OncoMed Pharmaceuticals Initiates Third Phase 1b Clinical Trial of First-in-Class WNT-Pathway-Targeting Antibody Vantictumab

OncoMed Pharmaceuticals Initiates Third Phase 1b Clinical Trial of
First-in-Class WNT-Pathway-Targeting Antibody Vantictumab (OMP-18R5) With
Nab-Paclitaxel (Abraxane(R)) and Gemcitabine in Stage IV Pancreatic Cancer

REDWOOD CITY, Calif., Dec. 4, 2013 (GLOBE NEWSWIRE) -- OncoMed
Pharmaceuticals, Inc. (Nasdaq:OMED), a clinical-stage company developing novel
therapeutics that target cancer stem cells (CSCs), or tumor-initiating cells,
today announced that it has started a Phase 1b clinical trial of its
first-in-class Wnt-pathway-targeting antibody vantictumab (OMP-18R5) in
combination with nab-paclitaxel (Abraxane^®) and gemcitabine in patients with
Stage IV pancreatic cancer. This trial is the third of three Phase 1b trials
for vantictumab initiated this year as part of OncoMed's collaboration with
Bayer Pharma AG. 

The multi-center Phase 1b clinical trial is a dose escalation study that will
evaluate safety of vantictumab in combination with Abraxane and gemcitabine
and determine a recommended Phase 2 dose for this combination regimen. Key
secondary and exploratory objectives include evaluation of the
pharmacokinetics (PK) of vantictumab, as well as the pharmacodynamics (PD) and
efficacy of this combination. Tumor tissue from patients will be used to
explore predictive biomarker hypotheses related to the efficacy of
vantictumab.

"Incidence of pancreatic cancer has been steadily rising.In spite of recent
advancements, metastatic pancreatic cancer represents a significant unmet
medical need and patients are in need of improved treatment options," said
Safi Shahda, M.D., Assistant Professor of Clinical Medicine at Indiana
University in Indianapolis, IN, and the Principal Investigator who treated the
first patient enrolled in this study. "By targeting cancer stem cells,
vantictumab has the potential to augment the clinical benefit of standard
chemotherapy in this disease setting.I am particularly excited by the
inclusion of biomarker measures in this Phase 1b trial of vantictumab with
Abraxane and gemcitabine, which will provide valuable information related to
the drug's mechanism of action."

The other investigators and clinical sites to participate in the trial are:
Jordan Berlin, M.D., Vanderbilt University, Nashville, TN; Steven Cohen, M.D.,
Fox Chase Cancer Center, Philadelphia, PA; Heinz-Josef Lenz, M.D., University
of Southern California, Los Angeles, CA, and Wells Messersmith, M.D.,
University of Colorado Cancer Center, Aurora, CO.

Dr. Jakob Dupont, Chief Medical Officer of OncoMed, commented, "The Wnt
signaling pathway is implicated to be central to cancer stem cells survival
and potentially a key therapeutic target in pancreatic cancer.Our Wnt pathway
targeting antibody, vantictumab, reveals impressive preclinical data efficacy
data in combination with gemcitabine and Abraxane in OncoMed's minimally
passaged patient-derived pancreatic cancer models.We are pleased to have this
Phase 1b trial underway and look forward to reporting data on the safety,
efficacy and biomarker data of the vantictumab-Abraxane-gemcitabine
combination in patients with late-stage pancreatic cancer."

This is the third Phase 1b clinical study of vantictumab in combination with
standard-of-care treatment initiated by OncoMed this year.Vantictumab plus
docetaxel is being evaluated in non-small cell lung cancer and vantictumab
combined paclitaxel is being studied in Her2-negative breast cancer.Interim
results for the single-agent first-in-human Phase 1a trial for vantictumab in
solid tumor patients were recently reported at the 2013 European Cancer
Congress (ECC 2013) in Amsterdam, NL in September 2013. Results from the
Phase 1a study showed that vantictumab is well tolerated with early evidence
of single-agent activity.Additionally, clinical biomarker data from the Phase
1a trial indicating PD modulation of the Wnt pathway by vantictumab were
presented at the AACR-NCI-EORTC International Conference on Molecular Targets
and Cancer Therapeutics in Boston, MA in October 2013.

"This pancreatic cancer trial is the third vantictumab Phase 1b study
initiated by OncoMed this year as part of the clinical development program
that we are advancing in partnership with Bayer," said Paul J. Hastings,
Chairman and Chief Executive Officer of OncoMed. "The clinical data from these
three trials will yield important clinical information about this novel
anti-cancer stem cell agent in the key solid tumor indications of non-small
cell lung, breast and pancreatic cancer and may also lead to an opt-in
decision by Bayer to take vantictumab into late-stage randomized clinical
trials."

About Vantictumab (OMP-18R5)

Vantictumab is a first-in-class antibody that has shown broad anti-CSC and
anti-tumor activity in patient-derived xenograft tumor models. Vantictumab
inhibits a key signaling pathway in cancer, the Wnt pathway. Specifically,
vantictumab selectively targets Frizzled receptors, which are activators of
Wnt signaling. Although vantictumab was originally identified by binding to
Frizzled7, the antibody selectively targets five different Frizzled receptors.
OncoMed is currently completing a Phase 1a study of vantictumab in patients
with advanced solid tumors. Preliminary data from this clinical trial were
presented at the European Cancer Conference (ECC 2013) in September 2013 in
Amsterdam, NL. Biomarker data for this Phase 1a trial were presented at the
AACR-NCI-EORTC International Conference on Molecular Targets and Cancer
Therapeutics in Boston, MA, in October 2013. Vantictumab is now being tested
in combination with standard-of-care chemotherapy in three Phase 1b clinical
trials in: 1) advanced NSCLC (vantictumab + docetaxel); 2) advanced
HER2-negative breast cancer (vantictumab + paclitaxel); and 3) advanced
pancreatic cancer (vantictumab + gemcitabine/Abraxane^®).Vantictumab is part
of OncoMed's collaboration with Bayer Pharma AG.

