Cabotegravir Maintains Protective Efficacy in the Setting of Bacterial Sexually Transmitted Infections: A Secondary Analysis of HPTN 083

Background. Sexually transmitted infections (STIs) have been shown to facilitate human immunodeficiency virus (HIV) transmission and acquisition. HPTN 083, a global clinical trial, demonstrated superiority of long-acting cabotegravir (CAB-LA) versus daily oral tenofovir disoproxil fumarate/emtricitabine (TDF/FTC) for HIV prevention among transgender women and cisgender men who have sex with men. This analysis assessed whether CAB-LA maintained protective efficacy when bacterial STIs (syphilis, rectal/urethral gonorrhea, and chlamydia) were present. Methods. STI events per 100 person-years were calculated, including by subgroups (age, race/ethnicity, gender, education, treatment arm, drug use, alcohol use, region/country, condom usage, partner number, marital status, baseline STI). Association between baseline factors and STI incidence was modeled using Poisson regression. Cox proportional hazards modeling with STI status as a time-varying covariate was used to evaluate potential interactions between STI status and the relative efficacy of CAB-LA versus TDF/FTC. Findings. Among 3859 participants, overall STI incidence rate was 50.7 infections/100 person-years. STIs were diagnosed in 1562 (40.5%) participants; 79% of STIs occurred in 25% of the participants. STI incidence was not different by preexposure prophylaxis arm. In the final multivariable model, age, region, race, education level, marital status, and baseline STI were associated with incident STI (P < .05). HIV incidence was lower with CAB-LA versus TDF/FTC with or without STIs (hazard ratios 0.37 and 0.31, respectively), with no significant interaction between STIs and the HR for HIV incidence (P = .75). Conclusions. In a large preexposure prophylaxis trial with high STI incidence, CAB-LA maintained robust protective efficacy relative to TDF/FTC in the setting of bacterial STIs.