Tesaro (TSRO) 10-Q 25 Jul 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014	Jul. 21, 2014
Document and Entity Information	'	'
Entity Registrant Name	'TESARO, Inc.	'
Entity Central Index Key	'0001491576	'
Document Type	'10-Q	'
Document Period End Date	30-Jun-14	'
Amendment Flag	'false	'
Current Fiscal Year End Date	'--12-31	'
Entity Current Reporting Status	'Yes	'
Entity Filer Category	'Accelerated Filer	'
Entity Common Stock, Shares Outstanding	'	36,043,167
Document Fiscal Year Focus	'2014	'
Document Fiscal Period Focus	'Q2	'

Condensed_Consolidated_Balance

Condensed Consolidated Balance Sheets (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Current assets:	'	'
Cash and cash equivalents	$151,088	$130,310
Other current assets	2,997	4,029
Total current assets	154,085	134,339
Property and equipment, net	1,147	440
Other assets	908	799
Total assets	156,140	135,578
Current liabilities:	'	'
Accounts payable	2,849	1,869
Accrued expenses	16,163	10,541
Other current liabilities	'	13
Total current liabilities	19,012	12,423
Other non-current liabilities	'	3
Commitments and contingencies (Note 7)	'	'
Stockholders' equity:	'	'
Preferred stock, $0.0001 par value; 10,000,000 shares authorized at both December 31, 2013 and June 30, 2014; no shares issued or outstanding at both December 31, 2013 and June 30, 2014	'	'
Common stock, $0.0001 par value; 100,000,000 shares authorized at both December 31, 2013 and June 30, 2014; 32,739,008 and 36,039,105 shares issued and outstanding at December 31, 2013 and June 30, 2014, respectively	4	3
Additional paid-in capital	403,473	302,647
Accumulated deficit	-266,349	-179,498
Total stockholders' equity	137,128	123,152
Total liabilities and stockholders' equity	$156,140	$135,578

Condensed_Consolidated_Balance1

Condensed Consolidated Balance Sheets (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
Condensed Consolidated Balance Sheets	'	'
Preferred stock, par value (in dollars per share)	$0.00	$0.00
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$0.00	$0.00
Common stock, shares authorized	100,000,000	100,000,000
Common stock, shares issued	36,039,105	32,739,008
Common stock, shares outstanding	36,039,105	32,739,008

Condensed_Consolidated_Stateme

Condensed Consolidated Statements of Operations and Comprehensive Loss (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Expenses:	'	'	'	'
Research and development	$30,569	$18,177	$58,686	$34,680
General and administrative	5,587	3,412	10,275	5,812
Acquired in-process research and development	900	'	17,900	'
Total expenses	37,056	21,589	86,861	40,492
Loss from operations	-37,056	-21,589	-86,861	-40,492
Interest income	5	25	10	59
Net loss	-37,051	-21,564	-86,851	-40,433
Net loss per share applicable to common stockholders - basic and diluted (in dollars per share)	($1.03)	($0.67)	($2.45)	($1.32)
Weighted-average number of common shares used in net loss per share applicable to common stockholders - basic and diluted (in shares)	35,982	32,336	35,422	30,577
Comprehensive loss	($37,051)	($21,564)	($86,851)	($40,433)

Condensed_Consolidated_Stateme1

Condensed Consolidated Statements of Cash Flows (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Operating activities	'	'
Net loss	($86,851)	($40,433)
Adjustments to reconcile net loss to net cash used in operating activities:	'	'
Acquired in-process research and development	17,900	'
Depreciation expense	158	84
Stock-based compensation expense	5,640	2,354
Loss on disposal of property and equipment	80	'
Changes in operating assets and liabilities:	'	'
Other assets	530	-711
Accounts payable	980	-1,206
Accrued expenses	6,015	1,432
Other liabilities	-16	19
Net cash used in operating activities	-55,564	-38,461
Investing activities	'	'
Acquisition of product candidate and technology licenses and milestone payments	-17,900	'
Purchase of property and equipment	-945	-369
Net cash used in investing activities	-18,845	-369
Financing activities	'	'
Proceeds from sale of common stock, net of issuance costs	94,199	91,312
Proceeds from exercise of stock options	868	99
Proceeds from issuance of common stock under Employee Stock Purchase Plan	120	65
Net cash provided by financing activities	95,187	91,476
Increase in cash and cash equivalents	20,778	52,646
Cash and cash equivalents at beginning of period	130,310	125,445
Cash and cash equivalents at end of period	$151,088	$178,091

