Setmelanotide (RM-493), is an investigational, first-in-class melanocortin-4 receptor (MC4R) agonist in development for the treatment of rare genetic disorders of obesity. Setmelanotide is thought to activate the MC4R, part of a key biological pathway in humans that regulates weight by increasing energy expenditure and reducing appetite. Variants in genes within the MC4 pathway are associated with unrelenting hunger, known as hyperphagia, and severe, early-onset obesity. Setmelanotide is a potential replacement therapy that may restore lost activity in the MC4 pathway, reestablishing weight and appetite control in patients with these rare genetic disorders.