Business Wire - September 27, 2002

Single doses of PRO 542 reduced concentrations of the human immunodeficiency (HIV) in the blood by 60% to 80% in a target population of highly treatment-experienced patients with PRO 542-sensitive virus. The viral-load reductions were sustained throughout the six-week follow-up period, and no serious side effects were observed. The Company also announced that it has begun multi-dose Phase II clinical studies of PRO 542 as salvage therapy of HIV-infected individuals who are no longer responding to currently available antiretroviral medications. In addition, the Company presented an update on its PRO 140 anti-CCR5 antibody, which is preparing to enter clinical trials. The presentations were made at the 42nd Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) in San Diego.

"The prolonged duration of PRO 542's antiviral effect was a particularly striking finding of this study, since we had expected that the virus levels would return to baseline during follow-up," said Jeffrey M. Jacobson, M.D., Assistant Chief and Program Director, Division of Infectious Diseases at Beth Israel Medical Center in New York City and Principal Investigator of the study. "The trial results provide strong support for expanded Phase II studies of multi-dose PRO 542 therapy in this patient population."

Sustained reduction in blood levels of virus, or "viral load," is a primary goal of HIV therapy. Following treatment with a single 25 mg/kg intravenous dose of PRO 542, patients experienced viral-load reductions of 0.4 to 0.6 log(10) copies/mL on average. The antiviral effects were statistically significant for as long as four weeks post-treatment (p = 0.038, two-sided test) and were observed in 80% of prospectively treated salvage therapy patients. Notably, the patients' blood levels of virus had not returned to baseline at the conclusion of the six-week follow-up period. The study further demonstrated that PRO 542 continued to be well tolerated, and no serious side effects were reported.

Assay results correlate with PRO 542 responders

The completed Phase II trial utilized HIV resistance-testing technology from ViroLogic, Inc. (Nasdaq: VLGC). ViroLogic's PhenoSense HIV Entry assay was used to assess the susceptibility of the patients' viruses to PRO 542. The assay results correlated with the magnitude of viral-load reductions in patients treated with PRO 542. This screening technology is also being utilized within the recently initiated multi-dose trial of PRO 542.

The Company's new findings confirm previously reported results indicating that PRO 542 was particularly active in treatment-experienced patients with high viral loads (greater than 100,000 copies/mL) and/or low CD4 counts (less than 200 cells/mm(3)). The patients in the completed study harbored viruses that were resistant to two of the three approved classes of antiretroviral therapies.

"We are pleased that PRO 542 reduced viral loads in individuals who are most in need of new treatment options," said Robert J. Israel, M.D., Sr. Vice President of Medical Affairs at Progenics. "These results confirm our earlier findings on the activity of PRO 542 in patients who are no longer responding to conventional therapy. The completed trial supports further development of PRO 542 as an infrequently administered intravenous agent."

PRO 542 belongs to a new class of drugs, viral-entry inhibitors, which are intended to prevent HIV from entering and infecting cells. Unlike currently approved therapies that block viral replication in cells already infected with HIV, PRO 542 is an antibody-like molecule that is designed to target and neutralize the virus in the bloodstream. Because of its novel mechanism of action, PRO 542 has the potential to be broadly active against both wild-type viruses and viruses that have acquired resistance to existing classes of antiretroviral therapies. To date, PRO 542 has been used to treat more than 50 HIV-infected individuals.

Company provides update on PRO 140, second HIV viral-entry inhibitor

In a second presentation at the ICAAC meeting, Progenics reported that in laboratory studies a humanized version of its PRO 140 HIV-entry inhibitor reproduced the compelling therapeutic profile of its "parent" mouse antibody. PRO 140 is a monoclonal antibody that is designed to block HIV entry by binding to a portion of the receptor that the virus uses to infect cells. Humanized PRO 140 inhibited entry of multiple strains of HIV into immune system cells, in vitro. In addition, it demonstrated the unique ability to block HIV entry via CCR5, while leaving the normal function of this receptor unaffected. Preclinical testing and manufacturing scale-up are expected to be completed in the coming months, with Phase I clinical trials scheduled to begin in 2003.

Progenics Pharmaceuticals, Inc. of Tarrytown, NY, is a diversified 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. The Company applies its expertise in immunology and molecular biology to develop biopharmaceuticals to fight viral diseases, such as human immunodeficiency virus (HIV) infection, and cancers, including malignant melanoma and prostate cancer. In supportive care, therapies are being developed to provide patients with an improved quality of life. The Company is conducting Phase II clinical studies with methylnaltrexone, a compound designed to block the debilitating side effects of opioid analgesics without interfering with pain palliation. The Company has initiated Phase II clinical trials with its lead HIV product, PRO 542, a viral-entry inhibitor and is in preclinical development with PRO 140 and other follow-on product candidates in HIV infection. Progenics' most clinically advanced product, GMK, is a cancer vaccine in Phase III clinical trials for the treatment of malignant melanoma. The Company is developing cancer immunotherapies based on PSMA (prostate specific membrane antigen) technology. Dehydroascorbic acid (DHA), a novel small-molecule antioxidant, is the subject of preclinical studies to treat stroke.

This press release contains forward-looking statements. Any statements contained herein that are not statements of historical fact may be forward-looking statements. When the Company uses the words 'anticipates,' 'plans,' 'expects' and similar expressions they are identifying forward-looking statements. Such forward-looking statements involve risks and uncertainties which may cause the Company's actual results, performance or achievements to be materially different from those expressed or implied by forward-looking statements. Such factors include, among others, the uncertainties associated with product development, the risk that clinical trials will not commence when or proceed as planned, the risks and uncertainties associated with dependence upon the actions of the Company's corporate, academic and other collaborators and of government regulatory agencies, the risk that products that appear promising in early clinical trials do not demonstrate efficacy in larger-scale clinical trials, the uncertainty of future profitability and other factors set forth more fully in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2001 and other periodic filings with the Securities and Exchange Commission to which investors are referred for further information. In particular, the Company cannot assure you that any of the their programs will result in a commercial product. The Company does not have a policy of updating or revising forward-looking statements, and thus it should not be assumed that the Company's silence over time means that actual events are bearing out as expressed or implied in such forward-looking statements.

Editor's Note:

Additional information on Progenics is available at http://www.progenics.com

CONTACT: Progenics Pharmaceuticals, Inc. Richard W. Krawiec, Ph.D., 914/789-2800 VP, Investor Relations and Corporate Communications rkrawiec@progenics.com

SOURCE: Progenics Pharmaceuticals, Inc.

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