Melanocortin 2 receptor (MC2R) (agonist)

Class

repository (depot) corticotropin; naturally sourced complex mixture of ACTH analogs and other porcine pituitary peptides, major component N-25 deamidated porcine ACTH(1-39)

Pathway

Acthar Gel and endogenous ACTH stimulate the adrenal cortex via the ACTH/melanocortin-2 receptor to secrete cortisol, corticosterone, aldosterone and weakly androgenic substances; label states the specific mechanism of action in infantile spasms/epilepsy is unknown

Melanocortin 2 receptor (MC2R) is a G protein-coupled receptor expressed almost exclusively on cells of the adrenal cortex, the outer layer of the adrenal gland. Its natural ligand is adrenocorticotropic hormone (ACTH), a peptide released by the pituitary gland as part of the hypothalamic-pituitary-adrenal (HPA) axis, the body's central stress-response signaling system. When ACTH binds MC2R, it triggers the adrenal cortex to synthesize and release corticosteroids, chiefly cortisol, along with corticosterone, aldosterone, and small amounts of weak androgens. Pharmacologic agonism of this receptor, using ACTH-derived peptide mixtures, is a strategy for raising endogenous corticosteroid output rather than administering synthetic steroids directly. Because cortisol has broad anti-inflammatory and immune-modulating effects, MC2R agonism has been used across inflammatory, autoimmune, and neurological conditions where steroid-like activity is therapeutically desired. Notably, in some conditions such as infantile spasms, the clinical benefit does not clearly track with corticosteroid elevation alone, and the precise mechanism of benefit remains incompletely defined. This mechanism sits at the intersection of endocrinology and immunology, illustrating how a single hormonal axis can be leveraged for effects extending well beyond glucocorticoid physiology.