Tenofovir Alafenamide: A Review in Chronic Hepatitis B.

Tenofovir alafenamide (AF) [Vemlidy], an oral prodrug of tenofovir, was developed to optimize the antiviral potency and clinical safety of the active moiety tenofovir diphosphate (selective reverse transcriptase nucleotide inhibitor). In two identically designed, ongoing, multinational trials in treatment-naive and -experienced adult patients with hepatitis B e antigen (HBeAg)-positive or -negative chronic hepatitis B virus (HBV) infection, once-daily tenofovir AF 25 mg provided effective and sustained viral suppression (120-week analysis), and was generally well tolerated. In the primary 48-week analysis, tenofovir AF was noninferior to once-daily tenofovir disoproxil fumarate (DF) 300 mg in terms of the proportion of patients achieving viral suppression (HBV DNA <29 IU/mL) and was associated with significantly higher alanine aminotransferase (ALT) normalization rates than tenofovir DF based on AASLD criteria (but not central laboratory criteria). In pooled analyses and/or individual trials, ALT normalization rates by AASLD and central laboratory criteria were significantly higher in tenofovir AF than tenofovir DF recipients at most assessed timepoints up to 96 weeks. Given the bone and renal safety concerns associated with long-term tenofovir DF treatment, the more favourable pharmacological profile of tenofovir AF permits a marked reduction in the dosage of this tenofovir prodrug and thereby reduces systemic exposure to tenofovir, potentially improving the bone and renal safety of tenofovir AF versus tenofovir DF. Long-term clinical experience will more definitively establish the relative bone and renal safety of these tenofovir prodrugs. With its potential for an improved safety profile, tenofovir AF is an important emerging first-line option for the treatment of chronic HBV infection in adults and adolescents (aged ≥12 years and with a bodyweight of ≥35 kg).