Alternative pharmacokinetics of S-1 components, 5-fluorouracil, dihydrofluorouracil and alpha-fluoro-beta-alanine after oral administration of S-1 following total gastrectomy

Sustained delivery of a camptothecin prodrug - CZ48 by nanosuspensions with improved pharmacokinetics and enhanced anticancer activity

Background and aim: We have synthesized a novel lactone-stabilized camptothecin (CPT) analog named CZ48 and demonstrated its potent anticancer effects via bioconversion to the active CPT in earlier studies. Herein, we aimed to develop, optimize and characterize CZ48 nanosuspensions, for a sustained delivery of this drug in humans with an intravenous (i.v.) administration.

Methods and materials: A three-factor, five-level central composite design (CCD) was employed to establish the impacts of the critical influencing factors (concentrations (wt%) of CZ48, polysorbate 80 (Tween-80), and Pluronic^® F-108 (F-108)) on the responses (particle size and zeta potential). Based on the quantitative influencing factor–response relationships, two optimized CZ48 nanosuspensions of 197.22 ± 7.12 nm (NS-S) and 589.35 ± 23.27 nm (NS-L) were developed with the zeta potential values of –26.5 mV and –27.9 mV, respectively.

Results: CZ48 released from the nanosuspensions in a sustained manner in contrast to the rapid release from cosolvent in both PBS and human plasma. Moreover, NS-S exhibited more favored pharmacokinetic properties than NS-L, with a 31-fold prolonged elimination half-life of CPT, and a 2.4-fold enhanced CPT exposure over cosolvent. In efficacy study, NS-S exhibited significant tumor suppression and an improved survival rate with a higher tolerable dose, compared to CZ48 cosolvent.

Conclusion: We have successfully developed CZ48 nanosuspensions with significantly favorable pharmacokinetics and improved efficacy using CCD approach. The formulation offers potential merits as a preferred candidate for clinical trials with the prolonged CPT exposure, which is known to correlate with the clinical efficacy.

Development of an S-1 dosage formula based on renal function by a prospective pharmacokinetic study

BACKGROUND

S-1 is an oral anticancer drug, containing tegafur (a prodrug of 5-fluorouracil, 5-FU), 5-chloro-2,4-dihydroxypyridine, and potassium oxonate. As renal dysfunction is known to increase exposure of 5-FU following S-1 administration, the incidence of severe adverse reactions is increased in patients with impaired renal function. However, no reliable information on its dose modification for patients with renal dysfunction has been provided.

METHODS

We conducted a prospective pharmacokinetic study to develop an S-1 dosage formula based on renal function. Sixteen cancer patients with various degrees of renal function received a single dose of S-1 at 40 mg/m(2). A series of blood samples were collected at predefined times within 24 h to assess the plasma concentration profiles of 5-FU, 5-chloro-2,4-dihydroxypyridine, and tegafur. A mathematical model for the relationship between renal function and exposure of 5-FU was constructed by a population pharmacokinetic analysis.

RESULTS

The clearance of 5-FU following S-1 administration was related to body surface area and creatinine clearance in the range 15.9-108.8 mL/min as estimated by the Cockcroft-Gault equation. The S-1 dosage formula was derived as follows:[Formula: see text]where AUC is the area under the concentration-time curve, CLcr is creatinine clearance, and BSA is body surface area. The recommended daily doses of S-1 in Asia and Europe were also proposed as nomograms according to exposure matching to the previously reported area under the concentration-time curve of 5-FU, which confirmed the efficacy and toxicity in pivotal registration studies.

CONCLUSIONS

We have developed a novel formula for determining the S-1 dosage on the basis of renal function. Further validation is needed to confirm the formula for practical application.

The evaluation of surgical treatment for gastric cancer patients with noncurative resection

PURPOSE

This study aims to analyze the results of treatment in a series of 233 gastric cancer patients who underwent a noncurative resection.

