A constrained optimum adaptive design for dose finding in early phase clinical trials.

Recently, interest has grown in the development of dose-finding methods that consider both toxicity and efficacy as endpoints. Along with responses on these, the incorporation of pharmacokinetic (PK) data can be beneficial in terms of patients' safety and can also increase the efficiency of the design for finding the best dose for the next phase. In this paper, the maximum concentration (Cmax) is used as the PK measure guiding the dose selection. The ethically attractive approach, which is based on the probability of efficacy, is used as a dose optimisation criterion. At each stage of an adaptive trial, that dose is selected for which the criterion is maximised, subject to the constraints imposed on the Cmax and the probability of toxicity. The inter-patient variability of the PK model parameters is considered, and population D-optimal sampling time points for measuring the concentration of a drug in the blood are calculated. The method is illustrated with a one-compartment PK model with first-order absorption, with the parameters being assumed to be random. The Cox model for bivariate binary responses is employed to model the dose-response outcomes. The results of a simulation study for several plausible dose-response scenarios show a significant gain in the efficiency of the design, as well as a reduction in the proportion of toxic responses.

Model based dose personalization in clinical trials.

BACKGROUND AND OBJECTIVE: Personalized medicine is an important area of medical research which consists of designing therapies specifically for a patient or a group of patients. For drugs having a narrow therapeutic index or for vulnerable patients, methods such as therapeutic drug monitoring are used in a hospital setting to ensure that the blood concentration of the drug is maintained within a pre-decided range. However, such methods can not be used for drugs which are still in the developmental phase since, generally, insufficient information is available about the pharmacokinetic behaviour of the drug. METHODS: In this paper, we present a new methodology for explicit optimization of dose regimens during the course of the pharmacokinetic studies such that the resultant blood concentration of the drug in each subject is maintained around a desired target concentration or within a target range. RESULTS: We demonstrate that our algorithm is able to achieve the clinical objective of PK estimation while simultaneously individualizing the dose to every subject in the trial. Our algorithm computes dose regimens that, on average, have a relative efficiency of 97% with a standard deviation of less than 5%. The results show that the algorithm can be relied upon to ensure that the subjects in the trial are minimally over- and under-exposed to the test therapy. CONCLUSIONS: The proposed methodology can assist in ensuring correct dosing to each subject in a clinical trial so that each subject receives only the intended exposure to the drug while simultaneously estimating the PK profile of the drug. Our methodology can also be applied in randomized concentration-controlled trials where maintenance of the target concentration in the subjects is a fundamental requirement for conducting these trials.

Dose optimisation with simultaneous pharmacokinetic estimation in adaptive clinical trials.

Determination of the optimal dose is a critical objective in the drug developmental process. An optimal dose prevents over- and under-exposure to the treatment drug thereby facilitating superior patient experience and reduced costs to the healthcare system. In this paper, we present a method for model-based dose optimisation with simultaneous pharmacokinetic estimation of the model parameters. Multiple doses of the drug are considered and the objective is to maintain the blood concentration of the drug around a pre-decided target concentration. We consider an adaptive setting wherein the model parameters are estimated from the blood samples collected at D-optimal time points from all subjects enrolled so far in the trial. The estimated parameters are then used to determine the optimal dose regimen for the next cohort. This procedure continues until the condition of a pre-decided stopping rule is met. Simulation studies and sensitivity analysis are undertaken to validate the methodology. We also evaluate the performance of the methodology when carried out in a non-adaptive setting. A two-stage design is then presented which combines the advantages of the adaptive as well as the non-adaptive approach. We demonstrate that our methodology enables pharmacokinetic estimation and dose regimen optimisation simultaneously in an ethical and cost-effective manner protecting the subjects from the ill-effects of suboptimal dose regimens and economising the number of subjects required in the trial.

Combined criteria for dose optimisation in early phase clinical trials.

