SAN DIEGO – Recent sexual risk behavior and partnership type may be important predictors of pre-exposure prophylaxis in men who have sex with men, results from a 48-week study suggest.
“We know from other studies including iPrEX, the Partners PrEP, and the Demo project that individuals who report higher risk behaviors are more likely to be adherent to pre-exposure prophylaxis (PrEP),” lead study author Jill Blumenthal, MD, said in an interview in advance of an annual scientific meeting on infectious diseases.
Dr. Jill Blumenthal
As part of a PrEP California Collaborative Treatment Group demonstration study of 398 HIV-negative at-risk men who have sex with men and transgender women, Dr. Blumenthal, of the Antiviral Research Center at the University of California, San Diego, and her associates estimated their HIV risk score at baseline and week 48. Their score was estimated as the probability of seroconversion over the next year based on number of condomless anal sex acts with HIV+/unknown partners in the last month and any sexually transmitted infection diagnosed at study visit. The researchers categorized HIV risk score as low (less than 0.12), moderate (0.12-0.59) and high (greater than 0.59) risk based on population seroconversion probabilities. They assigned partnership as no/single HIV- partner, single HIV+ partner, or multiple partners of any serostatus in the past 3 months. They estimated PrEP adherence by intracellular tenofovir-diphosphate (TFV-DP) levels as a continuous variable at week 48.
Of 313 study participants who completed week 48, the researchers observed no significant change in HIV risk category from baseline to week 48 (low: 44% to 42%; moderate: 27% to 24%; high: 28% to 34%; P=0.25). However, there was a significant change in partnership type, with the proportion of those with no or single HIV- partnerships increasing from 1% to 9% (P less than 0.001). Univariate analysis revealed that moderate and high risk groups had higher TFV-DP levels, compared with the low risk group at week 48 (P = 0.018). Participants with no/single HIV- partner had significantly lower TFV-DP levels, compared with those who had one HIV+ partner or multiple partners (P = 0.007). On multivariable linear regression, only low risk partnerships remained significant where no/single HIV- partnerships were associated with lower TFV-DP levels (P = 0.014).
“Although more individuals in our study reported having either no or a single HIV-negative partners by the end of the study, there was no decrease in risk behavior based on reported condomless anal sex acts and laboratory-confirmed STIs over time,” Dr. Blumenthal said. “However, those risk behaviors did not increase either, arguing against risk compensation. Individuals with higher HIV risk behaviors and in riskier partnerships (those with either a single HIV+ or multiple partners) had higher TFV-DP levels at week 48 suggesting a maintained, strong motivation for PrEP adherence.”
She acknowledged certain limitations of the study, including the fact that the risk behavior score used in the analysis has not been validated in prospective studies of HIV incidence. “In addition, participants in the study were not allowed to start and stop PrEP, so less risky individuals may have remained in the study in the event they wanted to restart PrEP,” she said. Dr. Blumenthal disclosed that she is a Gilead Educational Grant recipient and that the study drug was provided by Gilead.