METHODS

We performed a retrospective study of patients with noncurative treatment for advanced gastric cancer who were divided into three treatment groups: total gastrectomy (TG, n=150), distal gastrectomy (DG, n=44), and nonresection (NR, bypass procedure or chemotherapy only, n=39).

RESULTS

In multivariate analysis, surgical treatment (TG) and an absence of chemotherapy were significant independent prognostic factors for a poor survival. In the late period, the overall survival rate was significantly lower in the TG group than in the DG group (p=0.005) and was marginally lower than in the NR group (p=0.054). The resection group had a poorer compliance for chemotherapy than the NR group, and the TG group had a poorer compliance than the DG group (p<0.01). The morbidity rate was higher in the TG group than in the DG group (p<0.05).

CONCLUSIONS

TG is considered to be inappropriate for the treatment of noncurative gastric cancer because of the poor prognosis, high morbidity rates, and poor compliance for chemotherapy associated with the procedure. However, noncurative DG was acceptable and postoperative chemotherapy should be used in selected patients.

Randomized feasibility study of S-1 for adjuvant chemotherapy in completely resected Stage IA non-small-cell lung cancer: results of the Setouchi Lung Cancer Group Study 0701

The feasibility of the S-1 administration schedules (the 4-week versus the 2-week) showed no significant difference for adjuvant chemotherapy among pathological-Stage IA non–small-cell lung cancer patients.

Objective

The aim of this multicenter study was to determine the appropriate administration schedule for S-1, an oral fluoropyrimidine, for adjuvant chemotherapy in patients with completely resected pathological-Stage IA (tumor diameter, 2–3 cm) non–small-cell lung cancer.

Methods

Patients were randomly assigned to receive adjuvant chemotherapy consisting of either the 4-week oral administration of S-1 (80–120 mg/body/day) followed by a 2-week rest (Group A), or the 2-week oral administration of S-1 (80–120 mg/body/day) followed by a 1-week rest (Group B). The duration of adjuvant chemotherapy was 1 year in both arms. The primary endpoint was compliance, namely drug discontinuation-free survival, which was calculated using the Kaplan–Meier method with log-rank test.

Results

Eighty patients were enrolled in this study, and 76 patients actually received S-1 treatment. The drug discontinuation-free survival rates at 1 year were 49.1% in Group A and 52.7% in Group B (P = 0.373). The means of the relative dose intensities were 55.3% in Group A and 64.6% in Group B (P = 0.237). There were no treatment-related deaths. Patients with grade 3/4 toxicities were significantly more frequent in Group A (40.5%) than in Group B (15.4%, P = 0.021). The 2-year relapse-free survival rates were 97.5% in Group A and 92.5% in Group B, and the 2-year overall survival rates were 100% in both groups.

Conclusions

The feasibility showed no significant difference between the two groups among patients with completely resected Stage IA (tumor diameter, 2–3 cm) non–small-cell lung cancer.

Parsing interindividual drug variability: an emerging role for systems pharmacology

There is notable interindividual heterogeneity in drug response, affecting both drug efficacy and toxicity, resulting in patient harm and the inefficient utilization of limited healthcare resources. Pharmacogenomics is at the forefront of research to understand interindividual drug response variability, but although many genotype-drug response associations have been identified, translation of pharmacogenomic associations into clinical practice has been hampered by inconsistent findings and inadequate predictive values. These limitations are in part due to the complex interplay between drug-specific, human body and environmental factors influencing drug response and therefore pharmacogenomics, whilst intrinsically necessary, is by itself unlikely to adequately parse drug variability. The emergent, interdisciplinary and rapidly developing field of systems pharmacology, which incorporates but goes beyond pharmacogenomics, holds significant potential to further parse interindividual drug variability. Systems pharmacology broadly encompasses two distinct research efforts, pharmacologically-orientated systems biology and pharmacometrics. Pharmacologically-orientated systems biology utilizes high throughput omics technologies, including next-generation sequencing, transcriptomics and proteomics, to identify factors associated with differential drug response within the different levels of biological organization in the hierarchical human body. Increasingly complex pharmacometric models are being developed that quantitatively integrate factors associated with drug response. Although distinct, these research areas complement one another and continual development can be facilitated by iterating between dynamic experimental and computational findings. Ultimately, quantitative data-derived models of sufficient detail will be required to help realize the goal of precision medicine.

