| 1. |
- de Graan, Anne-Joy M., et al.
(author)
-
A Pharmacogenetic Predictive Model for Paclitaxel Clearance Based on the DMET Platform
- 2013
-
In: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 19:18, s. 5210-5217
-
Journal article (peer-reviewed)abstract
- Purpose: Paclitaxel is used in the treatment of solid tumors and displays high interindividual variation in exposure. Low paclitaxel clearance could lead to increased toxicity during treatment. We present a genetic prediction model identifying patients with low paclitaxel clearance, based on the drug-metabolizing enzyme and transporter (DMET)-platform, capable of detecting 1,936 genetic variants in 225 metabolizing enzyme and drug transporter genes. Experimental Design: In 270 paclitaxel-treated patients, unbound plasma concentrations were determined and pharmacokinetic parameters were estimated from a previously developed population pharmacokinetic model (NONMEM). Patients were divided into a training-and validation set. Genetic variants determined by the DMET platform were selected from the training set to be included in the prediction model when they were associated with low paclitaxel clearance (1 SD below mean clearance) and subsequently tested in the validation set. Results: A genetic prediction model including 14 single-nucleotide polymorphisms (SNP) was developed on the training set. In the validation set, this model yielded a sensitivity of 95%, identifying most patients with low paclitaxel clearance correctly. The positive predictive value of the model was only 22%. The model remained associated with low clearance after multivariate analysis, correcting for age, gender, and hemoglobin levels at baseline (P = 0.02). Conclusions: In this first large-sized application of the DMET-platform for paclitaxel, we identified a 14 SNP model with high sensitivity to identify patients with low paclitaxel clearance. However, due to the low positive predictive value we conclude that genetic variability encoded in the DMET-chip alone does not sufficiently explain paclitaxel clearance.
|
|
| 2. |
- de Graan, Anne-Joy M., et al.
(author)
-
CYP3A4*22 Genotype and Systemic Exposure Affect Paclitaxel-Induced Neurotoxicity
- 2013
-
In: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 19:12, s. 3316-3324
-
Journal article (peer-reviewed)abstract
- Purpose: Paclitaxel is used for the treatment of several solid tumors and displays a high interindividual variation in exposure and toxicity. Neurotoxicity is one of the most prominent side effects of paclitaxel. This study explores potential predictive pharmacokinetic and pharmacogenetic determinants for the onset and severity of neurotoxicity. Experimental Design: In an exploratory cohort of patients (n = 261) treated with paclitaxel, neurotoxicity incidence, and severity, pharmacokinetic parameters and pharmacogenetic variants were determined. Paclitaxel plasma concentrations were measured by high-performance liquid chromatography or liquid chromatography/tandem mass spectrometry, and individual pharmacokinetic parameters were estimated from previously developed population pharmacokinetic models by nonlinear mixed effects modeling. Genetic variants of paclitaxel pharmacokinetics tested were CYP3A4*22, CYP2C8*3, CYP2C8*4, and ABCB1 3435 C>T. The association between CYP3A4*22 and neurotoxicity observed in the exploratory cohort was validated in an independent patient cohort (n = 239). Results: Exposure to paclitaxel ((log)AUC) was correlated with severity of neurotoxicity (P < 0.00001). Female CYP3A4*22 carriers were at increased risk of developing neurotoxicity (P = 0.043) in the exploratory cohort. CYP3A4*22 carrier status itself was not associated with pharmacokinetic parameters (CL, AUC, C-max, or T->0.05) of paclitaxel in males or females. Other genetic variants displayed no association with neurotoxicity. In the subsequent independent validation cohort, CYP3A4*22 carriers were at risk of developing grade 3 neurotoxicity (OR = 19.1; P = 0.001). Conclusions: Paclitaxel exposure showed a relationship with the severity of paclitaxel-induced neurotoxicity. In this study, female CYP3A4*22 carriers had increased risk of developing severe neurotoxicity during paclitaxel therapy. These observations may guide future individualization of paclitaxel treatment.
|
|
| 3. |
- de Graan, Anne-Joy M., et al.
