Antiviral effect of entecavir in nucleos(t)ide analogue-naïve and nucleos(t)ide analogue-experienced chronic hepatitis B patients without virological response at week 24 or 48 of therapy.

We investigated the antiviral effect of entecavir in nucleos(t)ide analogue (NA)-naïve and NA-experienced chronic hepatitis B patients without virological response (VR, HBV DNA < 300 copies/mL) at week 24 or 48. A total of 369 NA-naïve and 181 NA-experienced patients treated with entecavir monotherapy were analysed. Of the 369 NA-naïve patients, 34 did not achieve VR at week 48. Of them, patients with HBV DNA ≤ 2000 copies/mL at week 48 achieved a higher VR rate than those with HBV DNA >2000 copies/mL (18/23 vs 3/11, P = 0.004). Two naïve patients with HBV DNA >2000 copies/mL developed entecavir- or lamivudine-resistant mutants. In 98 lamivudine-experienced patients without ever having lamivudine resistance, most patients with VR (72/72) and partial VR (300-10(4) copies/mL; 20/23) at week 24 or VR at week 48 (89/91) could maintain or achieve VR after prolonged therapy. In 75 patients with prior resistance to lamivudine, prolonged entecavir therapy led to low VR rate in those without VR at week 24 (13/45) or 48 (4/34) and high entecavir-resistance rate in those with or without VR at week 24 (6/30 with and 23/45 without) and 48 (8/41 with and 21/34 without). VR at week 48 was an independent predictor (HR 0.14, 95% CI 0.06-0.33) for entecavir-resistant mutant development among the 75 patients with prior lamivudine-resistant mutants. In conclusion, prolonged entecavir treatment resulted in a poor response in naïve patients with HBV DNA >2000 copies/mL at week 48 and patients with prior lamivudine-resistant mutants without VR at week 24 or 48.