Jan H M Schellens

Utrecht University, Utrecht, Utrecht, Netherlands

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Publications (754)2965.58 Total impact

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    ABSTRACT: This work was initiated to extend data on the effect of pharmacogenetics and chemotherapy pharmacokinetics (PK) on clinical outcome in patients with gastrointestinal malignancies. We assessed 44 gene polymorphisms in 16 genes (TYMS, MTHFR, GSTP1, GSTM1, GSTT1, DPYD, XRCC1, XRCC3, XPD, ERCC1, RECQ1, RAD54L, ABCB1, ABCC2, ABCG2 and UGT2B7) in 64 patients with metastatic colorectal cancer (CRC) receiving capecitabine/oxaliplatin and 76 patients with advanced gastroesophageal cancer (GEC) receiving epirubicin/cisplatin/capecitabine, respectively. Plasma concentrations of anticancer drugs were measured for up to 24 h, and results were submitted to population PK analysis. We calculated the association between gene polymorphisms, chemotherapy exposure, tumor response, progression-free survival (PFS), overall survival (OS) and chemotherapy-related toxicity using appropriate statistical tests. Patients with a low clearance of 5FU were at increased risk of neutropenia (P < 0.05) and hand-foot syndrome (P = 0.002). DPYD T85C, T1896C and A2846T mutant variants were associated with diarrhea (P < 0.05) and HFS (P < 0.02), and IVS14+1G>A additionally with diarrhea (P < 0.001). The TYMS 2R/3G, 3C/3G or 3G/3G promoter variants were associated with worse PFS in the CRC (HR = 2.0, P < 0.01) and GEC group (HR = 5.4, P < 0.001) and worse OS in the GEC group (HR = 4.7, P < 0.001). The GSTP1 A313G mutant variant was associated with a higher PFS (HR = 0.55, P = 0.001) and OS (HR = 0.60, P = 0.002) in the CRC group. Germline polymorphisms of DPYD, TYMS and GSTP1 have a significant effect on toxicity and clinical outcome in patients receiving capecitabine-based chemotherapy for advanced colorectal or gastroesophageal cancer. These data should further be validated in prospective clinical studies.
    Cancer Chemotherapy and Pharmacology 02/2015; · 2.80 Impact Factor
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    ABSTRACT: Purpose Overdose with baclofen, a derivative of the inhibitory neurotransmitter γ-aminobutyric acid, may lead to severe respiratory and central nervous system depression and can be life-threatening. Prolonged half-lives of baclofen, of up to 34 h, have been reported in patients after overdose. Hemodialysis has proven to be a successful approach to improve clearance of baclofen, but the value of continuous venovenous hemofiltration (CVVH) is unclear. We applied CVVH in a patient with acute baclofen overdose. Methods Pharmacokinetic measurements of baclofen in serum and hemofiltrate were made at six time points after hospital admission. Baclofen concentration-time data were analyzed using non-compartmental methods, and the relative contribution of clearance by hemofiltration to total baclofen clearance was calculated. Results Baclofen concentrations in serum varied between 1.81 and 0.05 mg/L. Concentrations of baclofen in hemofiltrate were within the same range (between 0.74 and 0.05 mg/L), and the elimination half-life during hemofiltration was estimated at 4.8 h. Total clearance and clearance via hemofiltration were estimated at 6.6 and 2.4 L/h, indicating that clearance could be increased by approximately 57 % by applying hemofiltration. Conclusions The presented case demonstrates the usefulness of CVVH in the treatment of baclofen overdose and indicates that CVVH can be used as an alternative to hemodialysis in patients with overdose of baclofen.
