MC1R

Class

Melanocortin-1 receptor agonist

Melanocortin-1 receptor (MC1R) is a G-protein-coupled receptor best known for its role in skin and hair pigmentation, where its natural ligand, alpha-melanocyte-stimulating hormone, signals melanocytes to produce protective eumelanin. Beyond pigmentation, MC1R is also expressed on various immune cells, including macrophages and neutrophils, where its activation tends to dampen production of pro-inflammatory signals and support resolution of inflammation. This dual biology creates two distinct rationales for developing MC1R agonists: one aimed at pigmentation-related conditions, and another aimed at inflammatory and autoimmune diseases where dialing down excessive immune activation could be therapeutically useful, such as chronic inflammatory bowel conditions or certain ocular inflammatory diseases. Because MC1R belongs to a family of five related melanocortin receptors that also govern appetite, energy balance, and adrenal steroid production, selectivity for MC1R over its relatives is important for avoiding unwanted effects on metabolism or the endocrine system. An orally available agonist targeting MC1R specifically would aim to harness the immune-modulating arm of this biology without the need for injection and without engaging the other melanocortin receptor subtypes.