Tesaro (TSRO) 10-K 14 Mar 14 2013 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2013	Mar. 11, 2014	Jun. 30, 2013
Document and Entity Information	'	'	'
Entity Registrant Name	'TESARO, Inc.	'	'
Entity Central Index Key	'0001491576	'	'
Document Type	'10-K	'	'
Document Period End Date	31-Dec-13	'	'
Amendment Flag	'false	'	'
Current Fiscal Year End Date	'--12-31	'	'
Entity Well-known Seasoned Issuer	'No	'	'
Entity Voluntary Filers	'No	'	'
Entity Current Reporting Status	'Yes	'	'
Entity Filer Category	'Accelerated Filer	'	'
Entity Public Float	'	'	$524,741,000
Entity Common Stock, Shares Outstanding	'	35,968,936	'
Document Fiscal Year Focus	'2013	'	'
Document Fiscal Period Focus	'FY	'	'

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$130,310	$125,445
Other current assets	4,029	1,175
Total current assets	134,339	126,620
Property and equipment, net	440	219
Other assets	799	541
Total assets	135,578	127,380
Current liabilities:	'	'
Accounts payable	1,869	3,170
Accrued expenses	10,541	8,545
Other current liabilities	13	3
Total current liabilities	12,423	11,718
Other non-current liabilities	3	'
Commitments and contingencies (Notes 9 and 10)	'	'
Stockholders' equity:	'	'
Preferred stock, $0.0001 par value; 10,000,000 shares authorized at both December 31, 2012 and December 31, 2013; no shares issued or outstanding at both December 31, 2012 and December 31, 2013	'	'
Common stock, $0.0001 par value; 100,000,000 shares authorized at both December 31, 2012 and December 31, 2013; 27,136,329 and 32,739,008 shares issued and outstanding at December 31, 2012 and December 31, 2013, respectively	3	3
Additional paid-in capital	302,647	202,795
Deficit accumulated during the development stage	-179,498	-87,136
Total stockholders' equity	123,152	115,662
Total liabilities and stockholders' equity	$135,578	$127,380

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Feb. 28, 2014	Dec. 31, 2013	Dec. 31, 2012
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	$0.00
Common stock, shares authorized	'	100,000,000	100,000,000
Common stock, shares issued	'	32,739,008	27,136,329
Common stock, shares outstanding	'	32,739,008	27,136,329

Consolidated_Statements_of_Ope

Consolidated Statements of Operations and Comprehensive Loss (USD $)	12 Months Ended			45 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Expenses:	'	'	'	'
Research and development	$75,725	$47,200	$11,768	$134,739
General and administrative	14,780	6,715	3,158	26,321
Acquired in-process research and development	1,940	8,000	500	17,070
Total expenses	92,445	61,915	15,426	178,130
Loss from operations	-92,445	-61,915	-15,426	-178,130
Interest income	83	152	38	293
Other income (expense), net	'	'	-1,010	-1,661
Net loss	-92,362	-61,763	-16,398	-179,498
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	($2.93)	($4.51)	($31.90)	($14.70)
Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted (in shares)	31,559	13,696	514	12,211
Comprehensive loss	($92,362)	($61,763)	($16,398)	($179,498)

Consolidated_Statements_of_Con

Consolidated Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity (USD $)	Total	Convertible Preferred Stock	Convertible Preferred Stock	Convertible Preferred Stock	Convertible Preferred Stock	Convertible Preferred Stock	Common Stock	Additional Paid-in Capital	Deficit Accumulated During the Development Stage
In Thousands, except Share data, unless otherwise specified			Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series B Convertible Preferred Stock	Series O Convertible Preferred Stock
Balance at Mar. 26, 2010	'	'	'	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'	'
Issuance of stock, net of offering costs and investor rights obligation	'	'	$7,758	'	'	$630	'	'	'
Issuance of stock, net of offering costs and investor rights obligation (in shares)	'	'	10,000,000	'	'	1,500,000	1,071,426	'	'
Net loss	-8,975	'	'	'	'	'	'	'	-8,975
Balance at Dec. 31, 2010	-8,975	8,388	'	'	'	'	'	'	-8,975
Balance (in shares) at Dec. 31, 2010	'	11,500,000	'	'	'	'	'	'	'
Balance (in shares) at Dec. 31, 2010	'	'	'	'	'	'	1,071,426	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'	'
Issuance of stock, net of offering costs and investor rights obligation	'	'	'	13,812	42,148	'	'	'	'
Issuance of stock, net of offering costs and investor rights obligation (in shares)	'	'	'	10,000,000	19,552,319	'	'	'	'
Issuance of restricted common stock (in shares)	'	'	'	'	'	'	188,570	'	'
Stock-based compensation expense	305	'	'	'	'	'	'	305	'
Net loss	-16,398	'	'	'	'	'	'	'	-16,398
Balance at Dec. 31, 2011	-25,068	64,348	'	'	'	'	'	305	-25,373
Balance (in shares) at Dec. 31, 2011	'	'	'	'	'	'	1,259,996	'	'
Balance (in shares) at Dec. 31, 2011	'	41,052,319	'	'	'	'	'	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'	'
Issuance of stock, net of offering costs and investor rights obligation	77,960	'	'	'	58,349	'	1	77,959	'
Issuance of stock, net of offering costs and investor rights obligation (in shares)	'	'	'	'	26,884,442	'	6,430,183	'	'
Conversion of convertible preferred stock into common stock	122,697	-122,697	'	'	'	'	2	122,695	'
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	33	'	'	'	'	'	'	33	'
Issuance of common stock resulting from exercise of stock options (in shares)	'	'	'	'	'	'	19,016	'	'
Issuance of common stock as payment of Board of Directors fees in lieu of cash	253	'	'	'	'	'	'	253	'
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	'	'	'	'	'	'	1,550	'
Net loss	-61,763	'	'	'	'	'	'	'	-61,763
Balance at Dec. 31, 2012	115,662	'	'	'	'	'	3	202,795	-87,136
Balance (in shares) at Dec. 31, 2012	0	'	'	'	'	'	'	'	'
Balance (in shares) at Dec. 31, 2012	27,136,329	'	'	'	'	'	27,136,329	'	'
Increase (Decrease) in Stockholders' Equity	'	'	'	'	'	'	'	'	'
Issuance of stock, net of offering costs and investor rights obligation	91,312	'	'	'	'	'	'	91,312	'
Issuance of stock, net of offering costs and investor rights obligation (in shares)	'	'	'	'	'	'	5,428,000	'	'
Issuance of common stock resulting from exercise of stock options	634	'	'	'	'	'	'	634	'
Issuance of common stock resulting from exercise of stock options (in shares)	'	'	'	'	'	'	162,480	'	'
Issuance of common stock resulting from Employee Stock Purchase Plan	147	'	'	'	'	'	'	147	'
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	'	'	'	'	'	'	253	'
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	'	'	'	'	'	'	7,506	'
Net loss	-92,362	'	'	'	'	'	'	'	-92,362
Balance at Dec. 31, 2013	$123,152	'	'	'	'	'	$3	$302,647	($179,498)
Balance (in shares) at Dec. 31, 2013	0	'	'	'	'	'	'	'	'
Balance (in shares) at Dec. 31, 2013	32,739,008	'	'	'	'	'	32,739,008	'	'

Consolidated_Statements_of_Con1

Consolidated Statements of Convertible Preferred Stock and Stockholders' (Deficit) Equity (Parenthetical) (USD $)	9 Months Ended	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2010	Dec. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013	Dec. 31, 2012
	Convertible Preferred Stock	Convertible Preferred Stock	Convertible Preferred Stock	Convertible Preferred Stock	Common Stock	Common Stock
	Series A-1 Convertible Preferred Stock	Series A-2 Convertible Preferred Stock	Series B Convertible Preferred Stock	Series B Convertible Preferred Stock
Issuance of stock, price per share (in dollars per share)	$1	$1	$2.17	$2.17	'	'
Issuance of stock, offering costs	$74	$17	$110	$378	$6,392	$8,847

