It a thymidine nucleoside analog (Figure 3) that was approved in Korea for the treatment of hepatitis B virus (HBV) infection [60]. Similar to previous agents, it is a prodrug that requires phosphorylation to form the corresponding active nucleotide, the triphosphate. Mechanistically, the triphosphate active form appears to noncompetitively inhibit the HBV reverse transcriptase protein priming and DNA synthesis [61]. Importantly, although clevudine showed a potent antiviral response, its long-term use for more than a year led to the development of viral resistance and myopathy [60]. The drug is being evaluated in a phase 2 as a treatment for COVID-19 in Korea (NCT04347915; n = 60).