Physiologically-based pharmacokinetic model predictions of inter-ethnic differences in imatinib pharmacokinetics and dosing regimens.

AIMS: This study implements a physiologically-based pharmacokinetic (PBPK) modelling approach to investigate inter-ethnic differences in imatinib pharmacokinetics and dosing regimens. METHODS: A PBPK model of imatinib was built in the Simcyp Simulator (version 17) integrating in vitro drug metabolism and clinical pharmacokinetic data. The model accounts for ethnic differences in body size and abundance of drug-metabolising enzymes and proteins involved in imatinib disposition. Utility of this model for prediction of imatinib pharmacokinetics was evaluated across different dosing regimens and ethnic groups. The impact of ethnicity on imatinib dosing was then assessed based on the established range of trough concentrations (Css,min ). RESULTS: The PBPK model of imatinib demonstrated excellent predictive performance in describing pharmacokinetics and the attained Css,min in patients from different ethnic groups, shown by prediction differences that were within 1.25-fold of the clinically-reported values in published studies. PBPK simulation suggested a similar dose of imatinib (400-600 mg/d) to achieve the desirable range of Css,min (1000-3200 ng/mL) in populations of European, Japanese and Chinese ancestry. The simulation indicated that patients of African ancestry may benefit from a higher initial dose (600-800 mg/d) to achieve imatinib target concentrations, due to a higher apparent clearance (CL/F) of imatinib compared to other ethnic groups; however, the clinical data to support this are currently limited. CONCLUSION: PBPK simulations highlighted a potential ethnic difference in the recommended initial dose of imatinib between populations of European and African ancestry, but not populations of Chinese and Japanese ancestry.

Physiologically based pharmacokinetic model predictions of natural product-drug interactions between goldenseal, berberine, imatinib and bosutinib.

PURPOSE: This study implements a physiologically based pharmacokinetic (PBPK) modelling approach to predict the effect of hydrastine and berberine, two major alkaloids present in goldenseal extract, on pharmacokinetics of imatinib and bosutinib. METHODS: PBPK models of hydrastine and berberine were developed in the Simcyp Simulator (version 17), integrating prior in vitro knowledge and published clinical pharmacokinetic data. The models account for reversible and irreversible (mechanism-based) inhibition of CYP3A enzymes as well as inhibition of the P-glycoprotein transporter. Inhibitory potencies of hydrastine and berberine on imatinib and bosutinib were estimated based on in vitro inhibition of metabolite formation. RESULTS: The PBPK models provided reliable estimates on the magnitude of interactions due to co-administration of goldenseal extract or high-dose berberine on substrates of CYP3A enzymes (midazolam, indinavir and cyclosporine) and P-glycoprotein (digoxin). PBPK simulations predicted a moderate twofold increase (5th to 95th percentiles of prediction of 1.4-3.1) in systemic exposure (AUC) of bosutinib when co-administered with clinically relevant doses of goldenseal extract. A high dose of berberine (300 mg thrice daily) was also expected to affect bosutinib exposure, albeit to a lesser extent than that predicted with goldenseal (AUC ratio of 1.3, 5th to 95th percentile: 1.1-1.6). Conversely, the corresponding effects on imatinib exposure are unlikely to be of clinical importance (predicted AUC ratios of 1.0-1.2). CONCLUSION: PBPK model-based predictions highlighted potential clinically significant interactions between goldenseal extract and bosutinib, but not imatinib. Dose adjustment may need to be considered if co-administration is desirable. These findings should be confirmed with optimally designed controlled drug interaction studies.

Is there scope for better individualisation of anthracycline cancer chemotherapy?