(author)
-
Influence of Smoking on the Pharmacokinetics and Toxicity Profiles of Taxane Therapy
- 2012
-
In: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 18:16, s. 4425-4432
-
Journal article (peer-reviewed)abstract
- Purpose: Cigarette smoke is known to interact with the metabolism of several anticancer drugs. It may also affect the incidence and severity of adverse events and efficacy of chemotherapy. The main objective of this study was to examine the effects of smoking on the pharmacokinetics and toxicities of patients treated with docetaxel or paclitaxel.Experimental Design: Smoking status, toxicity profiles, and pharmacokinetic parameters (calculated by nonlinear mixed-effect modeling population analysis) were determined in 566 patients (429 nonsmokers and 137 smokers) treated with docetaxel or paclitaxel.Results: Smokers treated with docetaxel showed less grade IV neutropenia (35% vs. 52%; P = 0.01) than nonsmokers. Smokers treated with paclitaxel had less grade III-IV leukopenia than nonsmokers (12% vs. 25%; P = 0.03), and the white blood cell (WBC) nadir was lower in nonsmokers (median, 2.7 x 10(9)/L; range, 0.05 x 10(9) to 11.6 x 10(9)/L) than in smokers (median, 3.3 x 10(9)/L; range 0.8 x 10(9) to 10.2 x 10(9)/L; P = 0.02). Of interest, significantly lower WBC counts and absolute neutrophil counts at baseline were seen in nonsmoking patients treated with paclitaxel (P = 0.0001). Pharmacokinetic parameters were similar in smokers and nonsmokers for both taxanes.Conclusion: Cigarette smoking does not alter the pharmacokinetic determinants of docetaxel and paclitaxel. Smokers treated with docetaxel and paclitaxel have less neutropenia and leukopenia, but further research is warranted to elucidate this potential protective effect.
|
|
| 4. |
- Eechoute, Karel, et al.
(author)
-
A long-term prospective population pharmacokinetic study on imatinib plasma concentrations in GIST patients
- 2012
-
In: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 18:20, s. 5780-5787
-
Journal article (peer-reviewed)abstract
- Purpose: Imatinib minimal (trough) plasma concentrations after one month of treatment have shown a significant association with clinical benefit in patients with gastrointestinal stromal tumors (GIST). Considering that a retrospective pharmacokinetic analysis has also suggested that imatinib clearance increases over time in patients with soft tissue sarcoma and GIST, the primary aim of this study was to assess systemic exposure to imatinib at multiple time points in a long-term prospective population pharmacokinetic study. As imatinib is mainly metabolized in the liver, our secondary aim was to elucidate the potential effects of the volume of liver metastases on exposure to imatinib. Experimental Design: Full pharmacokinetic blood sampling was conducted in 50 patients with GIST on the first day of imatinib treatment, and after one, six, and 12 months. In addition, on day 14, and monthly during imatinib treatment, trough samples were taken. Pharmacokinetic analysis was conducted using a compartmental model. Volume of liver metastases was assessed by computed tomographic (CT) imaging. Results: After 90 days of treatment, a significant decrease in imatinib systemic exposure of 29.3% compared with baseline was observed (P < 0.01). For every 100 cm 3 increase of metastatic volume, a predicted decrease of 3.8% in imatinib clearance was observed. Conclusions: This is the first prospective pharmacokinetic study in patients with GIST, showing a significant decrease of approximately 30% in imatinib exposure after long-term treatment. This means that future "trough level - clinical benefit" analyses should be time point specific. GIST liver involvement, however, has a marginal effect on imatinib clearance.
|
|
| 5. |
|
|
| 6. |
- Henningsson, Anja, et al.
(author)
-
Mechanism-based pharmacokinetic model for paclitaxel
- 2001
-
In: Journal of Clinical Oncology. - 0732-183X .- 1527-7755. ; 19:20, s. 4065-4073
-
Journal article (peer-reviewed)abstract
- PURPOSE To create a model based on known mechanisms of paclitaxel distribution that could describe the pharmacokinetics (PK) of total and unbound plasma concentrations, as well as blood concentrations. In addition, to investigate the relationship between exposure, based on unbound and total concentrations, and neutropenia. PATIENTS AND METHODS Paclitaxel and Cremophor EL (CrEL) concentrations were obtained from 23 female and three male patients (50 courses in total) with different cancer types that received paclitaxel (Taxol; Bristol-Myers Squibb Co, Princeton, NJ) (135 to 225 mg/m(2)) as 3- or 24-hour intravenous infusions. Seven of the patients received combination therapy with doxorubicin or cisplatin. The population PK model was built to fit three types of data simultaneously: unbound, total plasma, and blood concentrations. The area under the curve, threshold, and general models were used to relate neutrophil survival fraction from 19 patients (29 courses in total) to exposure based on unbound and total plasma concentration, respectively. RESULTS The PK model included a linear three-compartment model for unbound concentration, binding directly proportional to CrEL, linear and nonlinear binding to plasma proteins, and linear and nonlinear binding to blood cells. The threshold model best described the PK/pharmacodynamic (PD) relationship for total concentration. No distinction could be made between the models for unbound drug. CONCLUSION Earlier PK models for paclitaxel have been empirical. This study shows that a mechanistic model can be used to describe the nonlinear PK of paclitaxel. There is an indication that the PK/PD relationship is not the same for unbound and total plasma concentrations.
|
|
| 7. |
|
|
| 8. |
- Mathijssen, Ron H J, et al.