    European Journal of Clinical Pharmacology 01/2015; · 2.70 Impact Factor
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    ABSTRACT: Recently, there has been a renewed interest in the development of new drugs for the treatment of leishmaniasis. This has spurred the need for pharmacodynamic markers to monitor and compare therapies specifically for visceral leishmaniasis, in which the primary recrudescence of parasites is a particularly long-term event that remains difficult to predict. We performed a systematic review of studies evaluating biomarkers in human patients with visceral, cutaneous, and post-kala-azar dermal leishmaniasis, which yielded a total of 170 studies in which 53 potential pharmacodynamic biomarkers were identified. In conclusion, the large majority of these biomarkers constituted universal indirect markers of activation and subsequent waning of cellular immunity and therefore lacked specificity. Macrophage-related markers demonstrate favorable sensitivity and times to normalcy, but more evidence is required to establish a link between these markers and clinical outcome. Most promising are the markers directly related to the parasite burden, but future effort should be focused on optimization of molecular or antigenic targets to increase the sensitivity of these markers. In general, future research should focus on the longitudinal evaluation of the pharmacodynamic biomarkers during treatment, with an emphasis on the correlation of studied biomarkers and clinical parameters.
    Antimicrobial Agents and Chemotherapy 01/2015; 59(1):1-14. · 4.57 Impact Factor
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    ABSTRACT: Currently, no country-specific metastatic breast cancer (MBC) observational costing data are available for the Netherlands and Belgium. Our aim is to describe country-specific resource use and costs of human epidermal receptor 2 (HER-2)-positive MBC in the Netherlands and Belgium, making use of real-world data.The eligibility period for patient selection was from April 2004 to April 2010. Inclusion and retrospective data collection begins at the time of first diagnosis of HER-2-positive MBC during the eligibility period and ends 24 months post-index diagnosis of MBC or at patient death.We identified 88 eligible patients in the Netherlands and 44 patients in Belgium. The total costs of medical treatment and other resource use utilisation per patient was €48 301 in the Netherlands and €37 431 in Belgium. Majority of costs was related to the use of trastuzumab in both countries, which was 50% of the total costs in the Netherlands and 56% in Belgium respectively.Our study provides estimates of resource use and costs for HER-2-positive MBC in the Netherlands and Belgium. We noticed various differences in resource use patterns between both countries demonstrating caution is needed when transferring cost estimates between countries.
    European Journal of Cancer Care 12/2014; · 1.31 Impact Factor
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    ABSTRACT: Previously published pharmacokinetics (PK) models for sunitinib and its active metabolite SU12662 were based on a limited dataset or lacked important elements such us correlations between sunitinib and its metabolite. The current study was to develop an improved PK model that circumvented these limitations and to prove the utility of the PK model in treatment optimisation in clinical practice.
    British Journal of Clinical Pharmacology 11/2014; · 3.69 Impact Factor
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    ABSTRACT: Purpose Tumor necrosis factor (TNF)-like weak inducer of apoptosis (TWEAK) and fibroblast growth factor-inducible molecule 14 (Fn14) are a ligand-receptor pair frequently overexpressed in solid tumors. TWEAK:Fn14 signaling regulates multiple oncogenic processes through MAPK, AKT, and NFκB pathway activation. A phase I study of RG7212, a humanized anti-TWEAK IgG1κ monoclonal antibody, was conducted in patients with advanced solid tumors expressing Fn14. Methods Dose escalations, over a 200- to 7200-mg range, were performed with patients enrolled in weekly (QW), bi-weekly (Q2W), or every-three-week (Q3W) schedules. Primary objectives included determination of dose and safety profile. Secondary endpoints included assessments related to inhibition of TWEAK:Fn14 signaling, tumor proliferation, tumor immune cell infiltration, and pharmacokinetics. Results In 192 treatment cycles administered to 54 patients, RG7212 was well-tolerated with no dose-limiting toxicities observed. More than 95% of related adverse events were limited to grade 1/2. Pharmacokinetics were dose proportional for all cohorts, with a t1/2 of 11-12 days. Pharmacodynamic changes included clearance of free and total TWEAK ligand and reductions in tumor Ki-67 and TRAF1. A patient with BRAF wild-type melanoma who received 36 weeks of RG7212 therapy had tumor regression and pharmacodynamic changes consistent with antitumor effects. Fifteen patients (28%) received 16 or more weeks of RG7212 treatment.
