 2014, with early adoption permitted.  Retrospective application is required for the elimination of incremental DSE disclosures.  Prior to the issuance of ASU No. 2014-10, the Company had met the definition of a DSE since its inception.  The Company elected to adopt this ASU early, and therefore it has eliminated the incremental disclosures previously required of DSEs.

New Accounting Pronouncements - Recently Issued

New Accounting Pronouncements - Recently Issued

In April 2014, the FASB issued ASU No. 2014-08, which amends guidance for reporting discontinued operations and disposals of components of an entity.  The amended guidance requires that a disposal representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results or a business activity classified as held for sale should be reported as discontinued operations.  The amendments also expand the disclosure requirements for discontinued operations and add new disclosure requirements for individually significant dispositions that do not qualify as discontinued operations.  This guidance is effective prospectively for fiscal years beginning after December 15, 2014 (early adoption is permitted only for disposals that have not been previously reported).  The Company does not expect the adoption of this guidance to have a material effect on its consolidated financial statements.

In May 2014, the FASB issued ASU No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers.  This ASU supersedes the revenue recognition requirements in Accounting Standards Codification, or ASC, Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers.  This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted.  Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application.  The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its potential future revenue streams and consolidated financial statements.

In June 2014, the FASB issued ASU No. 2014-12.  The amendments in this ASU apply to reporting entities that grant their employees share-based payments in which the terms of the award provide that a performance target can be achieved after a requisite service period.  The amendments require an entity to treat a performance target that affects vesting, and that could be achieved after the requisite service period, as a performance condition.  A reporting entity should apply existing guidance in ASC Topic 718 relating to awards with performance conditions that affect vesting to account for such awards.  The performance target should not be reflected in estimating the grant-date fair value of the award.  Compensation cost should be recognized in the period in which it becomes probable that the performance target will be achieved and should represent the compensation cost attributable to the period(s) for which the requisite service has already been rendered.  The amendments in this ASU are effective for annual reporting periods and interim periods within those annual reporting periods beginning after December 15, 2015, and early adoption is permitted.  The Company does not expect the adoption of this guidance to have a material impact on its consolidated financial statements.

In August 2014, the FASB issued ASU No. 2014-15, which is intended to define management’s responsibility to evaluate whether there is substantial doubt about an organization’s ability to continue as a going concern and to provide related footnote disclosures.  Substantial doubt about an entity’s ability to continue as a going concern exists when relevant conditions and events, considered in the aggregate, indicate that it is probable that the entity will be unable to meet its obligations as they become due within one year after the date that the financial statements are issued (or are available to be issued).  ASU No. 2014-15 provides guidance to an organization’s management, with principles and definitions intended to reduce diversity in the timing and content of disclosures commonly provided by organizations in the footnotes of their financial statements.  ASU No. 2014-15 is effective for annual reporting periods ending after December 15, 2016, and for annual and interim periods thereafter.  Early adoption is permitted.  The Company is currently in the process of evaluating the impact of adoption of this guidance on its consolidated financial statements and related disclosures.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2014
Summary of Significant Accounting Policies
Schedule of company's financial assets and liabilities that have been measured at fair value and indicating the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):
	The following table presents information about the Company’s financial assets and liabilities that have been measured at fair value at December 31, 2013 and 2014 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):
			December 31, 2013
	Description	Balance Sheet Classification	Total			Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	128,801		$	128,801	$	—	$	—
	Total assets		$	128,801		$	128,801	$	—	$	—
			December 31, 2014
	Description	Balance Sheet Classification	Total			Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	254,840		$	254,840	$	—	$	—
	Total assets		$	254,840		$	254,840	$	—	$	—
Schedule of estimated useful lives that were used to depreciate the Company's assets:
		Estimated Useful Life
	Furniture and fixtures	5 years
	Computer equipment and software	3 years
	Leasehold improvements	Shorter of the useful life or the remaining lease term
Schedule of share amount excluded from the calculation of diluted net loss per share, prior to the use of the treasury stock method, due to their anti-dilutive effect	The following table presents amounts that were excluded from the calculation of diluted net loss per share, due to their anti-dilutive effect (in thousands):
		Years Ended December 31,
		2012	2013		2014
	Outstanding stock awards	2,134	2,853		3,742
	Unvested restricted stock	349	102		4
		2,483	2,955		3,746

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property and Equipment
Schedule of property and equipment and related accumulated depreciation	The following table presents property and equipment, at cost, and related accumulated depreciation (in thousands):
		December 31,
		2013			2014
	Furniture and fixtures	$	244		$	821
	Computer equipment and software	404			672
	Leasehold improvements	67			115
		715			1,608
	Less accumulated depreciation and amortization	(275		)	(586		)
	Total property and equipment, net	$	440		$	1,022

Accrued_Expenses_Tables

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2014
Accrued Expenses
Schedule of accrued expenses	The following table presents the components of accrued expenses (in thousands):
		December 31,
		2013		2014
	Research and development	$	7,422	$	11,433
	Salaries, bonuses and other compensation	2,462		4,012
	Professional services	389		529
	Other accrued expenses	268		776
	Total accrued expenses	$	10,541	$	16,750

Convertible_Notes_Tables

Convertible Notes ( Tables )	12 Months Ended
	Dec. 31, 2014
Convertible Notes
Schedule of convertible note balances	The Company’s outstanding convertible note balances at December 31, 2014 consisted of the following (in thousands):
		December 31, 2014
	Liability component:
	Principal	$	201,250
	Less: debt discount, net	(85,769		)
	Net carrying amount	$	115,481
	Equity component	$	87,843
Schedule of convertible note interest expense	The following table sets forth total interest expense recognized related to the Convertible Notes during the year ended December 31, 2014 (in thousands):
		Year Ended
		December 31, 2014
	Contractual interest expense	$	1,526
	Amortization of debt discount	2,074
	Amortization of debt issuance costs	176
	Total interest expense	$	3,776

