Abstract

Concerns over maternal and fetal exposure of drugs highlights the need for a better understanding of drug distribution into the fetus through the placental barrier. This study aimed to predict maternal and fetal drug disposition using physiologically based pharmacokinetic (PBPK) modelling. The detailed maternal-placental-fetal PBPK model within the Simcyp Simulator V20 was used to predict the maternal and fetoplacental exposure of cefazolin, cefuroxime, and amoxicillin during pregnancy and at delivery. The mechanistic dynamic model includes physiological changes of the maternal, fetal, and placental parameters over the course of pregnancy. Placental kinetics were parametrized using permeability parameters determined from the physicochemical properties of these compounds. Then, the PBPK predictions were compared to the observed data. Fully bottom-up feto-placental PBPK models were developed for cefuroxime, cefazolin, and amoxicillin without any parameter fitting. Predictions in non-pregnant and in pregnant subjects fall within 2-fold of the observed values. Predictions matched observed PK data reported in 9 maternal (5 fetoplacental) studies for cefuroxime, 10 maternal (5 fetoplacental) studies for cefazolin, and 6 maternal (2 fetoplacental) studies for amoxicillin. Integration of the fetal and maternal system parameters within PBPK models, together with compound-related parameters used to calculate placental permeability facilitates and extends the applications of the maternal-placental-fetal PBPK model. The study results indicated that the model can also be used for designing clinical trials and prospectively use for maternal/fetal risk assessment following maternally administered drugs or unintended exposure to environmental toxicants.

Significance Statement This study investigates the performance of an integrated maternal-placental-fetal PBPK model to predict maternal and fetal exposure of renally eliminated antibiotics that cross the placenta through a passive diffusion mechanism. The transplacental permeability clearance were predicted from the drug physicochemical properties. Results demonstrate that the developed models can facilitate the prediction of maternal and fetal drugs exposure simultaneously at any gestational age to support the use of a PBPK approach in the maternal/ fetal exposure assessments.