Comparison of the impact of tenofovir alafenamide and entecavir on declines of hepatitis B surface antigen levels

Objective: Tenofovir alafenamide is a new prodrug of tenofovir that allows for the treatment of patients with hepatitis B virus (HBV) at a lower dose than with tenofovir disoproxil fumarate, due to the more efficient delivery of tenofovir to hepatocytes. In this study, we compared entecavir and tenofovir alafenamide in terms of their ability to reduce hepatitis B surface antigen (HBsAg) in the same group of patients with HBV infection. Methods: During March and June 2018, 129 patients who received entecavir were switched to tenofovir alafenamide. Every 3– 6 months for 1 year before and after switching to tenofovir alafenamide, all patients underwent measurements of HBsAg, hepatitis core-related antigen (HBcrAg), calcium (Ca), inorganic phosphorus, and estimated glomerular filtration rate (eGFR). Results: The percent decline rate during the entecavir and tenofovir alafenamide phases at 6 months were 2.38% (−3.57 to 0.00) and −3.57% (−7.14 to 0.00), respectively, and those at 12 months were 3.03% (−6.57 to 0.00) and −5.56% (−7.41 to −2.50), respectively. HBsAg levels were reduced significantly more during the tenofovir alafenamide phase than during the entecavir phase ( P < 0.0001). There were no significant differences in the percent declines of HBcrAg, Ca, inorganic phosphorus, or eGFR during the entecavir and tenofovir alafenamide phases after 1 year. Conclusion: tenofovir alafenamide significantly decreased HBsAg levels compared to entecavir.