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GLASGOW, Scotland -- Since the advent of pre-exposure prophylaxis (PrEP), there has been an increase in sexually transmitted infections (STIs) among men who have sex with men (MSM), and a need for new strategies for prevention and treatment in this population, a researcher said here.

Strategies to potentially cut down on the incidence of disease in this population include increased promotion of condom use, using vaccines where applicable, so-called "test and treat" strategies, as well as new therapies especially for bacterial STIs, according to Jean-Michel Molina, MD, of the University of Paris Diderot in Paris.

"We have to rely on a number of different strategies. There is no magic bullet," Molina said at the Lock Lecture at the International Conference on HIV Drug Therapy (HIV Glasgow).

He cited a recent article in the U.S. edition of that questioned whether or not PrEP is "propelling the STI epidemic," due to a decline in condom use among this population. Molina pointed to recent research that found a decrease in condom use coincided with an increase in STIs, but a reduction in new HIV diagnoses.

Molina said that promotion of condom use, along with counseling and behavioral interventions, may have an impact. One recent study found a number of factors in predicting STIs among PrEP users, including ages <25, more than five casual partners at baseline, as well as an increase in casual partners. He suggested that one aspect of counseling could potentially focus on reducing the number of casual partners, to reduce the risk of contracting STIs.

An additional intervention would be partner notification, Molina said. He discussed the development of an app that would anonymously send a message from the user to the phones of their sexual partners, and sync a user's lab tests and test results to the partner's. All previous partners in the network would then receive a notification if they were exposed to HIV or STIs, along with information about linkage to care. Molina said a pilot study for this app (WeFLASH) is expected to begin next year.

Another strategy is the use of vaccines, which are applicable to such viral infections as hepatitis A and B, but not bacterial STIs, like gonorrhea, chlamydia, and syphilis. But new solutions could emerge from unexpected sources, such as cross-protection against gonorrhea from the meningococcal group B vaccine. Molina said in the meningococcal B vaccine, Bexsero, 2 of 3 recombinant proteins are shared with Neisseria gonorrhoeae.

Post-exposure prophylaxis (PEP) is another potential strategy examined within a cohort that was part of the IPERGAY study. HIV-negative high-risk MSM received either on-demand PEP with doxycycline 24 hours after sex, or no PEP. Molina said doxycycline was chosen due to concerns about low-level resistance from N. gonorrhoeae in France to tetracycline. Overall, the intervention reduced incidence of bacterial STIs by 47%, with about a 70% reduction in chlamydia and syphilis, though there was no effect on gonorrhea, Molina said.

But he added that "antibiotic prophylaxis is not recommended, and we have to wait for additional studies to assess the benefit/risk ratio."

Existing therapies also may not be the answer, with Molina discussing three new therapies -- two oral type II topoisomerase inhibitors and one oral fluoroketolide in development for the treatment of gonorrhea, particularly drug-resistant strains of gonorrhea.

"Test and treat" was another potential strategy, which Molina said has worked with hepatitis C. He cited recent research that showed this type of strategy worked among MSM in Switzerland.

For bacterial infections, home-based testing was suggested, with one intervention among sexually active adults finding that about 30% who received a free home-based testing kit had a substantially higher rate of screening compared with the <9% who visited a primary care provider for testing.

More frequent testing of MSM on PrEP could increase the rates of STI diagnosis, with one modeling study finding that testing once a month could prevent over 40% of N. gonorrhoeae and Chlamydia trachomatis infections over a decade.

"But it's just a model, right? We don't have good data that shows more frequent testing was associated with an impact on infection," Molina said.

He added that new interventions, frequent testing, early diagnosis and treatment, and better partner notification should help reduce incidence of STIs, but STIs among patients "should not be an excuse to deny PrEP access."

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