In vitro and in silico characterisation of Tacrolimus released under biorelevant conditions.

This work aims to better understand the in vivo behaviour of modified release (MR) formulations (Envarsus tablets and Advagraf capsules) using in vitro properties of tacrolimus and in silico simulations. The in silico concentration profiles of tacrolimus released from the MR formulations were predicted after building a three compartments PK model with GastroPlus™, and using the experimentally determined in vitro physico-chemical properties as input parameters. In vitro-in vivo correlations (IVIVC) were obtained after deconvolution of in vivo data from a clinical trial. The IVIVC showed that the in vitro dissolution was faster than the in vivo deconvoluted dissolution for Advagraf, while the in vitro dissolution was slightly slower than the in vivo deconvoluted dissolution for Envarsus. Population PK simulation showed that variability in the simulation was lower for Envarsus compared to Advagraf. The in silico predicted preferential absorption sites were the proximal and distal tract for Advagraf and Envarsus, respectively. The integration of experimental in vitro solubility, permeability and biorelevant dissolution data allowed to generate in silico tacrolimus concentrations for two different MR formulations. This permitted to compare the two formulations in a single PK profile, in a simulated population PK study and with respect to their absorption sites.