Medarex Announces Positive Data with MDX-010 and Dacarbazine Combination in Metastatic Melanoma Phase II Study Complete and Partial Response Data Presented at The American Society of

Clinical Oncology Annual Meeting

    PRINCETON, N.J., June 7 /PRNewswire-FirstCall/ -- Medarex, Inc. (Nasdaq:  
 MEDX) today announced that in a Phase II clinical study the overall response
 rate in metastatic melanoma patients treated with MDX-010 in combination with
 dacarbazine was 17.1%, or 6 of 35 patients, with the median duration of
 complete and partial responses ongoing at 167 days. One patient experienced an
 ongoing complete response of ten months duration, and five patients
 experienced partial responses with the longest ongoing response of over ten
 months duration. In addition, four patients with stable disease were observed.
 In a similar metastatic melanoma patient population, a recent study conducted
 by a third party showed that the response rate for dacarbazine treatment alone
 was 6.8% in 385 patients with a median duration of responses of 128 days.(1)
 The Medarex study was presented by Evan M. Hersh, M.D., of the Arizona Cancer
 Center, in the melanoma discussion session at the 40th Annual Meeting of the
 American Society of Clinical Oncology (ASCO), June 5-8, 2004, in New Orleans,
 LA. (Abstract #7511)
     In addition to the MDX-010 and dacarbazine treatment arm, 2 of 37
 patients, or 5.4%, treated with 3 mg/kg of MDX-010 alone experienced partial
 responses, which are ongoing at over five months and seven months in duration,
 respectively. Also, four patients experienced stable disease, the longest of
 which is currently approaching one year in duration.
     In the Phase II trial, patients were treated with 3mg/kg of MDX-010
 monthly for four months and were randomized to receive either MDX-010 alone or
 MDX-010 in combination with dacarbazine. Nine of 72 patients, or 12.5%, in the
 study reported Grade III or IV serious adverse events. The most common events
 that were consistent with an immune-based mechanism of action due to MDX-010
 mediated CTLA-4 blockade, now termed Autoimmune Breakthrough Events (ABEs),
 were diarrhea, rash and increased liver enzymes. With exception to one
 colectomy case due to treatment-resistant colitis complicated by a bacterial
 infection (combination treatment), one fatal outcome suggestive of
 dacarbazine-mediated acute liver toxicity (combination treatment), and one
 fatal outcome suggestive of a pulmonary embolism or acute cardiovascular event
 (monotherapy treatment), most ABEs resolved with treatment.
     "We are pleased with the complete and partial response data thus far,"
 said Donald L. Drakeman, President and CEO of Medarex. "We expect to closely
 monitor and review the duration of patient responses as we consider the
 further clinical development plans for this program."
     In the second half of 2004, Medarex expects to initiate a pivotal study
 with a separate MDX-010 treatment combination based on a peptide vaccine in
 metastatic melanoma, pending approval of a Special Protocol Assessment (SPA)
 application that was filed with the FDA. In addition, MDX-010 is being tested
 in a Phase II chemotherapy combination clinical trial for prostate cancer and
 is also being studied as a monotherapy in a Phase II clinical trial for breast
 cancer and a Phase I clinical trial for HIV.
     About MDX-010 and Melanoma
     MDX-010 is a fully human antibody against human CTLA-4, a molecule on T
 cells that is believed to be responsible for suppressing the immune response.
 Studies in mice have demonstrated that an antibody against CTLA-4 has the
 potential to strengthen the adaptive immune response against certain tumors,
 leading to the reduction of and, in some cases, the elimination of well-
 established tumors. In preclinical research, MDX-010 has been shown to enhance
 immune responses and prevent tumor growth.
     In a separate Phase II clinical study, 21% of 14 metastatic melanoma
 patients treated with a high dose of MDX-010 in combination with a gp100
 peptide vaccine experienced complete or partial responses. The two patients
 with complete responses and the one patient with a partial response still
 remain cancer-free for over twenty months. Data from this clinical study
 suggested that the development of durable complete and partial responses in
 patients with extensive metastatic disease was associated with the induction
 of some drug-related ABEs seen at higher doses; however, no unmanageable
 toxicities were observed.
     According to the American Cancer Society, cancer of the skin is the most
 common of all cancers. Melanoma accounts for about 4% of skin cancer cases,
 but it causes about 79% of skin cancer deaths. The American Cancer Society
 estimates that in 2004 there will be about 55,100 new cases of melanoma in the
 United States, and about 7,910 people will die of this disease.
     About Medarex
     Medarex is a biopharmaceutical company focused on the discovery and
 development of therapeutics to treat life-threatening and debilitating
 diseases. Medarex's UltiMAb Human Antibody Development System(R) is a unique
 combination of human antibody technologies that Medarex believes enables the
 rapid creation and development of fully human antibodies to a wide range of
 potential disease targets for therapeutic antibody products, including
 products for the treatment of cancer, inflammation, autoimmune and infectious
 diseases.  Medarex's product pipeline is based on a variety of therapeutic
 antibody products developed through the use of its UltiMAb(TM) technology.
 Medarex creates and develops fully human antibodies for itself and others,
 offering a full range of antibody related capabilities, including pre-clinical
 and clinical development supported by cGMP manufacturing services.  For more
 information about Medarex, visit its website at
     Except for the historical information presented herein, matters discussed
 herein 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 "potential";
 "believe"; "anticipate"; "intend"; "plan"; "expect"; "estimate"; "could";
 "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
 discovery and development, uncertainties related to the outcome of clinical
 trials, slower than expected rates of patient recruitment, unforeseen safety
 issues resulting from the administration of antibody products in patients,
 uncertainties associated with the collaborative process, uncertainties related
 to product manufacturing 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, 2003 and subsequent Quarterly Reports on Form 10-Q. There
 can be no assurance that such development efforts will succeed, that such
 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 Human Antibody Development
 System(R) are registered trademarks of Medarex, Inc. UltiMAbTM is a trademark
 of Medarex, Inc. All rights are reserved.
      (1) FDA Oncologic Drugs advisory Committee Briefing Material, dated May
          3, 2004.

SOURCE Medarex, Inc.

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