Description_of_Business

Description of Business	6 Months Ended
	Jun. 30, 2014
Description of Business	'
Description of Business	'
	1.  Description of Business
	TESARO, Inc., or the Company or TESARO, was incorporated in Delaware on March 26, 2010 and commenced operations in May 2010.  Headquartered in Waltham, Massachusetts, TESARO is an oncology-focused biopharmaceutical company dedicated to improving the lives of cancer patients.  TESARO acquires, in-licenses and develops oncology product candidates and, if approved for marketing, intends to commercialize these products 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, operates in one segment and has never earned revenue from its activities.  The Company is subject to a number of risks, including dependence on key individuals, the need to develop commercially viable products, competition from other companies, many of whom are larger and better capitalized, and the need to obtain adequate additional financing to fund the development and potential commercialization of its product candidates and further its in-licensing and acquisition activities.
	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 the achievement of 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.

Basis_of_Presentation_and_Sign

Basis of Presentation and Significant Accounting Policies	6 Months Ended
	Jun. 30, 2014
Basis of Presentation and Significant Accounting Policies	'
Basis of Presentation and Significant Accounting Policies	'
	2.  Basis of Presentation and Significant Accounting Policies
	Basis of Presentation
	The accompanying condensed consolidated financial statements are unaudited and have been prepared by TESARO in conformity with accounting principles generally accepted in the United States of America, or GAAP.
	The condensed 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 intercompany balances and transactions have been eliminated in consolidation.  The Company currently operates in one business segment, 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.
	Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted.  These interim financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended June 30, 2013 and 2014.
	The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full fiscal year.  These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2013 and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
	New Accounting Pronouncements - Recently Adopted
	In June 2014, the FASB issued ASU No. 2014-10, which eliminates the concept of a development stage entity, or DSE, in its entirety from GAAP.  Under existing guidance, DSEs are required to report incremental information, including inception-to-date financial information, in their financial statements.  A DSE is an entity devoting substantially all of its efforts to establishing a new business and for which either planned principal operations have not yet commenced or have commenced but there has been no significant revenues generated from that business.  Entities classified as DSEs will no longer be subject to these incremental reporting requirements after adopting ASU No. 2014-10.  ASU No. 2014-10 is effective for fiscal years beginning after December 15, 2014, with early adoption permitted.  Retrospective application is required for the elimination of incremental DSE disclosures.  Prior to the issuance of ASU No. 2014-10, the Company had met the definition of a DSE since its inception.  The Company elected to adopt this ASU early, and therefore it has eliminated the incremental disclosures previously required of DSEs, starting with this Quarterly Report on Form 10-Q.
	New Accounting Pronouncements - Recently Issued
	In April 2014, the FASB issued ASU No. 2014-08, which amends guidance for reporting discontinued operations and disposals of components of an entity.  The amended guidance requires that a disposal representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results or a business activity classified as held for sale should be reported as discontinued operations.  The amendments also expand the disclosure requirements for discontinued operations and add new disclosure requirements for individually significant dispositions that do not qualify as discontinued operations.  This guidance is effective prospectively for fiscal years beginning after December 15, 2014 (early adoption is permitted only for disposals that have not been previously reported).  The Company does not expect the adoption of this guidance to have a material effect on its consolidated financial statements.
	In May 2014, the FASB issued ASU No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers.  This ASU supersedes the revenue recognition requirements in Accounting Standards Codification Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers.  This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted.  Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application.  The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its consolidated financial statements.
	Use of Estimates
	The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, expenses, other comprehensive income and the related disclosures.  On an ongoing basis, management evaluates its estimates, including estimates related to accrued research and development 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.
	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                    Observable inputs other than Level 1 inputs, including quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active
	Level 3 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 as of December 31, 2013 and June 30, 2014 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):
			December 31, 2013
	Description	Balance Sheet Classification	Total		Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	128,801	$	128,801	$	—	$	—
	Total assets		$	128,801	$	128,801	$	—	$	—
			June 30, 2014
	Description	Balance Sheet Classification	Total		Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	149,390	$	149,390	$	—	$	—
	Total assets		$	149,390	$	149,390	$	—	$	—
	The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term maturities.
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and include:
	·         license fees and milestone payments related to the acquisition of in-licensed products, which are reported on the statements of operations as acquired in-process research and development;
	·         employee-related expenses, including salaries, bonuses, benefits, travel and stock-based compensation expense;
	·         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, utilities, maintenance of facilities, insurance and other supplies; and
	·         other costs associated with clinical and 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 condensed consolidated balance sheets as prepaid or accrued research and development expenses.
	Acquired In-Process Research and Development Expense
	The Company has acquired the rights to develop and commercialize new product candidates.  Up-front payments that relate to the acquisition of a new drug compound, as well as milestone payments, are immediately expensed as acquired in-process research and development in the period in which they are incurred, provided that the new drug compound did not also include processes or activities that would constitute a “business”, as defined under GAAP, the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no alternative future use.
	Stock-Based Compensation Expense
	Stock-based compensation is recognized as expense for each stock-based award based on its estimated fair value.  The Company determines the fair value of each equity-based award at its grant date using the Black-Scholes option pricing model.  The value of the award that is ultimately expected to vest is recognized as expense on a straight-line basis over the requisite service period.  The cumulative effect of any changes to the estimated forfeiture rates are accounted for as an adjustment to expense in the period of the change.

