TAF and TDF Compared for Kidney, Bone Toxicity in Black HIV+ Patients

SAN DIEGO, CA—Including tenofovir alafenamide (TAF) in single-tablet elvitegravir/cobicistat/emtricitabine (E/C/F/TAF) is associated with reduced renal and bone toxicity compared to tenofovir disoproxil fumarate (TDF)-containing single-tablet (E/C/F/TDF) therapy, according to an analysis of data from two Phase 3 trials, reported at IDWeek 2015.

TDF has been associated with nephrotoxicity, a potential problem for adult black patients, who are disproportionately affected by both HIV and chronic kidney disease. TAF was developed for the treatment of HIV and chronic hepatitis B infection.

In treatment-naïve black adults, the TAF-containing pill was associated with “significant improvements in renal and bone safety” over TDF, with similarly high levels of efficacy by Week 48, reported lead study author David Alain Wohl, MD, University of North Carolina at Chapel Hill, Chapel Hill, NC, and coauthors.

“Rates of virologic success and adherence were high for black [patients] but were lower than those for non-black patients,” Dr. Wohl added. “These results support the use of E/C/F/TAF for the initial treatment of HIV-1 in black and non-black adults.”

His team conducted analyses of 48-week efficacy and safety data, comparing TAF and TDF in treatment-naïve black and non-black patients, from two randomized Phase 3 studies that had enrolled adults with estimated glomerular filtration rates (eGFR) ≥50mL/min.

Baseline characteristics among black patients were balanced between treatment arms, Dr. Wohl noted.

“At Week 48, rates of virologic success were numerically (though not statistically) higher for black [patients] on TAF vs. TDF (88% vs. 83%), but significantly lower than in non-black patients (94% TAF vs. 93% TDF),” Dr. Wohl reported. In the TAF study arm, the overall lower rate of success in black patients was primarily driven by lack of virologic data (6.7% black vs. 3.1% non-black, P=0.018), he noted, with “most discontinuing study drug due to reasons other than adverse events.”

“In the TDF arm, both virologic failure (P=0.003) and missing virologic data were higher for black patients vs. non-black patients (P=0.005),” he noted. “Pill-count adherence was also lower in black patients vs. non-black patients in both the TAF (mean 95.4% vs. 97.3%; P<0.001) and TDF groups (95.1% vs. 97.6%; P<0.001).”

Both TAF and TDF were well-tolerated and proximal renal tubulopathy was not observed, Dr. Wohl reported.

“Among black [patients], decline in median eGFR was significantly less and median decreases in proteinuria were numerically greater in the TAF group,” he reported. “Black [patients] experienced similar bone mineral density declines compared with non-black [patients], while those on TAF had less spine and hip bone mineral density loss vs. TDF in both populations.”

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