Medarex, Inc. Release: Interim Ipilimumab (MDX-010) Phase II Trial Results Indicate Well-Tolerated, Extended Dosing With Preliminary Evidence That Immune Activation May Reduce Relapse In The Adjuvant Setting In Melanoma

PRINCETON, N.J., June 5 /PRNewswire-FirstCall/ -- Medarex, Inc. today announced interim data based on median follow-up of 12 months of extended dosing with ipilimumab (also known as MDX-010) indicated that the treatment regimen was generally well-tolerated in 25 patients with resected Stage IIIc or Stage IV melanoma treated with ipilimumab and a multi- peptide melanoma vaccine in the adjuvant setting. All patients have survived to date. The Phase II clinical trial results were presented by Jeffrey S. Weber, M.D., Ph.D., Chief of Oncology at the Keck School of Medicine at the University of Southern California at the 42nd Annual Meeting of the American Society of Clinical Oncology, June 2-6, 2006, in Atlanta, GA (Abstract #2510).

The Phase II clinical trial was designed to establish a dose and regimen of ipilimumab suitable for extended dose treatment and involved 25 patients with surgically resected Stage IIIc (10 patients) or Stage IV (15 patients) melanoma who received 3.0 mg/kg of ipilimumab continually every eight weeks, co-administered with a multi-peptide melanoma vaccine given 12 times over 12 months for up to one year. To date, all 25 patients are still living with 12 months of median follow-up, and six of the patients have relapsed.

Twelve of 25 patients experienced Grade II or Grade III colitis, rash or hypopituitarism events that are consistent with an immune-based mechanism of action due to ipilimumab mediated CTLA-4 blockade (also termed Inflammatory Breakthrough Events, or IBEs), and which have correlated, in short-term treatment of patients with advanced metastatic melanoma, with anti-tumor response. The IBEs induced by longer-term treatment were either reversible following discontinuation of treatment or did not require discontinuation of therapy. Eighteen patients (72%) were able to continue the therapy without discontinuation of treatment due to adverse events. To date, only two of 12 patients experiencing IBEs have relapsed, in comparison to four of 13 patients without IBEs, supporting a possible association between IBEs and anti-tumor response. Patients will continue to be followed to relapse.

"We are pleased to observe well-tolerated longer-term dosing with ipilimumab that is associated with some evidence of tolerable immune activation, with possible relapse prevention, in the adjuvant setting," said Donald L. Drakeman, President and CEO of Medarex. "We will continue to follow the patients to further evaluate relapse-free and survival durations with melanoma in this treatment setting, a setting that could considerably expand therapeutic opportunities for ipilimumab."

About ipilimumab

Ipilimumab (also known as 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. Medarex and Bristol-Myers Squibb are investigating the potential of ipilimumab to enable the immune systems of cancer patients to help suppress tumor growth. Ipilimumab is currently in two registrational studies as second-line therapy for metastatic melanoma under two separate Special Protocol Assessment (SPA) agreements with the Food and Drug Administration (FDA). One is a recently initiated monotherapy study that is expected to be completed this year, and the other is in combination with MDX-1379 (a melanoma peptide vaccine). A front-line dacarbazine combination registrational study is also expected to initiate this year. Ipilimumab is also involved in multiple Phase II clinical trials to investigate the product's potential activity in other tumor types, as well as in combination studies with chemotherapy, immunotherapy and vaccines. Further information regarding Medarex's ipilimumab program can be found in Medarex's public disclosure filings with the U.S. Securities and Exchange Commission (SEC).

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. Thirty-two of these therapeutic product candidates derived from Medarex technology are in human clinical testing or have had INDs submitted for such trials, with four of the most advanced product candidates currently in Phase III 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, 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 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, 2005 and subsequent Quarterly Reports on Form 10-Q. There can be no assurance that such development efforts will succeed or that 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.

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Medarex, Inc.

CONTACT: Laura S. Choi, Investor Relations, x2216, or Jean Mantuano,Corporate Communications, media, x2221, +1-609-430-2880

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