Anthracyclines are used to treat solid and haematological cancers, particularly breast cancers, lymphomas and childhood cancers. Myelosuppression and cardiotoxicity are the primary toxicities that limit treatment duration and/or intensity. Cardiotoxicity, particularly heart failure, is a leading cause of morbidity and mortality in cancer survivors. Cumulative anthracycline dose is a significant predictor of cardiotoxicity risk, suggesting a role for anthracycline pharmacokinetic variability. Population pharmacokinetic modelling in children has shown that doxorubicin clearance in the very young is significantly lower than in older children, potentially contributing to their higher risk of cardiotoxicity. A model of doxorubicin clearance based on body surface area and age offers a patient-centred dose-adjustment strategy that may replace the current disparate initial-dose selection tools, providing a rational way to compensate for pharmacokinetic variability in children aged <7 years. Population pharmacokinetic models in adults have not adequately addressed older ages, obesity, hepatic and renal dysfunction, and potential drug-drug interactions to enable clinical application. Although candidate gene and genome-wide association studies have investigated relationships between genetic variability and anthracycline pharmacokinetics or clinical outcomes, there have been few clinically significant reproducible associations. Precision-dosing of anthracyclines is currently hindered by lack of clinically useful pharmacokinetic targets and models that predict cumulative anthracycline exposures. Combined with known risk factors for cardiotoxicity, the use of advanced echocardiography and biomarkers, future validated pharmacokinetic targets and predictive models could facilitate anthracycline precision dosing that truly maximises efficacy and provides individualised early intervention with cardioprotective therapies in patients at risk of cardiotoxicity.

Potential for pharmacokinetic interactions between Schisandra sphenanthera and bosutinib, but not imatinib: in vitro metabolism study combined with a physiologically-based pharmacokinetic modelling approach.

AIMS: This study aimed to investigate the potential interaction between Schisandra sphenanthera, imatinib and bosutinib combining in vitro and in silico methods. METHODS: In vitro metabolism of imatinib and bosutinib using recombinant enzymes and human liver microsomes were investigated in the presence and absence of Schisandra lignans. Physiologically-based pharmacokinetic (PBPK) models for the lignans accounting for reversible and mechanism-based inhibitions and induction of CYP3A enzymes were built in the Simcyp Simulator (version 17) and evaluated for their capability to predict interactions with midazolam and tacrolimus. Their potential effect on systemic exposures of imatinib and bosutinib were predicted using PBPK in silico simulations. RESULTS: Schisantherin A and schisandrol B, but not schisandrin A, potently inhibited CYP3A4-mediated metabolism of imatinib and bosutinib. All three compounds showed a strong reversible inhibition on CYP2C8 enzyme with ki of less than 0.5 µmol L-1 . The verified PBPK models were able to describe the increase in systemic exposure of midazolam and tacrolimus due to co-administration of S. sphenanthera, consistent with the reported changes in the corresponding clinical interaction study (AUC ratio of 2.0 vs 2.1 and 2.4 vs 2.1, respectively). The PBPK simulation predicted that at recommended dosing regimens of S. sphenanthera, co-administration would result in an increase in bosutinib exposure (AUC ratio 3.0) but not in imatinib exposure. CONCLUSION: PBPK models for Schisandra lignans were successfully developed. Interaction between imatinib and Schisandra lignans was unlikely to be of clinical importance. Conversely, S. sphenanthera at a clinically-relevant dose results in a predicted three-fold increase in bosutinib systemic exposure.

Physiologically-Based Pharmacokinetic Predictions of the Effect of Curcumin on Metabolism of Imatinib and Bosutinib: In Vitro and In Vivo Disconnect.

PURPOSE: This study aimed to investigate the potential pharmacokinetic interactions between curcumin, imatinib and bosutinib, combining In Vitro and in silico methods. METHODS: In Vitro metabolism of imatinib and bosutinib were investigated in pooled human liver microsomes and recombinant CYP3A4 enzyme in the presence and absence of curcumin and curcumin glucuronide using an LC-MS/MS assay for N-desmethyl metabolites. A physiologically-based pharmacokinetic (PBPK) model for curcumin formulated as solid lipid nanoparticles (SLN) was constructed using In Vitro glucuronidation kinetics and published clinical pharmacokinetic data. The potential effects of curcumin coadministration on systemic exposures of imatinib and bosutinib were predicted in silico using PBPK simulations. RESULTS: Curcumin demonstrated potent reversible inhibition of cytochrome P450 (CYP)3A4-mediated N-demethylation of imatinib and bosutinib and CYP2C8-mediated metabolism of imatinib with inhibitory constants (ki,u) of ≤1.5 µmol. L-1. A confirmatory In Vitro study with paclitaxel, the 6α-hydroxylation of which is exclusively mediated by CYP2C8, was consistent with a potent inhibition of this enzyme by curcumin. Curcumin glucuronide also inhibited both CYP enzymes In Vitro, albeit to a lesser extent than that of curcumin. PBPK model simulations predicted that at recommended dosing regimens of SLN curcumin, coadministration would result in an increase in systemic exposures of imatinib and bosutinib of up to only 10%. CONCLUSION: A PBPK model for curcumin in a SLN formulation was successfully developed. Although curcumin possesses a strong In Vitro inhibitory activity towards CYP3A4 and CYP2C8 enzymes, its interactions with imatinib and bosutinib were unlikely to be of clinical importance due to curcumin's poor bioavailability.

