Pharmacokinetic and bioequivalence study of new S-1 capsule in Chinese cancer patients

Abstract

S-1 is a multicomponent capsule containing tegafur, gimeracil, and oteracil potassium that has shown anticancer activity against numerous tumor types. However, S-1 capsules from different manufacturing companies have shown variations in pharmacokinetics and safety. Therefore, this multicenter, single-dose, randomized-sequence, open-label, two-way, self-crossover study was conducted to evaluate the bioequivalence of a newly developed generic S-1 (New Times Pharmaceutical Co., Ltd., Shandong, China) and the original brand-name S-1 capsule (Taiho Pharmaceutical Co., Ltd., Japan). Furthermore, the safety profiles of both products were compared. A total of 70 patients with 18 types cancer including breast, lung, gastric, and colorectal recruited at 5 hospitals who were randomly and alternatively administered 50 mg of the reference and test S-1 with a 7-day interval. Plasma concentrations of tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP), oteracil potassium, and 5-fluorouracil were detected using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Pharmacokinetic parameters, including maximum drug concentration (C_max), time to achieve C_max (T_max), half-life (t_1/2, area under the concentration-time curve from 0-time t (AUC_0-t), and AUC from 0-infinity (AUC_0-∞) were determined using non-compartmental analysis with DAS2.0 software. Bioequivalence of the reference and test S-1 was evaluated according to 90% confidence intervals (CIs) for ratios of AUC and C_max of S-1. Adverse events were evaluated by monitoring symptoms, physical and laboratory examinations, electrocardiogram, and subject interviews. No significant difference was observed in plasma concentrations and pharmacokinetic profiles of tegafur, CDHP, oteracil potassium, or 5-fluorouracil (p > 0.05) among cancer patients treated with the reference or test S-1 formulation. The 90% CIs of C_max, AUC_0-t, and AUC_0-∞ ratios were within the 80%-125% limit. The generic S-1 caused eight mild adverse events including liver dysfunction, diarrhea, nausea, fatigue, abnormal blood electrolytes, hyperglycemia, and dermal toxicity. Similarly, 18 mild adverse events were observed including dysarteriotony, diarrhea, nausea, fatigue, fever, hematotoxicity, abnormal blood electrolytes, hyperglycemia, dermal toxicity, and joint pain. There were no differences in the adverse event incidence between the two formulations. In conclusion, the newly developed generic S-1 showed similar pharmacokinetics to those of an original brand-name S-1 in cancer patients, thereby indicating bioequivalence. Furthermore, both treatments were well tolerated, suggesting that the cost-effective generic S-1 should be considered as a feasible option when treating patients.

Keywords: Bioequivalence; Pharmacokinetics; S-1; Safety; Tegafur.