Dilemma of dihydropyrimidine dehydrogenase deficiency in colorectal cancer patients: is Uftoral® the right answer?

SUMMARY 

Fluoropyrimidines (5-fluorouracil, capecitabine, S-1, Uftoral® [UFT; Merck, Germany]) and their derivatives are effective in management of colorectal cancer. DPD deficiency is not routinely tested and is usually diagnosed after a patient has severe/grade IV toxicity secondary to the use of 5-fluorouracil or capecitabine. Once DPD deficiency is diagnosed, there are sparse data on the use of UFT or raltitrexed and there are no comparable outcome data with well-known regimens like infusional 5-fluorouracil, leucovorin oxaliplatin (FOLFOX) and infusional 5-fluorouracil, leucovorin, irinotecan (FOLFIRI). Here we report the first case series from India of DPD deficiency and the use of UFT.

The pharmacokinetics of the effervescent vs. conventional tramadol/paracetamol fixed-dose combination tablet in patients after total gastric resection

BACKGROUND

Tramadol/paracetamol is a fixed-dose combination prescribed for the relief of moderate to severe pain. The combination acts synergistically and guarantees the rapid onset of paracetamol and the prolonged analgesic effect of tramadol with good tolerability. These drugs are often used in various formulations in the treatment of patients with postoperative pain, e.g. after stomach resection. Gastrectomy leads to pathophysiological changes within the alimentary tract, which may affect the process of drug absorption. The aim of the research was an analysis of the pharmacokinetics of tramadol/paracetamol from effervescent and conventional tablets in patients after total gastrectomy.

METHODS

The research was carried out on patients after gastrectomy with Roux-en-Y reconstruction. The patients received two tramadol/paracetamol fixed-dose combination tablets in a single orally administered dose of 75/650 mg (2 × 37.5/325 mg). The patients were subjected to one of the two study drug group with: I. effervescent tablet (ET) (n = 14; mean [SD] age, 63.4 [10.1] years; weight, 75.5 [15.3]kg; and BMI, 26.0 [4.6]kg/m(2)) and II. conventional tablet (CT) (n = 12; mean [SD] age, 66.8 [7.7] years; weight, 79.8 [17.8]kg; and BMI, 27.4 [5.3]kg/m(2)). Blood samples were collected within 10 h after the drug administration. The plasma concentrations of tramadol and paracetamol were measured with validated HPLC (high-performance liquid chromatography) method with UV detection.

RESULTS

The comparison of the paracetamol and tramadol C(max) ratio for the ET group with that of the CT group gave ratios of 1.16 [90% confidence interval (CI) 1.06, 1.27] and 0.86 (90% CI 0.72, 1.02), respectively. The comparison of the paracetamol and tramadol AUC(0-t) ratio for the ET group with that of the CT group showed ratios of 0.99 (90% CI 0.88, 1.10) and 1.00 (90% CI 0.82, 1.22), respectively. The comparison of the difference for the effervescent and conventional formulation gave an estimated decrease in t(max) of 0.5 h for paracetamol and 0.13 h for tramadol.

CONCLUSIONS

In view of the changes in the pharmacokinetics of paracetamol and tramadol in the patients after gastric resection for both formulations compared the conventional tablet seems to be more appropriate due to the comparable rate of absorption of both substances, higher concentrations of tramadol and comparable exposure to paracetamol.

