Background: Limited data are available on the use of unboosted atazanavir in combination with nucleoside reverse transcriptase inhibitors (NRTIs) in treatment-experienced HIV-infected patients.
Methods: We conducted a multicentre, retrospective study among patients with plasma HIV-1 RNA levels <50 copies/mL under antiretroviral therapy who switched to unboosted atazanavir + NRTIs between January 2002 and December 2008. Virological failure during follow-up was defined as a confirmed plasma HIV-1 RNA level >50 copies/mL. Baseline risk factors for virological failure were identified using Cox proportional hazards models.
Results: A total of 886 patients were analysed. At baseline, median age was 44 years, 71.5% were males and median CD4 cell count was 490 cells/mm(3). NRTIs used in combination with atazanavir were tenofovir, abacavir and emtricitabine/lamivudine in 36.9%, 44.1% and 94.4% of patients, respectively. Median follow-up was 21 months. The 3 year probability of virological failure was 20.1%. Only a history of virological failure under NRTIs [hazard ratio (HR) 1.63, P = 0.049] and under protease inhibitors (HR 2.04, P = 0.006) were significantly associated with the risk of virological failure. Among the 431 patients without a prior history of virological failure, the 3 year probability of virological failure was 11.3%, and only hepatitis C virus co-infection (HR 2.25, P = 0.026) and abacavir use (HR 0.43, P = 0.04) were associated with the risk of virological failure. Safety of the switch was satisfactory, with improvement of the lipid profile.
Conclusions: In patients with virological suppression and no prior history of virological failure, a switch to unboosted atazanavir in combination with NRTIs is associated with a low probability of virological failure and a good safety profile.