1 University Medical Center, St Radboud Nijmegen, The Netherlands; 2 Wyeth Research, Collegeville, PA, USA; 3 Klinikum Nürnberg, Germany; 4 Wyeth Oncology, Munich, Germany
Received 21 October 2002; revised 16 January 2003; accepted 20 February 2003
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Abstract |
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CCI-779 is a novel ester of the immunosuppressive agent sirolimus that exerts cytostatic effects by the inhibition of the translation of cell-cycle regulatory proteins. We investigated the maximum tolerated dose (MTD) and pharmacokinetics (PK) of CCI-779 in combination with leucovorin (LV) and 5-fluorouracil (5-FU) in patients with advanced solid tumors.
Patients and methods:
Patients were treated with LV at 200 mg/m2 as a 1-h i.v. infusion directly followed by continuous 24-h i.v. infusion of 5-FU, in the first patient at 2000 mg/m2 and in subsequent patients at 2600 mg/m2. CCI-779 was administered directly prior to LV as a 30-min i.v. infusion at a starting dose of 15 mg/m2 beginning at day 8 and escalated in subsequent cohorts of patients. One cycle consisted of six weekly administrations followed by 1 week of rest. Blood samples were drawn to assess PK of CCI-779 as well as its effect on steady-state 5-FU exposures.
Results:
Twenty-eight patients entered the study, the majority having tumor types for which 5-FU is used as a treatment. CCI-779 doses of 15, 25, 45 and 75 mg/m2 were investigated. Skin toxicity (rash) was prominent at all dose levels examined. Stomatitis was the dose-limiting toxicity (DLT) for 75 mg/m2 doses of CCI-779. Subsequently the cohort at 45 mg/m2 was expanded to a total of 15 patients, and at this dose level two treatment-related deaths occurred due to mucositis with bowel perforation. Based on the toxicities observed, it was decided to discontinue the study. Partial responses were observed in three patients with gastrointestinal tumors. No pharmacokinetic interaction between CCI-779 and 5-FU was observed.
Conclusions:
The safety profiles of CCI-779 and 5-FU/LV suggest an overlap of drug-related toxicities, and the administration of these drugs at these doses and schedule resulted in unacceptable toxicity and therefore cannot be recommended. If CCI-779 is to be used in combination with 5-FU/LV, other doses or schedules of administration will need to be explored.
Key words: CCI-779, 5-fluorouracil, pharmacokinetics, phase I study, rapamycin, sirolimus, solid tumors
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Introduction |
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5-Fluorouracil (5-FU) is an antineoplastic antimetabolite which is frequently used as palliative treatment for patients with carcinoma of the colon, rectum, breast, stomach and pancreas. The pharmacokinetics (PK) of 5-FU have been relatively well characterized [12, 13]. Depending on the dose and schedule, its main toxicities are diarrhea, stomatitis and leukopenia. With continuous i.v. infusion, handfoot syndrome is frequently observed.
Based on the hypothesis that cytostatic agents are likely to be more effective with other chemotherapeutic agents in patients with solid tumors, we initiated a phase I study of CCI-779 in combination with 5-FU and leucovorin (LV). The PK of CCI-779 and its major metabolite, sirolimus, are described. In addition, the potential for CCI-779 to influence the disposition of 5-FU is examined.
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Patients and methods |
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Study objectives
The primary objectives of the study were to assess the safety and tolerability of CCI-779 when combined with 5-FU/LV and to identify its maximum tolerated dose (MTD) in this group of patients. The secondary objectives were to determine the PK and clinical efficacy of CCI-779 and 5-FU with this schedule. The protocol allowed the inclusion of additional patients at MTD in order to expand the experience at this dose level.
