PMPA: New Information

PMPA, an antiviral being developed by Gilead Sciences but not yet tested in humans, came to widespread attention last November, when a study published in SCIENCE (November 17, 1995) showed that it could block SIV (simian immunodeficiency virus) infection in macaque monkeys even when given 24 hours after exposure; PMPA protected 100% of the monkeys tested, while AZT protected none (there were 10 monkeys in each group). Now another study, presented at the Ninth International Conference on Antiviral Research in Fukushima, Japan, found that PMPA reduced SIV in chronically infected macaques by more than two logs (99%), or past the limits of detection; the virus reappeared when the drug was stopped.(1) Also, a 10% PMPA jell protected all four monkeys from vaginal transmission, while both of two monkeys treated with the control jell without PMPA were infected,(2) suggesting the possibility of a means of preventing sexual transmission which could be controlled by women -- which would have great public-health importance. (SIV is similar to HIV; the virus is so close to HIV-2 that many believe that humans acquired HIV-2 by SIV infection from monkeys. No animal ancestor to HIV-1 is known.)

For both studies, the researchers are from Gilead, the University of Washington Regional Primate Research Center, and the National Institutes of Health. Chiron Corporation also participated in the treatment study.

Gilead Sciences plans to start human testing of PMPA in 1996.

References

1. Bischofberger N, Tsai CC, Follis KE, and others. Antiviral efficacy of PMPA in macaques chronically infected with SIV. Ninth International Conference on Antiviral Research, Fukushima, May 19-24, 1996.

2. Miller C, Rosenberg Z, and Bischofberger N. Use of topical PMPA to prevent vaginal transmission of SIV. Ninth International Conference on Antiviral Research, Fukushima, May 19-24, 1996.