New AIDS Drug 'Incredibly Encouraging'
Isentress Works When All Other AIDS Drugs Fail, Study Shows
March 1, 2007 -- "Incredibly exciting." "Road to hope."
"Very exciting." "A very important milestone in HIV treatment
That's what major AIDS researchers are saying about Isentress, the first of
a new class of HIV drugs. Early results from two major clinical trials of
Isentress were reported this week at the largest annual U.S. HIV
Patients in the studies had run out of treatment options. After a decade of
treatment, the HIV in their bodies had become resistant to at least one drug in
each of the three classes of AIDS therapies. Their immune systems had begun to
fail and they had high blood levels of HIV.
But when these patients took Isentress in combination with other powerful
AIDS drugs, nearly 80% of patients saw their HIV levels plummet to
near-undetectable levels after 16 weeks of treatment. Without Isentress,
state-of-the-art treatment helped only 43% of patients to this degree.
Joseph J. Eron Jr., MD, of the University of North Carolina-Chapel Hill,
reported the combined findings from the studies at the 14th annual Conference
on Retroviruses and Opportunistic infections.
"This is a very important milestone in HIV treatment history," Eron
tells WebMD. "These are results we would have been happy with in
treatment-naive patients. And these are our most drug-experienced,
drug-resistant patients -- the ones for whom it is most difficult to come up
with treatment options.
"It really moves us into an era where even our most
treatment-experienced patients have the opportunity to get their virus below
detectable limits," Eron adds.
New AIDS Drug, New HIV Target
HIV makes three proteins, called enzymes, which it needs to infect human
cells. The AIDS virus uses its reverse transcriptase enzyme to translate its
RNA genetic code into DNA. Later, after it has made human cells produce new
viral proteins, it uses its protease enzyme to snip the proteins into the right
Nearly all existing HIV drugs block either reverse transcriptase or
protease. But Isentress blocks an enzyme called integrase. HIV needs integrase
to integrate its newly translated DNA into the DNA of human cells.
Researchers have worked for years to develop an integrase inhibitor. Until
recently, that goal was elusive. Now that work is paying off. Isentress, from
Merck, is the first of its kind. But others are on the way.
The Isentress results are based on only 16 weeks of treatment, although
early 24-week results look as good. Eron warns that the durability of the
treatment remains unproved.
Yet normally cautious AIDS researchers say it's been a very long time since
they've seen such promising findings.
One is Amneris Luque, MD, medical director of the AIDS Center at the
University of Rochester, New York.
"This is the road to hope for people who have failed all other AIDS
medications," Luque tells WebMD. "It is very impressive to see these
kinds of numbers in patients who have developed resistance to other