Exhibit 1.1

EXECUTION VERSION

OncoMed Pharmaceuticals, Inc.

5,500,000 Shares of Common Stock

Underwriting Agreement

August 17, 2016

Leerink Partners LLC

As representative of the several Underwriters

named in Schedule I hereto (the “Representative”),

c/o Leerink Partners LLC

299 Park Avenue

21^st Floor

New York, NY 10171

Ladies and Gentlemen:

OncoMed Pharmaceuticals, Inc., a Delaware corporation (the “Company”), proposes, subject to the terms and conditions stated herein, to issue and sell to the Underwriters named in Schedule I hereto (the “Underwriters”) an aggregate of 5,500,000 shares (the “Firm Shares”) and, at the election of the Underwriters, up to 825,000 additional shares (the “Optional Shares”) of common stock, par value $0.001 per share (“Stock”), of the Company (the Firm Shares and the Optional Shares that the Underwriters elect to purchase pursuant to Section 2 hereof being collectively called the “Shares”).

1. The Company represents and warrants to, and agrees with, each of the Underwriters, as of the date of this Agreement, as of the First Time of Delivery (as hereinafter defined) and as of the Second Time of Delivery (as hereinafter defined), if any, as follows:

(a) Compliance with Registration Requirements. The registration statement on Form S-3 (File No. 333-204914) (the “Initial Registration Statement”) in respect of the Shares has been filed with the Securities and Exchange Commission (the “Commission”); the Initial Registration Statement and any post-effective amendment thereto became effective under the Securities Act of 1933, as amended (the “Act”), in such form. Other than a registration statement, if any, increasing the size of the offering (a “Rule 462(b) Registration Statement”), filed pursuant to Rule 462(b) under the Act, which became effective upon filing, no other document with respect to the Initial Registration Statement or document incorporated by reference therein has heretofore been filed, or transmitted for filing, with the Commission (other than prospectuses filed pursuant to Rule 424(b) of the rules and regulations of the Commission under the Act, each in the form heretofore delivered to the Representative). No stop order suspending the effectiveness of the Initial Registration Statement is in effect and no proceedings for such purpose have been instituted or are pending or, to the knowledge of the Company, are contemplated or threatened by the Commission.

(b) Disclosure. The base prospectus filed as a part of the Initial Registration Statement, in the form in which it has most recently been filed with the Commission on or prior to the date of this Agreement relating to the Shares, is hereinafter called the “Base Prospectus”; any preliminary prospectus (including any preliminary prospectus supplement) relating to the Shares filed with the Commission pursuant to Rule 424(b) under the Act is hereinafter called a “Preliminary Prospectus”; the various parts of the Initial Registration Statement and the Rule 462(b) Registration Statement, if any, including all exhibits thereto and including any prospectus supplement relating to the Shares that is filed with the Commission and deemed by virtue of Rule 430B under the Act to be part of the Initial Registration Statement, each as amended at the time such part of the Initial Registration Statement became effective or such part of the Rule 462(b) Registration Statement, if any, became or hereafter becomes effective, are hereinafter collectively called the “Registration Statement”; the Base Prospectus, as amended and supplemented immediately prior to the Applicable Time (as defined below), is hereinafter called the “Pricing Prospectus”; the form of the final prospectus relating to the Shares filed with Commission pursuant to Rule 424(b) under the Act in accordance with Section 5(a) hereof is hereinafter called the “Prospectus”; any reference herein to the Base Prospectus, the Pricing Prospectus, any Preliminary Prospectus or the Prospectus shall be deemed to refer to and include the documents incorporated by reference therein pursuant to Item 12 of Form S-3, as of the date of such prospectus; any reference to any amendment or supplement to the Base Prospectus, any Preliminary Prospectus or the Prospectus shall be deemed to refer to and include any post-effective amendment to the Registration Statement, any prospectus supplement relating to the Shares filed with the Commission pursuant to Rule 424(b) under the Act and any documents filed under the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and incorporated therein, in each case after the date of the Base Prospectus, such Preliminary Prospectus or the Prospectus, as the case may be; any reference to any amendment to the Registration Statement shall be deemed to refer to and include any annual report of the Company filed pursuant to Section 13(a) or 15(d) of the Exchange Act after the effective date of the Registration Statement that is incorporated by reference in the Registration Statement. Each Preliminary Prospectus and the Prospectus when filed complied in all material respects with the Act and, if filed by electronic transmission pursuant to EDGAR, was identical (except as may be permitted by Regulation S-T under the Act) to the copy thereof delivered to the Underwriters for use in connection with the offer and sale of the Shares. The Registration Statement, at the time it became effective and at all subsequent times, complied and will comply in all material respects with the Act and did not and will not contain any untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading. As of 6:45 p.m. (Eastern Time) on the date of this Agreement (the “Applicable Time”), the Pricing Prospectus did not, and at the First Time of Delivery (as defined in Section 2) and at the Second Time of Delivery (as defined in Section 2), if applicable, the Pricing Prospectus, as then amended or supplemented by the Company, if applicable, will not, contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements therein, in the light of the circumstances under which they were made, not misleading. The Prospectus, as of its date did not, and (as then amended or supplemented) at each applicable Time of Delivery will not, contain 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. The representations and warranties set forth in the three immediately preceding sentences do not apply to statements in or omissions from the Registration Statement or any post-effective amendment thereto, or the Prospectus or the Pricing Prospectus, or any amendments or supplements thereto, made in reliance upon and in conformity with written information relating to any Underwriter furnished to the Company in writing by the Representative expressly for use therein, it being understood and agreed that the only such information consists of the information described in Section 9(b) below. There are no contracts or other documents required to be described in the Pricing Prospectus or the Prospectus or to be filed as an exhibit to the Registration Statement which have not been described or filed as required.

(c) Issuer Free Writing Prospectuses. Any “free writing prospectus” as defined in Rule 433 under the Act relating to the Shares is hereinafter called an “Issuer Free Writing Prospectus.” As of the determination date referenced in Rule 164(h) under the Act, the Company was not, is not or will not be (as applicable) an “ineligible issuer” in connection with the offering of the Shares pursuant to Rules 164, 405 and 433 under the Act. Each Issuer Free Writing Prospectus that the Company is required to file pursuant to Rule 433(d) under the Act has been filed with the Commission in accordance with the requirements of the Act. Each Issuer Free Writing Prospectus that the Company has filed pursuant to Rule 433(d) under the Act or that was prepared by or on behalf of or used or referred to by the Company complies in all material respects with the requirements of Rule 433 under the Act, including timely filing with the Commission or retention where required and legending, and each such Issuer Free Writing Prospectus, as of its issue date and at all subsequent times through the completion of the public offer and sale of the Shares did not and does not include any information that conflicted, conflicts or will conflict with the information contained in the Registration Statement, the Prospectus or any preliminary prospectus and not superseded or modified. Except for the Issuer Free Writing Prospectuses, if any, identified in Schedule II(a), the Company has not prepared, used or referred to, and will not, without prior written consent of the Representative, prepare, use or refer to, any Issuer Free Writing Prospectus.

(d) Emerging Growth Company Status. From the time of initial filing of the Registration Statement with the Commission 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”).

(e) Communications. Any oral or written communications with potential investors undertaken in reliance on Section 5(d) of the Act is hereinafter called a “Section 5(d) Communication”; and any Section 5(d) Communication that is a written communication within the meaning of Rule 405 under the Act is hereinafter called a “Section 5(d) Writing.” The Company (i) has not alone engaged in communications with potential investors in reliance on Section 5(d) of the Act other than those Section 5(d) Writings listed on Schedule II(b) hereto or Section 5(d) Communications with the consent of the Representative with entities that are QIBs or IAIs and (ii) has not authorized anyone other than the Representative to engage in Section 5(d) Communications; as of the Applicable Time, each Section 5(d) Writing identified on Schedule II(b), when considered together with the Pricing Prospectus, did not, as of the Applicable Time, include an 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; and each Section 5(d) Writing, if any, identified on Schedule II(b) hereto does not, as of the date hereof, conflict with the information contained in the Registration Statement, the Preliminary Prospectus and the Prospectus.

(f) Documents Incorporated by Reference. The documents incorporated by reference in the Pricing Prospectus and Prospectus, when they became effective or were filed with the Commission, as the case may be, conformed in all material respects to the requirements of the Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder, and none of such documents contained an untrue statement of a material fact or omitted to state a material fact required to be stated therein or necessary to make the statements therein not misleading; and any further documents so filed and incorporated by reference in the Prospectus or any further amendment or supplement thereto, when such documents become effective or are filed with the Commission, as the case may be, will conform in all material respects to the requirements of the Act or the Exchange Act, as applicable, and the rules and regulations of the Commission thereunder and will not contain an untrue statement of a material fact or omit to state a material fact required to be stated therein or necessary to make the statements therein not misleading; provided, however, that this representation and warranty shall not apply to any statements or omissions made in reliance upon and in conformity with information furnished in writing to the Company by an Underwriter through the Representative expressly for use therein; and no such documents were filed with the Commission since the Commission’s close of business on the business day immediately prior to the date of this Agreement and prior to the execution of this Agreement, except as set forth on Schedule II(b) hereto.

(g) Distribution of Offering Material By the Company. Prior to the later of (i) the expiration or termination of the option granted to the several Underwriters in Section 2, and (ii) the completion of the Underwriters’ distribution of the Shares and (iii) the expiration of 25 days after the date of the Prospectus, the Company has not distributed any offering material in connection with the offering and sale of the Shares other than the Registration Statement, the Pricing Prospectus, the Prospectus, the Issuer Free Writing Prospectuses, if any, identified on Schedule II(a) and any Section 5(d) Writing, if any, identified on Schedule II(b).

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

(i) Authorization of the Shares. The Shares have been duly authorized for issuance and sale pursuant to this Agreement and, when issued and delivered by the Company against payment therefor pursuant to this Agreement, will be validly issued, fully paid and nonassessable, and the issuance and sale of the Shares is not subject to any preemptive rights, rights of first refusal or other similar rights to subscribe for or purchase the Shares that have not been duly waived or satisfied (except as disclosed in the Registration Statement, the Pricing Prospectus and the Prospectus).

