Determination of S-1 (combined drug of tegafur, 5-chloro-2,4-dihydroxypyridine and potassium oxonate) and 5-fluorouracil in human plasma and urine using high-performance liquid chromatography and gas chromatography-negative ion chemical ionization mass spectrometry

GC Determination of Fluorouracil in Serum by Using Hexafluroroacetylacetone as Derivatizing Reagent

A gas chromatographic (GC) procedure has been developed for the determination of fluorouracil (5-FU) after pre-column derivatization with hexafluoroacetylacetone. GC separation was from column DB-1 (30 m × 0.32 mm id) and the determination was by flame-ionization detection. The derivatization conditions were optimized at pH 4, heating at 90°C for 40 min and extraction of the derivative was in chloroform. Using the conditions nucleobases cytosine, uracil, thymine, adenine and guanine separated completely from fluorouracil. The linear calibration range and LOD for 5-fluorouracil were 0.5-40.0 and 0.2 μg/mL, respectively. The derivatization, elution and separation were repeatable in terms of retention time and peak height/peak area (n = 5) and relative standard deviations (RSD) were within 3.5%. The method was applied for the analysis of serum spiked with 5-FU with recovery of 95.5-97.5% with RSD 1.5-3.1%.

High-throughput method to analyze tegafur and 5-fluorouracil in human tears and plasma using hydrophilic interaction liquid chromatography/tandem mass spectrometry

RATIONALE

We developed a new high-throughput method to analyze tegafur (FT) and 5-fluorouracil (5-FU) in tear and plasma samples using hydrophilic interaction liquid chromatography (HILIC)/tandem mass spectrometry (MS/MS).

METHODS

The tear samples (10 μL) spiked with FT, 5-FU, and 5-chlorouracil (internal standard) were diluted using 40 μL of 2 M ammonium acetate and 250 μL of acetonitrile with 2% formic acid; 20 μL of plasma spiked with the two drugs and internal standard was diluted with 80 μL of 2 M ammonium acetate and 500 μL of acetonitrile with 2% formic acid. After centrifugation, the clear supernatant extract (15 μL) was directly injected into the HILIC/MS/MS instrument, and each drug was separated on a Unison UK-Amino column (50 mm × 3 mm i.d., 3 μm particle size) with a linear gradient elution system composed of 10 mM ammonium acetate (pH 6.8) and acetonitrile at a flow rate of 0.7 mL/min. We performed quantification by multiple reaction monitoring (MRM) with negative-ion atmospheric-pressure chemical ionization.

RESULTS

Distinct peaks were observed for the drugs on each MRM channel within 2 min. The regression equations showed good linearity within the range 0.04-4.0 μg/mL for the tear and plasma samples with detection limits at 0.02-0.04 μg/mL. Recoveries for target analytes (FT and 5-FU) for the tear and plasma samples were in the 94-128% and 94-104% ranges, respectively. The intra- and inter-day coefficients of variation for the two drugs were lower than 10.8%. The accuracies of quantitation were 97-115% for both samples.

CONCLUSIONS

We established a high-throughput, reproducible, and practical procedure for analyzing FT and 5-FU in human tear and plasma samples using HILIC/MS/MS analysis with an aminopropyl-bonded mixed-mode separation column. This method can be applied to the high-throughput routines used in clinical analyses.

Pharmacokinetic study of the oral fluorouracil antitumor agent S-1 in patients with impaired renal function

Although dose reduction of S-1 is recommended for patients with impaired renal function, dose modification for such patients has not been prospectively evaluated. The aim of the present study was to investigate the pharmacokinetic parameters of 5-fluorouracil, 5-chloro-2,4 dihydroxypyridine and oteracil potassium, and to review the recommended dose modification of S-1 in patients with renal impairment. We classified patients receiving S-1 into 4 groups according to their renal function, as measured using the Japanese estimated glomerular filtration rate (eGFR) equation. The daily S-1 dose was adjusted based on the patient's eGFR and body surface area. Blood samples were collected for pharmacokinetic analysis. A total of 33 patients were enrolled and classified into 4 groups as follows: 10 patients in cohort 1 (eGFR ≥ 80 mL/min/1.73 m² ), 10 patients in cohort 2 (eGFR = 50-79 mL/min/1.73 m² ), 10 patients in cohort 3 (eGFR = 30-49 mL/min/1.73 m² ), and 3 patients in cohort 4 (eGFR < 30 mL/min/1.73 m² ). Those in cohorts 3 and 4 treated with an adjusted dose of S-1 showed a similar area under the curve for 5-fluorouracil (941.9 ± 275.6 and 1043.5 ± 224.8 ng/mL, respectively) compared with cohort 2 (1034.9 ± 414.3 ng/mL). Notably, while there was a statistically significant difference between cohort 1 (689.6 ± 208.8 ng/mL) and 2 (P = 0.0474) treated with an equal dose of S-1, there was no significant difference observed in the toxicity profiles of the cohorts. In conclusion, dose adjustment of S-1 in patients with impaired renal function using eGFR is appropriate and safe.

A novel approach to the application of hexagonal mesoporous silica in solid-phase extraction of drugs

Mesoporous silica with hexagonal type structure containing amine functional group was introduced. Firstly, aminopropyl hexagonal mesoporous silica was synthetized in a co-condensation process, via templating route of n-dodecylamine. Then synthesized mesoporous material were characterized, and FT-IR spectrum confirmed the presence of amine group and CHN analysis determined the amount of organic layer. The high surface area (750 m²/g) was determined by applying nitrogen adsorption-desorption technique. The morphology was examined by scanning electron microscopy which proved hexagonal structure. The crystallinity of mesoporous material was observed in XRD pattern of this material. According to previous background of such material in adsorbing drug, herein, the efficiency of this material in adsorbing of 5-fluorouracil was evaluated through solid phase extraction method in aqueous and plasma media with high performance liquid chromatography. The extraction efficiency was evaluated for drug concentrations of 500-2000 ng/ml by means of 5-20 mg/ml hexagonal mesoporous silica in both media. The results showed good to excellent recovery rate of in both aqueous and plasma medium which confirmed that the aminopropyl functionalized hexagonal mesoporous silica could be considered as promising device for drug bioanalysis.