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended			45 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Operating activities	'	'	'	'
Net loss	($92,362)	($61,763)	($16,398)	($179,498)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'	'	'
Acquired in-process research and development	1,940	8,000	500	17,070
Depreciation expense	179	64	35	285
Increase in fair value of investor rights obligation	'	'	1,010	1,661
Stock-based compensation expense	7,759	1,803	305	9,867
Changes in operating assets and liabilities:	'	'	'	'
Other assets	-3,112	1,020	-2,709	-4,828
Accounts payable	-1,301	2,565	496	1,869
Accrued expenses	1,996	5,565	2,612	10,541
Other liabilities	13	-11	8	16
Net cash used in operating activities	-84,888	-42,757	-14,141	-143,017
Investing activities	'	'	'	'
Acquisition of product candidate licenses and milestone payments	-1,940	-8,000	-500	-16,440
Change in restricted cash	'	200	-100	'
Purchase of property and equipment	-400	-165	-98	-725
Net cash used in investing activities	-2,340	-7,965	-698	-17,165
Financing activities	'	'	'	'
Proceeds from sale of common stock, net of issuance costs	91,312	77,960	'	169,272
Proceeds from exercise of stock options	634	33	'	667
Proceeds from issuance of common stock under Employee Stock Purchase Plan	147	'	'	147
Proceeds from sale of convertible preferred and common stock and related investor rights, net of issuance costs	'	58,349	52,131	120,406
Net cash provided by financing activities	92,093	136,342	52,131	290,492
Increase in cash and cash equivalents	4,865	85,620	37,292	130,310
Cash and cash equivalents at beginning of period	125,445	39,825	2,533	'
Cash and cash equivalents at end of period	130,310	125,445	39,825	130,310
Non-cash investing and financing activities	'	'	'	'
Issuance of Series O convertible preferred stock	'	'	'	630
Settlement of investor rights obligation	'	'	3,829	3,829
Conversion of convertible preferred stock to common stock	'	$122,697	'	$122,697

Nature_of_Business

Nature of Business	12 Months Ended
	Dec. 31, 2013
Nature of Business	'
Nature of Business	'
	1. Nature of Business
	The Company
	TESARO, Inc. (the “Company” or “TESARO”) is a development stage company that was incorporated in Delaware on March 26, 2010 and commenced operations in May 2010.  TESARO is 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 globally.  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.  The Company currently operates in one segment.  The Company has never earned revenue from these activities and, accordingly, the Company is considered to be in the development stage as of December 31, 2013.  The Company is subject to a number of risks similar to those of other development stage companies, 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 of its product candidates and further its in-licensing and acquisition activities.
	The Company currently has one business activity, which is the identification, acquisition, development and commercialization of oncology therapeutics and supportive care product candidates, and has a single reporting and operating unit structure.
	Public Offerings of Common Stock
	On June 28, 2012, the Company completed 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 29, 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 $94.1 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 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 achieving a level of revenues adequate to support the Company’s 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.  In February 2014, the Company sold 3,200,000 shares of common stock, $0.0001 par value per share, 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 $94.1 million. The shares were issued pursuant to an automatic registration statement on Form S-3.  The Company expects that its existing cash and cash equivalents as of December 31, 2013, plus the net proceeds of its February 2014 offering, will be sufficient to fund its current operating plan through at least January 1, 2015.
	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, 2013
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 and the related disclosures.  On an ongoing basis, management evaluates its estimates, including estimates related to accrued clinical trial expenses and stock-based compensation expense.  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 inputs	Quoted prices in active markets for identical assets or liabilities
	Level 2 inputs	Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly
	Level 3 inputs	Unobservable 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, 2012 and 2013 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):
			December 31, 2012
	Description	Balance Sheet Classification	Total			Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	123,888		$	123,888	$	—	$	—
	Total assets		$	123,888		$	123,888	$	—	$	—
			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	$	—	$	—
	The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term maturities.
	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.  No impairment losses have been recorded through December 31, 2013.
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and include, but are not limited to:
	·                  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;
	·                  expenses incurred under agreements with contract research organizations, investigative sites and research consortia in connection with the conduct of clinical trials and preclinical studies and related services, such as administrative, data management and biostatistics services;
	·                  the cost of acquiring, developing and manufacturing active pharmaceutical ingredients, clinical trial materials and other research and development materials;
	·                  facilities, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and other supplies; and
	·                  costs associated with preclinical activities and regulatory operations.
	Costs for certain development activities, such as clinical trials, 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.  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.  The up-front payments to acquire 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 does not also include processes or activities that would constitute a “business”, 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 all stock-based awards based on estimated fair values.  The Company determines the fair values of equity-based awards at the 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 convertible preferred stock (for the periods in which it was outstanding), outstanding stock options and unvested restricted stock, 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, prior to the use of the treasury stock method, due to their anti-dilutive effect (in thousands):
							The Period from
							March 26, 2010
		Years Ended December 31,					(Inception) to
		2011	2012		2013		December 31, 2013
	Convertible preferred stock	11,729	—		—		—
	Outstanding stock options	894	2,134		2,853		2,853
	Unvested restricted stock	641	349		102		102
	13,264	2,483		2,955		2,955
Recently Issued Accounting Pronouncements
In July 2013, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update No. 2013-11, which requires entities to present an unrecognized tax benefit, or a portion of an unrecognized tax benefit, as a reduction to a deferred tax asset for a net operating loss carryforward or a similar tax loss or a tax credit carryforward, unless certain conditions exist.  This guidance is effective prospectively for fiscal years beginning after December 15, 2013.  Early adoption and retrospective application are permitted.  The Company expects to adopt this guidance effective January 1, 2014 and does not expect this adoption to have a material effect on its consolidated financial statements.

Property_and_Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2013
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,
		2012			2013
	Furniture and fixtures	$	31		$	244
	Computer equipment and software	266			404
	Leasehold improvements	18			67
		315			715
	Less accumulated depreciation and amortization	(96		)	(275		)
	Total property and equipment, net	$	219		$	440
	Total depreciation expense amounted to $35,000, $64,000 and $179,000 for the years ended December 31, 2011, 2012 and 2013, respectively.

Accrued_Expenses

Accrued Expenses	12 Months Ended
	Dec. 31, 2013
Accrued Expenses	'
Accrued Expenses	'
	4. Accrued Expenses
	The following table presents the components of accrued expenses (in thousands):
		December 31,
		2012		2013
	Research and development	$	6,635	$	7,422
	Salaries, bonuses and other compensation	1,316		2,462
	Professional services	282		389
	Other accrued expenses	312		268
	Total accrued expenses	$	8,545	$	10,541