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2014
Stock-Based Compensation
Schedule of stock-based compensation expense as reflected in the Company's condensed consolidated statements of operations and comprehensive loss	The following table presents stock-based compensation expense as reflected in the Company’s consolidated statements of operations and comprehensive loss (in thousands):
			Years Ended December 31,
			2012			2013			2014
	Research and development		$	544		$	2,034		$	4,954
	General and administrative		1,259			5,725			6,729
	Total stock-based compensation expense		$	1,803		$	7,759		$	11,683
Summary of the Company's restricted stock activity and related information
	The following table presents a summary of the Company’s restricted stock activity and related information:
					Weighted-average
					grant date fair
			Shares		value per share
	Unvested restricted stock at December 31, 2013		102,412		$	0.76
	Granted		—		—
	Vested		(89,332	)	0.23
	Forfeited		(8,929	)	0.53
	Unvested restricted stock at December 31, 2014		4,151		$	12.79
Summary of the Company's stock option activity and related information
	The following table presents a summary of the Company’s stock option activity and related information:
			Shares		Weighted-average			Weighted-average		Aggregate
					exercise price per			remaining contractual		intrinsic value
					share			term (years)		(in thousands)
	Outstanding at December 31, 2013		2,852,793		$	12.77		8.4		$	46,708
	Granted		1,320,573		30.65
	Exercised		(157,113	)	10.59
	Cancelled		(289,924	)	17.75
	Outstanding at December 31, 2014		3,726,329		$	18.82		8.1		$	69,176
	Vested at December 31, 2014		1,552,249		$	10.16		7.2		$	42,428
	Vested and expected to vest at December 31, 2014 (a)		3,646,747		$	18.56		8		$	68,628
		(a)		This represents the number of vested options as of December 31, 2014, plus the number of unvested options expected to vest as of December 31, 2014, based on the unvested options at December 31, 2014, adjusted for the estimated forfeiture rate.
Schedule of fair value of each employee stock option estimated at the date of grant using a Black-Scholes option-pricing model
	The fair value of each stock option was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions:
			Years Ended December 31,
			2012		2013		2014
	Dividend yield		—		—		—
	Volatility		66% - 71%		73% - 78%		69% - 76%
	Risk-free interest rate		0.89% - 1.56%		1.07% - 2.05%		1.65% - 2.07%
	Expected term (years)		6.25		5.50 - 6.25		5.50 - 6.08
Summary of the Company's restricted stock unit (RSU) activity and related information
	The following table presents a summary of the Company’s restricted stock unit activity and related information:
					Weighted-average
					grant date fair
			Shares		value per share
	Unvested restricted stock units at December 31, 2013		—		$	—
	Granted		19,500		29.04
	Vested		(2,634	)	29.04
	Forfeited		—		—
	Withheld for taxes (a)		(1,266	)	29.04
	Unvested restricted stock units at December 31, 2014		15,600		$	29.04

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2014
Income Taxes
Schedule of reconciliation of income (loss) before the provision for (benefit from) income taxes	The following table presents a reconciliation of income (loss) before the provision for (benefit from) income taxes during the years ended December 31, 2012, 2013 and 2014 (in thousands):
		Years Ended December 31,
		2012			2013			2014
	United States	$	(61,763	)	$	(87,953	)	$	(141,119	)
	Foreign	—			(4,409		)	(29,893		)
	(Loss) income before provision for (benefit from) income taxes	$	(61,763	)	$	(92,362	)	$	(171,012	)
Schedule of reconciliation of income tax expense (benefit) at the statutory federal income tax rate to the effective income tax rate as reflected in the consolidated financial statements
	The following table presents a reconciliation of income tax expense (benefit) at the statutory federal income tax rate to the effective income tax rate as reflected in the consolidated financial statements:
		Years Ended December 31,
		2012		2013		2014
	Federal income tax (benefit)/expense at statutory rate	(34.0	)%	(34.0	)%	(34.0	)%
	State income tax benefit	(5.4	)	(5.1	)	(4.4	)
	Permanent items	0.4		0.8		0.7
	Foreign rate differential	0		1.6		5.9
	Federal research and development credit	0		(2.5	)	(1.4	)
	Change in valuation allowance	39		39.2		33.2
	Effective income tax rate	0	%	0	%	0	%
Schedule of principal components of the Company's deferred tax assets and liabilities	The following table presents the principal components of the Company’s deferred tax assets and liabilities (in thousands):
		December 31,
		2013			2014
	Deferred tax assets:
	Federal net operating loss carryforwards	$	50,265		$	86,163
	State net operating loss carryforwards	7,762			13,270
	Depreciation and amortization	5,793			14,647
	Tax credit carryforwards	2,984			5,780
	Stock-based compensation	2,248			4,891
	Other	779			1,289
	Total deferred tax assets	69,831			126,040
	Less: valuation allowance	(69,831		)	(101,399		)
	Net deferred tax assets	$	—		$	24,641
	Deferred tax liability:
	Debt discount on convertible notes		—			(24,641	)
	Net deferred taxes	$	—		$	—

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies
Schedule of future minimum rental commitments, by fiscal year and in the aggregate	The following table presents future minimum rental commitments, by fiscal year and in the aggregate, as of December 31, 2014 (in thousands):
		Operating
		Leases
	2015	$	1,697
	2016	1,697
	2017	849
	Thereafter	—
	Total minimum lease payments	$	4,243

