Abstract Background The impact of pharmacokinetic variability of cabotegravir (CAB) and rilpivirine (RPV) long-acting (LA) injectable therapy on virological outcomes remains controversial. This study aimed to characterize the variability of CAB and RPV trough concentrations (Ctrough) and to identify the predictors of suboptimal exposure and virologic failure (VF) in a large real-world cohort. Methods We conducted a multicenter observational study including people with human immunodeficiency virus type 1 (HIV-1) initiating LA-CAB/RPV as maintenance therapy from January to December 2022, in whom CAB and RPV plasma Ctrough were determined as part of therapeutic drug monitoring (TDM). Results A total of 1674 CAB and 1687 RPV Ctrough measurements were collected from 736 people with HIV-1 (PWH). Significant interindividual variability in concentrations was observed. At month 1/month 3, 20%–30% of PWH had Ctrough 1120 ng/mL for CAB and 32 ng/mL for RPV. Predictors of lower Ctrough were body mass index (BMI) ≥30 kg/m2 and female sex at month 1, and only male sex at steady state. After a median follow-up of 12 (interquartile range, 9–16) months, VF occurred in 2.5% of PWH. At month 6 and month 12, VF was significantly associated with the presence of at least 2 risk factors (obesity, suboptimal Ctrough) (odds ratio OR, 4.6, P = .047; OR, 5.15, P = .014), and CD4 nadir (OR, 0.56, P = .008; OR, 0.5, P = .001). Conclusions Our large real-world study confirms significant variability in CAB and RPV exposure, with BMI and sex as key predictors of lower Ctrough. Suboptimal CAB and RPV Ctrough, particularly in people with obesity, increases the risk of VF during the first year of treatment, highlighting the usefulness of TDM in clinical practice.
Néant et al. (2025) studied this question.