June 6, 2016
People switching from tenofovir disoproxil fumarate (TDF, Viread) plus emtricitabine (FTC, Emtriva) to tenofovir alafenamide (TAF) plus FTC maintained a viral load below 50 copies/mL through 48 weeks as often as people who stayed with TDF/FTC, according to the results of a double-blind multicenter trial. Kidney and bone markers improved in the TAF group, and treatment discontinuations for drug-related adverse events were rare in either group.
TDF/FTC (Truvada) coformulated with or without other antiretrovirals has become a mainstay of antiretroviral therapy. TDF is associated with renal and bone toxicity, and TAF/FTC may offer a safer alternative because plasma tenofovir exposure is 90% lower with TAF than with TDF. Thus, less tenofovir reaches off-target cells with TAF than with TDF.
To compare the efficacy and safety of TAF/FTC and TDF/FTC, a North American/European team recruited adults who maintained a viral load below 50 copies/mL for at least six months with a regimen containing TDF/FTC, and randomized them to continue that regimen or to replace TDF/FTC with TAF/FTC. The 333 people randomized to TAF had a median age of 48 years, compared with 49 years in the 330 randomized to continue TDF. Respective proportions of men were 86% and 84%, men who have sex with men 70% and 67%, and whites 73% and 77%.
Significantly higher proportions of people in the TAF group than in the TDF group had 48-week improvements in proteinuria according to urine protein to creatinine ratio (75% versus 29%, P = .0019) and urine albumin to creatinine ratio (54% to 10%, P = .0002). Median 48-week change in estimated glomerular filtration rate measured 8.4 mL/min in the TAF group and 2.8 mL/min in the TDF group (P < .0001). Proximal renal tubulopathy did not develop in either study arm.
Mean bone mineral density (BMD) improved significantly with TAF versus TDF at the spine (1.527% versus -0.206%, P < .001) and the hip (1.135% versus -0.152%, P < .001). BMD status (normal, osteopenia or osteoporosis) improved significantly more at 48 weeks with TAF than with TDF at the hip (P = .012) and spine (P = .037). Fractures were rare (one in the TAF group and two in the TDF group) and related to trauma, not to study drugs. No one stopped treatment because of fracture.
The researchers conclude: "The combination containing tenofovir alafenamide has the potential to be an important NRTI backbone in the treatment of people with HIV, with safety advantages over that containing tenofovir disoproxil fumarate." In the United States coformulated TAF/FTC is licensed as Descovy, with elvitegravir/cobicistat as Genvoya and with rilpivirine as Odefsey.
Mark Mascolini writes about HIV infection.
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