Net_Loss_per_Share

Net Loss per Share	6 Months Ended
	Jun. 30, 2014
Net Loss per Share	'
Net Loss per Share	'
	3.  Net Loss per Share
	Basic and diluted net loss per common share is calculated by dividing net loss applicable to common stockholders by the weighted-average number of common shares outstanding during the period, without consideration of common stock equivalents.  The Company’s potentially dilutive shares, which include outstanding stock options 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, due to their anti-dilutive effect (in thousands):
		Three and Six Months Ended June 30,
		2013	2014
	Outstanding stock options	2,845	3,612
	Unvested restricted stock	226	22
		3,071	3,634

StockBased_Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2014
Stock-Based Compensation	'
Stock-Based Compensation	'
	4.  Stock-Based Compensation
	The Company maintains several equity compensation plans, including the 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.
	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 initially allowed 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 was an additional 6,857 shares) plus that number of shares of common stock related to awards outstanding under the 2010 Incentive Plan that terminate by expiration, forfeiture, cancellation, cash settlement or otherwise.  Each year starting with 2014, the number of shares available for grants of awards under the 2012 Incentive Plan will be increased automatically on January 1 by a number of shares of common stock equal to the lesser of 4% of the shares of common stock outstanding at such time or the number of shares determined by the Company’s board of directors.  Accordingly, effective January 1, 2014, 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.
	Prior to the approval of the 2012 Incentive Plan, the Company granted equity awards under the 2010 Incentive Plan.  As a result of the approval of the 2012 Incentive Plan, in April 2012 the Company ceased making awards under the 2010 Incentive Plan.  Any shares subject to outstanding awards granted under the 2010 Incentive Plan that remained available at that time or that expire or terminate for any reason prior to exercise have been added to the total number of shares available for issuance under the 2012 Incentive Plan.  Under the 2010 Incentive Plan, the Company was authorized to grant equity awards up to an aggregate of 1,981,130 shares of common stock.  The exercise price of each stock option granted has been equal to the closing price of a share of the Company’s common stock on the grant date or the fair value as determined by the board of directors on the grant date.
	Stock-based compensation expense as reflected in the Company’s condensed consolidated statements of operations and comprehensive loss was as follows (in thousands):
		Three Months Ended June 30,					Six Months Ended June 30,
		2013			2014		2013		2014
	Research and development	$	462		$	1,454	$	794	$	2,364
	General and administrative	1,122			1,648		1,560		3,276
	Total stock-based compensation expense	$	1,584		$	3,102	$	2,354	$	5,640
	The following table presents a summary of the Company’s restricted stock activity and related information:
				Weighted-average
				grant date fair
		Shares		value per share
	Unvested restricted stock at December 31, 2013	102,412		$	0.76
	Granted	—		—
	Vested	(71,118	)	0.15
	Forfeited	(8,929	)	0.53
	Unvested restricted stock at June 30, 2014	22,365		$	2.8
	The following table presents a summary of the Company’s stock option activity and related information:
		Shares		Weighted-average
				exercise price per
				share
	Outstanding at December 31, 2013	2,852,793		$	12.77
	Granted	1,051,123		30.92
	Exercised	(93,243	)	9.3
	Cancelled	(199,103	)	13.16
	Outstanding at June 30, 2014	3,611,570		$	18.12
	Vested at June 30, 2014	1,264,144		$	9.37
	Vested and expected to vest at June 30, 2014	3,526,361		$	17.84
	At June 30, 2014, there was approximately $30.9 million of total unrecognized compensation cost related to unvested stock options, which the Company expects to recognize over a remaining weighted-average period of 2.7 years.  At June 30, 2014, total unrecognized compensation cost related to unvested restricted stock was insignificant.
	Under the Company’s 2012 ESPP, an aggregate of 275,000 shares of common stock have been reserved for issuance pursuant to purchase rights granted to the Company’s employees or to employees of the Company’s designated subsidiaries.  During the six months ended June 30, 2014, the Company issued 5,372 shares under the 2012 ESPP, and recognized approximately $0.1 million in related stock-based compensation expense.