Treatment
A tunneled central venous catheter for 5-FU infusion was inserted in all patients prior to the start of the study. Treatment was given in the ambulatory setting except for the days of PK sampling. Patients received LV administered at 200 mg/m2 as a 1-h i.v. infusion, directly followed by a continuous 24-h i.v. infusion of 5-FU by ambulatory pump. The first patient at one of the institutions received 5-FU at a dose of 2000 mg/m2 as requested by one of the local review boards. Subsequent patients received 5-FU at 2600 mg/m2, which has been used frequently for the treatment of colorectal cancer [14, 15]. CCI-779 (Wyeth Research, PA, USA) was administered immediately prior to LV as a 30-min i.v. infusion by pump at a starting dose of 15 mg/m2 beginning at day 8 and escalated in subsequent cohorts of three to six patients. The starting dose of CCI-779 was based on preliminary results of a phase I single-agent study in which CCI-779 was administered on a weekly schedule to patients with cancer [4]. The starting dose of 15 mg/m2 was well below (25%) the dose achieved at the time that the single-agent phase I study was simultaneously ongoing, and was neither associated with dose-limiting toxicities nor with National Cancer Institute (NCI) toxicity greater than grade 2.
CCI-779 25 mg/ml ethanolic concentrate was diluted 10-fold using a special PEG (polyethylene glycol)/polysorbate diluent, and was administered protected from light.
One cycle consisted of six weekly administrations followed by 1 week of rest. NCI-common toxicity criteria and World Health Organization (WHO) response criteria were used. Dose-limiting toxicities (DLT) were defined as grade 34 non-hematological toxicity (excluding nausea/vomiting, unless optimal antiemetic treatment was given, and rise in serum triglycerides, if <17 mmol/l and recovery had occurred by the next cycle), grade 4 thrombocytopenia, grade 4 uncomplicated neutropenia ≥5 days, febrile neutropenia, or treatment delay ≥2 weeks due to any toxicity. In the absence of DLT as determined by the evaluation of at least three patients at that dose level and at least a total of 9 weeks of completed treatment with all three drugs, CCI-779 was to be escalated following a modified Fibonacci scheme. Intrapatient dose escalation was not allowed. After the occurrence of DLT at a particular dose level in the first three patients, the cohort was to be expanded to six patients. The MTD was defined as the dose level at which one or two of six patients experienced DLT. Patients were followed weekly for toxicity and every 2 months for response. The dose of 5-FU was to be reduced upon the occurrence of grade 3 (25% reduction) or grade 4 (50% reduction) hematological toxicity and grade 2 (25% reduction) or grade 3 (50% reduction) non-hematological toxicity. The dose of CCI-779 was to be reduced to 33% upon the occurrence of grade 4 hematological toxicity or grade 3 non-hematological toxicity. Patients were to be withdrawn from the study when grade 4 non-hematological toxicity occurred. No prophylactic medication was used except for the administration of clemastine 2 mg i.v. for the prevention of allergic skin reactions beginning with the expanded 45 mg/m2 cohort.
Bioanalytical methodology
During week 1 (5-FU alone) and weeks 2 and 4 (5-FU with CCI-779), venous blood sampling (3 ml per sample) to measure 5-FU in plasma was performed during 5-FU infusion at 0 (pre-dose), 0.5, 1, 1.5, 2, 3, 5.56, 8 and 24 (end of infusion) h. During weeks 2 and 4, venous blood samples (3 ml each for CCI-779 and sirolimus metabolite) were drawn at 0 (pre-dose), 0.25, 0.5 (end of infusion), 1.5, 3.5, 8, 24, 48, 96 and 168 h.
The bioanalytical method used to measure CCI-779 concentrations was performed and validated at Taylor Technology, Inc. (Princeton, NJ, USA). The method employs a liquid chromatography, tandem mass spectrometry (LC/MS/MS) procedure with deuterated internal standard and is validated through the quantitation range of 0.25100 ng/ml using 1 ml of whole blood. During validation, inter- and intra-day variations were <5% coefficient of variation (CV) and biases were <9.4%. At the lower limit of quantitation (0.25 ng/ml), variability was 7.6% and bias was <2.4%. CCI-779 exhibited adequate room-temperature stability in whole blood (25 h at 25°C), in autosampler extracts (66 h at 25°C and 8 days at 80°C), and after three freeze/thaw cycles. Unpublished data from long-term studies indicate that CCI-779 stability in whole blood is adequate when stored at 70°C. In addition, no interference was observed in blank blood or blood spiked with 100 ng/ml of sirolimus.
