Browsing by Subject "distribution"

Physiologically based pharmacokinetic modelling (PBPK) can be used to predict pharmacokinetic behaviour of new drug molecules in human. PBPK model represents the body anatomically and physiologically with compartments connected to each other and combines those to drug specific parameters. PBPK modelling can be used to predict the absorption, disposition, and time-concentration profiles of drug molecules. The purpose of the study was to build a PBPK model for new drug molecule under research (compound A) and predict pharmacokinetics in human, to support the selection of dosing interval, formulation, and sampling time points for the first clinical trial. In this work it is described the building of the model in the ”bottom-up”-approach using in vitro parameters in GastroPlusTM-software. The modelling was done also for preclinical species (mouse, rat, dog) comparing the simulations to the observed in vivo data, which gave the confidence to the methods used in the modelling also for human. The model was first built for systemic kinetics and thereafter it was used for predicting pharmacokinetics after oral dosing. Parameters of systemic kinetics were compared also to the predictions from allometric scaling. Based on the preclinical species the most predictive method for the volume of distribution of compound A was the method by Lukacova, which predicted the volume of distribution to be moderate in human (1.7 l/kg). From the in vitro-to-in vivo -extrapolation methods the most predictive method to predict the clearance was the method by Poulin, which predicted low clearance in human (8.1-14.3 l/h). Empirical scaling factors based on the preclinical data were not needed, as the models predicted well the observed in vivo data. Allometric methods predicted the systemic kinetic parameters to be in the similar range. Advanced compartmental absorption transit -model (ACAT) integrated to GastroPlusTM-software predicted the absorption after oral dosing well in the preclinical species (predicted/observed ratio 0.8-1.3 for systemic exposure) despite the low solubility of the compound A. The model predicted the absorption in human to be sensitive to particle size and absorption rate to be clearly affected by the particle size. The feeding status was also predicted to affect on the absorption with larger particle sizes. The gut metabolism was not predicted to limit the oral exposure notably, whereas moderate bioavailability was predicted to be achievable. Compound A could be given in a capsule if the target particle size distribution could be achieved. The built PBPK-model can be used in the future to predict the first clinical doses by comparing the predicted plasma concentrations to in vitro pharmacodynamic parameters and to the plasma concentrations needed for efficacy in the pharmacodynamic models. The model can also be used to predict the drug-drug interactions.