FDA Panel Backs New HIV Drug

By Todd Zwillich

Reviewed by Louise Chang, MD

Sept. 5, 2007 -- A new HIV drug gained a federal advisory panel's backing for rapid government approval Wednesday.

The drug, known by the brand name Isentress, will join more than 20 other HIV/AIDS medications on the U.S. market if it is approved by the FDA. Experts say Isentress could pose a significant advance for HIV-positive patients because it works against the virus in a different way than other drugs.

Isentress developer Merck & Co. says it would market the drug to patients who continue to have increasing HIV counts despite taking several other drugs. HIV patients frequently must switch medications when the virus becomes drug-resistant or side effects make a product hard to take. 

Antiretroviral drugs help get the "viral load" -- the number of viruses circulating in the body -- as low as possible.

FDA advisors unanimously backed the drug after Merck showed it can reduce viral load in patients whose infection is advancing despite taking combinations of other drugs.

Nearly 80% of patients who added Isentress to their drug cocktails had very low levels of viral loads after six months of treatment, Merck says. That's nearly double the number who got similar results when a placebo was added to their existing drug regimens.

"There is no doubt that this is a great drug, absolutely," says Peter L. Havens, MD, a professor of pediatrics and epidemiology at the Medical College of Wisconsin and a member of the advisory panel.

Isentress -- also known as raltegravir -- works by inhibiting one of three enzymes that HIV viruses use to infect human cells. Currently available drugs work by preventing HIV replication in other ways or by blocking the virus from attaching to white blood cells.

More than 37,000 Americans were diagnosed with HIV in 2005, according to the CDC. Merck estimates that between 20,000 and 40,000 U.S. HIV patients would qualify to take Isentress if it's approved. 

Women and minorities make up a significant number of new HIV cases in the U.S. But experts criticized Merck and other companies for primarily enrolling white males in its drug studies. Panel member Fred Gordin, MD, said experts and activists have been pleading with companies for years to perform studies reflecting the face of the HIV/AIDS epidemic. 

"I don't know what more anyone on this panel can say," says Gordin, a professor of medicine at George Washington University.

"It is unfortunate that we have to bring this question up in 2007," says Debra Brinkrant, MD, director of the FDA's division of antiviral products.

Robin Isaacs, MD, Merck's executive director of clinical research, tells WebMD that his company "tried very hard" to enroll more women and minorities in its trials. Historically it's been difficult to get a good distribution of either group into studies."

"It's clearly an issue we would like to do better in," he says.

AIDS activists who testified at the hearing urged Merck to set a price for Isentress that will be affordable not only to U.S. patients, but also to governments of poor countries where the epidemic is far worse than it is here.

"The company should decide upon as low a cost as possible to assure people have access," says Matt Sharp, a member of the AIDS Treatment Activist Coalition.

Company officials say a price for the drug has not yet been set.

The agency is expected to issue a decision on Isentress by mid-October under a fast-track approval process.

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