Methods. We provided 100 consecutive CHB patients in 2 academic hospitals with a medication dispenser that monitors ETV intake in real time (Sensemedic, Evalan, Amsterdam, the Netherlands). During 16 weeks of treatment, adherence data were directly transferred to a central server. Poor adherence was Lumacaftor mouse defined as <80% pill intake during the study period. At both baseline and 16-week follow-up visits, quantitative serum HBV DNA (Cobas Taqman, Roche, Almere, the Netherlands: lower limit of detection 20 IU/mL) was performed. Results. At start of the study, 64% of patients were HBe-negative, 67% were treated > 1 year with ETV and 76% were HBV DNA unde-tectable.

29% was (PEG-)interferon-experienced, and 27% NUC-experienced. Adherence over 16 weeks averaged 85±17%. Percentages of patients with ≧70%, ≧80%, ≧90% and ≧95% adherence were 81 %, 70%, 52% and 43%, respectively. The longest interruption between two consecutive ETV doses was a median of 3 days (range 1-53). Patients with poor adherence were significantly younger (40 vs. 47 years, p=0.01), Proteasome inhibition assay while no other predictors of poor adherence were identified. 82 patients had HBV DNA <20 IU/mL after 16 weeks, whereas in 18 patients HBV DNA levels >20 IU/mL were measured. No virological breakthrough

occurred. Patients with HBV DNA >20 IU/mL were younger (37 vs. 47 years, p=0.001), more frequently treated <1 year (75% vs. 28%, p<0.001), more frequently HBeAg positive (72% vs. 28%, p=0.002), NUC-naive (89 vs. 69%, p=0.11), and had lower mean adherence (83% vs. 91% (p=0.19). In multivariate analysis, duration of ETV treatment (adjusted OR 18.8 (4.1-87.0, p<0.001) and negative HBe-status (adjusted OR 11.9 (2.6-53.6), p=0.001) predicted HBV DNA negativity, whereas adherence was not a significant predictor (adjusted OR 1.02 (0.98-1.07), p=0.34). Adherence tended to be lower in the 7 patients with HBV DNA >200 IU/mL compared to the 1 1 patients with HBV DNA 20-200 IU/mL (71 vs. 95%, p=0.1 0). Conclusions: Overall 70% of our CHB patients exhibited HSP90 good adherence to ETV therapy,

with younger patients being more prone to poor adherence. Even in case of poor adherence, virological responses seem to be generally excellent and poor adherence was not an independent predictor of virological response. Disclosures: Joop Arends – Advisory Committees or Review Panels: MSD, BMS Harry L. Janssen – Consulting: Abbott, Bristol Myers Squibb, Debio, Gilead Sciences, Merck, Medtronic, Novartis, Roche, Santaris; Grant/Research Support: Anadys, Bristol Myers Squibb, Gilead Sciences, Innogenetics, Kirin, Merck, Medtronic, Novartis, Roche, Santaris Karel J. van Erpecum – Grant/Research Support: Bristol Meyers Squibb, MSD The following people have nothing to disclose: Lotte G. van Vlerken, Pauline Arends, Faydra I. Lieveld, Willem Pieter Brouwer, Peter D.