Effectiveness of ritonavir-boosted protease inhibitor monotherapy in the clinical setting: Same results as in clinical trials? The PIMOCS study group

Objectives: Ritonavir-boosted protease inhibitor monotherapy (PIMT) is a maintenance strategy that prevents nucleoside reverse transcriptase inhibitor toxicity and reduces costs. Some trials compare PIMT with combined antiretroviral therapy, but restricted selection criteria and low sample size hamper data extrapolation to routine practice. Here, we analyse the effectiveness and safety of PIMT in clinical practice. Methods: This was a retrospective, observational, multicentre study. Adult HIV-1 patients receiving PIMT with darunavir or lopinavir were included. A Cox regression model identified independent predictors for virological failure (VF). Results: A total of 664 patients (435 on darunavir/ritonavir and 229 on lopinavir/ritonavir) [74%male,median age of 54 years, one-third with previous protease inhibitor VF, CD4 nadir 189 cells/mm3 and 42%coinfectedwith hepatitis C virus (HCV)] were analysed. After a median follow-up of 16 months, 78% of patients (95% CI 74%-81%) remained free from therapeutic failure (TF) (change between ritonavir-boosted PIs not considered failure). At 12 months, by intention-to-treat analysis (change between ritonavir-boosted PIs equals failure), 83% of patients were free from TF (87%darunavir/ritonavir versus 77%lopinavir/ritonavir, P=0.001). Regarding VF, 88%of patients maintained viral suppression at 12 months (93% darunavir/ritonavir versus 88% lopinavir/ritonavir, P=not significant). CD4 nadir <200 cells/mm³ [hazard ratio (HR) 1.58, 95% CI 1.01-2.49] and undetectable viral load prior to PIMT<24 months (HR 1.86, 95%CI 1.20-2.91) were independent predictors for VF. Prior protease inhibitor failure, HCV coinfection and the protease inhibitor/ritonavir used were not associated with PIMT outcome. A total of 158 patients stopped PIMT, 6% due to adverse events. Two patients developed encephalitis. Conclusions: PIMTeffectivenesswas consistentwith data fromclinical trials. Viral suppression duration prior to PIMT and CD4 cell count nadir were independent predictors for PIMT outcome.