Optimization of a clofarabine-based drug combination regimen for the preclinical evaluation of pediatric acute lymphoblastic leukemia.

BACKGROUND: The aim of this study was to improve the predictive power of patient-derived xenografts (PDXs, also known as mouse avatars) to more accurately reflect outcomes of clofarabine-based treatment in pediatric acute lymphoblastic leukemia (ALL) patients. PROCEDURE: Pharmacokinetic (PK) studies were conducted using clofarabine at 3.5 to 15 mg/kg in mice. PDXs were established from relapsed/refractory ALL patients who exhibited good or poor responses to clofarabine. PDX engraftment and response to clofarabine (either as a single agent or in combinations) were assessed based on stringent objective response measures modeled after the clinical setting. RESULTS: In naïve immune-deficient NSG mice, we determined that a clofarabine dose of 3.5 mg/kg resulted in systemic exposures equivalent to those achieved in pediatric ALL patients treated with clofarabine-based regimens. This dose was markedly lower than the doses of clofarabine used in previously reported preclinical studies (typically 30-60 mg/kg) and, when scheduled consistent with the clinical regimen (daily × 5), resulted in 34-fold lower clofarabine exposures. Using a well-tolerated clofarabine/etoposide/cyclophosphamide combination regimen, we then found that the responses of PDXs better reflected the clinical responses of the patients from whom the PDXs were derived. CONCLUSIONS: This study has identified an in vivo clofarabine treatment regimen that reflects the clinical responses of relapsed/refractory pediatric ALL patients. This regimen could be used prospectively to identify patients who might benefit from clofarabine-based treatment. Our findings are an important step toward individualizing prospective patient selection for the use of clofarabine in relapsed/refractory pediatric ALL patients and highlight the need for detailed PK evaluation in murine PDX models.

Wnt receptor gene FZD1 was associated with schizophrenia in genome-wide SNP analysis of the Australian Schizophrenia Research Bank cohort.

OBJECTIVES: Large-scale genetic analysis of common variation in schizophrenia has been a powerful approach to understanding this complex but highly heritable psychotic disorder. To further investigate loci, genes and pathways associated more specifically in the well-characterized Australian Schizophrenia Research Bank cohort, we applied genome-wide single-nucleotide polymorphism analysis in these three annotation categories. METHODS: We performed a case-control genome-wide association study in 429 schizophrenia samples and 255 controls. Post-genome-wide association study analyses were then integrated with genomic annotations to explore the enrichment of variation at the gene and pathway level. We also examine candidate single-nucleotide polymorphisms with potential function within expression quantitative trait loci and investigate overall enrichment of variation within tissue-specific functional regulatory domains of the genome. RESULTS: The strongest finding (p = 2.01 × 10-6, odds ratio = 1.82, 95% confidence interval = [1.42, 2.33]) in genome-wide association study was with rs10252923 at 7q21.13, downstream of FZD1 (frizzled class receptor 1). While this did not stand alone after correction, the involvement of FZD1 was supported by gene-based analysis, which exceeded the threshold for genome-wide significance (p = 2.78 × 10-6). CONCLUSION: The identification of FZD1, as an independent association signal at the gene level, supports the hypothesis that the Wnt signalling pathway is altered in the pathogenesis of schizophrenia and may be an important target for therapeutic development.

The role of solute carrier (SLC) transporters in actinomycin D pharmacokinetics in paediatric cancer patients.

