title: Efficacy of tenofovir switch therapy for nucleos(t)ide-experienced patients with chronic hepatitis B.
abstract: BACKGROUND
  Tenofovir disoproxil fumarate has been used in chronic hepatitis B patients with suboptimal virologic response to nucleos(t)ide analogues. The efficacy of tenofovir switch therapy has not been well studied in Asian patients.
  
  
  OBJECTIVE
  To evaluate the efficacy of tenofovir switch therapy in nucleos(t)ide-experienced patients, and identify the factors associated with treatment response of tenofovir switch therapy.
  
  
  METHODS
  Nucleos(t)ide-experienced hepatitis B e antigen-positive and -negative patients prescribed with tenofovir were retrospectively identified and recruited for prospective analysis. Hepatitis B virus (HBV) DNA and other biochemical parameters were monitored in regular 3-6 monthly follow-up visits. Primary efficacy endpoint was maintained-virologic response with tenofovir switch therapy, defined as undetectable HBV DNA (<20 IU/mL) until the last follow-up visit.
  
  
  RESULTS
  An overall of 214/252 (84.9%) patients achieved maintained-virologic response after 22 (7-55) months of tenofovir switch therapy. On multivariate analysis, a lower HBV DNA level at the time of switching to tenofovir was an independent factor associated with treatment efficacy. Maintained-virologic response after switching to tenofovir was achieved in 177/190 (93.2%) patients with HBV DNA <20 000 IU/mL vs. 37/62 (59.7%) patients with HBV DNA ≥20 000 IU/mL (P < 0.001). Absence of genotypic resistance to lamivudine or adefovir dipivoxil was not associated with improved treatment outcome.
  
  
  CONCLUSIONS
  Tenofovir switch therapy is an effective treatment strategy in nucleos(t)ide-experienced chronic hepatitis B patients. However, in patients with HBV DNA ≥20 000 IU/mL at the time of switching to tenofovir, the chance of achieving maintained undetectable HBV DNA is significantly reduced.
authors.affiliation: Department of Medicine and Therapeutics, The Chinese University of Hong Kong, Hong Kong; Institute of Digestive Disease, The Chinese University of Hong Kong, Hong Kong; State Key Laboratory of Digestive Disease, The Chinese University of Hong Kong, Hong Kong.
authors.forename: A O-S
authors.initials: AO
authors.lastname: Lo
authors.forename: V W-S
authors.initials: VW
authors.lastname: Wong
authors.forename: G L-H
authors.initials: GL
authors.lastname: Wong
authors.forename: Y-K
authors.initials: YK
authors.lastname: Tse
authors.forename: H-Y
authors.initials: HY
authors.lastname: Chan
authors.forename: H L-Y
authors.initials: HL
authors.lastname: Chan
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives* / Q000494:pharmacology / Q000627:therapeutic use; D000328:Adult; D000998:Antiviral Agents / Q000627:therapeutic use*; D005260:Female; D006513:Hepatitis B e Antigens / Q000276:immunology*; D019694:Hepatitis B, Chronic / Q000188:drug therapy*; D006801:Humans; D019259:Lamivudine / Q000494:pharmacology; D008297:Male; D008875:Middle Aged; D063065:Organophosphonates / Q000494:pharmacology / Q000627:therapeutic use*; D011446:Prospective Studies; D000068698:Tenofovir; D016896:Treatment Outcome
chemical_list: D000998:Antiviral Agents; D006513:Hepatitis B e Antigens; D063065:Organophosphonates; D019259:Lamivudine; D000068698:Tenofovir; D000225:Adenine; C106812:adefovir dipivoxil