Consolidated_Quarterly_Financi1

Consolidated Quarterly Financial Data - Unaudited (Tables)	12 Months Ended
	Dec. 31, 2014
Consolidated Quarterly Financial Data - Unaudited
Schedule of unaudited consolidated quarterly financial data	The following table presents unaudited consolidated quarterly financial data for the years ended December 31, 2013 and 2014 (in thousands, except per share data):
			Three Months Ended
			March 31,			June 30,			Sept. 30,			Dec. 31,			March 31,			June 30,			Sept. 30,			Dec. 31,
			2013			2013			2013			2013			2014			2014			2014			2014
	Expenses:
	Research and development		$	16,503		$	18,177		$	22,163		$	18,882		$	28,117		$	30,569		$	29,925		$	29,814
	General and administrative		2,400			3,412			4,503			4,465			4,688			5,587			6,263			7,397
	Acquired in-process research and development		—			—			1,940		(a)	—			17,000		(b)	900		(c)	—			7,000		(d)
	Total expenses		18,903			21,589			28,606			23,347			49,805			37,056			36,188			44,211
	Loss from operations		(18,903		)	(21,589		)	(28,606		)	(23,347		)	(49,805		)	(37,056		)	(36,188		)	(44,211		)
	Interest expense		—			—			—			—			—			—			(42		)	(3,734		)
	Interest income		34			25			17			7			5			5			4			10
	Net loss		$	(18,869	)	$	(21,564	)	$	(28,589	)	$	(23,340	)	$	(49,800	)	$	(37,051	)	$	(36,226	)	$	(47,935	)
	Net loss per share - basic and diluted		$	(0.66	)	$	(0.67	)	$	(0.88	)	$	(0.72	)	$	(1.43	)	$	(1.03	)	$	(1.01	)	$	(1.33	)
	Weighted-average shares - basic and diluted		28,798			32,336			32,453			32,597			34,856			35,982			36,029			36,071
		(a)		In the quarter ended September 30, 2013, the Company made a milestone payment to Merck for niraparib as a result of the first patient dosing in the NOVA trial, which occurred in July 2013.
		(b)		In the quarter ended March 31, 2014, the Company paid an up front fee of $17.0 million to AnaptysBio related to the immuno-oncology platform.
		(c)		In the quarter ended June 30, 2014, the Company made a milestone payment to Merck for niraparib as a result of the first patient dosing in the BRAVO trial, which occurred in April 2014.
		(d)		In the quarter ended December 31, 2014 the Company made a $5.0 million milestone payment to OPKO related to the acceptance of the oral rolapitant NDA for review by the FDA, as well as an up front payment of $2.0 million to AnaptysBio related to the immuno-oncology platform amendment.

Nature_of_Business_Details

Nature of Business (Details) (USD $)	0 Months Ended			1 Months Ended		12 Months Ended
	Jul. 23, 2012	Jun. 27, 2012	Jun. 12, 2012	Feb. 28, 2014	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jul. 03, 2012
						segment
Nature of Business
Number of operating segments						1
Reverse stock split, conversion ratio			3.5
Shares sold		6,000,000		3,200,000	5,428,000
Common stock issue price in an underwritten public offering (in dollars per share)		$13.50		$31.50	$18
Number of shares of common stock issued on conversion from convertible preferred stock									19,410,490
Number of additional shares under option granted to underwriters to purchase common stock shares at initial public offering price to cover over-allotments	430,183
Proceeds from sale of common stock, net of underwriting discount and commissions	$78,000,000
Common stock, shares authorized						100,000,000	100,000,000
Preferred stock, shares authorized						10,000,000	10,000,000
Common stock, par value (in dollars per share)						$0.00	$0.00
Preferred stock, par value (in dollars per share)						$0.00	$0.00
Net proceeds from the sale of common stock in an underwritten public offering				$94,200,000	$91,300,000	$94,199,000	$91,312,000	$77,960,000

Significant_Accounting_Policie

Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
	segment
Segment Information
Number of operating segments	1
Fair Value, Concentration of Risk, Financial Liabilities, Balance Sheet Groupings [Abstract]
Concentration Risk, Credit Risk, Financial Instruments, Off-balance Sheet Risk	0
Estimate of Fair Value Measurement
Fair Value of Financial Instruments
Total assets	254,840	$128,801
Estimate of Fair Value Measurement | Money Market Funds
Fair Value of Financial Instruments
Cash and cash equivalents	254,840	128,801
Fair Value, Inputs, Level 1
Fair Value of Financial Instruments
Total assets	254,840	128,801
Fair Value, Inputs, Level 1 | Money Market Funds
Fair Value of Financial Instruments
Cash and cash equivalents	254,840	$128,801

Significant_Accounting_Policie1

Significant Accounting Policies (Details 2) (USD $)	1 Months Ended
	Sep. 30, 2014	Dec. 31, 2014
Convertible notes [Line Items]
Interest rate (as a percent)	3.00%	3.00%
Convertible senior notes due October 2021
Convertible notes [Line Items]
Proceeds from issuance of convertible notes	$201,300,000
Interest rate (as a percent)	3.00%
Net carrying amount		115,481,000
Convertible notes fair value disclosures		$251,100,000

Significant_Accounting_Policie2

Significant Accounting Policies (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2014
Property and Equipment
Loss on disposal of property and equipment	($80,000)
Impairment losses	$0
Furniture and Fixtures
Property and Equipment
Estimated Useful Life	5 years
Computer Equipment and Software
Property and Equipment
Estimated Useful Life	3 years