Convertible_Preferred_Stock_an

Convertible Preferred Stock and Stockholders' Equity	12 Months Ended
	Dec. 31, 2013
Convertible Preferred Stock and Stockholders' Equity	'
Convertible Preferred Stock and Stockholders' Equity	'
	5. Convertible Preferred Stock and Stockholders’ Equity
	As of December 31, 2013, 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 32,739,008 shares of common stock were issued and outstanding.
	Convertible Preferred Stock
	The Company issued the Series O Junior convertible preferred stock, or Junior Preferred Stock, on December 10, 2010 in connection with the in-licensing of rolapitant (see Note 10, License Agreements).
	In June 2011, the Company entered into the Series B Preferred Stock Purchase Agreement with various investors, as amended in July 2011 and March 2012, or the Series B Purchase Agreement.  The Series B Purchase Agreement provided for the issuance of up to $101 million of Series B convertible preferred stock, subject to various terms and conditions.  On June 6, 2011 and July 7, 2011, the Company sold 18,390,796 shares and 1,161,523 shares, respectively, of Series B convertible preferred stock pursuant to the Series B Purchase Agreement at a price of $2.175 per share, resulting in aggregate net proceeds to the Company of $42.1 million.  Subject to the terms of the Series B Purchase Agreement, the Company was required to sell, and certain existing investors were required to purchase, up to an additional $58.5 million of Series B convertible preferred stock upon the occurrence of, or in connection with, certain milestone events.  Pursuant to the March 2012 amendment to the Series B Purchase Agreement, the Company and the existing investors agreed to accelerate the purchase and sale of the remaining shares of Series B convertible preferred stock available for issuance under the Series B Purchase Agreement, notwithstanding the original milestones.  On March 21, 2012, the Company sold an additional 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, 2013, 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 28, 2012, the Company completed 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 29, 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, $0.0001 par value per share, 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, $0.0001 par value per share, 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 $94.1 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, 2013
Stock-Based Compensation	'
Stock-Based Compensation	'
	6. Stock-Based Compensation
	The following table presents stock-based compensation expense as reflected in the Company’s condensed consolidated statements of operations and comprehensive loss (in thousands):
											The Period from
											March 26, 2010
		Years Ended December 31,									(Inception) to
		2011			2012			2013			December 31, 2013
	Research and development	$	46		$	544		$	2,034		$	2,624
	General and administrative	259			1,259			5,725			7,243
	Total stock-based compensation expense	$	305		$	1,803		$	7,759		$	9,867
	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 vest twenty-five percent (25%) one year from the vesting start date and seventy-five percent (75%) in equal installments over the subsequent thirty-six (36) months (subject to acceleration of vesting in the event of certain change of control transactions) 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 which 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.  Effective January 1, 2014, the number of shares authorized for issuance under the 2012 Incentive Plan was increased by 1,309,560 shares.  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 each option has been equal to the closing price of a share of our common stock on the grant date or the fair value as determined by the board of directors on the grant date.  As of December 31, 2013, a total of 1,291,604 stock options and 21,012 common stock awards have been granted, 12,468 options have been exercised, and 25,756 options have been cancelled under the 2012 Incentive Plan.
	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 357 shares of common stock to eligible employees, officers, directors and consultants.  On May 10, 2010, in connection with the Company’s sale of Series A-1 convertible preferred stock, each such share was reclassified for 1,000 shares of common stock, or an aggregate of 357,142 shares available under the 2010 Incentive Plan.  On June 6, 2011, in connection with the Company’s sale of Series B convertible preferred stock, the 2010 Incentive Plan was amended to increase the aggregate number of shares of common stock available to be issued under the 2010 Incentive Plan to 1,981,130 shares of common stock.  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, 2013, a total of 1,785,703 stock options and 188,570 restricted stock awards have been granted, 169,028 options have been exercised, and 17,262 options have been cancelled 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.  Under these agreements, the Founder Common shares vest as follows: twenty-five percent (25%) of such stock vested effective as of March 26, 2010, and seventy-five percent (75%) of such stock vests in equal installments over the subsequent forty-eight (48) months (subject to acceleration of vesting in the event of certain terminations of employment and in connection with certain change of control transactions).
	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.  Under these agreements, the 2011 Awards vest as follows: twenty-five percent (25%) of such stock vests effective as of January 6, 2012, and seventy-five percent (75%) of such stock vests in equal installments over the subsequent thirty-six (36) months (subject to acceleration of vesting in the event of certain change of control transactions).
	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, $24,000 and $669,000, respectively, for the years ended December 31, 2011, 2012 and 2013 associated with restricted common stock grants.  The total for the year ended December 31, 2013 includes $646,000 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, 2012	349,334		$	0.15
	Granted	1,114		46.22
	Vested	(248,036	)	0.1
	Forfeited	—		—
	Unvested restricted stock at December 31, 2013	102,412		$	0.76
	The weighted-average grant date fair values of restricted stock granted during the years ended December 31, 2011 and 2013 were $0.53 and $46.22 per share, respectively.  There were no grants of restricted stock during the year ended December 31, 2012.  The total grant date fair value of restricted stock that vested during the years ended December 31, 2011, 2012 and 2013 was $0, $47,000, and $25,000, respectively.  At December 31, 2013, there was $95,000 of total unrecognized compensation cost related to unvested restricted stock, which the Company expects to recognize over a remaining weighted-average period of 0.4 years.
	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		intrinsic value
				share			contractual term		(in thousands)
							(years)
	Outstanding at December 31, 2012	2,134,185		$	5.52
	Granted	916,250		28.13
	Exercised	(162,480	)	3.9
	Cancelled	(35,162	)	13.85
	Outstanding at December 31, 2013	2,852,793		$	12.77		8.4		$	46,708
	Vested at December 31, 2013	863,713		$	4.73		7.9		$	20,305
	Vested and expected to vest at December 31, 2013 (a)	2,852,793		$	12.77		8.4		$	46,708
	(a)         This represents the number of vested options as of December 31, 2013, plus the number of unvested options expected to vest as of December 31, 2013, based on the unvested options at December 31, 2013, adjusted for the estimated forfeiture rate of 0%.
	The fair value of each employee stock option was estimated at the date of grant using a Black-Scholes option-pricing model with the following assumptions:
		Years Ended December 31,
		2011		2012		2013
	Dividend yield	—		—		—
	Volatility	67% - 68%		66% - 71%		73% - 78%
	Risk-free interest rate	1.07% - 2.03%		0.89% - 1.56%		1.07% - 2.05%
	Expected term (years)	6.25		6.25		5.50 - 6.25
	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 to employees.  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 employee 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 coupled with comparison to data from the representative group of company peers and recognizes compensation costs only for those equity awards expected to vest.
	The Company recorded stock-based compensation expense associated with employee stock options of $281,000, $1,526,000, and $6,770,000 for the years ended December 31, 2011, 2012 and 2013, respectively.  The total for the year ended December 31, 2013 includes $1,132,000 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, 2011, 2012 and 2013 were $2.63, $5.29 and $18.48 per share, respectively.  The aggregate intrinsic value of options exercised during the years ended December 31, 2011, 2012 and 2013 was $0, $0.2 million, and $4.8 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, 2013, there was $17.0 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 and June 2013, and as provided for under the 2012 Incentive Plan, the Company issued 16,644 and 4,368 shares of common stock, respectively, with aggregate values of $0.3 million for both 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 the three months ended September 30, 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.  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 will continue to vest through March 31, 2014 (the term of the Consulting Agreement).  As a result, beginning in September 2013, the Company accounts for unvested stock awards previously granted to the former CFO as non-employee awards.  The Company records 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 are remeasured at each financial reporting date until they vest, with any increases or decreases in fair value recorded as stock-based compensation expense.  Fair values of stock options are determined on each measurement date using the Black-Scholes option pricing model, and fair values of restricted stock awards are equal to the fair market value of the Company’s common stock on the measurement date.  During the year ended December 31, 2013, the Company recorded incremental stock-based compensation expense of $1.8 million associated with these awards, as the result of the change in status of the former CFO.
	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, 2013, 267,169 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 date 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 year ended December 31, 2013, the Company issued a total of 7,831 shares of common stock under the 2012 ESPP and recognized $67,000 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, 2013
Income Taxes	'
Income Taxes	'
	7. Income Taxes
	The Company accounts for income taxes in accordance with ASC 740, Income Taxes, or ASC 740.  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.
	For the years ended December 31, 2011, 2012 and 2013, the Company did not record any current or deferred income tax provisions or benefits.
	As of December 31, 2013, the Company had federal net operating loss carryforwards of approximately $152.2 million and state net operating loss carryforwards of $151.3 million, which are available to reduce future taxable income.  The Company also had federal research and development tax credit carryforwards of $3.1 million, which may be used to offset future tax liabilities.  The net operating loss, or NOL, and tax credit carryforwards will expire at various dates through 2033.  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.
	The Company’s reserves related to taxes are based on a determination of whether and how much of a tax benefit taken by the Company in its tax filings or positions is more likely than not to be realized following resolution of any potential contingencies present related to the tax benefit.  As of December 31, 2013, the Company has recorded $0.5 million of gross unrecognized tax benefits related to research and development credits which, if recognized, would be offset by an adjustment to the valuation allowance.  Thus, there would be no impact to the consolidated balance sheet or consolidated statement of operations if the benefit was recognized.
	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.  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.
	On January 2, 2013, the President signed into law The American Taxpayer Relief Act of 2012, or ATRA.  Under prior law, a taxpayer was entitled to a research tax credit for qualifying amounts paid or incurred on or before December 31, 2011.  ATRA extended the research credit for two years to December 31, 2013.  The extension of the research credit was retroactive and included amounts paid or incurred after December 31, 2011.  As a result of the retroactive extension, the Company recorded a deferred tax asset before valuation allowance of $0.9 million for qualifying amounts incurred in 2012.  The deferred tax asset and corresponding valuation allowance were recorded in the period of enactment, which was the first quarter of 2013.  During the year ended December 31, 2013, the Company recorded an additional deferred tax asset and corresponding valuation allowance of $1.5 million for qualifying amounts incurred in 2013.
	The following table presents the principal components of the Company’s deferred tax assets (in thousands):
		December 31,
		2012			2013
	Deferred tax assets:
	Federal net operating loss carryforwards	$	23,634		$	50,265
	State net operating loss carryforwards	3,644			7,762
	Depreciation and amortization	5,428			5,793
	Tax credit carryforwards	443			2,984
	Stock-based compensation	357			2,248
	Other	99			779
	Total deferred tax assets	33,605			69,831
	Less: valuation allowance	(33,605		)	(69,831		)
	Net deferred tax assets	$	—		$	—
	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 has recorded full valuation allowances against its deferred tax assets at both December 31, 2012 and 2013, because management has determined that is it more likely than not that these assets will not be realized.  The increase in the valuation allowance in 2013 was related to the net loss incurred by the Company.
	As of December 31, 2013, the Company had federal and state net operating losses of approximately $4.4 million related to excess tax deductions that have been excluded from the table above.  The benefit of these net operating losses will be recognized as an increase in additional paid-in capital when it results in a reduction in taxable income.
	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,
		2011		2012		2013
	Federal income tax (benefit)/expense at statutory rate	(34.0	)%	(34.0	)%	(34.0	)%
	State income tax benefit	(4.8	)	(5.4	)	(5.1	)
	Permanent items	2.6		0.4		0.8
	Foreign rate differential	0		0		1.6
	Federal research and development credit	(1.8	)	0		(2.5	)
	Change in valuation allowance	38		39		39.2
	Effective income tax rate	0	%	0	%	0	%

Employee_Benefit_Plan

Employee Benefit Plan	12 Months Ended
	Dec. 31, 2013
Employee Benefit Plan	'
Employee Benefit Plan	'
	8. 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 and 2013, the Company made aggregate matching contributions of $137,000 and $277,000, respectively.

