Maraviroc, the first in a new class of oral HIV drugs known as CCR5 inhibitors, is one step closer to becoming available with its pending approval by the European Medicines Agency. CCR5 inhibitors bind to receptors on the surface of cells, stopping HIV from latching on and inserting itself into other uninfected cells and preventing infected cells from replicating. Interestingly, evidence for the potential use of this therapy came from a group of people with hemophilia in Italy who did not contract HIV despite using contaminated blood products. It was eventually discovered that each of them carried a rare genetic modification in a receptor used by HIV to bind to human immune system cells.
Maraviroc, developed by Pfizer Inc., is pending final marketing approval in Europe and accelerated review by regulators in Canada and the U.S. Pfizer anticipates U.S. approval by the end of the year.
Clinical trials have shown that when used in combination with an optimized treatment regimen, maraviroc is twice as effective in reducing HIV blood levels as the treatment regimen alone. Although the drug does not eliminate the virus completely, studies have demonstrated that it can reduce HIV in the blood to undetectable levels in patients with long-term infection. In two trials involving more than 1,000 patients, 45% of those who supplemented their existing drug regimen with maraviroc showed nearly imperceptible HIV blood levels. In contrast, of the patients receiving the existing therapy alone, only 23% achieved undetectable HIV levels. Maraviroc also boosted CD4 immune system cell levels—white blood cells that play an important role in immunity and that are targeted by HIV—in patients, another key determinant of effectiveness.
"The importance of new classes of treatment for HIV cannot be overstated," said Mark Nelson, MA, MBBS, MRCP, with the Chelsea and Westminster Hospital in London, which took part in the maraviroc trials. "Maraviroc is an exciting product as it allows us to build oral treatment regimens for the first time that target HIV both inside and outside the cells that the virus attacks."
Source: The Times (London), July 23, 2007