BACKGROUND: Actinomycin D is used for treatment of paediatric cancers; however, a large inter-patient pharmacokinetic (PK) variability and hepatotoxicity are significant limitations to its use and warrant further investigation. Elimination of actinomycin D may be mediated by transporters, as the drug does not seem to undergo significant metabolism. We investigated the role of solute carrier (SLC) transporters in actinomycin D PK. METHODS: Fourteen key SLCs were screened through probe substrate uptake inhibition by actinomycin D in HEK293 cells. Uptake of actinomycin D was further studied in candidate SLCs by measuring intracellular actinomycin D using a validated LCMS assay. Pharmacogenetic analysis was conducted for 60 patients (Clinical trial: NCT00900354), who were genotyped for SNPs for OAT4 and PEPT2. RESULTS: OAT4, OCT2, OCT3 and PEPT2 showed significantly lower probe substrate uptake (mean ± SD 75.0 ± 3.5% (p < 0.0001), 74.8 ± 11.2% (p = 0.001), 81.2 ± 14.0% (p = 0.0083) and 70.7 ± 5.7% (p = 0.0188)) compared to that of control. Intracellular accumulation of actinomycin D was greater compared to vector control in OAT4-transfected cells by 1.5- and 1.4-fold at 10 min (p = 0.01) and 20 min (p = 0.03), and in PEPT2-transfected cells by 1.5- and 1.7-fold at 10 min (p = 0.047) and 20 min (p = 0.043), respectively. Subsequent clinical study did not find a significant association between OAT4 rs11231809 and PEPT2 rs2257212 genotypes, and actinomycin D PK parameters such as clearance (CL) and volume of distribution (Vd). CONCLUSION: Transport of actinomycin D was mediated by OAT4 and PEPT2 in vitro. There was a lack of clinical significance of OAT4 and PEPT2 genotypes as predictors of actinomycin D disposition in paediatric cancer patients.

A population pharmacokinetic model of AT9283 in adults and children to predict the maximum tolerated dose in children with leukaemia.

AIMS: AT9283 is used to treat patients with solid tumours and patients with leukaemia. However, the maximum tolerated dose (MTD) for children with leukaemia remains unknown due to early termination of the Phase I trial. The aim of this study was to develop a population model of AT9283 to describe the pharmacokinetics in adults and children and to estimate the MTD in children with leukaemia. METHODS: Data from Phase I dose-escalation studies in adults and children were used to build a population pharmacokinetic model (NONMEM v7.3). Potential covariates investigated included body weight, body surface area (BSA), glomerular filtration rate (GFR), age and sex. Model-derived area under the concentration-time curve was used to investigate the relationship between dose and exposure in adults and children. RESULTS: The plasma concentrations of AT9283 (n = 1770) from 92 patients (53 adults, 39 children) were used to build a two-compartment model with all pharmacokinetic parameters scaled using body weight. Renal function (GFR), but not BSA, was a significant covariate for the clearance of AT9283. In children with leukaemia (median weight 16 kg), a flat dose of 500 mg 72 h-1 provided similar drug exposures at the MTD as the adult population. The estimated MTD for children with leukaemia, therefore, is 30 mg kg-1  72 h-1 . CONCLUSION: For adults, GFR was a significant predictor of clearance, whilst body-weight based dosing was more useful than BSA in determining the drug exposure in children. The MTD was estimated to be 30 mg kg-1  72 h-1 children with leukaemia.

High-resolution imaging for the detection and characterisation of circulating tumour cells from patients with oesophageal, hepatocellular, thyroid and ovarian cancers.

Interest has increased in the potential role of circulating tumour cells in cancer management. Most cell-based studies have been designed to determine the number of circulating tumour cells in a given volume of blood. Ability to understand the biology of the cancer cells would increase the clinical potential. The purpose of this study was to develop and validate a novel, widely applicable method for detection and characterisation of circulating tumour cells. Cells were imaged with an ImageStream(X) imaging flow cytometer which allows detection of expression of multiple biomarkers on each cell and produces high-resolution images. Depletion of haematopoietic cells was by red cell lysis, leukocyte common antigen CD45 depletion and differential centrifugation. Expression of epithelial cell adhesion molecule, cytokeratins, tumour-type-specific biomarkers and CD45 was detected by immunofluorescence. Nuclei were identified with DAPI or DRAQ5 and brightfield images of cells were collected. The method is notable for the dearth of cell damage, recoveries greater than 50%, speed and absence of reliance on the expression of a single biomarker by the tumour cells. The high-quality images obtained ensure confidence in the specificity of the method. Validation of the methodology on samples from patients with oesophageal, hepatocellular, thyroid and ovarian cancers confirms its utility and specificity. Importantly, this adaptable method is applicable to all tumour types including those of nonepithelial origin. The ability to measure simultaneously the expression of multiple biomarkers will facilitate analysis of the cancer cell biology of individual circulating tumour cells.

Imagestream detection and characterisation of circulating tumour cells - A liquid biopsy for hepatocellular carcinoma?

