Pre-exposure HIV prophylaxis most effective in subgroup of transgender women, MSM
By Lorraine L. Janeczko
NEW YORK (Reuters Health) - Transgender women and men who have sex with men (MSM), who also have receptive anal intercourse without a condom, benefit most from pre-exposure antiretroviral drugs, whether or not they perceive their partners to be HIV negative, according to new research.
"Receptive anal sex without a condom with partners of unknown serostatus contributed to more than half of all new HIV infections," the authors write in their secondary analysis of the iPrEx (Pre-Exposure Prophylaxis Initiative) trial, published online March 7 in The Lancet Infectious Diseases.
"The simplest and perhaps most effective strategy for identifying MSM and transgender women who may benefit most from pre-exposure prophylaxis would be to ask them two questions. In the past 3 months, have you had sex with men, women, or both? And in the past 3 months, have you had receptive anal sex without a condom?" they write.
Lead author Dr. Susan P. Buchbinder of University of California, San Francisco, advised in an email to Reuters Health, "Pre-exposure prophylaxis (PrEP), a daily regimen of Truvada (co-formulated emtricitabine/tenofovir) can prevent HIV acquisition in MSM at risk for HIV infection, but it is vastly under-utilized."
"PrEP should be prioritized for MSM who have condomless receptive anal sex (which clinicians can frame as 'being a bottom without a condom') in any situation outside of a mutually monogamous relationship with an HIV negative partner. This activity was shown to drive nearly 2/3 of new infections among MSM in the iPrEx study, and one infection could be averted per year for every 36 MSM put on Truvada," she said.
The authors recommend that, for maximum effect, PrEP should be targeted to groups of people who account for the largest proportion of infections (the population-attributable fraction, or PAF) and whose number needed to treat per year to avert one infection (NNT) is lowest.
To find which transgender women and MSM should be offered PrEP, Dr. Buchbinder and her colleagues conducted a secondary analysis of the iPrEx randomized controlled efficacy trial of pre-exposure prophylaxis with coformulated tenofovir disoproxil fumarate and emtricitabine in 2499 transgender women and MSM.
Over almost 2.5 years at 11 trial sites in six countries, they enrolled participants who were male at birth and at least 18 years old, and they followed them for almost 3.5 years from the first enrollment date.
They randomly assigned participants to receive either active PrEP (n=1251) or a placebo (n=1248) daily.
During follow-up, 83 participants in the placebo group became infected with HIV.
Those who reported receptive anal intercourse without a condom seroconverted significantly more frequently than those who reported no anal sex without a condom (adjusted hazard ratio, 5.11).
The overall PAF for transgender women and MSM who reported receptive anal intercourse without a condom was 64%, and the prevalence was 60%.
Most of this risk came from receptive anal intercourse without a condom with partners who had unknown serostatus (PAF 53%, prevalence 54%, AHR 4.76). This contrasts with the PAF of 1% for receptive anal intercourse without a condom with a HIV-positive partner (prevalence 1%, AHR 7.11, not significant). The NNT was 62 overall.
NNTs were lowest for transgender women and MSM who self-reported receptive anal intercourse without a condom (36), a sexually transmitted infection (41), or cocaine use (12). Those who had one partner and insertive anal sex without a condom had the highest NNTs (100 and 77, respectively).
Dr. Connie Celum, who studies HIV prevention at University of Washington in Seattle, told Reuters Health by email, "The findings are surprising in that the number needed to treat is relatively low based on identifying MSM and TG women who report receptive anal sex without a condom in the past 3 months, regardless of their partner's serostatus." Dr. Celum was not involved in the study.
Dr. Jared M. Baeten said, "In a very smart, rigorous and elegant way, the authors used data from this clinical trial to define subpopulations who are most at risk of HIV and who would get greatest individual and public health benefit from pre-exposure prophylaxis."
Dr. Baeten, also from University of Washington, co-authored an editorial accompanying the study.
"That a single prioritization question could open up discussion about life-saving and health-saving strategy is surprising and powerfully reassuring," he said.
"Broadly speaking, this paper and a lot of discussion currently going on in the scientific, advocacy, and policy communities motivates a new discussion about pre-exposure prophylaxis," Dr. Baeten said.
"The question is no longer about trying to figure out whether PrEP works in prevention, but is shifting now to how to make it work in public policy and have an impact for preventing as many HIV transmissions as possible, particularly for populations most highly infected by HIV," he added.
Dr. Buchbinder said, "Although highly effective in serodiscordant relationships, PrEP accounted for only 2% of all infections in the iPrEx study. If we want to have a bigger population level impact, we need to expand PrEP to include men having condomless receptive anal sex, men diagnosed with sexually transmitted infections, and men using drugs."
"Some raise concerns about offering medication in lieu of behavioral interventions, but we know that behavior change is difficult, whether related to smoking, diet, exercise, contraception, or prevention of sexually transmitted infections," she said.
The study drug was donated by Gilead Sciences. Dr. Buchbinder said she and several other authors have received funds from Gilead. Dr. Baeten stated that he has led studies in which the study drug was donated by Gilead Sciences but has no conflict of interest with the current study.
SOURCES: http://bit.ly/OOU3EB and http://bit.ly/1leW0YU
Lancet Infect Dis 2014.
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