Dose-finding study on adjuvant chemotherapy with S-1 plus oxaliplatin for gastric cancer

Gastric cancer (GC) is the fourth most common type of cancer, accounting for an estimated one million new cases annually worldwide. Locally advanced GC often recurs, even following curative surgical resection. Therefore, there is a need for an effective adjuvant chemotherapy regimen. The aim of this trial was to investigate the maximum tolerated dose (MTD) of S-1 when administered in combination with oxaliplatin in postoperative GC patients. Oxaliplatin was administered at a fixed dose of 130 mg/m² on day 1. S-1 was administered from day 1 to 14 of a 3-week cycle and escalated by 10 mg/m²/day from 60 to 80 mg/m²/day. A total of 15 patients were enrolled in this study. No dose-limiting toxicities (DLTs) occurred at level 1 (S-1, 60 mg/m²; n=3). One case of DLT (grade 3 vomiting) occurred at level 2 (S-1, 70 mg/m²; n= 6), whereas 2 cases of grade 3 vomiting were observed at level 3 (S-1, 80 mg/m²; n=6). Based on these results, the MTD of S-1 was initially determined to be 70 mg/m². Furthermore, we observed that cytochrome P450 2A6 (CYP2A6) 41349640C>G was associated with severe neutropenia (C/C vs. C/G vs. G/G = 0 vs. 33.33 vs. 100%; P=0.03297, Fisher's exact test) during the entire course of the treatment.

Feasibility of adjuvant chemotherapy with S-1 consisting of a 4-week administration and a two-week rest period in patients with completely resected non-small cell lung cancer

The efficacy of adjuvant chemotherapy with S-1 in patients with completely resected non-small cell lung cancer (NSCLC) has yet to be clarified, and the appropriate schedule for the adjuvant chemotherapy with S-1 remains unknown. A phase II study was conducted to evaluate the feasibility and efficacy of adjuvant chemotherapy with S-1. Patients enrolled in this study were 20-75 years old, had pathological stage IB-IIIA NSCLC, and had received complete resection of NSCLC. S-1 (80 mg/m²) was administered orally to the patients for four weeks followed by a two-week rest period (conventional schedule), for a maximum of eight cycles. The primary endpoint was relative dose intensity (RDI), while the secondary endpoints were safety and 1 year of disease-free survival (1y-DFS). Between May 2007 and October 2009, 28 patients were enrolled. The RDI was 63.1% (95% CI, 48.6-77.7). No grade 3 or worse hematological toxicity was observed. Grade 3 non-hematological toxicities were observed in four patients. No grade 4 or worse hematological toxicity was detected. The probability of 1y-DFS was 85.7% (95% CI, 72.8-98.6). In the subgroup analysis, the median RDI of patients over 65 years old was lower compared to the other patients (44.8 vs. 100%; P=0.013; Mann-Whitney U test). Creatinine clearance (CCr) was lower in the older group, with more grade 2 or 3 non-hematological toxicities in the elderly patients. These results suggest that the conventional schedule of adjuvant chemotherapy with S-1 is not likely to be feasible in older patients with completely resected NSCLC.

Lacrimal drainage obstruction in gastric cancer patients receiving S-1 chemotherapy

BACKGROUND

This study was conducted to determine the incidence and clinical characteristics of lacrimal drainage obstruction (LDO) in patients receiving S-1 chemotherapy.

PATIENTS AND METHODS

Consecutive 170 patients with gastric cancer who underwent curative surgery and received adjuvant S-1 chemotherapy were enrolled. S-1 was administered orally (40 mg/m2 b.i.d. on days 1-28 every 6 weeks) for 1 year. Ophthalmologic examinations were carried out on patients complaining of epiphora.

RESULTS

Thirty-one patients (18%) developed epiphora. Among 31 patients, 25 underwent ophthalmologic examinations and 22 (88%) were diagnosed with LDO. The median time to the onset of LDO was 2.9 months. The most common site of obstruction was the nasolacrimal duct [86% (19/22)]; punctal [23% (5/22)] and canalicular obstruction [14% (3/22)] were also noted. In multivariate analysis, total gastrectomy [versus partial gastrectomy: hazard ratio (HR), 2.9; P=0.014] and creatinine clearance<50 ml/min (versus ≥50 ml/min: HR, 2.9; P=0.038) were independent risk factors for the development of LDO.