Significant_Accounting_Policie3

Significant Accounting Policies (Details 4)	3 Months Ended	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Loss per Share
Amounts excluded from the calculation of diluted loss per share , prior to the use of the treasury stock method , due to their anti-dilutive effect		3,746,000	2,955,000	2,483,000
Shares issuable due to conversion of convertible debt	0
Employee Stock Option
Net Loss per Share
Amounts excluded from the calculation of diluted loss per share , prior to the use of the treasury stock method , due to their anti-dilutive effect		3,742,000	2,853,000	2,134,000
Restricted Stock
Net Loss per Share
Amounts excluded from the calculation of diluted loss per share , prior to the use of the treasury stock method , due to their anti-dilutive effect		4,000	102,000	349,000

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property and Equipment
Gross	$1,608	$715
Less accumulated depreciation and amortization	-586	-275
Total property and equipment, net	1,022	440
Total depreciation, expense	349	179	64
Furniture and Fixtures
Property and Equipment
Gross	821	244
Computer Equipment and Software
Property and Equipment
Gross	672	404
Leasehold Improvements
Property and Equipment
Gross	$115	$67

Accrued_Expenses_Details

Accrued Expenses (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Accrued Expenses
Research and development	$11,433	$7,422
Salaries, bonuses and other compensation	4,012	2,462
Professional services	529	389
Other accrued expenses	776	268
Total accrued expenses	$16,750	$10,541

Convertible_Notes_Details

Convertible Notes ( Details ) (USD $)	3 Months Ended		12 Months Ended	0 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2014	Sep. 29, 2014
Proceeds from issuance of convertible notes, net of issuance costs			$194,698,000
Interest rate (as a percent)	3.00%	3.00%	3.00%
Interest expense
Total interest expense	3,734,000	42,000	-3,776,000
Capped call option transactions
Capped calls transaction cost charged to stockholders' equity			-20,829,000
Convertible senior notes due October 2021
Notes, issued amount				201,300,000
Convertible notes issued from overallotment				26,300,000
Proceeds from issuance of convertible notes, net of issuance costs				194,700,000
Debt issuance costs paid			6,600,000	6,600,000
Capped call transactions payments				20,800,000
Interest rate (as a percent)		3.00%
Conversion price per share of convertible notes into common stock	$35.13		$35.13
Convertible notes conversion ratio per 1,000 principal			28.4627
Denominator of the principal amount used in conversion			1,000
Current share price premium over convertible note conversion share price ( as a percent )			35.00%
Sinking fund provided			0
Minimum percentage of debt holders that may force redemption of convertible notes			25.00%
Minimum percentage of convertible notes and accrued interest being redeemed upon notice or under certain circumstances			100.00%
Percentage of convertible notes being redeemed in the event of insolvency			100.00%
Grace period in days before acceleration or conversion of debt occurs			180
Convertible debt outstanding
Principal	201,250,000		201,250,000
Less: debt discount, net	-85,769,000		-85,769,000
Net carrying amount	115,481,000		115,481,000
Equity component	87,843,000		87,843,000
Convertible note issuance terms
Debt issuance costs paid			6,600,000	6,600,000
Equity component of debt issuance costs			2,900,000
Debt component of issuance costs recorded as an asset	3,700,000		3,700,000
Expected term for fair value			7 years
Convertible debt	115,500,000		115,500,000
Convertible notes fair value disclosures	251,100,000		251,100,000
Debt effective interest rate ( as a percent )	12.90%		12.90%
Interest expense
Contractual interest expense			1,526,000
Amortization of debt discount			2,074,000
Amortization of debt issuance costs			176,000
Total interest expense			3,776,000
Convertible senior notes due October 2021 | Capped call option
Capped call option transactions
Strike price ( in dollars per share )			$35.13
Cap price ( in dollars per share )			45.54
Capped calls cost charged to stockholders' equity			20,800,000
Convertible senior notes due October 2021 | Conversion of convertible notes into common stock after December 31,2014
Convertible threshold trading days			20
Convertible threshold consecutive trading days			30 days
Minimum threshold percentage of stock price trigger			130.00%
Convertible senior notes due October 2021 | Conversion of convertible notes when common share trading price is less than 98% of target ratio
Convertible threshold trading days			5
Convertible threshold consecutive trading days			10 days
Denominator of the principal amount for conversion into common stock			1,000
Threshold percentage forcing conversion when less than share price times conversion ratio			98.00%
Convertible senior notes due October 2021 | Conversion of convertible notes on or after April 1 , 2021
Days before maturity when notes holder can convert the notes			2 days
Minimum principal that holders may convert at or immediately before maturity			$1,000

