TESARO, Inc. [ ] Shares Common Stock ($0.0001 par value) Underwriting Agreement

Exhibit 1.1

TESARO, Inc.

[    ] Shares
Common Stock
($0.0001 par value)

Underwriting Agreement

New York, New York

[  ], 2012

Citigroup Global Markets Inc.

Morgan Stanley & Co. LLC

Leerink Swann LLC

As Representatives of the several Underwriters,

c/o Citigroup Global Markets Inc.

388 Greenwich Street

New York, New York 10013

c/o Morgan Stanley & Co. LLC

1585 Broadway

New York, New York 10036

c/o Leerink Swann LLC

One Federal Street, 37th Floor

Boston, MA 02110

Ladies and Gentlemen:

TESARO, Inc., a corporation organized under the laws of Delaware (the “Company”), proposes to sell to the several underwriters named in Schedule I hereto (the “Underwriters”), for whom you (the “Representatives”) are acting as representatives, [   ] shares of common stock, $0.0001 par value (“Common Stock”) of the Company (said shares to be issued and sold by the Company being hereinafter called the “Underwritten Securities”).  The Company also proposes to grant to the Underwriters an option to purchase up to [   ] additional shares of Common Stock to cover over-allotments, if any (the “Option Securities”; the Option Securities, together with the Underwritten Securities, being hereinafter called the “Securities”).  To the extent there are no additional Underwriters listed on Schedule I other than you, the term Representatives as used herein shall mean you, as Underwriters, and the terms Representatives and Underwriters shall mean either the singular or plural as the context requires.  Certain terms used herein are defined in Section 20 hereof.  As part of the offering contemplated by this Agreement, the Underwriters has agreed to reserve out of the Underwritten Securities set forth opposite their respective names on the Schedule II to this Agreement, up to [   ] shares, for sale to

the Company’s employees, officers, and directors and existing stockholders of the Company and other third parties designated by the Company (collectively, “Participants”), as set forth in the Prospectus under the heading “Underwriting” (the “Directed Shares”).  The Directed Shares to be sold pursuant to this Agreement will be sold by the Underwriters at the public offering price.  Any Directed Shares not orally confirmed for purchase by any Participants by 7:30 A.M. New York City time on the business day following the date on which this Agreement is executed will be offered to the public with the remaining Underwritten Securities.

1.                                       Representations and Warranties. The Company represents and warrants to, and agrees with, each Underwriter as set forth below in this Section 1.

(a)                                  The Company has prepared and filed with the Commission a registration statement (file number 333-180309) on Form S-1, including a related preliminary prospectus, for registration under the Act of the offering and sale of the Securities.  Such Registration Statement, including any amendments thereto filed prior to the Execution Time, has become effective.  The Company may have filed one or more amendments thereto, including a related preliminary prospectus, each of which has previously been furnished to you.  The Company will file with the Commission a final prospectus in accordance with Rule 424(b).  As filed, such final prospectus shall contain all information required by the Act and the rules thereunder and, except as otherwise required by law and after consultation with the Representatives, shall be in all substantive respects in the form furnished to you prior to the Execution Time or, to the extent not completed at the Execution Time, shall, except as otherwise required by law and after consultation with the Representatives, contain only such specific additional information and other changes (beyond that contained in the latest Preliminary Prospectus) as the Company has advised you, prior to the Execution Time, will be included or made therein.

(b)                                 On the Effective Date, the Registration Statement did, and when the Prospectus is first filed in accordance with Rule 424(b) and on the Closing Date (as defined herein) and on any date on which Option Securities are purchased, if such date is not the Closing Date (a “settlement date”), the Prospectus (and any supplement thereto) will, comply in all material respects with the applicable requirements of the Act and the rules thereunder; on the Effective Date and at the Execution Time, the Registration Statement did not and will not contain any untrue statement of a material fact or omit to state any material fact required to be stated therein or necessary in order to make the statements therein not misleading; and on the date of any filing pursuant to Rule 424(b) and on the Closing Date and any settlement date, the Prospectus (together with any supplement thereto) will not include any untrue statement of a material fact or omit to state a material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading; provided, however, that the Company makes no representations or warranties as to the information contained in or omitted from the Registration Statement, or the Prospectus (or any supplement thereto) in reliance upon and in conformity with information furnished in writing to the Company by or on behalf of any Underwriter through the Representatives specifically for inclusion in the Registration Statement or the Prospectus (or any supplement thereto), it being

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understood and agreed that the only such information furnished by any Underwriter consists of the information described as such in Section 8 hereof.

(c)                                  (i) The Disclosure Package and the price to the public, the number of Underwritten Securities, the number of Option Securities and the underwriting discount to be included on the cover page of the Prospectus, when taken together as a whole and (ii) each electronic road show when taken together as a whole with the Disclosure Package and the price to the public, the number of Underwritten Securities, the number of Option Securities and the underwriting discount to be included on the cover page of the Prospectus, does not contain any untrue statement of a material fact or omit to state any material fact necessary in order to make the statements therein, in the light of the circumstances under which they were made, not misleading.  The preceding sentence does not apply to statements in or omissions from the Disclosure Package based upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of any Underwriter consists of the information described as such in Section 8 hereof.

(d)                                 (i) At the time of filing the Registration Statement and (ii) as of the Execution Time (with such date being used as the determination date for purposes of this clause (ii)), the Company was not and is not an “ineligible issuer” (as defined in Rule 405), without taking account of any determination by the Commission pursuant to Rule 405 that it is not necessary that the Company be considered an “ineligible issuer.”

(e)                                  Each Issuer Free Writing Prospectus does not include any information that conflicts with the information contained in the Registration Statement on file at the time of issuance of such Issuer Free Writing Prospectus, including any document incorporated by reference therein that has not been superseded or modified.  The foregoing sentence does not apply to statements in or omissions from any Issuer Free Writing Prospectus based upon and in conformity with written information furnished to the Company by any Underwriter through the Representatives specifically for use therein, it being understood and agreed that the only such information furnished by or on behalf of any Underwriter consists of the information described as such in Section 8 hereof.

(f)                                    Each of the Company and the Subsidiary has been duly incorporated and is validly existing as a corporation in good standing under the laws of the jurisdiction in which it is chartered or organized with full corporate power and authority to own or lease, as the case may be, and to operate its properties and conduct its business as described in the Disclosure Package and the Prospectus, and is duly qualified to do business as a foreign corporation and is in good standing under the laws of each jurisdiction which requires such qualification, except where the failure to be so qualified or in good standing would not reasonably be expected, individually or in the aggregate, to have a material adverse effect on the condition (financial or otherwise), prospects, earnings, business or properties of the Company and the Subsidiary, taken as a whole, whether or not arising from transactions in the ordinary course of business (a “Material Adverse Effect”).

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(g)                                 As of the Execution Time, the Subsidiary does not have any material assets or liabilities and does not have any material operations.

(h)                                 All the outstanding shares of capital stock of the Subsidiary have been duly and validly authorized and issued and are fully paid and nonassessable, and, except as otherwise set forth in the Disclosure Package and the Prospectus, all outstanding shares of capital stock of the Subsidiary are directly owned by the Company free and clear of any perfected security interest or any other security interests, claims, liens or encumbrances.

(i)                                     There is no franchise, contract or other document of a character required to be described in the Registration Statement or Prospectus, or to be filed as an exhibit thereto, which is not described or filed as required (and the Preliminary Prospectus contains in all material respects the same description of the foregoing matters contained in the Prospectus); and the statements in the Preliminary Prospectus and the Prospectus under the headings “Risk Factors—Risks Related to Our Intellectual Property,” “Risk Factors—Risks Related to This Offering and Ownership of Our Common Stock—Some provisions of our charter documents and Delaware law may have anti-takeover effects that could discourage an acquisition of us by others, even if an acquisition would be beneficial to our stockholders and may prevent attempts by our stockholders to replace or remove our current management,” “Business—Patents and Proprietary Rights” and “Business—Government Regulation,” “Description of Capital Stock” and “Material U.S. Federal Income Tax Considerations,” insofar as such statements summarize legal matters, agreements, documents or proceedings discussed therein, are accurate and fair summaries of such legal matters, agreements, documents or proceedings.

(j)                                     This Agreement has been duly authorized, executed and delivered by the Company.

(k)                                  The Company is not and, after giving effect to the offering and sale of the Securities and the application of the proceeds thereof as described in the Disclosure Package and the Prospectus, will not be required to be registered as an “investment company” as defined in the Investment Company Act of 1940, as amended.

(l)                                     No consent, approval, authorization, filing with or order of any court or governmental agency or body is required in connection with the transactions contemplated herein, except such as have been obtained under the Act and such as may be required under the blue sky laws of any jurisdiction in connection with the purchase and distribution of the Securities by the Underwriters in the manner contemplated herein and in the Disclosure Package and the Prospectus.

(m)                               Neither the issue and sale of the Securities nor the consummation of any other of the transactions herein contemplated nor the fulfillment of the terms hereof will conflict with, result in a breach or violation of, or imposition of any lien, charge or encumbrance upon any property or assets of the Company or the Subsidiary pursuant to, (i) the charter or by-laws of the Company or the Subsidiary, (ii) the terms of any

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indenture, contract, lease, mortgage, deed of trust, note agreement, loan agreement or other agreement, obligation, condition, covenant or instrument to which the Company or the Subsidiary is a party or bound or to which its or their property is subject, or (iii) any statute, law, rule, regulation, judgment, order or decree applicable to the Company or the Subsidiary of any court, regulatory body, administrative agency, governmental body, arbitrator or other authority having jurisdiction over the Company or the Subsidiary or any of their respective properties, except in the case of clauses (ii) and (iii) as would not have a Material Adverse Effect or an adverse effect on the consummation of the transactions contemplated hereby.

