2. AIDS Drug Works on Monkeys
Foster City firm records a first
November 17, 1995
By BARRY KAYE
Times Staff Writer
FOSTER CITY – Researchers at a Foster City biotechnology company reported today that, for
the first time, a drug that inhibits the ability of the AIDS virus to replicate itself achieved a 100
percent success rate in monkeys.
The early, preclinical studies indicate that a revolutionary compound developed by Gilead
Sciences provided protection against the development of simian immunodeficiency virus (SIV)
in primates up to 24 hours after they were given large doses of the disease.
Gilead conducted the study in conjunction with scientists at the National Institutes of Health
and researchers at the University of Washington Primate Center in Seattle. The results appear
in this month’s issue of the prestigious Science magazine.
“No other drug has ever shown this kind of activity. It is really unbelievable,” said Roberta
Black, a microbiologist with the National Institute of Allergy and Infectious Diseases, a division
of NIH.
Finding a cure for AIDS has been especially difficult because the virus that causes it is
constantly changing and mutating. Scientists also know very little about how the disease itself
actually works.
[Photo Caption: MICHAEL RIORDAN: Gilead CEO says, “It turns off the enzyme the virus uses
to replicate itself.”]
Gilead’s work involves something known in biotechnology circles as a nucleotide analog, a
molecule that binds to a substance called reverse transcriptase.
“It turns off the enzyme that the virus uses to replicate itself,” said Michael Riordan, chief
executive officer at Gilead.
Riordan cautioned that the drug, called PMPA, has not yet been tested in humans, although
he said the disease in monkeys is very similar to the HIV virus.
There is no known cure for AIDS, which attacks the human immune system and is almost
always fatal.

3. Researchers at the National Institute of Allergy and Infectious Diseases, which helped fund
the study, said early tests show that the Gilead drug blocked all traces of the disease in 25
macaque monkeys more than one year after the experiment began.
“It sounds almost too good to be true,” said Dr. Marta Marthas, a virologist at the University
of California at Davis’ Regional Primate Research Center. But she added, “You can’t argue with
that result.”
Dr. Ashley Haase, an expert on lentiviruses, the virus family that includes HIV and SIV
(simian), said he was “surprised and pleased” by the finding.
He added that the study was carefully done and that it was “if anything, more difficult” to
protect against SIV than it was to protect against HIV infections.
NIH’s Black, who was on work furlough because of the federal budget impasse, said a
tremendous amount of additional research still needs to be completed.
Further tests are needed, for example, to determine how well monkeys tolerate high doses
of the drug.
“Monkeys are not human beings,” she said. “Although it is an excellent model for evaluating
drugs, it is still a model.”
But among the encouraging benefits of the Gilead compound is that, in achieving a 100
percent success rate, there were no additional complications.
“Such complete protection with no toxicity is unprecedented in the monkey model of AIDS,”
said Anthony S. Fauci, director of infectious diseases at NIH.
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