Liquid and tablet bevirimat doses of between 250 – 400mg yield good reductions in HIV viral load in treatment-experienced patients, according to the latest results of studies into the investigational product that have been released by its manufacturer, Panacos Pharmaceuticals, in a press release. These results also showed which patients were most likely to benefit from bevirimat therapy.
Bevirimat is an experimental drug that belongs to a new class of antiretrovirals called maturation inhibitors. It is currently in Phase IIB clinical trials that are designed to find the drug’s most effective and safe drug. These studies involve patients who have taken a lot of anti-HIV treatment before and are having difficulty finding effective antiretroviral therapy.
Five doses of bevirimat – 250, 300, 350 and 400mg liquid doses and a 400mg tablet - were tested in five separate cohorts of patients. In these studies, which lasted 14 days, 46 patients were given bevirimat and 13 patients received a placebo. All the patients were heavily treatment-experienced and received no other antiretroviral drugs apart from their study medication.
The mean fall in viral load was 0.60 log10 in the bevirimat-treated patients. However, the investigators found that the fewer polymorphisms in the HIV gag protein a patient had, the better their response to bevirimat. Gag polymorphisms are common in patients who have received past therapy with multiple anti-HIV treatment regimens. Patients who did not have any polymorphisms had a mean fall in their viral load of 1.26 log10.
Panacos has conducted an analysis of their database of over 100 HIV-positive patients, most of whom have advanced HIV disease and extensive experience of antiretroviral therapy. Analysis of this database showed that approximately 50% of these patients could benefit from bevirimat therapy. And a preliminary study of a larger patient database suggests that the drug might work in a much larger proportion of patients.
Investigators have also looked at the blood levels of bevirimat needed to achieve a good treatment response. They found that liquid and tablet doses of 250mg and above all provided adequate drug levels in patients who lacked the key gag polymorphisms.
Bevirimat appears to be safe as there was no difference in reported side-effects between the patients who received the drug and those who were given the placebo.