(j) No Material Adverse Change. Except as otherwise disclosed in the Registration Statement, the Pricing Prospectus and the Prospectus, subsequent to the respective dates as of which information is given in the Registration Statement, the Pricing Prospectus and the Prospectus: (i) there has been no material adverse change, or any development that could reasonably be expected to result in a material adverse change, in the condition (financial or otherwise), earnings, business, properties, operations or prospects, whether or not arising from transactions in the ordinary course of business, of the Company (any such change being referred to herein as a “Material Adverse Change”); (ii) the Company has not incurred any material liability or obligation, indirect, direct or contingent, including without limitation any losses or interference with its business from fire, explosion, flood, earthquake, accident or other calamity, whether or not covered by insurance, or from any strike, labor dispute or court or governmental action, order or decree, that are material, individually or in the aggregate, to the Company, and has not entered into any material transactions or agreements not in the ordinary course of business; and (iii) there has not been any material decrease in the capital stock (other than the issuance of shares of Stock upon exercise of stock options described as outstanding in, and the grant of options and awards under existing equity incentive plans or employee stock purchase plans described in, the Registration Statement, the Pricing Prospectus and the Prospectus) or any material increase in any short-term or long-term indebtedness of the Company and there has been no dividend or distribution of any kind declared, paid or made by the Company on any class of capital stock, or any repurchase or redemption by the Company of any class of capital stock.

(k) Independent Accountants. Ernst & Young LLP, which has expressed its opinion with respect to the financial statements (which term as used in this Agreement includes the related notes thereto) filed with the Commission as a part of the Registration Statement, the Pricing Prospectus and the Prospectus, is (i) an independent registered public accounting firm as required by the Act, and the rules of the Public Company Accounting Oversight Board (“PCAOB”), (ii) in compliance with the applicable requirements relating to the qualification of accountants under Rule 2-01 of Regulation S-X under the Act and (iii) a registered public accounting firm as defined by the PCAOB whose registration has not been suspended or revoked and who has not requested such registration to be withdrawn.

(l) Financial Statements. The financial statements filed with the Commission as a part of the Registration Statement, the Pricing Prospectus and the Prospectus present fairly, in all material respects, the financial position of the Company as of the dates indicated and the results of operations, changes in stockholders’ equity and cash flows for the periods specified. Such financial statements have been prepared in conformity with generally accepted accounting principles applied on a consistent basis throughout the periods involved, except as may be expressly stated in the related notes thereto and except in the case of unaudited financial statements, which are subject to normal and recurring year-end adjustments and do not contain certain footnotes as permitted by the applicable rules of the Commission. No other financial statements or supporting schedules are required to be included in the Registration Statement, the Pricing Prospectus or the Prospectus. The financial data set forth in each of the Registration Statement, the Pricing Prospectus and the Prospectus under the caption “Capitalization” present fairly, in all material respects, the information set forth therein on a basis consistent with that of the audited financial statements contained in the Registration Statement, the Pricing Prospectus and the Prospectus. All disclosures contained in the Registration Statement, any preliminary prospectus or the Prospectus and any Issuer Free Writing Prospectus, that constitute non-GAAP financial measures (as defined by the Exchange Act and the rules and regulations under the Act) comply, in all material respects, with Regulation G under the Exchange Act and Item 10 of Regulation S-K under the Act, as applicable. To the Company’s knowledge, no person who has been suspended or barred from being associated with a registered public accounting firm, or who has failed to comply with any sanction pursuant to Rule 5300 promulgated by the PCAOB, has participated in or otherwise aided the preparation of, or audited, the financial statements, supporting schedules or other financial data filed with the Commission as a part of the Registration Statement, the Pricing Prospectus and the Prospectus.

(m) Company’s Accounting System. The Company makes and keeps accurate books and records and maintains a system of internal accounting controls over financial reporting (as such term is defined in Rule 13a-15(f) under the Exchange Act) that complies with the requirements of the Exchange Act and has been designed by the Company’s principal executive officer and principal financial officer, or under their supervision, and is sufficient to provide reasonable assurance that: (i) transactions are executed in accordance with management’s general or specific authorization; (ii) transactions are recorded as necessary to permit preparation of financial statements in conformity with generally accepted accounting principles and to maintain accountability for assets; (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 existing assets at reasonable intervals and appropriate action is taken with respect to any differences.

(n) Disclosure Controls and Procedures; Deficiencies in or Changes to Internal Control Over Financial Reporting. The Company has established and maintains disclosure controls and procedures (as defined in Rules 13a-15 and 15d-15 under the Exchange Act), which (i) are designed to ensure that material information relating to the Company is made known to the Company’s principal executive officer and its principal financial officer by others within the Company, particularly during the periods in which the periodic reports required under the Exchange Act are being prepared; (ii) have been evaluated by management of the Company for effectiveness as of the end of the Company’s most recent fiscal quarter; and (iii) are effective to the reasonable assurance level as of the most recent fiscal quarter. Since the end of the Company’s most recent audited fiscal year, there have been no material weaknesses in the Company’s internal control over financial reporting (whether or not remediated) and no change in the Company’s internal control over financial reporting that has materially affected, or is reasonably likely to materially affect, the Company’s internal control over financial reporting. The Company is not aware of any change in its internal control over financial reporting that has occurred during its most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect, the Company’s internal control over financial reporting.

(o) Incorporation and Good Standing of the Company. The Company has been duly incorporated and is validly existing as a corporation in good standing under the laws of the jurisdiction of its incorporation and has the corporate power and authority to own, lease and operate its properties and to conduct its business as described in the Registration Statement, the Pricing Prospectus and the Prospectus and to enter into and perform its obligations under this Agreement. The Company is duly qualified as a foreign corporation to transact business and is in good standing in the State of California and each other jurisdiction in which such qualification is required, whether by reason of the ownership or leasing of property or the conduct of business, except where the failure to so qualify or to be in good standing could not be expected, individually or in the aggregate, to have a material adverse effect on the condition (financial or otherwise), earnings, business, properties, operations or prospects of the Company (a “Material Adverse Effect”).

(p) Subsidiaries. The Company has no subsidiaries (as defined in Rule 405 under the Act).

(q) Capitalization and Other Capital Stock Matters. The authorized, issued and outstanding capital stock of the Company is as set forth in the Registration Statement, the Pricing Prospectus and the Prospectus under the caption “Capitalization” (other than for subsequent issuances, if any, pursuant to equity incentive plans and employee stock purchase plans, or upon the exercise of outstanding options or warrants, in each case described in the Registration Statement, the Pricing Prospectus and the Prospectus). The Stock (including the Shares) conforms in all material respects to the description thereof contained in the Pricing Prospectus. All of the issued and outstanding shares of Stock have been duly authorized and validly issued, are fully paid and nonassessable and have been issued in compliance with all federal and state securities laws. None of the outstanding shares of Stock was issued in violation of any preemptive rights, rights of first refusal or other similar rights to subscribe for or purchase securities of the Company. There are no authorized or outstanding options, warrants, preemptive rights, rights of first refusal or other rights to purchase, or equity or debt securities convertible into or exchangeable or exercisable for, any capital stock of the Company other than those described in the Registration Statement, the Pricing Prospectus and the Prospectus. The descriptions of the Company’s equity incentive and employee stock purchase plans or arrangements, and the options or other rights granted thereunder, set forth in the Registration Statement, the Pricing Prospectus and the Prospectus accurately and fairly present the information required to be shown with respect to such plans, arrangements, options and rights.

(r) Stock Exchange Listing. The Shares have been approved for listing on The NASDAQ Global Select Market (the “NASDAQ”), subject only to official notice of issuance.

(s) Non-Contravention of Existing Instruments; No Further Authorizations or Approvals Required. The Company is not in violation of its certificate of incorporation or by-laws or is in default (or, with the giving of notice or lapse of time, would be in default) (“Default”) under any indenture, loan, credit agreement, note, lease, license agreement, contract, franchise or other instrument (including, without limitation, any pledge agreement, security agreement, mortgage or other instrument or agreement evidencing, guaranteeing, securing or relating to indebtedness) to which the Company is a party or by which it may be bound, or to which any of its properties or assets are subject (each, an “Existing Instrument”), except for such Defaults as could not be expected, individually or in the aggregate, to have a Material Adverse Effect. The Company’s execution, delivery and performance of this Agreement, consummation of the transactions contemplated hereby and by the Registration Statement, the Pricing Prospectus and the Prospectus and the issuance and sale of the Shares (including the use of proceeds from the sale of the Shares as described in the Registration Statement, the Pricing Prospectus and the Prospectus under the caption “Use of Proceeds”) (i) have been duly authorized by all necessary corporate action and will not result in any violation of the provisions of the certificate of incorporation or by-laws of the Company, (ii) will not conflict with or constitute a breach of, or Default or a Debt Repayment Triggering Event (as defined below) under, or result in the creation or imposition of any lien, charge or encumbrance upon any property or assets of the Company pursuant to, or require the consent of any other party to, any Existing Instrument, except for such conflicts, breaches, Defaults or Debt Repayment Triggering Events or liens, charges or encumbrances that would not, singly or in the aggregate, result in a Material Adverse Effect, and (iii) will not result in any violation of any law, administrative regulation or administrative or court decree applicable to the Company, except for such violations as would not, singly or in the aggregate, result in a Material Adverse Effect. No consent, approval, authorization or other order of, or registration or filing with, any court or other governmental or regulatory authority or agency, is required for the Company’s execution, delivery and performance of this Agreement and consummation of the transactions contemplated hereby and by the Registration Statement, the Pricing Prospectus and the Prospectus, except such as have been obtained or made by the Company and are in full force and effect under the Act and such as may be required under applicable state securities or blue sky laws or the Financial Industry Regulatory Authority, Inc. (“FINRA”). As used herein, a “Debt Repayment Triggering Event” means any event or condition which gives, or with the giving of notice or lapse of time would give, the holder of any note, debenture or other evidence of indebtedness (or any person acting on such holder’s behalf) the right to require the repurchase, redemption or repayment of all or a portion of such indebtedness by the Company.

(t) Compliance with Laws. The Company has been and is in compliance with all applicable laws, rules and regulations, except where failure to be so in compliance could not reasonably be expected, individually or in the aggregate, to have a Material Adverse Effect.

(u) No Material Actions or Proceedings. There is no action, suit, proceeding, inquiry or investigation brought by or before any governmental entity now pending or, to the knowledge of the Company, threatened, against or affecting the Company, which would reasonably be expected, individually or in the aggregate, to have a Material Adverse Effect or would materially and adversely affect the consummation of the transactions contemplated by this Agreement or the performance by the Company of its obligations hereunder; and the aggregate of all pending legal or governmental proceedings to which the Company is a party or of which any of its properties or assets is the subject, including ordinary routine litigation incidental to the business, if determined adversely to the Company, would not reasonably be expected to have a Material Adverse Effect. No material labor dispute with the employees of the Company, or with the employees of any principal supplier, manufacturer, customer or contractor of the Company, exists or, to the best of the Company’s knowledge, is threatened or imminent, which would reasonably be expected to result in a Material Adverse Effect.

