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Biomedical subjects

Jaap Verweij

Publications and source records attributed to Jaap Verweij.

At least 91 records · Page 5Linked to original sources
PubMed2003

Phase I pharmacological and bioavailability study of oral diflomotecan (BN80915), a novel E-ring-modified camptothecin analogue in adults with solid tumors.

PURPOSE: Diflomotecan (BN80915) is an E-ring modified camptothecin analogue that possesses greater lactone stability in plasma compared with other topoisomerase I inhibitors, a potential advantage for antitumor activity. As with other camptothecins, oral administration has pharmacological and clinical advantages. This Phase I study was performed to assess the feasibility of the administration of oral diflomotecan, to determine the maximum-tolerated, dose its bioavailability, and to explore the pharmacokinetics. EXPERIMENTAL DESIGN: An initial i.v. bolus was administered to assess the bioavailability of diflomotecan. Fourteen days later, diflomotecan was administered p.o. once daily for 5 days to adult patients with solid malignant tumors and repeated every 3 weeks. BN80915 and its open lactone form BN80942 were measured. RESULTS: Twenty-two patients entered the study and received a total of 57 cycles of oral diflomotecan at flat dose levels of 0.10, 0.20, 0.27, and 0.35 mg. The main toxicity was hematological, but some patients experienced alopecia, mild gastrointestinal toxicity, and fatigue. At the 0.35-mg dose level, 2 of 4 patients experienced dose-limiting toxicity comprising grade 3 thrombocytopenia with epistaxis and febrile neutropenia in 1 patient and uncomplicated grade 4 neutropenia lasting for >7 days in another. Toxicity was acceptable at the 0.27-mg dose level at which dose-limiting toxicities were observed in 3 of 12 patients (grade 4 neutropenia > 7 days, complicated by fever in 1 patient but without other signs of infection). After two cycles of diflomotecan, 6 patients had disease stabilization, which was maintained in 2 patients for 9 months and >1 year, respectively. Diflomotecan pharmacokinetics were linear over the dose range studied. Systemic exposure correlated with the fall in WBC counts. The mean oral bioavailability (+/-SD) was 72.24 +/- 59.2% across all dose levels. Urinary excretion of BN80915 was very low. CONCLUSIONS: The recommended oral diflomotecan dose for Phase II studies is 0.27 mg/day x 5 every 3 weeks. This regimen is convenient and generally well tolerated with a favorable pharmacokinetic profile and high but variable bioavailability.

Administration, Oral↗
PubMed2003

Irinotecan pathway genotype analysis to predict pharmacokinetics.

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.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Phase I and pharmacokinetic study of brostallicin (PNU-166196), a new DNA minor-groove binder, administered intravenously every 3 weeks to adult patients with metastatic cancer.

PURPOSE: Brostallicin (PNU-166196) is a cytotoxic agent that binds to the minor groove of DNA with significant antitumor activity in preclinical studies. This trial was designed to determine the maximum tolerated dose, the toxicity profile, and the pharmacokinetics of Brostallicin in cancer patients. EXPERIMENTAL DESIGN: Patients were treated with escalating doses of Brostallicin ranging from 0.85 to 15 mg/m(2) administered as a 10-min i.v. infusion every 3 weeks. Blood samples for pharmacokinetic analysis were collected during the first and second course, and analyzed by liquid-chromatography with tandem-mass spectrometric detection. RESULTS: Twenty-seven evaluable patients received a total of 73 courses. Grade 4 neutropenia was the only dose-limiting toxicity at 12.5 mg/m(2), whereas grade 4 thrombocytopenia (1 patient) and grade 4 neutropenia (2 patients) were the dose-limiting toxicities at 15 mg/m(2). Other side effects, including thrombocytopenia and nausea, were generally mild. The maximum tolerated dose was defined at 10 mg/m(2). The clearance and terminal half-life of Brostallicin were dose-independent, with mean (+/-SD) values of 9.33 +/- 2.38 liters/h/m(2) and 4.69 +/- 1.88 h, respectively. There was no significant accumulation of Brostallicin with repeated administration. Significant relationships were observed between systemic exposure to Brostallicin and neutrophil counts at nadir. One partial response was observed in a patient with a gastrointestinal stromal tumor. CONCLUSION: Brostallicin was found to be well tolerated, with neutropenia being the principal toxicity. The recommended dose for additional evaluation in this schedule is 10 mg/m(2).

Adult↗
PubMed2003

Randomized cross-over evaluation of body-surface area-based dosing versus flat-fixed dosing of paclitaxel.