Commitments_and_Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2013
Commitments and Contingencies	'
Commitments and Contingencies	'
	9. Commitments and Contingencies
	The Company leases approximately 23,800 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 March 31, 2015.  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, 2013 (in thousands):
		Operating
		Leases
	2014	$	755
	2015	189
	2016	—
	Thereafter	—
	Total minimum lease payments	$	944
	The Company recorded $77,000, $166,000 and $647,000 in rent expense for the years ended December 31, 2011, 2012 and 2013, respectively.
	In January 2014, the Company entered into an amendment of its lease agreement whereby beginning in March 2014, it expanded the total leased space in the facility to 53,200 square feet and extended the term of the lease through June 30, 2017.  The amended lease provides for additional rent expense of approximately $940,000 on an annualized basis.  In addition, the amended lease increased the security deposit to approximately $0.7 million and continues to require the Company to pay a proportionate share of certain of the landlord’s annual operating costs.
	The Company has entered into agreements with certain vendors for the provision of services, including services related to data management clinical operation support services, 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, 2013
License Agreements	'
License Agreements	'
	10. 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 Junior Preferred Stock.  At the time of the license transaction, the fair value of Junior 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, 2013, the Company has not made any additional milestone payments under this license agreement.
	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.  As of December 31, 2013, the Company has made one milestone payment under this license agreement, in the amount of approximately $1.9 million, which became due upon dosing of the first patient in the Phase 3 ovarian cancer clinical trial in July 2013.
	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 to AstraZeneca during the year ended December 31, 2013.

Consolidated_Quarterly_Financi

Consolidated Quarterly Financial Data - Unaudited	12 Months Ended
	Dec. 31, 2013
Consolidated Quarterly Financial Data - Unaudited	'
Consolidated Quarterly Financial Data - Unaudited	'
	11. Consolidated Quarterly Financial Data - Unaudited
	The following table presents unaudited consolidated quarterly financial data for the years ended December 31, 2012 and 2013 (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,
		2012			2012			2012			2012			2013			2013			2013			2013
	Expenses:
	Research and development	$	8,150		$	11,532		$	11,876		$	15,642		$	16,503		$	18,177		$	22,163		$	18,882
	General and administrative	1,199			1,685			1,736			2,095			2,400			3,412			4,503			4,465
	Acquired in-process research and development	—			7,000		(a)	—			1,000			—			—			1,940			—
	Total expenses	9,349			20,217			13,612			18,737			18,903			21,589			28,606			23,347
	Loss from operations	(9,349		)	(20,217		)	(13,612		)	(18,737		)	(18,903		)	(21,589		)	(28,606		)	(23,347		)
	Interest income	20			39			53			40			34			25			17			7
	Net loss	$	(9,329	)	$	(20,178	)	$	(13,559	)	$	(18,697	)	$	(18,869	)	$	(21,564	)	$	(28,589	)	$	(23,340	)
	Net loss per share - basic and diluted	$	(13.59	)	$	(21.31	)	$	(0.52	)(b)	$	(0.70	)	$	(0.66	)	$	(0.67	)	$	(0.88	)	$	(0.72	)
	Weighted-average shares - basic and diluted	687			947			26,130		(b)	26,740			28,798			32,336			32,453			32,597
	(a)           In the quarter ended June 30, 2012, the Company paid an up-front license fee to Merck for niraparib.
	(b)          In July 2012, the Company completed its initial public offering, which resulted in net proceeds of approximately $78.0 million from the issuance of 6,430,183 shares of common stock, which includes the sale of 430,183 shares under the underwriters’ over-allotment option.  In connection with the initial public offering, all of the outstanding shares of the Company’s convertible preferred stock were converted into 19,410,490 shares of common stock.

Subsequent_Event

Subsequent Event	12 Months Ended
	Dec. 31, 2013
Subsequent Event	'
Subsequent Event	'
	12. Subsequent Event
	On March 10, 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, sublicenseable 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.  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 three development programs and is obligated to use commercially reasonable efforts to research, develop or commercialize at least one product under each development program.
	The Company is obligated to make an up-front, non-creditable and non-refundable cash payment of $17.0 million to AnaptysBio.  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 three 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 the amount of worldwide annual net sales achieved, and additional commercial milestone payments if specified levels of annual net sales of a product are attained.
	The Company has not yet completed its assessment of the accounting for this transaction.  The Company expects to report its accounting for this transaction in its Quarterly Report on Form 10-Q for the quarter ending March 31, 2014.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2013
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 and the related disclosures.  On an ongoing basis, management evaluates its estimates, including estimates related to accrued clinical trial expenses and stock-based compensation expense.  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 inputs	Quoted prices in active markets for identical assets or liabilities
	Level 2 inputs	Inputs other than quoted prices included within Level 1 that are observable for the asset or liability, either directly or indirectly
	Level 3 inputs	Unobservable 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, 2012 and 2013 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):
			December 31, 2012
	Description	Balance Sheet Classification	Total			Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	123,888		$	123,888	$	—	$	—
	Total assets		$	123,888		$	123,888	$	—	$	—
			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	$	—	$	—
	The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term maturities.
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.  No impairment losses have been recorded through December 31, 2013.
Research and Development Expenses	'
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and include, but are not limited to:
	·                  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;
	·                  expenses incurred under agreements with contract research organizations, investigative sites and research consortia in connection with the conduct of clinical trials and preclinical studies and related services, such as administrative, data management and biostatistics services;
	·                  the cost of acquiring, developing and manufacturing active pharmaceutical ingredients, clinical trial materials and other research and development materials;
	·                  facilities, depreciation and other expenses, which include direct and allocated expenses for rent and maintenance of facilities, insurance and other supplies; and
	·                  costs associated with preclinical activities and regulatory operations.
	Costs for certain development activities, such as clinical trials, 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.  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.  The up-front payments to acquire 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 does not also include processes or activities that would constitute a “business”, 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 all stock-based awards based on estimated fair values.  The Company determines the fair values of equity-based awards at the 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 convertible preferred stock (for the periods in which it was outstanding), outstanding stock options and unvested restricted stock, 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, prior to the use of the treasury stock method, due to their anti-dilutive effect (in thousands):
							The Period from
							March 26, 2010
		Years Ended December 31,					(Inception) to
		2011	2012		2013		December 31, 2013
	Convertible preferred stock	11,729	—		—		—
	Outstanding stock options	894	2,134		2,853		2,853
	Unvested restricted stock	641	349		102		102
		13,264	2,483		2,955		2,955
Recently Issued Accounting Pronouncements	'
	Recently Issued Accounting Pronouncements
	In July 2013, the Financial Accounting Standards Board, or FASB, issued Accounting Standards Update No. 2013-11, which requires entities to present an unrecognized tax benefit, or a portion of an unrecognized tax benefit, as a reduction to a deferred tax asset for a net operating loss carryforward or a similar tax loss or a tax credit carryforward, unless certain conditions exist.  This guidance is effective prospectively for fiscal years beginning after December 15, 2013.  Early adoption and retrospective application are permitted.  The Company expects to adopt this guidance effective January 1, 2014 and does not expect this adoption to have a material effect on its consolidated financial statements.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2012 and 2013 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):
			December 31, 2012
	Description	Balance Sheet Classification	Total			Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	123,888		$	123,888	$	—	$	—
	Total assets		$	123,888		$	123,888	$	—	$	—
			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	$	—	$	—
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, prior to the use of the treasury stock method, due to their anti-dilutive effect (in thousands):
							The Period from
							March 26, 2010
		Years Ended December 31,					(Inception) to
		2011	2012		2013		December 31, 2013
	Convertible preferred stock	11,729	—		—		—
	Outstanding stock options	894	2,134		2,853		2,853
	Unvested restricted stock	641	349		102		102
		13,264	2,483		2,955		2,955

Property_and_Equipment_Tables

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2013
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,
		2012			2013
	Furniture and fixtures	$	31		$	244
	Computer equipment and software	266			404
	Leasehold improvements	18			67
		315			715
	Less accumulated depreciation and amortization	(96		)	(275		)
	Total property and equipment, net	$	219		$	440

Accrued_Expenses_Tables

Accrued Expenses (Tables)	12 Months Ended
	Dec. 31, 2013
Accrued Expenses	'
Schedule of accrued expenses	'
	The following table presents the components of accrued expenses (in thousands):
		December 31,
		2012		2013
	Research and development	$	6,635	$	7,422
	Salaries, bonuses and other compensation	1,316		2,462
	Professional services	282		389
	Other accrued expenses	312		268
	Total accrued expenses	$	8,545	$	10,541