(n)                                 No holders of securities of the Company have rights to the registration of such securities under the Registration Statement except for such rights of the Investors as have been waived.

(o)                                 The consolidated historical financial statements and schedules of the Company and its consolidated subsidiary included in the Preliminary Prospectus, the Prospectus and the Registration Statement present fairly in all material respects the financial condition, results of operations and cash flows of the Company as of the dates and for the periods indicated, comply as to form in all material respects with the applicable accounting requirements of the Act and have been prepared in conformity with generally accepted accounting principles in the United States applied on a consistent basis throughout the periods involved (except as otherwise noted therein).  The selected financial data set forth under the caption “Selected Financial Information” in the Preliminary Prospectus, the Prospectus and Registration Statement fairly present in all material respects, on the basis stated in the Preliminary Prospectus, the Prospectus and the Registration Statement, the information included therein.

(p)                                 No action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or the Subsidiary or their respective property is pending or, to the knowledge of the Company, threatened that (i) could reasonably be expected to have a material adverse effect on the performance of this Agreement or the consummation of any of the transactions contemplated hereby or (ii) could reasonably be expected to have a Material Adverse Effect.

(q)                                 Each of the Company and the Subsidiary owns or leases all such properties as are necessary to the conduct of its operations as presently conducted, except as would not reasonably be expected to have a Material Adverse Effect.

(r)                                    Neither the Company nor the Subsidiary is in violation or default of (i) any provision of its charter or bylaws, (ii) the terms of any indenture, contract, lease, mortgage, deed of trust, note agreement, loan agreement or other agreement, obligation, condition, covenant or instrument to which it is a party or bound or to which its property is subject, or (iii) any statute, law, rule, regulation, judgment, order or decree of any court, regulatory body, administrative agency, governmental body, arbitrator or other authority having jurisdiction over the Company or the Subsidiary or any of their respective properties, as applicable, except with respect to the Subsidiary (and its

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properties), and except with respect to the Company (and its properties) in the case of clauses (ii) and (iii), in each case as would not, individually or in the aggregate, have a Material Adverse Effect.

(s)                                  Ernst & Young LLP, who have certified certain financial statements of the Company and its consolidated subsidiary and delivered their report with respect to the audited consolidated financial statements and schedules included in the Disclosure Package and the Prospectus, are independent public accountants with respect to the Company within the meaning of the Act and the applicable published rules and regulations thereunder.

(t)                                    The Company has filed all tax returns that are required to be filed or has requested extensions thereof (except in any case in which the failure so to file would not have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto)) and has paid all taxes required to be paid by it and any other assessment, fine or penalty levied against it, to the extent that any of the foregoing is due and payable, except for any such assessment, fine or penalty that is currently being contested in good faith or as would not have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(u)                                 No labor problem or dispute with the employees of the Company or the Subsidiary exists or is threatened or, to the Company’s knowledge, imminent, and the Company is not aware of any existing or imminent labor disturbance by the employees of any of its or the Subsidiary’s principal suppliers, contractors or customers, that could have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(v)                                 The Company and the Subsidiary are insured by insurers of recognized financial responsibility against such losses and risks and in such amounts as are prudent and customary in the businesses in which they are engaged; all policies of insurance and fidelity or surety bonds insuring the Company or the Subsidiary or their respective businesses, assets, employees, officers and directors are in full force and effect; the Company and the Subsidiary are in compliance with the terms of such policies and instruments in all material respects; and there are no claims by the Company or the Subsidiary under any such policy or instrument as to which any insurance company is denying liability or defending under a reservation of rights clause; neither the Company nor the Subsidiary has been refused any insurance coverage sought or applied for; and neither the Company nor the Subsidiary has any reason to believe that it will not be able to renew its existing insurance coverage as and when such coverage expires or to obtain similar coverage from similar insurers as may be necessary to continue its business at a cost that would not have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(w)                               The Subsidiary is not currently prohibited, directly or indirectly, from paying any dividends to the Company, from making any other distribution on the

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Subsidiary’s capital stock, from repaying to the Company any loans or advances to the Subsidiary from the Company or from transferring any of the Subsidiary’s property or assets to the Company, except as described in or contemplated by the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(x)                                   The Company and the Subsidiary possess all licenses, certificates, permits and other authorizations issued by all applicable authorities necessary to conduct their respective businesses, except in each case, the lack of which would not reasonably be expected, individually or in the aggregate, to have a Material Adverse Effect, and neither the Company nor the Subsidiary has received any notice of proceedings relating to the revocation or modification of any such certificate, authorization or permit which, singly or in the aggregate, if the subject of an unfavorable decision, ruling or finding, would have a Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(y)                                 The Company maintains a consolidated system of internal accounting controls sufficient to provide reasonable assurance that (i) transactions are executed in accordance with management’s general or specific authorizations; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles and to maintain asset accountability; (iii) access to assets is permitted only in accordance with management’s general or specific authorization; and (iv) the recorded accountability for assets is compared with the existing assets at reasonable intervals and appropriate action is taken with respect to any differences.  The Company’s consolidated internal controls over financial reporting are effective and the Company and the Subsidiary are not aware of any material weakness in the Company’s consolidated internal controls over financial reporting.

(z)                                   The Company maintains consolidated “disclosure controls and procedures” (as such term is defined in Rule 13a-15(e) under the Exchange Act); such disclosure controls and procedures are effective.

(aa)                            The Company has not taken, directly or indirectly, any action designed to or that would constitute or that might reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

(bb)                          Except in each case as would not reasonably be expected, individually or in the aggregate, to have a Material Adverse Effect, the Company and the Subsidiary are (i) in compliance with any and all applicable foreign, federal, state and local laws and regulations relating to the protection of human health and safety, the environment or hazardous or toxic substances or wastes, pollutants or contaminants (“Environmental Laws”), (ii) have received and are in compliance with all permits, licenses or other approvals required of them under applicable Environmental Laws to conduct their respective businesses and (iii) have not received notice of any actual or potential liability under any environmental law, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).  Except as set forth in

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the Disclosure Package and the Prospectus, neither the Company nor the Subsidiary has been named as a “potentially responsible party” under the Comprehensive Environmental Response, Compensation, and Liability Act of 1980, as amended.

(cc)                            None of the following events has occurred or exists:  (i) a failure to fulfill the obligations, if any, under the minimum funding standards of Section 302 of the United States Employee Retirement Income Security Act of 1974, as amended (“ERISA”), and the regulations and published interpretations thereunder with respect to a Plan, determined without regard to any waiver of such obligations or extension of any amortization period; (ii) an audit or investigation by the Internal Revenue Service, the U.S. Department of Labor, the Pension Benefit Guaranty Corporation or any other federal or state governmental agency or any foreign regulatory agency with respect to the employment or compensation of employees by any of the Company or the Subsidiary that could have a Material Adverse Effect; (iii) any breach of any contractual obligation, or any violation of law or applicable qualification standards, with respect to the employment or compensation of employees by the Company or the Subsidiary that could have a Material Adverse Effect.  None of the following events has occurred or is reasonably likely to occur:  (i) a material increase in the aggregate amount of contributions required to be made to all Plans in the current fiscal year of the Company and the Subsidiary compared to the amount of such contributions made in the most recently completed fiscal year of the Company and the Subsidiary; (ii) a material increase in the “accumulated post-retirement benefit obligations” (within the meaning of Statement of Financial Accounting Standards 106) of the Company and the Subsidiary compared to the amount of such obligations in the most recently completed fiscal year of the Company and the Subsidiary; (iii) any event or condition giving rise to a liability under Title IV of ERISA that could have a Material Adverse Effect; or (iv) the filing of a claim by one or more employees or former employees of the Company or the Subsidiary related to their employment that could have a Material Adverse Effect.  For purposes of this paragraph, the term “Plan” means a plan (within the meaning of Section 3(3) of ERISA) subject to Title IV of ERISA with respect to which the Company or the Subsidiary may have any liability.

(dd)                          There is and has been no failure on the part of the Company and any of the Company’s directors or officers, in their capacities as such, to comply with any provision of the Sarbanes-Oxley Act of 2002 and the rules and regulations promulgated in connection therewith (the “Sarbanes-Oxley Act”), to the extent applicable to the Company, including Section 402 relating to loans.

(ee)                            Neither the Company nor the Subsidiary nor, to the knowledge of the Company, any director, officer, agent, employee or affiliate of the Company or the Subsidiary is aware of or has taken any action, directly or indirectly, that would result in a violation by such persons of the Foreign Corrupt Practices Act of 1977, as amended, and the rules and regulations thereunder (the “FCPA”), including, without limitation, making use of the mails or any means or instrumentality of interstate commerce corruptly in furtherance of an offer, payment, promise to pay or authorization of the payment of any money, or other property, gift, promise to give, or authorization of the giving of

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anything of value to any “foreign official” (as such term is defined in the FCPA) or any foreign political party or official thereof or any candidate for foreign political office, in contravention of the FCPA; and the Company, the Subsidiary and, to the knowledge of the Company, its affiliates have conducted their businesses in compliance with the FCPA and have instituted and maintain policies and procedures designed to ensure, and which are reasonably expected to continue to ensure, continued compliance therewith.

