Development of drugs based on the MC2R antagonists will directly benefit children with CAH and Cushing's diseases, and will help us to understand MC2R's role in metabolic pathways. The long term goal of this project is to discover small molecule inhibitors of MC2 receptor and develop drugs to treat several metabolic diseases including CAH and Cushing's diseases afflicting children. Our Phase I studies to identify novel ACTH small molecule antagonists were successful; we were able to identify 3 novel non-peptide small molecule ACTH antagonists that have high affinity to the MC2R. The inhibitors belong to the same chemotype with a similar chemical backbone. These compounds are full ACTH antagonists that potently inhibit ACTH-stimulated adrenal cell activity. We have achieved the Phase I goals and discovered a novel series of small molecule non-peptide ACTH antagonists. Phase II of this project will be dedicated to extending our studies of ACTH antagonists by examining structure-activity relationships using series analogs of identified inhibitors to assess their ACTH antagonist potency, specificity, and selectivity, and initiating animal testing. Specifically we will: 1) examine ACTH antagonist structure-activity relationships to increase our understanding of basic structural requirements for the compound to bind to MC2R; 2) assess selectivity and specificity of the ACTH antagonists to other melanocortin and unrelated receptors; (3) assess ADME- related characteristics such as human serum albumin binding, P450 inhibition, lipid membrane, CACO-2 permeability, and in vitro cytotoxicity; 4) perform in vivo animal toxicology/pharmacokinetic testing; and 5) assess ability to block ACTH action in an in vivo animal model. These studies combine ChemDiv's expertise in drug discovery with a Yale laboratory with expertise in GPCR action and treatment of adrenal disorders. The studies will lead to novel approaches for treating patients with ACTH-dependent adrenal disorders. Project Narrative: The production of adrenal gland hormones, including cortisol and androgens, is regulated by pituitary ACTH (adrenocorticotropin hormone), which acts via the melanocortin-2 receptor (MC2R) to stimulate steroid production. Serious clinical disorders affecting the adrenal gland include congenital virilizing adrenal hyperplasia (CAH) and Cushing's disease. The ability to antagonize ACTH action will greatly facilitate the care of these and other conditions affecting the adrenal gland. Unfortunately, high-affinity small molecule ACTH antagonists are not identified yet and are not currently available for clinical use. [unreadable] [unreadable] [unreadable]