Virological History Predicts Non-sustained Viral Suppression with Long-Acting Cabotegravir and Rilpivirine Therapy, independent of Pharmacokinetic Parameters

Background This study aimed to investigate factors contributing to non-sustained viral suppression, including intermittent viremia and persistent low-level viremia, during cabotegravir (CAB) plus rilpivirine (RPV) long-acting (LA) injectable therapy, with a focus on pharmacokinetics (PK). Methods A prospective cohort study was conducted on people with HIV (PWH) transitioning from stable oral antiretroviral therapy (ART) to bimonthly CAB+RPV LA. Standardized follow-up included close monitoring through blood sampling for plasma HIV-1 viral load (VL) and multiple plasma drug concentrations measurements to analyze the connection between PK parameters and virologic outcomes. Results Among 173 patients with a median (IQR) follow-up of 11.1(7.1-13.2) months and 789 pre-dose measurements, 38.7% experienced VL≥20 copies/mL, and 16.2% had levels ≥50 copies/mL. Intermittent viremia occurred in 34.7% of patients, and persistent low-level viremia in 4%. Virological failure developed in two cases. Predictors of non-sustained viral suppression included VL at HIV diagnosis [AHR: 1.49 per log10 VL, 95% CI: 1.04-2.12, P =.027], detectable viremia on oral ART [AHR: 2.45, 95% CI: 1.29-4.65, P =.006], and the level of viral suppression at transition [AHR: 0.38, 95% CI: 0.19-0.75, P =.004]. We found a significant association between low trough concentrations of CAB and RPV and episodes of detectable viremia exceeding 50 copies/mL. However, none of the assessed PK covariates predicted non-sustained viral suppression in multivariable models. Conclusion Non-sustained viral suppression in PWH transitioning from stable oral ART to CAB+RPV LA was linked to pre-existing factors before transition. Higher VL pre-ART and incomplete suppression on oral therapy increased the risk, independent of PK parameters.