Antihepatitis B therapy: a review of current medications and novel small molecule inhibitors

There are approximately 350 million hepatitis B virus (HBV) carriers worldwide. Chronic HBV infection increases the risk of liver cirrhosis and hepatocellular carcinoma. To date, two classes of antiviral drugs have been approved by the Food and Drug Administration for the treatment of hepatitis B, immunomodulators (interferon IFN]‐α and pegylated‐interferon PEG‐IFN]‐α) and nucleos(t)ide analogs (lamivudine, telbivudine, adefovir, tenofovir TDF], and entecavir ETV]). Of these, ETV, TDF, and PEG‐IFN‐α are the most effective and are currently recommended for anti‐HBV therapy. However, these therapies are less than optimal because of their low rate of viral DNA and surface antigen clearance; thus, there exists a significant unmet medical need for safe and efficacious new anti‐HBV drugs. Covering diverse chemical structures and mechanisms of action, non‐nucleos(t)ide compounds offer great promise in the search for new anti‐HBV drugs. This review summarizes the currently approved anti‐HBV drugs and highlights advances in the identification and characterization of novel small molecule HBV inhibitors. We discuss the sources, structures, anti‐HBV effects, mechanisms of action, and potential toxicities of these novel inhibitors.