Medarex Reports Interim Data from Ongoing Ipilimumab Combination Phase 1 Studies in Prostate Cancer at American Association for Cancer Research Meeting

Medarex Reports Interim Data from Ongoing Ipilimumab Combination Phase 1 Studies in Prostate Cancer at American Association for Cancer Research Meeting
PRINCETON, N.J., April 15 /PRNewswire-FirstCall/ -- Medarex, Inc. (Nasdaq: MEDX)
announced today interim results from two ongoing Phase 1 trials in hormone
refractory prostate cancer (HRPC) demonstrating dose-dependent T-cell activation and
clinical activity of ipilimumab, an investigational anti-CTLA-4 antibody. These
studies were done in combination with antigen-releasing immunotherapies based on
GM-CSF, a cytokine that stimulates the proliferation of white blood cells and
augments immune responses, and results were presented in two separate oral
presentations by investigators at the Annual Meeting of the American Association for
Cancer Research (AACR), being held April 12-16, 2008 in San Diego.

    "The interim results demonstrating clinical activity in these ongoing trials
lend additional support to the concept of ipilimumab as part of a therapeutic
regimen in treating prostate cancer," said Geoffrey M. Nichol, M.B.Ch.B., Senior
Vice President of Product Development at Medarex. "We will continue to explore the
prospects of ipilimumab in HRPC, and we expect further data in prostate cancer for
ipilimumab monotherapy and in combination with other antigen-releasing agents at
this year's ASCO conference in June."

    -- "Dendritic and T cell functions in patients with metastatic
       hormone-refractory prostate cancer treated with GVAX immunotherapy for
       prostate cancer and ipilimumab" (Abstract #2538)

       Interim data from the ongoing Phase 1 study of escalating doses of
       ipilimumab in combination with the Cell Genesys, Inc. GVAX
       immunotherapy for prostate cancer (an investigational agent comprised
       of whole tumor cells modified to secrete GM-CSF) were presented by
       Saskia JAM Santegoets, Ph.D., from the Department of Medical Oncology
       and Pathology of Vrije Universiteit Medical Center located in
       Amsterdam, Netherlands. The data suggested an ipilimumab dose-related
       association with increased T-cell activation, as well as associated
       anti-tumor activity from the initial 12 patients that was previously
       reported at the June 2007 American Society of Clinical Oncology (ASCO)
       meeting.

       In the Phase 1 clinical trial, 28 patients with metastatic HRPC have
       been enrolled, including 12 patients in the dose-escalation cohort
       (0.3, 1, 3 or 5 mg/kg ipilimumab) and 16 patients in the expansion
       cohort (3 mg/kg ipilimumab). The dose of GVAX immunotherapy for
       prostate cancer used in this combination trial is comparable to that
       currently being evaluated in Cell Genesys' ongoing Phase 3 program. The
       treatment combination was generally well-tolerated. Adverse events
       associated with this regimen are consistent with data previously
       reported from this study.

    -- "CTLA-4 blockade for hormone refractory prostate cancer: dose-dependent
       induction of CD8+ T cell activation and clinical responses" (Abstract
       #2539)

       Preliminary data from an ongoing Phase 1 study of escalating doses of
       ipilimumab in combination with GM-CSF (sargramostim) were presented by
       Lawrence Fong, Ph.D., from the University of California, San Francisco,
       San Francisco. Of the six patients treated at 3 mg/kg ipilimumab, three
       experienced confirmed decreases in prostate-specific antigen (PSA)
       serum levels of over 50%, and one of these patients experienced a
       partial response in hepatic metastases.

       In the Phase 1 clinical trial, 26 patients with HRPC received treatment
       with a 28-day cycle of daily doses of 250 mg/m2 of GM-CSF for 14 days
       in combination with ipilimumab administered on the first day of the
       28-day cycle for up to four cycles. Ipilimumab dosing initially ranged
       from 0.5 mg/kg to 3 mg/kg. Additional patients are now being treated
       with higher doses (5 mg/kg and 10 mg/kg) of ipilimumab. The treatment
       combination was generally well-tolerated. Adverse events associated
       with ipilimumab treatment are consistent with data previously reported
       from this study and from other clinical trials of ipilimumab.

    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(R)
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. More than 40 of these
therapeutic product candidates derived from Medarex technology are in human clinical
testing or have had INDs submitted for such trials, with seven of the most advanced
product candidates currently in Phase 3 clinical trials or the subject of regulatory
applications for marketing authorization. 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
http://www.medarex.com.

    Medarex Statement on Cautionary Factors

    Except for the historical information presented herein, matters discussed herein
relating to the interim data from ongoing ipilimumab combination Phase 1 studies may
constitute forward-looking statements 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.
Statements that are not historical facts, including statements preceded by, followed
by, or that include the words "preliminary"; "interim"; "potential"; "may"; or
similar statements are forward-looking statements. Medarex disclaims, however, any
intent or obligation to update these forward-looking statements. Risks and
uncertainties include risks associated with product development, unforeseen safety
issues resulting from the administration of antibody products in humans, 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, 2007 and its quarterly reports on Form
10-Q. There can be no assurance that future milestone payments will be paid, whether
the product development efforts will succeed, or whether other 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(R), the Medarex logo and UltiMAb(R) are registered trademarks of
Medarex, Inc. All rights are reserved.

SOURCE  Medarex, Inc.
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    (MEDX)

CO:  Medarex, Inc.; Annual Meeting of the American Association for Cancer
     Research; AACR ST:  New Jersey, California IN:  MTC BIO HEA SU:  TRI TDS

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