Merck's Antiretroviral Raltegravir Found to Reduce Viral Loads Among HIV-Positive People With Drug Resistance, Study Says
April 17, 2007
Merck's integrase inhibitor raltegravir effectively decreases HIV viral loads after 24 weeks of use among HIV-positive people who have not responded to other treatments, according to a study published in the April 14 online edition of the journal Lancet, AFP/Yahoo! News reports (AFP/Yahoo! News, 4/13). Raltegravir, formerly known as MK-0158, works by blocking an HIV enzyme called integrase. Integrase is one of the three enzymes necessary for HIV to replicate in the body, and integrase inhibitors would stop HIV from inserting its genes into uninfected DNA. The other two enzymes necessary for viral replication -- reverse transcriptase and protease -- already are targeted by a variety of antiretrovirals (Kaiser Daily HIV/AIDS Report, 2/28). For the study, Beatriz Grinsztejn of Merck Research Laboratories in Westpoint, Pa., and colleagues divided 178 HIV-positive people into four groups. Participants in three groups received different doses of raltegravir, ranging from 200 milligrams to 600 milligrams, and the fourth group received a placebo. All four groups also took a basic "background treatment," according to AFP/Yahoo! News. The study found that after 24 weeks, HIV viral loads dropped below a measurable threshold of 50 copies per milliliter in 65% of the patients taking the drug, nearly five times as many as the placebo group. The study also found that immune system responses substantially improved. Pedro Cahn and Omar Sued of the Department of Clinical Research at the Fundación Huesped in Buenos Aires, Argentina, in an accompanying Lancet commentary wrote that raltegravir "showed unprecedented levels of virological efficiency," adding that the treatment "achieved virological suppression even in patients with limited options." According to Cahn and Sued, "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" (AFP/Yahoo! News, 4/13). Merck has announced that it will apply for FDA approval in the second quarter of 2007 (Kaiser Daily HIV/AIDS Report, 2/28).
The study is available online.
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