<p>Telbivudine is a synthetic thymidine nucleoside analogue with activity against hepatitis B virus (HBV). Telbivudine is the unmodified &beta;&ndash;L enantiomer of the naturally occurring nucleoside, thymidine. It undergoes phosphorylation via interaction with cellular kinases to form the active metabolite, telbivudine 5&#39;-triphosphate.<br />
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Telbivudine 5&#39;&ndash;triphosphate inhibits HBV DNA polymerase (reverse transcriptase) by competing with the natural substrate, thymidine 5&#39;&ndash;triphosphate. This leads to the chain termination of DNA synthesis, thereby inhibiting viral replication. Incorporation of telbivudine 5&#39;&ndash;triphosphate into viral DNA also causes DNA chain termination, resulting in inhibition of HBV replication. Telbivudine inhibits anticompliment or second-strand DNA.</p>