This paper aims to investigate whether any bridge is possible between so-called best intention and D-optimum designs. It introduces combined criteria for dose optimisation in seamless phase I/II adaptive clinical trials. Each of the optimality criteria considers efficacy and toxicity as endpoints and is based on the probability of a successful outcome and on the determinant of the Fisher information matrix for estimation of the dose-response parameters. In addition, one of the criteria incorporates penalties for choosing a toxic or inefficacious dose. Starting with the lowest dose, the adaptive design selects the dose for each subsequent cohort that maximises the respective defined criterion. The methodology is illustrated with a dose-response model that assumes trinomial responses. Simulation studies show that the method is capable of identifying the optimal dose accurately without exposing many patients to toxic doses.

Optimum designs for non-linear mixed effects models in the presence of covariates.

In this article, we present a new method for optimizing designs of experiments for non-linear mixed effects models, where a categorical factor with covariate information is a design variable combined with another design factor. The work is motivated by the need to efficiently design preclinical experiments in enzyme kinetics for a set of Human Liver Microsomes. However, the results are general and can be applied to other experimental situations where the variation in the response due to a categorical factor can be partially accounted for by a covariate. The covariate included in the model explains some systematic variability in a random model parameter. This approach allows better understanding of the population variation as well as estimation of the model parameters with higher precision.

[Pancreatic cancer microenvironment]. / Mikrosrodowisko raka trzustki.

Pancreatic cancer remains one of the deadliest solid tumors in humans and an unsolved problem of today's medicine. Experimental studies reveal that the heterogeneous and complex pancreatic cancer microenvironment is responsible, not only for cancer growth, spread, development of metastases, but also for cancer recurrence and chemotherapy resistance. Chemotherapy affecting the cancer stroma is still under clinical and experimental research and remains hope for cure of pancreatic cancer. We present the cancer microenvironment characteristics and summary of experimental studies with use of agents affecting pancreatic cancer stroma.

Optimizing dose regimens and fixed dose combination ratios in clinical trials.

Successful treatment of many diseases depends on the level of drug concentration in blood and its maintenance over a period of time around a value considered as therapeutic. The dose regimen that minimizes the underexposure and overexposure around the target concentration maximizes efficacy and safety, resulting in increased chances of a successful patient recovery. We present a method of computer-assisted dose finding by explicit optimization of a target criterion. We develop a general theory for such dose regimens and propose criteria for their computation. This approach is likely to supersede "brute force" techniques exclusively based on simulation. In case of a combination of two drugs in a single dosing unit, it is crucial that the optimal combination ratio is identified during the developmental process and is taken forward to further trials or approval. The algorithm computes the optimal ratio along with the optimal dose regimen. If the interest is in restricting the concentration profile of the drug to a therapeutic range, we adapt the algorithm to determine the optimal dose regimen. In future, this work is intended to aid the development of fixed dose combinations, especially antimalarials and other anti-infectives. The methodology also has potential applications in randomized concentration-controlled trials where adherence to the target concentration is a fundamental requirement.

Association between serum osteocalcin, adiposity and metabolic risk in obese children and adolescents.

INTRODUCTION: Childhood obesity has been associated with the development of insulin resistance, potentially leading to several metabolic disorders. Osteocalcin has been reported to contribute to the regulation of glucose tolerance and insulin sensitivity. The purpose of this study was to examine the relationship between serum osteocalcin and metabolic risk factors in obese children and adolescents. MATERIAL AND METHODS: Age, gender, pubertal stage, adiposity markers (standard deviation score of body mass index: BMI-SDS, percentage of body fat, waist circumference), blood pressure, serum osteocalcin (OC), fasting plasma glucose and insulin, glycated haemoglobin level (HbA1c), insulin resistance estimated by homeostasis model assessment (HOMA-IR), lipid profile, C-reactive protein (CRP), fibrinogen (FB), white blood cell count (WBC) and 25-hydroxyvitamin D (25-OH-D) were evaluated in 142 obese children and adolescents. Stepwise multiple regression analysis was used to determine the relationship between serum osteocalcin and metabolic risk parameters. RESULTS: Mean serum osteocalcin level was 72.0 ± 20.5 µg/L (range: 16.8-181.5 µg/L). After adjustment for multiple potential confounders, serum osteocalcin concentration was inversely associated with adiposity markers as well as HOMA-IR, HbA1c, triglycerides, CRP, FB and positively with 25-OH-D and HDL-cholesterol. In stepwise multiple linear regression analysis adjusted for age, gender and pubertal stage, osteocalcin was significantly negatively related to HOMA-IR, triglycerides and waist circumference. CONCLUSIONS: Serum osteocalcin concentration is associated with blood markers of dysmetabolic phenotype and measures of adiposity, suggesting that osteocalcin is important not only for bones but also for glucose and fat metabolism as early as during childhood.

