Antiviral Activity of the Acyclic Nucleoside Phosphonate Prodrug LAVR-289 against Poxviruses and African Swine Fever Virus

Poxviruses are double-stranded DNA viruses including relevant zoonotic pathogens with high morbidity and potential biological warfare threats. Although African swine fever virus belongs to the Asfarviridae family and is not strictly classified as a Poxviridae member, both fall within the same class of Pokkesviricetes that replicate in the cytoplasm. Among compounds targeting these viruses, acyclic nucleoside phosphonate (ANP) prodrugs are promising inhibitors of viral DNA polymerases. However, some limitations related to their toxicity and the rapid emergence of resistance highlight the need for new antiviral molecules. In this study, we tested a new ANP called LAVR-289. This product effectively inhibits viral replication by targeting a specific domain in the poxvirus DNA polymerase. Using monkeypox virus models, the subcutaneous or oral administration of LAVR-289 demonstrated protective efficacy in infected animals without toxicity. Its in vivo half-life, long on-the-shelf stability and broad-spectrum efficacy make LAVR-289 a promising candidate for further development and stockpiling as a medical countermeasure against dsDNA virus outbreaks. LAVR-289 can be positioned in the context of recurrent viral epidemics, bioterrorism risk, and the emergence of resistant strains in the population.