PURPOSE: Despite dose calculation using body-surface area (BSA), pharmacokinetics of most anticancer drugs show wide interindividual variability. In this study, we evaluated the role of BSA in paclitaxel disposition. PATIENTS AND METHODS: Paclitaxel pharmacokinetics were prospectively studied in 12 patients that were treated in a randomized cross-over design with paclitaxel (3-hour infusion at a 3-week interval) at 175 mg/m2 in cycle 1 (A) and a flat-fixed dose of 300 mg in cycle 2 (B), or vice versa. Blood samples were collected up to 24 hours after dosing and analyzed for total and unbound paclitaxel. RESULTS: The area under the curves (AUC) of unbound paclitaxel were similar in both dosing groups, with mean values +/- SD (A v B) of 1.34 +/- 0.158 versus 1.30 +/- 0.329 microM x h, indicating that BSA-based dosing reduced the coefficient of variation by 53.3%. Unbound and total paclitaxel clearance was also significantly related to various body-size measures, including BSA (R > or = 0.617; P < or =.033), weight (R >or = 0.621; P < or =.031), and lean-body mass (r > or = 0.630; P < or = .028). We hypothesize that this is caused by the association of paclitaxel in the circulation with Cremophor EL, the distribution of which is linked to total blood volume, and thus to BSA. CONCLUSION: This study indicates that paclitaxel disposition is significantly related to BSA. This provides a pharmacokinetic rationale for BSA-based dosing of this drug.

Adult↗
PubMed2003

Clinical pharmacokinetics of unbound docetaxel: role of polysorbate 80 and serum proteins.

OBJECTIVE: Our objectives were to study the extent of docetaxel binding to plasma in the presence and absence of its excipient, polysorbate 80 (Tween 80; Imperial Chemical Industries PLC, London, United Kingdom), in vitro and to evaluate the pharmacokinetics of unbound docetaxel in vivo. METHODS: Equilibrium dialysis was used for determination of the fraction unbound (f(u)) docetaxel and was applied to study the pharmacokinetic behavior of unbound docetaxel in 23 patients with cancer receiving an intravenous infusion of the drug formulated in polysorbate 80 (Taxotere; Aventis Pharma SA, Vitry-sur-Seine Cedex, France). RESULTS: Polysorbate 80, added at clinically relevant concentrations (up to 1.0 microL/mL), increased f(u) in vitro by 13% (7.84% +/- 0.0752% versus 6.95% +/- 0.0678%, P <.00001). Similarly, f(u) calculated on the basis of the observed area under the plasma concentration-time curve (AUC) values [f(u)(AUC)] in vivo was 12% higher than f(u) in pretreatment samples [f(u)(pre)] (6.00% +/- 1.03% versus 5.49% +/- 1.01%, P =.038). Of various serum proteins evaluated, only alpha(1)-acid glycoprotein was significantly related to f(u) (P <.0018), with higher f(u) in the presence of lower protein levels. Total docetaxel clearance was related to alpha(1)-acid glycoprotein (R(2) = 0.13, P =.058), f(u)(pre) (R(2) = 0.15, P =.039), and f(u)(AUC) (R(2) = 0.29, P =.0048). CONCLUSION: This study demonstrates that the plasma binding of docetaxel is influenced by both alpha(1)-acid glycoprotein and its formulation vehicle. Further investigation is required to resolve the potential clinical significance of these observations.

Adult↗
PubMed2003

Clinical trial design for target specific anticancer agents.

Recently a large number of new anticancer agents targeting specifically one or more of the extracellular, transmembrane, or intracellular (but extranuclear) processes involved in malignant transformation of cells or carcinogenesis have been developed. These agents show target specificity, predominantly resulting in growth inhibition in tumor models and less frequently in tumor regression, acting in a cytostatic rather than a cytotoxic way. In addition, based on their specific mechanism of action, these target specific agents are expected to have a more favorable toxicity profile. In exploring new anticancer agents, phase I studies generally focus on toxicity and are primarily designed to describe dose limiting toxicity and to determine the maximum tolerated dose and the dose recommended for phase II studies. These phase II studies are subsequently performed in small groups of patients using the percentage tumor regression to screen for anticancer efficacy. Due to the anticipated low toxicity profile and the mainly growth inhibiting activity of target specific agents, the design of phase I and II studies involving these agents will have to be adapted in several ways. It is emphasized that, although it is helpful to distinguish cytotoxic from cytostatic anticancer agents, this dichotomy can be a simplification. In this paper, we will discuss important issues that will have to be faced when developing clinical trials with these agents and we will specifically translate this into the already known concepts of trial design exploring cytotoxic and cytostatic agents.

Animals↗
PubMed2003

Effect of valspodar on the pharmacokinetics of unbound paclitaxel.