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2013
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 condensed consolidated statements of operations and comprehensive loss (in thousands):
											The Period from
											March 26, 2010
		Years Ended December 31,									(Inception) to
		2011			2012			2013			December 31, 2013
	Research and development	$	46		$	544		$	2,034		$	2,624
	General and administrative	259			1,259			5,725			7,243
	Total stock-based compensation expense	$	305		$	1,803		$	7,759		$	9,867
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, 2012	349,334		$	0.15
	Granted	1,114		46.22
	Vested	(248,036	)	0.1
	Forfeited	—		—
	Unvested restricted stock at December 31, 2013	102,412		$	0.76
Summary of the Company's stock option activity and related information	'
		Shares		Weighted-average			Weighted-average		Aggregate
				exercise price per			remaining		intrinsic value
				share			contractual term		(in thousands)
							(years)
	Outstanding at December 31, 2012	2,134,185		$	5.52
	Granted	916,250		28.13
	Exercised	(162,480	)	3.9
	Cancelled	(35,162	)	13.85
	Outstanding at December 31, 2013	2,852,793		$	12.77		8.4		$	46,708
	Vested at December 31, 2013	863,713		$	4.73		7.9		$	20,305
	Vested and expected to vest at December 31, 2013 (a)	2,852,793		$	12.77		8.4		$	46,708
	(a)         This represents the number of vested options as of December 31, 2013, plus the number of unvested options expected to vest as of December 31, 2013, based on the unvested options at December 31, 2013, adjusted for the estimated forfeiture rate of 0%.
Schedule of fair value of each employee stock option estimated at the date of grant using a Black-Scholes option-pricing model	'
		Years Ended December 31,
		2011		2012		2013
	Dividend yield	—		—		—
	Volatility	67% - 68%		66% - 71%		73% - 78%
	Risk-free interest rate	1.07% - 2.03%		0.89% - 1.56%		1.07% - 2.05%
	Expected term (years)	6.25		6.25		5.50 - 6.25

Income_Taxes_Tables

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2013
Income Taxes	'
Schedule of principal components of the Company's deferred tax assets	'
	The following table presents the principal components of the Company’s deferred tax assets (in thousands):
		December 31,
		2012			2013
	Deferred tax assets:
	Federal net operating loss carryforwards	$	23,634		$	50,265
	State net operating loss carryforwards	3,644			7,762
	Depreciation and amortization	5,428			5,793
	Tax credit carryforwards	443			2,984
	Stock-based compensation	357			2,248
	Other	99			779
	Total deferred tax assets	33,605			69,831
	Less: valuation allowance	(33,605		)	(69,831		)
	Net deferred tax assets	$	—		$	—
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	'
		Years Ended December 31,
		2011		2012		2013
	Federal income tax (benefit)/expense at statutory rate	(34.0	)%	(34.0	)%	(34.0	)%
	State income tax benefit	(4.8	)	(5.4	)	(5.1	)
	Permanent items	2.6		0.4		0.8
	Foreign rate differential	0		0		1.6
	Federal research and development credit	(1.8	)	0		(2.5	)
	Change in valuation allowance	38		39		39.2
	Effective income tax rate	0	%	0	%	0	%

Commitments_and_Contingencies_

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2013 (in thousands):
		Operating
		Leases
	2014	$	755
	2015	189
	2016	—
	Thereafter	—
	Total minimum lease payments	$	944

Consolidated_Quarterly_Financi1

Consolidated Quarterly Financial Data - Unaudited (Tables)	12 Months Ended
	Dec. 31, 2013
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, 2012 and 2013 (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,
		2012			2012			2012			2012			2013			2013			2013			2013
	Expenses:
	Research and development	$	8,150		$	11,532		$	11,876		$	15,642		$	16,503		$	18,177		$	22,163		$	18,882
	General and administrative	1,199			1,685			1,736			2,095			2,400			3,412			4,503			4,465
	Acquired in-process research and development	—			7,000		(a)	—			1,000			—			—			1,940			—
	Total expenses	9,349			20,217			13,612			18,737			18,903			21,589			28,606			23,347
	Loss from operations	(9,349		)	(20,217		)	(13,612		)	(18,737		)	(18,903		)	(21,589		)	(28,606		)	(23,347		)
	Interest income	20			39			53			40			34			25			17			7
	Net loss	$	(9,329	)	$	(20,178	)	$	(13,559	)	$	(18,697	)	$	(18,869	)	$	(21,564	)	$	(28,589	)	$	(23,340	)
	Net loss per share - basic and diluted	$	(13.59	)	$	(21.31	)	$	(0.52	)(b)	$	(0.70	)	$	(0.66	)	$	(0.67	)	$	(0.88	)	$	(0.72	)
	Weighted-average shares - basic and diluted	687			947			26,130		(b)	26,740			28,798			32,336			32,453			32,597
	(a)           In the quarter ended June 30, 2012, the Company paid an up-front license fee to Merck for niraparib.
	(b)          In July 2012, the Company completed its initial public offering, which resulted in net proceeds of approximately $78.0 million from the issuance of 6,430,183 shares of common stock, which includes the sale of 430,183 shares under the underwriters’ over-allotment option.  In connection with the initial public offering, all of the outstanding shares of the Company’s convertible preferred stock were converted into 19,410,490 shares of common stock.

Nature_of_Business_Details

Nature of Business (Details) (USD $)	0 Months Ended			1 Months Ended			12 Months Ended		45 Months Ended
	Jul. 23, 2012	Jun. 28, 2012	Jun. 19, 2012	Feb. 28, 2014	Mar. 31, 2013	Jul. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Jul. 03, 2012
							segment
							item
Nature of Business	'	'	'	'	'	'	'	'	'	'
Number of operating segments	'	'	'	'	'	'	1	'	'	'
Number of business activities	'	'	'	'	'	'	1	'	'	'
Reverse stock split, conversion ratio	'	'	3.5	'	'	'	'	'	'	'
Number of shares of common stock sold in initial public offering	'	6,000,000	'	3,200,000	5,428,000	6,430,183	'	'	'	'
Common stock issue price (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	'	'	'	'	'	'	'	'	'
Number of shares of authorized common stock subsequent to filing of amended and restated certificate of incorporation	'	'	'	'	'	'	100,000,000	100,000,000	100,000,000	'
Number of shares of authorized preferred stock subsequent to filing of amended and restated certificate of incorporation	'	'	'	'	'	'	10,000,000	10,000,000	10,000,000	'
Common stock, par value (in dollars per share)	'	'	'	$0.00	'	'	$0.00	$0.00	$0.00	'
Preferred stock, par value (in dollars per share)	'	'	'	'	'	'	$0.00	$0.00	$0.00	'
Gross proceeds from the sale of common stock in an underwritten public offering	'	'	'	100,800,000	'	'	'	'	'	'
Net proceeds from the sale of common stock in an underwritten public offering	'	'	'	94,100,000	91,300,000	'	91,312,000	77,960,000	169,272,000	'
Subsequent event	'	'	'	'	'	'	'	'	'	'
Nature of Business	'	'	'	'	'	'	'	'	'	'
Number of shares of common stock sold in initial public offering	'	'	'	3,200,000	'	'	'	'	'	'
Common stock issue price (in dollars per share)	'	'	'	$31.50	'	'	'	'	'	'
Net proceeds from the sale of common stock in an underwritten public offering	'	'	'	$94,100,000	'	'	'	'	'	'

Summary_of_Significant_Account3

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2013	Dec. 31, 2012
	segment	Total	Total	Total	Total	Quoted Prices in Active Markets (Level 1)	Quoted Prices in Active Markets (Level 1)	Quoted Prices in Active Markets (Level 1)	Quoted Prices in Active Markets (Level 1)
				Money market funds	Money market funds			Money market funds	Money market funds
Segment Information	'	'	'	'	'	'	'	'	'
Number of operating segments	1	'	'	'	'	'	'	'	'
Fair Value of Financial Instruments	'	'	'	'	'	'	'	'	'
Cash and cash equivalents	'	'	'	$128,801	$123,888	'	'	$128,801	$123,888
Assets	'	$128,801	$123,888	'	'	$128,801	$123,888	'	'

Summary_of_Significant_Account4

Summary of Significant Accounting Policies (Details 2) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2013
Property and Equipment	'
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

Summary_of_Significant_Account5

Summary of Significant Accounting Policies (Details 3)	12 Months Ended			45 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Net Loss per Share	'	'	'	'
Amounts 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	2,955	2,483	13,264	2,955
Convertible preferred stock	'	'	'	'
Net Loss per Share	'	'	'	'
Amounts 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	'	'	11,729	'
Outstanding stock options	'	'	'	'
Net Loss per Share	'	'	'	'
Amounts 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	2,853	2,134	894	2,853
Unvested restricted stock	'	'	'	'
Net Loss per Share	'	'	'	'
Amounts 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	102	349	641	102