Phase II study of S-1 plus leucovorin in patients with metastatic colorectal cancer: Regimen of 1 week on, 1 week off

A phase II study of S‐1 plus leucovorin (LV) given in a 4‐week schedule (2 weeks’ administration followed by 2 weeks’ rest) for patients with untreated metastatic colorectal cancer (mCRC) showed that the combination was effective, but grade 3 toxicities (diarrhea, stomatitis and anorexia) occurred at a relatively high rate. In this phase II study, we evaluated the efficacy and safety of a 2‐week schedule of S‐1 plus LV. Patients with mCRC received oral S‐1 (40–60 mg) and LV (25 mg) twice daily for 1 week, followed by 1 week's rest. Treatment was repeated until disease progression or unacceptable toxicity. The primary endpoint was response rate. The pharmacokinetics of S‐1 and LV in Chinese patients were evaluated on day 1 of the first cycle. Seventy‐three patients were enrolled in Japan and China. Of 71 eligible patients, the response rate was 53.5%, and the disease control rate was 83.1%. Median progression‐free survival and median overall survival were 6.5 and 24.3 months, respectively. The incidences of grade 3 toxicities were diarrhea 8.3%, stomatitis 8.3%, anorexia 2.8% and neutropenia 9.7%. There were no treatment‐related deaths. The pharmacokinetics profiles of S‐1 plus LV in Chinese patients were similar to those in Japanese patients. This 2‐week schedule of S‐1 plus LV showed good efficacy and better tolerability than the 4‐week schedule. This therapy will be the base regimen for mCRC to be added by other cytotoxic or molecular‐targeted drugs. The optimized treatment schedule for S‐1 plus LV was 1 week on and 1 week off.

A phase I dose-escalation study of eribulin and S-1 for metastatic breast cancer

Background:

We evaluated the safety, maximum-tolerated dose (MTD), pharmacokinetics, recommended dose for phase II (P2RD), and preliminary anticancer activity of a combination eribulin and S-1 therapeutic in metastatic breast cancer patients pretreated with anthracycline and taxane.

Method:

Patients aged 20–74 years were recruited. In level 1, patients received S-1 (65 mg m⁻²) from day 1 to 14, and eribulin (1.1 mg m⁻²) on day 1 and 8 in a 21-day cycle. In level 2, eribulin was increased to 1.4 mg m⁻². In level 3, S-1 was increased to 80 mg m⁻².

Results:

Twelve patients were enrolled into three cohorts. Planned dose escalation was completed, with one case exhibiting dose-limiting toxicity (grade 3 hypokalaemia) at level 3, without reaching the MTD. The P2RD was determined to be level 2 (eribulin 1.4 mg m⁻² and S-1 65 mg m⁻²). The most common grade 3 or 4 toxicity was neutropenia (83.3%), followed by febrile neutropenia (25.0%). Five of eleven patients (41.7%) with measurable disease had a partial response. Pharmacokinetics were characterised by dose-dependent elimination and nonlinear exposure.

Conclusion:

Dose level 3 was not tolerated owing to febrile neutropenia development. Thus, intermediate dose level 2 was recommended for further evaluation. Preliminary antitumour activity warrants further investigation in this setting.

Feasibility and pharmacokinetics of combined therapy with S-1 and trastuzumab in patients with human epidermal growth factor receptor 2-positive metastatic or recurrent breast cancer

BACKGROUND

To clarify the tolerance and pharmacokinetics of combined therapy with S-1 and trastuzumab in patients with human epidermal growth factor receptor 2 (HER2)-positive metastatic or recurrent breast cancer.

METHODS

From January 2008 through to September 2009, combined therapy with S-1 and trastuzumab was given to 7 patients with HER2-positive metastatic or recurrent breast cancer. The incidence of adverse events and the pharmacokinetics of tegafur, 5-fluorouracil, and gimeracil in plasma were studied.

RESULTS

One patient had grade 3 leukopenia, and another had a grade 3 elevation of alanine aminotransferase. All other adverse events were grade 2 or lower. The combination of S-1 and trastuzumab did not cause any new adverse events. The incidence of adverse events was similar to those associated with S-1 alone. The median number of treatment cycles was 11. The pharmacokinetics of tegafur, 5-fluorouracil, and gimeracil after treatment with S-1 plus trastuzumab did not markedly differ from those after S-1 alone.

CONCLUSIONS

Combined therapy with S-1 and trastuzumab did not cause any new adverse events, administration continuity was good, and the therapy was well tolerated.

Development and validation of a HPLC-MS/MS method with electrospray ionization for quantitation of potassium oxonate in human plasma: Application to a pharmacokinetic study

A rapid, sensitive and specific HPLC-MS/MS method was developed and validated for the quantification of potassium oxonate (Oxo) in human plasma using [¹³C₂,¹⁵N₃]-Oxo as an internal standard (IS). The target substance was separated from human plasma using the solid-phase extraction method. Chromatography separation was performed on a Waters:Atlantis dC¹⁸ column (150×4.6 mm, 5.0 μm) with a mobile phase consisting of H₂O with 0.1% formic acid in acetonitrile (90:10, v/v). The mass spectrometer works with electrospray ionization and multiple reaction monitoring in its negative ion mode, using target ions at [M–H]⁻ m/z 111.9 for Oxo and [M–H]⁻ m/z 117.0 for the IS. The mean standard curve was linear (r=0.9991) over the concentration range of 2.0–200.0 ng/ml and had good back-calculated accuracy and precision. The intra- and inter-day precision were <6.33% and the accuracy was >99.38%. The extraction recovery was >60.26%. The lower limit of quantification achieved with this method was 2.0 ng/ml. This assay method was demonstrated to be accurate, sensitive and simple and was successfully applied to a pharmacokinetic study following single oral administration of a 40-mg S-1 capsule in 12 tumor patients.

In vivo distribution of 5-Fluorouracil after peritumoral implantation using a biodegradable micro-device in tumor-bearing mice

A novel implantable micro-device was used for delivery of 5-Fluorouracil (5-Fu), which was often used in the treatment of various human malignancies. The biodegradable poly(lactic-co-glycolic) acid (PLGA) was used as material. The purpose of this study was to investigate the efficiency of delivery of 5-Fu to the tumor via this delivery system. The distribution characters of the 5-Fu in tumor, plasma, peritumoral tissue, liver and kidney were compared after peritumoral implantation of micro-device and intraperitoneal injection of solution. After administration of micro-device, the 5-Fu was absorbed into the tumor on Day 1, and Cmax (4.14 μg/g) was reached on Day 6. The half life for the elimination was 4.48 d and the AUC was 46.78 μg × d/g. Similar pharmacokinetic behaviors were observed in plasma, peritumoral tissue, kidney and liver, while the Cmax and the AUC of plasma and these tissues were lower than those of tumor. When administered the solution, 5-Fu was rapidly absorbed into plasma, liver, kidney, spleen and tumor, and rapidly cleared from these tissues after 2 or 4 h. And the AUC in tumor of 5-Fu solution was significantly lower than that of the micro-device. These results indicated that 5-Fu loaded biodegradable micro-device offered a relatively high concentration and long-term delivery of the drug to the tumor site.

Phase II tailored S-1 regimen study of first-line chemotherapy in elderly patients with advanced and recurrent non-small cell lung cancer

PURPOSE

We investigated the efficacy and toxicity of a novel oral 5-fluorouracil (5-FU) formulation (S-1), administered according to a tailored dose regimen.

