Monotherapy with tenofovir disoproxil fumarate for adefovir-resistant vs. entecavir-resistant chronic hepatitis B: A 5-year clinical trial

Abstract

Background & Aims Tenofovir disoproxil fumarate (TDF) monotherapy has displayed non-inferior efficacy to TDF plus entecavir (ETV) combination therapy in patients with hepatitis B virus (HBV) resistant to ETV and/or adefovir (ADV). Nonetheless, the virologic response rate was suboptimal in patients receiving up to 144 weeks of TDF monotherapy. We aimed to assess the efficacy and safety of TDF monotherapy given for up to 240 weeks.

Methods One trial enrolled patients with ETV resistance without ADV resistance (n = 90), and another trial included patients with ADV resistance (n = 102). Most patients (91.2%) also had lamivudine resistance. Patients were randomized 1:1 to receive TDF monotherapy or TDF + ETV combination therapy for 48 weeks, and then TDF monotherapy until week 240. We compared efficacy between the studies and safety in the pooled population at 240 weeks.

Results At week 240, the proportion of patients with serum HBV DNA <15 IU/ml was not significantly different between the ETV and ADV resistance groups in the full analysis set (84.4% vs. 73.5%; p = 0.07), which was significantly different by on-treatment analysis (92.7% vs. 79.8%; p = 0.02). Virologic blips associated with poor medication adherence occurred in 7 patients throughout the 240 weeks. None developed additional HBV resistance mutations. Among the 170 HBV e antigen (HBeAg)-positive patients at baseline, 12 (7.1%) achieved HBeAg seroconversion at week 240. None achieved HBV surface antigen seroclearance. Significant decreases from baseline were observed at week 240 in the estimated glomerular filtration rate (−3.21 ml/min/1.73 m2 by the CKD-EPI equation, p <0.001) and bone mineral density (g/cm2) at the femur (−2.48%, p <0.001).

Conclusions Up to 240 weeks of TDF monotherapy provided an increasing virologic response rate in heavily pretreated patients with HBV resistant to ETV and/or ADV. However, it was associated with poor serological responses and decreasing renal function and bone mineral density.