Hepatitis B Subtype Increases resistance

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Hepatitis B Subtype Increases Risk of Epivir HBV Resistance



By Brian Boyle, MD



Hepatitis B virus has four subtypes of surface antigen, namely adw, ayw, adr and ayr. Epivir HBV (lamivudine) is an effective therapy for chronic Hepatitis B, but there is no information regarding whether the specific subtype has an affect on this antiviral therapy. A study to determine the effect of subtype on Epivir HBV resistance was undertaken in Hamburg, Germany.



HBV genotyping was performed on a study population of 26 patients who had chronic HBV and who were Epivir HBV-naïve. Genotyping revealed 13 patients with adw subtype and 13 patients with ayw subtype. All patients were hepatitis C negative, and there were no significant differences in age, sex, previous treatment with interferon alpha and HBV viral load between the two groups. Each patient received Epivir HBV 100mg daily for an average period of 12 months in the adw subgroup (range 7-31) and 11 months in the ayw subgroup (range 3-25). Adherence was monitored by pill counts and HBV DNA was quantified in blood samples every 3 months. A positive sample was sequenced for resistance mutations with an assay detection limit of 10%.



Epivir HBV resistance occurred in 7 patients of the adw subtype and 1 with subtype ayw in a median of 12 months of therapy (range 9-24 months). The authors conclude that ayw subtype carriers have a reduced risk of developing Epivir HBV resistance. Furthermore, adw carriers may need to be considered for a modified treatment regimen (possibly a combination of Epivir HBV with other antivirals). Finally, the authors conclude "HBV subtype of the patient should be included as a variable in further therapeutic studies for chronic hepatitis B."