METHODS

S-1 was administered orally for 28 days, followed by 14 days of no treatment, in 23 patients who received a tailored dose of S-1, adjusted on the basis of individual creatinine clearance and body surface area. In 8 of the patients, pharmacokinetic study was performed on the 6 points on 7th day after S-1 administration.

RESULTS

Of the 23 patients enrolled in this study, 2 (8.7 %) had a partial response and 14 (60.9 %) had stable disease. The disease control rate was 69.6 % (16/23) (95 % confidence interval, 50.8-88.4 %). Grade 3/4 hematologic and non-hematologic toxicities were minor. In the pharmacokinetic study group, the maximum plasma concentration (C (max)) and the area under the plasma concentration curve of 5-FU at all 6 points after administration of the tailored S-1 dose regimen were similar to the values reported in a previous study describing cancer patients with normal renal function who received a standard dose of S-1 (80 mg/m(2)/day).

CONCLUSIONS

Our results suggest that tailored S-1 monotherapy is safe and therapeutically useful as first-line treatment for elderly patients with advanced and recurrent non-small cell lung cancer.

Phase I study of two schedules of oral S-1 in combination with fixed doses of oxaliplatin and bevacizumab in patients with advanced solid tumors

BACKGROUND

S-1 is a novel oral agent combining the 5-fluorouracil (FU) prodrug tegafur with gimeracil and oteracil, which inhibit 5-FU degradation by dihydropyrimidine dehydrogenase and phosphorylation within the gastrointestinal tract, respectively. The study was designed to identify the maximum tolerable dose and the dose-limiting toxicities of two schedules of S-1 combined with oxaliplatin and bevacizumab, in advanced solid tumor patients.

METHODS

Schedule A: S-1 was administered orally at 20 mg/m(2) twice daily for 14 consecutive days, escalated by 5 mg/m(2), with fixed-dose intravenous bevacizumab 7.5 mg/kg and oxaliplatin 130 mg/m(2) on day 1 of each 3-week cycle. Schedule B: S-1 was administered at 25 mg/m(2) twice daily for 7 consecutive days, escalated by 5 mg/m(2), with fixed-dose intravenous bevacizumab 5 mg/kg and oxaliplatin 85 mg/m(2) on day 1 of each 2-week cycle.

RESULTS

The maximum tolerated dose and recommended phase II dose of S-1 was 25 mg/m(2) twice daily for 14 days for schedule A and 35 mg/m(2) twice daily for 7 days for schedule B. The most common dose-limiting toxicities were grade 3 diarrhea. Both regimens were well tolerated. No pharmacokinetic interactions between oxaliplatin and S-1 components were observed.

CONCLUSIONS

S-1, oxaliplatin and bevacizumab can be administered with acceptable safety and tolerability and without evidence of pharmacokinetic interactions.

Analysis of anticancer drugs: a review

In the last decades, the number of patients receiving chemotherapy has considerably increased. Given the toxicity of cytotoxic agents to humans (not only for patients but also for healthcare professionals), the development of reliable analytical methods to analyse these compounds became necessary. From the discovery of new substances to patient administration, all pharmaceutical fields are concerned with the analysis of cytotoxic drugs. In this review, the use of methods to analyse cytotoxic agents in various matrices, such as pharmaceutical formulations and biological and environmental samples, is discussed. Thus, an overview of reported analytical methods for the determination of the most commonly used anticancer drugs is given.

Phase I trial of chemoradiotherapy with the combination of S-1 plus cisplatin for patients with unresectable locally advanced squamous cell carcinoma of the head and neck

The aim of the present study was to determine the maximum tolerated dose (MTD) of S-1 in combination with chemoradiotherapy (CRT) in patients with unresectable locally advanced squamous cell carcinoma of the head and neck, and evaluate the difference in pharmacokinetics of S-1 when administered as a suspension via a feeding tube or orally as a capsule. Chemotherapy consisted of administration of S-1 twice daily on days 1-14 at escalating doses of 40, 60 and 80 mg/m(2) per day, and cisplatin at 20 mg/m(2) per day on days 8-11, repeated twice at a 5-week interval. Single daily radiation of 70 Gy in 35 fractions was given concurrently starting on day 1. Two additional cycles of chemotherapy were planned after the completion of CRT. Before starting CRT, each patient received S-1 via two different administration methods. Twenty-two patients were enrolled. The MTD was reached with S-1 at 80 mg/m(2) per day, with two of six patients experiencing febrile neutropenia lasting more than 4 days. All four patients whose creatinine clearance was decreased to <60 mL/min after the first cycle of chemotherapy developed febrile neutropenia lasting more than 4 days. Pharmacokinetic analysis revealed that the 5-fluorouracil area under the curve did not significantly differ by the administration route. S-1 at 60 mg/m(2) per day for 14 days was well tolerated with concurrent CRT. Administration of S-1 as a suspension or by whole capsule can be considered therapeutically interchangeable. Although these data are preliminary, activity was highly promising, and this approach warrants further investigation.

Phase I/II study of the pharmacokinetics, safety and efficacy of S-1 in patients with advanced hepatocellular carcinoma

S-1, an oral fluoropyrimidine derivative, has been shown to be clinically effective against various solid tumors, and preclinical studies have demonstrated activity against hepatocellular carcinoma. We conducted a phase I/II study in patients with advanced hepatocellular carcinoma to examine the pharmacokinetics, recommended dose, safety and efficacy of S-1. In phase I, the administered dose of S-1 was approximately 64 mg/m(2) per day in three patients (level 1) and approximately 80 mg/m(2) per day in six patients (level 2). There was no dose-limiting toxicity at level 1, but two patients had dose-limiting toxicity at level 2 (grade 3 anorexia and grade 2 rash requiring eight or more consecutive days of rest). The recommended dose was finally estimated to be 80 mg/m(2) per day. There were no significant differences in the pharmacokinetics of S-1 between patients with Child-Pugh A and those with B. In phase II, five of 23 patients (21.7%) had partial responses. The median progression-free survival and overall survival were 3.7 and 16.6 months, respectively. The most common toxicities of grade 3 or 4 were elevated serum aspartate aminotransferase levels, hypochromia and thrombocytopenia. In conclusion, S-1 showed an acceptable toxicity profile and promising antitumor activity for hepatocellular carcinoma, warranting further evaluation in randomized clinical trials.

A review of analytical methods for the determination of 5-fluorouracil in biological matrices

5-Fluorouracil (5-FU) is a cytostatic agent that has been widely used in the treatment of various solid tumours for more than 20 years, and is still considered to be among the most active antineoplastic agents in advanced colorectal cancer and malignancies of the head and neck. A large number of non-chromatographic and chromatographic methods for the quantitation of 5-FU, related prodrugs and their metabolites in biological matrices have been developed in the last 30 years to support preclinical and clinical studies. However, 5-FU monitoring has not been widely used, at least not in the USA, and certainly not outside the clinical research setting, given the absence of simple, fast and inexpensive testing methods for 5-FU monitoring. Recent developments with testing based on liquid chromatography-tandem mass spectrometry and a nanoparticle antibody-based immunoassay may facilitate routine monitoring of 5-FU in daily clinical practice. In this review the advantages and disadvantages of the bioanalytical methods developed and used for 5-FU, its metabolites and related prodrugs are discussed.

