UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

(Amendment No.     )

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☐ Definitive Proxy Statement

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ONCOMED PHARMACEUTICALS, INC.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than The Registrant)

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NNNNNNNNNNNN  +  C 1234567890 Vote by Internet•Go to www.envisionreports.com/OMED•Or scan the QR code with your smartphone • Follow the steps outlined on the secure website IMPORTANT ANNUAL MEETING INFORMATION Notice of Internet Availability of Proxy MaterialsNNNNNNNNNNNNNNN000004MRASAMPLEDESIGNATION(IFANY) ADD1ADD2ADD3ADD4ADD5ADD6ENDORSEMENT_LINE______________SACKPACK_____________ 123456789012345 Vote by Internet•Go to www.envisionreports.com/OMED• Or scan the QR code with your smartphone•Follow the steps outlined on the secure website Important Notice Regarding the Availability of Proxy Materials for the Stockholders Meeting to be Held on June 1, 2017  Under Securities and Exchange Commission rules, you are receiving this notice that the proxy materials for the annual stockholders meeting are available on the Internet. Follow the instructions below to view the materials and vote online or request a copy. The items to be voted on and location of the annual meeting are on the reverse side. Your vote is important!  This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. We encourage you to access and review all of the important information contained in the proxy materials before voting. The proxy statement and Annual Report on Form 10-K are available at:  www.envisionreports.com/OMED • : Easy Online Access — A Convenient Way to View Proxy Materials and Vote When you go online to view materials, you can also vote your shares. Step 1: Go to www.envisionreports.com/OMED to view the materials. Step 2: Click on Cast Your Vote or Request Materials. Step 3: Follow the instructions on the screen to log in. Step 4: Make your selection as instructed on each screen to select delivery preferences and vote.  When you go online, you can also help the environment by consenting to receive electronic delivery of future materials.   Obtaining a Copy of the Proxy Materials – If you want to receive a copy of these documents, you must request one. There is no charge to you for requesting a copy. Please make your request for a copy as instructed on the reverse side on or before May 19, 2017 to facilitate timely delivery. 2NOT COY + 02KMLA

Notice of 2017 Annual Meeting of Stockholders The 2017 Annual Meeting of Stockholders of OncoMed Pharmaceuticals, Inc. will be held on June 1, 2017 at800 Chesapeake Drive, Redwood City, California 94063, at 8:00 a.m. Pacific Time. Proposals to be voted on at the meeting are listed below along with the Board of Directors’ recommendations. The Board of Directors recommends a vote FOR all nominees under Proposal 1 and FOR Proposal 2: 1. Election of three Class I directors to hold office until the 2020 annual meeting of stockholders: 01 Perry A. Karsen 02 Rick E Winningham 03 Michael S. Wyzga 2. Ratify the selection of Ernst & Young LLP as the company’s independent registered public accounting firm for the fiscal year ending December 31, 2017. PLEASE NOTE – YOU CANNOT VOTE BY RETURNING THIS NOTICE. To vote your shares you must vote online or request a paper copy of the proxy materials to receive a proxy card. If you wish to attend and vote at the meeting, please bring this notice with you. Directions to the OncoMed Pharmaceuticals, Inc. 2017 Annual Meeting of Stockholders, which will be held at 800 Chesapeake Drive, Redwood City, California 94063, are located at: http://www.oncomed.com/Contact.html Here’s how to order a copy of the proxy materials and select a future delivery preference: Paper copies: Current and future paper delivery requests can be submitted via the telephone, Internet or email options below. Email copies: Current and future email delivery requests must be submitted via the Internet following the instructions below. If you request an email copy of current materials you will receive an email with a link to the materials. PLEASE NOTE: You must use the number in the shaded bar on the reverse side when requesting a set of proxy materials. • Internet – Go to www.envisionreports.com/OMED. Click Cast Your Vote or Request Materials. Follow the instructions to log in and order a copy of the current meeting materials and submit your preference for email or paper delivery of future meeting materials. • Telephone – Call us free of charge at 1-866-641-4276 and follow the instructions to log in and order a paper copy of the materials by mail for the current meeting. You can also submit a preference to receive a paper copy for future meetings. • Email – Send email to investorvote@computershare.com with “Proxy Materials OncoMed Pharmaceuticals” in the subject line. Include in the message your full name and address, plus the number located in the shaded bar on the reverse, and state in the email that you want a paper copy of current meeting materials. You can also state your preference to receive a paper copy for future meetings. To facilitate timely delivery, all requests for a paper copy of the proxy materials must be received by May 19, 2017. 02KMLA