(v) Intellectual Property Rights. Except as disclosed in the Registration Statement, the Pricing Prospectus and the Prospectus, the Company owns, or has obtained valid and enforceable licenses for, the inventions, patent applications, patents, trademarks, trade names, service names, copyrights, trade secrets and other intellectual property described in the Registration Statement, the Pricing Prospectus and the Prospectus as being owned or licensed by them that are necessary for the conduct of its business as currently conducted or as currently proposed to be conducted (collectively, “Intellectual Property”). To the Company’s knowledge: (i) there are no third parties who have rights to any material Intellectual Property, except for the customary reversionary rights of third-party licensors with respect to Intellectual Property that is disclosed in the Registration Statement, the Pricing Prospectus and the Prospectus as licensed to the Company and except as disclosed in the Registration Statement, the Pricing Prospectus and the Prospectus; and (ii) there is no infringement by third parties of any material Intellectual Property. Except as disclosed in the Registration Statement, the Pricing Prospectus and the Prospectus or as would not, individually or in the aggregate, reasonably be expected to result in a Material Adverse Effect, there is no pending or, to the Company’s knowledge, threatened action, suit, proceeding or claim by others: (A) challenging the Company’s rights in or to any material Intellectual Property; (B) challenging the validity, enforceability or scope of any material Intellectual Property; or (C) asserting that the Company infringes or otherwise violates, or would, upon conducting its business as currently conducted or as currently proposed to be conducted in the Registration Statement, the Pricing Prospectus or the Prospectus, infringe or violate, any patent, trademark, trade name, service name, copyright, trade secret or other proprietary rights of others, which infringement or violation (if the subject of any unfavorable decision, ruling or finding), individually or in the aggregate, would reasonably be expected to result in a Material Adverse Effect. The Company has complied or will comply in due time with the terms of each agreement pursuant to which Intellectual Property has been licensed to the Company, except where failure to comply could not reasonably be expected to have a Material Adverse Effect, and all such agreements are in full force and effect. The seven anti-CSC product candidates described in the Registration Statement, the Pricing Prospectus and the Prospectus as currently under clinical development by the Company fall within the scope of one or more claims of one or more patents or patent applications owned by, or exclusively licensed to, the Company.

(w) All Necessary Permits, etc. The Company possesses such valid and current certificates, authorizations or permits required by state, federal or foreign regulatory agencies or bodies to conduct its business as currently conducted and as described in the Registration Statement, the Pricing Prospectus or the Prospectus (“Permits”), except where the failure to so possess could not reasonably be expected to, individually or in the aggregate, result in a Material Adverse Effect. The Company is not in violation of, or in default under, any of the Permits, except where such violation or default could not reasonably be expected to, individually or in the aggregate, result in a Material Adverse Effect. The Company has not received any written notice of proceedings relating to the revocation or modification of, or non-compliance with, any such certificate, authorization or permit, which, individually or in the aggregate, if the subject of an unfavorable decision, ruling or finding, could reasonably be expected to result in a Material Adverse Effect.

(x) Title to Properties. The Company does not own any real property. The Company has good title to all personal property and other assets reflected as owned in the financial statements referred to in Section 1(l) above (or elsewhere in the Registration Statement, the Pricing Prospectus or the Prospectus), in each case free and clear of any security interests, mortgages, liens, encumbrances, equities, adverse claims and other defects, except such as do not, individually or in the aggregate, materially affect the value of such property and do not materially interfere with the use made and proposed to be made of such property by the Company. The real property, improvements, equipment and personal property held under lease by the Company are held under valid and enforceable leases, with such exceptions as are not material and do not materially interfere with the use made or proposed to be made of such real property, improvements, equipment or personal property by the Company.

(y) Tax Law Compliance. The Company has filed all necessary federal, state and foreign income and franchise tax returns through the date hereof or has timely requested extensions thereof, pursuant to applicable federal, state, foreign, local or other law except insofar as the failure to file such returns could not reasonably be expected to result in a Material Adverse Effect. The Company has paid all taxes due and payable, except for such taxes, if any, as are being contested in good faith and as to which adequate reserves have been established by the Company and except where the failure to pay such taxes could not reasonably be expected to result in a Material Adverse Effect. The Company has made adequate charges, accruals and reserves in the applicable financial statements referred to in Section 1(l) above in respect of all federal, state and foreign income and franchise taxes for all periods as to which the tax liability of the Company has not been finally determined, except to the extent of any inadequacy that could not reasonably be expected to result in a Material Adverse Effect.

(z) Insurance. The Company is insured by reputable institutions with policies in such amounts and with such deductibles and covering such risks as the Company reasonably believes are generally adequate and customary for its business including, but not limited to, policies covering real and personal property owned or leased by the Company against theft, damage, destruction, acts of vandalism and policies covering the Company for product liability claims and clinical trial liability claims. The Company has no reason to believe that it will not be able (i) to renew its existing insurance coverage as and when such policies expire or (ii) to obtain comparable coverage from similar institutions as may be necessary or appropriate to conduct its business as now conducted and at a cost that could not reasonably be expected to result in a Material Adverse Effect.

(aa) Compliance with Environmental Laws. Except as could not reasonably be expected, individually or in the aggregate, to have a Material Adverse Effect: (i) the Company is not in violation of any applicable federal, state, local or foreign statute, law, rule, regulation, ordinance, code, policy or rule of common law or any judicial or administrative interpretation thereof, including any judicial or administrative order, consent, decree or judgment, relating to pollution or protection of human health, the environment (including, without limitation, ambient air, surface water, groundwater, land surface or subsurface strata) or wildlife, including, without limitation, laws and regulations relating to the release or threatened release of chemicals, pollutants, contaminants, wastes, toxic substances, hazardous substances, petroleum or petroleum products (collectively, “Hazardous Materials”) or to the manufacture, processing, distribution, use, treatment, storage, disposal, transport or handling of Hazardous Materials (collectively, “Environmental Laws”); (ii) the Company has all permits, authorizations and approvals required under any applicable Environmental Laws and is in compliance with their requirements; (iii) there are no pending or, to the knowledge of the Company, threatened administrative, regulatory or judicial actions, suits, demands, demand letters, claims, liens, notices of noncompliance or violation, investigation or proceedings relating to any Environmental Law against the Company; and (iv) to the knowledge of the Company, there are no events or circumstances existing as of the date hereof that might reasonably be expected to form the basis of an order for clean-up or remediation, or an action, suit or proceeding by any private party or governmental body or agency, against or affecting the Company relating to Hazardous Materials or any Environmental Laws.

(bb) ERISA Compliance. The Company and any “employee benefit plan” (as defined under the Employee Retirement Income Security Act of 1974, as amended, and the regulations and published interpretations thereunder (collectively, “ERISA”)) established or maintained by the Company or its “ERISA Affiliates” (as defined below) are in compliance in all material respects with ERISA. “ERISA Affiliate” means, with respect to the Company, any member of any group of organizations described in Sections 414(b), (c), (m) or (o) of the Internal Revenue Code of 1986, as amended, and the regulations and published interpretations thereunder (the “Code”) of which the Company is a member. No “reportable event” (as defined under ERISA) has occurred or is reasonably expected to occur with respect to any “employee benefit plan” established or maintained by the Company or any of its ERISA Affiliates. No “employee benefit plan” established or maintained by the Company or any of its ERISA Affiliates, if such “employee benefit plan” were terminated, would have any “amount of unfunded benefit liabilities” (as defined under ERISA). Neither the Company nor any of its ERISA Affiliates has incurred or reasonably expects to incur any liability under (i) Title IV of ERISA with respect to termination of, or withdrawal from, any “employee benefit plan” or (ii) Sections 412, 4971, 4975 or 4980B of the Code. Each employee benefit plan established or maintained by the Company or any of its ERISA Affiliates that is intended to be qualified under Section 401(a) of the Code is so qualified and, to the Company’s knowledge, nothing has occurred, whether by action or failure to act, which would cause the loss of such qualification.

(cc) Company Not an “Investment Company.” The Company is not, and will not be, either after receipt of payment for the Shares or after the application of the proceeds therefrom as described under “Use of Proceeds” in the Registration Statement, the Pricing Prospectus or the Prospectus, required to register as an “investment company” under the Investment Company Act of 1940, as amended.

(dd) No Price Stabilization or Manipulation; Compliance with Regulation M. The Company has not taken, directly or indirectly, without giving effect to activities by the Representative, any action designed to or that could reasonably be expected to cause or result in stabilization or manipulation of the price of the Shares or of any “reference security” (as defined in Rule 100 of Regulation M under the Exchange Act (“Regulation M”)) with respect to the Shares, whether to facilitate the sale or resale of the Shares or otherwise, and has taken no action which would directly or indirectly violate Regulation M.

(ee) Related-Party Transactions. There are no business relationships or related-party transactions involving the Company or any other person required to be described in the Registration Statement, the Pricing Prospectus or the Prospectus that have not been described as required.

(ff) FINRA Matters. All of the information provided to the Underwriters or to counsel for the Underwriters by the Company, its counsel, its officers and directors and the holders of any securities (debt or equity) or options to acquire any securities of the Company in connection with the offering of the Shares is true, complete, correct in all material respects and compliant with FINRA’s rules and any letters, filings or other supplemental information provided to FINRA pursuant to FINRA Rules or NASD Conduct Rules is true, complete and correct in all material respects.

(gg) Parties to Lock-up Agreements. The Company has furnished to the Underwriters a letter agreement in the form attached hereto as Exhibit B from each of the persons listed on Exhibit A. Such Exhibit A lists under an appropriate caption the directors and officers of the Company. If any additional persons shall become directors or officers (as defined in Rule 16a-1(f) under the Exchange Act) of the Company prior to the end of the Company Lock-up Period (as defined below), the Company shall cause each such person, in connection with their appointment or election as a director or executive officer of the Company, to execute and deliver to the Representative a lock-up agreement, which lock-up agreement shall be effective as of the time of such person’s appointment or election; provided that any such lock-up agreement shall be on the same terms and conditions as the lock-up agreements executed and delivered by the other directors and officers of the Company.

(hh) Statistical and Market-Related Data. All statistical, demographic and market-related data included in the Registration Statement, the Pricing Prospectus or the Prospectus are based on or derived from sources that the Company believes, after reasonable inquiry, to be reliable and accurate in all material respects. To the extent required, the Company has obtained written consent to the use of such data from such sources.

(ii) No Unlawful Contributions or Other Payments. Neither the Company nor, to the Company’s knowledge, any employee or agent of the Company, has made any contribution or other payment to any official of, or candidate for, any federal, state or foreign office in violation of any applicable law or of the character required to be disclosed in the Registration Statement, the Pricing Prospectus or the Prospectus.