Polymorphism of CD36 gene, carbohydrate metabolism and plasma CD36 concentration in obese children. A preliminary study.

INTRODUCTION: CD36 may play an important role in removal of oxidized LDLs from plasma, protein glycation, the pathogenesis of insulin resistance, type 2 diabetes, and diabetic micro- and macroangiopathy. Some reports have pointed to decreased expression of macrophages in association with mutations of the CD36 gene in hyperglycemic and obese subjects. The aim of the study was to search for an association between CD36 gene polymorphism and carbohydrate metabolism disturbances or variability of plasma soluble CD36 concentrations in obese children. MATERIAL/METHODS: The study included 60 children aged 10 to 15 years: 30 with (study group) and 30 without (control group) obesity. Each patient's glycated hemoglobin, weight, height, waist and hip circumference, and systolic and diastolic blood pressure were measured, BMI, WHR and MAP were calculated, and oral glucose tolerance test was performed with glucose and insulin concentration measurements. Amplicons of exons 4-6 of CD36 were studied using DHPLC technique. The PCR products with alterations were bidirectionally sequenced. Plasma concentrations of human antigen CD36 was measured using a commercially available enzyme-linked immunosorbent assay (ELISA). RESULTS: We found two intronic alterations: IVS3-6 T/C (rs3173798) and IVS4-10 G/A (rs3211892), one nonsynonymous substitution: G367A (Glu123Lys, rs183461468) in exon 5 and two synonymous transitions in exon 6: G573A (Pro191Pro, rs5956) and A591T (Thr197Thr, rs141680676). There were no significant differences in any biochemical or morphometric parameters between genotype groups. DISCUSSION: The polymorphisms of the studied fragment of CD36 are not associated with carbohydrate metabolism disturbances or the variability of plasma soluble CD36 concentrations in obese children, but further research is necessary to assess their functional implications.

Changes in inflammatory biomarkers after successful lifestyle intervention in obese children.

BACKGROUND: Obesity has been associated with low-grade systemic inflammation, potentially leading to insulin resistance, type 2 diabetes, dyslipidemia, and cardiovascular diseases. Even moderate weight loss through dietary changes and physical exercise is effective in preventing and managing obesity-associated disorders. The aim of this study was to determine the effect of weight loss in response to a lifestyle modification on the serum levels of inflammatory markers in obese children and adolescents. MATERIAL AND METHODS: Fifty obese subjects completed a six-month programme consisting of combined hypocaloric diet and moderate physical activity. High-sensitive C-reactive protein (CRP), interleukin-6 (IL-6), fibrinogen (FB), white blood count (WBC), glucose, insulin, insulin resistance index (HOMA IR), glycosylated haemoglobin (HbA(1c)), lipids as well as systolic (SBP) and diastolic blood pressure (DBP) were measured before and after intervention. RESULTS: Patients had a 5.3 ± 3.4 kg average weight loss, with significant decreases of SDS-BMI, percentage of body fat, SDS-waist, SBP and DBP, HOMA-IR, HbA(1c) and reductions in serum IL-6, CRP, WBC, FB. In the multivariable linear models, changes in percentage of body fat and HOMA-IR were positively associated with favourable changes in inflammatory parameters. CONCLUSION: This study demonstrates that weight reduction after successful lifestyle intervention results in improvements of blood inflammatory markers in obese children and adolescents.

Serum 25-hydroxyvitamin D (25-OH-D) in obese adolescents.

