Wikipedia
Tipiracil
Tipiracil is a drug used in the treatment of cancer. In Japan, it is approved for use in combination with trifluridine (as the drug TAS-102 or Lonsurf) for the treatment of unresectable advanced or recurrent colorectal cancer.
Tipiracil helps maintain the blood concentration of trifluridine by inhibiting the enzyme thymidine phosphorylase which metabolizes trifluridine.