Progenics’ Humanized Monoclonal Antibodies Significantly Improve Survival in an Animal Model of C. difficile-associated Disease

Progenics Pharmaceuticals, Inc. (Nasdaq: PGNX) today presented preclinical findings for its humanized monoclonal antibodies against the disease-causing toxins produced by the bacterium Clostridium difficile (C. difficile). C. difficile is the leading cause of hospital-acquired diarrhea in the United States and represents a serious global public health challenge. In a well-established hamster model of C. difficile-associated disease (CDAD), treatment with Progenics’ antitoxin antibodies resulted in 95% survival versus 0% survival for standard antibiotic treatment. The data are being presented at the 50th annual Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in Boston, MA.

"Our novel antibodies represent a non-antibiotic treatment strategy that is designed to block the harmful effects of toxins A and B produced by C. difficile,” said William C. Olson, Ph.D., Senior Vice President, Research and Development at Progenics. "Our humanized antitoxin monoclonal antibodies provided potent and durable protection against CDAD in the study reported today, and these results were achieved without co-use of antibiotics. This new approach has the potential to treat severe cases of CDAD and to break the cycle of infection in patients with relapsed disease.”

Study Description and Summary of results

In the preclinical efficacy study, two humanized monoclonal antibodies (one against toxin A and the other against toxin B) were tested in combination. Hamsters were infected with C. difficile in the presence or absence of treatment with antitoxin antibodies or vancomycin, a current standard antibiotic therapy. Nineteen of twenty (95%) animals treated with antibodies survived until the end of the 40-day study. In contrast, none of the eight vancomycin-treated animals survived more than 22 days, and none of the eight control (untreated) animals survived more than three days. The survival advantage provided by antibody treatment was highly statistically significant (P<0.0001) relative to both the vancomycin and control groups.

The poster, entitled "Mechanistic Studies of Novel Monoclonal Antibodies against Clostridium difficile Toxins," is scheduled for presentation on Monday, September 13, 2010 by Andre J. Marozsan, Ph.D., Associate Director, Biologics Discovery, at Progenics Pharmaceuticals, Inc.

Presentation details are as follows:

About Clostridium difficile

Clostridium difficile (C. difficile) is an anaerobic, spore-forming bacterium that represents the leading cause of hospital-acquired diarrhea and life-threatening pseudomembranous colitis. C. difficile-associated disease (CDAD) affects an estimated 750,000 individuals each year in the U.S. and is responsible for more deaths than all other intestinal infections combined. Recent outbreaks of hypervirulent strains have been reported globally, significantly increasing the economic burden of CDAD and requiring new treatment strategies to combat this worldwide public health challenge.

Upon infection, C. difficile produces two protein toxins (toxins A and B) that can damage the cells that line the colon, leading to CDAD. CDAD encompasses a spectrum of diseases ranging from mild-to-severe diarrhea to potentially life-threatening complications such as toxic megacolon and sepsis. CDAD often occurs when an individual is exposed to C. difficile while taking antibiotics, since a course of antibiotic treatment can disrupt the normal (beneficial) intestinal bacteria, providing opportunities for C. difficile to become established. Current treatments for CDAD consist of narrow-spectrum antibiotics, such as vancomycin or metronidazole that may impede regrowth of the normal colonic bacteria. Although current therapies are generally effective in treating CDAD, the disease frequently relapses after antibiotic treatment ceases. Progenics’ monoclonal antibodies are designed to block the cytotoxic effects of C. difficile toxins and enable the normal bacteria in the colon to become re-established.

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About Progenics

Progenics Pharmaceuticals, Inc., of Tarrytown, NY, is a biopharmaceutical company focusing on the development and commercialization of innovative therapeutic products to treat the unmet medical needs of patients with debilitating conditions and life-threatening diseases. Principal programs are directed toward supportive care, oncology and infectious diseases. Progenics is developing RELISTOR^® (methylnaltrexone bromide) for the treatment of opioid-induced constipation. RELISTOR is now approved in over 50 countries, including the U.S., E.U., Canada, Australia and Brazil. Progenics is pursuing strategic alternatives for RELISTOR, including licensing, collaboration, strategic alliances and U.S. commercialization or co-promotion, following termination of its 2005 collaboration with Wyeth Pharmaceuticals*, which is continuing manufacturing, sales, marketing, clinical, and certain development and regulatory activities for RELISTOR during the transition. Ono Pharmaceutical Co., Ltd. has an exclusive license from Progenics for development and commercialization of subcutaneous RELISTOR in Japan. In oncology, the Company is conducting a phase 1 clinical trial of PSMA ADC, a human monoclonal antibody-drug conjugate for the treatment of prostate cancer. PSMA is a protein found on the surface of prostate cancer cells as well as in blood vessels supplying other solid tumors. In virology, Progenics is also developing the viral-entry inhibitor PRO 140, a humanized monoclonal antibody which binds to co-receptor CCR5 to inhibit human immunodeficiency virus (HIV) infection. PRO 140 is currently in phase 2 clinical testing. In early development, Progenics is evaluating novel antibodies to toxins produced by the bacteria C. difficile, as well as single-agent multiplex PI3-Kinase inhibitors as a potential strategy to combat some of the most aggressive forms of cancer, and is also seeking to identify novel entry-inhibitors of HCV infection.

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* Wyeth is now part of Pfizer Inc.

Editors Note:

For more information, please visit www.progenics.com.