Convertible_Preferred_Stock_an1

Convertible Preferred Stock and Stockholders' Equity (Details) (USD $)	0 Months Ended		1 Months Ended		12 Months Ended			0 Months Ended
	Jul. 23, 2012	Jun. 27, 2012	Feb. 28, 2014	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 21, 2012	Jul. 03, 2012
Convertible Preferred Stock and Stockholders' Equity
Preferred stock, shares authorized					10,000,000	10,000,000
Common stock, shares authorized					100,000,000	100,000,000
Preferred stock, par value (in dollars per share)					$0.00	$0.00
Common stock, par value (in dollars per share)					$0.00	$0.00
Preferred stock, shares issued					0	0
Preferred stock, shares outstanding					0	0
Common stock, shares issued					36,110,082	32,739,008
Common Stock, Shares, Outstanding					36,110,082	32,739,008
Number of shares of common stock issued on conversion from convertible preferred stock									19,410,490
Shares sold		6,000,000	3,200,000	5,428,000
Common stock issue price in an underwritten public offering (in dollars per share)		$13.50	$31.50	$18
Number of additional shares under option granted to underwriters to purchase common stock shares at initial public offering price to cover over-allotments	430,183
Proceeds from sale of common stock, net of underwriting discount and commissions	$78,000,000
Net proceeds from sale of shares							58,349,000
Net proceeds from the sale of common stock in an underwritten public offering			94,200,000	91,300,000	94,199,000	91,312,000	77,960,000
Preferred stock value								0
Convertible Preferred Stock
Convertible Preferred Stock and Stockholders' Equity
Convertible preferred stock, shares outstanding									67,936,761
Net proceeds from sale of shares								58,300,000
Series B Preferred Stock
Convertible Preferred Stock and Stockholders' Equity
Shares sold								26,884,442
Sale price per share (in dollars per share)								$2.17
Common Stock
Convertible Preferred Stock and Stockholders' Equity
Number of shares of common stock issued on conversion from convertible preferred stock									19,410,490
Shares sold	6,000,000		3,200,000	5,428,000
Common stock issue price in an underwritten public offering (in dollars per share)	$13.50		$31.50	$18
Number of additional shares under option granted to underwriters to purchase common stock shares at initial public offering price to cover over-allotments	430,183
Proceeds from sale of common stock, net of underwriting discount and commissions	78,000,000
Gross proceeds from the sale of common stock in an underwritten public offering			100,800,000	97,700,000
Net proceeds from the sale of common stock in an underwritten public offering			$94,200,000	$91,300,000
Number of votes per share					1

StockBased_Compensation_Detail

Stock-Based Compensation (Details ) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Stock-based compensation expense
Total stock-based compensation expense	$11,683,000	$7,759,000	$1,803,000
Research and Development Expense
Stock-based compensation expense
Total stock-based compensation expense	4,954,000	2,034,000	544,000
General and Administrative Expense
Stock-based compensation expense
Total stock-based compensation expense	$6,729,000	$5,725,000	$1,259,000

StockBased_Compensation_Detail1

Stock-Based Compensation (Details 2)	12 Months Ended	0 Months Ended
	Dec. 31, 2014	Feb. 07, 2011	10-May-10	Jan. 02, 2015	Jan. 02, 2014	Apr. 27, 2012	Jan. 02, 2012
		item
Stock-Based Compensation
Annual increase in common stock available for grant as a percentage of common stock outstanding	4.00%
Employee Stock Option
Stock-Based Compensation
Exercisable period from the date of grant	10 years
Employee Stock Option | Vesting One Year from Awards Vesting Start Date
Stock-Based Compensation
Vesting percentage	25.00%
Vesting period	1 year
Employee Stock Option | Vesting over Subsequent 36 Months
Stock-Based Compensation
Vesting percentage	75.00%
Vesting period	3 years
Employee Stock Option | Common Stock
Stock-Based Compensation
Number of shares available for future grants that were added to the total number of shares reserved for issuance				1,444,403	1,309,560
Restricted Stock
Stock-Based Compensation
Number of non-founding employees to whom shares of common stock are allotted as compensation for services provided		1
Restricted Stock | Common Stock | Founders
Stock-Based Compensation
Shares of common stock purchased	1,071
Shares of common stock granted			1,071,426
Restricted Stock | Series A1 Preferred Stock | Founders
Stock-Based Compensation
Conversion ratio for conversion of preferred stock into common stock (in shares)			1,000
Omnibus Incentive Plan 2012 | Common Stock
Stock-Based Compensation
Number of shares available for grant under the plan						1,428,571
Number of shares available for future grants that were added to the total number of shares reserved for issuance						6,857
Omnibus Incentive Plan 2012 | Common Stock Awards
Stock-Based Compensation
Number of shares available for grant under the plan	423,759
Stock Incentive Plan 2010 | Common Stock
Stock-Based Compensation
Number of shares available for grant under the plan							1,981,130
Number of shares available for future grants that were added to the total number of shares reserved for issuance						6,857

StockBased_Compensation_Detail2

Stock-Based Compensation (Details 3) (USD $)	12 Months Ended			1 Months Ended	0 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 31, 2014	Feb. 07, 2011	10-May-10	Jan. 02, 2015	Jan. 02, 2014	Apr. 27, 2012	Jan. 02, 2012
					item
Stock-Based Compensation
Annual increase in common stock available for grant as a percentage of common stock outstanding	4.00%
Stock-based compensation expense	$11,683,000	$7,759,000	$1,803,000
Employee Stock Option
Stock-Based Compensation
Exercisable period from the date of grant	10 years
Options granted (in shares)	1,320,573
Issuance of common stock resulting from exercise of common stock (in shares)	157,113
Options cancelled (in shares)	289,924
Stock-based compensation expense	11,081,000	6,770,000	1,526,000
Employee Stock Option | Vesting One Year from Awards Vesting Start Date
Stock-Based Compensation
Vesting percentage	25.00%
Vesting period	1 year
Employee Stock Option | Vesting over Subsequent 36 Months
Stock-Based Compensation
Vesting percentage	75.00%
Vesting period	3 years
Employee Stock Option | Non Employee Consultant
Stock-Based Compensation
Options granted (in shares)	2,750	0	0	2,750
Issuance of common stock resulting from exercise of common stock (in shares)	0
Stock-based compensation expense	297,000	1,132,000
Employee Stock Option | Common Stock
Stock-Based Compensation
Number of shares available for future grants that were added to the total number of shares reserved for issuance							1,444,403	1,309,560
Restricted Stock
Stock-Based Compensation
Granted (in shares)	0		0
Number of non-founding employees to whom shares of common stock are allotted as compensation for services provided					1
Stock-based compensation expense	116,000	669,000	24,000
Restricted Stock | Founders and One Employee
Stock-Based Compensation
Granted (in shares)					188,570
Restricted Stock | Non Employee Consultant
Stock-Based Compensation
Stock-based compensation expense	$96,000	$646,000
Restricted Stock | Common Stock | Founders
Stock-Based Compensation
Shares of common stock purchased	1,071
Shares of common stock granted						1,071,426
Restricted Stock | Series A1 Preferred Stock | Founders
Stock-Based Compensation
Conversion ratio for conversion of preferred stock into common stock (in shares)						1,000
Omnibus Incentive Plan 2012 | Common Stock
Stock-Based Compensation
Number of shares available for grant under the plan									1,428,571
Number of shares available for future grants that were added to the total number of shares reserved for issuance									6,857
Omnibus Incentive Plan 2012 | Common Stock Awards
Stock-Based Compensation
Number of shares available for grant under the plan	423,759
Stock Incentive Plan 2010 | Common Stock
Stock-Based Compensation
Number of shares available for grant under the plan										1,981,130
Number of shares available for future grants that were added to the total number of shares reserved for issuance									6,857