    Clinical Cancer Research 11/2014; · 8.19 Impact Factor
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    ABSTRACT: Lenvatinib is an orally available multi-targeted tyrosine kinase inhibitor with anti-angiogenic and antitumor activity. To get more insight into the disposition of lenvatinib, a mass balance study was performed in patients with advanced solid tumors. A single oral 24 mg (100 μCi) dose of (14)C-lenvatinib was administered to six patients, followed by collection of blood, plasma, urine and feces for 7 to 10 days. The collected material was analyzed for total radioactivity, unchanged lenvatinib and selected metabolites. The safety and antitumor effect of a daily oral dose of 24 mg non-labeled lenvatinib were assessed in the extension phase of the study. Peak plasma concentrations of lenvatinib and total radioactivity were reached 1.6 and 1.4 h after administration, respectively, and their terminal phase half-lifes were 34.5 and 17.8 h, respectively. Unchanged lenvatinib systemic exposure accounted for 60 % of the total radioactivity in plasma. Peak concentrations of the analyzed metabolite were over 700-fold lower than the peak plasma concentration of lenvatinib. Ten days after the initial dose, the geometric mean (± CV) recovery of administered dose was 89 % ±10 %, with 64 % ±11 % recovered in feces and 25 % ±18 % in urine. Unchanged lenvatinib in urine and feces accounted for 2.5 % ±68 % of the administered dose, indicating a major role of metabolism in the elimination of lenvatinib. In conclusion, lenvatinib is rapidly absorbed and extensively metabolized, with subsequent excretion in urine and, more predominantly, in feces. Additionally, lenvatinib showed acceptable safety and preliminary antitumor activity.
    Investigational New Drugs 11/2014; · 3.50 Impact Factor
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    ABSTRACT: Background This phase I/II study determined the maximal tolerable dose, dose limiting toxicities, antitumor activity, the pharmacokinetics and pharmacodynamics of ruthenium compound NAMI-A in combination with gemcitabine in Non-Small Cell Lung Cancer patients after first line treatment. Methods Initial dose escalation of NAMI-A was performed in a 28 day cycle: NAMI-A as a 3 h infusion through a port-a-cath at a starting dose of 300 mg/m(2) at day 1, 8 and 15, in combination with gemcitabine 1,000 mg/m(2) at days 2, 9 and 16. Subsequently, dose escalation of NAMI-A in a 21 day schedule was explored. At the maximal tolerable dose level of this schedule an expansion group was enrolled of which 15 patients were evaluable for response. Results Due to frequent neutropenic dose interruptions in the third week, the 28 day schedule was amended into a 21 day schedule. The maximal tolerable dose was 300 and 450 mg/m(2) of NAMI-A (21 day schedule). Main adverse events consisted of neutropenia, anemia, elevated liver enzymes, transient creatinine elevation, nausea, vomiting, constipation, diarrhea, fatigue, and renal toxicity. Conclusion NAMI-A administered in combination with gemcitabine is only moderately tolerated and less active in NSCLC patients after first line treatment than gemcitabine alone.
    Investigational New Drugs 10/2014; · 3.50 Impact Factor
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    ABSTRACT: Purpose:Since a dose-response relationship is characteristic of conventional chemotherapy, this concept is widely used for the development of novel cytotoxic (CTX) drugs. However, the need to reach the maximum tolerated dose (MTD) to obtain optimal benefit with molecularly targeted agents (MTA) is controversial. In this study we evaluated the relationship between dose and efficacy in a large cohort of phase I patients with solid tumors. Experimental Design:We collected data on 1182 consecutive patients treated in phase I trials in 14 European institutions in 2005-2007. Inclusion criteria were: a) patients treated within completed single agent studies where a maximum-administered-dose was defined; b) RECIST/survival data available. Results:72% of patients were included in trials with MTA (N=854) and 28% in trials with CTX (N=328). The objective response (OR) rate was 3% and disease control at 6 months was 11%. OR for CTX was associated with higher doses (median 92% of MTD); this was not the case for MTA, where patients achieving OR received a median of 50% of MTD. For trials with MTA, patients treated at intermediate doses (40-80%) had better survival compared to those receiving low or high dose (p=0.038). On the contrary, there was a direct association between higher dose and better OS for CTX agents (p=0.003). Conclusions:While these results support the development of novel CTX based on MTD, we found no direct relationship between higher doses and response with MTA in unselected patients. However, the longest OS was seen in patients treated with MTA at intermediate doses (40-80% of MTD).
