Medarex Announces Efficacy Data in Cancer Patients Treated with Investigational Anti-PD-1 Antibody at American Society of Clinical Oncology Annual Meeting

-Phase 1 Single-Dose and Phase 1b Multi-Dose Data Presented-
PRINCETON, N.J.--(Business Wire)--
Medarex, Inc. (NASDAQ: MEDX) today announced anti-tumor activity and efficacy
data for MDX-1106 (also known as ONO-4538), a fully human anti-PD-1 antibody
that Medarex is co-developing with Ono Pharmaceutical Co. Ltd. for the treatment
of recurrent or treatment-refractory cancers, including malignant melanoma,
renal cell carcinoma, colorectal carcinoma, non-small cell lung cancer, and
castrate resistant prostate carcinoma. Results presented at the annual meeting
of the American Society of Clinical Oncology (ASCO) showed:

* Durable anti-tumor activity in patients treated with intermittent 10 mg/kg
dosing of MDX-1106 in the 21-patient expansion cohort from the Phase 1 trial,
including one patient with renal cell cancer experiencing an ongoing objective
partial response of over 9 months and one patient with melanoma experiencing
ongoing stable disease with marked clinical improvement for over 19 months and 9
doses of MDX-1106. One patient with colorectal carcinoma treated with five doses
at the earlier 3 mg/kg cohort has also maintained a partial response for over 20
months;
* All patients showing clinical benefit with MDX-1106 had previously progressed
after prior chemotherapies;
* None of the patients treated at 10 mg/kg have developed any significant
drug-related adverse events. MDX-1106 appeared to be well-tolerated at the 10
mg/kg dose, including those patients in the cohort eligible to receive between
two and nine doses of 10mg/kg MDX-1106; and
* No dose-limiting toxicities have been reached.

These data focused on the experience of an expansion cohort of 21 patients dosed
at 10 mg/kg of MDX-1106 from the single-dose Phase 1 trial and were presented by
investigator Julie Brahmer, M.D., Assistant Professor of Oncology from the
Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins University (Abstract
#3018). The complete study was designed to examine the safety, tolerability and
pharmacokinetic profile of single-dose MDX-1106 (0.3, 1, 3 or 10 mg/kg) in
patients with recurrent or treatment-refractory cancers. However, per protocol,
patients demonstrating clinical benefit could receive additional intermittent
doses (up to nine doses of 10 mg/kg MDX-1106) until an objective response was
obtained. In addition to the durable responses outlined above, lesional
regressions were observed in two additional patients, including one with
non-small cell lung cancer, and one with melanoma. Enrollment in the single-dose
Phase 1 trial is complete with 39 patients.

Also presented were preliminary data from an ongoing multi-dose, dose escalating
Phase 1b monotherapy study of MDX-1106. One patient with melanoma in the first
treatment cohort of 4 patients has demonstrated marked tumor regression of liver
and lung lesions after receiving four doses of 1 mg/kg of MDX-1106. The tumors
have continued to shrink after additional cycles of four doses, and the patient
continues to tolerate the treatment without adverse events. Additional
anti-tumor activity has been observed with lung lesion regression in a patient
with renal cell cancer. Subsequently observed in the second dose level cohort,
one patient with non-small cell lung cancer has demonstrated regression of a
solitary adrenal metastasis after the first 4 doses of 3 mg/kg of MDX-1106. The
trial is designed to examine the safety and activity in patients treated with
multiple doses of MDX-1106 (1, 3 and 10 mg/kg) administered every two weeks
until a confirmed complete response, clear progression or serious adverse event
emerges. This multi-center, open label study is expected to enroll up to 76
patients in the United States.

"We are encouraged by both the safety profile and the initial anti-tumor
activity that included durable responses in several cancer indications for
patients treated intermittently with MDX-1106 up to the 10 mg/kg dose. We are
also pleased by our ongoing Phase 1b study of repeated doses of the antibody
which has also shown early evidence of activity at a repeated dose of 1 or 3
mg/kg," said Geoffrey M. Nichol, MBChB, Senior Vice President of Product
Development at Medarex. "While we are still in early stages of development, it
is also exciting that these treatments continue to be generally well tolerated."