Determination of tegafur, 5-fluorouracil, gimeracil and oxonic acid in human plasma using liquid chromatography-tandem mass spectrometry

S-1 is an oral anticancer drug, which consists of tegafur (FT), gimeracil (CDHP) and potassium oxonate (Oxo) at a molar ratio of 1:0.4:1. Among these, tegafur is a prodrug, and is rapidly metabolized to the active drug, 5-fluorouracil (5-FU), in vivo. To evaluate the pharmacokinetics of S-1 in patients, LC-MS/MS methods were developed and validated for determination of FT, 5-FU, CDHP and Oxo in human plasma. FT, 5-FU and CDHP were extracted from plasma following protein precipitation, separated on a Synergi Hydro-RP column and simultaneously quantified by LC-MS/MS. The mobile phase consisted of methanol-water-ammonia-acetic acid (27:73:0.0018:0.018, v/v/v/v). The mass spectrometer was operated in negative mode using electrospray ionization. The calibration curves were linear in the range of 12.0-3000ng/mL for FT, and 2.00-500ng/mL for 5-FU and CDHP. The accuracy ranged from 93.1% to 110.7% and the precision ranged from 2.4% to 14.6% for each analyte. To determine Oxo in human plasma, an LC-MS/MS method employing pre-column derivatization was developed and validated. 4-Bromomethyl-7-methoxycoumarin was chosen as the derivatization reagent and [(13)C(2),(15)N(3)]-Oxo was used as the internal standard. The MS/MS detection was operated in positive mode using an APCI source. The calibration range was 2.00-150ng/mL. The accuracy and precision were within 95.9-99.1% and 4.4-10.0%, respectively. The validated methods were successfully applied to characterize the pharmacokinetic profiles of FT, 5-FU, CDHP and Oxo following oral administration of 60mg S-1 tablets to patients with solid gastrointestinal tract tumors.

Effects of a low-fat meal on the oral bioavailability of UFT and leucovorin in patients with colorectal cancer

BACKGROUND

UFT is composed of tegafur, a prodrug of 5-fluorouracil, and uracil, at a fixed ratio of 1: 4. UFT is widely used with leucovorin as adjuvant chemotherapy in patients with colon cancer. As reported, UFT/leucovorin should not be taken simultaneously with food because a high fat content will reduce the systemic exposure to the active cytotoxic moiety of UFT. In this single-dose, randomized, two-way crossover study, we investigated the effects of a low-fat Japanese meal on the pharmacokinetics and oral bioavailability of UFT (2 x 100-mg capsules; dose in terms of tegafur) and leucovorin (1 x 25-mg tablet).

METHODS

Patients (n = 12) were randomly assigned to receive both drugs after an overnight fast or 5 min after eating a standard Japanese breakfast (641 kcal), with a 3-day washout period between treatments. Pharmacokinetics (n = 12) were determined for tegafur, 5-fluorouracil, uracil, leucovorin, and 5-methyltetrahydrofolate (an active metabolite of leucovorin).

RESULTS

For 5-fluorouracil pharmacokinetics, the maximum plasma concentration and the area under the curve were reduced by 73.7% and 47.4%, respectively, when UFT was taken postprandially, and the maximum plasma concentration and the area under the curve for uracil were reduced by 84.1% and 68.9%, respectively, compared with dosing on an empty stomach. These decreases in the systemic exposure to 5-fluorouracil were quite marked and may have an impact on its antitumor effect.

CONCLUSION

A low-fat meal affects the pharmacokinetics of UFT similarly to a high-fat meal.

Can the 2-(13)C-uracil breath test be used to predict the effect of the antitumor drug S-1?

PURPOSE

S-1 is an oral anticancer drug containing tegafur (FT), a pro-drug of fluorouracil, combined with two modulators, 5-chloro-2,4-dihydroxypyridine and potassium oxonate (Oxo), at a molar ratio of 1:0.4:1. CYP2A6 genetic polymorphism and dihydropyrimidine dehydrogenase (DPD) inhibition are important for the antitumor effect of S-1. Exploiting the usefulness of the 2-(13)C-uracil breath test (UrBT) as an indicator of DPD activity, we examined whether the results of CYP2A6 genetic polymorphism analysis and UrBT could be used to predict the antitumor effect of S-1.

METHODS

Thirty-four patients with advanced or recurrent cancer (15, 16 and 3 with gastric, colorectal and pancreatic cancer, respectively) were orally administered 40 mg/m(2) S-1 twice daily in the morning and evening. Eighteen patients with a complete response (CR)/partial response (PR) (2 with CR, 16 with PR) and 16 with progressive disease (PD) were compared with respect to CYP2A6 genetic polymorphisms (1- vs. 2-allele mutation), UrBT results, and plasma FT and 5-fluorouracil levels at 3 h after S-1 ingestion in the morning.

RESULTS

On multivariate analysis between the CR/PR and PD groups, only the UrBT results was an independent factor of CR/PR to S-1 (95% CI 1.02-1.10).

CONCLUSION

These results suggest that the anticancer effect of S-1 can be predicted by performing UrBT 3 h after the initial oral S-1 administration.

Two dosages of oral fluoropyrimidine S-1 of 35 and 40 mg/m2 bid: comparison of the pharmacokinetic profiles in Korean patients with advanced gastric cancer

Objective

In this study, we compared the pharmacokinetic profiles of 5-fluorouracil (5-FU), tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP) and potassium oxonate (Oxo) after administration of S-1 at 35 or 40 mg/m² bid for 28 consecutive days, in Cycles 1 and 3, in patients with advanced gastric cancer.

Methods

Three patients were enrolled for each dosage. S-1 dosage was assigned based on body surface area (BSA), which is different from the Japanese dosing system. The median daily dose per BSA was 76 mg/m², ranging from 70 to 88 mg/m².

Results

Plasma levels of 5-FU, tegafur, CDHP and Oxo at 4 h post-dose reached steady-state on day 8. The estimated steady-state level was dependent on S-1 dosage. There were no intercyclic differences of pre-dose and 4 h post-dose levels between Cycles 1 and 3, implying no cumulative effect of S-1 was shown probably due to 2-week drug-resting period. Pharmacokinetic profiles on day 28 were similar to previous Japanese report. C_max and AUC_{0–48 h} values of each S-1 component increased depending on S-1 dosage. Pharmacokinetic parameters were not correlated with tumor response or toxicity.