(ff)                                The operations of the Company and the Subsidiary are and have been conducted at all times in compliance with applicable financial recordkeeping and reporting requirements and the money laundering statutes of jurisdictions where the Company or the Subsidiary conduct business and the rules and regulations thereunder and any related or similar rules, regulations or guidelines, issued, administered or enforced by any governmental agency (collectively, the “Money Laundering Laws”) and no action, suit or proceeding by or before any court or governmental agency, authority or body or any arbitrator involving the Company or the Subsidiary with respect to the Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(gg)                          Neither the Company nor the Subsidiary nor, to the knowledge of the Company, any director, officer, agent, employee or affiliate of the Company or the Subsidiary is currently subject to any sanctions administered by the Office of Foreign Assets Control of the U.S. Treasury Department (“OFAC”); and the Company will not directly or indirectly use the proceeds of the offering, or lend, contribute or otherwise make available such proceeds to the Subsidiary or any joint venture partner or other person or entity, for the purpose of financing the activities of any person currently subject to any U.S. sanctions administered by OFAC.

(hh)                          The Company and the Subsidiary own, possess, have a license to or have other rights to use, all patents, patent applications, trade and service marks, trade and service mark registrations, trade names, copyrights, licenses, domain names, inventions, trade secrets, technology, know-how and other intellectual property, including registrations and applications for registration thereof (collectively, the “Intellectual Property”) necessary for the conduct of the Company’s business as now conducted or as proposed in the Prospectus to be conducted, except as would not reasonably be expected to have a Material Adverse Effect.  Except as set forth in the Preliminary Prospectus and the Prospectus under the caption “Business—Patents and Proprietary Rights,” (a) there are no rights of third parties to any such Intellectual Property that conflict with the Company’s rights thereto and/or ability to practice thereunder; (b) to the Company’s knowledge, there is no material infringement, misappropriation or other violation by third parties of any such Intellectual Property; (c) there is no pending or, to the Company’s knowledge, threatened action, suit, proceeding or claim by others challenging the Company’s rights in or to any such Intellectual Property, and the Company is unaware of any facts which would form a reasonable basis for any such claim; (d) the issued patents, and the registered trade marks, service marks and trade names included in the Intellectual Property owned by the Company and, to the Company’s knowledge, licensed to the Company, have not been adjudged invalid or unenforceable in whole or in part, and there is no pending or, to the knowledge of the Company, threatened action, suit, proceeding or

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claim by others challenging the validity or scope of any such Intellectual Property, and the Company is unaware of any facts which would form a reasonable basis for any such claim; (e) there is no pending or , to the Company’s best knowledge, threatened action, suit, proceeding or claim by others that the Company infringes or otherwise misappropriates or violates any patent, trademark, copyright, trade secret or other proprietary rights of others, and the Company is unaware of any facts which would form a reasonable basis for any such claim; (f) to the Company’s knowledge, there is no U.S. patent or published U.S. patent application which contains claims that dominate or may dominate any Intellectual Property described in the Disclosure Package and the Prospectus as being owned by or licensed to the Company or that interferes with the issued or pending claims of any such Intellectual Property; (g) there is no prior art of which the Company is currently aware that may render any U.S. patent held or licensed by the Company invalid or any U.S. patent application held or licensed by the Company unpatentable which has not been disclosed to the U.S. Patent and Trademark Office; (h) to the Company’s knowledge, none of the Intellectual Property used by the Company in its business has been obtained or is being used by the Company in violation of any contractual obligation binding on the Company or in violation of the rights of any third parties; and (i) the Company is not aware of any facts that it believes would form a reasonable basis for a successful challenge that any of its employees are in or have ever been in violation of any term of any employment contract, patent disclosure agreement, invention assignment agreement, non-competition agreement, non-solicitation agreement, nondisclosure agreement or any restrictive covenant to or with a former employer where such violation relates to such employee’s breach of a confidentiality obligation, obligation to assign to the company Intellectual Property, or obligation not to use third party Intellectual Property or other proprietary rights in each case, on behalf of or for the benefit of the Company; and (j) the Company is not a party to or bound by any options, licenses or other agreements with respect to the Company’s or any third party’s Intellectual Property that are required to be set forth on the Prospectus, but are not described in all material respects in the Prospectus.

(ii)                                  Except as described in the Registration Statement, the Disclosure Package and the Prospectus, the Company: (A) is and at all times has been in material compliance with all statutes, rules or regulations applicable to the ownership, testing, development, manufacture, packaging, processing, use, distribution, marketing, labeling, promotion, sale, offer for sale, storage, import, export or disposal of any product that is under development, manufactured or distributed by the Company (“Applicable Laws”); (B) has not received any Form FDA 483, notice of adverse finding, warning letter, untitled letter or other correspondence or notice from the U.S. Food and Drug Administration (the “FDA”) or any other federal, state, local or foreign governmental or regulatory authority alleging or asserting material noncompliance with any Applicable Laws or any licenses, certificates, approvals, clearances, authorizations, permits and supplements or amendments thereto required by any such Applicable Laws (“Authorizations”) that would, individually or in the aggregate, result in a Material Adverse Effect; (C) possesses all material Authorizations necessary for the operation of its business as described in the Registration Statement and such Authorizations are valid and in full force and effect and the Company is not in material violation of any term of any such Authorizations; (D) has

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not received notice of any claim, action, suit, proceeding, hearing, enforcement, investigation, arbitration or other action from the FDA or any other federal, state, local or foreign governmental or regulatory authority or third party alleging that any product, operation or activity is in material violation of any Applicable Laws or Authorizations, and has no knowledge that the FDA or any other federal, state, local or foreign governmental or regulatory authority or third party is considering any such claim, litigation, arbitration, action, suit, investigation or proceeding; (E) has not received notice that the FDA or any other federal, state, local or foreign governmental or regulatory authority has taken, is taking or intends to take action to limit, suspend, modify or revoke any material Authorizations and has no knowledge that the FDA or any other federal, state, local or foreign governmental or regulatory authority is considering such action; (F) has filed, obtained, maintained or submitted all material reports, documents, forms, notices, applications, records, claims, submissions and supplements or amendments as required by any Applicable Laws or Authorizations and that all such reports, documents, forms, notices, applications, records, claims, submissions and supplements or amendments were materially complete and correct on the date filed (or were corrected or supplemented by a subsequent submission); and (G) has not, either voluntarily or involuntarily, initiated, conducted, or issued or caused to be initiated, conducted or issued, any recall, market withdrawal or replacement, safety alert, post sale warning, “dear doctor” letter, or other notice or action relating to the alleged lack of safety or efficacy of any product or any alleged product defect or violation and, to the Company’s knowledge, no third party has initiated, conducted or intends to initiate any such notice or action.

(jj)                                  The studies, tests and preclinical and clinical trials conducted by or on behalf of the Company were and, if still ongoing, are being conducted in all material respects in accordance with experimental protocols, procedures and controls pursuant to accepted professional scientific standards and all Applicable Laws and Authorizations, including, without limitation, the Federal Food, Drug, and Cosmetic Act and the rules and regulations promulgated thereunder (collectively, “FFDCA”); the descriptions of the results of such studies, tests and trials contained in the Registration Statement, the Disclosure Package and the Prospectus are accurate and complete in all material respects and fairly present the data derived from such studies, tests and trials; except to the extent disclosed in the Registration Statement, the Disclosure Package and the Prospectus, the Company is not aware of any studies, tests or trials, the results of which the Company believes reasonably call into question the study, test, or trial results described or referred to in the Registration Statement, the Disclosure Package and the Prospectus when viewed in the context in which such results are described and the clinical state of development; and, except to the extent disclosed in the Registration Statement, the Disclosure Package or the Prospectus, the Company has not received any notices or correspondence from the FDA or any other federal, state, local or foreign governmental or regulatory authority requiring the termination, suspension or material modification of any studies, tests or preclinical or clinical trials conducted by or on behalf of the Company.

(kk)                            As used in this subsection:

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“Governmental Entity” means any national, federal, state, county, municipal, local or foreign government, or any political subdivision, court, body, agency or regulatory authority thereof, and any Person exercising executive, legislative, judicial, regulatory, taxing or administrative functions of or pertaining to any of the foregoing.

“Law” means any federal, state, local, national or foreign law, statute, code, ordinance, rule, regulation, order, judgment, writ, stipulation, award, injunction, decree or arbitration award or finding.

(i)                                     The Company has not committed any act, made any statement or failed to make any statement that would reasonably be expected to provide a basis for the FDA or any other Governmental Entity to invoke its policy with respect to “Fraud, Untrue Statements of Material Facts, Bribery, and Illegal Gratuities”, or similar policies, set forth in any applicable Laws. Neither the Company, nor, to the knowledge of the Company, any of its officers, key employees or agents has been convicted of any crime or engaged in any conduct that has resulted, or would reasonably be expected to result, in debarment under applicable Law, including, without limitation, 21 U.S.C. Section 335a. No claims, actions, proceedings or investigations that would reasonably be expected to result in such a material debarment or exclusion are pending, or to the knowledge of the Company, threatened, against the Company or any of its respective officers, employees or agents.

(ii)                                  Each of the Company and its directors, officers, employees, and agents (in each case, while acting in such capacity) is, and at all times has been, in material compliance with all health care Laws applicable to the Company or by which any of its properties, businesses, products or other assets is bound or affected, including, without limitation, the federal Anti-kickback Statute (42 U.S.C. § 1320a-7b(b)), the Anti-Inducement Law (42 U.S.C. § 1320a-7a(a)(5)), the civil False Claims Act (31 U.S.C. §§ 3729 et seq.), the administrative False Claims Law (42 U.S.C. § 1320a-7b(a)), the Health Insurance Portability and Accountability Act of 1996 (42 U.S.C. § 1320d et seq.), the exclusion laws (42 U.S.C. § 1320a-7), the Food Drug and Cosmetic Act (21 U.S.C. §§ 301 et seq.) (collectively, “Health Care Laws”). The Company has not received any notification, correspondence or any other written or oral communication from any Governmental Entity, including, without limitation, the FDA, the Centers for Medicare and Medicaid Services, and the Department of Health and Human Services Office of Inspector General, of potential or actual material non-compliance by, or liability of, the Company under any Health Care Laws.