About MDX-1106/ONO-4538

MDX-1106/ONO-4538 is a novel fully human antibody designed to target and inhibit
the function of PD-1 (programmed cell death 1), a receptor expressed on the
surface of activated lymphocytes (T-cells). The binding of PD-1 with one of two
ligands (PD-L1 or PD-L2) is an important negative regulation pathway that
suppresses or inhibits activated lymphocytes. Recent research has noted
increased PD-1 expression levels on antigen specific T-cells in both the
oncology and chronic infectious disease settings, as well as a strong
correlation between increased PD-L1 expression on tumors and a negative survival
prognosis in cancer patients. Preclinical studies indicate that antibodies
targeting the PD-1 signaling pathway reinvigorate antigen-specific T-cell
responses and promote an immune response to fight tumors and infectious
diseases.

MDX-1106/ONO-4538 is being investigated in both the oncology and infectious
disease settings. In addition to the Phase 1b study in cancer, a Phase 1 trial
is ongoing for the treatment of hepatitis C. In September 2008, Ono initiated a
single and multi-dose Phase 1 clinical study in patients with advanced solid
malignancies in Japan. MDX-1106/ONO-4538 may also have the potential to be used
synergistically in combination with other treatment modalities, including with
anti-CTLA-4 blockade.

In May 2005, Ono entered into a collaboration agreement with Medarex to research
and develop a fully human anti-PD-1 antibody for the treatment of cancer. The
two companies plan to share the costs and responsibilities of research and
product development up to the completion of a Phase 2 clinical study in each
party`s territory. Thereafter, each company will be fully responsible for any
continued development and any commercialization in its exclusive territory;
Medarex`s exclusive territory is North America, and Ono`s exclusive territory is
all areas outside of North America.

About Medarex

Medarex is a biopharmaceutical company focused on the discovery, development and
potential commercialization of fully human antibody-based therapeutics to treat
life-threatening and debilitating diseases, including cancer, inflammation,
autoimmune disorders and infectious diseases. Medarex applies its UltiMAb®
technology and product development and clinical manufacturing experience to
generate, support and potentially commercialize a broad range of fully human
antibody product candidates for itself and its partners. Over forty of these
therapeutic product candidates derived from Medarex technology are in human
clinical testing or have had INDs submitted for such trials, with the most
advanced product candidates currently approved for commercial sale, the subject
of regulatory applications for marketing authorization or in Phase 3 clinical
trials. Medarex is committed to building value by developing a diverse pipeline
of antibody products to address the world`s unmet healthcare needs. For more
information about Medarex, visit its website at www.medarex.com.

Medarex Statement on Cautionary Factors

Except for the historical information presented herein, the statements relating
to MDX-1106 in this press release may constitute forward-looking statements, as
defined in the Private Securities Litigation Reform Act of 1995, that are
subject to certain risks and uncertainties that could cause actual results to
differ materially from any future results, performance or achievements expressed
or implied by such statements. Medarex disclaims, however, any intent or
obligation to update these forward-looking statements. Risks and uncertainties
include risks associated with product discovery and development of MDX-1106, as
well as risks detailed from time to time in Medarex`s public disclosure filings
with the U.S. Securities and Exchange Commission (SEC), including its Annual
Report on Form 10-K for the fiscal year ended December 31, 2008 and its
quarterly reports on Form 10-Q. There can be no assurance that such development
efforts will succeed or that developed products will receive required regulatory
clearance or that, even if such regulatory clearance were received, such
products would ultimately achieve commercial success. Copies of Medarex`s public
disclosure filings are available from its investor relations department.

Medarex, the Medarex logo and UltiMAb are registered trademarks of Medarex, Inc.
All rights are reserved.

Medarex, Inc.
Laura S. Choi
Investor Relations
Phone: 609-430-2880, x2216
or
Nichol Ochsner
Corporate Communications (media)
Phone: 609-430-2880, x2214

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