StockBased_Compensation_Detail3

Stock-Based Compensation (Details 4) (USD $)	1 Months Ended	12 Months Ended			1 Months Ended
	Aug. 31, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Jun. 30, 2014	Jun. 30, 2013	Oct. 31, 2012
Weighted-average price per share
Granted (in dollars per share)	$29.04
Additional disclosure
Stock-based compensation expense		$11,683,000	$7,759,000	$1,803,000
Aggregate value of shares issued to certain non-employee board members in lieu of fees		274,000	253,000	253,000
Restricted Stock
Shares
Unvested restricted at the beginning of the period (in shares)		102,412
Granted (in shares)		0		0
Vested (in shares)		-89,332
Forfeited (in shares)		-8,929
Unvested restricted at the end of the period (in shares)		4,151	102,412
Weighted-average grant date fair value per share
Unvested restricted at the beginning of the period (in dollars per share)		$0.76
Vested (in dollars per share)		$0.23
Forfeited (in dollars per share)		$0.53
Unvested restricted at the end of the period (in dollars per share)		$12.79	$0.76
Additional disclosure
Total grant date fair value of vested restricted stock		21,000	25,000	47,000
Additional disclosure
Stock-based compensation expense		116,000	669,000	24,000
Weighted-average grant date fair value of options granted (in dollars per share)			$46.22
Restricted Stock | Non Employee Consultant
Additional disclosure
Stock-based compensation expense		96,000	646,000
Employee Stock Option
Additional disclosure
Total unrecognized compensation cost related to unvested stock options (in dollars)		30,700,000
Weighted average period over which unrecognized compensation costs are expected to be recognized		2 years 6 months
Shares
Outstanding at the beginning of the period (in shares)		2,852,793
Granted (in shares)		1,320,573
Exercised (in shares)		-157,113
Cancelled (in shares)		-289,924
Outstanding at the end of the period (in shares)		3,726,329	2,852,793
Vested at the end of the period (in shares)		1,552,249
Vested and expected to vest at the end of the period (in shares)		3,646,747
Weighted-average price per share
Outstanding at the beginning of the period (in dollars per share)		$12.77
Granted (in dollars per share)		$30.65
Exercised (in dollars per share)		$10.59
Cancelled (in dollars per share)		$17.75
Outstanding at the end of the period (in dollars per share)		$18.82	$12.77
Vested at the end of the period (in dollars per share)		$10.16
Vested and expected to vest at the end of the period (in dollars per share)		$18.56
Weighted-average remaining contractual term (years)
Outstanding at the end of the period		8 years 1 month 6 days	8 years 4 months 24 days
Vested at the end of the period		7 years 2 months 12 days
Vested and expected to vest at the end of the period		8 years
Aggregate intrinsic value
Outstanding at the end of the period (in dollars)		69,176,000	46,708,000
Vested at the end of the period (in dollars)		42,428,000
Vested and expected to vest at the end of the period		68,628,000
Assumptions used to calculate fair value of employee stock option at the date of grant
Volatility, minimum (as a percent)		69.00%	73.00%	66.00%
Volatility, maximum (as a percent)		76.00%	78.00%	71.00%
Risk-free interest rate, minimum (as a percent)		1.65%	1.07%	0.89%
Risk-free interest rate, maximum (as a percent)		2.07%	2.05%	1.56%
Expected term				6 years 3 months
Additional disclosure
Stock-based compensation expense		11,081,000	6,770,000	1,526,000
Weighted-average grant date fair value of options granted (in dollars per share)		$20.33	$18.48	$5.29
Aggregate intrinsic value of options exercised		3,400,000	4,800,000	200,000
Weighted average period over which unrecognized compensation costs are expected to be recognized		2 years 6 months
Shares issued during the period					10,411	4,368	16,644
Aggregate value of shares issued to certain non-employee board members in lieu of fees					300,000	300,000	300,000
Employee Stock Option | Minimum
Assumptions used to calculate fair value of employee stock option at the date of grant
Expected term		5 years 6 months	5 years 6 months
Employee Stock Option | Maximum
Assumptions used to calculate fair value of employee stock option at the date of grant
Expected term		6 years 29 days	6 years 3 months
Employee Stock Option | Former Chief Financial Officer
Additional disclosure
Incremental stock-based compensation expense		400,000	1,800,000
Employee Stock Option | Non Employee Consultant
Shares
Granted (in shares)	2,750	2,750	0	0
Exercised (in shares)		0
Vested at the end of the period (in shares)		0
Assumptions used to calculate fair value of employee stock option at the date of grant
Volatility (as a percent)		69.00%
Risk-free interest rate (as a percent)		1.87%
Expected term		5 years 6 months
Dividend yield		0.00%
Additional disclosure
Stock-based compensation expense		$297,000	$1,132,000
Weighted-average grant date fair value of options granted (in dollars per share)		$17.50