BACKGROUND & AIMS: The lack of progress in developing and delivering new therapies for hepatocellular carcinoma (HCC) is in part attributed to the risk related avoidance of tumour biopsy at diagnosis. Circulating tumour cells (CTCs) are a potential source of tumour tissue that could aid biological or biomarker research, treatment stratification and monitoring. METHODS: An imaging flow cytometry method, using immunofluorescence of cytokeratin, EpCAM, AFP, glypican-3 and DNA-PK together with analysis of size, morphology and DNA content, for detection of HCC CTCs was developed and applied to 69 patient and 31 control samples. The presence of CTCs as a prognostic indicator was assessed in multivariate analyses encompassing recognised prognostic parameters. RESULTS: Between 1 and 1642 CTCs were detected in blood samples from 45/69 HCC patients compared to 0/31 controls. CTCs positive for the epithelial markers cytokeratin and EpCAM were detected in 29% and 18% of patients respectively, while an additional 28% of patients had CTCs negative for all markers other than size and evidence of hyperploidy. CTC number correlated significantly with tumour size and portal vein thrombosis (PVT). The median survival of patients with >1 CTC was 7.5months versus >34months for patients with <1 CTC (p<0.001, log-rank), with significance retained in a multivariate analysis (HR 2.34, 95% CI 1.005-5.425, p=0.049) including tumour size and PVT. CONCLUSIONS: The use of multiple parameters enhanced HCC CTC detection sensitivity, revealing biological associations and predictive biomarker potential that may be able to guide stratified medicine decisions and future research. LAY SUMMARY: Characteristics of tumour tissues can be used to predict outcomes for individual patients with cancer, as well as help to choose their best treatment. Biopsy of liver cancers carries risks, however, and is usually avoided. Some cancer cells enter the blood, and although they are very rare, we have developed a method of finding and characterising them in patients with liver cancer, which we hope will provide a low risk means of guiding treatment.

A Retinol Isotope Dilution Equation Predicts Both Group and Individual Total Body Vitamin A Stores in Adults Based on Data from an Early Postdosing Blood Sample.

BACKGROUND: Retinol isotope dilution (RID) is used to determine vitamin A total body stores (TBS) after an oral dose of a vitamin A stable isotope. The generally accepted prediction equation proposed by Olson's group in 1989 (Furr et al. Am J Clin Nutr 1989;49:713-6) includes factors related to dose absorption and retention, isotope equilibration in plasma compared with stores, catabolism during the mixing period, and the optimal time for measuring plasma isotope enrichment. OBJECTIVES: The objectives were 1) to develop a modified RID equation and identify an earlier sampling time for predicting TBS and 2) to improve prediction in individuals as well as groups. METHODS: To develop a modified RID equation, we used results of model-based compartmental analysis [the Simulation, Analysis and Modeling software (WinSAAM version 3.0.8; http://www.WinSAAM.org)] of plasma [13C10]retinol kinetic data from 32 previously studied, healthy young adults of European ancestry who had moderate vitamin A intakes and who ingested 2.95 µmol [13C10]retinyl acetate. RESULTS: We examined the time dependence of factors in the prediction equation related to absorption/retention (Fa) and isotope equilibration (S) and determined that 4 or 5 d postdosing was the optimal sampling time. TBS calculated by the equation TBS = Fa x S x (1/SAp), where SAp is plasma retinol specific activity (fraction of dose/µmol), were highly correlated with model-predicted TBS (r = 0.95 and 0.96 for 4 and 5 d, respectively; P < 0.001); predictions for individuals were also highly correlated (Rs = 0.94 and 0.94; P < 0.001). CONCLUSION: The equation TBS ≈ 0.5 × (1/SAp) accurately predicted vitamin A TBS in this group of 32 healthy young adults and its individual members with the use of data from 1 blood sample taken 4 d after isotope administration.

Plasma Retinol Kinetics and ß-Carotene Bioefficacy Are Quantified by Model-Based Compartmental Analysis in Healthy Young Adults with Low Vitamin A Stores.