Common_Stock_Transactions

Common Stock Transactions	6 Months Ended
	Jun. 30, 2014
Common Stock Transactions	'
Common Stock Transactions	'
	5.  Common Stock Transactions
	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 $94.2 million.  The shares were issued pursuant to an automatic shelf registration statement on Form S-3.

Income_Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2014
Income Taxes	'
Income Taxes	'
	6.  Income Taxes
	Deferred tax assets and deferred tax liabilities are determined based on 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.  A valuation allowance is recorded against deferred tax assets if it is more likely than not that some portion or all of the deferred tax assets will not be realized.
	For the three and six months ended June 30, 2013 and 2014, the Company did not record any current or deferred income tax provisions or benefits.  Due to the uncertainty surrounding the future realization of the favorable tax attributes, the Company has recorded full valuation allowances against its otherwise recognizable net deferred tax assets at both December 31, 2013 and June 30, 2014.

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2014
Commitments and Contingencies	'
Commitments and Contingencies	'
	7.  Commitments and Contingencies
	In January 2014, the Company entered into an amendment of its existing office lease agreement whereby beginning in March 2014 it expanded the total leased space in the facility to approximately 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 $0.9 million 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 recognizes rental expense on a straight-line basis over the respective lease term.
	Future minimum rental commitments under the amended lease as of June 30, 2014 were $0.8 million, $1.7 million, $1.7 million and $0.8 million for the remainder of the year ending December 31, 2014, and the years ending December 31, 2015, 2016 and 2017, respectively.
	The Company has entered into agreements with certain vendors for the provision of services, including services related to data management, clinical operation support services, and certain contract manufacturing 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.
	The Company has certain obligations under licensing agreements with third parties that are contingent upon achieving various development, regulatory and commercial milestones.  Pursuant to these license agreements, the Company is required to make milestone payments if certain development, regulatory and commercial sales milestones are achieved, and may have certain additional research funding obligations.  Also, pursuant to the terms of each of these license agreements, when and if commercial sales of a product commence, the Company will pay royalties to its licensors on net sales of the respective products.
	Legal Proceedings
	The Company may periodically become subject to legal proceedings and claims arising in connection with on-going 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 does not have contingency reserves established for any litigation liabilities.

AnaptysBio_Collaboration_and_E

AnaptysBio Collaboration and Exclusive License Agreement	6 Months Ended
	Jun. 30, 2014
AnaptysBio Collaboration and Exclusive License Agreement	'
AnaptysBio Collaboration and Exclusive License Agreement	'
	8.  AnaptysBio Collaboration and Exclusive License Agreement
	Immuno-Oncology Platform License
	In March 2014, the Company entered into a collaboration and exclusive license agreement with AnaptysBio, Inc., or AnaptysBio, a privately-held therapeutic antibody company.  Under the terms of this agreement, the Company obtained an exclusive, royalty-bearing, 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.  Specifically, the Company received exclusive rights to monospecific antibody product candidates targeting TIM-3, LAG-3 and PD-1 (TSR-042) and dual-reactive antibody product candidates targeting PD-1/TIM-3 and PD-1/LAG-3.  Under the agreement, AnaptysBio is responsible for performing initial discovery and development of therapeutic antibodies, with the goal of generating immunotherapy antibodies for use in the treatment of cancer.  The Company is responsible for the performance and costs of all subsequent preclinical, clinical, regulatory, manufacturing and other activities necessary to develop and commercialize antibodies selected under each of three development programs and is obligated to use commercially reasonable efforts to research, develop or commercialize at least one product under each development program.
	Under the terms of the agreement, the Company made an up-front, non-creditable and non-refundable cash payment of $17.0 million to AnaptysBio in March 2014.  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 worldwide annual net sales, and additional commercial milestone payments if specified levels of annual net sales of a product are attained.
	As of the date of the license transaction, none of the assets acquired had alternative future uses, nor had they reached a stage of technological feasibility.  As the processes or activities that were acquired along with the license do not constitute a “business”, the transaction has been accounted for as an asset acquisition.  In addition, the Company has concluded that it is reimbursing AnaptysBio at fair value for the research services called for under the agreement.  As a result of these factors, the entire up-front payment of $17.0 million has been recorded as acquired in-process research and development expense, and no portion of the payment has been ascribed to the future services to be provided to the Company by AnaptysBio.  For the three and six months ended June 30, 2014, the Company recorded approximately $1.3 million and $1.5 million of research and development expense, respectively, associated with amounts due to AnaptysBio under the collaboration.  As of June 30, 2014, the Company has not made any additional milestone payments under this agreement.

