Definition

A radioconjugate composed of a melanocyte-stimulating hormone receptor (MSHR; melanocortin-1 receptor; MC1R; melanin-activating peptide receptor; melanotropin receptor)-targeting ligand conjugated to the bifunctional, macrocyclic chelating agent tetra-azacyclododecanetetra-acetic acid (DOTA), and labeled with the alpha-emitting radioisotope actinium Ac 225, with potential antineoplastic activity. Upon administration of actinium Ac 225-DOTA-MTI-201, MT-201 targets and binds to MC1R-expressing melanoma cells, thereby specifically delivering a cytotoxic dose of alpha radiation to cells expressing MC1R. MC1R, a G protein-coupled receptor expressed by melanocytes that binds to melanocortins, is involved in regulating mammalian skin and hair color. It is upregulated on the surface of on uveal and cutaneous melanoma cells, but not in healthy normal tissues.