(iii)                               The Company is not a party to any corporate integrity agreements, monitoring agreements, consent decrees, settlement orders, or similar agreements with or imposed by any Governmental Entity.

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(ll)                                  From the time of initial confidential submission of the Registration Statement to the Commission (or, if earlier, the first date on which the Company engaged directly or through any Person authorized to act on its behalf in any communication in reliance on Section 5(d) of the Act) through the date hereof, the Company has been and is an “emerging growth company,” as defined in Section 2(a) of the Act (an “Emerging Growth Company”).

(mm)                      The Company (i) has not engaged in communications with potential investors in reliance on Section 5(d) of the Act except in consultation with the Representatives and in accordance with any written guidelines provided by the Representatives and (ii) has not authorized anyone other than the Underwriters to engage in such communications.  The Company reconfirms that the Underwriters have been authorized to act on its behalf in communicating with specified potential investors in reliance on Section 5(d) of the Act.  The Company has not used or distributed any Testing-the-Waters Writings.

(nn)                          The Company solely determined, without any direct or indirect participation by the Underwriters, the Participants who will purchase Directed Shares (including the amounts to be purchased by such persons) sold in the offering contemplated by this Agreement by the Underwriters.

(oo)                          The Registration Statement, the Prospectus, any preliminary prospectus and any Issuer Free Writing Prospectuses comply in all material respects, and any further amendments or supplements thereto will comply in all material respects, with any applicable laws or regulations of foreign jurisdictions in which the Prospectus or any preliminary prospectus and any Issuer Free Writing Prospectus, as amended or supplemented, if applicable, are distributed in connection with the sale of the Directed Shares, and no authorization, approval, consent, license, order, registration or qualification of or with any government, governmental instrumentality or court, other than such as have been obtained, is necessary under the securities laws and regulations of foreign jurisdictions in which the Directed Shares are offered outside the United States.  The Company has not offered, or caused the Underwriters to offer, Securities with the specific intent to unlawfully influence (i) a customer or supplier of the Company to alter the customer’s or supplier’s level or type of business with the Company, or (ii) a trade journalist or publication to write or publish favorable information about the Company or its products.

Any certificate signed by any officer of the Company and delivered to the Representatives or counsel for the Underwriters in connection with the offering of the Securities shall be deemed a representation and warranty by the Company, as to matters covered thereby, to each Underwriter.

2.                                       Purchase and Sale.  (a)  Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company agrees to sell to each Underwriter, and each Underwriter agrees, severally and not jointly, to purchase

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from the Company, at a purchase price of $[   ] per share, the amount of the Underwritten Securities set forth opposite such Underwriter’s name in Schedule I hereto.

(b)                                 Subject to the terms and conditions and in reliance upon the representations and warranties herein set forth, the Company hereby grants an option to the several Underwriters to purchase, severally and not jointly, up to [   ] Option Securities at the same purchase price per share as the Underwriters shall pay for the Underwritten Securities, less an amount per share equal to any dividends or distributions declared by the Company and payable on the Underwritten Securities but not payable on the Option Securities.  Said option may be exercised only to cover over-allotments in the sale of the Underwritten Securities by the Underwriters.  Said option may be exercised in whole or in part at any time on or before the 30th day after the date of the Prospectus upon written or telegraphic notice by the Representatives to the Company setting forth the number of shares of the Option Securities as to which the several Underwriters are exercising the option and the settlement date.  The number of Option Securities to be purchased by each Underwriter shall be the same percentage of the total number of shares of the Option Securities to be purchased by the several Underwriters as such Underwriter is purchasing of the Underwritten Securities, subject to such adjustments as you in your absolute discretion shall make to eliminate any fractional shares.

3.                                       Delivery and Payment.  Delivery of and payment for the Underwritten Securities and the Option Securities (if the option provided for in Section 2(b) hereof shall have been exercised on or before the third Business Day immediately preceding the Closing Date) shall be made at 10:00 AM, New York City time, on [   ], 2012, or at such time on such later date not more than three Business Days after the foregoing date as the Representatives shall designate, which date and time may be postponed by agreement between the Representatives and the Company or as provided in Section 9 hereof (such date and time of delivery and payment for the Securities being herein called the “Closing Date”).  Delivery of the Securities shall be made to the Representatives for the respective accounts of the several Underwriters against payment by the several Underwriters through the Representatives of the purchase price thereof to or upon the order of the Company by wire transfer payable in same-day funds to an account specified by the Company.  Delivery of the Underwritten Securities and the Option Securities shall be made through the facilities of The Depository Trust Company unless the Representatives shall otherwise instruct.

If the option provided for in Section 2(b) hereof is exercised after the third Business Day immediately preceding the Closing Date, the Company will deliver the Option Securities (at the expense of the Company) to the Representatives, at 388 Greenwich Street, New York, New York, on the date specified by the Representatives (which shall be within three Business Days after exercise of said option) for the respective accounts of the several Underwriters, against payment by the several Underwriters through the Representatives of the purchase price thereof to or upon the order of the Company by wire transfer payable in same-day funds to an account specified by the Company.  If settlement for the Option Securities occurs after the Closing Date, the Company will deliver to the Representatives on the settlement date for the Option Securities, and the obligation of the Underwriters to purchase the Option Securities shall be conditioned upon receipt of, supplemental opinions, certificates and letters confirming as

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of such date the opinions, certificates and letters delivered on the Closing Date pursuant to Section 6 hereof.

4.                                       Offering by Underwriters.  It is understood that the several Underwriters propose to offer the Securities for sale to the public as set forth in the Prospectus.

5.                                       Agreements.  The Company agrees with the several Underwriters that:

(a)                                  Prior to the termination of the offering of the Securities, the Company will not file any amendment of the Registration Statement or supplement to the Prospectus or any Rule 462(b) Registration Statement unless the Company has furnished you and your counsel a copy for review prior to filing and will not file any such proposed amendment or supplement to which you reasonably object. The Company will cause the Prospectus, properly completed, and any supplement thereto to be filed in a form approved by the Representatives with the Commission pursuant to the applicable paragraph of Rule 424(b) within the time period prescribed and will provide evidence satisfactory to the Representatives of such timely filing.  The Company will promptly advise the Representatives (i) when the Prospectus, and any supplement thereto, shall have been filed (if required) with the Commission pursuant to Rule 424(b) or when any Rule 462(b) Registration Statement shall have been filed with the Commission, (ii) when, prior to termination of the offering of the Securities, any amendment to the Registration Statement shall have been filed or become effective, (iii) of any request by the Commission or its staff for any amendment of the Registration Statement, or any Rule 462(b) Registration Statement, or for any supplement to the Prospectus or for any additional information, (iv) of the issuance by the Commission of any stop order suspending the effectiveness of the Registration Statement or of any notice objecting to its use or the institution or threatening of any proceeding for that purpose and (v) of the receipt by the Company of any notification with respect to the suspension of the qualification of the Securities for sale in any jurisdiction or the institution or threatening of any proceeding for such purpose.  The Company will use its reasonable best efforts to prevent the issuance of any such stop order or the occurrence of any such suspension or objection to the use of the Registration Statement and, upon such issuance, occurrence or notice of objection, to obtain as soon as possible the withdrawal of such stop order or relief from such occurrence or objection, including, if necessary, by filing an amendment to the Registration Statement or a new registration statement and using its reasonable best efforts to have such amendment or new registration statement declared effective as soon as practicable.

(b)                                 If, at any time prior to the filing of the Prospectus pursuant to Rule 424(b), any event occurs as a result of which the Disclosure Package would include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made not misleading, the Company will (i) notify promptly the Representatives so that any use of the Disclosure Package may cease until it is amended or supplemented; (ii) amend or supplement the Disclosure Package to correct such statement or omission; and (iii) supply any amendment or supplement to you in such quantities as you may reasonably request.

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(c)                                  If, at any time when a prospectus relating to the Securities is required to be delivered under the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), any event occurs as a result of which the Prospectus as then supplemented would include any untrue statement of a material fact or omit to state any material fact necessary to make the statements therein in the light of the circumstances under which they were made not misleading, or if it shall be necessary to amend the Registration Statement or supplement the Prospectus to comply with the Act or the rules thereunder, the Company promptly will (i) notify the Representatives of any such event; (ii) prepare and file with the Commission, subject to the second sentence of paragraph (a) of this Section 5, an amendment or supplement which will correct such statement or omission or effect such compliance; and (iii) supply any supplemented Prospectus to you in such quantities as you may reasonably request.

(d)                                 As soon as practicable, the Company will make generally available to its security holders and to the Representatives an earnings statement or statements of the Company and the Subsidiary which will satisfy the provisions of Section 11(a) of the Act and Rule 158.

(e)                                  The Company will furnish to each of the Representatives and counsel for the Underwriters, without charge, a signed copy of the Registration Statement (including exhibits thereto) and to each other Underwriter a conformed copy of the Registration Statement (without exhibits thereto) and, so long as delivery of a prospectus by an Underwriter or dealer may be required by the Act (including in circumstances where such requirement may be satisfied pursuant to Rule 172), as many copies of the Preliminary Prospectus, the Prospectus and each Issuer Free Writing Prospectus and any supplement thereto as the Representatives may reasonably request.  The Company will pay the expenses of printing or other production of all documents relating to the offering.

(f)                                    The Company will use its reasonable best efforts to arrange, with the cooperation of the Underwriters, if necessary, for the qualification of the Securities for sale under the laws of such jurisdictions as the Representatives may reasonably designate after consultation with the Company and will use its reasonable best efforts to maintain such qualifications in effect so long as required for the distribution of the Securities; provided that in no event shall the Company be obligated to qualify to do business in any jurisdiction where it is not now so qualified or to take any action that would subject it to service of process in suits, other than those arising out of the offering or sale of the Securities, or subject it to taxation, in any jurisdiction where it is not now so subject.

