Isentress Fights Drug-Resistant HIV

July 23, 2008 -- A new HIV drug called Isentress has proved successful in lowering levels of the virus even when other drugs have failed.

New research in TheNew England Journal of Medicine details the results of two studies of Isentress. It's the first of a new class of HIV drugs that targets an enzyme called integrase to make it harder for HIV to multiply and infect new cells.

Isentress is designed to work in combination with other HIV drugs to lower HIV levels circulating in the blood. It's specifically used for HIV that is already resistant to other commonly used drugs. Isentress does not cure HIV or stop the virus from spreading among people.

Based on preliminary results of these clinical trials, the FDA approved Isentress for use in HIV treatment via its fast-track approval process in October 2007.

New Option for HIV Treatment

People with HIV (the virus that causes AIDS) must add or switch medications when the virus becomes resistant to drugs they are taking.

In the studies, researchers looked at people whose HIV had become resistant to multiple drugs and whose HIV levels remained high. In addition to taking an HIV drug regimen optimized for them, each of the 699 participants also received Isentress or placebo.

After 16 weeks of treatment, 78% of the Isentress group had viral levels below 400 copies per milliliter compared with 42% of those who received placebo.

Nearly two-thirds of those taking Isentress reduced their viral load to a level below 50 copies per milliliter compared with one-third of those taking a placebo. After four years of treatment with Isentress, 62% still had well-controlled HIV with viral loads less than 50.

Researcher Roy T. Steigbigel, MD, of the State University of New York at Stony Brook and colleagues say the results show that in people with HIV with limited treatment options, adding Isentress to current HIV drug therapy provided better results than standard therapy alone.

The study was supported by Merck, which manufactures Isentress.