By Andrea Orr
LOS ANGELES, April 11 (Reuters) - An experimental AIDS drug being developed by Gilead Sciences Inc has
been shown to drive down viral levels by more than 90 percent in the first eight days of treatment in clinical trials,
the company said on Friday.
Although Gilead has yet to test the drug for sustained periods of time in humans, it said that based on the rapid pace
at which it reduced the virus in the short-term trial, as well as further success in longer trials in animals, it was
hopeful it could eventually achieve more than 99 percent viral reduction.
The drug, known as anti-retroviral PMPA, belongs to a class of compounds known as nucleotide analogues, which
block the human immunodeficiency virus (HIV) that causes AIDS from replicating. While it is similar to some of the
most widely used AIDS drugs like AZT, PMPA targets a wider area of the virus, reducing the risk that it can
develop a resistance, Gilead said.
"Based on mathematical models of how the virus replicates, you would not be able to do much better than (90
percent) reduction in viral load in a single week, regardless of how many therapies or the potencies of the drugs,"
said Dr. Howard Jaffe, senior vice president of drug development at Foster City, Calif.-based Gilead.
"But based on the animal data and the slope of the decline in the eight-day test on humans, we have every reason to
believe it would continue to drive down viral levels if used over a longer term."
While many doctors have successfully lowered their patients' viral load by more than 99 percent using the
celebrated three-drug cocktail, Gilead's findings could potentially achieve the same results with a lighter drug
regimen.
Jaffe said the Gilead drug would need to be taken only once a day, and preliminary results showed it was well
tolerated with no significant side effects except nausea.
Jaffe said Gilead also tested a vaginal gel form of the drug in animals, which was found to block the spread of the
virus during sexual activity. It plans to begin similar studies in humans later this year in collaboration with the
National Institutes of Health in Bethesda, Maryland.
In the trial on humans, Gilead gave patients eight intravenously administered doses of PMPA for eight consecutive
days. The trial was halted at that point because of the dramatic results. Gilead said it hoped to eventually develop
the drug as a pill, and would begin trials within the next few weeks on a tablet form of PMPA.
"A once-a-day intravenous infusion is not something that patients who are going to live for several years are going
to want," said Jaffe. "We want to devote our resources to an oral form of the drug."
If those studies are successful, Gilead would follow with a Phase III clinical trial in 1998, but even in a best case
scenario the drug would not reach the market any sooner than 1999. |
