OMED Oncomed Pharmaceuticals, Inc.

OncoMed Pharmaceuticals, Inc. (NASDAQ:OMED), a clinical-stage biopharmaceutical company focused on discovering and developing novel anti-cancer therapeutics, today announced that five posters will be presented at the upcoming American Association for Cancer Research (AACR) Annual Meeting to be held April 14-18, 2018, in Chicago. Among the presentations will be preclinical data for OncoMed’s novel anti-TIGIT (OMP-313M32) immuno-oncology program, which is currently in a Phase 1a single-agent clinical study. Preclinical data for OncoMed’s differentiated clinical-stage GITRL-Fc (OMP-336B11) program will also be featured. In addition, preclinical immuno-oncology data for OncoMed’s Wnt antagonist vantictumab (anti-FZD, OMP-18R5) in combination with immune checkpoint inhibitors will be presented.

Details on the poster presentations are provided below:

Poster 20; Abstract 70: Effect of aging on the antitumor activity of GITRL-FcSession: Tumor Biology, Dormancy and Aging: The Influential MicroenvironmentDate and Time: Sunday Apr 15, 2018 1:00 PM - 5:00 PMLocation: McCormick Place South, Exhibit Hall A, Poster Section 3

Poster 28; Abstract 1733: Wnt antagonists synergize with immune checkpoint inhibitors to enhance anti-tumor responsesSession: Immunology, Immune Responses to Therapies 2Date and Time: Monday Apr 16, 2018 8:00 AM - 12:00 PMLocation: McCormick Place South, Exhibit Hall A, Poster Section 32

Poster 18; Abstract 2726: In vitro functional activity of OMP-336B11, a GITRL-Fc fusion protein, on primary human immune cellsSession: Immunology, Immune Checkpoints 2Date and Time: Monday Apr 16, 2018 1:00 PM - 5:00 PMLocation: McCormick Place South, Exhibit Hall A, Poster Section 32

Poster 16; Abstract 3826: GITRL-Fc biomarker and mechanism study: GITRL-Fc reduces Treg frequency in tumors and requires effector function for inhibition of tumor growthSession: Immunology, Therapeutic Antibodies, Including Engineered Antibodies 3Date and Time: Tuesday Apr 17, 2018 8:00 AM - 12:00 PMLocation: McCormick Place South, Exhibit Hall A, Poster Section 34

Poster 22; Abstract 5627: Anti-TIGIT biomarker study: Inhibition of TIGIT induces loss of Tregs from tumors and requires effector function for tumor growth inhibition Session: Clinical Research, Therapeutic Antibodies, Including Engineered Antibodies 4Date and Time: Wednesday Apr 18, 2018 8:00 AM - 12:00 PMLocation: McCormick Place South, Exhibit Hall A, Poster Section 28

Following the presentations, the posters will be available on the Pipeline section of OncoMed’s website, www.oncomed.com.

Additional information on the meeting can be found on the AACR website www.aacr.org.

About OncoMed PharmaceuticalsOncoMed Pharmaceuticals is a clinical-stage biopharmaceutical company focused on discovering and developing novel anti-cancer therapeutics. OncoMed has internally discovered a broad pipeline of investigational drugs intended to address the fundamental biology driving cancer's growth, resistance, recurrence and metastasis. Anti-TIGIT (OMP-313M32), navicixizumab (anti-DLL4/VEGF bispecific, OMP-305B83), and rosmantuzumab (anti-RSPO3, OMP-131R10) are part of OncoMed's strategic alliance with Celgene Corporation. OncoMed is independently developing GITRL-Fc (OMP-336B11), as well as continuing to pursue new drug discovery research. For further information about OncoMed Pharmaceuticals, please see www.oncomed.com.

Investor Relations Contact:

Matthew BeckSolebury Troutmbeck@troutgroup.com(646) 378-2933