BACKGROUND: Model-based compartmental analysis of data on plasma retinol kinetics after administration of labeled retinol provides unique information about whole-body vitamin A metabolism. If labeled ß-carotene is coadministered, its bioefficacy relative to the retinol reference dose can also be estimated. OBJECTIVES: The objectives were to model plasma retinol kinetics after administration of labeled preformed vitamin A and provitamin A ß-carotene and to determine relative ß-carotene bioefficacy. METHODS: We used the Simulation, Analysis and Modeling software (WinSAAM version 3.0.8; http://www.WinSAAM.org) to analyze previously collected data on plasma [13C10]- and [13C5]retinol kinetics for 14 d after oral administration of 1 mg [13C10]retinyl acetate and 2 mg [13C10]ß-carotene in oil to 30 healthy young adults of European ancestry [13 men, 17 women; mean ± SD age: 24.5 ± 4.2 y; mean ± SD body weight: 65.2 ± 10 kg; mean ± SD body mass index (in kg/m2): 22.5 ± 1.9] with moderate vitamin A intakes. RESULTS: A 6-component model provided the best fit to the data, including compartments for initial metabolism of vitamin A, plasma retinol, and extravascular vitamin A storage. The disposal rate was 6.7 ± 3.1 µmol/d, fractional catabolic rate was 6.0% ± 2.3%/d, and vitamin A stores were 123 ± 71 µmol. Relative ß-carotene bioefficacy, based on the ratio of the areas under the fraction of dose curves calculated by WinSAAM, averaged 13.5% ± 6.02% (retinol activity equivalents = 7.7:1.0 µg). Interindividual variation in relative ß-carotene bioefficacy was high (CV: 44%). CONCLUSIONS: Vitamin A kinetics in these young adults were best described by essentially the same model that had been previously developed by using data for older adults with higher vitamin A stores; differences in parameter values reflected differences in vitamin A status. Estimated ß-carotene bioefficacy was relatively low but similar to previously reported estimates obtained by graphical methods. This trial was registered at the UK Clinical Research Network as UKCRN 7413.

Development of a physiologically based pharmacokinetic model of actinomycin D in children with cancer.

AIMS: Use of the anti-tumour antibiotic actinomycin D is associated with development of hepatotoxicity, particularly in young children. A paucity of actinomycin D pharmacokinetic data make it challenging to develop a sound rationale for defining dosing regimens in younger patients. The study aim was to develop a physiologically based pharmacokinetic (PBPK) model using a combination of data from the literature and generated from experimental analyses. METHODS: Assays to determine actinomycin D Log P, blood:plasma partition ratio and ABCB1 kinetics were conducted. These data were combined with physiochemical properties sourced from the literature to generate a compound file for use within the modelling-simulation software Simcyp (version 14 release 1). For simulation, information was taken from two datasets, one from 117 patients under the age of 21 and one from 20 patients aged 16-48. RESULTS: The final model incorporated clinical renal and biliary clearance data and an additional systemic clearance value. The mean AUC0-26h of simulated subjects was within 1.25-fold of the observed AUC0-26h (84 ng h ml(-1) simulated vs. 93 ng h ml(-1) observed). For the younger age ranges, AUC predictions were within two-fold of observed values, with simulated data from six of the eight age/dose ranges falling within 15% of observed data. Simulated values for actinomycin D AUC0-26h and clearance in infants aged 0-12 months ranged from 104 to 115 ng h ml(-1) and 3.5-3.8 l h(-1) , respectively. CONCLUSIONS: The model has potential utility for prediction of actinomycin D exposure in younger patients and may help guide future dosing. However, additional independent data from neonates and infants is needed for further validation. Physiological differences between paediatric cancer patients and healthy children also need to be further characterized and incorporated into PBPK models.

An LC/MS/MS method for stable isotope dilution studies of ß-carotene bioavailability, bioconversion, and vitamin A status in humans.

Isotope dilution is currently the most accurate technique in humans to determine vitamin A status and bioavailability/bioconversion of provitamin A carotenoids such as ß-carotene. However, limits of MS detection, coupled with extensive isolation procedures, have hindered investigations of physiologically-relevant doses of stable isotopes in large intervention trials. Here, a sensitive liquid chromatography-tandem mass spectrometry (LC/MS/MS) analytical method was developed to study the plasma response from coadministered oral doses of 2 mg [(13)C10]ß-carotene and 1 mg [(13)C10]retinyl acetate in human subjects over a 2 week period. A reverse phase C18 column and binary mobile phase solvent system separated ß-carotene, retinol, retinyl acetate, retinyl linoleate, retinyl palmitate/retinyl oleate, and retinyl stearate within a 7 min run time. Selected reaction monitoring of analytes was performed under atmospheric pressure chemical ionization in positive mode at m/z 537→321 and m/z 269→93 for respective [(12)C]ß-carotene and [(12)C] retinoids; m/z 547→330 and m/z 274→98 for [(13)C10]ß-carotene and [(13)C5] cleavage products; and m/z 279→100 for metabolites of [(13)C10]retinyl acetate. A single one-phase solvent extraction, with no saponification or purification steps, left retinyl esters intact for determination of intestinally-derived retinol in chylomicrons versus retinol from the liver bound to retinol binding protein. Coadministration of [(13)C10]retinyl acetate with [(13)C10]ß-carotene not only acts as a reference dose for inter-individual variations in absorption and chylomicron clearance rates, but also allows for simultaneous determination of an individual's vitamin A status.

