Two new studies published in the Lancet HIV support current guidelines recommending treatment of HIV-1 infection with tenofovir alafenamide-based regimens. Compared with tenofovir disoproxil fumarate (TDF), tenofovir alafenamide (TAF), a prodrug of tenofovir, reduces plasma concentrations of tenofovir by 90%. In clinical trials, TAF has demonstrated improvements in renal and bone safety because it enters cells more efficiently than TDF and can be administered at much lower doses. In these trials, investigators aimed to see whether viral suppression could be maintained when therapy was switched from a TDF-based regimen to a TAF-based regimen. 

The first study compared the safety and efficacy of switching to a single-tablet combination of rilpivirine, emtricitabine, and TAF versus remaining on a regimen containing rilpivirine, emtricitabine and TDF. Six hundred and thirty patients were randomized to either a TAF-based regimen (n=316) or the TDF-based regimen (n=314). By week 48, in both groups, 94% of patients maintained <50 copies per mL HIV-1 RNA (difference –0.3%, 95% CI –4.2 to 3.7), proving non-inferiority of TAF to TDF.  The number of side effects were similar between the groups (6% vs. 12% for TAF and TDF, respectively), and none of these were considered serious. 

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In the second study, the safety and efficacy of switching to a regimen containing rilpivirine, emtricitabine, and TAF was compared to remaining on a regimen containing efavirenz, emtricitabine, and TDF. In this study, 875 patients were randomly assigned to either the TAF-based regimen (n=438) or the TDF-based regimen (n=437). By week 48, viral suppression was maintained in 90% of the TAF group and 92% of the TDF group (difference –2.0%, 95% CI –5.9 to 1.8), indicating non-inferiority. Treatment-related side effects occurred in 13% of TAF patients versus 10% of TDF patients.

“These findings support guidelines recommending tenofovir alafenamide-based regimens, including coformulation with rilpivirine and emtricitabine, as initial and ongoing treatment for HIV-1 infection,” concluded the authors.

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