Conclusions

We suggest that these pharmacokinetic profiles of Asian population could provide a basis for schedule optimization and for additional studies on interaction with other antitumor drugs.

Phase II study of S-1 as first-line treatment for elderly patients over 75 years of age with advanced gastric cancer: the Tokyo Cooperative Oncology Group study

PURPOSE

This prospective multicenter phase II study was carried out to investigate the efficacy, safety and pharmacokinetics of S-1 monotherapy in elderly patients over 75 years of age, with unresectable advanced or recurrent gastric cancer.

METHODS

Patients had measurable or evaluable lesions according to the Japanese Classification of Gastric Carcinoma. S-1 (25-60 mg determined by the body surface area and creatinine clearance) was given orally, twice daily. A course of treatment consisted of 4-week administration followed by a 2-week rest period, and the patients received repeated courses.

RESULTS

Thirty-three patients were enrolled. Pharmacokinetics of S-1 was studied in six patients, and the maximum plasma concentrations of respective metabolites after S-1 administration were found to be similar to those reported for younger cancer patients. The overall response rate in 33 patients was 21.2% (95% CI, 10.7-37.8%), and median progression-free survival was 3.9 months, with a median overall survival of 15.7 months. Frequently noted adverse events include leukopenia, neutropenia, anemia, anorexia, and fatigue. As for serious adverse events, relatively higher frequencies of anemia (9%) and anorexia (12%) of grade 3 severity were found, but there were no grade 4 episodes.

CONCLUSIONS

The results suggest that S-1 monotherapy is safe and useful for elderly patients with unresectable advanced or recurrent gastric cancer when the dose is selected with caution, taking into account renal function.

CYP2A6 and the plasma level of 5-chloro-2, 4-dihydroxypyridine are determinants of the pharmacokinetic variability of tegafur and 5-fluorouracil, respectively, in Japanese patients with cancer given S-1

S-1 is an oral anticancer agent composed of tegafur (FT), 5-chloro-2,4-dihydroxypyridine (CDHP), and potassium oxonate. CDHP is added to prevent degradation of 5-fluorouracil (5-FU) by inhibiting dihydropyrimidine dehydrogenase. CYP2A6 is involved in the biotransformation of FT to 5-FU. Thus, we prospectively analyzed the effects of the CYP2A6 genotype, plasma level of CDHP, and patient characteristics on the pharmacokinetic (PK) variability of FT and 5-FU. Fifty-four Japanese patients with metastatic or recurrent cancers who received S-1 were enrolled. The CYP2A6 polymorphisms (*4A, *7, and *9) with deficient or reduced activity were analyzed. All subjects were classified into three groups according to their CYP2A6 genotype: wild type (*1/*1), one-variant allele (*1/any), or two-variant alleles (combination other than *1). The PK of FT, 5-FU, and CDHP were measured on day 1 of treatment. Multivariate regression analysis revealed that oral clearance of FT was associated with the CYP2A6 genotype (analysis of variance [ANOVA], P = 0.000838). The oral clearance of FT seen in patients with the two-variant alleles was significantly lower than those in wild type and the one-variant allele (95% confidence intervals 0.75-2.41 and 0.41-1.82, respectively; Tukey-Kramer test). The area under the time-concentration curve (AUC) of 5-FU was significantly correlated with the AUC of CDHP (ANOVA, P = 0.00126). The AUC of 5-FU and CDHP were inversely correlated with creatinine clearance (ANOVA, P = 0.0164 and P = 0.000762, respectively). Although the CYP2A6 variants are the cause of the PK variability of FT, the AUC of CDHP affected by renal function is the key determinant of the variability in the PK of 5-FU.

The CYP2A6*4 allele is determinant of S-1 pharmacokinetics in Japanese patients with non-small-cell lung cancer

S-1 is an oral fluorouracil anticancer drug that contains the 5-FU prodrug tegafur. Tegafur has been shown to be converted enzymatically to 5-FU to exert its antitumor effect, and this conversion is principally catalyzed by CYP2A6. Forty-six non-small-cell lung cancer patients were enrolled. The frequencies of the CYP2A6*4C, CYP2A6*7, and CYP2A6*9 alleles were 17.4, 19.6, and 15.2%, respectively. In the S-1 pharmacokinetic analysis, the area under the concentration-time curve from 0 to 10 h (AUC(0-10)) ratios of 5-FU/tegafur showed large interindividual variabilities, ranging from 5.14 to 112.6. The AUC(0-10) for tegafur was 1.5-fold higher in patients with the CYP2A6*4C allele than in patients without the CYP2A6*4C allele P < 0.05). Furthermore, patients with the CYP2A6*4C allele had a significantly lower maximum plasma concentration (102.6 +/- 32.9 ng/ml) for 5-FU than patients without the CYP2A6*4C allele (157.0 +/- 65.5 ng/ml, P < 0.05). Genotyping of CYP2A6 polymorphisms may provide vital information for effective cancer therapy using S-1.

Quantitation of 5-fluorouracil (5-FU) in human plasma by liquid chromatography/electrospray ionization tandem mass spectrometry

5-Fluorouracil (5-FU) has long had a place in the treatment of many malignancies. 5-FU plasma concentrations have been correlated with toxicity and efficacy, and therapeutic drug monitoring has been reported to result in an improved response/toxicity balance. We report validation, according to FDA guidelines, of a hydrophilic interaction chromatography (HILIC) liquid chromatography/tandem mass spectrometry (LC/MS/MS) assay for the sensitive, accurate and precise quantitation of 5-FU in human plasma. The assay employed an isotopically labeled 5-FU internal standard and ethyl acetate extraction. Separation was achieved with an amino column and an isocratic mobile phase of 0.1% formic acid in acetonitrile/water (97:3, v/v), followed by a wash. Detection consisted of electrospray, negative-mode ionization tandem mass spectrometry in the multiple reaction monitoring (MRM) mode. The accuracy was 96.0-102.2%, and precision was 2.1-7.5% in the concentration range of 10-10 000 ng/mL. Recovery from plasma was 46.0-72.6%, and ion suppression was 9.8-25.7%. Plasma freeze/thaw stability was 87.5-104.3%, and stability for 4 h at room temperature was 98.7-100.0%. This assay is currently being used to quantitate 5-FU in human plasma samples.