Basis_of_Presentation_and_Sign1

Basis of Presentation and Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2014
Basis of Presentation and Significant Accounting Policies	'
Basis of Presentation	'
	Basis of Presentation
	The accompanying condensed consolidated financial statements are unaudited and have been prepared by TESARO in conformity with accounting principles generally accepted in the United States of America, or GAAP.
	The condensed 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 intercompany balances and transactions have been eliminated in consolidation.  The Company currently operates in one business segment, 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.
	Certain information and footnote disclosures normally included in the Company’s annual financial statements have been condensed or omitted.  These interim financial statements, in the opinion of management, reflect all normal recurring adjustments necessary for a fair presentation of the Company’s financial position and results of operations for the interim periods ended June 30, 2013 and 2014.
	The results of operations for the interim periods are not necessarily indicative of the results of operations to be expected for the full fiscal year.  These interim financial statements should be read in conjunction with the audited financial statements as of and for the year ended December 31, 2013 and the notes thereto, which are included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
New Accounting Pronouncements - Recently Adopted	'
	New Accounting Pronouncements - Recently Adopted
	In June 2014, the FASB issued ASU No. 2014-10, which eliminates the concept of a development stage entity, or DSE, in its entirety from GAAP.  Under existing guidance, DSEs are required to report incremental information, including inception-to-date financial information, in their financial statements.  A DSE is an entity devoting substantially all of its efforts to establishing a new business and for which either planned principal operations have not yet commenced or have commenced but there has been no significant revenues generated from that business.  Entities classified as DSEs will no longer be subject to these incremental reporting requirements after adopting ASU No. 2014-10.  ASU No. 2014-10 is effective for fiscal years beginning after December 15, 2014, with early adoption permitted.  Retrospective application is required for the elimination of incremental DSE disclosures.  Prior to the issuance of ASU No. 2014-10, the Company had met the definition of a DSE since its inception.  The Company elected to adopt this ASU early, and therefore it has eliminated the incremental disclosures previously required of DSEs, starting with this Quarterly Report on Form 10-Q.
New Accounting Pronouncements - Recently Issued	'
	New Accounting Pronouncements - Recently Issued
	In April 2014, the FASB issued ASU No. 2014-08, which amends guidance for reporting discontinued operations and disposals of components of an entity.  The amended guidance requires that a disposal representing a strategic shift that has (or will have) a major effect on an entity’s operations and financial results or a business activity classified as held for sale should be reported as discontinued operations.  The amendments also expand the disclosure requirements for discontinued operations and add new disclosure requirements for individually significant dispositions that do not qualify as discontinued operations.  This guidance is effective prospectively for fiscal years beginning after December 15, 2014 (early adoption is permitted only for disposals that have not been previously reported).  The Company does not expect the adoption of this guidance to have a material effect on its consolidated financial statements.
	In May 2014, the FASB issued ASU No. 2014-09, which amends the guidance for accounting for revenue from contracts with customers.  This ASU supersedes the revenue recognition requirements in Accounting Standards Codification Topic 605, Revenue Recognition, and creates a new Topic 606, Revenue from Contracts with Customers.  This guidance is effective for fiscal years beginning after December 15, 2016, with early adoption not permitted.  Two adoption methods are permitted: retrospectively to all prior reporting periods presented, with certain practical expedients permitted; or retrospectively with the cumulative effect of initially adopting the ASU recognized at the date of initial application.  The Company has not yet determined which adoption method it will utilize or the effect that the adoption of this guidance will have on its consolidated financial statements.
Use of Estimates	'
	Use of Estimates
	The preparation of condensed consolidated financial statements in conformity with GAAP requires management to make certain estimates and assumptions that affect the reported amounts of assets, liabilities, expenses, other comprehensive income and the related disclosures.  On an ongoing basis, management evaluates its estimates, including estimates related to accrued research and development 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.
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                    Observable inputs other than Level 1 inputs, including quoted prices in active markets for similar assets or liabilities and quoted prices for identical assets or liabilities in markets that are not active
	Level 3 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 as of December 31, 2013 and June 30, 2014 and indicates the fair value hierarchy of the valuation inputs utilized to determine such fair value (in thousands):
			December 31, 2013
	Description	Balance Sheet Classification	Total		Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	128,801	$	128,801	$	—	$	—
	Total assets		$	128,801	$	128,801	$	—	$	—
			June 30, 2014
	Description	Balance Sheet Classification	Total		Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	149,390	$	149,390	$	—	$	—
	Total assets		$	149,390	$	149,390	$	—	$	—
	The carrying amounts of accounts payable and accrued expenses approximate their fair values due to their short-term maturities.
Research and Development Expenses	'
	Research and Development Expenses
	Research and development costs are charged to expense as incurred and include:
	·         license fees and milestone payments related to the acquisition of in-licensed products, which are reported on the statements of operations as acquired in-process research and development;
	·         employee-related expenses, including salaries, bonuses, benefits, travel and stock-based compensation expense;
	·         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, utilities, maintenance of facilities, insurance and other supplies; and
	·         other costs associated with clinical and 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 condensed consolidated balance sheets as prepaid or accrued research and development expenses.
Acquired In-Process Research and Development Expense	'
	Acquired In-Process Research and Development Expense
	The Company has acquired the rights to develop and commercialize new product candidates.  Up-front payments that relate to the acquisition of a new drug compound, as well as milestone payments, are immediately expensed as acquired in-process research and development in the period in which they are incurred, provided that the new drug compound did not also include processes or activities that would constitute a “business”, as defined under GAAP, the drug has not achieved regulatory approval for marketing and, absent obtaining such approval, has no alternative future use.
Stock-Based Compensation Expense	'
	Stock-Based Compensation Expense
	Stock-based compensation is recognized as expense for each stock-based award based on its estimated fair value.  The Company determines the fair value of each equity-based award at its grant date using the Black-Scholes option pricing model.  The value of the award that is ultimately expected to vest is recognized as expense on a straight-line basis over the requisite service period.  The cumulative effect of any changes to the estimated forfeiture rates are accounted for as an adjustment to expense in the period of the change.

