The study met its primary endpoint by demonstrating a statistically significant reduction in the level of HIV in the blood, known as viral load, compared to placebo. The median reduction in viral load in the trial was greater than 1 log10, or a 90% decrease, at the highest dose. PA-457 is the first in a new class of HIV drugs called Maturation Inhibitors, with broad activity against HIV, including strains resistant to currently approved drugs, the most common cause of HIV treatment failure.
In this randomized double-blind phase IIa study, performed at leading academic centers in the US, PA-457 at one of four doses (25, 50, 100 or 200mg; 6 patients per group) or placebo (8 patients), was administered orally once daily for 10 days to HIV-infected subjects not on other antiretroviral therapy. The primary endpoint was viral load reduction on Day 11. Other endpoints included safety, tolerability and pharmacokinetics of the drug.
Genetic analysis of HIV in patients pre and post treatment, available now for 21 out of 33 patients in the study, showed no evidence of the development of resistance to PA-457. All doses were observed to be generally safe and well tolerated.
“We are extremely pleased with the results of this important phase IIa study,” commented Dr Samuel Ackerman, chairman and CEO of Panacos. “We believe that PA-457 is a potential breakthrough drug which could play a role throughout the HIV treatment spectrum, including both naive and treatment- experienced patients, based on once-a-day oral dosing, potent activity observed against drug resistant virus and a promising safety profile. We now plan to move forward aggressively to initiate a phase IIb study of the drug in the first half of 2006.”