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

In the HEAT randomized trial, abacavir/3TC was noninferior to tenofovir/FTC when each was used in combination with lopinavir/r in treatment-naive patients, regardless of pretreatment viral load.

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.

Comment: In the HEAT trial, abacavir/3TC was noninferior to tenofovir/FTC when each was given with lopinavir/r in treatment-naive patients, regardless of pretreatment viral load. Why the results of the HEAT trial differed from those of ACTG 5202 is not clear, but distinct study designs and patient management strategies may have been contributing factors. The HEAT trial data indicate that, when used in combination with boosted lopinavir, fixed-dose abacavir/3TC is a viable option for initial treatment of HIV-infected patients.

— Charles B. Hicks, MD

Published in Journal Watch HIV/AIDS Clinical Care July 20, 2009

Citation(s):

Smith KY et al. Randomized, double-blind, placebo-matched, multicenter trial of abacavir/lamivudine or tenofovir/emtricitabine with lopinavir/ritonavir for initial HIV treatment. AIDS 2009 Jun 17; [e-pub ahead of print].

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