BACKGROUND: There is increasing evidence that vitamin D deficiency is common and has been associated with several non-bone related outcomes, including insulin resistance, type 2 diabetes and cardiovascular disease. The influences of gender, puberty, and adiposity on serum hydroxyvitamin D (25-OH-D) levels and the relationship between 25-OH-D and insulin resistance in obese children were studied. MATERIAL AND METHODS: Age, gender, pubertal stage, weight status (standard deviation score of body mass index: BMI-SDS, percentage body fat, waist circumference), 25-OH-D levels, and insulin resistance index calculated by homeostasis model assessment (HOMA-IR) were evaluated in 64 obese adolescents. Multivariable linear regression was used to determine factors associated with decreased serum 25-OH-D levels and to study the relationship between 25-OH-D and HOMA-IR. RESULTS: Median serum 25-OH-D level was 10.1 ng/mL (25.2 nmol/L). 14% of patients were vitamin D-sufficient (25-OH-D ≥ 20 ng/mL), 36% had intermediate values (11-19 ng/mL), and 50% were deficient (25-OH-D ≤ 10 ng/mL). In the multivariable model, older age, puberty, higher value of percentage of body fat, and the presence of acanthosis nigricans (AN) were all negatively associated with 25-OH-D. Lower 25-OH-D levels were also associated with higher blood glucose, insulin and HOMA-IR after adjustment for puberty and SDS-BMI. Summer positively correlated with 25-OH-D level. CONCLUSION: Our study confirms that obesity is a risk factor for vitamin D deficiency. Hypovitaminosis D, common in obese adolescents at risk for type 2 diabetes (older age, puberty, acanthosis nigricans) is associated with worse insulin resistance.

Optimum design of experiments for enzyme inhibition kinetic models.

We find closed-form expressions for the D-optimum designs for three- and four-parameter nonlinear models arising in kinetic models for enzyme inhibition. We calculate the efficiency of designs over a range of parameter values and make recommendations for design when the parameter values are not well known. In a three-parameter experimental example, a standard design has an efficiency of 18.2% of the D-optimum design. Experimental results from a standard design with 120 trials and a D-optimum design with 21 trials give parameter estimates that are in close agreement. The estimated standard errors of these parameter estimates confirm our theoretical results on efficiency and thus on the serious savings that can be made by the use of D-optimum designs.

[Maternal active or passive smoking in relation to some neonatal morphological parameters and complications]. / Palenie czynne lub bierne w okresie ciazy a wybrane parametry morfologiczne i powiklanma okresu noworodkowego.

OBJECTIVE: To determine the relationship between maternal active and passive smoking and neonatal morphological parameters, as well as some neonatal complications in full-term newborns. METHODS: 150 women with uncomplicated, singleton pregnancies were assessed by means of a patient questionnaire. Neonates were divided into 3 groups according to obtained information on maternal smoking status--active smoking: n=51, passive smoking: n=49, non-smoking: n=50. Immediately after birth morphological parameters such as: birthweight, body length, head and chest circumference were assessed. RESULTS: Values of birthweight, body length, head and chest circumference in newborns born to active smoking mothers were significantly lower than in newborns of passive smoking and non-smoking mothers. No significant differences in values of RBC, WBC, PLT Hemoglobin and Hematocrit between the studied groups have been detected. Oxygen hood was applied significantly more often in case of newborns from active smoking mothers than in the control subjects. In groups of newborns from active and passive smoking mothers, hyperbilirubinemia and signs of early onset infection were diagnosed significantly more frequently than in the control subjects. CONCLUSIONS: Active maternal smoking, as opposed to passive maternal smoking, leads to decreased birthweight, body length, head and chest circumference. Full-term newborns born to active smoking mothers often need to be treated with oxygen hood during the first hours after birth. Maternal smoking, both active and passive, leads to an increased risk of hyperbilirubinemia and early onset infection in neonates.

Analysis of human CD36 gene sequence alterations in the oxidized low-density lipoprotein-binding region using denaturing high-performance liquid chromatography.

