Partnership-Type and Risk Behaviors Can Predict PrEP Adherence in Men Who Have Sex With Men

Researchers have uncovered a novel method for determining how men who have sex with men (MSM) will adhere to pre-exposure prophylaxis (PrEP), according to a recent study.

Jill Blumenthal, MD, of the University of California, San Diego, and colleagues found that individuals with higher human immunodeficiency virus (HIV) risk behaviors and higher risk partnerships had higher tenofovir-diphosphate (TFV-DP) levels, suggesting that these individuals maintained stronger motivation for PrEP adherence than those who avoided such behaviors and partnerships.

"I think it's reassuring to both patients and physicians that those with high risk behaviors and partnerships are likely to be more adherent, suggesting that many are recognizing their risk. Since those who engage in risky behaviors may take PrEP more consistently, providers have the opportunity to test for STIs perhaps more frequently," Blumenthal said in an interview with MD Magazine.

While previous studies had shown that individuals who engaged in higher risk behaviors were more likely to maintain adherence to PrEP, it was initially unclear whether partnership type also affected adherence. To find out, researchers examined the effect of recent HIV risk behaviors and partnership type on PrEP adherence in MSM in the CCTG 595 study, a 48-week PrEP demonstration study of 298 HIV-at-risk MSM.

At baseline and week 48, HIV risk 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 infections (STI) diagnosed at study visit. HIV risk score was categorized as low risk (<0.12), moderate risk (0.12-0.59) and high risk (>0.59) based on population seroconversion probabilities.

Partnership type was assigned as no/single HIV- partner, single HIV+ partner, or multiple partners of any serostatus in the past 3 months. PrEP adherence was estimated by intracellular TFV-DP levels as a continuous variable at week 48. Statistical methods included McNamara’s test, Wilcoxin rank sum test and linear regression model, where appropriate.

Of 313 MSM who completed week 48, there was 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). There was a significant change in partnership type, with the proportion of those with no or single HIV-partnerships increasing (1 to 9%, p=0.001).

In univariate analysis, moderate and high risk groups had higher TFV-DP levels than the low risk group at week 48 (p=0.019. Participants with no/single HIV- partner had significantly lower TFV-DP levels than those with one HIV+ partner or multiple partners (p=0.007). In a multivariable linear regression model, only low risk partnerships remained significant where no/single HIV- partnerships were associated with lower TFV-DP levels (mean difference= -344 fmol/punch [-617, -71], p=0.014).

Although there was a shift in partnership type towards lower risk partnerships, objective HIV risk behavior remained stable over time. Overall, individuals with higher HIV risk behaviors and higher risk partnerships had higher TFV-DP levels, suggesting a strong motivation for PrEP adherence. Because of this, the authors said, recent sexual risk behavior and partnership type may both be important predictors of PrEP adherence in MSM.