StockBased_Compensation_Detail4

Stock-Based Compensation (Details 5) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Additional disclosure
Stock-based compensation expense	$11,683,000	$7,759,000	$1,803,000
Annual increase in common stock available for grant as a percentage of common stock outstanding	4.00%
Employee Stock Option
Additional disclosure
Expected term			6 years 3 months
Stock-based compensation expense	11,081,000	6,770,000	1,526,000
Options granted (in shares)	1,320,573
Minimum | Employee Stock Option
Additional disclosure
Expected term	5 years 6 months	5 years 6 months
Maximum | Employee Stock Option
Additional disclosure
Expected term	6 years 29 days	6 years 3 months
Employee Stock Purchase Plan
Additional disclosure
Number of shares available for grant under the plan	275,000
Shares issued	9,845	7,831
Stock-based compensation expense	99,000
Number of shares remaining available for issuance	257,324
Offering period	6 months
Purchase price of the common stock as a percentage of the lower of the fair market value of a share of common stock on the first trading date of each offering period or on the last trading day of the offering period	85.00%
Termination period	10 years
Employee Stock Purchase Plan | Maximum
Additional disclosure
Purchase of common stock based on fair market value	25,000
Restricted Stock Units
Shares
Granted (in shares)	19,500	0	0
Vested (in shares)	-2,634
Withheld for taxes (in shares)	-1,266
Unvested restricted at the end of the period (in shares)	15,600
Weighted-average grant date fair value per share
Granted (in dollars per share)	$29.04
Vested (in dollars per share)	$29.04
Withheld for taxes	$29.04
Unvested restricted at the end of the period (in dollars per share)	$29.04
Additional disclosure
Total grant date fair value of vested restricted stock	113,000	0	0
Unrecognized compensation costs	$453,000
Expected term	9 months

Income_Taxes_Details

Income Taxes (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
(Loss) before income taxes	($171,012)	($92,362)	($61,763)
United States
(Loss) before income taxes	-141,119	-87,953	-61,763
Foreign
(Loss) before income taxes	($29,893)	($4,409)

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Taxes
Gross unrecognized tax benefits related to research and development credits	$1,000,000	$500,000
Federal and state net operating losses related to excess tax deductions	5,800,000
Increase in valuation allowance, deferred tax asset	31,600,000
Deferred tax assets :
Federal net operating loss carryforwards	86,163,000	50,265,000
State net operating loss carryforwards	13,270,000	7,762,000
Depreciation and amortization	14,647,000	5,793,000
Tax credit carryforwards	5,780,000	2,984,000
Stock-based compensation	4,891,000	2,248,000
Other	1,289,000	779,000
Total deferred tax assets	126,040,000	69,831,000
Less valuation allowance	-101,399,000	-69,831,000
Net deferred tax assets	24,641,000
Debt discount on convertible notes	-24,641,000
Reconciliation of income tax expense (benefit) at the statutory federal income tax rate to the effective income tax rate as reflected in the consolidated financial statements
Federal income tax (benefit)/ expense at statutory rate (as a percent)	-34.00%	-34.00%	-34.00%
State income tax benefit (as a percent)	-4.40%	-5.10%	-5.40%
Permanent items (as a percent)	0.70%	0.80%	0.40%
Foreign rate differential	5.90%	1.60%	0.00%
Federal research and development credit (as a percent)	1.40%	2.50%	0.00%
Change in valuation allowance (as a percent)	33.20%	39.20%	39.00%
Effective income tax rate (as a percent)	0.00%	0.00%	0.00%
R & D Tax Credit Carryforward | Internal Revenue Service (IRS)
Income Taxes
Tax credit carryforwards	5,900,000
R & D Tax Credit Carryforward | State
Income Taxes
Tax credit carryforwards	$1,400,000

Income_Taxes_Details_3

Income Taxes (Details 3) (USD $)	Dec. 31, 2014
In Millions, unless otherwise specified
State
Operating loss carryforwards
Net operating loss carryforwards	$257.60
Internal Revenue Service (IRS)
Operating loss carryforwards
Net operating loss carryforwards	$259.20

Employee_Benefit_Plan_Details

Employee Benefit Plan (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Employee Benefit Plan
Employer match of employee deferral contributions of first 3% of compensation (as a percent)	3.00%
Percentage of eligible compensation, matched 100% by employer	100.00%
Employer match of employee deferral contributions of next 2% of compensation (as a percent)	2.00%
Percentage of eligible compensation, matched 50% by employer	50.00%
Aggregate matching contribution to the 401(k) plan	$484,000	$277,000	$137,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Future minimum rental commitments
2015	$1,697,000
2016	1,697,000
2017	849,000
Total minimum lease payments	4,243,000
Rent expense	$1,525,000	$647,000	$166,000
Operating Lease
Commitments and Contingencies
Leased office space (in square feet)	53,200
Future minimum rental commitments
Period of free rent	1 month

