Trifluridine/tipiracil hydrochloride mixture (TAS-102) is a potent and orally active nucleoside antitumor agent. The composition of Trifluridine/tipiracil hydrochloride mixture (TAS-102) is a 1:0.5 mixture (on a molar basis) of alpha,alpha,alpha-tri-fluorothymidine (FTD) and thymidine phosphorylase inhibitor (TPI). Trifluridine/tipiracil hydrochloride mixture (TAS-102) shows the antitumor activity mainly via the inhibition of thymidylate synthase (TS) and incorporation into DNA[1][2].