Tipiracil (hydrochloride)

Tipiracil is an inhibitor of thymidine phosphorylase (IC₅₀ = 35 nM).¹ It is selective for thymidine phosphorylase over uridine phosphorylase (UPase), thymidine kinase (TK), orotate phosphoribosyltransferase (OPRTase), and dihydropyrimidine dehydrogenase (DPD; IC₅₀s = > 1,000 µM for all). Tipiracil also inhibits the severe acute respiratory coronavirus 2 (SARS-CoV-2) endoribonuclease nsp15 (IC₅₀ = 7.5 µM).² It reduces the levels of SARS-CoV-2 spike glycoprotein, also known as the surface glycoprotein, in SARS-CoV-2-infected A549 lung cancer cells when used at a concentration of 50 µM. Tipiracil (1 µM) prevents the metabolism of the DNA synthesis inhibitor trifluorothymidine (Item No. 21366) in human liver extracts.¹. It increases the plasma levels and potentiates the cytotoxicity of trifluorothymidine in an AZ-521 gastric carcinoma mouse xenograft model when administered at an equimolar dose. Formulations containing tipiracil have been used in the treatment of metastatic colorectal and gastric cancers.

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1. Fukushima, M., Suzuki, N., Emura, T., et al. Structure and activity of specific inhibitors of thymidine phosphorylase to potentiate the function of antitumor 2'-deoxyribonucleosides. Biochem. Pharmacol. 59(10), 1227-1236 (2000).

2. Kim, Y., Wower, J., Maltseva, N.I., et al. Tipiracil binds to uridine site and inhibits Nsp15 endoribonuclease NendoU from SARS-CoV-2. Commun. Biol. 4(1), 193 (2021).