X0306 4 2018-04-24 0 0001302573 OncoMed Pharmaceuticals Inc OMED 0001553352 Lewicki John A. C/O ONCOMED PHARMACEUTICALS, INC. 800 CHESAPEAKE DRIVE REDWOOD CITY CA 94063 1 1 0 0 President & CEO Common Stock 2018-04-24 4 S 0 4557 2.6777 D 55418 D Common Stock 99388 I See Footnote Pursuant to a sell-to-cover election made by the Reporting Person at the time of the initial grant of the restricted stock units ("RSU") award, the shares were sold upon the vesting of restricted stock units solely to cover applicable withholding taxes. This transaction was executed in multiple trades in prices ranging from $2.612 to $2.682771, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote. Includes 45,625 RSUs. The Reporting Person is entitled to receive one (1) share of common stock of the issuer for each one (1) RSU upon the vesting thereof. The shares are held by John Allan Lewicki and Jenniffer Joan Lewicki, Trustees of the Lewicki Family Trust dated December 6, 2000. /s/ Alicia J. Hager, Attorney-in-Fact for John A. Lewicki 2018-04-26