Property_and_Equipment_Details

Property and Equipment (Details) (USD $)	12 Months Ended			45 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Property and Equipment	'	'	'	'
Gross	$715	$315	'	$715
Less accumulated depreciation and amortization	-275	-96	'	-275
Total property and equipment, net	440	219	'	440
Total depreciation expense	179	64	35	285
Furniture and fixtures	'	'	'	'
Property and Equipment	'	'	'	'
Gross	244	31	'	244
Computer equipment and software	'	'	'	'
Property and Equipment	'	'	'	'
Gross	404	266	'	404
Leasehold improvements	'	'	'	'
Property and Equipment	'	'	'	'
Gross	$67	$18	'	$67

Accrued_Expenses_Details

Accrued Expenses (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012
In Thousands, unless otherwise specified
Accrued Expenses	'	'
Research and development	$7,422	$6,635
Salaries, bonuses and other compensation	2,462	1,316
Professional services	389	282
Other accrued expenses	268	312
Total accrued expenses	$10,541	$8,545

Convertible_Preferred_Stock_an1

Convertible Preferred Stock and Stockholders' Equity (Details) (USD $)

0 Months Ended

1 Months Ended

12 Months Ended

45 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

1 Months Ended

Jul. 23, 2012

Jun. 28, 2012

Feb. 28, 2014

Mar. 31, 2013

Jul. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2013

Jul. 03, 2012

Jul. 03, 2012

Mar. 21, 2012

Jul. 07, 2011

Jun. 06, 2011

Dec. 31, 2013

Dec. 31, 2011

Jun. 30, 2011

Jul. 23, 2012

Jun. 28, 2012

Feb. 28, 2014

Mar. 31, 2013

Dec. 31, 2013

Jul. 03, 2012

Convertible Preferred Stock

Series B Convertible Preferred Stock

Series B Convertible Preferred Stock

Series B Convertible Preferred Stock

Series B Convertible Preferred Stock

Series B Convertible Preferred Stock

Series B Convertible Preferred Stock

Common stock

Common stock

Common stock

Common stock

Common stock

Common stock

Series B Purchase Agreement

Series B Purchase Agreement

Series B Purchase Agreement

Series B Purchase Agreement

Series B Purchase Agreement

Series B Purchase Agreement

item

Convertible Preferred Stock and Stockholders' Equity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, shares authorized

'

'

'

'

'

10,000,000

10,000,000

10,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares authorized

'

'

'

'

'

100,000,000

100,000,000

100,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, par value (in dollars per share)

'

'

'

'

'

$0.00

$0.00

$0.00

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, par value (in dollars per share)

'

'

$0.00

'

'

$0.00

$0.00

$0.00

'

'

'

'

'

'

'

'

'

'

$0.00

$0.00

'

'

Preferred stock, shares issued

'

'

'

'

'

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Preferred stock, shares outstanding

'

'

'

'

'

0

0

0

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares issued

'

'

'

'

'

32,739,008

27,136,329

32,739,008

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Common stock, shares outstanding

'

'

'

'

'

32,739,008

27,136,329

32,739,008

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Convertible Preferred Stock and Stockholders' Equity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Convertible preferred stock, shares outstanding

'

'

'

'

'

'

'

'

'

67,936,761

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares of common stock issued on conversion from convertible preferred stock

'

'

'

'

'

'

'

'

19,410,490

'

'

'

'

'

'

'

'

'

'

'

'

19,410,490

Shares sold

'

6,000,000

3,200,000

5,428,000

6,430,183

'

'

'

'

'

26,884,442

1,161,523

18,390,796

'

'

'

'

6,000,000

3,200,000

5,428,000

'

'

Net proceeds from sale of shares

'

'

'

'

'

'

'

'

'

'

$58,300,000

'

'

'

$42,100,000

'

'

'

'

'

'

'

Value of shares authorized for issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

101,000,000

'

'

'

'

'

'

Value of additional shares required to be sold upon the occurrence of, or in connection with, certain milestone events

'

'

'

'

'

'

'

'

'

'

'

'

'

58,500,000

'

'

'

'

'

'

'

'

Common stock issue price, in an underwritten public offering (in dollars per share)

'

$13.50

$31.50

$18

'

'

'

'

'

'

$2.17

$2.17

$2.17

'

'

'

'

$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

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

430,183

'

'

'

'

'

Proceeds from sale of common stock, net of underwriting discount and commissions

78,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

78,000,000

'

'

'

'

'

Common stock, par value (in dollars per share)

'

'

$0.00

'

'

$0.00

$0.00

$0.00

'

'

'

'

'

'

'

'

'

'

$0.00

$0.00

'

'

Gross proceeds from the sale of common stock in an underwritten public offering

'

'

100,800,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

100,800,000

97,700,000

'

'

Net proceeds from the sale of common stock in an underwritten public offering

'

'

$94,100,000

$91,300,000

'

$91,312,000

$77,960,000

$169,272,000

'

'

'

'

'

'

'

'

'

'

$94,100,000

$91,300,000

'

'

Number of votes per share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1

'

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (USD $)	12 Months Ended			45 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Stock-based compensation expense	'	'	'	'
Total stock-based compensation expense	$7,759,000	$1,803,000	$305,000	$9,867,000
Research and development	'	'	'	'
Stock-based compensation expense	'	'	'	'
Total stock-based compensation expense	2,034,000	544,000	46,000	2,624,000
General and administrative	'	'	'	'
Stock-based compensation expense	'	'	'	'
Total stock-based compensation expense	$5,725,000	$1,259,000	$259,000	$7,243,000

StockBased_Compensation_Detail1

Stock-Based Compensation (Details 2) (USD $)

12 Months Ended

45 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

0 Months Ended

12 Months Ended

45 Months Ended

0 Months Ended

45 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Feb. 07, 2011

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

10-May-10

10-May-10

Feb. 07, 2011

Feb. 07, 2011

Feb. 07, 2011

Dec. 31, 2013

10-May-10

Dec. 31, 2013

10-May-10

Dec. 31, 2013

Apr. 27, 2012

Jan. 02, 2014

Dec. 31, 2013

Dec. 31, 2013

Jun. 06, 2011

10-May-10

Mar. 26, 2010

10-May-10

Dec. 31, 2013

Dec. 31, 2013

Stock options

Stock options

Stock options

Stock options

Stock options

Stock options

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

Restricted deferred common stock awards

2012 Incentive Plan

2012 Incentive Plan

2012 Incentive Plan

2012 Incentive Plan

2012 Incentive Plan

2010 Incentive Plan

2010 Incentive Plan

2010 Incentive Plan

2010 Incentive Plan

2010 Incentive Plan

2010 Incentive Plan

Vesting one year from awards vesting start date

Vesting over subsequent 36 months

Non-employee consultant

item

Founders

Founders

Founders and one employee

Founders and one employee

Founders and one employee

Non-employee consultant

Common stock

Common stock

Series A-1 Convertible Preferred Stock

Common stock

Common stock

Common stock

Stock options

Common stock awards

Common stock

Common stock

Common stock

Series A-1 Convertible Preferred Stock

Stock options

Restricted deferred common stock awards

Vesting on March 26, 2010

Vesting over subsequent 48 months

Vesting over subsequent 36 months

Vesting on January 6, 2012

Founders

Founders

Founders

Subsequent events

Stock-Based Compensation

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting percentage

'

'

'

'

'

'

'

25.00%

75.00%

'

'

'

'

'

25.00%

75.00%

'

75.00%

25.00%

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Vesting period

'

'

'

'

'

'

'

'1 year

'3 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Exercisable period from the date of grant

'

'

'

'

'10 years

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares available for grant under the plan

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,428,571

'

'

'

1,981,130

357,142

357

'

'

'

Number of shares available for future grants that were added to the total number of shares reserved for issuance

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

6,857

1,309,560

'

'

'

'

'

'

'

'

Annual increase in common stock available for grant as a percentage of common stock outstanding

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

4.00%

'

'

'

'

'

'

'

'

'

'

Options granted (in shares)

'

'

'

'

916,250

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,291,604

21,012

'

'

'

'

1,785,703

'

Options exercised (in shares)

'

'

'

'

162,480

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

12,468

'

'

'

'

'

169,028

'

Options cancelled (in shares)

'

'

'

'

35,162

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

25,756

'

'

'

'

'

17,262

'

Conversion ratio for conversion of preferred stock into common stock (in shares)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000

'

'

'

'

'

'

'

'

1,000

'

'

Restricted stock awards granted (in shares)

'

'

'

'

'

'

'

'

'

'

'

1,114

'

'

'

'

