6th IAS Conference On HIV Pathogenesis, Treatment and Prevention


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WELBB03 - Oral Abstract

SWIFT study: switching from lamivudine/abacavir (3TC/ABC) to emtricitabine/ tenofovir DF (FTC/TDF) maintained efficacy and reduced virologic failure

Presented by Edwin DeJesus (United States).

R. Campo1, E. DeJesus2, H. Khanlou3, H. Wang4, K. White4, L. Dau4, J. Flaherty4, T. Fralich4

1University of Miami School of Medicine, Division of Infectious Diseases, Miami, United States, 2Orlando Immunology Center, Orlando, United States, 3AIDS Healthcare Foundation, Los Angeles, United States, 4Gilead Sciences, Foster City, United States

Background: Comparative studies (ACTG 5202, ASSERT, and BICOMBO) reported higher rates of virologic failure (VF) with 3TC/ABC vs FTC/TDF. This represents an important consideration for possibly switching from 3TC/ABC to FTC/TDF.
Methods: Prospective, multicenter, randomized 48 week study to evaluate the safety and efficacy of a strategy to switch subjects from 3TC/ABC to FTC/TDF. Subjects receiving 3TC/ABC +PI/r with HIV RNA < 200c/mL ³ 3 months (and < 200c/mL at screening by TaqMan assay) were randomized (1:1) to either continue 3TC/ABC or switch to FTC/TDF. Subjects were stratified by PI/r (LPV/r vs. other) and co-morbidities. Primary endpoint was time to loss of virologic response (TLOVR, premature discontinuation, or ARV modification = failure). VF is defined as confirmed rebound, or the last one on study drug > 200 copies/mL.
Results: 311 subjects were treated (FTC/TDF 155, 3TC/ABC 156). Overall, baseline characteristics were similar between the arms: 85% males, 28% African Americans, median age 46 years, median CD4 532 cells/mm3. Early discontinuation rates were also similar (11%). Through Week 48, 86.5% on FTC/TDF and 83.3% on 3TC/ABC maintained HIV RNA < 200 copies/mL by TLOVR (treated; NC=F), with a treatment difference (95% CI) of 3.1% (-5% to 11%) indicating non-inferiority of FTC/TDF to 3TC/ABC (Δ=12%). Fewer subjects on FTC/TDF vs 3TC/ABC experienced VF (3 vs 11; p=0.033). Of the 14 VF subjects, low level viremia at Week 48 occurred in 3 subjects in the FTC/TDF arm compared to 8 in the 3TC/ABC arm, while transient viremic events at other time points were similar between arms. An additional 3 subjects on 3TC/ABC experienced VF (2 early discontinuations, 1 early VF that resuppressed). Three of 14 on 3TC/ABC were genotyped and all lacked resistance mutations.
Conclusion: Switching subjects from 3TC/ABC to FTC/TDF maintained virologic suppression while reducing the risk of VF.

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