CONCLUSION

Considering the high incidence of LDO in patients receiving S-1 chemotherapy, oncologists should be alert to epiphora and cooperate with ophthalmologists in the early stages to improve the quality of life of patients and avoid more complicated ophthalmologic procedures.

Management of adjuvant S-1 therapy after curative resection of gastric cancer: dose reduction and treatment schedule modification

BACKGROUND

The aim of this study was to determine the optimal management of adjuvant S-1 therapy for stage II or III gastric cancer, encompassing the details of dose reduction and treatment schedule modification.

METHODS

We retrospectively examined 97 patients with stage II or III gastric cancer who received S-1 chemotherapy following gastrectomy between January 2003 and December 2007. S-1 (80 mg/m² per day) was orally administered twice daily for 4 weeks, followed by a 2-week rest. As a rule, treatment was continued for 1 year after gastrectomy. Dose reduction or treatment schedule modification was performed according to toxicity profiles.

RESULTS

Among the 97 patients, 57 (59%) underwent dose reduction at least once and 39 (40%) received treatment schedule modification. Of the 57 patients who required dose reduction, 45 (79%) underwent reduction within 3 months of the beginning of treatment. The most common reasons for dose reduction were anorexia (47%), followed by diarrhea (32%), leukopenia (24%), and rash (16%), with the reasons overlapping. Although the difference in the requirement for dose reduction was not significant, patients with a low creatinine clearance level or those who underwent total gastrectomy had a greater tendency to require dose reduction. The duration of the S-1 treatment period was at least 3 months in 88% of the patients, at least 6 months in 82%, and the planned 1-year period in 73% of the patients.

CONCLUSIONS

In most patients, the planned 1-year adjuvant S-1 therapy for stage II or III gastric cancer could be completed by modifying the dose reduction and treatment schedule.

Feasibility study of adjuvant chemotherapy with S-1 plus cisplatin for gastric cancer

PURPOSE

To evaluate the feasibility of S-1 plus cisplatin as adjuvant chemotherapy for stage III gastric cancer after curative resection.

METHODS

Japanese patients with stage III gastric cancer who underwent gastrectomy with D2 lymph node resection were enrolled. Treatment consisted of 3 cycles of S-1 (80 mg/m(2)/day, b.i.d.) for 21 days followed by a 14-day rest, and cisplatin (60 mg/m(2) iv) on day 8. After that, S-1 monotherapy was given on days 1-28 every 6 weeks until 1-year postsurgery. After protocol amendment, the first chemotherapy cycle consisted of S-1 monotherapy; cisplatin was added to cycles 2, 3, and 4, followed by S-1 monotherapy up to 1-year postsurgery. The primary endpoint was the completion rate of three cycles of S-1 plus cisplatin.

RESULTS

A total of 63 enrolled patients have been evaluated. Grade 3/4 toxicities included neutropenia (40%), anorexia (28%), and febrile neutropenia (4%) before protocol amendment (n = 25), and neutropenia (37%), anorexia (8%), and febrile neutropenia (3%) after amendment implementation (n = 38). Excluding ineligible cases, treatment completion rates were 57% (12/21) before and 81% (30/37) after the protocol amendment.

CONCLUSIONS

The amended S-1 plus cisplatin is more feasible than the original protocol because of early dose reduction of S-1 prior to cisplatin addition and greater recovery time from surgery prior to cisplatin. This treatment should be considered as a feasible experimental arm for the next postoperative adjuvant phase III trial.