Basis_of_Presentation_and_Sign2

Basis of Presentation and Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2014
Basis of Presentation and 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):	'
			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	$	—	$	—
			June 30, 2014
	Description	Balance Sheet Classification	Total		Level 1		Level 2		Level 3
	Assets:
	Money market funds	Cash and cash equivalents	$	149,390	$	149,390	$	—	$	—
	Total assets		$	149,390	$	149,390	$	—	$	—

Net_Loss_per_Share_Tables

Net Loss per Share (Tables)	6 Months Ended
	Jun. 30, 2014
Net Loss per Share	'
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	'
		Three and Six Months Ended June 30,
		2013	2014
	Outstanding stock options	2,845	3,612
	Unvested restricted stock	226	22
		3,071	3,634

StockBased_Compensation_Tables

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2014
Stock-Based Compensation	'
Schedule of stock-based compensation expense as reflected in the Company's condensed consolidated statements of operations and comprehensive loss	'
		Three Months Ended June 30,					Six Months Ended June 30,
		2013			2014		2013		2014
	Research and development	$	462		$	1,454	$	794	$	2,364
	General and administrative	1,122			1,648		1,560		3,276
	Total stock-based compensation expense	$	1,584		$	3,102	$	2,354	$	5,640
Summary of the Company's restricted stock activity and related information	'
				Weighted-average
				grant date fair
		Shares		value per share
	Unvested restricted stock at December 31, 2013	102,412		$	0.76
	Granted	—		—
	Vested	(71,118	)	0.15
	Forfeited	(8,929	)	0.53
	Unvested restricted stock at June 30, 2014	22,365		$	2.8
Summary of the Company's stock option activity and related information	'
		Shares		Weighted-average
				exercise price per
				share
	Outstanding at December 31, 2013	2,852,793		$	12.77
	Granted	1,051,123		30.92
	Exercised	(93,243	)	9.3
	Cancelled	(199,103	)	13.16
	Outstanding at June 30, 2014	3,611,570		$	18.12
	Vested at June 30, 2014	1,264,144		$	9.37
	Vested and expected to vest at June 30, 2014	3,526,361		$	17.84

