Department of Internal Medicine, Konkuk University School of Medicine , Seoul , Korea.
Abstract Objective. Partial virologic response (PVR) in chronic hepatitis B (CHB) patients during antiviral therapy is associated with an increased risk of occurrence of viral resistance and treatment failure. The aim of this study was to evaluate the clinical and virological responses of partial responders to long-term entecavir (ETV) monotherapy. Material and method. In this open-labeled prospective study, 128 treatment-naïve CHB patients treated with 0.5 mg ETV once daily for more than 12 months were monitored at baseline and at 3-month intervals during treatment. Results. At baseline, the mean age of subjects was 47.0 ± 13.0 years, and the median duration of treatment was 27 months; 85 subjects (66.4%) were HBeAg-positive, and 47 patients (36.7%) had liver cirrhosis. Eighteen of 128 patients (14.0%) showed PVR to 48 weeks of ETV treatment, and 13 patients were followed up for over 24 months. Among them, 9 of 13 patients (69.2 %) achieved a complete virologic response (VR, HBV-DNA < 60 IU/mL) during prolonged ETV treatment. Four showed persistent PVR, but only one patient with poor compliance developed genetic resistance to ETV at month 27. The occurrence of PVR was independently associated with a high viral load, more than 7 log(10) IU/mL (p = 0.014). Conclusions. CHB patients with a high viral load, more than 7 log log(10) IU/mL, are related to the occurrence of PVR during ETV monotherapy. Long-term ETV monotherapy may be effective for suppressing serum HBV DNA levels in treatment- naïve CHB patients with a PVR to ETV.