Towards a mechanism-based analysis of pharmacodynamic drug-drug interactions in vivo

The capability to describe response surfaces with high resolution offers the opportunity to develop an understanding of the mechanisms that underlie the observed combined drug response. Operational models for drug interaction constitute a highly versatile framework for mechanism-based modelling by taking the signal transduction properties of the drug combination into account. On this basis, it is predicted that the occurrence of synergism is favoured by convergence of drug signals late in the signal transduction pathway as opposed to proximal convergence. Furthermore, a high efficiency of signal transduction poses in general a barrier to the occurrence of synergism. The in vivo application of operational models with advanced response surface modelling techniques will facilitate the rational development of synergistic drug combinations.