(g)                                 The Company will not, without the prior written consent of Citigroup Global Markets Inc., Morgan Stanley & Co. LLC and Leerink Swann LLC, offer, sell, contract to sell, pledge, or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition or effective economic disposition due to cash settlement or otherwise) by the Company or any affiliate of the Company or any person in privity with the Company or any affiliate of the Company) directly or indirectly, including the filing (or participation in the filing) of a registration statement with the Commission in respect of,

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or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Exchange Act, any other shares of Common Stock or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock; or publicly announce an intention to effect any such transaction, for a period of 180 days after the date of the Underwriting Agreement, provided, however, that the Company may (i) issue and sell Common Stock, or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock, pursuant to any employee stock option plan, incentive plan, stock ownership plan or dividend reinvestment plan of the Company in effect at the Execution Time or disclosed in the Prospectus, (ii) issue Common Stock issuable upon the conversion of securities outstanding at the Execution Time, (iii) file one or more registration statements on Form S-8 or (iv) offer, issue and sell shares of Common Stock or any securities convertible into, or exercisable, or exchangeable for, shares of Common Stock in connection with any acquisition or strategic investment (including any joint venture, strategic alliance or partnership) as long as (x) the aggregate number of shares of Common Stock issued or issuable does not exceed 10% of the number of shares of Common Stock outstanding immediately after the issuance and sale of the Securities, and (y) each recipient of any such shares or other securities agrees to restrictions on the resale of securities that are consistent with the lock-up letters described in Section 6(j) hereof for the remainder of the 180-day restricted period, as extended pursuant to the next sentence if applicable.  Notwithstanding the foregoing, if (x) during the last 17 days of the 180-day restricted period the Company issues an earnings release or material news or a material event relating to the Company occurs, or (y) prior to the expiration of the 180-day restricted period, the Company announces that it will release earnings results during the 16-day period beginning on the last day of the 180-day period, the restrictions imposed in this clause shall continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event.  The Company will provide the Representatives and any co-managers and each individual subject to the restricted period pursuant to the lock-up letters described in Section 6(j) hereof with prior notice of any such announcement that gives rise to an extension of the restricted period.

(h)                                 If Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC, in their sole discretion, agree to release or waive the restrictions set forth in a lock-up letter described in Section 6(j) hereof for an officer or director of the Company and provide the Company with notice of the impending release or waiver at least three Business Days before the effective date of the release or waiver, the Company agrees to announce the impending release or waiver by a press release substantially in the form of Exhibit B hereto through a major news service at least two Business Days before the effective date of the release or waiver.

(i)                                     The Company will not take, directly or indirectly, any action designed to or that would constitute or that would reasonably be expected to cause or result in, under the Exchange Act or otherwise, stabilization or manipulation of the price of any security of the Company to facilitate the sale or resale of the Securities.

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(j)                                     The Company agrees to pay the costs and expenses relating to the following matters:  (i) the preparation, printing or reproduction and filing with the Commission of the Registration Statement (including financial statements and exhibits thereto), each Preliminary Prospectus, the Prospectus and each Issuer Free Writing Prospectus, and each amendment or supplement to any of them; (ii) the printing (or reproduction) and delivery (including postage, air freight charges and charges for counting and packaging) of such copies of the Registration Statement, each Preliminary Prospectus, the Prospectus and each Issuer Free Writing Prospectus, and all amendments or supplements to any of them, as may, in each case, be reasonably requested for use in connection with the offering and sale of the Securities; (iii) the preparation, printing, authentication, issuance and delivery of certificates for the Securities, including any stamp or transfer taxes in connection with the original issuance and sale of the Securities; (iv) the printing (or reproduction) and delivery of this Agreement, any blue sky memorandum and all other agreements or documents printed (or reproduced) and delivered in connection with the offering of the Securities; (v) the registration of the Securities under the Exchange Act and the listing of the Securities on the Nasdaq Global Market; (vi) any registration or qualification of the Securities for offer and sale under the securities or blue sky laws of the several states (including filing fees and the reasonable fees and expenses of counsel for the Underwriters relating to such registration and qualification); (vii) any filings required to be made with the Financial Industry Regulatory Authority, Inc. (including filing fees and the reasonable fees and expenses of counsel for the Underwriters relating to such filings); provided that the reasonable fees and expenses of counsel for the Underwriters relating to subclause (vi) and (vii) of this Section 5(j) shall not exceed $30,000; (viii) the transportation and other expenses incurred by or on behalf of Company representatives in connection with presentations to prospective purchasers of the Securities; provided, however, that the Company shall be responsible for half of the cost and expenses of any aircraft chartered in connection with the “road show” for the Securities and the Underwriters shall be responsible for the balance; (ix) the fees and expenses of the Company’s accountants and the fees and expenses of counsel (including local and special counsel) for the Company; and (x) all other costs and expenses incident to the performance by the Company of its obligations hereunder.

(k)                                  The Company agrees that, unless it has or shall have obtained the prior written consent of the Representatives, and each Underwriter, severally and not jointly, agrees with the Company that, unless it has or shall have obtained, as the case may be, the prior written consent of the Company, it has not made and will not make any offer relating to the Securities that would constitute an Issuer Free Writing Prospectus or that would otherwise constitute a Free Writing Prospectus required to be filed by the Company with the Commission or retained by the Company under Rule 433; provided that the prior written consent of the parties hereto shall be deemed to have been given in respect of the Free Writing Prospectuses included in Schedule II hereto.  Any such free writing prospectus consented to by the Representatives or the Company is hereinafter referred to as a “Permitted Free Writing Prospectus.”  The Company agrees that (x) it has treated and will treat, as the case may be, each Permitted Free Writing Prospectus as an Issuer Free Writing Prospectus and (y) it has complied and will comply, as the case may

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be, with the requirements of Rules 164 and 433 applicable to any Permitted Free Writing Prospectus, including in respect of timely filing with the Commission, legending and record keeping.

(l)                                     The Company will promptly notify the Representatives if the Company ceases to be an Emerging Growth Company at any time prior to the later of (i) completion of the distribution of the Securities within the meaning of the Act and (ii) completion of the 180-day restricted period referred to in Section 5(g) hereof.

(m)                               The Company will comply with all applicable securities and other applicable laws, rules and regulations in each foreign jurisdiction in which the Directed Shares are offered in connection with the sale of the Directed Shares.

6.                                       Conditions to the Obligations of the Underwriters.  The obligations of the Underwriters to purchase the Underwritten Securities and the Option Securities, as the case may be, shall be subject to the accuracy of the representations and warranties on the part of the Company contained herein as of the Execution Time, the Closing Date and any settlement date pursuant to Section 3 hereof, to the accuracy of the statements of the Company made in any certificates pursuant to the provisions hereof, to the performance by the Company of its obligations hereunder and to the following additional conditions:

(a)                                  The Prospectus, and any supplement thereto, have been filed in the manner and within the time period required by Rule 424(b); any material required to be filed by the Company pursuant to Rule 433(d) under the Act shall have been filed with the Commission within the applicable time periods prescribed for such filings by Rule 433; and no stop order suspending the effectiveness of the Registration Statement or any notice objecting to its use shall have been issued and no proceedings for that purpose shall have been instituted or threatened.

(b)                                 The Company shall have requested and caused Hogan Lovells US LLP, counsel for the Company, to have furnished to the Representatives their opinion and letter, dated the Closing Date and addressed to the Representatives, substantially in the form agreed by such counsel and the Underwriters.

(c)                                  (i) The Company shall have requested and caused Choate Hall & Stewart LLP, intellectual property counsel for the Company, to have furnished to the Representatives their opinion, dated the Closing Date and addressed to the Representatives, substantially in the form agreed by such counsel and the Underwriters. (ii) The Company shall have requested and caused Fish & Richardson P.C., intellectual property counsel for the Company, to have furnished to the Representatives their opinion, dated the Closing Date and addressed to the Representatives, substantially in the form agreed by such counsel and the Underwriters.

(d)                                 The Representatives shall have received from Latham & Watkins LLP, counsel for the Underwriters, such opinion or opinions, dated the Closing Date and addressed to the Representatives, with respect to the issuance and sale of the Securities, the Registration Statement, the Disclosure Package, the Prospectus (together with any

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supplement thereto) and other related matters as the Representatives may reasonably require, and the Company shall have furnished to such counsel such documents as they request for the purpose of enabling them to pass upon such matters.

(e)                                  The Company shall have furnished to the Representatives a certificate of the Company, signed by the principal executive officer and the principal financial or accounting officer of the Company, dated the Closing Date, to the effect that the signers of such certificate have reviewed the Registration Statement, the Disclosure Package, the Prospectus and any amendment or supplement thereto, as well as each electronic road show used in connection with the offering of the Securities, and this Agreement and that:

(i)                                     the representations and warranties of the Company in this Agreement are true and correct on and as of the Closing Date with the same effect as if made on the Closing Date and the Company has complied with all the agreements and satisfied all the conditions on its part to be performed or satisfied at or prior to the Closing Date;

(ii)                                  no stop order suspending the effectiveness of the Registration Statement or any notice objecting to its use has been issued and no proceedings for that purpose have been instituted or, to the Company’s knowledge, threatened; and

(iii)                               since the date of the most recent financial statements included in the Disclosure Package and the Prospectus (exclusive of any supplement thereto), there has been no Material Adverse Effect, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto).

(f)                                    The Company shall have requested and caused Ernst & Young LLP to have furnished to the Representatives, at the Execution Time and at the Closing Date, letters, dated respectively as of the Execution Time and as of the Closing Date, in form and substance satisfactory to the Representatives, substantially in the form as set forth in Exhibit C.

