6. New TAF Version of Tenofovir Approved in Combo Pill

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In November the U.S. Food and Drug Administration announced the approval of Gilead Sciences' Genvoya, a new single-tablet regimen containing the integrase inhibitor elvitegravir, the booster cobicistat, emtricitabine, and tenofovir alafenamide or TAF -- a new formulation that is easier on the kidneys and bones than the older tenofovir disoproxil fumarate (TDF).

Genvoya is the first approved product containing TAF, a pro-drug that delivers active tenofovir to HIV-infected cells more efficiently than the current TDF formulation (Viread, also in Truvada, Atripla, Complera, and Stribild). The new coformulation is similar to Stribild, but with 10 mg of TAF replacing 300 mg of TDF. TAF produces adequate intracellular drug levels with smaller doses, which means lower concentrations in the blood and less drug exposure for the kidneys, bones, and other organs and tissues.

Gilead's Study 104 and Study 111 did a head-to-head comparison of first-line treatment using either Genvoya or Stribild. As described at this year's Conference on Retroviruses and Opportunistic Infections, 92% of people taking Genvoya and 90% taking Stribild had undetectable viral load at 48 weeks. But TAF had less detrimental effects on the kidneys and bones. Various laboratory tests of kidney function favored the TAF regimen and people taking TAF had significantly smaller mean decrease in spine and hip bone mineral density.

Study 109 showed that people who switched from their current TDF-containing combination regimen to Genvoya maintained viral suppression while seeing improvement in kidney and bone health. As reportedat the International AIDS Society Conference, virological response rates were high overall: 97% with Genvoya and 93% with an existing regimen. People who switched to Genvoya saw improvements in kidney function markers and bone density, while those who stayed on TDF-containing regimens worsened.

Gilead has also requested approval of another TAF-containing single-tablet regimen containing rilpivirine (a successor to Complera) and a dual coformulation of TAF and emtricitabine (a successor to Truvada). Importantly, TAF has not yet been adequately studied for pre-exposure prophylaxis (PrEP), and it may not work as well because it does not build up as much at TDF in body tissues.

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