Clevudine is a synthetic pyrimidine nucleoside analog antiviral agent with activity against hepatitis B virus (HBV) and Epstein-Barr virus (EBV). Intracellularly, clevudine is phosphorylated to its active metabolites, clevudine monophosphate and triphosphate. The triphosphate metabolite competes with thymidine for incorporation into viral DNA, thereby causing DNA chain termination and inhibiting the function of HBV DNA polymerase and reverse transcriptase, consequently blocking the viral replication. It also blocks the DNA supply of the virus into the nucleus, reducing the amount of cccDNA by 20-100 times. Potentially useful for the treatment of the SARS-CoV-2 (COVID-19) infection, acting as a potent inhibitor of the RdRp protein.