A phase II and pharmacokinetic study of first line S-1 for advanced gastric cancer in Taiwan

PURPOSE

To evaluate the efficacy, safety and pharmacokinetic profiles of S-1, which composed of tegafur (FT, a prodrug of 5-FU), 5-chloro-2,4-dihydroxypyridine and potassium oxonate (Oxo), in Taiwanese advanced gastric cancer (AGC) patients.

METHODS

Patients with chemo-naïve, histologically confirmed AGC were eligible. S-1 was given orally at dose of 40, 50 or 60 mg, twice daily for patients with body surface <1.25, 1.25-1.5 and >1.5 m(2), respectively, on day 1-28 every 42 days/cycle.

RESULTS

Thirty-four patients were included. On intent-to-treat analysis, the overall response rate, median progression-free and overall survival were 35.3% [95% confidence interval (CI): 19.2-51.3%], 2.9 (95% CI: 2.4-5.8) months and 9.8 (95% CI: 6.1-NA) months, respectively. The most common grade 3-4 toxicities were anemia 23.5% and neutropenia 11.8%. There were two treatment-related mortality, which occurred in patients with suboptimal renal function underestimated by serum creatinine level at study entry. Single-dose pharmacokinetic study showed trend toward lower AUC(5-FU), and higher AUC(FT) and AUC(Oxo) comparing to most Western reports.

CONCLUSIONS

The efficacy, toxicity and pharmacokinetic profiles of S-1 in current study are compatible with those from other Asian populations. Accurate renal function assessment and more closely monitoring is mandatory for S-1 therapy in patients with low body mass. Literature review suggests that, besides AUC(5-FU), AUC(Oxo) may also attribute to the difference in the compliance to S-1 between Asian and Caucasian populations.

Plasma pharmacokinetics after combined therapy of gemcitabine and oral S-1 for unresectable pancreatic cancer

Background

The combination of gemcitabine (GEM) and S-1, an oral 5-fluorouracil (5-FU) derivative, has been shown to be a promising regimen for patients with unresectable pancreatic cancer.

Methods

Six patients with advanced pancreatic cancer were enrolled in this pharmacokinetics (PK) study. These patients were treated by oral administration of S-1 30 mg/m² twice daily for 28 consecutive days, followed by a 14-day rest period and intravenous administration of GEM 800 mg/m² on days 1, 15 and 29 of each course. The PK parameters of GEM and/or 5-FU after GEM single-administration, S-1 single-administration, and co-administration of GEM with pre-administration of S-1 at 2-h intervals were analyzed.

Results

The maximum concentration (Cmax), the area under the curve from the drug administration to the infinite time (AUCinf), and the elimination half-life (T1/2) of GEM were not significantly different between GEM administration with and without S-1. The Cmax, AUCinf, T1/2, and the time required to reach Cmax (Tmax) were not significantly different between S-1 administration with and without GEM.

Conclusion

There were no interactions between GEM and S-1 regarding plasma PK of GEM and 5-FU.

In vitro and in vivo evidence that a combination of lapatinib plus S-1 is a promising treatment for pancreatic cancer

Lapatinib is a small molecule inhibitor of both HER2 and the epidermal growth factor receptor (EGFR). We investigated the effect of treatment with lapatinib alone or in combination with a fluoropyrimidine derivative S-1 against pancreatic cancer. The HER2/EGFR expression in each of the four pancreatic cancer cell lines MiaPaca-2, PANC-1, Capan-1 and Capan-2 was measured by flow cytometry. The anti-tumor effects of lapatinib (30 mg/kg) and/or S-1 (10 mg/kg) were evaluated using female BALB/c nude mice xenografts generated using these four cell lines. Synergy between lapatinib and S-1 was examined by median effect analysis in vitro. Resected pancreatic cancer tissues from 137 patients were immunohistochemically stained with anti-human HER2 and EGFR antibodies. The administration of lapatinib as a single agent substantially suppressed tumor growth in vivo of all pancreatic cancer cell lines examined. A strong correlation was observed between HER2 expression and the anti-tumor effect of lapatinib in vivo. Lapatinib synergized with S-1 to inhibit the tumor growth of MiaPaca-2 and PANC-1 xenografts. When used as a single agent in vitro, lapatinib barely inhibit the cell growth of any cell line. However, lapatinib synergized with the anti-tumor activity of the S-1 components 5-fluorouracil and 5-chloro-2,4-dihydrogenase against all cell lines. Immunohistochemical staining demonstrated that 70% of the pancreatic cancers overexpressed HER2 and/or EGFR. Both lapatinib monotherapy and combined treatment with S-1 may be promising treatments for patients with pancreatic cancers; the majority these cancers express lapatinib target molecules.