Denaturing high-performance liquid chromatography (DHPLC) has been employed as a prescreening tool to reduce the amount of DNA sequencing. It could be a simple and cost-effective screening method for mutations and polymorphisms in exons 4, 5, and 6 of the CD36 gene, which encode the protein region responsible for the removal of oxidized low-density lipoprotein. Genomic DNA was isolated from 306 Caucasian infants of Polish origin. Six single-nucleotide substitutions were detected by DHPLC and confirmed by direct sequencing. The A591T, G550A, and C572T alterations have not been described so far. Each of two nonsynonymous substitutions (Asp184Asn, Pro191Leu) was found in one subject (0.2% minor allele frequency). The results suggest that nonsynonymous alterations in the analyzed CD36 region are rare in Caucasians. DHPLC is a specific and cost-effective technique that may prove to be particularly useful for the identification of polymorphisms and mutations in the CD36 gene.

Potential application of D-optimal designs in the efficient investigation of cytochrome P450 inhibition kinetic models.

Correctly chosen d-optimal designs provide efficient experimental schemes when the aim of the investigation is to obtain precise estimates of parameters. In the current work, estimates of parameters refer to the enzyme kinetic parameters V(max) and K(m), but they also refer to the inhibition constant K(i). In general, this experimental approach is performed on a grid of values of the design variables. However, this approach may not be very efficient, in the sense that the parameter estimates (V(max), K(m), and K(i)) have unnecessarily high variances. For good estimates of parameters, the most efficient designs consist of clusters of replicates of a few sets of experimental conditions. The current study compares the application of such d-optimal designs with that of a conventional approach in assessing the competitive inhibitory potency of fluconazole and sertraline toward CYP2C9 and 2D6, respectively. In each instance, the parameter estimates, namely V(max), K(m), and K(i), were predicted well using the d-optimal design compared with those measured using the rich data sets, for both inhibitors. We show that d optimality can provide more efficient designs for estimating the model parameters, including K(i). We also show that real cost savings can be made by carefully planning studies that use the theory of optimal experimental design.

Serum leptin concentrations in children with mild and moderate malnutrition.

INTRODUCTION: Numerous studies have reported a strong relationship between plasma leptin concentration and percentage of body fat, fat mass, and body mass index (BMI) in obese and non-obese children. The objective of the present study was to assess the usefulness of serum leptin concentration in disclosing prepubertal malnutrition. MATERIAL AND METHOD: Leptin concentrations in serum were determined and anthropometric parameters were measured in 149 children (3-6 and 7-10 years old). The Cole index of nutritional status was calculated. 44 children (I) presented with long-standing malnutrition due to celiac disease or food allergy and 105 children (II) were healthy. RESULTS: Leptin concentrations in both age groups of undernourished boys (median 2.7 and 2.7 microg/L) and in younger undernourished girls (median 4.2 microg/L) did not differ from concentrations in healthy children (median 2.9, 2.9, and 3.4 microg/L, respectively). Leptin concentrations in older undernourished girls were significantly lower than in healthy girls (median 4.2 vs. 8.8 microg/L, respectively; p < 0.05) of comparable age. In healthy children, leptin levels correlated with gender, body mass, BMI, Cole ratio (r = 0.39-0.41, r = 0.33, r = 0.28, r = 0.22, respectively; p < 0.005), and height (r = 0.19; p < 0.05). Serum leptin concentrations in undernourished children correlated with gender, arm circumference, and BMI (r = 0.27-0.35, r = 0.27, r = 0.25, respectively; p < 0.05). CONCLUSIONS: Our results show that serum leptin concentration is not a useful indicator of mild and moderate malnutrition in prepubertal children.

Analysis of the sodium iodide symporter expression in histological slides from a nodular goiter.

