Selection of the First‐Time Dose in Humans: Comparison of Different Approaches Based on Interspecies Scaling of Clearance

The authors describe four approaches to selecting a safe starting dose for humans in clinical drug trials based on interspecies scaling of clearance. Human clearance was predicted by scaling for 10 example drugs for which animal clearance values were available in the literature. The predicted human clearance values were then used to select the estimated starting dose in humans. These doses were then compared with the actual doses given to humans during clinical trials. All four approaches used to estimate the first‐time dose in humans provided values that were within the dose range given to humans from Phases I to III. This work demonstrates that animal pharmacokinetic data can be used to estimate a suitable human starting dose, provided the data have been obtained from a dose that produces no adverse effects.