Melanocortin 2 receptor antagonists in canine pituitary-dependent hypercortisolism: in vitro studies

Abstract

Canine hypercortisolism is most often caused by an ACTH-secreting pituitary adenoma (pituitary-dependent hypercortisolism; PDH). An interesting target for a selective medical treatment of PDH would be the receptor for ACTH: the melanocortin 2 receptor (MC2R). In this study we investigated whether two peptide compounds, BIM-22776 (#776) and BIM-22A299 (#299), are effective MC2R antagonists in vitro. Their effects on cortisol production and mRNA expression of steroidogenic enzymes, MC2R and melanocortin 2 receptor accessory protein (MRAP) were evaluated in primary adrenocortical cell cultures (n = 8) of normal canine adrenal glands. Cortisol production stimulated by 50 nM ACTH was dose-dependently inhibited by #299 (inhibition 90.7 ± 2.3% at 5 μM) and by #776 (inhibition 38.0 ± 5.2% at 5 μM). The ACTH-stimulated mRNA expression of steroidogenic enzymes, MC2R and MRAP was significantly inhibited by both compounds, but most potently by #299. These results indicate that canine primary cell culture is a valuable in vitro system to test MC2R antagonists, and that these compounds, but especially #299, are effective MC2R antagonists in vitro. To determine its efficacy in vivo, further studies are warranted. Antagonism of the MC2R is a promising potential treatment approach in canine PDH.

Management challenges and therapeutic advances in congenital adrenal hyperplasia

“…These promising preclinical results have led to the investigation of CRN04894, an oral MC2R antagonist, in a double-blind, randomized, placebo-controlled phase I study 139 . Other MC2R peptide antagonists are in preclinical development 140 , 141 .…”

Clinical advances in the pharmacotherapy of congenital adrenal hyperplasia

“…Various other therapies are in preclinical development and include anti-ACTH monoclonal antibodies ( 57 ), ACTH receptor antagonists ( 58 ), gene-based therapy ( 59 , 60 , 61 , 62 ), and cell-based therapy approaches ( 63 ). While most of these treatment strategies do not eliminate the need for glucocorticoid replacement, gene- and cell-based therapies have the anticipated hope that replacing the 21-hydroxylase enzyme itself will allow both replacement of cortisol and control of androgens ( 59 ).…”

Novel treatments for congenital adrenal hyperplasia

“…The negative effects of ACTH could potentially be diminished by ACTH antagonists [ 62 , 63 ] or ACTH receptor (MC2R) blocking [ 58 , 64 ]. Two preclinical studies tested the efficacy of an ACTH-neutralizing antibody (ALD1613 or ALD1611) in cell lines, rodents, and monkeys [ 62 , 63 ].…”

“…Alternatively, not ACTH, but its receptor MC2R could be targeted by a receptor antagonist. Antagonizing MC2R can dose-dependently lower cortisol levels in primary cultured ACTH-induced canine adrenocortical cells [ 64 ]. Currently, a double-blind, randomized, placebo-controlled phase 1 study is assessing the safety, tolerability and efficacy (steroid hormone suppression following ACTH stimulation) of an oral ACTH antagonist CRN04894 (Crinetics Pharmaceuticals) in healthy individuals.…”