Using antibiotics to prevent STIs effective found in early SF study results

To curb the trends, sexual health advocates have been searching for new strategies to help people prevent bacterial infections. Condoms are one option, but many people don’t use them consistently, Luetkemeyer said.

Researchers in Europe began studying the use of antibiotics as prevention about five years ago, following the model of PrEP, or antiviral pre-exposure prophylaxis to prevent HIV infection. The UCSF trial, done jointly with the University of Washington, is the first to study the approach in the US

The DoxyPEP trial is ongoing, with nearly 650 participants enrolled at two clinics in San Francisco and two more in Seattle. All participants are men who have sex with men or transgender women who had at least one sexually transmitted infection in the previous year, and who are living with HIV or are on PrEP.

Participants were enrolled in one of two study arms: one with access to antibiotics for prevention, the other a control group. The antibiotic group was given a three-month supply of doxycycline, a common antibiotic to treat sexually transmitted infections, and told to take one 200 mg pill within three days of having oral, anal or vaginal sex without a condom. They could get refills on the prescription as often as they needed.

Luetkemeyer said she can’t yet reveal specific outcomes from the trial. But a safety and ethics board assigned to regularly monitor the results found this month that the antibiotics were so effective at preventing infections that it would be problematic to keep sorting participants into the control group.

Researchers stopped enrolling people in the trial earlier this month, and are now offering DoxyPEP to all participants in the control group, Luetkemeyer said. Participants will continue to be monitored for 12 months.

Taking antibiotics to prevent infections is not without potential risk, both in terms of developing drug-resistant pathogens and upsetting an individual’s microbiome, the complex system of bacteria that occupy the gut, Luetkemeyer said. Over the past decade, gonorrhea already has become more difficult to treat in some cases due to drug resistance. Infectious disease experts have already identified a few cases of gonorrhea around the world that were resistant to all antibiotics.

It’s possible that the initial study of DoxyPEP won’t be able to determine if drug resistance develops from using antibiotics for prevention, and more trials will almost certainly be needed, Luetkemeyer said. Still, she and other health care providers say they’re encouraged by what they’ve seen so far.

“HIV PrEP really demonstrated the power of biomedical prevention in the field of sexual health, and certainly has fueled enthusiasm for identifying a biomedical prevention solution for other STIs,” said Dr. Stephanie Cohen, medical director of San Francisco City Clinic, one of the DoxyPEP trial sites.

She noted there are key differences between DoxyPEP and HIV PrEP that could influence whether people are interested in the prevention: HIV is a much more dangerous illness than other sexually transmitted infections, and the antiviral used for PrEP is less likely than doxycycline to cause secondary harms like drug resistance. But City Clinic clients already have expressed interest in DoxyPEP, and Cohen believes some people will benefit from having the option.

“Some community members have decided, ‘I really am tired of getting an STI and the discomfort, and having to tell my partners,’” Cohen said. “I think there is a lot of enthusiasm among some communities for this strategy.”