Tipiracil (TPI) is a potent and competitive inhibitor of thymidine phosphorylase (TPase) with an IC
50 value of 35 nM for human placental TPase.
1 It is selective for TPase over other pyrimidine-metabolizing enzymes (IC
50s = >1 mM for UPase, OPRTase, TK, and DPDase). TPI inhibits the phosphorolysis and degradation of trifluorothymidine (Item No.
21366), a cytotoxic nucleoside, in human breast and colon carcinoma tumor samples. Oral administration of TPI (12.5-50 mg/kg) enhances the anti-tumor activity of trifluorothymidine in a mouse AZ-521 stomach cancer xenograft model. Formulations containing TPI have been used for the treatment of metastatic colorectal cancer.
2