    Clinical Cancer Research 09/2014; · 8.19 Impact Factor
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    ABSTRACT: Older adults receiving cytotoxic agents may be more susceptible to hematologic toxicities because of progressive reduction in organ functions and multiple co-morbidities. Because older adults are under-represented in clinical trials, this retrospective study aims to evaluate hematologic toxicity of gemcitabine-based regimens in older patients compared with their younger counterparts in clinical practice.
    Drugs & Aging 09/2014; · 2.50 Impact Factor
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    ABSTRACT: Background:Capecitabine is an established treatment alternative to intravenous 5-fluorouracil (5-FU) for patients with rectal cancer receiving chemoradiotherapy. Its place in the treatment of locally advanced anal carcinoma (AC), however, remains undetermined. We investigated whether capecitabine is as effective as 5-FU in the treatment of patients with locally advanced AC.Methods:One hundred and five patients with squamous cell AC stage T2-4 (T2>4 cm), N0-1, M0 or T1-4, N2-3, M0, were included in this retrospective study. Forty-seven patients were treated with continuous 5-FU (750 mg m(-2)) on days 1-5 and 29-33, mitomycin C (MMC, 10 mg m(-2)) on day 1, and radiotherapy; 58 patients were treated with capecitabine (825 mg m(-2) b.i.d. on weekdays), MMC (10 mg m(-2)) on day 1, and radiotherapy. The primary end points of the study were: clinical complete response rate, locoregional control (LRC) and overall survival (OS). Secondary end points were: colostomy-free survival (CFS), toxicity and associations of genetic polymorphisms (GSTT1, GSTM1, GSTP1 and TYMS) with outcome and toxicity.Results:Clinical complete response was achieved in 41/46 patients (89.1%) with 5-FU and in 52/58 patients (89.7%) with capecitabine. Three-year LRC was 76% and 79% (P=0.690, log-rank test), 3-year OS was 78% and 86% (P=0.364, log-rank test) and CFS was 65% and 79% (P=0.115, log-rank test) for 5-FU and capecitabine, respectively. GSTT1 and TYMS genotypes were associated with severe (grade 3-4) toxicity.Conclusions:Capecitabine combined with MMC and radiotherapy was equally effective as 5-FU-based chemoradiotherapy. This study shows that capecitabine can be used as an acceptable alternative to 5-FU for the treatment of AC.British Journal of Cancer advance online publication 28 August 2014; doi:10.1038/bjc.2014.467 www.bjcancer.com.
    British Journal of Cancer 08/2014; · 4.82 Impact Factor
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    ABSTRACT: Background The aim of the current work was to perform a clinical trial simulation (CTS) analysis to optimize a drug-drug interaction (DDI) study of vincristine in children who also received azole antifungals, taking into account challenges of conducting clinical trials in this population, and, to provide a motivating example of the application of CTS in the design of pediatric oncology clinical trials.ProcedureA pharmacokinetic (PK) model for vincristine in children was used to simulate concentration-time profiles. A continuous model for body surface area versus age was defined based on pediatric growth curves. Informative sampling time windows were derived using D-optimal design. The CTS framework was used to different magnitudes of clearance inhibition (10%, 25%, or 40%), sample size (30–500), the impact of missing samples or sampling occasions, and the age distribution, on the power to detect a significant inhibition effect, and in addition, the relative estimation error (REE) of the interaction effect.ResultsA minimum group specific sample size of 38 patients with a total sample size of 150 patients was required to detect a clearance inhibition effect of 40% with 80% power, while in the case of a lower effect of clearance inhibition, a substantially larger sample size was required. However, for the majority of re-estimated drug effects, the inhibition effect could be estimated precisely (REE < 25%) in even smaller sample sizes and with lower effect sizes.Conclusion This work demonstrated the utility of CTS for the evaluation of PK clinical trial designs in the pediatric oncology population. Pediatr Blood Cancer © 2014 Wiley Periodicals, Inc.
