FDA Panel Backs New HIV Drug
Drug Called Isentress Uses New Approach to Fighting AIDS Virus
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.
Reducing 'Viral Load'
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.
Novel Drug Class
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
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
"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
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.