| 1. |
- Kloft, Charlotte, et al.
(författare)
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Population pharmacokinetic-pharmacodynamic model for neutropenia with patient subgroup identification : comparison across anticancer drugs
- 2006
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 12:18, s. 5481-5490
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: Cancer chemotherapy, although based on body surface area, often causes unpredictable myelosuppression, especially severe neutropenia. The aim of this study was to evaluate qualitatively and quantitatively the influence of patient-specific characteristics on the neutrophil concentration-time course, to identify patient subgroups, and to compare covariates on system-related pharmacodynamic variable between drugs. Experimental Design: Drug and neutrophil concentration, demographic, and clinical chemistry data of several trials with docetaxel (637 patients), paclitaxel (45 patients), etoposide (71 patients), or topotecan (191 patients) were included in the covariate analysis of a physiology-based pharmacokinetic-pharmacodynamic neutropenia model. Comparisons of covariate relations across drugs were made. Results: A population model incorporating four to five relevant patient factors for each drug to explain variability in the degree and duration of neutropenia has been developed. Sex, previous anticancer therapy, performance status, height, binding partners, or liver enzymes influenced system-related variables and alpha(1)-acid glycoprotein, albumin, bilirubin, concomitant cytotoxic agents, or administration route changed drug-specific variables. Overall, female and pretreated patients had a lower baseline neutrophil concentration. Across-drug comparison revealed that several covariates (e.g., age) had minor (clinically irrelevant) influences but consistently shifted the pharmacodynamic variable in the same direction. Conclusions: These mechanistic models, including patient characteristics that influence drug-specific parameters, form the rationale basis for more tailored dosing of individual patients or subgroups to minimize the risk of infection and thus might contribute to a more successful therapy. In addition, nonsignificant or clinically irrelevant relations on system-related parameters suggest that these covariates could be negligible in clinical trails and daily use.
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| 2. |
- Trame, Mirjam N, et al.
(författare)
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Population pharmacokinetics of busulfan in children : increased evidence for body surface area and allometric body weight dosing of busulfan in children.
- 2011
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 17:21, s. 6867-6877
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Tidskriftsartikel (refereegranskat)abstract
- PURPOSE: To evaluate the best method for dosing busulfan in children, we retrospectively analyzed two different data sets from three different dosing regimens by means of population pharmacokinetics using NONMEM. EXPERIMENTAL DESIGN: The development data set consisted of plasma samples from 94 children, in the age range of 0.4 to 18.8 years, receiving either oral or intravenous busulfan. The external model evaluation data set comprised 24 children, in the age range of 0.1 to 18.9 years, who belonged to the once-daily intravenous busulfan dosing regimen. A one-compartment model with first-order absorption using body surface area (BSA) or allometric body weight (BW) as covariate on clearance (CL) and BW as covariate on volume of distribution (V) were used to describe the results sufficiently. In addition to interindividual variability on all pharmacokinetic parameters, interoccasion variability was included for CL and V. RESULTS: CL values in the present study did not reflect the shape of the CL versus weight curve reported in previous investigations. By external model evaluation, we were able to confirm these findings. Furthermore, bioavailability was calculated to be between 93% and 99% for the development data set. On the basis of the final models, we simulated two dosing schemes according to allometric BW and BSA showing that we estimated to include about 30% more patients into the proposed therapeutic area under the curve (AUC) range of 900 to 1,500 μM*min and could, furthermore, achieve a reduction in the AUC variability when dosed according to the labeled European Medicines Agency (EMA) dosing recommendation. CONCLUSION: We recommend a BSA or an allometric BW dosing regimen for individualizing busulfan therapy in children to reduce variability in busulfan exposure and to improve safety and efficacy of busulfan treatment.
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| 4. |
- van Erp, Nielka P, et al.