(author)
-
Irinotecan pathway genotype analysis to predict pharmacokinetics
- 2003
-
In: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 9:9, s. 3246-3253
-
Journal article (peer-reviewed)abstract
- PURPOSE: The purpose was to explore the relationships between irinotecan disposition and allelic variants of genes coding for adenosine triphosphate binding cassette transporters and enzymes of putative relevance for irinotecan. EXPERIMENTAL DESIGN: Irinotecan was administered to 65 cancer patients as a 90-min infusion (dose, 200-350 mg/m(2)), and pharmacokinetic data were obtained during the first cycle. All patients were genotyped for variants in genes encoding MDR1 P-glycoprotein (ABCB1), multidrug resistance-associated proteins MRP-1 (ABCC1) and MRP-2 (canalicular multispecific organic anion transporter; ABCC2), breast cancer resistance protein (ABCG2), carboxylesterases (CES1, CES2), cytochrome p450 isozymes (CYP3A4, CYP3A5), UDP glucuronosyltransferase (UGT1A1), and a DNA-repair enzyme (XRCC1), which was included as a nonmechanistic control. RESULTS: Eighteen genetic variants were found in nine genes of putative importance for irinotecan disposition. The homozygous T allele of the ABCB1 1236C>T polymorphism was associated with significantly increased exposure to irinotecan (P = 0.038) and its active metabolite SN-38 (P = 0.031). Pharmacokinetic parameters were not related to any of the other multiple variant genotypes, possibly because of the low allele frequency. The extent of SN-38 glucuronidation was slightly impaired in homozygous variants of UGT1A1*28, although differences were not statistically significant (P = 0.22). CONCLUSIONS: It is concluded that genotyping for ABCB1 1236C>T may be one of the factors assisting with dose optimization of irinotecan chemotherapy in cancer patients. Additional investigation is required to confirm these findings in a larger population and to assess relationships between irinotecan disposition and the rare variant genotypes, especially in other ethnic groups.
|
|
| 9. |
- van der Bol, Jessica M., et al.
(author)
-
A CYP3A4 Phenotype-Based Dosing Algorithm for Individualized Treatment of Irinotecan
- 2010
-
In: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 16:2, s. 736-742
-
Journal article (peer-reviewed)abstract
- Purpose: Irinotecan, the prodrug of SN-38, is extensively metabolized by cytochrome P450-3A4 (CYP3A4). A randomized trial was done to assess the utility of an algorithm for individualized irinotecan dose calculation based on a priori CYP3A4 activity measurements by the midazolam clearance test. Experimental Design: Patients were randomized to receive irinotecan at a conventional dose level of 350 mg/m(2) (group A) or doses based on an equation consisting of midazolam clearance, gamma-glutamyl-transferase, and height (group B). Pharmacokinetics and toxicities were obtained during the first treatment course. Results: Demographics of 40 evaluable cancer patients were balanced between both groups, including UGT1A1*28 genotype and smoking status. The absolute dose of irinotecan ranged from 480 to 800 mg in group A and 380 to 1,060 mg in group B. The mean absolute dose and area under the curve of irinotecan and SN-38 were not significantly different in either group (P > 0.18). In group B, the interindividual variability in the area under the curve of irinotecan and SN-38 was reduced by 19% and 25%, respectively (P > 0.22). Compared with group A, the incidence of grades 3 to 4 neutropenia was >4-fold lower in group B (45 versus 10%; P = 0.013). The incidence of grades 3 to 4 diarrhea was equal in both groups (10%). Conclusions: Incorporation of CYP3A4 phenotyping in dose calculation resulted in an improved predictability of the pharmacokinetic and toxicity profile of irinotecan, thereby lowering the incidence of severe neutropenia. In combination with UGT1A1*28 genotyping, CYP3A4 phenotype determination should be explored further as a strategy for the individualization of irinotecan treatment.
|
|
| 10. |
- van der Bol, Jessica M., et al.
