Abacavir/Lamivudine Fixed-Dose Combination With Ritonavir-Boosted Darunavir: A Safe and Efficacious Regimen for HIV Therapy

Background: Current treatment guidelines recommend the use of tenofovir (TDF) and emtricitabine (FTC) along with a third agent to treat HIV-positive adults. However, other treatment options, including the use of abacavir (ABC) and lamivudine (3TC) when used with ritonavir-boosted darunavir (DRV/r), have rarely been studied. Objective: We evaluated the safety and efficacy of the coformulation of ABC/3TC administered with DRV/r in treatment-naive and treatment-experienced patients. Methods: HIV-infected adults who received an open-label combination of ABC/3TC/DRV/r were followed in a community clinic in Montreal. Patients had no resistance to any of the compounds in their regimen. Viral load (VL), CD4 cell count, AST, ALT, and creatinine levels were examined throughout the 48 weeks of follow-up. Results: Sixty-seven patients with a mean age of 45 years were enrolled. Two did not return for follow-up and were excluded. Thirty-five (52%) were treatment-experienced and the remaining were treatment-naive. HLA-B(star)5701 test results were available for 56 patients and none were positive. At baseline, mean VL was 4.8 log for treatment-naive and 2.3 log for experienced patients. Twelve patients discontinued the study regimen prior to reaching the endpoint. At week 48, 79% had a VL <50. Median CD4 cell gain was higher among treatment-naive patients (273 cells) than among treatment-experienced patients (102 cells) (P = .002). No patient experienced any grade 2 or higher liver enzyme elevation throughout the study. Conclusions: The new combination of ABC/3TC/DRV/r demonstrates a high rate of antiviral activity with no major toxicity. The drug combination appears to be generally safe and well tolerated.