Semmelweis Egyetem, Farmakológiai és Farmakoterápiás Intézet, Budapest
SUMMARY – Although the basic theory of the early development of different drug groups is identical, due to their various pharmacological characteristics the design of the studies, the starting safe dose and the selection of the pharmacologic and therapeutic end-points show signifi cant differences. The development process of drugs is usually divided into two functionally different parts, the learning and the confi rming phases, respectively. The aim of the fi rst part is the description of the suggested targets, the mechanism of action in humans and the characterization of the drug-linked biomarkers. This section contains the microdose (phase 0), phase I and II studies. The end-point of this part is the proof of the underlying concept which was developed on the basis of the non-clinical studies. According to the internationally accepted terminology, this strategically important point is called the Proof of Concept (POC). Upon POC it has to be decided whether the drug-candidate possesses those qualities which make it worthwhile to perform human phase III studies, treating the statistically required number of patients for proving the good therapeutic effi cacy and safety of the drug. This section of the drug development is called the confi rmatory phase. The use of highly sophisticated technology opened the possibility to apply microdoses in humans for studying the pharmacokinetics and pharmacodynamics of new drugs as well as the characteristics of human biomarkers at very low, harmless drug doses. This approach made possible to draw important conclusions on the usefulness of biomarkers for the clinical practice even following the fi rst drug-application. The planning of phases I and II studies, the calculation of the applicable doses, the selection of the pharmacologic and therapeutic end-points, the use of biomarkers, are all based on the concept of translational medicine and are essentially dependent on the results obtained both in animal experiments and human microdose studies.