    Pediatric Blood & Cancer 08/2014; 61(12). · 2.35 Impact Factor
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    ABSTRACT: BMS-275,183 is a novel oral C-4 methyl carbonate analogue of paclitaxel. Recently, a drug-drug interaction between BMS-275,183 and benzimidazole proton pump inhibitors (PPIs) was suggested in clinical trials resulting in elevated drug exposure and toxicity. We explored whether the interaction takes place at the level of P-glycoprotein (Pgp, MDR1, ABCB1), Breast Cancer Resistance Protein (BCRP, ABCG2) and MRP2 (ABCC2) using in vitro and in vivo models. In vitro cell survival, drug accumulation, efflux and transport studies with BMS-275,183 were performed employing MDCKII (wild-type, MDR1, BCRP, MRP2) and LLCPK (wild-type and MDR1) cells. In vivo the pharmacokinetics and tissue distribution of BMS-275,183 after p.o. and i.v. administration were explored in Mdr1a/1b(-/-) and wild-type mice, in presence or absence of the PPI pantoprazole. Results In vitro, BMS-275,183 was found to be a good substrate for MDR1, a moderate substrate for MRP2 and not a substrate for BCRP. In vivo, oral bioavailability, plasma AUC0-6h and brain concentrations were significantly 1.5-, 4-, and 2-fold increased, respectively, in Mdr1a/1b(-/-) compared with wild-type mice (p < 0.001). However, oral co-administration of pantoprazole (40 mg/kg) did not alter the pharmacokinetics of BMS-275,183 in wild-type mice. Conclusions BMS-275,183 is efficiently transported by Pgp and to a lesser extent by MRP2 in vitro. Genetic deletion of Pgp significantly altered the pharmacokinetics and brain distribution of p.o. and i.v. administered BMS-275,183 in Mdr1a/1b-/- compared to wild-type mice. Oral co-administration of BMS-275,183 with pantoprazole did not affect the pharmacokinetics of BMS-275,183 in wild-type mice, suggesting no interaction with PPI at the dose employed.
    Investigational New Drugs 07/2014; 32(6). · 3.50 Impact Factor
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    ABSTRACT: Purpose:This phase I expansion study assessed safety, pharmacodynamic effects and antitumor activity of RO4987655, a pure MEK inhibitor in selected advanced solid tumor patients. Experimental Design:We undertook a multicenter phase I two-part study (dose escalation, cohort expansion). Here we present the part 2 expansion that included melanoma, non-small cell lung cancer (NSCLC) and colorectal cancer (CRC) with oral RO4987655 administered continuously at recommended doses of 8.5 mg twice-daily until progressive disease (PD). Sequential tumor sampling investigated multiple markers of pathway activation/tumor effects, including ERK-phosphorylation and Ki-67 expression. BRAF- and KRAS-testing were implemented as selection criteria and broader tumor mutational analysis added. Results:95 patients received RO4987655, including 18 BRAF-mutant melanoma, 23 BRAF wild-type melanoma, 24 KRAS-mutant NSCLC, and 30 KRAS-mutant CRC. Most frequent adverse events were rash, acneiform dermatitis and gastrointestinal disorders, mostly grade 1/2. Four (24%) of 17 BRAF-mutated melanoma had partial response as did four (20%) of 20 BRAF wild-type melanoma and two (11%) of 18 KRAS-mutant NSCLC. All KRAS-mutant CRC developed PD. Paired tumor biopsies demonstrated reduced ERK-phosphorylation among all cohorts but significant differences among cohorts in Ki-67 modulation. 69% showed decrease in fluorodeoxyglucose-uptake between baseline and day 15. Detailed mutational profiling confirmed RAS/RAF screening and identified additional aberrations (NRAS/non-BRAF melanomas; PIK3CA/KRAS CRC) without therapeutic implications. Conclusions:Safety profile of RO4987655 was comparable to other MEK inhibitors. Single agent activity was observed in all entities except CRC. Evidence of target modulation and early biological activity were shown amongst all indications independent of mutational status.