Interactions between natural products and cancer treatments: underlying mechanisms and clinical importance.

Natural products, also referred to as dietary supplements, complementary and alternative medicines, and health or food supplements are widely used by people living with cancer. These products are predominantly self-selected and taken concurrently with cancer treatments with the intention of improving quality of life, immune function and reducing cancer symptoms and treatment side effects. Concerns have been raised that concurrent use may lead to interactions resulting in adverse effects and unintended treatment outcomes. This review provides an overview of the mechanisms by which these interactions can occur and the current evidence about specific clinically important natural product-drug interactions. Clinical studies investigating pharmacokinetic interactions provide evidence that negative treatment outcomes may occur when Hypericum perforatum, Grapefruit, Schisandra sphenanthera, Curcuma longa or Hydrastis canadensis are taken concurrently with common cancer treatments. Conversely, pharmacodynamic interactions between Hangeshashinto (TJ-14) and some cancer treatments have been shown to reduce the side effects of diarrhoea and oral mucositis. In summary, research in this area is limited and requires further investigation.

Minimization of the preanalytical error in pharmacokinetic analyses and therapeutic drug monitoring: focus on IV drug administration.

BACKGROUND: The conduct of multicenter pharmacokinetic (PK) analyses for long-established drugs entails specific problems, because samples have to be obtained within daily clinical practice. Practices for intravenous (IV) drug administration vary between hospitals, including the use of different infusion devices, the use of infusion line systems with different line volumes, and different priming and rinsing procedures. METHODS: Variables of IV drug administration that could influence concentration data obtained in PK analyses were evaluated. Kinetics of drug delivery during initiation and cessation of IV infusions were simulated in vitro for a drop-counter and a syringe-driven infusion system at different flow rates. Furthermore, the percentages of the target drug dosage remaining in the infusion line after different rinsing periods were investigated in vitro and in clinical practice. RESULTS: Varying times required for the drug to migrate from the bag/syringe to the cannula and to reach a steady-state drug administration rate were observed. Time to steady state ranged from almost immediate to 48 minutes depending on the infusion system and flow rate. The longest times were seen for the drop-counter system at low flow rates and were associated with large drug concentration gradients in the infusion line, which makes it difficult to accurately determine start and end of the infusion. For most systems, when rinsing at the end of infusion was performed with once the volume of the infusion line, <5% of the total drug dosage was discarded. Larger variability was seen for slow infusion rates and small infusion volumes. CONCLUSIONS: The choice of the infusion apparatus, standardized infusion systems, and standardized operating procedures for drug administration are important when performing postmarketing PK analyses in multicentric studies.

Physiologically Based Pharmacokinetic Modeling Approaches for Patients With SARS-CoV-2 Infection: A Case Study With Imatinib.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which causes coronavirus disease 2019 (COVID-19), manifests as mild respiratory symptoms to severe respiratory failure and is associated with inflammation and other physiological changes. Of note, substantial increases in plasma concentrations of α1 -acid-glycoprotein and interleukin-6 have been observed among patients admitted to the hospital with advanced SARS-CoV-2 infection. A physiologically based pharmacokinetic (PBPK) approach is a useful tool to evaluate and predict disease-related changes on drug pharmacokinetics. A PBPK model of imatinib has previously been developed and verified in healthy people and patients with cancer. In this study, the PBPK model of imatinib was successfully extrapolated to patients with SARS-CoV-2 infection by accounting for disease-related changes in plasma α1 -acid-glycoprotein concentrations and the potential drug interaction between imatinib and dexamethasone. The model demonstrated a good predictive performance in describing total and unbound imatinib concentrations in patients with SARS-CoV-2 infection. PBPK simulations highlight that an equivalent dose of imatinib may lead to substantially higher total drug concentrations in patients with SARS-CoV-2 infection compared to that in patients with cancer, while the unbound concentrations remain comparable between the 2 patient populations. This supports the notion that unbound trough concentration is a better exposure metric for dose adjustment of imatinib in patients with SARS-CoV-2 infection, compared to the corresponding total drug concentration. Potential strategies for refinement and generalization of the PBPK modeling approach in the patient population with SARS-CoV-2 are also provided in this article, which could be used to guide study design and inform dose adjustment in the future.

