For the first time, a study shows that a drug used to treat HIV infection also can help prevent it when taken before and after risky sex by gay men.
The results offer hope of a more appealing way to help prevent the disease beyond taking daily pills and using condoms, although those methods are still considered best.
The study, done in France and Canada, is the first to test “on demand” use of Truvada, a pill combining two AIDS drugs, by people planning to have risky sex. The uninfected men who took it were 86 percent less likely to get HIV compared to men given dummy pills.
“That impressed me,” Dr. Scott Hammer said of the size of the benefit. He is an AIDS specialist at Columbia University in New York and heads the Retrovirus Conference going on in Seattle, where the results were discussed Tuesday.
Daily Truvada pills are used now to prevent HIV infection in people at high risk for it, and studies show the drug helps even when some doses are skipped. Health officials have been leery of billing it as a “chemical condom” out of fear that people will not use the best prevention methods, but many won’t use condoms all the time or take daily pills.
The study of Gilead Science’s Truvada was led by the French national HIV research agency.
Men were given fake or real Truvada and told to take two pills from two to 24 hours before sex, a third pill 24 hours later, and a fourth pill 48 hours after the first dose. The men also were given condoms and disease prevention counseling.
The study was stopped early, in November, after 400 men were enrolled and researchers saw that the drug was working; there were two new HIV infections among those on Truvada and 14 in those on dummy pills. The two infections in the Truvada group were in men who stopped using the pills after more than a year in the study.
The drug was safe, but nausea and diarrhea were more frequent among men who used it. Only one stopped using it because of side effects.
A second study presented at the conference by the U.K. Medical Research Council found that daily use of Truvada cut the risk of infection by 86 percent in a “real world” test of gay men aware they were taking Truvada for HIV prevention.
Researchers assigned 545 gay men to get Truvada right away or a year later. The study was stopped in October after HIV infections occurred in only three men given Truvada but in 19 of those assigned to get it after a year.
As in the French study, rates of other sexually spread diseases were similar in both groups, leading researchers to conclude that use of the prevention pills was not increasing risky behavior.
Since available data suggest that men in this study were taking PrEP an average of three to four days per week, CDC cautions that researchers do not yet know if this regimen will work among MSM who have sex less frequently and would therefore be taking PrEP less often.
It is not known whether the regimen will work if taken only a few hours or days before sex, without any buildup of the drug from prior use. Studies suggest that it may take days, depending on the type of sexual exposure, for the active drug in PrEP to build up to an optimal level for preventing HIV infection.
We applaud ongoing efforts like IPERGAY to identify PrEP dosing strategies that may be more acceptable than oral daily dosing for some individuals at risk, and could potentially lower costs. In addition, researchers are working to identify alternative delivery vehicles, including injectable PrEP and insertable products such as a vaginal ring. These are exciting avenues for research.
We encourage people at substantial risk for HIV infection to take steps to reduce their risk, including speaking with their doctor about PrEP. Daily, oral PrEP is recommended by CDC as an option for men who have sex with men, heterosexual men and women, and injection drug users.”