Efficacy and safety of boosted and unboosted atazanavir-containing antiretroviral regimens in real life: results from a multicentre cohort study

BACKGROUND: Atazanavir (ATV) has demonstrated high efficacy and safety in both treatment-naïve and treatment-experienced patients. Some comparative data are available on the durability of ritonavir-boosted (ATV/r) and unboosted formulations, but there are no data on clinicians' motivations for choosing one or another in everyday practice. The aim of this study was to evaluate the long-term efficacy of boosted and unboosted ATV in a cohort of treatment-experienced patients. METHODS: All patients included in the study were enrolled in an observational cohort within the Surveillance Cohort Long-Term Toxicity Antiretrovirals (SCOLTA) Project. Data on CD4 cell count, HIV viral load, metabolic parameters and adverse events of grade 3-4 are collected through an on-line system every six months. The duration of treatment with ATV was evaluated using the Kaplan-Meier curve and boosted and unboosted regimens were compared using the log-rank test. RESULTS: A total of 509 patients starting ATV as a component of their antiretroviral therapy were enrolled in the SCOLTA Project at the time of the study. Boosted ATV was received by 379 patients (74.5%) while 130 (25.5%) were treated with the unboosted formulation. The last therapeutic regimen did not influence the choice of ATV formulation. The mean observational time was 23.9 months. At the end of follow-up, 58.5% of patients on unboosted ATV and 58.1% of patients on ATV/r continued the treatment and no statistically significant differences were observed for ATV durability between the formulations or among the single causes of therapy interruption. CONCLUSIONS: Our results suggest that, in unselected clinical settings, ATV-containing antiretroviral therapy is durable and safe in both its formulations.