Antiviral Activity of Various 1-(2′-Deoxy-β-d-lyxofuranosyl), 1-(2′-Fluoro-β-d-xylofuranosyl), 1-(3′-Fluoro-β-d-arabinofuranosyl), and 2′-Fluoro-2′,3′-didehydro-2′,3′-dideoxyribose Pyrimidine Nucleoside Analogues against Duck Hepatitis B Virus (DHBV) and Human Hepatitis B Virus (HBV) Replication

Despite the existence of successful vaccine and antiviral therapies, infection with hepatitis B virus (HBV) continues to be a major global cause of acute and chronic liver disease and high mortality. We synthesized and evaluated several lyxofuranosyl, 2′-fluoroxylofuranosyl, 3′-fluoroarabinofuranosyl, and 2′-fluoro-2′,3′-didehydro-2′,3′-dideoxyribose pyrimidine nucleoside analogues for antiviral activities against hepatitis B virus. Among the compounds examined, 1-(2-deoxy-β-d-lyxofuranosyl)thymine (<b>23</b>), 1-(2-deoxy-β-d-lyxofuranosyl)-5-trifluoromethyluracil (<b>25</b>), 1-(2-deoxy-2-fluoro-β-d-xylofuranosyl)uracil (<b>38</b>), 1-(2-deoxy-2-fluoro-β-d-xylofuranosyl)thymine (<b>39</b>), 2′,3′-dideoxy-2′,3′-didehydro-2′-fluorothymidine (<b>48</b>), and 2′,3′-dideoxy-2′,3′-didehydro-2′-fluoro-5-ethyluridine (<b>49</b>) were found to possess significant anti-HBV activity against DHBV in primary duck hepatocytes with EC₅₀ values of 4.1, 3.3, 40.6, 3.8, 0.2, and 39.0 μM, respectively. Compounds <b>23</b>, <b>25</b>, <b>39</b>, <b>48</b>, and <b>49</b> (EC₅₀ = 41.3, 33.7, 19.2, 2.0−4.1, and 39.0 μM, respectively) exhibited significant activity against wild-type human HBV in 2.2.15 cells. Intriguingly, <b>25</b>, <b>39</b>, <b>48</b>, and <b>49</b> retained sensitivity against lamivudine-resistant HBV containing a single mutation (M204I) and <b>48</b> emerged as an effective inhibitor of drug-resistant HBV with an EC₅₀ of 4.1 μM. In contrast, 50% inhibition could not be achieved by lamivudine at 44 μM concentration in the drug-resistant strain. The compounds investigated did not show cytotoxicity to host cells up to the highest concentrations tested.