Once-daily abacavir/lamivudine and ritonavir-boosted atazanavir for the treatment of HIV-1 infection in antiretroviral-naïve patients: a 48-week pilot study.

Purpose: To assess the efficacy and safety of a once-daily (QD) regimen consisting of the co-formulation of abacavir/lamivudine (ABC/3TC) and atazanavir plus ritonavir (ATV-RTV) in antiretroviral (ART)-naïve patients with plasma HIV-1 RNA >5,000 copies/mL.

Method: This open-label, multicenter study conducted between September 2004 and June 2006 included 112 patients who received ABC 600 mg/3TC 300 mg and ATV 300 mg-RTV 100 mg QD. Drug switches were permitted for ABC hypersensitivity and ATV-related hyperbilirubinemia. Primary endpoints were proportion of patients achieving HIV-1 RNA <50 copies/mL at Week 48 and treatment discontinuation due to study drugs.

Results: A total of 111 patients were treated. At Week 48, the proportion of patients achieving HIV-1 RNA <50 copies/mL was 77% (85/111) by intent-to-treat (ITT) missing=failure, switch included response rate. Drug substitutions occurred in 8 (7%) patients for suspected ABC hypersensitivity reaction (HSR) and in 6 (5%) patients for ATV-related toxicities; only 1 patient discontinued study due to ABC HSR. Four patients met confirmed virologic nonresponse (HIV RNA >or= 400 copies/mL). Treatment-emergent drug resistance was rare, and no patient had virus that developed reduced susceptibility to ATV. Median change from baseline (95% confidence interval) in fasting lipids at Week 48 was 39 (26-66) mg/dL for triglycerides, 28 (22-38) mg/dL for total cholesterol (C), 14 (10.5-16) mg/dL for HDL-C, and 8 (2-16.5) mg/dL for LDL-C.

Conclusion: ABC/3TC and ATV-RTV QD is an effective and well-tolerated regimen in ART-naïve patients through 48 weeks, with a modest impact on fasting lipids.