Description_of_Business_Detail

Description of Business (Details)	6 Months Ended
	Jun. 30, 2014
	segment
Description of Business	'
Number of operating segments	1

Basis_of_Presentation_and_Sign3

Basis of Presentation and Significant Accounting Policies (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014	Dec. 31, 2013
	item	Estimate Of Fair Value Fair Value Disclosure [Member]	Estimate Of Fair Value Fair Value Disclosure [Member]	Estimate Of Fair Value Fair Value Disclosure [Member]	Estimate Of Fair Value Fair Value Disclosure [Member]	Fair Value Inputs Level1 [Member]	Fair Value Inputs Level1 [Member]	Fair Value Inputs Level1 [Member]	Fair Value Inputs Level1 [Member]
	segment			Money Market Funds [Member]	Money Market Funds [Member]			Money Market Funds [Member]	Money Market Funds [Member]
Segment Information	'	'	'	'	'	'	'	'	'
Number of operating segments	1	'	'	'	'	'	'	'	'
Fair Value of Financial Instruments	'	'	'	'	'	'	'	'	'
Cash and cash equivalents	'	'	'	$149,390	$128,801	'	'	$149,390	$128,801
Assets	'	$149,390	$128,801	'	'	$149,390	$128,801	'	'
Acquired In-Process Research and Development Expense	'	'	'	'	'	'	'	'	'
Number of processes or activities obtained along with license	0	'	'	'	'	'	'	'	'

Net_Loss_per_Share_Details

Net Loss per Share (Details)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Net Loss per Share	'	'
Amounts excluded from the calculation of diluted net loss per share due to their anti-dilutive effect	3,634	3,071
Employee Stock Option [Member]	'	'
Net Loss per Share	'	'
Amounts excluded from the calculation of diluted net loss per share due to their anti-dilutive effect	3,612	2,845
Restricted Stock [Member]	'	'
Net Loss per Share	'	'
Amounts excluded from the calculation of diluted net loss per share due to their anti-dilutive effect	22	226

StockBased_Compensation_Detail

Stock-Based Compensation (Details) (Common Stock [Member])	0 Months Ended	6 Months Ended
	Jan. 02, 2014	Jun. 30, 2014	Apr. 27, 2012
Omnibus Incentive Plan2012 [Member]	'	'	'
Stock-Based Compensation	'	'	'
Number of shares available for grant under the plan	'	'	1,428,571
Number of shares available for future grants that were added to the total number of shares reserved for issuance	'	'	6,857
Number of additional shares authorized underthe plan	1,309,560	'	'
Annual increase in common stock available for grant as a percentage of common stock outstanding	'	4.00%	'
Stock Incentive Plan2010 [Member]	'	'	'
Stock-Based Compensation	'	'	'
Number of shares available for grant under the plan	'	1,981,130	'

StockBased_Compensation_Detail1

Stock-Based Compensation (Details 2) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock-based compensation expense	'	'	'	'
Total stock-based compensation expense	$3,102	$1,584	$5,640	$2,354
Research And Development Expense [Member]	'	'	'	'
Stock-based compensation expense	'	'	'	'
Total stock-based compensation expense	1,454	462	2,364	794
General And Administrative Expense [Member]	'	'	'	'
Stock-based compensation expense	'	'	'	'
Total stock-based compensation expense	$1,648	$1,122	$3,276	$1,560

