[9] Two transcript variants encoding two different isoforms have been found for this gene.

[citation needed] The protein encoded by this gene hydrolyzes inosine triphosphate and deoxyinosine triphosphate to the monophosphate nucleotide and diphosphate.

Defects in the encoded protein can result in inosine triphosphate pyrophosphorylase deficiency.

[6] The enzyme ITPase dephosphorylates ribavirin triphosphate in vitro to ribavirin monophosphate, and reduced ITPase activity in 30% of humans potentiates mutagenesis in hepatitis C virus.

[10] Gene variants predicting reduced predicted ITPase activity have been associated with decreased risk of ribavirin-induced anemia, increased risk of thrombocytopenia, lower ribavirin concentrations, as well as a ribavirin-like reduced relapse risk following interferon-based therapy for hepatitis C virus (HCV) genotype 2 or 3 infection.