Interim Phase 1/2 Data of Ipilimumab in Prostate Cancer Presented at American Society of Clinical Oncology Annual Meeting

Update: Yervoy (ipilimumab) Now FDA Approved - March 25, 2011

PRINCETON, N.J., June 02, 2008 /PRNewswire-FirstCall/ -- Medarex, Inc. today announced interim results from a Phase 1/2 trial of ipilimumab, an investigational oncology immunotherapy, as monotherapy or in combination with radiotherapy in patients with metastatic castration resistant prostate cancer (mCRPC).

Data presented showed that ipilimumab monotherapy or in combination with radiotherapy was clinically active and generally well-tolerated. Preliminary evidence of anti-cancer activity showed that 21 percent of patients (7 of 33) experienced decreases in prostate-specific antigen (PSA) serum levels of over 50 percent, with median duration of PSA responses of 4.8 months. This included one patient treated at the highest dose with a complete response (measured by both PSA and RECIST criteria) ongoing over one year. Two additional patients had PSA reductions of more than 30 percent within 12 weeks of treatment. The interim results were described in an oral presentation by investigator Tomasz M. Beer, M.D., the Grover C. Bagby Endowed Chair for Prostate Cancer Research and Associate Professor of Medicine from Oregon Health & Science University Cancer Institute, at the annual meeting of the American Society of Clinical Oncology (ASCO) being held in Chicago. (Abstract #5004)

"These initial data in patients with metastatic castration resistant prostate cancer demonstrated preliminary anti-tumor activity, including durable response, and is suggestive of a safety profile at the optimal ipilimumab regimen similar to that observed in our melanoma program," said Geoffrey M. Nichol, MBChB, Senior Vice President of Product Development at Medarex. "Radiotherapy is routinely used for palliative treatment in patients with metastatic castration resistant prostate cancer and bone metastases, and these data encourage further exploration of the ability of tumor antigen release by radiotherapy to serve as an immune-supportive intervention in combination with ipilimumab as a potentially important treatment option for these patients."

The Phase 1/2 trial was conducted to evaluate the safety and preliminary anti-tumor activity of escalating doses of ipilimumab (3, 5 or 10 mg/kg) every three weeks for up to four doses, with and without a single dose of focal radiotherapy administered to target bone lesion(s) prior to the first dose of ipilimumab. The dose escalation portion of the trial enrolled 33 patients with mCRPC and with bone metastases. Additional patients are enrolling in the expansion cohort of 10mg/kg ipilimumab in combination with radiotherapy.

Adverse events related to ipilimumab in this study were generally manageable and consistent with those immune-related adverse events (irAEs) previously reported in other clinical trials of ipilimumab. Grade 3/4 adverse events included diarrhea/colitis (5 patients), rash (1 patient) and elevated liver enzymes (2 patients). No new patterns or frequency of adverse events emerged in patients receiving the combination of ipilimumab and radiotherapy.

About Ipilimumab

Ipilimumab is a fully human antibody that binds to CTLA-4 (cytotoxic T lymphocyte-associated antigen 4), a molecule on T-cells that plays a critical role in regulating natural immune responses. The absence or presence of CTLA- 4 can augment or suppress the immune system's T-cell response in fighting disease. Ipilimumab is designed to block the activity of CTLA-4, thereby sustaining an active immune response in its attack on cancer cells.

Comprehensive Clinical Trial Program for Ipilimumab

Bristol-Myers Squibb Company and Medarex remain committed to the development of ipilimumab. The companies also have ongoing Phase 2 studies in hormone-refractory prostate cancer and lung cancer as well as a Phase 3 study, to be initiated shortly, in adjuvant melanoma.

For further information about ipilimumab clinical trials, please visit www.clinicaltrials.gov.

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 Web site at www.medarex.com.

Medarex Statement on Cautionary Factors

Except for the historical information presented herein, matters discussed herein relating to the development of ipilimumab may constitute forward- looking statements, as defined in 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, such as statements preceded by, followed by or including the words "preliminary"; "suggest"; or "potential"; 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 ipilimumab, 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, 2007 and its quarterly reports on Form 10-Q. There can be no assurance that such development efforts will succeed or that 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.

CONTACT: Laura S. Choi, Investor Relations, +1-609-430-2880, x2216; orNichol Harber, Corporate Communications (media), +1-609-430-2880, x2214,both of Medarex, Inc.

Web site: http://www.medarex.com/http://www.asco.org/ASCO/Meetings/ASCO+Annual+Meeting/

Company News On-Call: http://www.prnewswire.com/comp/108265.html /

Ticker Symbol: (NASDAQ-NMS:MEDX)

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Posted: June 2008

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