(jj) Foreign Corrupt Practices Act. Neither the Company nor, to the knowledge of the Company, any director, officer, agent, employee or representative of the Company has, in the course of its actions for, or on behalf of, the Company (i) used any corporate funds for any unlawful contribution, gift, entertainment or other unlawful expenses relating to political activity; (ii) made any direct or indirect unlawful payment to any domestic government official, “foreign official” (as defined in the U.S. Foreign Corrupt Practices Act of 1977, as amended, and the rules and regulations thereunder (collectively, the “FCPA”)) or employee from corporate funds; (iii) violated or is in violation of any provision of the FCPA or any applicable non-U.S. anti-bribery statute or regulation; or (iv) made any unlawful bribe, rebate, payoff, influence payment, kickback or other unlawful payment to any domestic government official, such foreign official or employee; and the Company has conducted its business in compliance with the FCPA and has instituted and maintains policies and procedures designed to ensure, and which are reasonably expected to continue to ensure, continued compliance therewith. The Company has no controlled affiliates.

(kk) Money Laundering Laws. The operations of the Company are, and have been conducted at all times, in compliance with applicable financial recordkeeping and reporting requirements of the Currency and Foreign Transactions Reporting Act of 1970, as amended, the money laundering statutes of all applicable jurisdictions, the rules and regulations thereunder and any related or similar applicable 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 with respect to the Money Laundering Laws is pending or, to the knowledge of the Company, threatened.

(ll) OFAC. Neither the Company nor, to the knowledge of the Company, any director, officer, agent, employee or representative of the Company is currently subject to any U.S. 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 this offering, or lend, contribute or otherwise make available such proceeds to any subsidiary, or any joint venture partner or other person or entity, for the purpose of financing the activities of or business with any person, or in any country or territory, that currently is subject to any U.S. sanctions administered by OFAC or in any other manner that will result in a violation by any person (including any person participating in the transaction whether as underwriter, advisor, investor or otherwise) of U.S. sanctions administered by OFAC.

(mm) Brokers. Except pursuant to this Agreement, there is no broker, finder or other party that is entitled to receive from the Company any brokerage or finder’s fee or other fee or commission as a result of any transactions contemplated by this Agreement.

(nn) Forward-Looking Statements. Each financial or operational projection or other “forward-looking statement” (as defined by Section 27A of the Act or Section 21E of the Exchange Act) contained in the Registration Statement, the Pricing Prospectus or the Prospectus (i) was so included by the Company in good faith and with reasonable basis after due consideration by the Company of the underlying assumptions, estimates and other applicable facts and circumstances and (ii) is accompanied by meaningful cautionary statements identifying those factors that could cause actual results to differ materially from those in such forward-looking statement. No such statement was made with the knowledge of an executive officer of the Company that it was false or misleading.

(oo) Clinical Data and Regulatory Compliance. The preclinical tests and clinical trials (collectively, “studies”) that are described in, or the results of which are referred to in, the Registration Statement, the Pricing Prospectus or the Prospectus were and, if still pending, are being conducted in all material respects in accordance with the protocols, procedures and controls designed and approved for such studies and with standard medical and scientific research procedures; each description of the results of such studies is accurate and complete in all material respects and fairly presents the data derived from such studies, and the Company has no knowledge as of the date hereof of any other studies the results of which are inconsistent with, or otherwise call into question, the results described or referred to in the Registration Statement, the Pricing Prospectuses or the Prospectus; the Company has made all such filings and obtained all such approvals as may be required by the Food and Drug Administration of the U.S. Department of Health and Human Services or any committee thereof or from any other U.S. or foreign government or drug or medical device regulatory agency, or health care facility Institutional Review Board (collectively, the “Regulatory Agencies”), except where the failure to make such filing or obtain such approval could not reasonably be expected to, individually or in the aggregate, result in a Material Adverse Effect; except such as are described in the Registration Statement, the Pricing Prospectus and the Prospectus, the Company has not received any written notice of, or correspondence from, any Regulatory Agency requiring the termination or suspension of any clinical trials that are described or referred to in the Registration Statement, the Pricing Prospectus or the Prospectus; and the Company has operated and currently is in compliance in all material respects with all applicable rules, regulations and policies of the Regulatory Agencies.

(pp) No Contract Terminations. The Company has not sent or received any written communication regarding termination of, or intent not to renew, any of the contracts or agreements referred to or described in the Registration Statement, the Pricing Prospectus or the Prospectus, or filed as an exhibit to the Registration Statement, and no such termination or non-renewal has been threatened by the Company or, to the Company’s knowledge, any other party to any such contract or agreement, which threat of termination or non-renewal has not been rescinded as of the date hereof.

Any certificate signed by any officer of the Company and delivered to any Underwriter or to counsel for the Underwriters pursuant to this Agreement shall be deemed a representation and warranty by the Company to each Underwriter as to the matters covered thereby.

The Company has a reasonable basis for making each of the representations set forth in this Section 1. The Company acknowledges that the Underwriters and, for purposes of the opinions to be delivered pursuant to Section 8 hereof, counsel to the Company and counsel to the Underwriters, will rely upon the accuracy and truthfulness of the foregoing representations and hereby consents to such reliance.

2. Subject to the terms and conditions herein set forth, (a) the Company agrees to issue and sell to each of the Underwriters, and each of the Underwriters agrees, severally and not jointly, to purchase from the Company, at a purchase price per share of $9.40, the number of Firm Shares set forth opposite the name of such Underwriter in Schedule I hereto and (b) in the event and to the extent that the Underwriters shall exercise the election to purchase Optional Shares as provided below, the Company agrees to issue and sell to each of the Underwriters, and each of the Underwriters agrees, severally and not jointly, to purchase from the Company, at the purchase price per share set forth in clause (a) of this Section 2, that portion of the number of Optional Shares as to which such election shall have been exercised (to be adjusted by the Representative so as to eliminate fractional shares) determined by multiplying such number of Optional Shares by a fraction, the numerator of which is the maximum number of Optional Shares which such Underwriter is entitled to purchase as set forth opposite the name of such Underwriter in Schedule I hereto and the denominator of which is the maximum number of Optional Shares that all of the Underwriters are entitled to purchase hereunder.

The Company hereby grants to the Underwriters the right to purchase at their election up to 825,000 Optional Shares, at the purchase price per share set forth in the paragraph above, provided that the purchase price per Optional Share shall be reduced by an amount per share equal to any dividends or distributions declared by the Company and payable on the Firm Shares but not payable on the Optional Shares. Any such election to purchase Optional Shares may be exercised only by written notice from the Representative to the Company, given within a period of 30 calendar days after the date of this Agreement, setting forth the aggregate number of Optional Shares to be purchased and the date on which such Optional Shares are to be delivered, as determined by the Representative but in no event earlier than the First Time of Delivery (as defined in Section 4 hereof) or, unless the Representative and the Company otherwise agree in writing, earlier than two or later than ten business days after the date of such notice.

3. Upon the authorization by the Representative of the release of the Firm Shares, the several Underwriters propose to offer the Firm Shares for sale upon the terms and conditions set forth in the Prospectus.

4. (a) The Shares to be purchased by each Underwriter hereunder, in definitive form, and in such authorized denominations and registered in such names as the Representative may request upon at least forty-eight hours’ prior notice to the Company shall be delivered by or on behalf of the Company to the Representative, through the facilities of the Depository Trust Company (“DTC”), for the account of such Underwriter, against payment by or on behalf of such Underwriter of the purchase price therefor by wire transfer of Federal (same-day) funds to the account specified by the Company to the Representative at least forty-eight hours in advance. The Company will cause the certificates representing the Shares to be made available for checking and packaging at least twenty-four hours prior to the Time of Delivery (as defined below) with respect thereto at the office of DTC or its designated custodian (the “Designated Office”). The time and date of such delivery and payment shall be, with respect to the Firm Shares, 9:30 a.m., New York City time, on August 23, 2016 or such other time and date as the Representative and the Company may agree upon in writing, and, with respect to the Optional Shares, 9:30 a.m., New York time, on the date specified by the Representative in the written notice given by the Representative of the Underwriters’ election to purchase such Optional Shares, or such other time and date as the Representative and the Company may agree upon in writing. Such time and date for delivery of the Firm Shares is herein called the “First Time of Delivery”, such time and date for delivery of the Optional Shares, if not the First Time of Delivery, is herein called the “Second Time of Delivery”, and each such time and date for delivery is herein called a “Time of Delivery”.

(b) The documents to be delivered at each Time of Delivery by or on behalf of the parties hereto pursuant to Section 8 hereof, including the cross receipt for the Shares and any additional documents requested by the Underwriters pursuant to Section 8 hereof, will be delivered at the offices of Davis Polk & Wardwell LLP, 450 Lexington Avenue, New York, New York (the “Closing Location”), and the Shares will be delivered at the Designated Office, all at such Time of Delivery. A meeting will be held at the Closing Location at 3:30 p.m., New York City time, on the New York Business Day next preceding such Time of Delivery, at which meeting the final drafts of the documents to be delivered pursuant to the preceding sentence will be available for review by the parties hereto. For the purposes of this Section 4, “New York Business Day” shall mean each Monday, Tuesday, Wednesday, Thursday and Friday which is not a day on which banking institutions in New York are generally authorized or obligated by law or executive order to close.

5. The Company agrees with each of the Underwriters:

(a) To prepare the Prospectus in a form approved by the Representative and to file such Prospectus pursuant to Rule 424(b) under the Act not later than the Commission’s close of business on the second business day following the date of this Agreement or such earlier time as may be required under the Act; to make no further amendment or any supplement to the Registration Statement, the Base Prospectus or the Prospectus prior to the last Time of Delivery which shall be reasonably disapproved by the Representative promptly after reasonable notice thereof; to advise the Representative, promptly after it receives notice thereof, of the time when any amendment to the Registration Statement has been filed or becomes effective or any amendment or supplement to the Prospectus has been filed and to furnish the Representative with copies thereof; to file promptly all material required to be filed by the Company with the Commission pursuant to Rule 433(d) under the Act within the time required by such Rule; to file promptly all reports and any definitive proxy or information statements required to be filed by the Company with the Commission pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act subsequent to the date of the Prospectus and for so long as the delivery of a prospectus (or in lieu thereof, the notice referred to in Rule 173(a) under the Act) is required in connection with the offering or sale of the Shares; to advise the Representative, promptly after it receives notice thereof, of the issuance by the Commission of any stop order or of any order preventing or suspending the use of any Preliminary Prospectus or other prospectus in respect of the Shares, of the suspension of the qualification of the Shares for offering or sale in any jurisdiction, of the initiation or threatening of any proceeding for any such purpose, or of any request by the Commission for the amending or supplementing of the Registration Statement or the Prospectus or for additional information; and, in the event of the issuance of any stop order or of any order preventing or suspending the use of any Preliminary Prospectus or other prospectus or suspending any such qualification, to promptly use its best efforts to obtain the withdrawal of such order;

