Ligand-receptor interactions studied by PET: implications for drug development

Positron emission tomography (PET) is a quantitative imaging method that ca n be used to characterize binding properties of specific target molecules s uch as various receptors, transporter molecules and enzymes irt vivo. Altho ugh already applied successfully, one Of the greatest challenges for the te chnique is to understand better the in vivo complexities of ligand-receptor (target) interaction. The PET technique can be used efficiently in animal studies but, moss importantly, also in human studies. PET imaging of patien ts and healthy volunteers can generate information on human pathophysiology at a molecular level currently unobtainable with other methods. Modern ima ging techniques are increasingly applied to drug discovery and development. There are many ways of utilizing PET in pharmacodynamic studies, one inter esting approach being the indirect exploration of synaptic neurotransmissio n with receptor ligands. The receptor occupancy-type studies with PET are r apidly becoming a state-of-the-art method for verifying the mechanism of ac tion of a given drug in man and especially for facilitating the dose-findin g procedures in early drug development. Thus far, PET has been mainly appli ed to pharmacodynamic studies in the central nervous system. but will be us ed also in other areas of drug development such as cardiovascular diseases and oncology.