Advances in Nucleotide Antiviral Development from Scientific Discovery to Clinical Applications: Tenofovir Disoproxil Fumarate for Hepatitis B

Exploration of naturally occurring chemical structures for medicinal uses has received significant interest in drug discovery and development research in the past few decades. None have had more success or products of greater clinical efficacy than synthetic analogs of nucleosides and nucleotides, especially as antiviral drugs. Nucleos(t)ide antivirals are synthetic analogs of the natural building blocks of DNA or RNA. This review focuses on the developmental path of tenofovir disoproxil fumarate (TDF), a prodrug of a nucleotide analog and its clinical applications as a first-line antiviral for chronic hepatitis B (CHB). Tenofovir is a potent antiviral compound, but has poor oral availability. The disoproxil fumarate (DF) prodrug moiety greatly enhances intestinal absorption allowing it to become an oral medication. Tenofovir is activated intracellularly, and the incorporation into HBV DNA prevents further elongation thus terminating replication. In patients with CHB, TDF has demonstrated broad, potent and sustained virologic response. Maintenance of viral suppression for up to 5 years resulted in regression of fibrosis and cirrhosis. No tenofovir-resistant HBV variants have been detected in patients after long-term use. The efficacy and safety profiles reported from cohort studies of clinical practices were consistent with those observed in registration trials. Continuous development includes a new oral prodrug, tenofovir alafenamide fumarate (TAF), which has enhanced delivery of tenofovir to target cells compared to TDF.