(b) Promptly from time to time to take such action as the Representative may reasonably request to qualify the Shares for offering and sale under the securities laws of such jurisdictions as the Representative may request and to comply with such laws so as to permit the continuance of sales and dealings therein in such jurisdictions for as long as may be necessary to complete the distribution of the Shares, provided that in connection therewith the Company shall not be required to qualify as a foreign corporation, to file a general consent to service of process in any jurisdiction or to take any action that would subject it to general service of process in any jurisdiction where it is not presently qualified;

(c) [Reserved];

(d) On the New York Business Day immediately following the date of this Agreement, or as soon as is reasonably practicable thereafter, and from time to time thereafter, to furnish the Underwriters with printed and electronic copies of the Prospectus in New York City in such quantities as the Representative may reasonably request, and, if the delivery of a prospectus (or in lieu thereof, the notice referred to in Rule 173(a) under the Act) is required under law at any time prior to the expiration of nine months after the time of issue of the Prospectus in connection with the offering or sale of the Shares and if at such time any event shall have occurred as a result of which the Prospectus as then amended or supplemented would include an 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 when such Prospectus (or in lieu thereof, the notice referred to in Rule 173(a) under the Act) is delivered, not misleading, or, if for any other reason it shall be necessary during such same period to amend or supplement the Prospectus or to file under the Exchange Act any document incorporated by reference in the Prospectus in order to comply with the Act or the Exchange Act, to notify the Representative and upon the Representative’s request to file such document and to prepare and furnish without charge to each Underwriter and to any dealer in securities as many written and electronic copies as the Representative may from time to time reasonably request of an amended Prospectus or a supplement to the Prospectus which will correct such statement or omission or effect such compliance; and in case any Underwriter is required to deliver a prospectus (or in lieu thereof, the notice referred to in Rule 173(a) under the Act) in connection with sales of any of the Shares at any time nine months or more after the time of issue of the Prospectus, upon the Representative’s request but at the expense of such Underwriter, to prepare and deliver to such Underwriter as many written and electronic copies as the Representative may request of an amended or supplemented Prospectus complying with Section 10(a)(3) of the Act;

(e) To make generally available to its security holders as soon as practicable, but in any event not later than sixteen months after the effective date of the Registration Statement (as defined in Rule 158(c) under the Act), an earnings statement of the Company (which need not be audited) complying with Section 11(a) of the Act and the rules and regulations of the Commission thereunder (including, at the option of the Company, Rule 158);

(f) During the period beginning from the date hereof and continuing to and including the date 90 days after the date of the Prospectus (the “Lock-up Period”), not to (i) offer, sell, contract to sell, pledge, grant any option to purchase, make any short sale or otherwise transfer or dispose of, directly or indirectly, or file with the Commission a registration statement under the Act relating to, any securities of the Company that are substantially similar to the Shares, including but not limited to any options or warrants to purchase shares of Stock or any securities that are convertible into or exchangeable for, or that represent the right to receive, Stock or any such substantially similar securities, or publicly disclose the intention to make any offer, sale, pledge, disposition or filing or (ii) enter into any swap or other agreement that transfers, in whole or in part, any of the economic consequences of ownership of the Stock or any such other securities, whether any such transaction described in clause (i) or (ii) above is to be settled by delivery of Stock or such other securities, in cash or otherwise (other than the Shares to be sold hereunder or pursuant to employee stock option plans existing on, or upon the conversion or exchange of convertible or exchangeable securities outstanding as of, the date of this Agreement), without the prior written consent of the Representative; provided, however, that the Company may (A) effect the transactions contemplated hereby, (B) issue Stock or options to purchase Stock, or issue Stock upon exercise of options, pursuant to any equity incentive plans or employee stock purchase described in the Registration Statement, the Pricing Prospectus and the Prospectus, (C) file a Registration Statement on Form S-8 relating to the Stock granted pursuant to or reserved for issuance under any stock-based compensation plans of the Company and (D) enter into an agreement providing for the sale or issuance by the Company of, and sell or issue, Stock or Related Securities exercisable or exchangeable for, or convertible into, a number of shares of Stock, of not more than 5%, in aggregate, of the total number of shares of Stock issued and outstanding immediately following the completion of the transactions contemplated by this Agreement, pursuant to one or more strategic collaborations, licensing transactions or business, product or technology acquisitions (but excluding transactions principally of a financing nature), without the prior written consent of the Representative (which consent may be withheld in its sole discretion); provided, however, that any such issuances under clause (D) above shall be conditioned upon the execution by each recipient of such Stock or Related Securities of a lock-up agreement with the Underwriters prohibiting transfers of such Shares or Related Securities during the remainder of the Lock-up Period in the form of Exhibit B hereto. Notwithstanding the foregoing restrictions, during the Lock-up Period, the Company shall be permitted to keep in effect the Controlled Equity Offering^SM sales agreement, dated June 12, 2015, by and between the Company and Cantor Fitzgerald & Co. (the “ATM Sales Agreement”), and the prospectus supplement to the Base Prospectus included in the Registration Statement related thereto, provided that any sales of shares of Stock under the ATM Sales Agreement shall only be made after the period ending 60 days after the date of the Prospectus. For purposes of the foregoing, “Related Securities” shall mean any options or warrants or other rights to acquire Stock or any securities exchangeable or exercisable for or convertible into Stock, or to acquire other securities or rights ultimately exchangeable or exercisable for, or convertible into, Stock.

(g) If the Company elects to rely upon Rule 462(b), the Company shall file a Rule 462(b) Registration Statement with the Commission in compliance with Rule 462(b) by 10:00 p.m., Washington, D.C. time, on the date of this Agreement, and the Company shall at the time of filing either pay the Commission the filing fee for the Rule 462(b) Registration Statement or give irrevocable instructions for the payment of such fee pursuant to Rule 111(b) under the Act;

(h) [Reserved];

(i) To use the net proceeds received by it from the sale of the Shares in the manner specified in the Pricing Prospectus under the caption “Use of Proceeds”; and

(j) To use its best efforts to list for quotation, subject to official notice of issuance, the Shares on The NASDAQ Global Market (“NASDAQ”).

(k) To promptly notify the Representative 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 Shares within the meaning of the Act and (ii) completion of the 90-day restricted period referred to in Section 5(f) hereof.

6. (a) The Company represents and agrees that, without the prior consent of the Representative, it has not made and will not make any offer relating to the Securities that would constitute a “free writing prospectus” as defined in Rule 405 under the Act; each Underwriter represents and agrees that, without the prior consent of the Company and the Representative, it has not made and will not make any offer relating to the Securities that would constitute a free writing prospectus; any such free writing prospectus the use of which has been consented to by the Company and the Representative is listed on Schedule II(a) hereto;

(b) The Company represents and agrees that (i) it has not engaged in, or authorized any other person to engage in, any Section 5(d) Communications, other than Section 5(d) Communications with the prior consent of the Representative with entities that are qualified institutional buyers as defined in Rule 144A under the Act or institutions that are accredited investors as defined in Rule 501(a) under the Act; and (ii) it has not distributed, or authorized any other person to distribute, any Section 5(d) Writings, other than those distributed with the prior consent of the Representative that are listed on Schedule II(b) hereto; and the Company reconfirms that the Underwriters have been authorized to act on its behalf in engaging in Section 5(d) Communications

(c) The Company has complied and will comply with the requirements of Rule 433 under the Act applicable to any Issuer Free Writing Prospectus, including timely filing with the Commission or retention where required and legending;

(d) Each Underwriter represents and agrees that any Section 5(d) Communications undertaken by it were with entities that are qualified institutional buyers as defined in Rule 144A under the Act or institutions that are accredited investors as defined in Rule 501(a) under the Act; and

(e) The Company agrees that if at any time following issuance of an Issuer Free Writing Prospectus any event occurred or occurs as a result of which such Issuer Free Writing Prospectus would conflict with the information in the Registration Statement, the Pricing Prospectus or the Prospectus or would include an 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 then prevailing, not misleading, the Company will give prompt notice thereof to the Representative and, if requested by the Representative, will prepare and furnish without charge to each Underwriter an Issuer Free Writing Prospectus or other document which will correct such conflict, statement or omission; provided, however, that this representation and warranty shall not apply to any statements or omissions in an Issuer Free Writing Prospectus made in reliance upon and in conformity with information furnished in writing to the Company by an Underwriter (including through the Representative) expressly for use therein.

7. The Company covenants and agrees with the several Underwriters that the Company will pay or cause to be paid the following: (i) the fees, disbursements and expenses of the Company’s counsel and accountants in connection with the registration of the Shares under the Act and all other expenses in connection with the preparation, printing, reproduction and filing of the Registration Statement, the Base Prospectus, any Preliminary Prospectus, any Issuer Free Writing Prospectus and the Prospectus and amendments and supplements thereto and the mailing and delivering of copies thereof to the Underwriters and dealers; (ii) the cost of printing or producing this Agreement, closing documents (including any compilations thereof) and any other documents in connection with the offering, purchase, sale and delivery of the Shares; (iii) all expenses in connection with the qualification of the Shares for offering and sale under state securities laws as provided in Section 5(b) hereof, including the reasonable and documented fees and disbursements of counsel for the Underwriters in connection with such qualification and in connection with the Blue Sky survey(s) (not to exceed $5,000); (iv) any filing fees incident to, and the reasonable and documented fees and disbursements of counsel for the Underwriters in connection with, any required reviews by the Financial Industry Regulatory Authority, Inc. of the terms of the sale of the Shares in an amount not to exceed $15,000; (v) the cost of preparing certificates for the Shares; (vi) the cost and charges of any transfer agent or registrar or dividend disbursing agent; (vii) all fees and expenses in connection with listing the Shares on NASDAQ; (viii) any transfer or other taxes payable upon or related to the transfer and delivery of the Shares to the Underwriters; and (ix) all other costs and expenses incident to the performance of its obligations hereunder which are not otherwise specifically provided for in this Section. It is understood, however, that, except as provided in this Section, and Sections 9 and 12 hereof, the Underwriters will pay all of their own costs and expenses, including the fees of their counsel, transfer taxes on resale of any of the Shares by them, and any advertising expenses connected with any offers they may make.