Phase I/II and pharmacokinetic study of S-1 and oxaliplatin in previously untreated advanced gastric cancer

BACKGROUND

We aimed to determine the maximum-tolerated dose (MTD) of S-1 when given with oxaliplatin, to evaluate S-1 pharmacokinetics, and to determine the efficacy and safety of this regimen as a first-line treatment for advanced gastric cancer (AGC).

METHODS

Oxaliplatin was fixed at a dose of 130 mg/m2 on day 1 (D1). S-1 was administered from D1 to D14 of a 3-week cycle, and escalated by 10 mg/m2 per day from 70 mg/m2 per day up to 100 mg/m2 per day. Pharmacokinetic analyses were performed following a single dose of S-1 on D-5 and D1 of the first cycle.

RESULTS

In phase I (n=18), MTD was not defined. In phase II (n=47) with the planned maximum dose, partial response was achieved in 26 patients (55.3%) and stable disease in 14 patients (29.8%). The median time to progression was 6.6 months (95% CI 4.0-9.2 months) and the median overall survival was 12.5 months (95% CI 9.2-15.9 months). Frequent grade 3/4 toxicities included thrombocytopenia (39%), neutropenia (28%), anemia (17%), and leukopenia (13%). There was one grade 5 febrile neutropenia during the first cycle.

CONCLUSIONS

The pharmacokinetics of S-1 was not influenced by oxaliplatin. S-1/Oxaliplatin combination therapy is highly active against AGC and has a favorable toxicity profile.

Development history and concept of an oral anticancer agent S-1 (TS-1): its clinical usefulness and future vistas

Dushinsky et al. left a great gift to human beings with the discovery of 5-fluorouracil (5-FU). Approximately 50 years have elapsed from that discovery to the development of S-1 (TS-1^®). The concept of developing an anticancer agent that simultaneously possesses both efficacy-enhancing and adverse reaction-reducing effects could be achieved only with a three-component combination drug. S-1 is an oral anticancer agent containing two biochemical modulators for 5-FU and tegafur (FT), a metabolically activated prodrug of 5-FU. The first modulator, 5-chloro-2,4-dihydroxypyridine (CDHP), enhances the pharmacological actions of 5-FU by potently inhibiting its degradation. The second modulator, potassium oxonate (Oxo), localizing in mucosal cells of the gastrointestinal (GI) tract after oral administration, reduces the incidence of GI toxicities by suppressing the activation of 5-FU in the GI tract. Thus, S-1 combines FT, CDHP and Oxo at a molar ratio of 1:0.4:1. In 1999–2007, S-1 was approved for the treatment of the following seven cancers: gastric, head and neck, colorectal, non-small cell lung, breast, pancreatic and biliary tract cancers. ‘S-1 and low-dose cisplatin therapy’ without provoking Grade 3 non-hematologic toxicities was proposed to enhance its clinical usefulness. Furthermore, ‘alternate-day S-1 regimen’ may improve the dosing schedule for 5-FU by utilizing its strongly time-dependent mode of action; the former is characterized by the low incidences of myelotoxicity and non-hematologic toxicities (e.g. ≤Grade 1 anorexia, fatigue, stomatitis, nausea, vomiting and taste alteration). These two approaches are considered to allow long-lasting therapy with S-1.