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

We studied whether total gastrectomy for gastric cancer would affect the pharmacokinetics of 5-fluorouracil (5-FU) and its degradation products, such as dihydrouracil (FUH(2)) and alpha-fluoro-beta-alanine (FBAL), after oral administration of the fluorouracil derivative S-1, composed of tegafur, 5-chloro-2,4-dihydroxypyridine (CDHP; a dihydropyrimidine dehydrogenase inhibitor) and potassium oxonate. Blood and urine samples were obtained, both preoperatively and at least 2 weeks postoperatively, from six patients with advanced gastric cancers who were undergoing total gastrectomy. Plasma levels of tegafur, 5-FU, CDHP, potassium oxonate, FUH(2) and FBAL were measured prior to and at 1, 2, 4, 6 and 10 h after oral administration of 40 mg/m(2) S-1. The total amounts of 5-FU, FUH(2) and FBAL excreted into urine during the 24-h period after S-1 administration were also measured. Total gastrectomy significantly increased the maximum concentration and the area under the curve until 10 h after administration (AUC(1-10h)) of plasma 5-FU. The plasma AUC(1-10h) of CDHP was significantly higher than the preoperative value. In terms of clinical efficacy, the higher AUC(1-10h) of 5-FU after total gastrectomy may be beneficial to S-1 administered as adjuvant chemotherapy, and might be caused by the higher postoperative AUC(1-10h) of CDHP relative to preoperative values. However, the dose of S-1 for patients who have undergone total gastrectomy might be diminished to avoid severe adverse events and to continue the treatment for a long period.

Multi‐Institutional Phase II Study of S‐1 Monotherapy in Advanced Gastric Cancer with Pharmacokinetic and Pharmacogenomic Evaluations

This study describes the first phase II study of S-1, a novel oral fluoropyrimidine, in a non-Japanese Asian population with advanced gastric cancer. S-1 was administered twice daily for 28 days every 6 weeks. A pharmacokinetic study was performed on day 28 of cycles 1 and 3. Genomic DNA from peripheral mononuclear cells was analyzed using a cDNA microarray-based comparative genomic hybridization (CGH) method. Thirty-one patients were initially given a dose of 35 mg/m(2) twice daily (bid) (group 1); then, the protocol was amended by increasing the dose to 40 mg/m(2) bid for an additional 31 patients (group 2) because of good tolerability to S-1. The overall response rate was 19.3% (95% confidence interval, 9.2%-29.5%). Over a median follow-up duration of 265 days, the median time to progression and overall survival time were 126 and 264 days, respectively. The 1-year survival rate was 34%. There was no grade 4 toxicity and the major adverse event was anemia. Pharmacokinetic parameters were similar to those of the previous Japanese reports. Microarray CGH identified 18 genes with copy number changes that were associated with hemoglobin reduction with S-1 treatment. A logistic regression analysis, integrating one clinical parameter (initial hemoglobin level) combined with three genetic copy number variations (HIST1H2BL, C10orf127, and XPNPEP2), provided a predictive model for the development of severe hemoglobin reduction. In conclusion, this study showed the feasibility of using S-1 at 35 mg/m(2) bid in gastric cancer. We suggest that the pharmacogenomic markers identified in this study may be potential candidates for predicting anemia after S-1 treatment.

Effect of gastrectomy on the pharmacokinetics of S-1, an oral fluoropyrimidine, in resectable gastric cancer patients

PURPOSE

The effect of gastrectomy on pharmacokinetics after S-1 administration was investigated.

PATIENTS AND METHODS

A dose of 40 mg/m(2) of S-1 was administered orally twice daily for 7 days (80 mg/m(2)/day) preoperatively in ten patients with resectable gastric cancer, and the same dose of S-1 was administered for 28 consecutive days after gastrectomy. Plasma concentrations of tegafur, gimeracil, and oteracil potassium, all the components of S-1, and 5-FU were measured on pre- and postoperative days. Concentrations of 5-FU in tumor and normal tissues were also determined.

RESULTS

At day 4 from the initial preoperative administration of S-1, the AUC of 5-FU was 1,055 +/- 304 ng h/ml. At day 18, day 28, and day 42 after gastrectomy, it was 1,012 +/- 331, 1,070 +/- 403, and 946 +/- 226 ng h/ml, respectively. No significant differences for plasma 5-FU were observed between pre- and postoperative days. In the resected tumor tissues, concentrations of 5-FU were 242 +/- 83 ng/g around 4.5 h and 91.7 +/- 37.0 ng/g around 20 h after the final administration, respectively.

CONCLUSION

Gastrectomy does not affect on pharmacokinetics of 5-FU derived from S-1 regardless of partial or total gastrectomy, indicating that S-1 can be a useful drug in postoperative adjuvant chemotherapy for gastric cancer.

Phase I and pharmacokinetic study of S-1 administered for 14 days in a 21-day cycle in patients with advanced upper gastrointestinal cancer

PURPOSE

S-1 is a novel oral fluoropyrimidine that combines tegafur with CDHP and oxonic acid. To decrease the incidence of late onset, severe diarrhea observed in a previous study, a phase I study was conducted to determine the maximum tolerated dose (MTD) of S-1 utilizing a 14-day schedule, repeated every 21 days, in patients with chemotherapy-refractory upper gastrointestinal malignancies.

METHODS

S-1 was administered orally, twice-daily, at an initial dose level of 30 mg/m2/dose; doses were escalated by 5 mg/m2 at each level. A minimum of three patients were enrolled at each dose level. S-1 toxicity, antitumor activity, and pharmacokinetics were assessed. The MTD was based on the dose limiting toxicity (DLT) during the first treatment cycle.

RESULTS

At 30 mg/m2 no DLT was observed in the first three evaluable patients. Two of the first three patients at the 35 mg/m2 dose level developed DLTs (grade 3 rash and dehydration). An additional nine patients were subsequently treated at 30 mg/m2 without DLT and this dose was established as the MTD. Common toxicities at 30 mg/m2 included diarrhea, nausea, skin rash, anorexia, and fatigue. No grade 4 toxicities were observed. One partial response was seen in a patient with gemcitabine-refractory pancreatic adenocarcinoma and ten patients with pancreatic, gastric, or gallbladder carcinomas achieved stable disease as their best response to therapy. The AUC(0-8) of 5-FU at the 30 and 35 mg/m2 dose levels were 875 +/- 212 and 894 +/- 151 h ng/ml, respectively.

CONCLUSIONS

In a 14-day dosing schedule, the MTD of S-1 was 30 mg/m2 and preliminary evidence of antitumor activity was seen in a North American population with refractory upper gastrointestinal malignancies.

Phase I pharmacokinetic study of S-1 plus cisplatin in patients with advanced gastric carcinoma

PURPOSE

The conversion rate of tegafur (a component of S-1) to fluorouracil (FU) differs in Asians and whites because of polymorphic differences in the CYP2A6 gene. S-1 with cisplatin is considered highly active in Japanese gastric cancer patients. Therefore, we initiated a phase I pharmacokinetic study of this combination in our gastric cancer patients.

