Current Trends in Radio-Pharmaceuticals

The development of radiotraces with defined affinities for specific receptor systems is a potentially useful approach to the design of radio pharmaceuticals for nuclear medicine. Radio labeled ligands, such as hormones and neurotransmitters, are being synthesized and evaluated as diagnostic tools for diseases which can be characterized either by changes in receptor concentration or by novel receptor expression. Since the utility of a radio pharmaceutical is dependent upon the achievement of adequate ratios of target to non-target accumulation of radio activity, design of radio traces via the receptor approach attempts to exploit those systems in which receptor is present in significantly higher concentration at potential target sites such as tumors. Receptormediated radio tracers are also currently being used in animal models to investigate the normal tissue distribution of drug and hormone receptors and the in-vivo pharmacokinetics of receptor binding. The successful development of receptor-avid radiopharmaceuticals will depend upon the ability to synthesize ligands of high specific radio activity which retain the high affinity and binding specifically for the receptor after radio labeling.