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.