Tenofovir in Asian Chronic Hepatitis B Patients
Condition: Chronic Hepatitis B
MeSH terms: Hepatitis A; Hepatitis B; Hepatitis B, Chronic; Hepatitis; Hepatitis, Chronic
Study type: Interventional

Summary: 
      Tenofovir (TDF) has been demonstrated to have potency antiviral against the hepatitis B virus
      (HBV) in various multiple-centre trials, with no cases of resistance encountered. However,
      its efficacy and resistance profile in the Asian population, which constitute the majority of
      chronic hepatitis B (CHB) patients, is unknown. Compared to other nucleoside analogues, TDF
      has been associated with relatively high rates of hepatitis B surface antigen (HBsAg)
      seroclearance. It would be interested to see if this could be reproduced. The investigators
      plan to report the serologic and virologic results of our 140 nucleoside analogue-experienced
      patients who were commenced on TDF.
    

Detailed description: 
      Recent multi-center trials have shown tenofovir disoprovil fumarate (TDF) demonstrating
      potent antiviral efficacy in both nucleoside-naive and -experienced chronic hepatitis B (CHB)
      patients. At present, there has been no identifiable amino acid substitutions associated with
      resistance to TDF.

      Since TDF and adefovir (ADV), another licensed drug for CHB, belong to same molecular group,
      acyclic phosphonate, there had been various studies investigating the efficacy of TDF in
      ADV-resistant patients. The efficacy of tenofovir in this group of patients is conflicting.
      While several studies have shown TDF achieving similar viral suppression when compared to CHB
      patients without ADV-resistance , another study found that patients with the signature ADV
      mutations of rtA181V/T and /or rtN236T responded suboptimally to TDF. For all published
      studies, the number of patients with documented genotypic resistance to adefovir is actually
      small (n = 17-40), and therefore, further studies in this area are required.

      Another interesting point to note was the relatively high rate of hepatitis B surface antigen
      (HBsAg) seroclearance found in patients taking TDF. The cumulative rate of HBsAg
      seroclearance up in hepatitis B e antigen (HBeAg)-positive was 10% after 4 years . However,
      the same study did not find any HBeAg-negative patients achieving HBsAg seroclearance. In
      addition, studies on TDF were mainly performed in Caucasian patients, the majority being
      genotypes A and D. A preliminary study performed in Asian patients, predominantly genotypes B
      and C, did not discover any cases of HBsAg seroclearance . Given the majority of the CHB
      population is found in Asia, further studies are needed to clarify if HBsAg seroclearance by
      nucleoside / nucleotide analogues is potentially achievable using TDF.
    

Intervention name(s): Tenofovir disoproxil
Intervention type(s): Drug
Intervention description(s): Tenofovir disoproxil 300mg daily
Other intervention name(s): Viread
Intervention MeSH terms: Tenofovir
Intervention model: Single Group Assignment
Masking: None (Open Label)
Primary purpose: Treatment
Keywords: HBV; Tenofovir; HBV DNA; HBsAg; Resistance