Tenofovir alafenamide (TAF) is a newly developed prodrug of tenofovir that can be used to treat patients with chronic hepatitis B (HBV) infection at a lower dose than tenofovir disoproxil fumarate (TDF) by delivering the drug more efficiently to hepatocytes. The authors have previously described the 48-week results from two ongoing, double-blind, randomised phase III trials in which TAF was found to be non-inferior to TDF in efficacy, with improved renal and bone safety. Now the authors report the 96-week outcomes for both trials. Patients with chronic HBV were randomised 2:1 to receive either 25 mg TAF or 300 mg TDF in a double-blinded fashion. One study enrolled HBeAg-positive patients and the other HBeAg-negative patients. By week 96, the differences in the rates of viral suppression were similar in HBeAg-positive patients receiving TAF and TDF (73% vs. 75%, respectively) and in HBeAg-negative patients receiving TAF and TDF (90% vs. 91%, respectively). In both studies the proportions of patients with alanine aminotransferase above the upper limit of normal at baseline that then normalised by week 96 were significantly higher in patients receiving TAF than in those receiving TDF. In the pooled safety population, patients receiving TAF had significantly smaller decreases in bone mineral density than those receiving TDF in the hip (mean % change -0.33% vs. -2.51%) and lumbar spine (mean % change -0.75% vs. -2.57%), as well as a significantly smaller median change in estimated glomerular filtration rate by Cockcroft-Gault method (-1.2 vs. -4.8 mg/dl). Therefore TAF remains as effective as TDF in patients with chronic HBV, with continued improved renal and bone safety, two years following initiation of treatment.
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