StockBased_Compensation_Detail2

Stock-Based Compensation (Details 3) (USD $)	6 Months Ended
In Millions, except Share data, unless otherwise specified	Jun. 30, 2014
Restricted Stock [Member]	'
Shares	'
Unvested restricted at the beginning of the period (in shares)	102,412
Vested (in shares)	-71,118
Forfeited (in shares)	-8,929
Unvested restricted at the end of the period (in shares)	22,365
Weighted-average grant date fair value per share	'
Unvested restricted at the beginning of the period (in dollars per share)	$0.76
Vested (in dollars per share)	$0.15
Forfeited (in dollars per share)	$0.53
Unvested restricted at the end of the period (in dollars per share)	$2.80
Employee Stock Option [Member]	'
Shares	'
Outstanding at the beginning of the period (in shares)	2,852,793
Granted (in shares)	1,051,123
Exercised (in shares)	-93,243
Cancelled (in shares)	-199,103
Outstanding at the end of the period (in shares)	3,611,570
Vested at the end of the period (in shares)	1,264,144
Vested and expected to vest at the end of the period (in shares)	3,526,361
Weighted-average price per share	'
Outstanding at the beginning of the period (in dollars per share)	$12.77
Granted (in dollars per share)	$30.92
Exercised (in dollars per share)	$9.30
Cancelled (in dollars per share)	$13.16
Outstanding at the end of the period (in dollars per share)	$18.12
Vested at the end of the period (in dollars per share)	$9.37
Vested and expected to vest at the end of the period (in dollars per share)	$17.84
Additional disclosure	'
Total unrecognized compensation cost related to unvested stock options (in dollars)	$30.90
Weighted average period over which unrecognized compensation costs are expected to be recognized	'2 years 8 months 12 days

StockBased_Compensation_Detail3

Stock-Based Compensation (Details 4) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Stock-Based Compensation	'	'	'	'
Stock-based compensation expense	$3,102	$1,584	$5,640	$2,354
Employee Stock [Member]	'	'	'	'
Stock-Based Compensation	'	'	'	'
Common stock reserved for future issuance (in shares)	275,000	'	275,000	'
Shares issued	'	'	5,372	'
Stock-based compensation expense	'	'	$100	'

Common_Stock_Transactions_Deta

Common Stock Transactions (Details) (USD $)	1 Months Ended		6 Months Ended
	Feb. 28, 2014	Mar. 31, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Common Stock Transactions	'	'	'	'	'
Shares sold	3,200,000	5,428,000	'	'	'
Common stock, par value (in dollars per share)	$0.00	$0.00	$0.00	'	$0.00
Common stock issue price, in an underwritten public offering (in dollars per share)	$31.50	$18	'	'	'
Gross proceeds from the sale of common stock in an underwritten public offering	$100,800,000	$97,700,000	'	'	'
Net proceeds from the sale of common stock in an underwritten public offering	$94,200,000	$91,300,000	$94,199,000	$91,312,000	'

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (Amendment Of Operating Lease [Member], USD $)	1 Months Ended
In Millions, unless otherwise specified	Jan. 31, 2014	Jun. 30, 2014
	sqft
Amendment Of Operating Lease [Member]	'	'
Commitments and Contingencies	'	'
Leased office space (in square feet)	53,200	'
Additional rent expense	$0.90	'
Security deposit under amended lease	0.7	'
Future minimum rental commitments	'	'
Remainder of 2014	'	0.8
2015	'	1.7
2016	'	1.7
2017	'	$0.80

AnaptysBio_Collaboration_and_E1

AnaptysBio Collaboration and Exclusive License Agreement (Details) (USD $)	3 Months Ended		6 Months Ended		1 Months Ended	3 Months Ended		6 Months Ended	1 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Mar. 31, 2014	Jun. 30, 2014	Mar. 31, 2014	Jun. 30, 2014	Mar. 31, 2014
					Collaboration And Exclusive License Agreement [Member]	Collaboration And Exclusive License Agreement [Member]	Collaboration And Exclusive License Agreement [Member]	Collaboration And Exclusive License Agreement [Member]	Collaboration And Exclusive License Agreement [Member]
					Anaptys Bio Inc [Member]	Anaptys Bio Inc [Member]	Anaptys Bio Inc [Member]	Anaptys Bio Inc [Member]	Maximum [Member]
					item				Anaptys Bio Inc [Member]
AnaptysBio Collaboration and Exclusive License Agreement	'	'	'	'	'	'	'	'	'
Number of development programs	'	'	'	'	3	'	'	'	'
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	'	'	'	'	'	'	'	'	$18,000,000
Additional milestone payments required, if certain U.S. and non-U.S. regulatory submissions and approvals occur in multiple indications	'	'	'	'	'	'	'	'	90,000,000
Up-front payment recorded as acquired in-process research and development expense	'	'	17,900,000	'	17,000,000	'	17,000,000	'	'
Research and development expense	$30,569,000	$18,177,000	$58,686,000	$34,680,000	'	$1,300,000	'	$1,500,000	'