Tenofovir alafenamide (TAF) treatment of HBV, what are the unanswered questions?

Tenofovir disoproxil fumarate (TDF), an ester prodrug of tenofovir (TFV), is one of the recommended drugs for chronic hepatitis B (CHB) patients. However, reduced kidney function and loss of bone mineral density have been reported in some CHB patients treated with TDF. Consequent to these safety issues, tenofovir alafenamide (TAF) [Vemlidy®], a phosphonate prodrug of TFV, was developed for the treatment of CHB patients. Areas covered: The favourable pharmacological profile of TAF allows a marked reduction in dosage (25 mg/day) thus reducing systemic exposure to tenofovir and improving the bone and renal safety, keeping however the same virological efficacy, compared to TDF 300 mg/day. In two ongoing 96-week phase III trials in mainly treatment-naive HBeAg-positive or -negative patients, TAF showed similar viral suppression but was associated with significantly higher alanine aminotransferase normalization rates and more favourable renal and bone safety compared to TDF. In a 48-week TAF switch study enrolling patients treated with TDF for 96 weeks, glomerular, tubular and bone safety parameters rapidly improved while virological suppression was maintained. Expert commentary: Waiting long-term large scale clinical practice studies aimed to confirm these advantages, TAF represents an helpful treatment option for both naïve and TDF-exposed CHB patients.