Switch from a ZDV/3TC-based regimen to a completely once daily (QD) regimen of emtricitabine/tenofovir DF fixed dose combination plus a third QD agent (SONETT)

OBJECTIVES: To assess the efficacy and safety of a treatment switch from a twice-daily (BID) regimen containing zidovudine (ZDV) and lamivudine (3TC) plus a third agent to a once daily (QD) regimen containing the fixed-dose combination of tenofovir DF/emtricitabine (TDF/FTC, Truvada(®)) plus a divergent third QD agent in HIV-1 infected patients. METHODS: Prospective, 48-week, non-randomised, single-group, open-label, study. Fifty-one patients on stable ZDV/3TC-containing HAART, with HIV-1 RNA < 50 copies/ml and CD4+ T-cell count > 50 cells/μl, were switched to TDF/FTC plus a third agent. Plasma HIV-1 RNA, CD4+ and CD8+ T-cell counts were assessed at baseline and weeks 4, 12, 24, 36 and 48 post-switch. RESULTS: During the 48-week study, 10 patients discontinued prematurely, including three due to adverse events (AEs). At week 48, plasma HIV-1 RNA was < 50 copies/ml in 40 patients (78.4%). No patient experienced virological failure (defined as HIV-1 RNA ≥50 copies/ml at two consecutive post-baseline measurements) during the study. Immunologic control was maintained, with no significant changes in CD4+ or CD8+ T-cell counts. A statistically significant improvement from baseline in haemoglobin level was observed at week 48 (median change 0.8 g/dl; p < 0.001). There was also a statistically significant decrease in total cholesterol concentration at week 48 (-26.0 mg/dl; p = 0.001) in a subset of patients (n = 22) entering the study with elevated total cholesterol. Treatment was well tolerated and no treatment-related grade 3 or 4 AEs were seen. CONCLUSIONS: Results from this study support switching from a ZDV/3TC-containing HAART regimen to a completely QD regimen of TDF/FTC plus a third agent. Virologic and immunologic control are maintained, with apparent benefits in haemoglobin.