OMED Oncomed Pharmaceuticals, Inc.

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(a)    Name of Issuer:

Oncomed Pharmaceuticals, Inc. (the “Issuer”)

(b)    Address of Issuer’s Principal Executive Offices:

800 Chesapeake Drive

Redwood City, California 94063

(a)    Name of Person Filing:

HarbourVest Partners, LLC

Dover VII Associates LLC

Dover VII Associates L.P.

Dover Street VII L.P.

Dover Street VII L.P., Dover VII Associates L.P., Dover VII Associates LLC and HarbourVest Partners, LLC have entered into a Joint Filing Agreement, dated December 21, 2018, a copy of which is filed with this Schedule 13G as Exhibit 99.1.1, pursuant to which such reporting persons have agreed to file this statement jointly in accordance with the provisions of 13d-1(k)(1) under the Securities Exchange Act of 1934.

(b)    Address of Principal Business Office or, if none, Residence

The principal business office of each reporting person is One Financial Center, Boston, MA 02111.

(c)    Citizenship:

Reporting entities are all organized and exist under the laws of the State of Delaware.

(d)    Title of Class of Securities:

Common stock, par value $0.001 per share

(e)    CUSIP Number:

68234X102

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Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

(a)    Amount beneficially owned:

Consists of 1,941,098 shares of common stock owned directly by Dover Street VII, L.P. HarbourVest Partners, LLC (“HarbourVest”) is the Managing Member of Dover VII Associates LLC, which is the General Partner of Dover VII Associates L.P., which is the General Partner of Dover Street VII, L.P. Each of HarbourVest, Dover VII Associates LLC and Dover VII Associates L.P. may be deemed to have a beneficial interest in the shares held by Dover Street VII L.P.

Voting and investment power over the securities owned directly by Dover Street VII L.P. is exercised by the Investment Committee of HarbourVest. Each of HarbourVest, Dover VII Associates LLC and Dover VII Associates L.P. and the members of the HarbourVest Investment Committee disclaim beneficial ownership of the shares held directly by Dover Street VII L.P.

(b)    Percent of class:

5.02% (based on the Issuer’s aggregate of 38,630,145 shares of common stock outstanding as of October 31, 2018, as reported in the Issuer’s quarterly report on Form 10-Q, filed with the Securities and Exchange Commission on November 1, 2018.

(c)    Number of shares as to which the person has:

(i) Sole power to vote or to direct the vote:

Dover Street VII L.P. has the sole power to vote or to direct the vote of 1,941,098 shares of common stock.

(ii) Shared power to vote or to direct the vote:

HarbourVest, Dover VII Associates LLC and Dover VII Associates L.P. may be deemed to have shared power to vote or direct the vote of 1,941,098 shares of common stock. Each of HarbourVest, Dover VII Associates LLC and Dover VII Associates L.P. disclaim such beneficial ownership of such shares.

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(iii) Sole power to dispose or to direct the disposition:

Dover Street VII L.P. has the sole power to dispose or to direct the disposition of 1,941,098 shares of     common stock.

(iv) Shared power to dispose or to direct the disposition:

HarbourVest, Dover VII Associates LLC and Dover VII Associates L.P. may be deemed to have shared power to dispose or direct the disposition of 1,941,098 shares of common stock. Each of HarbourVest, Dover VII Associates LLC and Dover VII Associates L.P. disclaim such beneficial ownership of such shares.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following [ ]:

See item 4 above.

Not Applicable.

Not Applicable.

Not Applicable.

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under §240.14a–11.

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Signatures

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Date: December 21, 2018

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