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Antiviral efficacy of adefovir dipivoxil similar regardless of hepatitis B genotype
  NEW YORK (Reuters Health) - The oral prodrug of adefovir, adefovir dipivoxil, led to significant reductions in serum HBV-DNA levels, regardless of HBV genotype, HBeAg status, or race, according to a study published in the July issue of Gastroenterology.
Recent reports suggesting that viral heterogeneity may influence response to antiviral therapy led researchers to analyze the frequency and distribution of HBV genotypes of participating patients as well as their response to treatment. Dr. Chris Westland of Gilead Sciences in Foster City, California, and colleagues looked at baseline data from 694 patients with hepatitis B virus (HBV) enrolled in two large phase III trials of 10 mg adefovir dipivoxil for 48 weeks.
The data "confirm and extend previous reports on the asymmetric distribution of HBV genotypes with respect to geography, race, and HBeAg status," the authors write.
In agreement with other reports, genotypes A, B, C, and D were most commonly seen in patients from European, Mediterranean, and Asia/Oceanic countries. The low frequency of types E and F in study subjects may reflect the scarcity of patients from Africa and South America, the authors suggest.
Eleven patients (1.6%) were infected with HBV genotype G, which, the team notes, has only recently been discovered and its worldwide prevalence unknown. Genotype G was found in patients from North America, confirming prior reports, but also in several new locations within the United States, (California, Michigan, Florida, New York, and Washington), one new location in Europe (United Kingdom), and for the first time in a Mediterranean country (Italy).
Regardless of study site, 93% of Asian patients were infected with genotypes B or C, while 93% of Caucasian patients were infected with genotypes A and D.
Analysis of baseline levels of serum HBV DNA by genotype yielded a number of "interesting" findings, according to the team. For example, in HbeAg-positive patients, genotype G was significantly associated with higher levels of serum HBV DNA levels than the other genotypes. Moreover, all 11 patients with genotype G had HBeAg+ chronic hepatitis.
In HBeAg-negative chronic hepatitis B patients, on the other hand, genotype D was associated with significantly higher serum HBV-DNA levels.
Gastroenterology 2003;125:107-116.
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