Eight-year Results from Two Randomized Phase 3 Trials of Tenofovir Alafenamide for Chronic Hepatitis B Virus Infection in China.

BACKGROUND AND AIMS: Tenofovir alafenamide (TAF) has demonstrated comparable efficacy to tenofovir disoproxil fumarate (TDF), with improved renal and bone safety, in Chinese participants with chronic hepatitis B enrolled in two Phase 3 trials. This study aimed to evaluate the long-term virologic efficacy, serological and biochemical responses, resistance, and renal and bone safety of TAF over eight years in this population.

METHODS

Participants completing the three-year double-blind phase were eligible to receive open-label TAF 25 mg/day for up to an additional five years (totaling eight years). Analyses of viral suppression (HBV DNA < 29 IU/mL), alanine aminotransferase normalization, serological responses, resistance surveillance, and safety outcomes were conducted.

RESULTS

Among 334 enrolled participants, 212 of 227 participants randomized to TAF continued open-label TAF (TAF-TAF), and 99 of 107 participants on TDF switched to open-label TAF (TDF-TAF). At Year 8, 79.3% (180/227) and 78.5% (84/107) of participants in the TAF-TAF and TDF-TAF groups, respectively, achieved viral suppression (missing = failure); rates increased to 95.2% (180/189) and 95.5% (84/88) when excluding missing data. Alanine aminotransferase normalization rates remained high and comparable between groups. Serologic response rates continued to increase over time, with higher rates observed in the TAF-TAF group. Estimated glomerular filtration rate (by Cockcroft-Gault) and hip/spine bone mineral density remained stable in the TAF-TAF group through eight years; the small declines in these renal and bone parameters observed during double-blind TDF treatment improved after switching to open-label TAF. No resistance to TAF was detected.

CONCLUSIONS

Long-term TAF treatment demonstrated durable virologic efficacy, sustained biochemical and serological responses, and favorable renal and bone safety over eight years in Chinese participants with chronic hepatitis B.