Two Separate Clinical Studies Planned for Cancer and Inflammatory Disease

PRINCETON, NJ, USA | December 4, 2007 | Medarex, Inc. (Nasdaq: MEDX) announced today the allowance of two separate investigational new drug applications (IND) filed with the U.S. Food & Drug Administration (FDA) for MDX-1342, one for the treatment of chronic lymphocytic leukemia (CLL) and the other for rheumatoid arthritis. MDX-1342 is a fully human antibody that targets CD19, a molecule specifically expressed on normal B-cells and malignant B-cells in diseases such as CLL, acute lymphoblastic leukemia, follicular non-Hodgkins lymphoma, diffuse large B-cell lymphoma and mantle cell lymphoma.

The IND for the treatment of CLL is for an open-label, multi-dose, dose-escalation Phase I clinical trial for cancer that is expected to enroll up to 52 patients with relapsed or refractory CLL. This trial is designed to establish and evaluate the safety, tolerability and maximum tolerated dose, as well as preliminary pharmacodynamics and efficacy of MDX-1342.

The IND for the treatment of rheumatoid arthritis is for a randomized, single-dose, dose-escalation, placebo-controlled Phase I clinical trial that is expected to enroll up to 90 patients with rheumatoid arthritis. This trial is designed to evaluate the safety and tolerability profile of MDX-1342 and to
determine the dose range for B-cell depletion.

"We are pleased with the advancement of a new product candidate from Medarex’s proprietary pipeline into clinical trials," said Howard H. Pien, President and CEO of Medarex. "We look forward to the continued development of MDX-1342, which could provide new treatment options for a number of serious conditions."

About CD19 and MDX-1342

CD19 is a B-cell specific membrane protein that is broadly expressed during B-cell development, from the pro-B-cell to the early plasma cell stage.

Clinical studies have demonstrated that depleting monoclonal antibodies directed against CD20, another B-cell specific membrane protein that has a more restricted expression pattern than CD19 during B-cell development, are effective in treating rheumatoid arthritis and various B-cell malignancies, and show promise in treating other inflammatory diseases such as systemic lupus erythematosis and multiple sclerosis.

MDX-1342 is a fully human antibody that binds selectively to CD19 expressed on B-cells (without targeting stem cells or fully differentiated plasma cells, which lack CD19 expression) and induces the depletion and elimination of CD19-positive B-cells.

About Chronic Lymphocytic Leukemia

Chronic Lymphocytic Leukemia (CLL) is a cancer that affects B-cell lymphocytes, an important component of the immune system that helps the body fight infection or cancer. The American Cancer Society estimates that in 2007, approximately 15,340 new cases of chronic lymphocytic leukemia will occur in the United States, and approximately 4,500 people will die of the disease in 2007.

About Rheumatoid Arthritis

According to the American College of Rheumatology, more than two million Americans suffer from rheumatoid arthritis (RA), a chronic autoimmune disease that develops when certain cells of the immune system inappropriately attack healthy joint tissue, thereby causing swelling, inflammation and damage of joints, as well as systemic inflammation and damage of other tissues.

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 30 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 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(R), the Medarex logo and UltiMAb(R) are registered trademarks of Medarex, Inc. All rights are reserved.

SOURCE: Medarex, Inc.