Evolution of the HIV-1 protease region in heavily pretreated HIV-1 infected patients receiving Atazanavir

Background: Previous in vitro studies indicated that Atazanavir (ATV) has a distinct resistance profile than other protease inhibitors (PIs). In treatment-experienced patients ATV resistance is characterised by the accumulation of at least four mutations among those that confer cross-resistance to the PIs. Objective: We studied the evolution of PIs resistance mutations in 10 HAART-failed patients undergoing ATV enrolled in an early access program. Study design: Virus genotypic resistance was determined from plasma collected at baseline and during treatment. HIV-RNA was extracted and the pol region amplified and sequenced. Genotypic data were used to determine drug susceptibility. Phylogenetic analysis was performed. Results: At baseline, genotypic data showed cross-resistance patterns to approved PIs in 6 patients. In two of these subjects new mutations (I54V and A71V) conferring cross-resistance emerged after 3 months of therapy. The I50L mutation was evidenced in one subject after 12 months of treatment. The "virtual" phenotype analysis mirrored the resistance profiles to ATV and other PIs and evidenced differences with tipranavir and darunavir. Conclusion: Genotype evolution within the protease region did not emerge at significant levels during salvage therapy of multidrug-experienced patients. ATV exhibited certain/same virologic effect on the majority of our patients.