Treatment of chronic hepatitis B patients with tyrosine-methionine-aspartate-aspartate mutations.

Lamivudine is an antiviral used for the treatment of chronic hepatitis B. Several studies have reported various mutations that are induced by lamivudine therapy. These mutations in the tyrosine-methionine-aspartate-aspartate (YMDD) motif are necessary and sufficient to confer high-level lamivudine resistance. During treatment with lamivudine, mutations develop in the YMDD motif of the hepatitis B virus (HBV) polymerase gene and lamivudine cannot prevent the replication of the mutant form. The virulence strain of developed mutation in the polymerase gene is lower than the original virus and they are susceptible to treatment with some other nucleoside analogs except lamivudine. Entecavir and tenofovir are potent HBV inhibitors and they can be confidently used as first line monotherapies. We read the article written by Tan et al that lamivudine therapy improved the clinical course in HBV patients with natural YMDD mutations. We think that lamivudine use for this patient group is not appropriate. These patients should use YMDD mutant form-effective drugs such as adefovir, tenofovir.