Monitoring trifluridine incorporation in the peripheral blood mononuclear cells of colorectal cancer patients under trifluridine/tipiracil medication.

Trifluridine/tipiracil (TFTD, TAS-102) is an orally administrated anti-cancer drug with efficacy validated for patients with metastatic colorectal cancer (mCRC). Trifluridine (FTD) is an active cytotoxic component of TFTD and mediates the anticancer effect via its incorporation into DNA. However, it has not been examined whether FTD is incorporated into the tissues of patients who received TFTD medication. By detecting FTD incorporation into DNA by a specific antibody, we successfully detected FTD in the bone marrow and spleen cells isolated from FTD-challenged mice as well as human peripheral blood mononuclear cells (PBMCs) activated with phytohemagglutinin-P and exposed to FTD in vitro. FTD was also detected in PBMCs isolated from mCRC patients who had administrated TFTD medication. Intriguingly, weekly evaluation of PBMCs from mCRC patients revealed the percentage of FTD-positive PBMCs increased and decreased in parallel with the administration and cessation of TFTD medication, respectively. To our knowledge, this is the first report to detect an active cytotoxic component of a chemotherapeutic drug in clinical specimens using a specific antibody. This technique may enable us to predict the clinical benefits or the adverse effects of TFTD in mCRC patients.

Phase 1 study of cardiac safety of TAS-102 in patients with advanced solid tumors.

PURPOSE: TAS-102 is a novel oral agent combining the antineoplastic thymidine-based nucleoside analogue, trifluridine, and the thymidine phosphorylase inhibitor, tipiracil (molar ratio 1:0.5). TAS-102 has shown good activity in refractory metastatic colorectal cancer with acceptable safety. No QT prolongation was seen in clinical studies. This study aimed to investigate TAS-102 cardiac safety for regulatory requirements. METHODS: This was a phase 1, non-randomized study in adults with advanced solid tumors. Intensive QT assessments were conducted at baseline, placebo, and following single and multiple doses of TAS-102 during a 28-day cycle. RESULTS: Following single- and multiple-dose administration (N = 30), the upper bounds of the one-sided 95 % confidence intervals for the difference between TAS-102 and placebo in time-matched baseline-subtracted 12-lead Holter QT intervals did not exceed 20 ms at any prespecified time point. One patient had a change from baseline in QTcI interval ≥60 ms, and one patient had a QTcI interval >500 ms following multiple-dose TAS-102 administration. No patient had an uncorrected QT, QTcF, or QTcB interval >500 ms. Based on the exposure-response analysis between TAS-102 plasma concentrations and the placebo-adjusted QTc intervals, none of the upper bounds of the one-sided 95 % prediction intervals exceeded 20 ms. There were no significant morphological changes for T or U waves. No cardiovascular AEs were reported in cycle 1. Across all cycles, no patient experienced an AE of ventricular tachycardia, ventricular fibrillation, syncope, or seizure. CONCLUSIONS: There was no clinically relevant relationship between TAS-102 plasma concentrations and QTc interval; TAS-102 had no clinically relevant effects on cardiac repolarization. CLINICAL TRIALS: ClinicalTrials.gov study number: NCT01867879.

Involvement of concentrative nucleoside transporter 1 in intestinal absorption of trifluorothymidine, a novel antitumor nucleoside, in rats.

ααα-Trifluorothymidine (TFT), an anticancer nucleoside analog, is a potent thymidylate synthase inhibitor. TFT exerts its antitumor activity primarily by inducing DNA fragmentation after incorporation of the triphosphate form of TFT into the DNA. Although an oral combination of TFT and a thymidine phosphorylase inhibitor has been clinically developed, there is little information regarding TFT absorption. Therefore, we investigated TFT absorption in the rat small intestine. After oral administration of TFT in rats, more than 75% of the TFT was absorbed. To identify the uptake transport system, uptake studies were conducted by using everted sacs prepared from rat small intestines. TFT uptake was saturable, significantly reduced under Na(+)-free conditions, and strongly inhibited by the addition of an endogenous pyrimidine nucleoside. From these results, we suggested the involvement of concentrative nucleoside transporters (CNTs) in TFT absorption into rat small intestine. In rat small intestines, the mRNAs coding for rat CNT1 (rCNT1) and rCNT2, but not for rCNT3, were predominantly expressed. To investigate the roles of rCNT1 and rCNT2 in TFT uptake, we conducted uptake assays by using Xenopus laevis oocytes injected with rCNT1 complementary RNA (cRNA) and rCNT2 cRNA. TFT uptake by X. laevis oocytes injected with rCNT1 cRNA, and not rCNT2 cRNA, was significantly greater than that by water-injected oocytes. In addition, in situ single-pass perfusion experiments performed using rat jejunum regions showed that thymidine, a substrate for CNT1, strongly inhibited TFT uptake. In conclusion, TFT is absorbed via rCNT1 in the intestinal lumen in rats.

