August 12, 2006

Experimental HIV Drug Helps Control Virus

TORONTO -- An experimental HIV drug in a new class called integrase inhibitors helps control the virus well combined with other drugs commonly used in AIDS cocktails, its maker Merck and Co. reported on Saturday.

The findings, to be presented at an international AIDS meeting, offer a potential new weapon in the growing armory of drugs that fight HIV. The drug mixtures can keep HIV patients healthy for years, although they are not a cure.

Merck said the drug, known by its experimental name MK-0518, worked as well as older drugs to suppress the AIDS virus when combined with Gilead Sciences' tenofovir, known commercially as Viread and GlaxoSmithkline's lamivudine, sold under the brand name Epivir.

They compared the new drug with a similar cocktail using Bristol Myer Squibb's efavirenz, sold under the brand names Sustiva and Stocrin. For the study, 198 HIV-infected patients took one or the other mixture for 24 weeks.

Both combinations lower viral load -- the amount of the virus be found in blood. Suppressing the virus limits the damage it can do to a patient's immune system.

"This early study showed a rapid and significant reduction in viral load up to 24 weeks with MK-0518," Dr. Martin Markowitz of the Aaron Diamond AIDS Research Center in New York, who led the study, said in a statement.

"This study should lend further insight into the potential of HIV integrase inhibitors as a new and exciting class of antiretroviral agents."

There are several classes of HIV drugs, also known as antiretroviral drugs. Each class attacks the virus at a different point in its cycle of replication.

Combining the drugs in a cocktail suppresses the virus even more, but eventually the virus in a patient's body escapes the effects of drugs so new approaches and combinations are needed to control it.

When the human immunodeficiency virus infects a cell, usually an immune system cell called a T-cell, it attaches to the cell, pierces it and inserts its own genetic material.

The viral DNA re-programs the cell, in essence hijacking it, and forces it to produce copy after copy of the virus, which it pumps into the blood to infect other cells.

The integrase inhibitors stop the insertion of the HIV viral DNA into human DNA, shutting down the virus factory.

Other HIV drugs target other enzymes involved in this hijacking process.

Several companies are working on integrase inhibitors but none is approved yet.