Data Supportive of Phase 2 Clinical Development Program Currently Underway

PRINCETON, NJ, USA | May 21, 2008 | Medarex, Inc. (Nasdaq: MEDX) announced today positive safety data from two Phase 1 trials that support the Phase 2 clinical development program of MDX-1100, a fully human monoclonal antibody that
targets CXCL10 (also known as IP-10), for the treatment of inflammatory diseases.

MDX-1100 could potentially treat diseases such as ulcerative colitis (UC) and rheumatoid arthritis (RA) by suppressing the inflammatory process characteristic of these diseases. Results from the Phase 1 trials were presented at the Digestive Disease Week (DDW), being held May 17-22, 2008 in San Diego. (Abstracts #704, #T1145 and #W1170)

A Phase 1 open-label pilot study was conducted to evaluate the safety (primary endpoint) and preliminary efficacy of escalating single doses of MDX-1100 in 11 patients with moderate to severe UC. This study demonstrated that single doses (ranging from 0.3 to 10.0 mg/kg) of MDX-1100 in patients with active UC were safe and well-tolerated. Four patients in the study had protocol-defined clinical responses, determined by the Ulcerative Colitis Disease Activity Index (UCDAI) which scores the frequency and the amount of bloody stool per day that is recorded in a patient diary, physician global assessment and the assessment of colon mucosal inflammation ascertained by endoscopy. None of the three serious adverse events reported in the study were considered drug related. (Abstract #704)

A separate Phase 1 double-blind, placebo-controlled study was conducted to determine safety and pharmacokinetics of escalating single doses (ranging from 0.01 to 10 mg/kg) of MDX-1100 in 50 healthy volunteers. MDX-1100 demonstrated dose-proportional pharmacokinetics, and a potential pharmacodynamic effect that signaled a decrease in the production of CXCL10 was observed at 10 mg/kg. There were no infusion reactions, and the drug was non-immunogenic. No serious adverse effects were observed in this study. The most common drug related adverse events were drowsiness, cough and shortness of breath. (Abstract #T1145)

"The safety and preliminary efficacy data from these Phase 1 studies provide the foundation for our recently initiated Phase 2 program with MDX-1100," said Geoffrey M. Nichol, Senior Vice President, Product Development of Medarex. "We are excited
with the Phase 2 program and look forward to the outcome of the proof-of-concept studies in ulcerative colitis and rheumatoid arthritis."

Additional studies presented at DDW demonstrated that CXCL10 induced expression of several pro-inflammatory molecules and that these CXCL10 inducible genes were upregulated in patients with ulcerative colitis. (Abstract #W1170)

About MDX-1100

MDX-1100 is a fully human antibody that targets CXCL10 (also known as IP-10), a chemokine expressed in association with multiple inflammatory disease indications such as rheumatoid arthritis, inflammatory bowel disease and multiple sclerosis.
Published data suggests that CXCL10 plays key roles in murine models of inflammatory bowel disease (IBD) and RA. Moreover, CXCL10 levels are increased in patients with these diseases. Phase 2 proof-of-concept clinical trials of MDX-1100 in ulcerative
colitis and rheumatoid arthritis have been initiated.

About Ulcerative Colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease of the colon and is characterized by inflammation and ulceration of the lining of the colon. Symptoms typically include bloody diarrhea and abdominal pain and in severe cases may require
colectomy. According to the Crohn’s & Colitis Foundation of America, it is estimated that there are up to approximately 500,000 Americans with ulcerative colitis.

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. 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 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 www.medarex.com.

Medarex Statement on Cautionary Factors

Except for the historical information presented herein, matters discussed herein relating to the development of MDX-1100 may constitute forward-looking statements, as defined by 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. Statements that are not historical facts, including statements preceded by, followed by, or that include the words "preliminary"; "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 the development of MDX-1100, 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 such 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.