(g)                                 Subsequent to the Execution Time or, if earlier, the dates as of which information is given in the Registration Statement (exclusive of any amendment thereof) and the Prospectus (exclusive of any amendment or supplement thereto), there shall not have been (i) any change or decrease specified in the letter or letters referred to in paragraph (f) of this Section 6 or (ii) any change, or any development involving a prospective change, in or affecting the condition (financial or otherwise), earnings, business or properties of the Company and the Subsidiary taken as a whole, whether or not arising from transactions in the ordinary course of business, except as set forth in or contemplated in the Disclosure Package and the Prospectus (exclusive of any supplement thereto) the effect of which, in any case referred to in clause (i) or (ii) above, is, in the sole judgment of the Representatives, so material and adverse as to make it impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by

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the Registration Statement (exclusive of any amendment thereof), the Disclosure Package and the Prospectus (exclusive of any amendment or supplement thereto).

(h)                                 Prior to the Closing Date, the Company shall have furnished to the Representatives such further customary information, certificates and documents as the Representatives may reasonably request.

(i)                                     The Securities shall have been listed and admitted and authorized for trading on the Nasdaq Global Market, and satisfactory evidence of such actions shall have been provided to the Representatives.

(j)                                     At the Execution Time, the Company shall have furnished to the Representatives a letter substantially in the form of Exhibit A hereto from each officer and director of the Company and each holder of capital stock of the Company prior to the date hereof (other than employees of the Company holding, in aggregate, less than 1% of the outstanding capital stock of the Company) addressed to the Representatives

If any of the conditions specified in this Section 6 shall not have been fulfilled when and as provided in this Agreement, or if any of the opinions and certificates mentioned above or elsewhere in this Agreement shall not be reasonably satisfactory in form and substance to the Representatives and counsel for the Underwriters, this Agreement and all obligations of the Underwriters hereunder may be canceled at, or at any time prior to, the Closing Date by the Representatives.  Notice of such cancellation shall be given to the Company in writing or by telephone or facsimile confirmed in writing.

The documents required to be delivered by this Section 6 shall be delivered at the office of Latham & Watkins LLP, counsel for the Underwriters, at 140 Scott Dr., Menlo Park, CA 94025, on the Closing Date.

7.                                       Reimbursement of Underwriters’ Expenses.  If the sale of the Securities provided for herein is not consummated because any condition to the obligations of the Underwriters set forth in Section 6 hereof is not satisfied, because of any termination pursuant to Section 10 hereof or because of any refusal, inability or failure on the part of the Company to perform any agreement herein or comply with any provision hereof other than by reason of a default by any of the Underwriters, the Company will reimburse the Underwriters severally through Citigroup Global Markets Inc. on demand for all out-of-pocket expenses (including reasonable fees and disbursements of counsel) that shall have been reasonably incurred by them in connection with the proposed purchase and sale of the Securities; provided that if the sale of the Securities is not consummated because of any termination pursuant to Sections 10(i)(b), 10(ii) or 10(iii) the Company shall only be obligated to reimburse 50% of the Underwriters’ out-of-pocket expenses.

8.                                       Indemnification and Contribution.  (a)  The Company agrees to indemnify and hold harmless each Underwriter, the directors, officers, employees and agents of each Underwriter, each person who controls any Underwriter within the meaning of either the Act or the Exchange Act and each affiliate of any Underwriter within the meaning of Rule 405 under the Act against any and all losses, claims, damages or liabilities, joint or several, to which they or

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any of them may become subject under the Act, the Exchange Act or other federal or state statutory law or regulation, at common law or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon any untrue statement or alleged untrue statement of a material fact contained in the registration statement for the registration of the Securities as originally filed or in any amendment thereof, or in any Preliminary Prospectus, the Prospectus, any Issuer Free Writing Prospectus, any Testing-the-Waters Writing, or in any amendment thereof or supplement thereto, or arise out of or are based upon the omission or alleged omission to state therein a material fact required to be stated therein or necessary to make the statements therein not misleading, and agrees to reimburse each such indemnified party, as incurred, for any legal or other expenses reasonably incurred by them in connection with investigating or defending any such loss, claim, damage, liability or action; provided, however, that the Company will not be liable in any such case to the extent that any such loss, claim, damage or liability arises out of or is based upon any such untrue statement or alleged untrue statement or omission or alleged omission made therein in reliance upon and in conformity with written information furnished to the Company by or on behalf of any Underwriter through the Representatives specifically for inclusion therein.  This indemnity agreement is not intended to limit any liability that the Company may otherwise have.

(b)           Each Underwriter severally and not jointly agrees to indemnify and hold harmless the Company, each of its directors, each of its officers who signs the Registration Statement, and each person who controls the Company within the meaning of either the Act or the Exchange Act, to the same extent as the foregoing indemnity from the Company to each Underwriter, but only with reference to written information relating to such Underwriter furnished to the Company by or on behalf of such Underwriter through the Representatives specifically for inclusion in the documents referred to in the foregoing indemnity.  This indemnity agreement will be in addition to any liability which any Underwriter may otherwise have.  The Company acknowledges that the statements set forth (i) in the last paragraph of the cover page regarding delivery of the Securities and, under the heading “Underwriting” or “Plan of Distribution”, (ii) the list of Underwriters and their respective participation in the sale of the Securities, (iii) the sentences related to concessions and reallowances and (iv) the paragraph related to stabilization, syndicate covering transactions and penalty bids in the Preliminary Prospectus and the Prospectus constitute the only information furnished in writing by or on behalf of the several Underwriters for inclusion in the Preliminary Prospectus, the Prospectus or any Issuer Free Writing Prospectus.

(c)           Promptly after receipt by an indemnified party under this Section 8 of notice of the commencement of any action, such indemnified party will, if a claim in respect thereof is to be made against the indemnifying party under this Section 8, notify the indemnifying party in writing of the commencement thereof; but the failure so to notify the indemnifying party (i) will not relieve it from liability under paragraph (a) or (b) above unless and to the extent it did not otherwise learn of such action and such failure results in the forfeiture by the indemnifying party of substantial rights and defenses and (ii) will not, in any event, relieve the indemnifying party from any obligations to any indemnified party other than the indemnification obligation provided in paragraph (a) or (b) above.  The indemnifying party shall be entitled to appoint counsel

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of the indemnifying party’s choice at the indemnifying party’s expense to represent the indemnified party in any action for which indemnification is sought (in which case the indemnifying party shall not thereafter be responsible for the fees and expenses of any separate counsel retained by the indemnified party or parties except as set forth below); provided, however, that such counsel shall be reasonably satisfactory to the indemnified party.  Notwithstanding the indemnifying party’s election to appoint counsel to represent the indemnified party in an action, the indemnified party shall have the right to employ separate counsel (including local counsel), and the indemnifying party shall bear the reasonable fees, costs and expenses of such separate counsel (which, if the Company is the indemnifying party, shall be limited to one such separate counsel for any Underwriter together with all persons who control such Underwriter within the meaning of the Exchange Act or the Act, and no more than three such separate counsel for all the Underwriters) if (i) the use of counsel chosen by the indemnifying party to represent the indemnified party would present such counsel with a conflict of interest, (ii) the actual or potential defendants in, or targets of, any such action include both the indemnified party and the indemnifying party and the indemnified party shall have reasonably concluded that there may be legal defenses available to it and/or other indemnified parties which are different from or additional to those available to the indemnifying party, (iii) the indemnifying party shall not have employed counsel reasonably satisfactory to the indemnified party to represent the indemnified party within a reasonable time after notice of the institution of such action or (iv) the indemnifying party shall authorize the indemnified party to employ separate counsel at the expense of the indemnifying party.  An indemnifying party will not, without the prior written consent of the indemnified parties, settle or compromise or consent to the entry of any judgment with respect to any pending or threatened claim, action, suit or proceeding in respect of which indemnification or contribution may be sought hereunder (whether or not the indemnified parties are actual or potential parties to such claim or action) unless such settlement, compromise or consent includes an unconditional release of each indemnified party from all liability arising out of such claim, action, suit or proceeding.

(d)           In the event that the indemnity provided in paragraph (a), (b) or (c) of this Section 8 is unavailable to or insufficient to hold harmless an indemnified party for any reason, the Company and the Underwriters severally agree to contribute to the aggregate losses, claims, damages and liabilities (including legal or other expenses reasonably incurred in connection with investigating or defending the same) (collectively “Losses”) to which the Company and one or more of the Underwriters may be subject in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and by the Underwriters on the other from the offering of the Securities; provided, however, that in no case shall any Underwriter (except as may be provided in any agreement among underwriters relating to the offering of the Securities) be responsible for any amount in excess of the underwriting discount or commission applicable to the Securities purchased by such Underwriter hereunder.  If the allocation provided by the immediately preceding sentence is unavailable for any reason, the Company and the Underwriters severally shall contribute in such proportion as is appropriate to reflect not only such relative benefits but also the relative fault of the Company on the one hand and of the Underwriters on the other in connection with the

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statements or omissions which resulted in such Losses as well as any other relevant equitable considerations.  Benefits received by the Company shall be deemed to be equal to the total net proceeds from the offering (before deducting expenses) received by it, and benefits received by the Underwriters shall be deemed to be equal to the total underwriting discounts and commissions, in each case as set forth on the cover page of the Prospectus.  Relative fault shall be determined by reference to, among other things, whether any untrue or any alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information provided by the Company on the one hand or the Underwriters on the other, the intent of the parties and their relative knowledge, access to information and opportunity to correct or prevent such untrue statement or omission.  The Company and the Underwriters agree that it would not be just and equitable if contribution were determined by pro rata allocation or any other method of allocation which does not take account of the equitable considerations referred to above.  Notwithstanding the provisions of this paragraph (d), no person guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of the Act) shall be entitled to contribution from any person who was not guilty of such fraudulent misrepresentation.  For purposes of this Section 8, each person who controls an Underwriter within the meaning of either the Act or the Exchange Act, each affiliate of any Underwriter within the meaning of Rule 405 under the Act and each director, officer, employee and agent of an Underwriter shall have the same rights to contribution as such Underwriter, and each person who controls the Company within the meaning of either the Act or the Exchange Act, each officer of the Company who shall have signed the Registration Statement and each director of the Company shall have the same rights to contribution as the Company, subject in each case to the applicable terms and conditions of this paragraph (d).

