King's College London

Background and Aim: The incidence and consequences of flares during first-line nucleos(t)ide analogue therapy are largely unknown. We aimed to investigate the incidence and outcome of alanine aminotransferase (ALT) flares during long-term entecavir (ETV) in chronic hepatitis B (CHB). Methods: CHB patients treated with ETV monotherapy from 11 European centers were studied. Flare was defined as > 3× increase in ALT compared with baseline or lowest on-treatment level and an absolute ALT > 3× ULN. Flares were designated as host-induced (preceded by hepatitis B virus (HBV)-DNA decline), virus-induced (HBV-DNA increase), or indeterminate (stable HBV-DNA). Results: Seven hundred and twenty-nine patients were treated with ETV for median of 3.5 years. Thirty patients developed a flare with cumulative incidence of 6.3% at year 5. Baseline hepatitis B e antigen (HBeAg)-positivity (HR 2.84; P = 0.005) and high HBV-DNA (Hazard ratio (HR) 1.30; P = 0.003) predicted flares. There were 12 (40%) host-induced, 7 (23%) virus-induced, and 11 (37%) indeterminate flares. Host-induced flares occurred earlier than virus-induced (median: 15 vs 83 weeks; P = 0.027) or indeterminate flares (15 vs 109 weeks; P = 0.011). Host-induced flares were associated with biochemical remission, and HBeAg (n = 3) and hepatitis B surface antigen (n = 2) seroconversions were exclusively observed among patients with these flares. Virus-induced flares were associated with ETV resistance (n = 2) and non-compliance (n = 1). Conclusion: The incidence of ALT flares during ETV was low in this real-life cohort. ETV can be safely continued in patients with host-induced flares. Treatment adherence and drug resistance must be assessed in patients with virus-induced flares.