Background: Daily oral tenofovir-DF/emtricitabine (TDF/FTC)-based pre-exposure prophylaxis (PrEP) is effective for HIV prevention in MSM/TGW. Demonstration projects and clinical experience are informing real-world effectiveness and implementation challenges. Predictors of adherence and comparisons of self-report and objective measures were evaluated in the Los Angeles PATH-PrEP Demonstration Project.
Methods: HIV-uninfected MSM/TGW seeking HIV prevention services in Los Angeles were screened at two sites. Enrolled participants were assigned to PEP-based or PrEP-based cohorts based on self-reported risk. PrEP-participants were offered open-label daily oral TDF/FTC. Risk behavior and medication adherence were assessed over 48 weeks. PEP-participants were educated about PEP use and availability. If sexual risk increased, those assigned to PEP “escalated” into PrEP. Logistic regression determined predictors of PrEP adherence by self-report, MEMS, plasma TFV and DBS TFV-DP.
Results: Between May 2013 and June 2015, 823 individuals expressed interest; 301 enrolled. Median age was 34y; 50.7% non-Hispanic white, 12.4% non-Hispanic black, 28.1% Hispanic. Twenty-three (7.6%) were assigned to PEP, 19 (82.6%) escalated to PrEP. Intraerythrocytic TFV-DP levels were available from 274 participants (91%) at week 4; 85.8% had levels consistent with ≥4 doses/week. In multivariable analysis, non-Hispanic black participants (AOR 0.26, 95% CI: 0.09-0.78), reporting sex for trade in the past month (AOR 0.3, 95% CI: 0.09 - 0.98), and lower education (AOR 0.3, 95% CI: 0.09 - 0.97) were less likely to have protective TFV-DP levels. Other adherence measures variably predicted protective TFV-DP levels at week 4 (Figure). Predictive capacity did not differ by race/ethnicity.

Figure: Odds ratios for predictors of TVF-DP levels consistent with ≥4 doses/week in Dried Blood Spot (DBS) samples at Week 4
[Figure: Odds ratios for predictors of TVF-DP levels consistent with ≥4 doses/week in Dried Blood Spot (DBS) samples at Week 4]

Conclusions: There is significant community interest in PrEP among diverse MSM in Los Angeles. Plasma TFV and some self-reports of adherence may offer feasible and scalable surrogates of biomarker assessments in PrEP clinical protocols. Increased understanding of barriers to PrEP use by at-risk black populations, those with less formal education, and sex workers is needed to maximize PrEP impact.