Physiologically-Based Modeling and Interspecies Prediction of Cisplatin Pharmacokinetics

The goal of this work was to develop a physiologically-based pharmacokinetic (PBPK) modeling framework for cisplatin. The model was constructed based on 11 published data sets from rodents; and rabbit, dog, and human data were used to evaluate its utility in predicting plasma and tissue distribution of platinum in larger species, including humans. The model included biotransformation of cisplatin into mobile (k₁) and fixed (k₂) metabolites in all tissues, and subsequent conversion of fixed metabolites to mobile metabolites (k₃) due to protein degradation and turnover. The model successfully captured complex pharmacokinetics of platinum in rodents, and all parameters were estimated with sufficient precision. A separate k₂ parameter was estimated for each included tissue, and the relationship between the rates of formation of mobile and fixed metabolites was established through a scaling factor (k₁=k₂·SF, SF=0.74). For interspecies predictions, k₁ and k₂ were shared across all species, and k₃ was scaled allometrically based on protein turnover rate (with an exponent of -0.28). Scaled PBPK model provided a good prediction of total platinum profiles in humans and reasonably captured platinum measurements in human tissues (as obtained from autopsy).