MC4R and hyperinsulinemic hypoglycemia, familial, 4: The successful use of setmelanotide has opened doors for clinical trials of treatments for other monogenic deficiencies of the leptin–melanocortin pathway, such as MC4R-deficiency (which occurs in a far larger cohort than POMC deficiency) and leptin receptor deficiency the sufferers of which, for obvious reasons, are resistant to leptin treatment.