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9.             Default by an Underwriter.  If any one or more Underwriters shall fail to purchase and pay for any of the Securities agreed to be purchased by such Underwriter or Underwriters hereunder and such failure to purchase shall constitute a default in the performance of its or their obligations under this Agreement, the remaining Underwriters shall be obligated severally to take up and pay for (in the respective proportions which the amount of Securities set forth opposite their names in Schedule I hereto bears to the aggregate amount of Securities set forth opposite the names of all the remaining Underwriters) the Securities which the defaulting Underwriter or Underwriters agreed but failed to purchase; provided, however, that in the event that the aggregate amount of Securities which the defaulting Underwriter or Underwriters agreed but failed to purchase shall exceed 10% of the aggregate amount of Securities set forth in Schedule I hereto, the remaining Underwriters shall have the right to purchase all, but shall not be under any obligation to purchase any, of the Securities, and if such nondefaulting Underwriters do not purchase all the Securities, this Agreement will terminate without liability to any nondefaulting Underwriter or the Company.  In the event of a default by any Underwriter as set forth in this Section 9, the Closing Date shall be postponed for such period, not exceeding five Business Days, as the Representatives shall determine in order that the required changes in the Registration Statement and the Prospectus or in any other documents or arrangements may be effected.  Nothing contained in this Agreement shall relieve any defaulting Underwriter of its liability, if any, to the Company and any nondefaulting Underwriter for damages occasioned by its default hereunder.

10.           Termination.  This Agreement shall be subject to termination in the absolute discretion of the Representatives, by notice given to the Company prior to delivery of and payment for the Securities, if at any time prior to such delivery and payment (i) (a) trading in the Company’s Common Stock shall have been suspended by the Commission or the Nasdaq Global Market or (b) trading in securities generally on the New York Stock Exchange shall have been suspended or limited or minimum prices shall have been established on such exchange, (ii) a banking moratorium shall have been declared either by federal or New York State authorities or (iii) there shall have occurred any outbreak or escalation of hostilities, declaration by the United States of a national emergency or war, or other calamity or crisis the effect of which on financial markets is such as to make it, in the sole judgment of the Representatives, impractical or inadvisable to proceed with the offering or delivery of the Securities as contemplated by the Preliminary Prospectus or the Prospectus (exclusive of any supplement thereto).

11.           Representations and Indemnities to Survive.  The respective agreements, representations, warranties, indemnities and other statements of the Company or its officers and of the Underwriters set forth in or made pursuant to this Agreement will remain in full force and effect, regardless of any investigation made by or on behalf of any Underwriter or the Company or any of the officers, directors, employees, agents, controlling persons or affiliates referred to in Section 8 hereof, and will survive delivery of and payment for the Securities.  The provisions of Sections 7 and 8 hereof shall survive the termination or cancellation of this Agreement.

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12.           Notices.  All communications hereunder will be in writing and effective only on receipt, and, if sent to the Representatives, will be mailed, delivered or telefaxed to (a) the Citigroup Global Markets Inc. General Counsel (fax no.: (212) 816-7912) and confirmed to the General Counsel, Citigroup Global Markets Inc., at 388 Greenwich Street, New York, New York, 10013, Attention:  General Counsel; (b) Morgan Stanley & Co. LLC, Attention: Equity Syndicate Desk (fax no.: (212) 507-4075) and confirmed to the Legal Department, Morgan Stanley & Co. LLC, at 1585 Broadway, New York, New York 10036, Attention: General Counsel; and (c) Leerink Swann LLC (fax no.: (617) 918-4900), One Federal Street, 37th Floor, Boston, Massachusetts 02110-2015, Attention: General Counsel or, if sent to the Company, will be mailed, delivered or telefaxed to the Company Chief Financial Officer (fax no.: (339) 469-8966) and confirmed to it at 1000 Winter St., Suite #3300, Waltham, MA 02451, Attention: Chief Financial Officer, with a copy to Asher Rubin and William Intner, Hogan Lovells US LLP, 100 International Drive, Suite 2000, Baltimore, Maryland 21202.

13.           Successors.  This Agreement will inure to the benefit of and be binding upon the parties hereto and their respective successors and the officers, directors, employees, agents and controlling persons referred to in Section 8 hereof, and no other person will have any right or obligation hereunder.

14.           No fiduciary duty.  The Company hereby acknowledges that (a) the purchase and sale of the Securities pursuant to this Agreement is an arm’s-length commercial transaction between the Company, on the one hand, and the Underwriters and any affiliate through which it may be acting, on the other, (b) the Underwriters are acting as principal and not as an agent or fiduciary of the Company and (c) the Company’s engagement of the Underwriters in connection with the offering and the process leading up to the offering is as independent contractors and not in any other capacity.  Furthermore, the Company agrees that it is solely responsible for making its own judgments in connection with the offering (irrespective of whether any of the Underwriters has advised or is currently advising the Company on related or other matters).  The Company agrees that it will not claim that the Underwriters have rendered advisory services of any nature or respect, or owe an agency, fiduciary or similar duty to the Company, in connection with such transaction or the process leading thereto.

15.           Integration.  This Agreement supersedes all prior agreements and understandings (whether written or oral) between the Company and the Underwriters, or any of them, with respect to the subject matter hereof.

16.           Applicable Law.  This Agreement will be governed by and construed in accordance with the laws of the State of New York applicable to contracts made and to be performed within the State of New York.

17.           Waiver of Jury Trial.  The Company and the Underwriters hereby irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to this Agreement or the transactions contemplated hereby.

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18.           Counterparts.  This Agreement may be signed in one or more counterparts, each of which shall constitute an original and all of which together shall constitute one and the same agreement.

19.           Headings.  The section headings used herein are for convenience only and shall not affect the construction hereof.

20.           Definitions.  The terms that follow, when used in this Agreement, shall have the meanings indicated.

“Act” shall mean the Securities Act of 1933, as amended, and the rules and regulations of the Commission promulgated thereunder.

“Business Day” shall mean any day other than a Saturday, a Sunday or a legal holiday or a day on which banking institutions or trust companies are authorized or obligated by law to close in New York City.

“Commission” shall mean the Securities and Exchange Commission.

“Disclosure Package” shall mean (i) the Preliminary Prospectus that is generally distributed to investors and used to offer the Securities, (ii) the Issuer Free Writing Prospectuses, if any, identified in Schedule II hereto and (iii) any other Free Writing Prospectus that the parties hereto shall hereafter expressly agree in writing to treat as part of the Disclosure Package.

“Effective Date” shall mean each date and time that the Registration Statement, any post-effective amendment or amendments thereto and any Rule 462(b) Registration Statement became or becomes effective.

“Exchange Act” shall mean the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Commission promulgated thereunder.

“Execution Time” shall mean the date and time that this Agreement is executed and delivered by the parties hereto.

“Free Writing Prospectus” shall mean a free writing prospectus, as defined in Rule 405.

“Issuer Free Writing Prospectus” shall mean an issuer free writing prospectus, as defined in Rule 433.

“Investors” shall mean the “Series A Investors” and “Series B Investors” listed in Schedule A to the Second Amended and Restated Investors’ Rights Agreement, dated as of June 6, 2011, among the Company and the other parties named therein, as amended by Amendment No. 1, dated as of July 7, 2011.

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“Preliminary Prospectus” shall mean any preliminary prospectus referred to in paragraph 1(a) above and any preliminary prospectus included in the Registration Statement at the Effective Date that omits Rule 430A Information.

“Prospectus” shall mean the prospectus relating to the Securities that is first filed pursuant to Rule 424(b) after the Execution Time.

“Registration Statement” shall mean the registration statement referred to in paragraph 1(a) above, including exhibits and financial statements and any prospectus supplement relating to the Securities that is filed with the Commission pursuant to Rule 424(b) and deemed part of such registration statement pursuant to Rule 430A, as amended at the Execution Time and, in the event any post-effective amendment thereto or any Rule 462(b) Registration Statement becomes effective prior to the Closing Date, shall also mean such registration statement as so amended or such Rule 462(b) Registration Statement, as the case may be.

“Rule 158”, “Rule 164”, “Rule 172”, “Rule 405”, “Rule 424”, “Rule 430A” and “Rule 433” refer to such rules under the Act.

“Rule 430A Information” shall mean information with respect to the Securities and the offering thereof permitted to be omitted from the Registration Statement when it becomes effective pursuant to Rule 430A.

“Rule 462(b) Registration Statement” shall mean a registration statement and any amendments thereto filed pursuant to Rule 462(b) relating to the offering covered by the registration statement referred to in Section 1(a) hereof.

“Subsidiary” shall mean TESARO UK LIMTED.

“Testing-the-Waters Writing” shall mean any written communication within the meaning of Rule 405 under the Act relating to the Securities that would, but for the provisions of Section 5(d) of the Act, be a “free writing prospectus” as defined in Rule 405 under the Act but without regard to whether a registration statement has been filed.

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If the foregoing is in accordance with your understanding of our agreement, please sign and return to us the enclosed duplicate hereof, whereupon this letter and your acceptance shall represent a binding agreement among the Company and the several Underwriters.