(author)
-
Cigarette smoking and irinotecan treatment : Pharmacokinetic interaction and effects on neutropenia
- 2007
-
In: Journal of Clinical Oncology. - 0732-183X .- 1527-7755. ; 25:19, s. 2719-2726
-
Journal article (peer-reviewed)abstract
- Purpose Several constituents of cigarette smoke are known to interact with drug metabolizing enzymes and potentially affect treatment outcome with substrate drugs. The purpose of this study was to determine the effects of cigarette smoking on the pharmacokinetics and adverse effects of irinotecan. Patients and Methods A total of 190 patients (49 smokers, 141 nonsmokers) treated with irinotecan (90-minute intravenous administration on a 3-week schedule) were evaluated for pharmacokinetics. Complete toxicity data were available in a subset of 134 patients receiving 350 mg/m(2) or 600 mg flat-fixed dose irinotecan. Results In smokers, the dose-normalized area under the plasma concentration-time curve of irinotecan was significantly lower (median, 28.7 v 33.9 ng . h/mL/mg; P = .001) compared with nonsmokers. In addition, smokers showed an almost 40% lower exposure to SN-38 (median, 0.54 v 0.87 ng . h/mL/mg; P < .001) and a higher relative extent of glucuronidation of SN-38 into SN-38G (median, 6.6 v 4.5; P = .006). Smokers experienced considerably less hematologic toxicity. In particular, the incidence of grade 3 to 4 neutropenia was 6% in smokers versus 38% in nonsmokers (odds ratio [OR], 0.10; 95% CI, 0.02 to 0.43; P < .001). There was no significant difference in incidence of delayed-onset diarrhea (6% v 15%; OR, 0.34; 95% CI, 0.07 to 1.57; P = .149). Conclusion This study indicates that smoking significantly lowers both the exposure to irinotecan and treatment-induced neutropenia, indicating a potential risk of treatment failure. Although the underlying mechanism is not entirely clear, modulation of CYP3A and uridine diphosphate glucuronosyltransferase isoform 1A1 may be part of the explanation. The data suggest that additional investigation is warranted to determine whether smokers are at increased risk for treatment failure.
|
|
| 11. |
- Xie, Rujia, et al.
(author)
-
Clinical pharmacokinetics of irinotecan and its metabolites in relation with diarrhea
- 2002
-
In: Clinical Pharmacology and Therapeutics. - : Springer Science and Business Media LLC. - 0009-9236 .- 1532-6535. ; 72:3, s. 265-275
-
Journal article (other academic/artistic)abstract
- OBJECTIVES: Our objective was to build population pharmacokinetic models that describe plasma concentrations of irinotecan (CPT-11) and its metabolites 7-ethyl-10-hydroxycamptothecin (SN-38) and SN-38 glucuronide (SN-38G) and to investigate the pharmacokinetic-pharmacodynamic relationships between drug exposure and diarrhea, the major dose-limiting toxicity. METHODS: Data were obtained from 109 patients (65 men and 44 women) who received 1.5-hour (range, 0.75- to 2.25-hour) intravenous infusions of irinotecan at doses that ranged from 100 to 350 mg/m(2); 44 patients had a second course. The population pharmacokinetic models were developed to describe plasma concentration-time profiles. The area under the concentration-time curve from time zero to 60 hours [AUC (0-60)] was used as a measure of drug exposure to model the probabilities of diarrhea with use of a logistic regression model. RESULTS: A 3-compartment pharmacokinetic model best described the disposition of irinotecan, whereas SN-38 and SN-38G showed 2-compartmental characteristics. The population estimate of clearance for irinotecan was 31.6 L/h, and the volume of distribution at steady-state (V(SS)) was 263 L. The clearance divided by formation fraction (F(m)) was 712 L/h and 66.8 L/h for SN-38 and SN-38G, respectively. The V(SS)/F(m) was 72,000 L for SN-38 and 85.4 L for SN-38G. The frequencies of diarrhea scores in this study were 46% (grade 0), 28% (grade 1), 20% (grade 2), 4% (grade 3), and 2% (grade 4). Significant correlations between AUC(0-60) and diarrhea scores were found for irinotecan (P <.05) and SN-38G (P <.01) but not for SN-38 or the biliary index. CONCLUSIONS: In this population analysis, irinotecan and SN-38G AUC values were appropriate predictors of the risk for diarrhea, and SN-38G AUC showed the stronger relationship of the two. The developed population models may be useful in further clinical development of this agent.
|
|