The aim of this multicenter study was to determine whether valspodar (Amdray; code designation, SDZ PSC 833), a potent P-glycoprotein (P-gp) inhibitor, affects the pharmacokinetics of unbound paclitaxel (Cu). Data were obtained from 31 patients with advanced breast cancer. Thirteen patients were treated with paclitaxel alone (3-h infusion at 175 mg/m2) and another 18 received paclitaxel (3-h infusion at 70 mg/m2) in combination with a 21-day cycle of oral valspodar (5 mg/kg given four times a day) starting 1 day before administration of paclitaxel. Serial blood samples were taken in the first course and Cu in plasma determined using equilibrium dialysis with a [G-3H]paclitaxel tracer. The apparent clearance of Cu was not significantly different between the two groups, with mean +/- standard deviation (+/- SD) values of 230 +/- 56.0 and 202 +/- 49.9 L/h/m2 in the absence and presence of valspodar, respectively (P = 0.17). The volume of Cu distribution was slightly larger in the presence of valspodar (1160 +/- 474 vs. 1620 +/- 552 L/m2; P = 0.025), which contributed to a minor difference in the terminal disposition half-life (6.12 +/- 3.42 vs. 8.50 +/- 2.06 h; P = 0.028). These data indicate that (i) valspodar lacks the significant interaction with paclitaxel observed previously with other P-gp modulators, (ii) the majority of the increased toxicity of the combination does not appear to be attributable to increased levels of Cu, and (iii) provide further evidence of the conjecture that the plasma concentration of paclitaxel may not be an appropriate measure to monitor the impact of P-gp inhibition.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Red blood cells: a neglected compartment in topotecan pharmacokinetic analysis.

Previously, a gender dependency of topotecan was found in the pharmacokinetics in the plasma compartment. Here, we prospectively studied the red blood cell (RBC) partitioning of topotecan and evaluated its consequences for overall drug disposition. Blood samples were obtained from 12 patients receiving cisplatin followed by i.v. topotecan. Topotecan pharmacokinetic analysis was performed in whole blood, plasma and RBCs. Significantly slower clearance was noted in females (n=7) compared to males (n=5) for lactone and total topotecan in plasma (p<0.0001), and for total drug in RBCs (p=0.027), but not in whole blood. In addition, no gender-dependent differences were observed in the terminal half-lives of topotecan in any of the compartments. The area under the curve ratios for RBC total to plasma lactone were 2.53+/-0.0640 and 2.13+/-0.442 in males and females, respectively. Hence, topotecan displays preferential affinity for RBCs compared to plasma, although these cells do not act as a depot in which drug accumulates over time. RBCs thus play a principal role in the distribution kinetics of topotecan and have a major impact on its plasma pharmacokinetics. The data warrant a change from current practice in pharmacokinetic studies with this agent and provide further evidence that, in general, the choice of the appropriate assay matrix should be rationally based.

Adult↗
PubMed2003

Distribution of paclitaxel in plasma and cerebrospinal fluid.

Our objective was to assess the distribution of paclitaxel in plasma and cerebrospinal fluid (CSF) in a cancer patient, and evaluate the role of the formulation vehicle Cremophor EL (CrEL) in drug distribution. Analysis of paclitaxel concentrations in CSF was performed using a triple-quadrupole mass spectrometric assay with electrospray ionization. Total and unbound paclitaxel levels in plasma were measured by liquid chromatography and equilibrium dialysis, respectively, and CrEL concentrations were determined by a colorimetric dye-binding microassay. Clinical samples were obtained from a 54-year-old female with breast cancer receiving a weekly regimen of paclitaxel (dose 60 mg/m2). The disposition of total paclitaxel in plasma was characterized by a bi-exponential elimination (terminal half-life 9.17 h) and a total clearance of 19.4 l/h/m2. The fraction of unbound paclitaxel in plasma ranged from 7.6 to 12.4% (unbound drug CL 176 l/h/m2). The plasma clearance of CrEL was 0.332 l/h/m2, whereas CrEL levels were undetectable in CSF (below 0.5 microl/ml). Concentrations of paclitaxel in CSF (range 45.5-162 pg/ml) and unbound CSF:unbound plasma concentration ratios (range 0.093-9.53%) progressively increased up to 24 h, with a mean unbound drug fraction in CSF of 84+/-3.6% (range 81-88%). These findings indicate that there is substantial distribution of paclitaxel to CSF. Since the fraction of unbound paclitaxel is different between plasma and CSF, measurement of unbound paclitaxel is required to accurately assess the extent of drug penetration.

Antineoplastic Agents, Phytogenic↗
PubMed2003

Role of imatinib mesylate (Gleevec/Glivec) in gastrointestinal stromal tumors.