Audit of Data Sharing by Pharmaceutical Companies for Anticancer Medicines Approved by the US Food and Drug Administration.

Importance: Emerging policies drafted by the pharmaceutical industry indicate that they will transparently share clinical trial data. These data offer an unparalleled opportunity to advance evidence-based medicine and support decision-making. Objective: To evaluate the eligibility of independent, qualified researchers to access individual participant data (IPD) from oncology trials that supported US Food and Drug Administration (FDA) approval of new anticancer medicines within the past 10 years. Design, Setting, and Participants: In this quality improvement study, a cross-sectional analysis was performed of pivotal clinical trials whose results supported FDA-approved anticancer medicines between January 1, 2011, and June 30, 2021. These trials' results were identified from product labels. Exposures: Eligibility for IPD sharing was confirmed by identification of a public listing of the trial as eligible for sharing or by receipt of a positive response from the sponsor to a standardized inquiry. Main Outcomes and Measures: The main outcome was frequency of IPD sharing eligibility. Reasons for data sharing ineligibility were requested and collated, and company-, drug-, and trial-level subgroups were evaluated and presented using χ2 tests and forest plots. Results: During the 10-year period examined, 115 anticancer medicines were approved by the FDA on the basis of evidence from 304 pharmaceutical industry-sponsored trials. Of these trials, 136 (45%) were eligible for IPD sharing and 168 (55%) were not. Data sharing rates differed substantially among industry sponsors, with the most common reason for not sharing trial IPD being that the collection of long-term follow-up data was still ongoing (89 of 168 trials [53%]). Of the top 10 anticancer medicines by global sales, nivolumab, pembrolizumab, and pomalidomide had the lowest eligibility rates for data sharing (<10% of trials). Conclusions and Relevance: There has been a substantial increase in IPD sharing for industry-sponsored oncology trials over the past 5 years. However, this quality improvement study found that more than 50% of queried trials for FDA-approved anticancer medicines were ineligible for IPD sharing. Data accessibility would be substantially improved if, at the time of FDA registration of a medicine, all data that support the registration were made available.

Two minor NQO1 and NQO2 alleles predict poor response of breast cancer patients to adjuvant doxorubicin and cyclophosphamide therapy.

OBJECTIVE: A SNP in the NQO1 gene has been implicated in the response of patients with breast cancer to anthracycline containing regimens. NQO1, and its homologue NQO2, share many substrates yet retain distinct functional differences, with NQO2 being a more permissive molecule for electron accepting substrates. We aimed to determine whether functional NQO2 variants are associated with altered response to adjuvant doxorubicin and cyclophosphamide therapy, with or without tamoxifen, in the treatment of breast cancer. METHODS: Genomic DNA samples from 227 women with early breast cancer were genotyped for NQO1 and NQO2 polymorphisms. All participants were treated with an AC adjuvant therapy regimen. The functional implications of NQO2 polymorphisms were validated in in-vitro ectopic expression models. RESULTS: The NQO1 SNP (rs1800566) was associated with a poorer outcome and a lower likelihood of having a treatment delay. Patients who had ER and PR negative disease and were wild type for both the NQO1 and an NQO2 SNP (rs1143684) had 100% 5-year overall survival compared with 88% for carriers of one minor allele and 70% for carriers of two or more minor alleles (P=0.018, log rank). Carriers of minor alleles of a triallelic NQO2 promoter polymorphism were more likely to be withdrawn from tamoxifen therapy prematurely due to intolerance (P=0.009, log rank). MCF-7 cells were sensitized to growth inhibition by doxorubicin and 4OH tamoxifen, but not cyclophosphamide, by ectopic expression of NQO2. CONCLUSION: This study suggests that both NQO1 and NQO2 modulate the efficacy of AC therapy and that NQO2 is associated with tamoxifen toxicity.