    Clinical Cancer Research 06/2014; · 8.19 Impact Factor
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    ABSTRACT: Pertuzumab is a recombinant humanized monoclonal antibody that specifically targets the extracellular dimerization domain (subdomain II) of HER2. Based on the positive opinion from the European Medicines Agency (EMA) on March 4, 2013, a marketing authorization valid throughout the European Union (EU) was issued for pertuzumab (Perjeta) for use in combination with trastuzumab and docetaxel for the treatment of adult patients with HER2-positive metastatic or locally recurrent unresectable breast cancer who have not received previous anti-HER2 therapy or chemotherapy for their metastatic disease. The demonstration of clinical benefit for pertuzumab was based on a single, phase III, randomized, double-blind, placebo-controlled trial comparing the efficacy and safety of pertuzumab plus trastuzumab plus docetaxel versus placebo plus trastuzumab plus docetaxel in previously untreated patients with locally advanced or metastatic HER2-positive breast cancer. In the primary analysis, median progression-free survival was 18.5 months in the pertuzumab group compared with 12.4 months in the placebo group (hazard ratio [HR]: 0.62; 95% confidence interval [CI]: 0.51-0.75; p < .0001). For the secondary endpoints, overall survival (HR: 0.66; 95% CI: 0.52-0.84; p = .0008) and objective response rate (80.2% vs. 69.3%) were also favored in the pertuzumab group. Toxicity was similar between groups except for higher incidence of diarrhea, rash, mucosal inflammation, dry skin, and neutropenia for pertuzumab compared with placebo. This paper summarizes the scientific review of the application leading to approval in the EU. The detailed scientific assessment report and product information, including the summary of product characteristics, are available on the EMA website (http://www.ema.europa.eu).
    The Oncologist 06/2014; · 4.54 Impact Factor
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    ABSTRACT: The anti-estrogenic effect of tamoxifen is suggested to be mainly attributable to its metabolite (Z)-endoxifen, and a minimum therapeutic threshold for (Z)-endoxifen in serum has been proposed. The objective of this research was to establish the relationship between dried blood spot (DBS) and serum concentrations of tamoxifen and (Z)-endoxifen to allow the use of DBS sampling, a simple and patient-friendly alternative to venous sampling, in clinical practice. Paired DBS and serum samples were obtained from 50 patients using tamoxifen and analyzed using HPLC-MS/MS. Serum concentrations were calculated from DBS concentrations using the formula calculated serum concentration = DBS concentration/([1-haematocrit (Hct)] + blood cell-to-serum ratio × Hct). The blood cell-to-serum ratio was determined ex vivo by incubating a batch of whole blood spiked with both analytes. The average Hct for female adults was imputed as a fixed value. Calculated and analyzed serum concentrations were compared using weighted Deming regression. Weighted Deming regression analysis comparing 44 matching pairs of DBS and serum samples showed a proportional bias for both analytes. Serum concentrations were calculated using [Tamoxifen] serum, calculated = [Tamoxifen] DBS /0.779 and [(Z)-Endoxifen] serum, calculated = [(Z)-Endoxifen] DBS /0.663. Calculated serum concentrations were within 20 % of analyzed serum concentrations in 84 and 100 % of patient samples for tamoxifen and (Z)-endoxifen, respectively. In conclusion, DBS concentrations of tamoxifen and (Z)-endoxifen were equal to serum concentrations after correction for Hct and blood cell-to-serum ratio. DBS sampling can be used in clinical practice.
    Breast Cancer Research and Treatment 05/2014; 146(1). · 4.47 Impact Factor
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    ABSTRACT: Purpose Renal impairment (RI) studies are conducted to estimate the impact of RI on pharmacokinetics (PK). In some disease areas, these studies can be difficult to conduct, for instance due to the limited number of eligible patients. The objective of this analysis was to evaluate bias and precision of population PK parameters, and the dose adjustment error (DAE) for RI studies i) with different levels of study design imbalance in the stratification of subjects across RI categories, and ii) that include additional patients in the control arm of RI studies, that may be available from previously conducted PK studies. Methods Study designs were simulated and re-estimated using a hypothetical 2-compartmental PK model with varying magnitude of the fraction of renal elimination (FR) and magnitude of between-subject variability (BSV). The DAE was computed based on the difference between the theoretical necessary dose adjustment versus the empirical estimated dose adjustment to reach a similar exposure as controls. Results Although some design imbalance may still lead to DAEs of acceptable magnitude (DAE < -11.05-14.44 inter-quartile range, IQR), at least some patients are necessary in the more severe RI groups. When 100 additional patients with normal renal function were included in a sub-informative design, the DAE changed from < -7.63-16.64 IQR to < -8.89-8.69 IQR. Conclusions We quantified the impact of study design imbalance on bias and precision of PK parameters and DAE, as may occur for RI studies in some indications. Adding additional data from earlier studies to the analysis dataset improves the bias and precision of PK parameters.
