TAS-102

TAS-102 is an oral combination drug consisting of trifluridine (FTD), which is a thymidine-based nucleoside analog, and tipiracil hydrochloride (TPI), which improves the bioavailability of FTD by inhibiting its catabolism by thymidine phosphorylase (TP)^[1].

Phosphorylated form of trifluridine is incorporated into DNA resulting in DNA dysfunction and cell cycle arrest. Thymidine phosphorylase inhibitor inhibits degradation of FTD and inhibits angiogenesis. Thus, TAS-102 treatment results in massive trifluridine incorporation into DNA and in activation of similar DNA damage response pathways, which involve phosphorylation of Chk1 and cycle arrest during the G2/M-phase^[2].

Cells were treated with different concentrations of TAS-120.

The elimination half-life of FTD after intravenous administration to humans is very rapid (18 minutes), due to the rapid degradation of FTD to its major metabolite, 5-trifluoromethyl-2,4(1H,3H)-pyrimidinedione. In monkeys, the plasma FTD level after oral administration alone is very low, suggesting extensive first-pass metabolism by the liver and intestine TPase. However, the addition of TPI(tipiracil hydrochloride) is found to enable oral administration. By inhibiting TP, TPI inhibits the degradation of FTD in the liver and intestines following oral administration and thereby improves its bioavailability. The TP enzyme catalyzes the phosphorolysis of pyrimidine 2'-deoxynucleosides such as FTD. Studies using human CRC tumor xenografts in mice determine that the maximum antitumor activity is achieved with a 1:0.5 molar ratio, and studies in mice and monkeys show that the maximum plasma concentration of FTD is almost achieved with the same ratio. Moreover, this ratio produces a favorable balance between antitumor activity and toxicity. Lower toxicity in mice is observed with TPI coadministration than with FTD alone. TAS-102 (FTD) can overcome acquired resistance to 5-FU because the main mechanism of TAS-102 is not associated with main metabolic enzymes of 5-FU, such as TS and OPRT. TAS-102 has demonstrated efficacy in 5-FU-refractory cancers^[1].