Phase I study to determine the safety and pharmacokinetics of oral administration of TAS-102 in patients with solid tumors.

BACKGROUND: The purpose of the current study was to determine the maximum tolerated dose, dose-limiting toxicities, pharmacokinetic profile, and recommended Phase II dose of oral administration of TAS-102, a novel nucleoside formed by the combination of alpha,alpha,alpha-trifluorothymidine (FTD) and a thymidine phosphorylase inhibitor (TPI: 5-chloro-6-(2-iminopyrrolidin-1-yl)methyl-2,4(1H,3H)-pyrimidinedione). METHODS: Eligible patients had advanced solid tumors, adequate organ function, and had not received anticancer therapy in the preceding 4 weeks. TAS-102 was administered orally once daily for 14 days, followed by a 1-week rest, repeated every 3 weeks. The initial dose of TAS-102 administered was 100 mg/m2/day. The first 2 patients treated at that dose experienced substantial toxicity and, therefore, lower dose levels of TAS-102 were subsequently explored. RESULTS: Fourteen patients were enrolled; all patients were evaluable for toxicity assessment and 12 were evaluable for response. The initial dose explored was 100 mg/m2/day, based on a preclinical monkey model. However, the first 2 patients experienced bone marrow suppression of Grade 3 or 4 in course 1. The protocol was amended to study the next cohort of patients at 50 mg/m2/day. At this dose level no Grade 3 or 4 toxicities were observed in course 1. In the subsequent dose level (60 mg/m2/day), 3 of 6 patients experienced Grade 3 or 4 granulocytopenia as dose-limiting toxicity. Three additional patients for a total of 6 were enrolled at 50 mg/m2/day without occurrence of dose-limiting toxicity. Thus, 50 mg/m2/day was declared the maximum tolerated dose for this schedule. CONCLUSIONS: The authors' study showed that 50 mg/m2/day was a tolerable dose of the novel antimetabolite FTD in combination with an inhibitor of its inactivating enzyme TP, and this is the recommended Phase II dose. Evaluation of this daily dose in malignancies for which fluoropyrimidines have failed is needed.

Potentiation of the antitumor activity of alpha, alpha, alpha-trifluorothymidine by the co-administration of an inhibitor of thymidine phosphorylase at a suitable molar ratio in vivo.

Trifluorothymidine (FTD) is a thymidine analog that exhibits an antitumor activity through its inhibition of thymidylate synthase and its incorporation into DNA. However, FTD is rapidly hydrolyzed to an inactive form by thymidine phosphorylase (TP). We attempted to augment the antitumor activity of FTD by combining it with a potent and reversible inhibitor of TP, 5-chloro-6-(2-imino-propyrrolidin-1-yl) methyl-2, 4 (1H, 3H)-pyrimidinedione hydrochloride (TPI) in human tumor xenografts with a low sensitivity to 5-fluorouracil. The optimum ratio of TPI to FTD was determined by measuring the maximum plasma level of FTD after oral administration and the antitumor effect of FTD on human tumor xenografts in mice. When > 0.5 M of TPI and 1 M of FTD (10 mg/kg) were co-administered, the plasma FTD levels in mice and monkeys were elevated, almost reaching a maximal and constant value of 20-30 microg/ml and 15 microg/ml, respectively. When human gastrointestinal cancer cell lines (DLD-1, CO-3 and AZ521) were xenografted into nude mice, the antitumor activity of FTD was augmented by the co-administration of TPI, compared to that of FTD alone, and the ED50 value, used to indicate the antitumor effect, reached a maximum value (about 25, 20, and 10 mg/kg in the DLD-1, CO-3, and AZ521 tumors, respectively) when > 0.5 M of TPI was combined with 1 M of FTD. The oral administration of TPI markedly improved the FTD-induced toxicity, as evaluated by the decrease in the body weight of the mice. These results suggested that the optimum ratio of FTD to TPI was 1:0.5 M, enabling a high antitumor activity and a low toxicity. We further evaluated whether TPI inhibits TP-induced angiogenesis in a gelatin-sponge mouse model, based on the finding that TP is identical to platelet-derived endothelial cell growth factor. Ten and 30 mg/kg administration of TPI significantly inhibited TP-induced neovascularization in a dose-dependent manner in a mouse model. The above results suggest that the combination of TPI and an antitumor nucleoside, FTD, not only enhances the antitumor efficacy and decreases the toxicity of FTD, but also suppresses TP-induced angiogenesis.

