High‐Throughput Screening for Novel Modulators of the D 3 Dopamine Receptor

The D 3 dopamine receptor (DAR) subtype plays a crucial role in regulating movement, mood and emotion, as well as reward and reinforcement. Therapeutically, the D 3 DAR may be a useful target for the treatment of drug abuse, as well as neurological and neuropsychiatric disorders. One problem of current drugs, which target the orthosteric site of DARs, is that of cross‐GPCR reactivity. However, the development of ligands that target allosteric sites on the receptor may lead to highly specific, efficacious drugs with fewer side effects. We are seeking to identify allosteric modulators of the D 3 DAR using a highly robust assay for measuring receptor activity in an HTS format. Our primary screen is an enzyme (β‐galactosidase) complementation assay that involves agonist‐induced D 3 DAR recruitment of β‐arrestin, which is measured using a luminescent read‐out. We have also developed HTS‐formatted secondary assays to measure D 3 DAR activities and counter‐screening assays to determine DAR subtype selectivity. Through the NIH Molecular Libraries Program, a 370,000+ small molecule library will be screened to identify allosteric agonists, as well as positive and negative allosteric modulators. Resulting hit compounds will be evaluated using a screening plan to characterize their activity and receptor selectivity. Tertiary assays will be performed to identify potential allosteric ligands within each pool of chemotypes.