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SCHEDULE I

SCHEDULE II

Schedule of Free Writing Prospectuses included in the Disclosure Package

2

[Attached]

[Letterhead of officer, director or major shareholder of TESARO, Inc.]

TESARO, Inc.
Public Offering of Common Stock

                   , 2012

Citigroup Global Markets Inc.
Morgan Stanley & Co. LLC

Leerink Swann LLC

As Representatives of the several Underwriters,
c/o Citigroup Global Markets Inc.
388 Greenwich Street
New York, New York 10013

Ladies and Gentlemen:

This letter is being delivered to you in connection with the proposed Underwriting Agreement (the “Underwriting Agreement”), between TESARO, Inc., a Delaware corporation (the “Company”), and each of you as representatives of a group of Underwriters named therein, relating to an underwritten public offering of Common Stock, $0.0001 par value (the “Common Stock”), of the Company (the “Offering”).

In order to induce you and the other Underwriters to enter into the Underwriting Agreement, the undersigned will not, without the prior written consent of Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC, offer, sell, contract to sell, pledge or otherwise dispose of, (or enter into any transaction which is designed to, or might reasonably be expected to, result in the disposition (whether by actual disposition or effective economic disposition due to cash settlement or otherwise) by the undersigned or any affiliate of the undersigned or any person in privity with the undersigned or any affiliate of the undersigned), directly or indirectly, including the filing (or participation in the filing) of a registration statement (other than on Form S-8) with the Securities and Exchange Commission in respect of, or establish or increase a put equivalent position or liquidate or decrease a call equivalent position within the meaning of Section 16 of the Securities Exchange Act of 1934, as amended, and the rules and regulations of the Securities and Exchange Commission promulgated thereunder with respect to (together, the “Exchange Act”), any shares of capital stock of the Company or any securities convertible into, or exercisable or exchangeable for such capital stock, or publicly announce an intention to effect any such transaction, for a period from the date hereof until 180 days after the date of the Underwriting Agreement (the “Lock-Up Period”), other than shares of Common Stock or securities convertible into or exercisable or exchangeable for shares of Common Stock disposed of not for consideration as bona fide gifts, by estate planning or intestacy, or distributions to limited partners, members, stockholders or affiliates of the undersigned; provided that (a) each recipient of transferred shares agrees in writing to be bound by the same restrictions in place for the undersigned pursuant to this letter for the duration of the Lock-Up Period and (b) and no filing under Section 16(a) of the Exchange Act reporting a reduction in beneficial ownership of

shares of Common Stock shall be required or shall be voluntarily made by the undersigned during the Lock-Up Period.  The foregoing restrictions shall not apply to transactions relating to shares of Common Stock or other securities acquired in the Offering or in open market transactions; provided that no filing under Section 16(a) of the Exchange Act reporting a reduction in beneficial ownership of shares of Common Stock shall be required or shall be voluntarily made by the undersigned during the Lock-Up Period.  If the undersigned is an officer or director of the Company, the undersigned further agrees that the foregoing restrictions shall be equally applicable to any issuer-directed shares of Common Stock the undersigned may purchase in the Offering.

If the undersigned is an officer or director of the Company, (i) Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC agree that, at least three business days before the effective date of any release or waiver of the foregoing restrictions in connection with a transfer of shares of Common Stock, Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC will notify the Company of the impending release or waiver, and (ii) Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC will require the Company to agree in the Underwriting Agreement to announce the impending release or waiver by press release through a major news service at least two business days before the effective date of the release or waiver.  Any release or waiver granted by Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC hereunder to any such officer or director shall only be effective two business days after the publication date of such press release.  The provisions of this paragraph will not apply if (a) the release or waiver is effected solely to permit a transfer not for consideration and (b) the transferee has agreed in writing to be bound by the same terms described in this letter to the extent and for the duration that such terms remain in effect at the time of the transfer.

If (i) the Company issues an earnings release or material news, or a material event relating to the Company occurs, during the last 17 days of the Lock-Up Period, or (ii) prior to the expiration of the Lock-Up Period, the Company announces that it will release earnings results during the 16-day period beginning on the last day of the Lock-Up Period, the restrictions imposed by this agreement shall continue to apply until the expiration of the 18-day period beginning on the issuance of the earnings release or the occurrence of the material news or material event, unless Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC waive, in writing, such extension.  The undersigned hereby acknowledges that the Company may agree in the Underwriting Agreement to provide written notice of any event that would result in an extension of the Lock-Up Period and agrees that any such notice properly delivered will be deemed to have given to, and received by, the undersigned.

In the event that Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC release, in full or in part, any officer, director or stockholder of the Company (a “Stockholder”) from the restrictions of any lock-up agreement signed by such Stockholder with the Underwriters (a “Triggering Release”), then the undersigned shall be released in the same manner from the restrictions of this Agreement (i.e., in an amount equal to the same percentage of the shares of Common Stock being released in the Triggering Release relative to the undersigned’s ownership of Common Stock at the time of the request of the Triggering Release); provided that (i) in order to request a Triggering Release, the Stockholder requesting the Triggering Release must make a request in writing to the Company setting forth the number of shares of Common Stock to be released; (ii) the Company must notify the other Stockholders of the requested Triggering

Release within three business days; (iii) any other Stockholder that intends to request a release of a pro rata portion of the shares of Common Stock held by them (the “Pro Rata Stockholders”) must (x) make such a request in writing to the Company and (y) certify in writing to the Underwriters and the Company the total number of shares of Common Stock held by such Pro Rata Stockholder; (iv) the Company must (x) make a request in writing to Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC setting forth for the Stockholder requesting the Triggering Release and for each Pro Rata Stockholder the number of shares of Common Stock for which each such Stockholder is requesting a release and (y) provide to Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC the total number of shares of common stock of the Company outstanding as of the date of the request of such Triggering Release and certify in writing to the Underwriters that such number is true and accurate.  If the Company fails to notify the undersigned within three business days of the request of the Triggering Release, the failure to give such notice shall not give rise to any claim or liability against Citigroup Global Markets Inc., Morgan Stanley & Co. LLC or the Underwriters.

Notwithstanding the foregoing, (i) no release by Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC of any shares of Common Stock will constitute a Triggering Release if the aggregate of such releases granted to any individual Stockholder requesting a release does not exceed 1,500,000 shares of Common Stock during the Lock-Up Period (as adjusted for any stock splits, reverse stock splits and the like after the date hereof) (for the avoidance of doubt, each individual affiliate of the undersigned that is a party to a separate lock-up agreement with the Underwriters shall be treated as a separate Stockholder); (ii) if the release, in full or in part, of any shares of Common Stock from the restrictions of its lock-up agreement is in connection with a follow-on offering of common stock (the “Follow-On Offering”), then the shares of Common Stock held by the undersigned shall be released only if the undersigned enters into a new lock-up agreement with the underwriters with respect to the shares of Common Stock that are not being released, upon terms and conditions reasonably satisfactory to the Underwriters but with restrictions that will be no more restrictive than those set forth herein (other than that the expiration of the new lock-up may be up to 180 days from the date of such Follow-On Offering, subject to extension on the same terms as set forth herein) and only to the extent that the undersigned agrees to participate as a selling stockholder in the Follow-On Offering and to sell any of the shares of Common Stock released from the restrictions of this Agreement in such Follow-On Offering; and (iii) Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC shall not release, in full or in part, any Stockholder from the restrictions of any lock-up agreement signed by such Stockholder with the Underwriters unless such Stockholder shall have first made a request pursuant to the clause (i) of the preceding paragraph.

If (i) for any reason the Underwriting Agreement shall be terminated prior to the Closing Date (as defined in the Underwriting Agreement), (ii) the Company informs the undersigned that the Board of Directors for the Company has determined not to proceed with the Offering, (iii) the registration statement filed with the Securities and Exchange Commission in connection with the Offering is withdrawn, or (iv) the Underwriting Agreement is not executed prior to September 30, 2012, the agreement set forth above shall likewise be terminated.

TESARO, Inc.
Public Offering of Common Stock

, 20    

[Name and Address of
Officer or Director
Requesting Waiver]

Dear Mr./Ms. [Name]:

This letter is being delivered to you in connection with the offering by TESARO, Inc. (the “Company”) of [   ] shares of common stock, $0.0001 par value (the “Common Stock”), of the Company and the lock-up letter dated [   ], 2012 (the “Lock-up Letter”), executed by you in connection with such offering, and your request for a [waiver] [release] dated   , 20   , with respect to         shares of Common Stock (the “Shares”).

Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC hereby agree to [waive] [release] the transfer restrictions set forth in the Lock-up Letter, but only with respect to the Shares, effective    , 20   ; provided, however, that such [waiver] [release] is conditioned on the Company announcing the impending [waiver] [release] by press release through a major news service at least two business days before effectiveness of such [waiver] [release].  This letter will serve as notice to the Company of the impending [waiver] [release].

Except as expressly [waived] [released] hereby, the Lock-up Letter shall remain in full force and effect.

cc:  Company

TESARO, Inc.
[Date]

TESARO, Inc. (the “Company”) announced today that Citigroup Global Markets Inc. and Morgan Stanley & Co. LLC, joint book-running managers in the Company’s recent public sale of [   ] shares of common stock, are [waiving] [releasing] a lock-up restriction with respect to     shares of the Company’s common stock held by [certain officers or directors] [an officer or director] of the Company.  The [waiver] [release] will take effect on      ,          20    , and the shares may be sold on or after such date.

This press release is not an offer for sale of the securities in the United States or in any other jurisdiction where such offer is prohibited, and such securities may not be offered or sold in the United States absent registration or an exemption from registration under the United States Securities Act of 1933, as amended.