License_Agreements_Details

License Agreements (Details) (USD $)	0 Months Ended	1 Months Ended		3 Months Ended								12 Months Ended			1 Months Ended				12 Months Ended	1 Months Ended
	Jun. 27, 2012	Feb. 28, 2014	Mar. 31, 2013	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014	Dec. 31, 2010	Nov. 30, 2012	Mar. 31, 2011	Dec. 31, 2011	Apr. 30, 2014	Jul. 31, 2013	Jun. 30, 2012	Oct. 31, 2012
															item					item			item
License Agreements
Shares sold	6,000,000	3,200,000	5,428,000
Acquired in-process research and development expense				$7,000,000		$900,000	$17,000,000		$1,940,000			$24,900,000	$1,940,000	$8,000,000
Additional milestone payment												1
Up-front payment recorded as acquired in-process research and development expense												24,900,000	1,940,000	8,000,000
Research and development expense				29,814,000	29,925,000	30,569,000	28,117,000	18,882,000	22,163,000	18,177,000	16,503,000	118,425,000	75,725,000	47,200,000
Anaptys Bio Inc
License Agreements
Up-front fees paid				2,000,000			17,000,000
OPKO Health Inc
License Agreements
Milestone payments made				5,000,000								5,000,000
Collaboration and Exclusive License Agreement | Anaptys Bio Inc
License Agreements
Acquired in-process research and development expense												19,000,000
Up-front fees paid												2,000,000
Milestone payments required, if certain research and development milestone events are achieved							18,000,000								18,000,000
Number of development programs												4			4
Period for reimbursement of specified cost under agreement															2 years
Termination period															90 days
Additional milestone payments required, if certain U.S. and non-U.S. regulatory submissions and approvals occur in multiple indications							90,000,000								90,000,000
Up-front payment recorded as acquired in-process research and development expense															17,000,000
Research and development expense												4,600,000
License Agreement | OPKO Health Inc
License Agreements
Amount paid upon signing the agreement																6,000,000
Acquired in-process research and development expense																6,600,000
Amount paid upon signing the agreement																6,000,000
License Agreement | OPKO Health Inc | Maximum
License Agreements
Amount required to be paid for development milestones if specified regulatory and initial commercial sales milestones are achieved				30,000,000								30,000,000
Additional milestone payments required if specified levels of annual net sales of rolapitant are achieved				85,000,000								85,000,000
License Agreement | OPKO Health Inc | Junior Preferred Stock
License Agreements
Shares sold																1,500,000
Fair value of shares issued																630,000
License Agreement | Amgen Inc
License Agreements
Acquired in-process research and development expense																		500,000
Up-front fees paid																			500,000
Additional milestone payment																	1,000,000
License Agreement | Amgen Inc | Maximum
License Agreements
Milestone payments required, if specified clinical development, regulatory, initial commercialization and annual net product sales milestones are achieved				138,000,000								138,000,000
License Agreement | Merck
License Agreements
Acquired in-process research and development expense																						7,000,000
Up-front fees payable																						7,000,000
Number of milestone payments made				2								2								1
Milestone payments made																				900,000	1,900,000
License Agreement | Merck | Maximum
License Agreements
Amount required to be paid for development and regulatory milestones for the first indication				57,000,000								57,000,000
Amount required to be paid for development and regulatory milestones for each successive indication				29,500,000								29,500,000
Amount required to be paid for one-time sales milestones based on the achievement of annual sales objectives				87,500,000								87,500,000
License Agreement | AstraZeneca UK Limited
License Agreements
Up-front fees paid																							400,000
Milestone payments made													$200,000
Number of non-exclusive license agreements entered into by the entity																							2

Consolidated_Quarterly_Financi2

Consolidated Quarterly Financial Data - Unaudited (Details) (USD $)	3 Months Ended								12 Months Ended
Share data in Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Research and development	$29,814,000	$29,925,000	$30,569,000	$28,117,000	$18,882,000	$22,163,000	$18,177,000	$16,503,000	$118,425,000	$75,725,000	$47,200,000
General and administrative	7,397,000	6,263,000	5,587,000	4,688,000	4,465,000	4,503,000	3,412,000	2,400,000	23,935,000	14,780,000	6,715,000
Acquired in-process research and development expense	7,000,000		900,000	17,000,000		1,940,000			24,900,000	1,940,000	8,000,000
Total expenses	44,211,000	36,188,000	37,056,000	49,805,000	23,347,000	28,606,000	21,589,000	18,903,000	167,260,000	92,445,000	61,915,000
Loss from operations	-44,211,000	-36,188,000	-37,056,000	-49,805,000	-23,347,000	-28,606,000	-21,589,000	-18,903,000	-167,260,000	-92,445,000	-61,915,000
Interest expense	3,734,000	42,000							-3,776,000
Interest income	10,000	4,000	5,000	5,000	7,000	17,000	25,000	34,000	24,000	83,000	152,000
Net loss	-47,935,000	-36,226,000	-37,051,000	-49,800,000	-23,340,000	-28,589,000	-21,564,000	-18,869,000	-171,012,000	-92,362,000	-61,763,000
Net loss per share - basic and diluted (in dollars per share)	($1.33)	($1.01)	($1.03)	($1.43)	($0.72)	($0.88)	($0.67)	$0.66	($4.79)	($2.93)	($4.51)
Weighted - average shares - basic and diluted	36,071	36,029	35,982	34,856	32,597	32,453	32,336	28,798	35,739	31,559	13,696
Anaptys Bio Inc
Up front fees paid	2,000,000			17,000,000
OPKO Health Inc
Milestone payments	$5,000,000								$5,000,000