About Cancer Stem Cells

Cancer stem cells, or CSCs, are the subpopulation of cells in a tumor
responsible for driving growth and metastasis of the tumor. CSCs, also known
as tumor-initiating cells, exhibit certain properties which include the
capacity to divide and give rise to new CSCs via a process called self-renewal
and the capacity to differentiate or change into the other cells that form the
bulk of the tumor. Common cancer drugs target bulk tumor cells but have
limited impact on CSCs, thereby providing a path for recurrence of the tumor.
OncoMed's product candidates target CSCs by blocking self-renewal and driving
differentiation of CSCs toward a non-tumorigenic state, and also impact bulk
tumor cells. OncoMed believes its product candidates are distinct from the
current generations of chemotherapies and targeted therapies, and have the
potential to significantly impact cancer treatment and the clinical outcome of
patients with cancer.

About OncoMed Pharmaceuticals

OncoMed Pharmaceuticals is a clinical-stage company focused on discovering and
developing novel therapeutics targeting cancer stem cells. OncoMed has five
anti-cancer product candidates in clinical development, including demcizumab
(Anti-DLL4, OMP-21M18), OMP-59R5 (Anti-Notch2/3), OMP-52M51 (Anti-Notch1),
vantictumab (Anti-Fzd7, OMP-18R5), and OMP-54F28 (Fzd8-Fc), which target key
cancer stem cell signaling pathways including Notch and Wnt.OncoMed has two
other antibodies in preclinical development, Anti-DLL4/Anti-VEGF bispecific
and Anti-RSPO3, with Investigational New Drug filings planned for as early as
2014.OncoMed is also pursuing discovery of additional novel anti-CSC product
candidates. OncoMed has formed strategic alliances with Celgene Corporation,
Bayer Pharma AG and GlaxoSmithKline (GSK).Additional information can be found
at the company's website:www.oncomed.com.

Forward-Looking Statements

To the extent that statements contained in this press release are not
descriptions of historical facts regarding OncoMed Pharmaceuticals, they are
forward-looking statements reflecting the current beliefs and expectations of
management made pursuant to the safe harbor provisions of the Private
Securities Litigation Reform Act of 1995, including OncoMed's expectations
regarding the success of Phase 1b trials for vantictumab and the potential for
an opt-in decision by Bayer; the potential of vantictumab to improve patient
outcomes, particularly in pancreatic cancer patients; the potential for
development of predictive biomarkers for vantictumab, especially in pancreatic
cancer; the potential of OncoMed's product candidates to significantly impact
cancer treatment and the clinical outcome of patients with cancer; and the
timing of Investigational New Drug filings and clinical trials. Such
forward-looking statements involve substantial risks and uncertainties that
could cause OncoMed's clinical development programs, future results,
performance or achievements to differ significantly from those expressed or
implied by the forward-looking statements. Such risks and uncertainties
include, among others, the uncertainties inherent in the preclinical and
clinical development process; the risks and uncertainties of the regulatory
approval process; OncoMed's dependence on its collaboration partners,
including GSK and Bayer, for the funding of its partnered programs; OncoMed's
ability to raise capital to support the development of its unpartnered
programs; OncoMed's dependence on the development and marketing efforts of its
partners for the commercial success of its partnered product candidates;
OncoMed's reliance on third parties to conduct certain preclinical studies and
all of its clinical trials; OncoMed's reliance on single source third-party
contract manufacturing organizations to manufacture and supply its product
candidates; OncoMed's ability to validate, develop and obtain regulatory
approval for companion diagnostics; OncoMed's ability to achieve market
acceptance and commercial success of its product candidates once regulatory
approval is achieved; OncoMed's ability to discover, develop and commercialize
additional product candidates; the ability of competitors to discover, develop
or commercialize competing products more quickly or more successfully;
OncoMed's dependence on its Chairman and Chief Executive Officer, its Chief
Scientific Officer, its Chief Medical Officer and other key executives; risk
of third party claims alleging infringement of patents and proprietary rights
or seeking to invalidate OncoMed's patents or proprietary rights; and the
ability of OncoMed's proprietary rights to protect its technologies and
product candidates. OncoMed undertakes no obligation to update or revise any
forward-looking statements. For a further description of the risks and
uncertainties that could cause actual results to differ from those expressed
in these forward-looking statements, as well as risks relating to OncoMed's
business in general, see OncoMed's Prospectus filed with the Securities and
Exchange Commission on July 18, 2013 and OncoMed's Quarterly Report on Form
10-Q for the fiscal quarter ended September 30,2013, filed with the Securities
and Exchange Commission on November 13, 2013.

CONTACT: Investor Contact:
         OncoMed Pharmaceuticals
         Shari Annes
         Investor Relations
         (650) 888-0902
         shari.annes@oncomed.com
        
         Media Inquiries:
         BCC Partners
         Karen L. Bergman or
         Michelle Corral
         (650) 575-1509 or (415) 794-8662
         kbergman@bccpartners.com or
         mcorral@bccpartners.com

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