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One of the objectives of oncology phase I dose‐escalation studies has been to determine the maximum tolerated dose (MTD). Although MTD is no longer set as the dose for further development in contemporary oncology drug development, MTD determination is still important for informing the therapeutic index. Bayesian adaptive model‐based designs are becoming mainstream in oncology first‐in‐human trials. Herein, we illustrate via simulations the use of systemic exposure in Bayesian adaptive dose–toxicity models to estimate MTD. We extend traditional dose–toxicity models to incorporate pharmacokinetic exposure, which provides information on exposure–toxicity relationships. We pursue dose escalation until the maximum tolerated exposure (corresponding to the MTD) is reached. By leveraging pharmacokinetics, dose escalation considers exposure and interindividual variability on a continuous rather than discrete domain, offering additional information for dose‐escalation decisions. To demonstrate this, we generated 1000 simulations (starting dose of 1/25th the reference dose and six dose levels) for several different scenarios. Both rule‐based and model‐based designs were compared using metrics of potential safety, accuracy, and reliability. The mean results over simulations and different toxicity scenarios showed that model‐based designs were better than rule‐based methods and that exposure–toxicity model‐based methods have the potential to valuably complement dose–toxicity model‐based methods. Exposure–toxicity model‐based methods had decreased underdose risk accompanied by a relatively smaller increase in overdose risk, resulting in improved net reliability. MTD estimation accuracy was compromised when exposure variability was large, emphasizing the importance of appropriate control of pharmacokinetic variability in phase I dose‐escalation studies. [ABSTRACT FROM AUTHOR]

Cladribine Tablets (MAVENCLAD®) are used to treat relapsing multiple sclerosis (MS). The recommended dose is 3.5 mg/kg, consisting of 2 annual courses, each comprising 2 treatment weeks 1 month apart. We reviewed the clinical pharmacology of Cladribine Tablets in patients with MS, including pharmacokinetic and pharmacometric data. Cladribine Tablets are rapidly absorbed, with a median time to reach maximum concentration (Tmax) of 0.5 h (range 0.5-1.5 h) in fasted patients. When administered with food, absorption is delayed (median Tmax 1.5 h, range 1-3 h), and maximum concentration (Cmax) is reduced by 29% (based on geometric mean). Area under the concentration-time curve (AUC) is essentially unchanged. Oral bioavailability of cladribine is approximately 40%, pharmacokinetics are linear and time-independent, and volume of distribution is 480-490 L. Plasma protein binding is 20%, independent of cladribine plasma concentration. Cladribine is rapidly distributed to lymphocytes and retained (either as parent drug or its phosphorylated metabolites), resulting in approximately 30- to 40-fold intracellular accumulation versus extracellular concentrations as early as 1 h after cladribine exposure. Cytochrome P450-mediated biotransformation of cladribine is of minor importance. Cladribine elimination is equally dependent on renal and non-renal routes. In vitro studies indicate that cladribine efflux is minimally P-glycoprotein (P-gp)-related, and clinically relevant interactions with P-gp inhibitors are not expected. Cladribine distribution across membranes is primarily facilitated by equilibrative nucleoside transporter (ENT) 1, concentrative nucleoside transporter (CNT) 3 and breast cancer resistance protein (BCRP), and there is no evidence of any cladribine-related effect on heart rate, atrioventricular conduction or cardiac repolarisation (QTc interval prolongation). Cladribine Tablets are associated with targeted lymphocyte reduction and durable efficacy, with the exposure-effect relationship showing the recommended dose is appropriate in reducing relapse risk. [ABSTRACT FROM AUTHOR]

Purpose: The aims of this study were to characterize the concentration-time course of cladribine (CdA) and its main metabolite 2-chloroadenine (CAde), estimate interindividual variability in pharmacokinetics (PK), and identify covariates explaining variability in the PK of CdA.Methods: This population PK analysis was based on the combined dataset from four clinical studies in patients with multiple sclerosis (MS): three phase I studies, including one food and one drug-drug interaction study, and one phase III clinical study. Plasma and urine concentration data of CdA and CAde were modeled simultaneously.Results: The analysis comprised a total of 2619 CdA and CAde plasma and urine concentration observations from 173 patients with MS who received an intravenous infusion or oral tablet doses of CdA as a single agent or in combination with interferon (IFN) β-1a. CdA PK data were best described by a three-compartment model, while a one-compartment model best described the PK of CAde. CdA renal clearance (CLR) was correlated with creatinine clearance (CLCR), predicting a decrease in the total clearance of 19%, 30% and 40% for patients with mild (CLCR = 65 ml/min), moderate (CLCR = 40 ml/min) and severe (CLCR = 20 ml/min) renal impairment, respectively. Food decreased the extent of CdA absorption by 11.2% and caused an absorption delay. Coadministration with IFNβ-1a was found to increase non-CLR (CLNR) by 21%, resulting in an increase of 11% in total clearance.Conclusions: Both CdA and CAde displayed linear PK after intravenous and oral administration of CdA, with CdA renal function depending on CLCR. Trial registration number for study 25643: NCT00213135. [ABSTRACT FROM AUTHOR]

