UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K/A

(Amendment No. 1)

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): March 16, 2018

ONCOMED PHARMACEUTICALS, INC.

(Exact name of registrant as specified in its charter)

800 Chesapeake Drive

Redwood City, California 94063

(Address of principal executive offices, including Zip Code)

Registrant’s telephone number, including area code: (650) 995-8200

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Indicate by check mark whether the registrant is an emerging growth company as defined in as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company  ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act.  ☒

On March 19, 2018, OncoMed Pharmaceuticals, Inc. (the “Company”) filed a Current Report on Form 8-K (the “Original 8-K”) reporting that, on March 16, 2018, the Board of Directors of the Company appointed Yvonne Li, the Company’s Vice President, Finance, Controller and Administration, as the Company’s principal accounting officer and principal financial officer. In connection with this appointment, on March 18, 2018, the Compensation Committee of the Company’s Board of Directors (the “Compensation Committee”) approved the grant to Ms. Li of a stock option award to purchase 75,000 shares of the Company’s common stock, as described in the Original 8-K. At the time, Ms. Li’s compensation did not otherwise change.

This Current Report on Form 8-K/A amends the Original 8-K to include information regarding the following change in Ms. Li’s compensation in connection with her appointment as the Company’s principal accounting officer and principal financial officer: On June 21, 2018, the Compensation Committee approved an increase in Ms. Li’s annual bonus eligibility for 2018 to up to 35% of her base salary.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.