New HIV drug shows 'unprecedented' results

A new category of drug has shown promising results for HIV/ AIDS patients who failed to respond to other treatments, a study to be published Saturday shows.

Especially when combined with other medications, raltegravir -- the first in a new class of anti-retroviral drugs called integrase inhibitors -- dramatically reduced the presence of the HIV virus and boosted immunity in clinical-trial patients, according to the study in the British journal The Lancet.

Integrase inhibitors act by targeting and disrupting an enzyme that facilitates the insertion of the HIV virus into the host's cellular genome.

In clinical tests on 178 patients with advanced HIV infections that had proved resistant to standard treatments, raltegravir "showed unprecedented levels of virological efficiency," virologists Pedro Cahn and Omar Sued wrote in a commentary in the same journal.

The treatment "achieved virological suppression even in patients with limited options," they wrote, predicting that the new drug would "have a major role in salvage therapy," the term used to describe last-ditch efforts to save those with highly-compromised immune systems.

"Clearly, we are in a new era of anti-retroviral therapy," they added.

There are three types of enzyme needed for HIV to replicate, namely reverse-transcriptase, protease and integrase. Up to now, no drug has successfully inhibited integrase enzymes.

A team of researchers at Merck Research Laboratories in Westpoint, Pennsylvania, led by Beatriz Grinsztejn, divided the 178 patients into four groups during clinical trials.

Each of three groups were given different doses of raltegravir, ranging from 200 to 600 milligrams, and the fourth group received a placebo. All four also took a basic "background treatment."

After 24 weeks, the amount of HIV genetic material in the blood dropped below a measurable threshold (50 copies per millilitre) in 65 percent of the patients taking raltegravir, nearly five times as many as the placebo group. Immune system responses were also dramatically improved.

"If no long-term unexpected side-effects or resistance issues emerge, raltegravir will have a major role in salvage therapy, particularly in combination with another new drug," Cahn and Sued concluded.