Tenofovir Alafenamide Fumarate: A New Tenofovir Prodrug for the Treatment of Chronic Hepatitis B Infection.

Tenofovir alafenamide fumarate (TAF), a new prodrug of tenofovir and a potential successor of tenofovir disoproxil fumarate (TDF), has been approved in the United States and Europe for treating adolescents and adults with chronic hepatitis B infection. TAF is formulated to deliver the active metabolite to target cells more efficiently than TDF at lower doses, thereby reducing systemic exposure to tenofovir. In patients with chronic hepatitis B, TAF appears to be as effective as TDF, with lower bone and renal toxicity. TAF has the potential advantages that dose adjustment is not required in patients with renal impairment, and monitoring can be less intense because of the better safety profile. Results from 2 large, randomized, phase 3 studies after 48 weeks of therapy have shown that TAF may be a good alternative to TDF for treating chronic hepatitis B. Whether the short-term benefits observed in these 48-week trials will translate into improvements in bone and renal health in patients receiving long-term treatment remains to be seen.