<scp>Dynamics of thrombin generation</scp>: <scp>Filling the gap between</scp> the <scp>system pharmacology theory and clinical practice</scp> in <scp>clinical pharmacology and therapeutics</scp>

Mathematical models of thrombin generation (TG) that have been developed are based on a systems biology approach. Although this approach provides important information about the coagulation system, its clinical applicability is limited by its complexity and number of input variables required. The aim of this study was to develop a semimechanistic model able to describe TG in trauma and control patients. A dataset containing longitudinal data of TG assays and coagulation factors from 40 trauma patients and 20 control patients was used for model building. The model considered three fundamental processes: the degradation of tissue factor (TF) through a first-order process, the activation of factor II by the TF through a first-order process, and the degradation of thrombin through a first-order process. Model fitting was performed using a nonlinear mixed-effects approach. The condition of the patient (trauma and control) and coagulation factors were modelled as covariates. Model building demonstrated the presence of two additional processes that improved the predictive capacity of the model: the activation of factor II by TF governed by a second-order constant and, a mechanism of factor II activation by TF characterized by a 7-compartment transit chain governed by a second-order constant. In the covariate model only the inclusion of patient condition was significant. Model evaluation demonstrated excellent performance in describing the temporal pattern of TG in trauma and control patients. Thrombin generation can be adequately modelled using a semimechanistic approach. Its application in practice could help to better assess the risk of hemorrhage and/or thrombosis in different settings.