Background: Sapropterin dihydrochloride, a synthetic formulation of BH4, the cofactor for phenylalanine hydroxylase (PAH, EC 1.14.16.1), was initially approved in Europe only for patients ≥4 years with BH4-responsive phenylketonuria. The aim of the SPARK (Safety Paediatric efficAcy phaRmacokinetic with Kuvan®) trial was to assess the efficacy (improvement in daily phenylalanine tolerance, neuromotor development and growth parameters), safety and pharmacokinetics of sapropterin dihydrochloride in children <4 years.Results: In total, 109 male or female children <4 years with confirmed BH4-responsive phenylketonuria or mild hyperphenylalaninemia and good adherence to dietary treatment were screened. 56 patients were randomly assigned (1:1) to 10 mg/kg/day oral sapropterin plus a phenylalanine-restricted diet or to only a phenylalanine-restricted diet for 26 weeks (27 to the sapropterin and diet group and 29 to the diet-only group; intention-to-treat population). Of these, 52 patients with ≥1 pharmacokinetic sample were included in the pharmacokinetic analysis, and 54 patients were included in the safety analysis. At week 26 in the sapropterin plus diet group, mean phenylalanine tolerance was 30.5 (95% confidence interval 18.7-42.3) mg/kg/day higher than in the diet-only group (p < 0.001). The safety profile of sapropterin, measured monthly, was acceptable and consistent with that seen in studies of older children. Using non-linear mixed effect modelling, a one-compartment model with flip-flop pharmacokinetic behaviour, in which the effect of weight was substantial, best described the pharmacokinetic profile. Patients in both groups had normal neuromotor development and stable growth parameters.Conclusions: The addition of sapropterin to a phenylalanine-restricted diet was well tolerated and led to a significant improvement in phenylalanine tolerance in children <4 years with BH4-responsive phenylketonuria or mild hyperphenylalaninemia. The pharmacokinetic model favours once per day dosing with adjustment for weight. Based on the SPARK trial results, sapropterin has received EU approval to treat patients <4 years with BH4-responsive phenylketonuria.Trial Registration: ClinicalTrials.gov, NCT01376908 . Registered June 17, 2011. [ABSTRACT FROM AUTHOR]

Aims of this analysis was to develop a pullulation pharmacokinetic model for Emfilermin (recombinat human leukaemia inibitory factor, r-hLIF) following subcutaneous administraton to healthy women and to infertile patients undergoing in vitro fertilization and transfer (IVF-Et).Methods Data from three studies, a single and a repeatdose phase I study in postmenopausal women as well as a proof of concept study undergoing in vitro fertilization and embryo tranfer were combned and analyzed. The structural pharmacokinetic model was developed using the rich data from Phase I studies and the full pharmacostatistical model was then derived using all the data.Results The pharmacokinetics of r-hLIF after repeated subcutaneous administration were described by a one-compartment disposition model with a zero order input. The duration of the absorbation phase was short (0.8 h) and invariant. The apparent clearance in postmenopausal women 57 &iota h -1 (Cv=17%). In vitro fertilization and embryo transfer patients, the apparent clearance was decreased by 35% compared with portmenopausal women. the apparent volume of distribution was 2351 (interindividual CV = 28%) and exhibited an interoccasion variability of 23%. Itfor every 10kg body weight. The medain posthoc estimates of apparent clearance and volume of distribution and thier variability were consistent with those population estimates. In postmenopausal women, the results were consistent with those obtained by noncompartment analysis. the residual variability on r-hLIF serum concentration was 20%.Conclusions. the pharmacokinetics of r-hLIF after repeated SC administration were describes by a one compartment disposition model, with zero order input, in postmenopausal women and those undergoing IVF of intracytoplasmic sperm onjection and embryo tranfer. Absorption og r-LIF rapid as was its subsequent clearance. The apparent volume of distribution of r-LIF was moderate to high, depended on body weigh and showed interoccasion variability. [ABSTRACT FROM AUTHOR]