In case data of humans is not available, non-clinical data can be used to generate animal PK/PD models. Based on valid assumptions these models can be used to extrapolate to the human situation, e.g. to predict a pharmacological active target concentration (MABEL). Information from extrapolated data can be used as a base for the justification of a first dose in man study. In case human data in adults is available, models can be built to allow extrapolations to the pediatric population. Simulations can then predict a dose level that provides adequate exposure.