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-naive 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.