PANACOS ANNOUNCES REVISED MATURATION INHIBITOR STUDY PLANS

Panacos Pharmaceuticals announced it has agreed with the FDA on a revised trial design for the company's Phase IIb clinical study of bevirimat (PA-457), the first-in-class maturation inhibitor for the treatment of HIV infection. The first cohort in this study was completed in December 2006 and confirmed the antiviral activity of bevirimat shown in previous studies and extended it to HIV patients failing therapy due to antiretroviral resistance. However, the prototype tablet formulation used in that cohort resulted in bevirimat plasma concentrations that were lower than anticipated.

The next cohorts in the study will test the tolerability and efficacy of bevirimat in treatment-experienced patients failing current therapy, at increasing doses using the oral liquid formulation, which was used in the Phase IIa trial.

The Phase IIb dose-escalation trial with the liquid formulation will involve 14-day functional monotherapy, where patients are dosed with either placebo or bevirimat in combination with their failing antiretroviral therapy. This is similar to the first Phase IIb cohort except that patients will not continue on to extended dosing.

The primary endpoints of the trial will be safety and viral load reduction on day 15. To expedite dose escalation, the cohort size will be reduced to eight patients on bevirimat and two on placebo. Dosing of the next cohort will be initiated at 250 mg of the oral solution once daily, a higher dose than previously studied in multiple-dose trials of bevirimat solution. Panacos plans to escalate the dose in subsequent cohorts by 50 mg per cohort following review of the safety and antiviral response from each preceding cohort.