Galidesivir triphosphate is a substrate for viral RNA-dependent RNA polymerase (RDRP), resulting in termination of viral RNA replication and thus serves as an antiviral. Galidesivir triphosphate inhibits HCV NS5B RNA polymerase activity and protects mice against Ebola. Galidesivir triphosphate (Immucillin-A triphosphate) is converted by the prodrug Galidesivir.

Galidesivir is converted to the mono-, di-, and triphosphates in virus-infected human Huh-7 cells.?Galidesivir triphosphate (Immucillin-A triphosphate) (1-60 μM) inhibits hepatitis C virus (HCV) RNA polymerase transcriptional activity in a cell-free, isolated enzyme transcription assay.The triphosphate is a substrate for viral RNA-dependent RNA polymerase.?Its incorporation permits the addition of a few additional encoded bases at which point the Galidesivir-modified RNA cannot be elongated.In virus-infected cells, Galidesivir is converted to the triphosphate, is incorporated into the viral transcript, and functions as an atypical chain-terminator for RNA-dependent RNA polymerases.

In vivo conversion of Galidesivir to its TP (Galidesivir triphosphate) nucleotide is particularly efficient.