8. The obligations of the Underwriters hereunder, as to the Shares to be delivered at each Time of Delivery, shall be subject, in their discretion, to the condition that all representations and warranties and other statements of the Company herein are, at and as of such Time of Delivery, true and correct, the condition that the Company shall have performed all of its obligations hereunder theretofore to be performed, and the following additional conditions:

(a) The Prospectus shall have been filed with the Commission pursuant to Rule 424(b) under the Act within the applicable time period prescribed for such filing by the rules and regulations under the Act and in accordance with Section 5(a) hereof; all 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 period prescribed for such filings by Rule 433; if the Company has elected to rely upon Rule 462(b) under the Act, the Rule 462(b) Registration Statement shall have become effective by 10:00 p.m., Washington, D.C. time, on the date of this Agreement; no stop order suspending the effectiveness of the Registration Statement or any part thereof shall have been issued and no proceeding for that purpose shall have been initiated or threatened by the Commission; no stop order suspending or preventing the use of the Prospectus or any Issuer Free Writing Prospectus shall have been initiated or threatened by the Commission; and all requests for additional information on the part of the Commission shall have been complied with to the Representative’s reasonable satisfaction;

(b) Davis Polk & Wardwell LLP, counsel for the Underwriters, shall have furnished to the Representative such written opinion or opinions, dated such Time of Delivery, with respect to such matters as the Representative may reasonably request, and such counsel shall have received such papers and information as they may reasonably request to enable them to pass upon such matters;

(c) Latham & Watkins LLP, counsel for the Company, shall have furnished to the Representative their written opinion and negative assurance letter, dated such Time of Delivery, in the form and substance reasonably satisfactory to the Representative;

(d) On the date of the Prospectus at a time prior to the execution of this Agreement, at 9:30 a.m., New York City time, on the effective date of any post-effective amendment to the Registration Statement filed subsequent to the date of this Agreement and also at each Time of Delivery, Ernst & Young LLP shall have furnished to the Representative a letter or letters, dated the respective dates of delivery thereof, in form and substance satisfactory to the Representative;

(e) In the judgment of the Representative, there shall not have occurred any material adverse change, or any development that could reasonably be expected to result in a material adverse change, in the condition (financial or otherwise), earnings, business, properties, operations or prospects, whether or not arising from transactions in the ordinary course of business, of the Company except as otherwise set forth in the Pricing Prospectus provided to prospective purchasers of Shares.

(f) [Reserved];

(g) [Reserved];

(h) [Reserved];

(i) The Shares at each Time of Delivery shall have been duly listed for quotation on NASDAQ, subject, in the case of the First Time of Delivery, to official notice of issuance;

(j) The Company shall have complied with the provisions of Section 5(c) hereof with respect to the furnishing of prospectuses on the New York Business Day immediately following the date of this Agreement, or as soon as reasonably practicable thereafter;

(k) The Company shall have furnished or caused to be furnished to the Representative at such Time of Delivery certificates of officers of the Company satisfactory to the Representative as to the accuracy of the representations and warranties of the Company herein at and as of such Time of Delivery, as to the performance by the Company of all of its obligations hereunder to be performed at or prior to such Time of Delivery, as to the matters set forth in subsections (a) and (e) of this Section and as to such other matters as the Representative may reasonably request;

(l) [Reserved];

(m) Prior to the date of this Agreement, the Representative shall have received an agreement substantially in the form of Exhibit B hereto signed by each of the persons listed in Exhibit A hereto; and

(n) The Company shall have furnished or caused to be furnished to the Representative at such Time of Delivery satisfactory evidence of the good standing of the Company in the State of Delaware and its good standing as a foreign entity in the State of California, in each case in writing or any standard form of telecommunication from the appropriate governmental authorities of such jurisdictions.

9. (a) The Company will indemnify and hold harmless each Underwriter against any losses, claims, damages or liabilities, joint or several, to which such Underwriter may become subject, under the Act or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon an untrue statement or alleged untrue statement of a material fact contained in the Registration Statement, the Base Prospectus, any Preliminary Prospectus, the Pricing Prospectus or the Prospectus, or any amendment or supplement thereto, any Issuer Free Writing Prospectus or any “issuer information” filed or required to be filed pursuant to Rule 433(d) under the Act, or any Section 5(d) Writing, 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 will reimburse each Underwriter for any legal or other expenses reasonably incurred by such Underwriter in connection with investigating or defending any such action or claim as such expenses are incurred; provided, however, that the Company shall 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 an untrue statement or alleged untrue statement or omission or alleged omission made in the Registration Statement, the Base Prospectus, any Preliminary Prospectus, the Pricing Prospectus or the Prospectus, or any amendment or supplement thereto, or any Issuer Free Writing Prospectus, or any Section 5(d) Writing, in reliance upon and in conformity with written information furnished to the Company by any Underwriter (including through the Representative) expressly for use therein.

(b) Each Underwriter will indemnify and hold harmless the Company, each officer who signed the Registration Statement and each of its directors against any losses, claims, damages or liabilities to which the Company may become subject, under the Act or otherwise, insofar as such losses, claims, damages or liabilities (or actions in respect thereof) arise out of or are based upon an untrue statement or alleged untrue statement of a material fact contained in the Registration Statement, the Base Prospectus, any Preliminary Prospectus, the Pricing Prospectus or the Prospectus, or any amendment or supplement thereto, or any Issuer Free Writing Prospectus, or any Section 5(d) Writing, 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, in each case to the extent, but only to the extent, that such untrue statement or alleged untrue statement or omission or alleged omission was made in the Registration Statement, the Base Prospectus, any Preliminary Prospectus, the Pricing Prospectus or the Prospectus, or any amendment or supplement thereto, any Issuer Free Writing Prospectus, or any Section 5(d) Writing, in reliance upon and in conformity with written information furnished to the Company by such Underwriter (including through the Representative) expressly for use therein; and will reimburse the Company, or any such director or officer, for any legal or other expenses reasonably incurred by the Company, or any such director or officer, in connection with investigating or defending any such action or claim as such expenses are incurred.

(c) Promptly after receipt by an indemnified party under subsection (a) or (b) above of notice of the commencement of any action, such indemnified party shall, if a claim in respect thereof is to be made against the indemnifying party under such subsection, notify the indemnifying party in writing of the commencement thereof; but the omission so to notify the indemnifying party shall not relieve the indemnifying party from any liability which it may have to any indemnified party otherwise than under such subsection to the extent the indemnifying party is not materially prejudiced as a proximate result of such failure and shall not in any event relieve the indemnifying party from any liability that it may have otherwise than on account of this indemnity agreement. In case any such action is brought against any indemnified party and it shall notify the indemnifying party of the commencement thereof, the indemnifying party shall be entitled to participate therein and, to the extent that it wishes, jointly with any other indemnifying party similarly notified, by written notice delivered to the indemnified party promptly after receiving the aforesaid notice from such indemnified party, to assume the defense thereof, with counsel reasonably satisfactory to such indemnified party; provided, however, that if the defendants in any such action include both the indemnified party and the indemnifying party and the indemnified party shall have reasonably concluded that a conflict may arise between the positions of the indemnifying party and the indemnified

party in conducting the defense of any such action or 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, the indemnified party or parties shall have the right to select separate counsel to assume such legal defenses and to otherwise participate in the defense of such action on behalf of such indemnified party or parties. Upon receipt of notice from the indemnifying party to such indemnified party of such indemnifying party’s election to assume the defense of such action, the indemnifying party shall not be liable to such indemnified party under such subsection for any legal expenses of other counsel or any other expenses, in each case subsequently incurred by such indemnified party, in connection with the defense thereof unless (i) the indemnified party shall have employed separate counsel in accordance with the proviso to the preceding sentence (it being understood, however, that the indemnifying party shall not be liable for the fees and expenses of more than one separate counsel (together with local counsel), representing the indemnified parties who are parties to such action), which counsel (together with any local counsel) for the indemnified parties shall be selected by the Representative (in the case of counsel for the indemnified parties referred to in Section 9(a) above) or by the Company (in the case of counsel for the indemnified parties referred to in Section 9(b) above)) or (ii) the indemnifying party shall not have employed counsel satisfactory to the indemnified party to represent the indemnified party within a reasonable time after notice of commencement of the action or (iii) the indemnifying party has authorized in writing the employment of counsel for the indemnified party at the expense of the indemnifying party, in each of which cases the reasonable fees and expenses of counsel shall be at the expense of the indemnifying party and shall be paid as they are incurred. The indemnifying party under this Section 9 shall not be liable for any settlement of any proceeding effected without its written consent, but if settled with such consent or if there be a final judgment for the plaintiff, the indemnifying party agrees to indemnify the indemnified party against any loss, claim, damage, liability or expense by reason of such settlement or judgment. Notwithstanding the foregoing sentence, if at any time an indemnified party shall have requested an indemnifying party to reimburse the indemnified party for fees and expenses of counsel as contemplated by this Section 9(c), the indemnifying party shall be liable for any settlement of any proceeding effected without its written consent if (i) such settlement is entered into more than 30 days after receipt by such indemnifying party of the aforesaid request and (ii) such indemnifying party shall not have reimbursed the indemnified party in accordance with such request prior to the date of such settlement. No indemnifying party shall, without the written consent of the indemnified party, effect the settlement or compromise of, or consent to the entry of any judgment with respect to, any pending or threatened action or claim in respect of which indemnification or contribution may be sought hereunder (whether or not the indemnified party is an actual or potential party to such action or claim) unless such settlement, compromise or judgment (i) includes an unconditional release of the indemnified party from all liability arising out of such action or claim and (ii) does not include any statement as to or an admission of fault, culpability or a failure to act, by or on behalf of any indemnified party.

(d) If the indemnification provided for in this Section 9 is unavailable to or insufficient to hold harmless an indemnified party under subsection (a) or (b) above in respect of any losses, claims, damages or liabilities (or actions in respect thereof) referred to therein, then each indemnifying party shall contribute to the amount paid or payable by such indemnified party as a result of such losses, claims, damages, expenses or liabilities (or actions in respect thereof) in such proportion as is appropriate to reflect the relative benefits received by the Company on the one hand and the Underwriters on the other from the offering of the Shares. If, however, the allocation provided by the immediately preceding sentence is not permitted by applicable law or if the indemnified party failed to give the notice required under subsection (c) above, then each indemnifying party shall contribute to such amount paid or payable by such indemnified party 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 the Underwriters on the other in connection with the statements or omissions which resulted in such losses, claims, damages or liabilities (or actions in respect thereof), as well as any other relevant equitable considerations. The relative benefits received by the Company on the one hand and the Underwriters on the other, in connection with the offering of Shares, shall be deemed to be in the same respective proportions as the total net proceeds from the offering (before deducting expenses) received by the Company bear to the total underwriting discounts and commissions received by the Underwriters, in each case as set forth in the table on the cover page of the Prospectus. The relative fault shall be determined by reference to, among other things, whether the untrue or alleged untrue statement of a material fact or the omission or alleged omission to state a material fact relates to information supplied by the Company on the one hand or the Underwriters on the other and the parties’ relative intent, knowledge, access to information and opportunity to correct or prevent such statement or omission. The Company and the Underwriters agree that it would not be just and equitable if contribution pursuant to this subsection (d) were determined by pro rata allocation (even if the Underwriters were treated as one entity for such purpose) or by any other method of allocation which does not take account of the equitable considerations referred to above in this subsection (d). The amount paid or payable by an indemnified party as a result of the losses, claims, damages or liabilities (or actions in respect thereof) referred to above in this subsection (d) shall be deemed to include any legal or other expenses reasonably incurred by such indemnified party in connection with investigating or defending any such action or claim. Notwithstanding the provisions of this subsection (d), no Underwriter shall be required to contribute any amount in excess of the amount by which the total price at which the Shares underwritten by it and distributed to the public were offered to the public exceeds the amount of any damages which such Underwriter has otherwise been required to pay by reason of such untrue or alleged untrue statement or omission or alleged omission. 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. The Underwriters’ obligations in this subsection (d) to contribute are several in proportion to their respective underwriting obligations and not joint.