    Investigational New Drugs 05/2014; · 3.50 Impact Factor
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    ABSTRACT: Objectives The aim of this study is to establish the inhibitory effects of 14 commonly used complementary and alternative medicines (CAM) on the metabolism of cytochrome P450 2C9 (CYP2C9) substrates 7-methoxy-4-trifluoromethyl coumarine (MFC) and tolbutamide. CYP2C9 is important for the metabolism of numerous drugs and inhibition of this enzyme by CAM could result in elevated plasma levels of drugs that are CYP2C9 substrates. Especially for anticancer drugs, which have a narrow therapeutic window, small changes in their plasma levels could easily result in clinically relevant toxicities.Methods The effects of CAM on CYP2C9-mediated metabolism of MFC were assessed in Supersomes, using the fluorometric CYP2C9 inhibition assay. In human liver microsomes (HLM) the inhibition of CYP2C9-mediated metabolism of tolbutamide was determined, using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS).Key findingsThe results indicated milk thistle as the most potent CYP2C9 inhibitor. For milk thistle, silybin (main constituent of milk thistle) was mainly responsible for the inhibition of CY2C9.Conclusions Milk thistle and green tea were confirmed as potent inhibitors of CYP2C9-mediated metabolism of multiple substrates in vitro. Clinical studies with milk thistle are recommended to establish the clinical relevance of the demonstrated CYP2C9 inhibition.
    Journal of Pharmacy and Pharmacology. 05/2014;
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    ABSTRACT: Background:The intestinal uptake of the taxanes paclitaxel and docetaxel is seriously hampered by drug efflux through P-glycoprotein (P-gp) and drug metabolism via cytochrome P450 (CYP) 3A. The resulting low oral bioavailability can be boosted by co-administration of P-gp or CYP3A4 inhibitors.Methods:Paclitaxel or docetaxel (10 mg/kg) was administered to CYP3A4-humanised mice after administration of the P-gp inhibitor elacridar (25 mg kg(-1)) and the CYP3A inhibitor ritonavir (12.5 mg kg(-1)). Plasma and brain concentrations of the taxanes were measured.Results:Oral co-administration of the taxanes with elacridar increased plasma concentrations of paclitaxel (10.7-fold, P<0.001) and docetaxel (four-fold, P<0.001). Co-administration with ritonavir resulted in 2.5-fold (paclitaxel, P<0.001) and 7.3-fold (docetaxel, P<0.001) increases in plasma concentrations. Co-administration with both inhibitors simultaneously resulted in further increased plasma concentrations of paclitaxel (31.9-fold, P<0.001) and docetaxel (37.4-fold, P<0.001). Although boosting of orally applied taxanes with elacridar and ritonavir potentially increases brain accumulation of taxanes, we found that only brain concentrations, but not brain-to-plasma ratios, were increased after co-administration with both inhibitors.Conclusions:The oral availability of taxanes can be enhanced by co-administration with oral elacridar and ritonavir, without increasing the brain penetration of the taxanes.British Journal of Cancer advance online publication, 29 April 2014; doi:10.1038/bjc.2014.222 www.bjcancer.com.
    British Journal of Cancer 04/2014; · 5.08 Impact Factor
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    ABSTRACT: Background:Plasma exposure of sunitinib shows large inter-individual variation. Therefore, a pharmacokinetic (PK) study was performed to determine safety and feasibility of sunitinib dosing based on PK levels.Methods:Patients were treated with sunitinib 37.5 mg once daily. At days 15 and 29 of treatment, plasma trough levels of sunitinib and N-desethyl sunitinib were measured. If the total trough level (TTL) was <50 ng ml(-1) and the patient did not show any grade 3 toxicity, the daily sunitinib dose was increased by 12.5 mg. If the patient suffered from grade 3 toxicity, the sunitinib dose was lowered by 12.5 mg.Results:Twenty-nine out of 43 patients were evaluable for PK assessments. Grade 3 adverse events were experienced in seven patients (24%) at the starting dose and in nine patients (31%) after dose escalation. TTLs were below target in 15 patients (52%) at the starting dose. Of these, five patients (17%) reached target TTL after dose escalation without additional toxicity.Conclusions:In a third of the patients that were below target TTL at standard dose, the sunitinib dose could be increased without additional toxicities. This could be the basis for future studies and the implementation of a PK-guided dosing strategy in clinical practice.British Journal of Cancer advance online publication, 15 April 2014; doi:10.1038/bjc.2014.194 www.bjcancer.com.
