Abstract
Preclinical Research & Development Appropriate translation and determination of the maximum recommended starting dose in human is a vital task in new drug development and research. Allometric scaling is the most frequently used approach for dose extrapolation based on normalization of dose-to-body surface area. Misinterpretation of allometric dose conversion and safety factor application can lead to major problems in calculating maximum recommended safe starting dose in first-in-human clinical trials. Therefore, dose translation always necessitates careful consideration of body surface area, pharmacological, physiological and anatomical factors, pharmacokinetic parameters, metabolic function, receptor, and life span. The concept of estimating the first-in-human dose, interspecies scaling between species and the factors influencing the dose escalation were reviewed. The pros and cons of various approaches to determine first-in-human dose including allometric scaling, pharmacokinetically guided approach, minimal anticipated biological effect level, pharmacokinetic-pharmacodynamic modeling, similar drug approach, and microdosing were explained. The five steps to estimate maximum recommended starting dose for human studies by scaling factor were elaborated. Few examples, illustrating the application of different approaches were also demonstrated along with concerns that may be considered while applying such methods. Furthermore, typical considerations in dose administration, dosing through diet, maximum absorbable dose, blood sampling, and anesthesia in animal species were discussed. In summary, this review may serve as a concise guide for predicting human equivalent dose from animal species for researchers involved in various phases of preclinical and early clinical drug development.