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Panacos Presents Data on Lack of Clinical Resistance Development to Bevirimat (PA-457) at International HIV Drug Resistance Conference

Posted on: Wednesday, 14 June 2006, 09:01 CDT

Panacos Pharmaceuticals, Inc. (Nasdaq:PANC), a biotechnology company dedicated to developing the next generation of antiviral therapeutic products, today presented data demonstrating lack of rapid emergence of resistance to bevirimat in single and multiple dose monotherapy studies in HIV infected patients. The study, presented at the XV International HIV Drug Resistance Workshop in Sitges, Spain, was the result of a collaboration between Panacos and Dr. Eric Freed's group in the HIV Drug Resistance Program at the National Cancer Institute, Frederick, MD, USA.

In the new report, HIV was isolated from patients prior to, and following, monotherapy with bevirimat in single dose Phase 1/2 and multiple dose Phase 2a clinical studies. The amino acid sequence of the bevirimat target, the capsid-SP1 region of the HIV-1 Gag protein, from these viruses was determined by an approach called population sequencing which determines whether a significant proportion of virus within a patient exhibits resistance. No resistance mutations previously identified in laboratory cell culture assays were seen in patient isolates from these studies, nor was there any evidence of "viral rebound," or resurgence in viral load, during the period of bevirimat treatment. These results suggest that resistance to bevirimat does not emerge rapidly in patients, in contrast to some approved drugs where clinical resistance may be seen in the first 14 days of monotherapy. The results are noteworthy because bevirimat has a relatively long half-life of around 2.5 to 3 days. As a result, patients in the Phase 2a study were exposed to sub-optimal concentrations of bevirimat as monotherapy for up to three weeks following completion of the ten day treatment period, potentially an ideal situation for resistance development. Sequencing of the protease and reverse transcriptase genes did not reveal any new resistance mutations appearing during the study, nor did any pre-existing mutations affect the bevirimat treatment response.

Dr. Graham P. Allaway, Panacos' Chief Operating Officer commented, "We know the capsid-SP1 region is highly conserved among patient HIV isolates. While not definitive, these new data support the hypothesis of a genetic barrier to clinically significant bevirimat resistance in patients. We expect that resistance will be further suppressed when patients are treated with bevirimat in combination with other HIV drugs, as is expected to occur in future clinical trials and in clinical practice."

About Panacos

Panacos is developing the next generation of anti-infective products through discovery and development of small molecule oral drugs for the treatment of HIV and other major human viral diseases. HIV infects approximately 1.7 million people in North America and Western Europe and approximately 40 million people worldwide. Approximately 650,000 patients are treated annually for HIV in the United States and Western Europe. Resistance to currently available drugs is one of the most pressing problems in HIV therapy and the leading cause of treatment failure. Panacos' proprietary discovery technologies are designed to combat resistance by focusing on novel targets in the virus life cycle, including virus maturation and virus fusion.

Panacos' lead candidate, bevirimat (PA-457), is the first in a new class of oral HIV therapeutics under development called maturation inhibitors, discovered by Panacos scientists and their academic collaborators. Based on its novel mechanism of action, bevirimat is designed to have potent activity against a broad range of HIV, including strains that are resistant to existing classes of drugs. The Company has completed seven clinical studies of bevirimat in over 300 subjects, showing significant reductions in viral load in HIV-infected subjects and a promising safety profile.

Except for the historical information contained herein, statements made herein, including those relating to bevirimat's clinical development, the potential results of treatment with bevirimat and future clinical trials and clinical practice are forward-looking statements made pursuant to the safe harbor provisions of the Private Securities Litigation Reform Act of 1995. These statements involve risks as set forth in the Company's filings with the Securities and Exchange Commission, including, but not limited to, the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2005. These risks and uncertainties could cause actual results to differ materially from any forward-looking statements made herein. The Company undertakes no obligation to publicly update forward-looking statements, whether because of new information, future events or otherwise, except as required by applicable law.

Source: Business Wire

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