Gastrointestinal stromal tumors are soft tissue sarcomas of the gastrointestinal tract that originate from mesenchymal cells. Advances in the systemic therapy of gastrointestinal stromal tumors are highlighted by the rapid development and approval of the molecularly targeted therapy imatinib mesylate (Gleevec/Glivec). Mutations of the KIT gene are known to be present in most gastrointestinal stromal tumors and result in gain of function, with permanent activation of the expressed KIT receptor in the absence of binding of the stem cell factor ligand. Imatinib is the first rationally designed selective inhibitor of specific protein tyrosine kinases, including KIT. Inhibiting the downstream signaling of KIT switches the cell balance into apoptosis. Although complete responses have seldom been seen up until now, imatinib has proven to be extremely effective in the treatment of patients with unresectable and/or metastatic gastrointestinal stromal tumors.

Animals↗
PubMed2003

Pharmacological effects of formulation vehicles : implications for cancer chemotherapy.

The non-ionic surfactants Cremophor EL (CrEL; polyoxyethyleneglycerol triricinoleate 35) and polysorbate 80 (Tween) 80; polyoxyethylene-sorbitan-20-monooleate) are widely used as drug formulation vehicles, including for the taxane anticancer agents paclitaxel and docetaxel. A wealth of recent experimental data has indicated that both solubilisers are biologically and pharmacologically active compounds, and their use as drug formulation vehicles has been implicated in clinically important adverse effects, including acute hypersensitivity reactions and peripheral neuropathy.CrEL and Tween 80 have also been demonstrated to influence the disposition of solubilised drugs that are administered intravenously. The overall resulting effect is a highly increased systemic drug exposure and a simultaneously decreased clearance, leading to alteration in the pharmacodynamic characteristics of the solubilised drug. Kinetic experiments revealed that this effect is primarily caused by reduced cellular uptake of the drug from large spherical micellar-like structures with a highly hydrophobic interior, which act as the principal carrier of circulating drug. Within the central blood compartment, this results in a profound alteration of drug accumulation in erythrocytes, thereby reducing the free drug fraction available for cellular partitioning and influencing drug distribution as well as elimination routes. The existence of CrEL and Tween 80 in blood as large polar micelles has also raised additional complexities in the case of combination chemotherapy regimens with taxanes, such that the disposition of several coadministered drugs, including anthracyclines and epipodophyllotoxins, is significantly altered. In contrast to the enhancing effects of Tween 80, addition of CrEL to the formulation of oral drug preparations seems to result in significantly diminished drug uptake and reduced circulating concentrations. The drawbacks presented by the presence of CrEL or Tween 80 in drug formulations have instigated extensive research to develop alternative delivery forms. Currently, several strategies are in progress to develop Tween 80- and CrEL-free formulations of docetaxel and paclitaxel, which are based on pharmaceutical (e.g. albumin nanoparticles, emulsions and liposomes), chemical (e.g. polyglutamates, analogues and prodrugs), or biological (e.g. oral drug administration) strategies. These continued investigations should eventually lead to more rational and selective chemotherapeutic treatment.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2003

Disposition of docosahexaenoic acid-paclitaxel, a novel taxane, in blood: in vitro and clinical pharmacokinetic studies.

PURPOSE: Docosahexaenoic acid-paclitaxel is as an inert prodrug composed of the natural fatty acid DHA covalently linked to the C2'-position of paclitaxel (M. O. Bradley et al., Clin. Cancer Res., 7: 3229-3238, 2001). Here, we examined the role of protein binding as a determinant of the pharmacokinetic behavior of DHA-paclitaxel. EXPERIMENTAL DESIGN: The blood distribution of DHA-paclitaxel was studied in vitro using equilibrium dialysis and in 23 cancer patients receiving the drug as a 2-h i.v. infusion (dose, 200-1100 mg/m(2)). RESULTS: In vitro, DHA-paclitaxel was found to bind extensively to human plasma (99.6 +/- 0.057%). The binding was concentration independent (P = 0.63), indicating a nonspecific, nonsaturable process. The fraction of unbound paclitaxel increased from 0.052 +/- 0.0018 to 0.055 +/- 0.0036 (relative increase, 6.25%; P = 0.011) with an increase in DHA-paclitaxel concentration (0-1000 microg/ml), suggesting weakly competitive drug displacement from protein-binding sites. The mean (+/- SD) area under the curve of unbound paclitaxel increased nonlinearly with dose from 0.089 +/- 0.029 microg.h/ml (at 660 mg/m(2)) to 0.624 +/- 0.216 microg.h/ml (at 1100 mg/m(2)), and was associated with the dose-limiting neutropenia in a maximum-effect model (R(2) = 0.624). A comparative analysis indicates that exposure to Cremophor EL and unbound paclitaxel after DHA-paclitaxel (at 1100 mg/m(2)) is similar to that achieved with paclitaxel on clinically relevant dose schedules. CONCLUSIONS: Extensive binding to plasma proteins may explain, in part, the unique pharmacokinetic profile of DHA-paclitaxel described previously with a small volume of distribution ( approximately 4 liters) and slow systemic clearance ( approximately 0.11 liters/h).

Adult↗