Does Abacavir/3TC Still Have a Role in First-Line Therapy for HIV?

HIV clinical practice guidelines previously included both abacavir/3TC and tenofovir/FTC as preferred options for once-daily, fixed-dose, dual-NRTI backbone therapy in treatment-naive patients. However, in November 2008, abacavir/3TC was demoted from a “preferred” to an “alternative” option (JW AIDS Clin Care Nov 6 2008), largely on the basis of data from the ACTG 5202 trial. In that trial, abacavir/3TC (together with efavirenz or boosted atazanavir) was associated with a shorter time to virologic failure than tenofovir/FTC (also together with efavirenz or boosted atazanavir) in patients with pretreatment viral loads ≥100,000 copies/mL (JW AIDS Clin Care Dec 29 2008).

Results are now in from the double-blind, multicenter HEAT trial, in which 688 treatment-naive patients were randomized to receive either tenofovir/FTC or abacavir/3TC, each in combination with once-daily lopinavir/ritonavir, for 96 weeks. This noninferiority study was funded by the manufacturer of abacavir/3TC.

HIV suppression to a viral load <50 copies/mL at 48 weeks (the primary endpoint) was achieved by 68% of patients in the abacavir/3TC group and by 67% of those in the tenofovir/FTC group. At 96 weeks, suppression rates were 60% and 58%, respectively. This similar efficacy of the two regimens held in subgroups stratified by baseline viral load (<100,000 vs. ≥100,000 copies/mL) and by baseline CD4 count (<50 vs. ≥50 cells/mm³). The two treatment groups also had similar rates of virologic failure and of drug discontinuation because of adverse events.