BACKGROUND: The aim of the study was analysis at both the level and the cell site of the sodium/iodide symporter (NIS) in histological slides from hot, warm, and cold nodules and extranodular parenchyma according to scintigraphy. METHODS: The study population consisted of 97 people who underwent surgery for a toxic nodular goiter (26 patients) or a non-toxic nodular goiter (71 patients). Immunohistochemical study was performed with 198 histological slides from hot, warm, and cold nodules (study slides) and the extranodular parenchyma (control slides). The level of NIS expression was estimated objectively using the computerized image analysis system, Quantimet 600S (Leica, Cambridge, UK). RESULTS: We found significantly higher NIS expression in hot nodules than in cold nodules and in warm nodules than in cold ones. We found significantly higher NIS expression in hot and warm nodules than in the surrounding parenchyma. The level of NIS expression did not differ significantly between cold nodules and the collateral tissues. CONCLUSIONS: Our data indicate that NIS protein participates in the development of hyperthyroidism in the course of a nodular goiter. We confirm that the functional state of a nodular goiter is determined by NIS expression in nodules, not in collateral parenchyma. The low metabolism of cold nodules does not simply result from decreased level of NIS protein or its defective targeting to the cell membrane. The observation of NIS in the cell cytoplasm of hot nodules seems to indicate that the intracellular localization of NIS does not determine loss of its activity.

[Atypical forms of hyperthyroidism]. / Nietypowe postacie nadczynnosci tarczycy.

Except from well-known the most frequent reasons of the hyperthyroidism such as the Graves-Basedow disease, multinodular goitre and the autonomous adenoma we should also remember the other rarer illnesses leading to the excess of thyroid hormones in the serum. Authors presented the problem of atypical forms of thyrotoxicosis which run without the overproduction of thyroid hormones and are characterized by low 24 h 131 J uptake by the thyroid gland. So called masks of hyperthyroidism such as apathetic, neuromuscular, gastrointestinal and cardiovascular forms were also discussed in the article.

Relation of low-grade inflammation and endothelial activation to blood pressure in obese children and adolescents.

OBJECTIVE: To determine the role of low-grade, systemic inflammation and endothelial activation in the modulation of blood pressure (BP) independently of other traditional risk factors in obese children and adolescents. DESIGN: We surveyed 281 obese subjects, aged 6-18 years to investigate the relationship of serum inflammation and endothelial activation markers and blood pressure. MEASUREMENTS: Clinical variables, indices of obesity, ambulatory 24-h blood pressure and serum concentrations of C-reactive protein (CRP), interleukin-6 (IL-6), interleukin-1 beta (IL-1 beta), intercellular cell adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), glucose and insulin. HOMA IR was used as a marker of insulin resistance (IR). RESULTS: CRP, IL-6, IL-1 beta, and ICAM-1 correlated significantly with mean 24-h systolic BP, whereas CRP and IL-6 was positively correlated with mean 24-h diastolic BP. Multiple regression analysis showed that serum IL-6 (P < .001) concentration, HOMA IR (P < .01), and waist to hip ratio (P < .05) were the significant determinants of systolic BP, whereas CRP (P < .05) level was the only predictor of diastolic BP. There were no significant associations of cell adhesion molecules with BP. CONCLUSIONS: These results indicate that low-grade inflammation may play a role in the modulation of arterial BP relatively early in life.

Low-grade systemic inflammation and the risk of type 2 diabetes in obese children and adolescents.

BACKGROUND: There is growing evidence that low-grade systemic inflammation is closely involved in the pathogenesis of type 2 diabetes. OBJECTIVE: The aim of this study was to investigate the relationship between serum inflammatory markers and selected parameters known as risk factors of type 2 diabetes in obese children and adolescents. SUBJECTS AND METHODS: Fasting levels of C-reactive protein (CRP), fibrinogen (FB) interleukin-6 (IL-6), interleukin 1-beta (IL-1beta), glucose, insulin, total, HDL and LDL cholesterol, triglycerides, white blood cell count (WBC) and fasting glucose to insulin ratio (FGIR) were measured in 281 obese children and adolescents. Pearson's correlation was used for assessing the relationship between inflammatory markers and selected clinical parameters. RESULTS: Inflammatory markers correlated significantly with insulin resistance indices, HbA1c, lipid profile, hypertension, positive family history of type 2 diabetes, low physical fitness, and mixed high-fat and high-carbohydrate diet. CONCLUSIONS: Serum inflammatory markers were significantly correlated with most factors implicated in the development of type 2 diabetes. These data provide additional support for previously reported in adults relationship between subclinical inflammation and the risk of type 2 diabetes.