Structural and functional pharmacokinetic analogs for physiologically based pharmacokinetic (PBPK) model evaluation

Physiologically based pharmacokinetic (PBPK) models enable simulations of absorption, distribution, metabolism, and elimination of chemicals from the body. Model evaluation is a key step in the PBPK model development processes whereby model predictions are compared to pharmacokinetic (PK) data. A prerequisite for PBPK model evaluation has always been the availability of PK data for the modeled compound, a requirement which has limited the use and acceptance of PBPK models since PK data is often limited or not available. The current work tests the hypothesis that an adequately developed PBPK model for a target chemical (chemical with no PK data) can be evaluated using PK data from a source chemical (chemical with existing PK data). Two different approaches for identifying the source chemical, a structural PK analog and functional PK analog technique, are used to evaluate a series of oral human PBPK models. Results show that both analog approaches can identify PK analogs which display similar PK as the target chemical and can be used as alternative ways for evaluating PBPK models. As animal free safety assessment strategies continue to develop, its important to develop alternative approaches for PBPK model evaluation which does not rely on generating new PK data.