188,570

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

188,570

Shares of common stock purchased

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,071

'

'

'

'

'

'

'

'

'

'

'

'

Shares of common stock granted

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,071,426

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of non-founding employees to whom shares of common stock are allotted as compensation for services provided

'

'

'

'

'

'

'

'

'

'

1

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock-based compensation expense

$7,759,000

$1,803,000

$305,000

$9,867,000

$6,770,000

$1,526,000

$281,000

'

'

$1,132,000

'

$669,000

$24,000

$24,000

'

'

'

'

'

$646,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

StockBased_Compensation_Detail2

Stock-Based Compensation (Details 3) (USD $)

12 Months Ended

45 Months Ended

12 Months Ended

1 Months Ended

12 Months Ended

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Jun. 30, 2013

Oct. 31, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Dec. 31, 2013

Restricted stock awards

Restricted stock awards

Restricted stock awards

Restricted stock awards

Stock options

Stock options

Stock options

Stock options

Stock options

Stock options

Stock options

Stock options

Stock options

Non-employee consultant

Minimum

Maximum

Former CFO

Non-employee consultant

Shares

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested restricted at the beginning of the period (in shares)

'

'

'

'

349,334

'

'

'

'

'

'

'

'

'

'

'

'

Granted (in shares)

'

'

'

'

1,114

'

'

'

'

'

'

'

'

'

'

'

'

Vested (in shares)

'

'

'

'

-248,036

'

'

'

'

'

'

'

'

'

'

'

'

Unvested restricted at the end of the period (in shares)

'

'

'

'

102,412

349,334

'

'

'

'

'

'

'

'

'

'

'

Weighted-average grant date fair value per share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Unvested restricted at the beginning of the period (in dollars per share)

'

'

'

'

$0.15

'

'

'

'

'

'

'

'

'

'

'

'

Granted (in dollars per share)

'

'

'

'

$46.22

$0

$0.53

'

'

'

'

'

'

'

'

'

'

Vested (in dollars per share)

'

'

'

'

$0.10

'

'

'

'

'

'

'

'

'

'

'

'

Unvested restricted at the end of the period (in dollars per share)

'

'

'

'

$0.76

$0.15

'

'

'

'

'

'

'

'

'

'

'

Additional disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Total grant date fair value of vested restricted stock

'

'

'

'

$25,000

$47,000

$0

'

'

'

'

'

'

'

'

'

'

Total unrecognized compensation cost related to unvested restricted stock (in dollars)

'

'

'

'

95,000

'

'

'

'

'

'

'

'

'

'

'

'

Weighted average period over which unrecognized compensation costs are expected to be recognized

'

'

'

'

'4 months 24 days

'

'

'

'

'

'2 years 6 months

'

'

'

'

'

'

Shares

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding at the beginning of the period (in shares)

'

'

'

'

'

'

'

'

'

'

2,134,185

'

'

'

'

'

'

Granted (in shares)

'

'

'

'

'

'

'

'

'

'

916,250

'

'

'

'

'

'

Exercised (in shares)

'

'

'

'

'

'

'

'

'

'

-162,480

'

'

'

'

'

'

Cancelled (in shares)

'

'

'

'

'

'

'

'

'

'

-35,162

'

'

'

'

'

'

Outstanding at the end of the period (in shares)

'

'

'

'

'

'

'

'

'

'

2,852,793

2,134,185

'

'

'

'

'

Vested at the end of the period (in shares)

'

'

'

'

'

'

'

'

'

'

863,713

'

'

'

'

'

'

Vested and expected to vest at the end of the period (in shares)

'

'

'

'

'

'

'

'

'

'

2,852,793

'

'

'

'

'

'

Estimated forfeiture rate (as a percent)

'

'

'

'

'

'

'

'

'

'

0.00%

'

'

'

'

'

'

Weighted-average price per share

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding at the beginning of the period (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$5.52

'

'

'

'

'

'

Granted (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$28.13

'

'

'

'

'

'

Exercised (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$3.90

'

'

'

'

'

'

Cancelled (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$13.85

'

'

'

'

'

'

Outstanding at the end of the period (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$12.77

$5.52

'

'

'

'

'

Vested at the end of the period (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$4.73

'

'

'

'

'

'

Vested and expected to vest at the end of the period (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$12.77

'

'

'

'

'

'

Weighted-average remaining contractual term (years)

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding at the end of the period

'

'

'

'

'

'

'

'

'

'

'8 years 4 months 24 days

'

'

'

'

'

'

Vested at the end of the period

'

'

'

'

'

'

'

'

'

'

'7 years 10 months 24 days

'

'

'

'

'

'

Vested and expected to vest at the end of the period

'

'

'

'

'

'

'

'

'

'

'8 years 4 months 24 days

'

'

'

'

'

'

Aggregate intrinsic value

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Outstanding at the end of the period (in dollars)

'

'

'

'

'

'

'

'

'

'

46,708,000

'

'

'

'

'

'

Vested at the end of the period (in dollars)

'

'

'

'

'

'

'

'

'

'

20,305,000

'

'

'

'

'

'

Vested and expected to vest at the end of the period

'

'

'

'

'

'

'

'

'

'

46,708,000

'

'

'

'

'

'

Assumptions used to calculate fair value of employee stock option at the date of grant

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Volatility, minimum (as a percent)

'

'

'

'

'

'

'

'

'

'

73.00%

66.00%

67.00%

'

'

'

'

Volatility, maximum (as a percent)

'

'

'

'

'

'

'

'

'

'

78.00%

71.00%

68.00%

'

'

'

'

Risk-free interest rate, minimum (as a percent)

'

'

'

'

'

'

'

'

'

'

1.07%

0.89%

1.07%

'

'

'

'

Risk-free interest rate, maximum (as a percent)

'

'

'

'

'

'

'

'

'

'

2.05%

1.56%

2.03%

'

'

'

'

Expected term

'

'

'

'

'

'

'

'

'

'

'

'6 years 3 months

'6 years 3 months

'5 years 6 months

'6 years 3 months

'

'

Additional disclosure

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Stock-based compensation expense

7,759,000

1,803,000

305,000

9,867,000

669,000

24,000

24,000

646,000

'

'

6,770,000

1,526,000

281,000

'

'

'

1,132,000

Weighted-average grant date fair value of options granted (in dollars per share)

'

'

'

'

'

'

'

'

'

'

$18.48

$5.29

$2.63

'

'

'

'

Aggregate intrinsic value of options exercised

'

'

'

'

'

'

'

'

'

'

4,800,000

200,000

0

'

'

'

'

Total unrecognized compensation cost related to unvested restricted stock

'

'

'

'

'

'

'

'

'

'

17,000,000

'

'

'

'

'

'

Weighted average period over which unrecognized compensation costs are expected to be recognized

'

'

'

'

'4 months 24 days

'

'

'

'

'

'2 years 6 months

'

'

'

'

'

'

Shares issued during the period

'

'

'

'

'

'

'

'

4,368

16,644

'

'

'

'

'

'

'

Aggregate value of shares issued to certain non-employee board members in lieu of fees

253,000

253,000

'

'

'

'

'

'

300,000

300,000

'

'

'

'

'

'

'

Incremental stock-based compensation expense

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$1,800,000

'

StockBased_Compensation_Detail3

Stock-Based Compensation (Details 4) (USD $)	12 Months Ended			45 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013
Stock-Based Compensation	'	'	'	'
Stock-based compensation expense	$7,759,000	$1,803,000	$305,000	$9,867,000
2012 ESPP	'	'	'	'
Stock-Based Compensation	'	'	'	'
Common stock reserved for future issuance (in shares)	275,000	'	'	275,000
Number of shares remaining available for issuance	267,169	'	'	267,169
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	'	'	'
Shares issued	7,831	'	'	'
Stock-based compensation expense	67,000	'	'	'
2012 ESPP | Maximum	'	'	'	'
Stock-Based Compensation	'	'	'	'
Purchase of common stock based on fair market value	$25,000	'	'	'

Income_Taxes_Details

Income Taxes (Details) (USD $)	Dec. 31, 2013
In Millions, unless otherwise specified
Federal	'
Operating loss carryforwards	'
Net operating loss carryforwards	$152.20
State	'
Operating loss carryforwards	'
Net operating loss carryforwards	$151.30

