Novel detection strategies for drug discovery.

The Human Genome Project is expected to increase the number of potential drug targets from the current figure of 500 to approximately 3,000-4,000. This increased number of targets, and increasing knowledge of signaling-pathway networks and their complexities, sets new demands for efficiency on HTS assay technologies. Assessment of the total efficacy of a given drug candidate requires not only the classical assays, but also a wide variety of assays related to signaling cascades and cellular functions. Discrete functional assays traditionally involved Ca(2+) flux, kinases and cAMP, but today extend to the whole signaling network, from ligand binding to expression. This review discusses emerging novel non-radioisotopic assays, such as ligand-stimulated GTP-binding, the inositol triphosphate assay, cellular receptor trafficking, and protein-protein interactions.