(e) The obligations of the Company under this Section 9 shall be in addition to any liability which the Company may otherwise have and shall extend, upon the same terms and conditions, to each person, if any, who controls any Underwriter within the meaning of Section 15 of the Act or Section 20 of the Exchange Act and each broker-dealer affiliate of any Underwriter; and the obligations of the Underwriters under this Section 9 shall be in addition to any liability which the respective Underwriters may otherwise have and shall extend, upon the same terms and conditions, to each officer and director of the Company and to each person, if any, who controls the Company within the meaning of Section 15 of the Act or Section 20 of the Exchange Act.

10. (a) If any Underwriter shall default in its obligation to purchase the Shares that it has agreed to purchase hereunder at a Time of Delivery, the Representative may in its discretion arrange for the Representative or another party or other parties to purchase such Shares on the terms contained herein. If within thirty-six hours after such default by any Underwriter the Representative does not arrange for the purchase of such Shares, then the Company shall be entitled to a further period of thirty-six hours within which to procure another party or other parties satisfactory to the Representative to purchase such Shares on such terms. In the event that, within the respective prescribed periods, the Representative notifies the Company that it has so arranged for the purchase of such Shares, or the Company notifies the Representative that it has so arranged for the purchase of such Shares, the Representative or the Company shall have the right to postpone such Time of Delivery for a period of not more than seven days, in order to effect whatever changes may thereby be made necessary in the Registration Statement or the Prospectus, or in any other documents or arrangements, and the Company agrees to file promptly any amendments or supplements to the Registration Statement or the Prospectus which in your opinion may thereby be made necessary. The term “Underwriter” as used in this Agreement shall include any person substituted under this Section with like effect as if such person had originally been a party to this Agreement with respect to such Shares.

(b) If, after giving effect to any arrangements for the purchase of the Shares of a defaulting Underwriter or Underwriters by the Representative and the Company as provided in subsection (a) above, the aggregate number of such Shares which remains unpurchased does not exceed one-eleventh of the aggregate number of all the Shares to be purchased at such Time of Delivery, then the Company shall have the right to require each non-defaulting Underwriter to purchase the number of shares which such Underwriter agreed to purchase hereunder at such Time of Delivery and, in addition, to require each non-defaulting Underwriter to purchase its pro rata share (based on the number of Shares which such Underwriter agreed to purchase hereunder) of the Shares of such defaulting Underwriter or Underwriters for which such arrangements have not been made; but nothing herein shall relieve a defaulting Underwriter from liability for its default.

(c) If, after giving effect to any arrangements for the purchase of the Shares of a defaulting Underwriter or Underwriters by the Representative and the Company as provided in subsection (a) above, the aggregate number of such Shares which remains unpurchased exceeds one-eleventh of the aggregate number of all the Shares to be purchased at such Time of Delivery, or if the Company shall not exercise the right described in subsection (b) above to require non-defaulting Underwriters to purchase Shares of a defaulting Underwriter or Underwriters, then this Agreement (or, with respect to the Second Time of Delivery, the obligations of the Underwriters to purchase and of the Company to sell the Optional Shares) shall thereupon terminate, without liability on the part of any non-defaulting Underwriter or the Company, except for the expenses to be borne by the Company and the Underwriters as provided in Section 7 hereof and the indemnity and contribution agreements in Section 9 hereof; but nothing herein shall relieve a defaulting Underwriter from liability for its default.

11. The respective indemnities, agreements, representations, warranties and other statements of the Company and the several Underwriters, as set forth in this Agreement or made by or on behalf of them, respectively, pursuant to this Agreement, shall remain in full force and effect, regardless of any investigation (or any statement as to the results thereof) made by or on behalf of any Underwriter or any controlling person of any Underwriter, or the Company, or any officer or director or controlling person of the Company, and shall survive delivery of and payment for the Shares.

12. Prior to the First Time of Delivery, this Agreement may be terminated by the Representative by notice given to the Company if at any time: (i) a suspension or material limitation in trading in securities generally on the New York Stock Exchange or NASDAQ; (ii) a suspension or material limitation in trading in the Company’s securities on NASDAQ; (iii) a general moratorium on commercial banking activities declared by either Federal or New York State authorities or a material disruption in commercial banking or securities settlement or clearance services in the United States; (iv) the outbreak or escalation of hostilities involving the United States or the declaration by the United States of a national emergency or war or (v) the occurrence of any other calamity or crisis or any change in financial, political or economic conditions in the United States or elsewhere, if the effect of any such event specified in clause (iv) or (v) in the Representative’s reasonable judgment makes it impracticable or inadvisable to proceed with the public offering or the delivery of the Shares being delivered at such Time of Delivery on the terms and in the manner contemplated in the Pricing Prospectus and the Prospectus. If this Agreement shall be terminated pursuant to Section 10 or 12 hereof, the Company shall not then be under any liability to any Underwriter except as provided in Sections 7, 9 and 12 hereof; but, if for any reason other than the termination of this Agreement pursuant to Section 10, any Shares are not delivered by or on behalf of the Company as provided herein, the Company will reimburse the Underwriters through the Representative for all reasonable and documented out-of-pocket expenses approved in writing by the Representative, including reasonable and documented fees and disbursements of counsel, reasonably incurred by the Underwriters in making preparations for the purchase, sale and delivery of the Shares not so delivered, but the Company shall then be under no further liability to any Underwriter except as provided in Sections 7 and 9 hereof. For the avoidance of doubt, it is understood that the Company shall not pay or reimburse any costs, fees or expenses incurred by any Underwriter that defaults on its obligations to purchase Shares.

13. In all dealings hereunder, the Representative shall act on behalf of each of the Underwriters, and the parties hereto shall be entitled to act and rely upon any statement, request, notice or agreement on behalf of any Underwriter made or given by the Representative jointly or by the Representative on behalf of the Representative. All statements, requests, notices and agreements hereunder shall be in writing, and if to the Underwriters shall be delivered or sent by mail, telex or facsimile transmission to the Representative as the Representative in care of Leerink Partners, LLC, One Federal Street, 37^th Floor, Boston MA 02110, Attention: John I. Fitzgerald, Esq.; and if to the Company shall be delivered or sent by mail or electronic mail to OncoMed Pharmaceuticals, Inc., 800 Chesapeake Drive, Redwood City, California 94063, Attention: General Counsel, with a copy (which shall not constitute notice) to Latham & Watkins LLP, 140 Scott Drive, Menlo Park, California 94025, Facsimile: 650-463-2600, Attention: Alan C. Mendelson and Mark V. Roeder. Any such statements, requests, notices or agreements shall take effect upon receipt thereof.

In accordance with the requirements of the USA Patriot Act (Title III of Pub. L. 107-56 (signed into law October 26, 2001)), the Underwriters are required to obtain, verify and record information that identifies their respective clients, including the Company, which information may include the name and address of their respective clients, as well as other information that will allow the underwriters to properly identify their respective clients.

14. This Agreement shall be binding upon, and inure solely to the benefit of, the Underwriters, the Company and, to the extent provided in Sections 8 and 10 hereof, the officers and directors of the Company and each person who controls the Company or any Underwriter, and their respective heirs, executors, administrators, successors and assigns, and no other person shall acquire or have any right under or by virtue of this Agreement. No purchaser of any of the Shares from any Underwriter shall be deemed a successor or assign by reason merely of such purchase.

15. Time shall be of the essence of this Agreement. As used herein, the term “business day” shall mean any day when the Commission’s office in Washington, D.C. is open for business.

16. The Company acknowledges and agrees that (i) the purchase and sale of the Shares pursuant to this Agreement is an arm’s-length commercial transaction between the Company, on the one hand, and the several Underwriters, on the other, (ii) in connection therewith and with the process leading to such transaction each Underwriter is acting solely as a principal and not the agent or fiduciary of the Company, (iii) no Underwriter has assumed an advisory or fiduciary responsibility in favor of the Company with respect to the offering contemplated hereby or the process leading thereto (irrespective of whether such Underwriter has advised or is currently advising the Company on other matters) or any other obligation to the Company except the obligations expressly set forth in this Agreement and (iv) the Company has consulted its own legal and financial advisors to the extent it deemed appropriate.The Company agrees that it will not claim that the Underwriters, or any of them, has rendered advisory services of any nature or respect, or owes a fiduciary or similar duty to the Company, in connection with such transaction or the process leading thereto.

17. 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. This Agreement will inure to the benefit of and be binding upon the parties hereto, including any substitute Underwriters permitted by Section 10 hereof, and to the benefit of directors, officers, employees, agents referred to in Section 9 and in each case their respective successors, and no other person will have any right or obligation hereunder. The term “successors” shall not include any purchaser of the Shares as such from any of the Underwriters merely by reason of such purchase. This Agreement may be executed in two or more counterparts, each of which shall be an original, with the same effect as if the signatures thereto and hereto were upon the same instrument. This Agreement may not be amended or modified unless in writing by all of the parties hereto, and no condition herein (express or implied) may be waived unless waived in writing by each party whom the condition is meant to benefit.

18. THIS AGREEMENT AND ANY MATTERS RELATED TO THIS TRANSACTION SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK WITHOUT REGARD TO PRINCIPLES OF CONFLICT OF LAWS THAT WOULD RESULT IN THE APPLICATION OF ANY LAW OTHER THAN THE LAWS OF THE STATE OF NEW YORK. The Company agrees that any suit or proceeding arising in respect of this agreement or our engagement will be tried exclusively in the U.S. District Court for the Southern District of New York or, if that court does not have subject matter jurisdiction, in any state court located in The City and County of New York and the Company agrees to submit to the jurisdiction of, and to venue in, such courts.

19. The Company and each of the Underwriters hereby irrevocably waives, 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.

20. Notwithstanding anything herein to the contrary, the Company is authorized to disclose to any persons U.S. federal and state tax treatment and tax structure of the potential transaction and all materials of any kind (including tax opinions and other tax analyses) provided to the Company relating to that treatment and structure, without the Underwriters imposing any limitation of any kind. However, any information relating to the tax treatment and tax structure shall remain confidential (and the foregoing sentence shall not apply) to the extent necessary to enable any person to comply with securities laws. For this purpose, “tax structure” is limited to any facts that may be relevant to that treatment.