PATIENTS AND METHODS

Patients received cisplatin intravenously on day 1 and S-1 orally, twice daily, on days 1 to 21 every 28 days. At level 1, the S-1 dose was 25 mg/m2/dose (50 mg/m2/d), but it was increased by 5 mg/m2/dose for the next level. Cisplatin was administered at 75 mg/m2 (for levels 1 and 2) but was then reduced to 60 mg/m2 (level 1A). At every level, a cohort of three patients, which could be expanded to six patients, was studied. Maximum-tolerated dose (MTD) was determined based on the dose-limiting toxicity (DLT) in the first cycle. Patients with histologic proof of gastric adenocarcinoma and near-normal organ function were studied.

RESULTS

Sixteen patients were enrolled. No DLTs occurred at level 1. However, DLTs occurred at levels 2 and 1A. The area under the curve for FU correlated significantly with DLT (P = .006) and grade 3 to 4 diarrhea (P = .004). Six partial responses were confirmed, including three at the MTD.

CONCLUSION

At the established MTD of S-1 plus cisplatin, the S-1 dose (50 mg/m2/d for 21 days) is lower in our study than in the Japanese study (80 mg/m2/d for 21 days). A multi-institutional phase II study of this active combination is currently accruing patients.

An early phase II study of S-1 in patients with metastatic pancreatic cancer

OBJECTIVE

The aim of this study was to evaluate the efficacy and toxicity of S-1 in patients with metastatic pancreatic cancer.

METHODS

Patients were required to have a histological diagnosis of pancreatic adenocarcinoma with measurable metastatic lesions, and no prior chemotherapy. S-1 was administered orally at 40 mg/m2 twice daily for 28 days with a rest period of 14 days as one course. Administration was repeated until the appearance of disease progression or unacceptable toxicity. A pharmacokinetic study was done on day 1 in the initial 8 patients.

RESULTS

Nineteen patients were entered into this study. Four patients (21.1%) achieved a partial response with a 95% confidence interval of 6.1-45.6%. No change was noted in 10 patients (52.6%), and progressive disease in 5 patients (26.3%). The median survival time was 5.6 months with a one-year survival rate of 15.8%. The major adverse events were gastrointestinal toxicities such as nausea and anorexia, though most of them were tolerable and reversible. There were no large differences in the pharmacokinetic parameters of S-1 in patients with pancreatic cancer and those in patients with other cancers.

CONCLUSION

S-1 is active and tolerated in patients with metastatic pancreatic cancer, which will be confirmed in the following large-scale phase II study.

Hydrophilic interaction liquid chromatography–APCI–mass spectrometry determination of 5-fluorouracil in plasma and tissues

A simple and fast analytical method using hydrophilic interaction liquid chromatography (HILIC) coupled with mass spectrometry was developed to analyse 5-fluorouracil (5-FU) in plasma and tissues. The HILIC system overcomes problems reported in obtaining satisfactory retention of 5-FU with other types of HPLC systems. After addition of internal standard (IS) (5-Chlorouracil (5-CU)), plasma proteins were precipitated with acetonitrile, and tissue samples homogenised with a micro-dismembrator. The analysis was performed using a polymer-based column (Ashaipak NH2) and the compounds were eluted under gradient conditions at 1 ml/min using a mobile phase containing a mixture of ammonium formate and acetonitrile. MS detection used a API 4000 mass spectrometry with heated nebulizer source and multiple reaction monitoring operated in the negative ion mode. The mass transitions of 5-FU and its internal standard were 129 m/z-->42m/z and 145 m/z-->42 m/z, respectively. The lower limits of quantitation in plasma and tissues were about 5 ng/ml and 10 ng/g, respectively, using 25 microl of plasma and 50mg of tissue. Good linearity, accuracy and precision were obtained in all matrices tested. The suitability and robustness of the method for in vivo samples were confirmed by analysis of mouse plasma, muscle and tumour from animals dosed with 5-FU.

Phase II study of S-1 in patients with advanced biliary tract cancer

The aim of this study was to investigate the efficacy and safety of an oral fluoropyrimidine derivative, S-1, in patients with advanced biliary tract cancer. Patients with pathologically confirmed advanced biliary tract cancer, a measurable lesion, and no history of radiotherapy or chemotherapy were enrolled. S-1 was administered orally (40 mg m(-2) b.i.d.) for 28 days, followed by a 14-day rest period. A pharmacokinetic study was performed on day 1 in the initial eight patients. In all, 19 consecutive eligible patients were enrolled in the study between July 2000 and January 2002. The site of the primary tumour was the gallbladder (n=16), the extrahepatic bile ducts (n=2), and the ampulla of Vater (n=1). A median of two courses of treatment (range, 1-12) was administered. Four patients achieved a partial response, giving an overall response rate of 21.1%. The median time-to-progression and median overall survival period were 3.7 and 8.3 months, respectively. Although grade 3 anorexia and fatigue occurred in two patients each (10.5%), no grade 4 toxicities were observed. The pharmacokinetic parameters after a single oral administration of S-1 were similar to those of patients with other cancers. S-1 exhibits definite antitumour activity and is well tolerated in patients with advanced biliary tract cancer.

Phase I and Pharmacokinetic Study of the Oral Fluoropyrimidine S-1 on a Once-Daily-for-28-Day Schedule in Patients with Advanced Malignancies

PURPOSE

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.

EXPERIMENTAL DESIGN

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.

RESULTS

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.

CONCLUSIONS

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.

Comparison of the pharmacokinetics of S-1, an oral anticancer agent, in Western and Japanese patients

OBJECTIVE

S-1 is an oral anticancer agent combining tegafur (FT), a prodrug of 5-fluorouracil (5-FU), with potassium oxonate (oteracil) and gimeracil (CDHP) respectively to mitigate gastrointestinal toxicity and increase the half-life of 5-FU. This article presents a population pharmacokinetic analysis of these four compounds in Western cancer patients. The second objective was to compare the pharmacokinetics of S-1 in Western and Japanese patients.

METHODS

A single dose (25-45 mg/m2) of S-1 was administered to 60 patients. In each patient, 6 concentrations of FT, 5-FU, oteracil and CDHP were measured over 24 hr. Using NONMEM, oteracil and CDHP were analyzed separately, and the individual estimates of CDHP parameters were included in the joint analysis of FT and 5-FU. We used validation techniques to assess differences between the two populations, and finally we compared the exposures in Western and Japanese patients using simulations.

RESULTS

A compartmental model describing the PK of the 4 compounds was developed. The influence of CDHP on the elimination of 5-FU was well described by an enzymatic inhibition model. The model provided a good fit for all compounds. The pharmacokinetics for 5-FU and oteracil were similar between Western and Japanese patients, but apparent differences in exposure to 5-FU resulted from different total doses due to different body sizes.