(författare)
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Influence of CYP3A4 Inhibition on the Steady-State Pharmacokinetics of Imatinib
- 2007
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 13:24, s. 7394-7400
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: To evaluate the effects of ritonavir, a potent inhibitor of CYP3A4, on the steady-state pharmacokinetics of imatinib. Experimental Design: Imatinib pharmacokinetics were evaluated in cancer patients receiving the drug for at least 2 months, after which ritonavir (600 mg) was administered daily for 3 days. Samples were obtained on the day before ritonavir (day 1) and on the third day (day 4).The in vitro metabolism of imatinib with or without ritonavir and the effect of imatinib on 1-OH-midazolam formation rate, a probe for CYP3A4 activity, were evaluated with human CYP3A4 and pooled liver microsomes. Results: In 11 evaluable patients, the geometric mean (95% confidence interval) area under the curve of imatinib on days 1 and 4 were 42.6 (33.0-54.9) mu g.h/mL and 41.2 (32.1-53.1) mu g.h/mL, respectively (P = 0.65). A population analysis done in NONMEM with a time-dependent covariate confirmed that ritonavir did not influence the clearance or bioavailability of imatinib. In vitro, imatinib was metabolized to the active metabolite CGP74588 by CYP3A4 and CYP3A5 and, to a lesser extent, by CYP2D6. Ritonavir (1 mu mol/L) completely inhibited CYP3A4-mediated metabolism of imatinib to CGP74588 but inhibited metabolism in microsomes by only 50%. Imatinib significantly inhibited CYP3A4 activity in vitro. Conclusion: At steady state, imatinib is insensitive to potent CYP3A4 inhibition and relies on alternate elimination pathways. For agents with complex elimination pathways that involve autoinhibition, interaction studies that are done after a single dose may not be applicable when drugs are administered chronically.
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| 6. |
- Hovstadius, Peter, et al.
(författare)
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A Phase I Study of CHS 828 in Patients with Solid Tumor Malignancy
- 2002
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 8:9, s. 2843-2850
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Tidskriftsartikel (refereegranskat)abstract
- CHS 828 is a cyanoguanidine, which has demonstrated potent antitumor activity in preclinical tumor models. The activity of CHS 828 in vitro showed only low to moderate correlation to other antineoplastic agents suggesting a unique mechanism of action. Ten females and 6 males (median age 58 years) with solid tumors refractory to standard therapy were included in this Phase I study. The study drug was administered to fasting patients as a single oral dose on days 1–5 of each treatment cycle. Patients received one to six cycles of treatment. The doses ranged from 30 mg to 200 mg (total dose within a cycle). Hematological toxicity was generally mild and dominated by transient thrombocytopenia and lymphocytopenia. Nonhematological toxicity most frequently consisted of nausea, vomiting, diarrhea, fatigue, and localized genital mucositis. The dose-limiting toxicities were thrombocytopenia, thrombosis, esophagitis, diarrhea, and constipation. The recommended Phase II dose of CHS 828 was 20 mg once daily for 5 days in cycles of 28 days duration. The extent of systemic exposure of CHS 828 across patients was approximately dose proportional. The time at which the highest drug concentration occurs was 2.2 ± 1.3 h and half-life was 2.1 ± 0.52 h (mean ± SD). Large intra- and interindividual variation in dose level-adjusted maximum plasma concentration and the area under the curve from time 0 h to infinity were observed. There was an apparent inverse relationship between systemic exposure of CHS 828, and thrombocyte and lymphocyte nadir levels. No objective tumor responses were observed, and 7 patients showed stable disease after two courses of therapy.
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| 7. |
- Mathijssen, Ron H J, et al.
(författare)
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Irinotecan pathway genotype analysis to predict pharmacokinetics
- 2003
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265. ; 9:9, s. 3246-3253
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Tidskriftsartikel (refereegranskat)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.
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| 8. |
- Netterberg, Ida, 1988-, et al.
(författare)
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Circulating tumor cell counts is a better predictor of overall survival than dynamic tumor size changes – a quantitative modeling framework
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Ingår i: Clinical Cancer Research. - 1078-0432 .- 1557-3265.
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Purpose: Quantitative relationships between treatment-induced changes in tumor size and circulating tumor cell (CTC) counts, and their links to overall survival (OS), are lacking. We here present a population modeling framework identifying and quantifying such relationships, based on longitudinal data collected in patients with metastatic colorectal cancer (mCRC) to evaluate the value of tumor size and CTC counts as predictors of OS.Experimental design: A pharmacometric approach (i.e., population pharmacodynamic modeling) was used to characterize the changes in tumor size and CTC count and evaluate them as predictors of OS in 451 patients with mCRC treated with chemotherapy and targeted therapy in a prospectively randomized phase 3 study (CAIRO2).Results: A tumor size model of tumor quiescence and drug-resistance, was used to characterize the tumor size time-course, and was, in addition to the total normalized dose (i.e., of all administered drugs) in a given cycle, related to the CTC counts through a negative binomial model (CTC model). A CTC count≥3/7.5 mL (hazard ratio=3.51, 95% confidence interval: 2.85-4.32), as described by the CTC model, was a better predictor of OS than tumor size changes. The modeling framework was applied to explore if dose-modifications (increased and reduced) would result in a CTC count below 3/7.5 mL after 1-2 weeks of treatment.Conclusions: Time-varying CTC counts can be useful for early predicting OS in patients with mCRC, and may therefore have potential for model-based treatment individualization. Although tumor size had a strong connection to CTC, its link to OS was weaker.
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