21. The invalidity or unenforceability of any section, paragraph, or provision of this Agreement shall not affect the validity or enforceability of any other section, paragraph of provision hereof. If any section, paragraph or provision of this Agreement is for any reason determined to be invalid or unenforceable, there shall be deemed to be made such minor changes (and only such minor changes) as are necessary to make it valid and enforceable.

22. Each of the parties hereto acknowledges that it is a sophisticated business person or entity who was adequately represented by counsel during negotiations regarding the provisions hereof and is fully informed regarding said provisions. Each of the parties hereto further acknowledges that the provisions of Section 9 hereof fairly allocate the risks in light of the ability of the parties to investigate the Company, its affairs and its business in order to assure that adequate disclosure has been made in the Registration Statement, any Base Prospectus, Pricing Prospectus, Prospectus or any free writing prospectus (and any amendments and supplements to the foregoing), as contemplated by the Act and Exchange Act.

If the foregoing is in accordance with your understanding, please sign and return to us a counterpart hereof, and upon the acceptance hereof by you, on behalf of each of the Underwriters, this letter and such acceptance hereof shall constitute a binding agreement between each of the Underwriters and the Company. It is understood that your acceptance of this letter on behalf of each of the Underwriters is pursuant to the authority set forth in a form of Agreement among Underwriters, the form of which shall be submitted to the Company for examination upon request, but without warranty on your part as to the authority of the signers thereof.

Very truly yours,
ONCOMED PHARMACEUTICALS, INC.
By:	/s/ Paul J. Hastings
	Name: Paul J. Hastings
	Title: Chairman and Chief Executive Officer

Accepted as of the date first written above: LEERINK PARTNERS LLC Acting as Representative of the several Underwriters named in the attached Schedule I
By:	/s/ John I. Fitzgerald, Esq.
	Name: John I. Fitzgerald, Esq.
	Title: Managing Director

SCHEDULE I

	Number of Firm Shares to be Purchased		Maximum Number of Optional Shares Which May be Purchased
Underwriter
Leerink Partners LLC		3,575,000		536,250
Wells Fargo Securities LLC		1,100,000		165,000
JMP Securities LLC		825,000		123,750
Total		5,500,000		825,000

SCHEDULE II

(a) Issuer Free Writing Prospectuses:

None.

(b) Section 5(d) Writings:

None.

Exhibit A

List of Lock-Up Signatories

Name	Title
Paul Hastings	Director, officer
John Lewicki	Officer
Sunil Patel	Officer
Jakob Dupont	Officer
Austin Gurney	Officer
Tim Hoey	Officer
Alicia Hager	Officer
Terry Gould	Director
Perry Karsen	Director
Jack Lasersohn	Director
Larry Lasky	Director
Deepa Pakianathan	Director
Jon Root	Director
Denise Scots-Knight	Director
Rick Winningham	Director
Michael Wyzga	Director
Adams Street Partners	Stockholder
US Venture Partners	Stockholder
Vertical Group	Stockholder
Delphi Ventures	Stockholder
Phase4 Ventures	Stockholder

A-1

Exhibit B

Form of Lock-Up

OncoMed Pharmaceuticals, Inc.

Lock-Up Agreement

August [•], 2016

Leerink Partners LLC

299 Park Avenue

21st Floor

New York, NY 10171

Re: OncoMed Pharmaceuticals, Inc. - Lock-Up Agreement

Ladies and Gentlemen:

The undersigned understands that you, as representative (the “Representative”), propose to enter into an Underwriting Agreement, on behalf of the several Underwriters named in Schedule I to such agreement (collectively, the “Underwriters”), with OncoMed Pharmaceuticals, Inc., a Delaware corporation (the “Company”), providing for a public offering of the Common Stock of the Company (the “Shares”) pursuant to a Registration Statement on Form S-3 filed with the Securities and Exchange Commission (the “SEC”).

In consideration of the agreement by the Underwriters to offer and sell the Shares, and of other good and valuable consideration the receipt and sufficiency of which is hereby acknowledged, the undersigned agrees that, during the period beginning from the date hereof and continuing to and including the date 90 days after the date of the final Prospectus covering the public offering of the Shares (the “Lock-Up Period”), subject to the exceptions set forth in this Lock-Up Agreement, the undersigned will not offer, sell, contract to sell, pledge, grant any option to purchase, make any short sale or otherwise dispose of any shares of Common Stock of the Company, or any options or warrants to purchase (collectively, “transfer”) any shares of Common Stock of the Company, or any securities convertible into, exchangeable for or that represent the right to receive shares of Common Stock of the Company, whether now owned or hereinafter acquired, owned directly by the undersigned (including holding as a custodian) or with respect to which the undersigned has beneficial ownership within the rules and regulations of the SEC (collectively the “Undersigned’s Shares”). Subject to the exceptions set forth in this Lock-Up Agreement, the foregoing restriction on transfer is expressly agreed to preclude the undersigned from engaging in any hedging or other transaction which is designed to or which reasonably could be expected to lead to or result in a sale or disposition of the Undersigned’s Shares even if such Shares would be disposed of by someone other than the undersigned. Such hedging or other transactions would include without limitation any short sale or any purchase, sale or grant of any right (including without limitation any put or call option) with respect to any of the Undersigned’s Shares or with respect to any security that includes, relates to, or derives any significant part of its value from such Shares.

B-1

Notwithstanding the foregoing, the undersigned may transfer the Undersigned’s Shares (A)(i) as a bona fide gift or gifts, or by will or intestate succession to the legal representative, heir, beneficiary or any immediate family of the undersigned, (ii) to any trust whose beneficiaries consist exclusively of one or more of the undersigned and/or the immediate family of the undersigned, (iii) to any corporation, partnership, limited liability company or other entity all of the beneficial ownership interests of which are held by the undersigned or any immediate family, (iv) as distributions to partners, members or stockholders of the undersigned, and (v) by operation of law, including pursuant to a domestic order or a negotiated divorce settlement; provided that, (1) in any such case, each transferee or distributee agrees to be bound in writing by the restrictions set forth herein and (2) with respect to clauses (i) through (iii) only, prior to the expiration of the Lock-Up Period, no public disclosure or filing under the Exchange Act by any party to the transfer or distribution (donor, donee, transferor or transferee) shall be required or made voluntarily, reporting a reduction in beneficial ownership of Shares in connection with such transfer or distribution, (B) with the prior written consent of the Representative of the Underwriters or (C) if the undersigned is a corporation, the corporation may transfer the capital stock of the Company to any wholly-owned subsidiary of such corporation; provided, however, that in any such case, it shall be a condition to the transfer that the transferee execute an agreement stating that the transferee is receiving and holding such capital stock subject to the provisions of this Agreement and there shall be no further transfer of such capital stock except in accordance with this Lock-Up Agreement, and provided further that any such transfer shall not involve a disposition for value. For purposes of this Lock-Up Agreement, “immediate family” shall mean any relationship by blood, marriage or adoption, not more remote than first cousin.

Furthermore, notwithstanding the restrictions imposed by this Lock-Up Agreement, the undersigned may, without the prior written consent of the Representative, (i) exercise an option to purchase the Shares granted under any stock incentive plan or stock purchase plan of the Company, provided that the underlying Shares shall continue to be subject to the restrictions on transfer set forth in this Lock-Up Agreement, (ii) establish a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer of the Shares, provided that such plan does not provide for any transfers of Shares during the Lock-up Period, (iii) transfer or sell shares of Common Stock pursuant to any trading plan pursuant to Rule 10b5-1 under the Exchange Act that has been entered into by the undersigned prior to the date of this Lock-Up Agreement, provided that any filing required to be made under Section 16(a) of the Exchange Act as a result of such transfer or sale shall state that such transfer or sale is pursuant to a trading plan pursuant to Rule 10b5-1, and (iv) transfer or dispose of the Undersigned’s Shares acquired in the Offering or on the open market following the Offering, provided that no filing under the Exchange Act or other public announcement shall be required or shall be made voluntarily in connection with such transfer or disposition pursuant to this clause (iv) during the Lock-up Period.

[Notwithstanding anything herein to the contrary, in the event that the Representative releases any Shares held by executive officers, directors and/or 1% or greater stockholders of the Company from the lock-up restrictions described herein, the same percentage of Shares of the Company’s securities held by such persons that are so released from the lock-up restrictions shall be released with respect to the Shares held by the undersigned concurrently therewith; provided, however, that the Representative, on behalf of the underwriters, will not be obligated to release the undersigned from such lock-up restrictions unless the Representative, on behalf of the underwriters, has first released more than an aggregate of $500,000 of Shares (the value of such released Shares to be determined based on the closing price on the date that the applicable Shares are approved for release) from such lock-up restrictions. In the event that the undersigned is released from any of its obligations under this agreement prior to the expiration of the Lock-up Period (“Early Release”), the Representative shall provide written notice promptly, and in no event later than five (5) business days prior to the effective date of such Early Release, to the Company, and the Company will, in turn, notify the undersigned.]

B-2

The undersigned now has, and, except as contemplated by the third and fourth paragraphs of this Lock-Up Agreement, for the duration of this Lock-Up Agreement will have, good and marketable title to the Undersigned’s Shares, free and clear of all liens, encumbrances, and claims whatsoever. The undersigned also agrees and consents to the entry of stop transfer instructions with the Company’s transfer agent and registrar against the transfer of the Undersigned’s Shares except in compliance with the foregoing restrictions.

It is understood that, if (i) the Company notifies the Representative in writing that it does not intend to proceed with the Offering, (ii) the Underwriting Agreement relating to the Offering is not executed by August 31, 2016 or (iii) the Underwriting Agreement (other than the provisions thereof which survive termination) shall terminate or be terminated for any reason prior to payment for and delivery of the Shares to be sold thereunder, this Lock-Up Agreement shall immediately be terminated and the undersigned shall automatically be released from all of his or her obligations under this letter agreement.

The undersigned understands that the Company and the Underwriters are relying upon this Lock-Up Agreement in proceeding toward consummation of the offering. The undersigned further understands that this Lock-Up Agreement is irrevocable and shall be binding upon the undersigned’s heirs, legal representatives, successors, and assigns.

This Lock-Up Agreement shall be governed by, and construed in accordance with, the laws of the State of New York.

IF AN INDIVIDUAL:

        By:                                                                                                            

(duly authorized signature)

        Name:                                                                                                      

(please print full name)

Email Address:

Address:

    Very truly yours,

IF AN ENTITY:

(please print complete name of entity)

        By:                                                                                                            

(duly authorized signature)

        Name:                                                                                                      

(please print full name)

Email Address:

Address:

B-3