Structure and activity of specific inhibitors of thymidine phosphorylase to potentiate the function of antitumor 2'-deoxyribonucleosides.

A new class of 5-halogenated pyrimidine analogs substituted at the 6-position was evaluated as competitive inhibitors of thymidine phosphorylase (TPase). The most potent member of the series was 5-chloro-6-(2-iminopyrrolidin-1-yl)methyl-2,4(1H,3H)-pyrimidine dio ne hydrochloride (TPI), which has an apparent K(i) value of 1.7 x 10(-8) M. TPI selectively inhibited the activity of TPase, but not that of uridine phosphorylase, thymidine kinase, orotate phosphoribosyltransferase, or dihydropyrimidine dehydrogenase. In vitro inhibition studies of TPI using a thymidine analogue, 5-trifluoromethyl-2'-deoxyuridine (F(3)dThd), as the substrate demonstrated that F(3)dThd phosphorolytic activity was inhibited markedly by TPI (1 x 10(-6) M) in extracts from the liver, small intestine, and tumors of humans, from the liver and small intestine of cynomolgus monkeys, and from the liver of rodents, but not from the liver or small intestine of dogs or the small intestine of rodents, suggesting that the distribution of TPase differs between humans and animal species, and that TPI could contribute to the modulation of TPase in humans. When F(3)dThd or 5-iodo-2'-deoxyuridine (IdUrd) was coadministered to mice with TPI at a molar ratio of 1:1, the blood levels of F(3)dThd (or IdUrd) were about 2-fold higher than when F(3)dThd (or IdUrd) was administered alone. In monkeys, the maximum concentration (C(max)) and the area under the concentration-time curve (AUC) after oral F(3)dThd alone were 0.23 microg/mL and 0.28 microg. hr/mL, respectively, but markedly increased to 15.18 microg/mL (approximately 70-fold) and 28.47 microg. hr/mL (approximately 100-fold), respectively, when combined with equimolar TPI. Combined oral administration of TPI significantly potentiated the antitumor activity of F(3)dThd on AZ-521 human stomach cancer xenografts in nude mice. In conclusion, TPI may contribute not only to inhibition of TPase-mediated biological functions but also to potentiation of the biological activity of various 2'-deoxyuridine and thymidine derivatives by combining with them.

Detection of new metabolites of trifluridine (F3TdR) using 19F NMR spectroscopy.

The metabolism of 5-trifluoromethyl-2'-deoxyuridine (trifluridine, F3TdR) in male BALB/C mice has been studied by 19F NMR spectroscopy. Contrary to previous reports, a number of fluorinated metabolites were observed in urine, whole livers and blood samples taken from mice after i.p. injection of F3TdR. The present study describes the identification of two new metabolites in mouse urine using the 19F NMR technique. The NMR of crude urine showed the presence of F3TdR 5-trifluorothymine (F3T), the newly-identified metabolites, 5-trifluoromethyl-5,6-dihydrouracil (DHF3T) and 5-trifluoromethyl-5,6-dihydroxyracil (DOHF3T), and several new, as yet unidentified fluorinate metabolites. These two new metabolites were characterized by comparison to authentic compounds prepared synthetically from F3T.