Coverage of 2007 IAS
(International AIDS Society)

July 2007, Sydney, Australia

New Monoclonal Antibody Drug, PRO140, Shows Promise

July 26, 2007

Results were presented at the 4th IAS Conference on Retroviruses and Opportunistic Infections in Sydney, Australia from a study of PRO140, a monoclonal antibody entry inhibitor that blocks the CCR5 receptor,. PRO140 is different from other drugs that target CCR5, like Selzentry (maraviroc) and vicriviroc (Schering-D), in two important ways. First, unlike these other drugs, PRO140 must be given as an intravenous infusion: through a needle directly in to the blood. Second, it targets a different part of the CCR5 protein, meaning it should still work against HIV that has grown resistant to the oral R5 drugs.

The study followed 49 people who were given a single dose of PRO150 as a monotherapy. All volunteers had only ‘R5 only’ HIV (HIV that uses the R5 receptor) and had been off all other anti-HIV drugs for at least three months. They were given one of three different doses (0.5, 2 or 5 mg/kg) of PRO140 or a placebo by infusion. Changes in HIV levels were checked periodically for 60 days.

People given the two higher doses of PRO140 in this study had significant drops in HIV levels. At the highest dose, the average drop was 1.8 logs. Reductions in HIV levels were greatest 10 days after infusion, and rose back to pre-infusion levels after around 30 days. There were no serious side effects reported in the study, and only one person taking PRO140 experienced a shift in HIV type from R5-only to dual/mixed HIV.

The magnitude of reduction in HIV levels seen from a single dose was impressive. While the optimal dosing schedule for this drug hasn’t been determined, the fact that the lower HIV levels were maintained for so long after infusion suggests that it might be given every 10 days to 2 weeks.

Monoclonal antibodies are large proteins that are expensive to manufacture. With so many powerful, easy-to-use oral HIV drugs available many people question the need for such therapies. However, the results from this single-dose study were impressive enough for the drug to move forward. More studies are planned to start later this year.