A new class of anti-HIV drug which inhibits an as-yet untargeted enzyme in the virus has proven effective in a drug trial, according to an Article in this weeks edition of The Lancet.
There is an urgent need for new antiretroviral drugs due to existing rates of failure in existing combination antiretroviral therapies. The current study looked at the new "integrase-inhibitor" raltegravir when used in conjunction with optimised background combination therapies, in patients with advanced HIV infection whose existing treatments were failing.
There are three types of enzyme essential to the successful replication of HIV reverse-transcriptase, protease and integrase. Integrase is responsible for insertion of HIV DNA into the host cells DNA. Until now all antiretroviral drugs for HIV which target enzymes have been reverse-transcriptase or protease inhibitors.
Dr Bach-Yen Nguyen, Merck Research Laboratories, Westpoint, Pennsylvania, USA, and colleagues divided their patients into four groups. One group received the background treatment plus placebo only, and the other three received the background treatment plus 200, 400 or 600mg of raltegravir twice daily. All 178 patients across the four groups had been receiving antiretroviral therapy for an average of just under 10 years.
The researchers measured the amount of HIV genetic material (HIV RNA) in the blood of patients after 24 weeks, and found that patients taking raltegravir experienced an average of 98% drop in their HIV RNA count, compared to just 45% drop in the placebo group.
The number of CD4 cells which give an indication of the immune response were also significantly boosted in patients taking raltegravir. Patients receiving the 400mg and 600mg doses increased their CD4 count by 113 and 94 cells per ml of blood respectively.
Raltegravir also proved safe, well tolerated and potent in most of the patients.