Melanotan II (CAS NO. 121062-08-6) was first synthesized at the University of Arizona. Researchers decided to find a more potent and stable alternative, one that would be more practical to defenses against skin cancer.
It was under development as drug candidate for female sexual dysfunction and erectile dysfunction,
Melanotan II acts as a non-selective agonist of the melanocortin receptors.
The melanogenesis produced by Melanotan II is caused by activation of the MC1 receptor, whereas its sexual effects are thought to be related to its ability to activate the MC4 receptor (though the MC3 is thought to possibly also be involved).