Sensitive liquid chromatographic assay for the simultaneous determination of 5-fluorouracil and its prodrug, tegafur, in beagle dog plasma

A high-performance liquid chromatographic (HPLC) method has been developed for the simultaneous determination of 5-fluorouracil (5-FU) and its prodrug, tegafur (TF), in dog plasma. 5-FU, the internal standard, 5-bromouracil, and TF were separated on a C18 Spherisorb ODS2 column using isocratic elution with retention times of 4.4, 8.0 and 21.2 min, respectively. Detection by UV absorption at 260 nm gave a limit of quantitation of 4 microg/l for 5-FU in plasma. Calibration curves for 5-FU and TF were linear over the ranges of 4-160 microg/l and 0.48-19.2 mg/l, respectively. Intra- and inter-day precision over these concentration ranges were <10.9 and <13.6% for 5-FU and TF, respectively, with good accuracy for both compounds. The method was successfully applied to define plasma concentration-time curves of TF and 5-FU in dogs administered a single oral dose containing TF (100 mg) and uracil (224 mg).

Experimental study to evaluate the usefulness of S-1 in a model of peritoneal dissemination of gastric cancer

BACKGROUND

Favorable results have been reported for the novel oral anticancer agent S-1 (TS-1) in clinical studies of advanced gastric cancer with peritoneal dissemination. In the present study we assessed its pharmacokinetics, inhibitory effects, and effect on survival time in an animal model.

METHODS

A model of peritoneal dissemination was created by intraperitoneally implanting 4-week-old female BALBc nu/nu mice with the human gastric cancer cell line MKN-45 after transfection with a fluorescent protein-expressing vector. Pharmacokinetics were investigated by measuring intratumor, peritoneal lining, and blood concentrations after the administration of S-1 and fluorouracil (5-FU). The effect of S-1 on survival time was also assessed, by administration once daily to seven animals per group, starting on day 7 after implantation, and survival time was compared with that of an untreated control group. The inhibitory effect of S-1 on peritoneal dissemination was evaluated by killing mice at the start of administration, and 1 and 3 weeks after the start of administration, and examining them for the presence of peritoneal dissemination under a fluorescence stereomicroscope.

RESULTS

Maintenance of high 5-FU concentrations in the intraperitoneal tumors was confirmed in the S-1 group, and survival time was prolonged without any decrease in oral food intake or body weight.

CONCLUSION

Assessment in a model of peritoneal dissemination of gastric cancer showed that the novel oral anticancer agent S-1 was effective against peritoneal dissemination, and that it improved the survival rate.

Plasma concentrations of 5-fluorouracil and F-beta-alanine following oral administration of S-1, a dihydropyrimidine dehydrogenase inhibitory fluoropyrimidine, as compared with protracted venous infusion of 5-fluorouracil

The pharmacokinetics and pharmacodynamics of oral S-1, a dihydropyrimidine dehydrogenase (DPD) inhibitory fluoropyrimidine, were compared with those of protracted venous infusion (PVI) of 5-fluorouracil (5-FU). In all, 10 patients with gastric cancer received PVI of 5-FU at a dose of 250 mg m(-2) day(-1) for 5 days. After a washout period of 9 days, the patients received two divided doses daily for 28 days. S-1 was administered orally at about 0900 and 1900 hours. The daily dose of S-1 in terms of tegafur was 80 mg day(-1) in patients with a body surface area (BSA) of <1.25 m(2), 100 mg day(-1) in those with a BSA of >or=1.25 m(2) to <1.5 m(2), and 120 mg day(-1) in those with a BSA of >or=1.5 m(2). Plasma concentrations of 5-FU and F-beta-alanine (FBAL) were measured for pharmacokinetic analysis, and the plasma uracil concentration was monitored as a surrogate marker of DPD inhibition (pharmacodynamic analysis) in the same patients on days 1-5 of PVI of 5-FU and on days 1-5 of oral S-1. The area under the curve (AUC(0-10 h)) of 5-FU on day 5 was 728+/-113 ng h ml(-1) for PVI of 5-FU and 1364+/-374 ng h ml(-1) for S-1. The median 5-FU PVI : S-1 ratio of the AUC(0-10 h) of 5-FU was 1.9. The AUC(0-10 h) of FBAL on day 5 of PVI of 5-FU was 9465+/-3225 ng h ml(-1), AUC(0-10 h), as compared with 1725+/-605 ng h ml(-1) on day 5 of S-1 treatment. The AUC(0-10 h) of uracil on day 5 was 252+/-60 ng h ml(-1) with PVI of 5-FU and 12 582+/-3060 ng h ml(-1) with S-1. The AUC(0-10 h) of FBAL was markedly lower and plasma uracil concentrations were significantly higher for S-1 than for PVI of 5-FU, clearly demonstrating the effect of DPD inhibition.

Pharmacokinetics of S-1, an oral formulation of ftorafur, oxonic acid and 5-chloro-2,4-dihydroxypyridine (molar ratio 1:0.4:1) in patients with solid tumors

S-1 is an oral formulation of ftorafur (FT), oxonic acid and 5-chloro-2,4-dihydroxypyridine (CDHP) at a molar ratio of 1:0.4:1. FT is a 5-fluorouracil (5-FU) prodrug, CDHP is a dihydropyrimidine dehydrogenase (DPD) inhibitor and oxonic acid is an inhibitor of 5-FU phosphoribosylation in the gastrointestinal mucosa and was included to prevent gastrointestinal toxicity. We determined the pharmacokinetics of S-1 in 28 patients at doses of 25, 35, 40 and 45 mg/m(2). The plasma C(max) values of FT, 5-FU, oxonic acid and CDHP increased dose-dependently and after 1-2 h were in the ranges 5.8-13 microM, 0.4-2.4 microM, 0.026-1.337 microM, and 1.1-3.6 microM, respectively. Uracil levels, indicative of DPD inhibition, also increased dose-dependently from basal levels of 0.03-0.25 microM to 3.6-9.4 microM after 2-4 h, and 0.09-0.9 microM was still present after 24 h. The pharmacokinetics of CDHP and uracil were linear over the dose range. The areas under the plasma concentration curves (AUC) for CDHP and uracil were in the ranges 418-1735 and 2281-8627 micromol x min/l, respectively. The t(1/2) values were in the ranges 213-692 and 216-354 min, respectively. Cumulative urinary excretion of FT was predominantly as 5-FU and was 2.2-11.9%; the urinary excretion of both fluoro-beta-alanine and uracil was generally maximal between 6 and 18 h. During 28-day courses with twice-daily S-1 administration, 5-FU and uracil generally increased. Before each intake of S-1, 5-FU varied between 0.5 and 1 microM and uracil was in the micromolar range (up to 7 microM), indicating that effective DPD inhibition was maintained during the course. In a biopsy of an esophageal adenocarcinoma metastasis that had regressed, thymidylate synthase, the target of 5-FU, was inhibited 50%, but increased four- to tenfold after relapse in subsequent biopsies. In conclusion, oral S-1 administration resulted in prolonged exposure to micromolar 5-FU concentrations due to DPD inhibition, and the decrease in uracil levels after 6 h followed the pattern of CDHP and indicates reversible DPD inhibition.