Switching to besifovir in patients with chronic hepatitis B receiving tenofovir disoproxil fumarate: A randomized trial

Background/Aims: Besifovir (BSV) showed comparable antiviral activity and superior safety profiles to tenofovir disoproxil fumarate (TDF) in treatment-naïve chronic hepatitis B (CHB). However, no data are available regarding the antiviral efficacy and safety of BSV in patients with CHB who switched from long-term TDF to BSV. This study aimed to evaluate the outcome of a 48-week BSV therapy in patients with CHB who switched from long-term TDF treatment. Methods: In this non-inferiority trial, 153 CHB patients treated with TDF for ≥48 weeks who had hepatitis B virus (HBV) DNA <20 IU/mL were randomized to receive either BSV 150 mg or TDF 300 mg for 48 weeks. Results: The per-protocol analysis included 130 patients (BSV group, 64; TDF group, 66). The median duration of TDF use before enrollment was 4.14 years. After 48 weeks, 100.0% and 98.5% patients in the BSV and TDF groups, respectively, met the primary endpoint (HBV DNA <20 IU/mL), demonstrating the non-inferior antiviral efficacy of BSV to TDF (95% confidence interval –0.01 to 0.04; P>0.999), with a predefined margin of –0.18. The mean percentage changes in estimated glomerular filtration rates were slightly better in the BSV group (1.67±11.73%) than in the TDF group (–1.24±11.02%). The BSV group showed a significant improvement in bone turnover biomarkers compared to the TDF group; accordingly, hip and spine bone mineral density increased in the BSV group. Conclusions: In patients with CHB receiving long-term TDF, switching to BSV may improve renal and bone safety with non-inferior antiviral efficacy compared to that of maintaining TDF. (Clin Mol Hepatol 2025;31:810-822).