The bioanalytical method used to measure sirolimus in this study also employs an LC/MS/MS procedure. The method was performed at Taylor Technology, Inc. and validated through the quantitation range of 0.1100 ng/ml using 1 ml of whole blood. Collectively, inter- and intra-day variabilities of quality control samples measured during validation were <12.7% and biases were <11.3%. Sirolimus is stable in whole blood when stored at 70°C.
Concentrations of 5-FU were measured in plasma using a validated GC/MS/MS (gas chromatography, tandem mass spectrometry) assay. The 5-FU assay was performed at Northwest Bioanalytical (NWB; Salt Lake City, UT, USA). The bioanalytical method exhibited a linear range from plasma of 1100 ng/ml. Inter- and intra-assay variability of quality control samples measured during validation were <7% and biases were <13%. 5-FU is stable in plasma when stored at 20°C.
Pharmacokinetic methodology
All PK data analyses were performed by the Department of Clinical Pharmacology and Pharmacokinetics at Wyeth Research. Concentrations of CCI-779, sirolimus and 5-FU were analyzed using a noncompartmental modeling approach [16]. The PK parameters for CCI-779 and sirolimus include peak concentration (Cmax), time to Cmax (tmax), lambda (), terminal half-life (t1/2), area under the curve through infinity (AUC), clearance (Cl), volume of distribution at steady state (Vss) and AUC ratio (week 4/week 2). For sirolimus, the apparent clearance (Cl/fm) and apparent Vss/fm (where fm is the unknown fraction of parent drug metabolized to form sirolimus), and the AUC ratio (sirolimus/CCI-779 and week 4/week 2) were determined. For 5-FU, the average concentration during infusion (Cmean) was also determined. Derivation of the PK parameters was performed using statistical analysis software.
Statistical analysis of PK parameters includes summary representation for the 15, 25, 45 and 75 mg/m2 dose treatments, and an analysis of variance on log-transformed data with dose treatment and patient as statistical factors. In addition, the ratio [test (week 2 or 4)/reference (week 1)] of least-squares geometric means was determined and the corresponding 90% confidence intervals.
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Results |
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Discussion |
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Following i.v. administration, the PK of CCI-779 in whole blood were non-linear and exhibited increasing clearance with increasing dose. This phenomenon is thought to be a result of saturable specific binding of CCI-779 to FKBP in the red blood cell. Sirolimus was a major metabolite, was present early after the start of dose administration, and decreased in an apparently mono-exponential fashion. The longer half-life of sirolimus relative to CCI-779 is an important determinant of the high parent/metabolite ratios observed with CCI-779.
The PK of 5-FU varies according to dose and schedule of administration. Clearance of 5-FU is reported to be much faster with continuous i.v. infusion than with bolus administration. For 24-h infusion and a dose of 20002600 mg/m2, a mean clearance of 8 µM or
7801040 ng/ml has been reported. This is somewhat higher than the values reported herein, but the difference may be accounted for by diurnal increases in exposure not characterized in the present study. Notwithstanding, generally comparable exposures of 5-FU were observed between reference and test treatments, and these exposures were associated with moderate variability.
In conclusion, the administration of CCI-779 and 5-FU at these doses and schedule resulted in unacceptable toxicity. Three clinical responses were observed and these were for tumors for which 5-FU is often used as a treatment so that the contribution of CCI-779 to these responses is unknown. However, CCI-779 has been shown to be generally well-tolerated and antitumor activity in renal cell carcinoma and breast cancer has been observed [5, 6]. Thus, studies to determine the appropriate use of CCI-779 for the treatment of solid tumors need to continue. If CCI-779 is to be used in combination with 5-FU/LV, other doses or schedules of administration will need to be explored.
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Acknowledgements |
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Footnotes |
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References |
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