s-1-(combination) and 5-fluoropyrimidine

Topics: Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Biliary Tract Neoplasms; Capecitabine; Clinical Trials as Topic; Deoxycytidine; Drug Combinations; Fluorouracil; Humans; Oxonic Acid; Pyridines; Pyrimidines; Tegafur; Uracil

The fluoropyrimidine anticancer agent 5-fluorouracil (5-FU) is active in a wide range of solid tumors, particularly gastric, colorectal, and head and neck cancers. Whilst infusional 5-FU is associated with higher response rates and a favorable safety profile as compared to the classical i.v. bolus administration, prolonged infusions can be inconvenient for the patients and catheter-related problems are common complications. An oral 5-FU formulation would allow for sustained 5-FU plasma concentrations, mimicking the pharmacokinetics (PK) of a continuous infusion with the addition of convenience of administration. The oral administration of 5-FU itself is not feasible due to the high activity of dihydropyrimidine dehydrogenase in the gut wall, which causes rapid metabolism of the drug, and results in decreased and erratic absorption of 5-FU and non-linear PK. To bypass this problem, oral fluoropyrimidine derivatives were developed either in the form of 5-FU prodrugs (i.e. tegafur, doxifluridine or capecitabine), or as enzyme inhibitors (i.e. eniluracil) administered with 5-FU, or as both prodrugs and enzyme inhibitors (i.e. S-1, UFT or BOF-A2). This review will focus on the oral fluoropyrimidine S-1, which consists of the 5-FU prodrug tegafur (ftorafur, FT) and two enzyme inhibitors, i.e. CDHP (5-chloro-2,4-dihydroxypyridine) and OXO (potassium oxonate), in a molar ratio of 1(FT):0.4 (CDHP):1(OXO). Phase II trials have demonstrated that S-1, as a single agent, is active for the treatment of gastric, colorectal, head and neck, breast, non-small cell lung, and pancreatic cancers. Phase III trials are currently underway in gastric cancer and these results are awaited to confirm the phase II findings. Furthermore, the combination of S-1 with cisplatin (CDDP), irinotecan or docetaxel for the treatment of gastric cancer and with CDDP for non-small cell and pancreatic cancer is feasible and active. The activity observed with S-1 in the phase II studies is at least equivalent, if not better, than continuous i.v. and bolus 5-FU and the other oral fluoropyrimidines. Thus, we may finally be seeing the realization of oral treatments for the management of various solid tumors and could be on the brink of a new approach to treatment strategies.

Topics: Administration, Oral; Animals; Antineoplastic Combined Chemotherapy Protocols; Clinical Trials as Topic; Dosage Forms; Drug Administration Schedule; Drug Combinations; Drug Delivery Systems; Drug Evaluation, Preclinical; Enzyme Inhibitors; Gastrointestinal Neoplasms; Humans; Oxonic Acid; Prodrugs; Pyridines; Pyrimidines; Tegafur

Paclitaxel, S1 and their combined sequential administration is proposed to be examined installing UFT as an active control of adjuvant chemotherapy for curatively resected T3-4 gastric cancer in a multicenter Phase III trial. The primary endpoint is disease-free survival and the secondary endpoints are incidence of adverse events, overall survival and compliance. The sample size is 370 per treatment arm (1480 in total) for two hypotheses of the superiority of sequential use of paclitaxel followed by oral fluoropyrimidines to fluoropyrimidines (UFT/S1) alone and the non-inferiority of S1 to UFT to be tested by two-by-two factorial design. Abdominal CT or US is performed every 3 months in the first 2 years and every 6 months thereafter for 3 years in total to ensure recurrence data collection. This trial could appraise sequential combination therapy and efficacy of new drugs as adjuvant for gastric cancer treatment.

Topics: Administration, Oral; Adult; Aged; Aged, 80 and over; Antineoplastic Combined Chemotherapy Protocols; Chemotherapy, Adjuvant; Disease-Free Survival; Drug Administration Schedule; Drug Combinations; Endpoint Determination; Humans; Middle Aged; Oxonic Acid; Paclitaxel; Pyridines; Pyrimidines; Stomach Neoplasms; Tegafur; Uracil

The oral fluoropyrimidine S-1, which consists of a mixture of a 5-fluorouracil (5-FU) prodrug (tegafur), a dihydropyrimidine dehydrogenase inhibitor [5-chloro-2,4-dihydroxypyrimidine (CDHP)], and an inhibitor of orotate phosphoribosyltransferase [potassium oxonate (oxonic acid)], was developed to increase the feasibility and therapeutic index of 5-FU administered orally. The principal objective of this study was to assess the feasibility of administering S-1 on a once-daily-for-28-day schedule every 5 weeks, determine the maximum tolerated dose, characterize the pharmacokinetics of S-1, and seek evidence of anticancer activity.. Patients with advanced solid malignancies were treated with escalating doses of S-1 on a once-daily oral schedule for 28 days every 5 weeks. The maximum tolerated dose was defined as the highest dose in which fewer than two of the first six new patients experienced dose-limiting toxicity. The pharmacokinetic profiles of the tegafur, CDHP, and oxonic acid constituents were characterized.. Twenty patients were treated with 72 courses of S-1 at three dose levels ranging from 50 to 70 mg/m(2)/day. Diarrhea, which was often associated with abdominal discomfort and cramping, was the principal dose-limiting toxicity of S-1 on this protracted schedule. Nausea, vomiting, mucositis, fatigue, and cutaneous effects were also observed but were rarely severe. Myelosuppression was modest and uncommon. A partial response and a 49% reduction in tumor size were observed in patients with fluoropyrimidine- and irinotecan-resistant colorectal carcinoma. The pharmacokinetic data suggested potent inhibition of 5-FU clearance by CHDP, with resultant 5-FU exposure at least 10-fold higher than that reported from equitoxic doses of tegafur modulated by uracil in the oral fluoropyrimidine UFT.. The recommended dose for Phase II studies of S-1 administered once daily for 28 consecutive days every 5 weeks is 50 mg/m(2)/day. The pharmacokinetic data indicate substantial modulation of 5-FU clearance by CDHP. Based on these pharmacokinetic data, the predictable toxicity profile of S-1, and the low incidence of severe adverse effects at the recommended Phase II dose, evaluations of S-1 on this schedule are warranted in malignancies that are sensitive to the fluoropyrimidines.

Topics: Adult; Aged; Antimetabolites, Antineoplastic; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Area Under Curve; Colorectal Neoplasms; Dose-Response Relationship, Drug; Drug Combinations; Enzyme Inhibitors; Female; Follow-Up Studies; Humans; Lung Neoplasms; Male; Maximum Tolerated Dose; Middle Aged; Orotate Phosphoribosyltransferase; Oxonic Acid; Pyridines; Pyrimidines; Stomach Neoplasms; Tegafur; Time Factors