Emma Hitt, PhD

July 22, 2011

July 22, 2011 (Rome, Italy) — Switching patients from lamivudine/abacavir (3TC/ABC) to emtricitabine/tenofovir (FTC/TDF) appears to maintain virologic suppression while reducing the risk for viral failure in HIV infection, according to new findings from the SWIFT study.

Edwin DeJesus, MD, from the Orlando Immunology Center in Florida, presented the findings during a late-breaking session here at the 6th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention.

According to the researchers, several studies — including the ACTG 5202, ASSERT, and BICOMBO trials — reported higher rates of virologic failure with 3TC/ABC than with FTC/TDF, suggesting that switching from 3TC/ABC to FTC/TDF might help reduce viral load.

Dr. Edwin DeJesus

"As with the ROCKET 1 study, switching to FTC/TDF from 3TC/ABC resulted in significant improvement in fasting low-density-lipoprotein and total cholesterol levels," Dr. DeJesus told Medscape Medical News. "Importantly, significantly fewer subjects experienced virologic failure when switched to FTC/TDF, compared to those who remained on 3TC/ABC through week 48," he said.

The SWIFT study was a prospective multicenter randomized 48 week study. All subjects received 3TC/ABC with a ritonavir-boosted protease inhibitor, and had HIV RNA below 200 copies/mL for at least 3 months. They were then randomized to either continue 3TC/ABC (n = 156) or switch to FTC/TDF (n = 155). The primary end point was time to loss of virologic response (TLOVR), premature discontinuation, or antiretroviral modification (which was counted as virologic failure).

Early discontinuation rates were similar — about 11% — in the 2 treatment groups. By week 48, 86.5% of patients receiving FTC/TDF, compared with 83.3% receiving 3TC/ABC, maintained HIV RNA below 200 copies/mL by TLOVR, indicating the noninferiority of FTC/TDF to 3TC/ABC.

Transient viremic events at other time points were similar between groups, but fewer subjects in the FTC/TDF than in the 3TC/ABC group experienced virologic failure (3% vs 11%; P = .033). Among those who experienced virologic failure, low-level viremia at week 48 was observed in 3 subjects in the FTC/TDF group and in 8 in the 3TC/ABC group. None of the virologic failures demonstrated resistance mutations.

According to Dr. DeJesus, thesestudy results reemphasize why the Department of Health and Human Services and the IAS–USA guidelines list FTC/TDF as the "preferred" nucleoside reverse-transcriptase inhibitor backbone, and 3TC/ABC as an "alternative" backbone.

"This study confirms that there is an option for clinicians to switch virologically stable subjects to FTC/TDF from 3TC/ABC. Switching subjects to FTC/TDF will maintain virologic suppression while gaining benefits in improved lipid profile and reduce the risk of virologic failure," he said.

He added that the findings represent another reinforcement that it is okay to switch a patient who is virologically controlled, especially if we are going to gain some secondary benefits. In general, switches as a treatment strategy have been found to be safe when this concept is applied to the right patient — for example, patients with no baseline resistance," he said.

"It will be important to know how the randomization was performed in this study — if patients wanted to switch or not — as there is often a positive effect of the switch itself," said independent commentator Trevor Hawkins, MD, medical director of Southwest Care Center in Santa Fe, and associate clinical professor at the University of New Mexico.

"It does appear to confirm the superior potency of FTC/TDF over 3TC/ABC, which may be largely due to the FTC component, as it has a longer half-life and generates less M184V resistance than 3TC," he told Medscape Medical News. "However, I don't think it will convince providers to offer this switch to patients who are content with their regimen, and 3TC/ABC is already a second-line choice in the United States," he added.

The study was supported by Gilead Sciences. Dr. DeJesus reports serving as an advisor, consultant, or speaker and receiving research support for multiple commercial interests, including Gilead Sciences. Dr. Hawkins reports being a paid advisory board member of Gilead Sciences, Pfizer, and Tibotec Therapeutics; and receiving speaker honoraria from Bristol-Myers Squibb, Gilead Sciences, GlaxoSmithKline, Merck, Tibotec Therapeutics, Pfizer, and Virco.

6th International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention: Abstract WELBB03. Presented July 20, 2011.

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