A comment published in the Lancet Gastroenterology & Hepatology reports on two comparator studies which showed that tenofovir alafenamide (TA) is equally effective as tenofovir disaproxil fumarate (TDF) in hepatitis B (HBV) virological suppression, with a smaller decline in estimated glomerular filtration rate (eGFR) and bone mineral density (BMD).
Following a switch from TDF to TA:
- An increased estimated glomerular filtration rate (eGFR) (0.94 mL/min) was seen at week 48.
- A decrease of 2.74mL/min for those continuing on TDF.
- Increases in BMD were seen in the TA group.
- Decreased BMD in those continuing on TDF.
- Increase in cholesterol in the TA group, while TDF had a lipid-lowering effect.
- Treatment-induced HBV surface antigen (HBsAg) seroclearance at week 48; 0% for TA group and 2% for TDF.
TA also has renal toxicities; 1 per cent had eGFR decline during the four-year study period. Both groups showed increased proteinuria, although the increase was smaller for patients switching to TA. An improvement of eGFR in switch patients, peaking at 24 weeks and subsequently decreasing to 48 weeks, was unexpected.
The study population had moderate renal impairment and tolerated TDF for four years. New data will clarify the efficacy and safety of TA in HBV chronic patients with substantial renal impairment.