Income_Taxes_Details_2

Income Taxes (Details 2) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes	'	'	'
Gross unrecognized tax benefits related to research and development credits	$500,000	'	'
Deferred tax asset before valuation allowance recorded as a result of retroactive extension of the research credit	1,500,000	900,000	'
Federal and state net operating losses related to excess tax deductions	4,400,000	'	'
Deferred tax assets :	'	'	'
Federal net operating loss carryforwards	50,265,000	23,634,000	'
State net operating loss carryforwards	7,762,000	3,644,000	'
Depreciation and amortization	5,793,000	5,428,000	'
Tax credit carryforwards	2,984,000	443,000	'
Stock-based compensation	2,248,000	357,000	'
Other	779,000	99,000	'
Total deferred tax assets	69,831,000	33,605,000	'
Less valuation allowance	-69,831,000	-33,605,000	'
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)	-5.10%	-5.40%	-4.80%
Permanent items (as a percent)	0.80%	0.40%	2.60%
Foreign rate differential	1.60%	0.00%	0.00%
Federal research and development credit (as a percent)	-2.50%	0.00%	-1.80%
Change in valuation allowance (as a percent)	39.20%	39.00%	38.00%
Effective income tax rate (as a percent)	0.00%	0.00%	0.00%
Federal	'	'	'
Income Taxes	'	'	'
Research and development tax credit carryforwards	$3,100,000	'	'

Employee_Benefit_Plan_Details

Employee Benefit Plan (Details) (USD $)	12 Months Ended
	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	$277,000	$137,000

Commitments_and_Contingencies_1

Commitments and Contingencies (Details) (USD $)	12 Months Ended			1 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jan. 31, 2014	Dec. 31, 2013
				Subsequent events	Operating lease
				Amendment of operating lease	sqft
				sqft
Future minimum rental commitments	'	'	'	'	'
2014	$755,000	'	'	'	'
2015	189,000	'	'	'	'
Total	944,000	'	'	'	'
Rent expense	647,000	166,000	77,000	'	'
Commitments and Contingencies	'	'	'	'	'
Leased office space (in square feet)	'	'	'	53,200	23,800
Period of free rent	'	'	'	'	'1 month
Additional rent expense	'	'	'	940,000	'
Increase in security deposit	'	'	'	$700,000	'

License_Agreements_Details

License Agreements (Details) (USD $)

0 Months Ended

1 Months Ended

3 Months Ended

12 Months Ended

45 Months Ended

1 Months Ended

1 Months Ended

12 Months Ended

1 Months Ended

1 Months Ended

12 Months Ended

Jun. 28, 2012

Feb. 28, 2014

Mar. 31, 2013

Jul. 31, 2012

Sep. 30, 2013

Dec. 31, 2012

Jun. 30, 2012

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2010

Nov. 30, 2012

Mar. 31, 2011

Dec. 31, 2011

Dec. 31, 2013

Jul. 31, 2013

Jun. 30, 2012

Dec. 31, 2013

Dec. 31, 2013

Oct. 31, 2012

Dec. 31, 2013

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

License Agreement

OPKO

OPKO

OPKO

Amgen, Inc

Amgen, Inc

Amgen, Inc

Amgen, Inc

Merck Sharp & Dohme Corp

Merck Sharp & Dohme Corp

Merck Sharp & Dohme Corp

Merck Sharp & Dohme Corp

AstraZeneca UK Limited

AstraZeneca UK Limited

Maximum

Junior Preferred Stock

Maximum

item

Maximum

item

License Agreements

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Amount paid upon signing the agreement

'

'

'

'

'

'

'

'

'

'

'

$6,000,000

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares issued

6,000,000

3,200,000

5,428,000

6,430,183

'

'

'

'

'

'

'

'

'

1,500,000

'

'

'

'

'

'

'

'

'

'

Fair value of shares issued

'

'

'

'

'

'

'

'

'

'

630,000

'

'

630,000

'

'

'

'

'

'

'

'

'

'

Amount required to be paid for development milestones if specified regulatory and initial commercial sales milestones are achieved

'

'

'

'

'

'

'

'

'

'

'

'

30,000,000

'

'

'

'

'

'

'

'

'

'

'

Additional milestone payments required if specified levels of annual net sales of rolapitant are achieved

'

'

'

'

'

'

'

'

'

'

'

'

85,000,000

'

'

'

'

'

'

'

'

'

'

'

Acquired in-process research and development expense

'

'

'

'

1,940,000

1,000,000

7,000,000

1,940,000

8,000,000

500,000

17,070,000

6,600,000

'

'

'

500,000

'

'

'

7,000,000

'

'

'

'

Up-front fees paid

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

500,000

'

'

'

'

'

400,000

'

Milestone payments required, if specified clinical development, regulatory, initial commercialization and annual net product sales milestones are achieved

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

138,000,000

'

'

'

'

'

'

Additional milestone payment

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1,000,000

'

'

'

'

'

'

'

'

'

Up-front fees payable

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

7,000,000

'

'

'

'

Amount required to be paid for development and regulatory milestones for the first indication

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

57,000,000

'

'

Amount required to be paid for development and regulatory milestones for each successive indication

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

29,500,000

'

'

Amount required to be paid for one-time sales milestones based on the achievement of annual sales objectives

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

87,500,000

'

'

Number of milestone payments made

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

1

'

'

'

Milestone payments made

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

$1,900,000

'

'

'

'

$200,000

Number of non-exclusive license agreements entered into by the entity

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

2

'

Consolidated_Quarterly_Financi2

Consolidated Quarterly Financial Data - Unaudited (Details) (USD $)

0 Months Ended

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

45 Months Ended

Jul. 23, 2012

Jun. 28, 2012

Feb. 28, 2014

Mar. 31, 2013

Jul. 31, 2012

Dec. 31, 2013

Sep. 30, 2013

Jun. 30, 2013

Mar. 31, 2013

Dec. 31, 2012

Sep. 30, 2012

Jun. 30, 2012

Mar. 31, 2012

Dec. 31, 2010

Dec. 31, 2013

Dec. 31, 2012

Dec. 31, 2011

Dec. 31, 2013

Jul. 03, 2012

Expenses:

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Research and development

'

'

'

'

'

$18,882,000

$22,163,000

$18,177,000

$16,503,000

$15,642,000

$11,876,000

$11,532,000

$8,150,000

'

$75,725,000

$47,200,000

$11,768,000

$134,739,000

'

General and administrative

'

'

'

'

'

4,465,000

4,503,000

3,412,000

2,400,000

2,095,000

1,736,000

1,685,000

1,199,000

'

14,780,000

6,715,000

3,158,000

26,321,000

'

Acquired in-process research and development

'

'

'

'

'

'

1,940,000

'

'

1,000,000

'

7,000,000

'

'

1,940,000

8,000,000

500,000

17,070,000

'

Total expenses

'

'

'

'

'

23,347,000

28,606,000

21,589,000

18,903,000

18,737,000

13,612,000

20,217,000

9,349,000

'

92,445,000

61,915,000

15,426,000

178,130,000

'

Loss from operations

'

'

'

'

'

-23,347,000

-28,606,000

-21,589,000

-18,903,000

-18,737,000

-13,612,000

-20,217,000

-9,349,000

'

-92,445,000

-61,915,000

-15,426,000

-178,130,000

'

Interest income

'

'

'

'

'

7,000

17,000

25,000

34,000

40,000

53,000

39,000

20,000

'

83,000

152,000

38,000

293,000

'

Net loss

'

'

'

'

'

-23,340,000

-28,589,000

-21,564,000

-18,869,000

-18,697,000

-13,559,000

-20,178,000

-9,329,000

-8,975,000

-92,362,000

-61,763,000

-16,398,000

-179,498,000

'

Net loss per share - basic and diluted (in dollars per share)

'

'

'

'

'

($0.72)

($0.88)

($0.67)

($0.66)

($0.70)

($0.52)

($21.31)

($13.59)

'

($2.93)

($4.51)

($31.90)

($14.70)

'

Weighted-average shares - basic and diluted

'

'

'

'

'

32,597,000

32,453,000

32,336,000

28,798,000

26,740,000

26,130,000

947,000

687,000

'

31,559,000

13,696,000

514,000

12,211,000

'

Net proceeds from the issuance of common stock

$78,000,000

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares issued

'

6,000,000

3,200,000

5,428,000

6,430,183

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares sold under underwriters' over-allotment option

430,183

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

Number of shares of common stock issued on conversion from convertible preferred stock

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

'

19,410,490

Subsequent_Event_Details

Subsequent Event (Details) (Subsequent event, AnaptysBio, Collaboration and exclusive license agreement, USD $)	0 Months Ended
In Millions, unless otherwise specified	Mar. 10, 2014
	item
Subsequent event	'
Number of development programs	3
Up-front, non-creditable and non-refundable cash payment payable	$17
Minimum	'
Subsequent event	'
Number of products under each development program for which research, development or commercialization is conducted	1
Maximum	'
Subsequent event	'
Period for reimbursement of specified cost under agreement	'2 years
Termination period	'90 days
Milestone payments required, if certain research and development milestone events are achieved	18
Additional milestone payments required, if certain U.S. and non-U.S. regulatory submissions and approvals occur in multiple indications	$90