    British Journal of Cancer 04/2014; · 5.08 Impact Factor

Publication Stats

16k Citations
2,965.58 Total Impact Points


  • 2000–2014
    • Utrecht University
      • • Division of Pharmacoepidemiology and Pharmacotherapy
      • • Department of Pharmaceutical Sciences
      • • Division of Biomedical Analysis
      • • Division of Toxicology
      Utrecht, Utrecht, Netherlands
  • 1993–2014
    • Netherlands Cancer Institute
      • • Department of Clinical Pharmacology
      • • Division of Molecular Pathology
      • • Department of Medical Oncology
      • • Division of Molecular Biology
      • • Division of Experimental Therapy
      • • Department of Neuro-oncology
      Amsterdamo, North Holland, Netherlands
  • 2013
    • University of Amsterdam
      • Faculty of Medicine AMC
      Amsterdamo, North Holland, Netherlands
    • Rijnstate Hospital
      Arnheim, Gelderland, Netherlands
  • 2011–2013
    • European Medicines Agency
      Londinium, England, United Kingdom
    • Dana-Farber Cancer Institute
      • Carole M. and Philip L. Lowe Center for Thoracic Oncology
      Boston, MA, United States
    • Cantonal Hospital of Schwyz
      Schwyz, Schwyz, Switzerland
  • 1994–2013
    • Slotervaartziekenhuis
      Amsterdamo, North Holland, Netherlands
  • 2012
    • Nederlands Jeugd Instituut
      Utrecht, Utrecht, Netherlands
    • Queen's University Belfast
      • Centre for Cancer Research and Cell Biology
      Béal Feirste, N Ireland, United Kingdom
  • 2010–2012
    • The Royal Marsden NHS Foundation Trust
      Londinium, England, United Kingdom
    • Institute of Cancer Research
      Londinium, England, United Kingdom
  • 2001–2012
    • Uppsala University
      • Department of Pharmacy
      Uppsala, Uppsala, Sweden
  • 2009–2011
    • University Medical Center Utrecht
      Utrecht, Utrecht, Netherlands
    • Atrium Medisch Centrum Parkstad
      Heerlen, Limburg, Netherlands
  • 2007–2011
    • Kantonsspital St. Gallen
      San Gallo, Saint Gallen, Switzerland
    • Leiden University Medical Centre
      • Department of Clinical Pharmacy and Toxicology
      Leyden, South Holland, Netherlands
    • Insitute de Cancérologie de l'Ouest - Centre René Gauducheau
      Naoned, Pays de la Loire, France
  • 2002–2010
    • Academisch Medisch Centrum Universiteit van Amsterdam
      • Department of Medical Oncology
      Amsterdam, North Holland, Netherlands
    • Pfizer Inc.
      New York, New York, United States
    • Institut de Cancérologie Gustave Roussy
      • Department of Radiotherapy
      Île-de-France, France
  • 2008–2009
    • Astellas Pharmaceutical
      Northbrook, Illinois, Japan
  • 2004
    • Washington University in St. Louis
      • Alvin J. Siteman Cancer Center
      San Luis, Missouri, United States
    • VU University Medical Center
      Amsterdamo, North Holland, Netherlands
  • 1999–2001
    • Institut Bergonié
      Burdeos, Aquitaine, France
  • 1996–1999
    • Erasmus MC
      • Department of Internal Oncology
      Rotterdam, South Holland, Netherlands
  • 1998
    • University of Glasgow
      Glasgow, Scotland, United Kingdom
  • 1997
    • Erasmus Universiteit Rotterdam
      Rotterdam, South Holland, Netherlands
  • 1988–1991
    • Leiden University
      • Leiden Amsterdam Center for Drug Research
      Leyden, South Holland, Netherlands