Melanotan II


Melanotan II is a synthetic analogue of the peptide hormone α-melanocyte-stimulating hormone.
It was under development as drug candidate for female sexual dysfunction and erectile dysfunction but clinical development ceased by 2003, and as of 2018, no product containing melanotan II was marketed and all commercial development had ceased. Unlicensed, untested, or fraudulent products sold as "melanotan II" are found on the Internet, and purported to be effective as "tanning drugs", though side effects such as uneven pigmentation, new nevi, and darkening or enlargement of existing moles are common and have led to medical authorities discouraging use.

Mechanism of action

Melanotan II acts as a non-selective agonist of the melanocortin receptors MC1, MC3, MC4, and MC5.
To the extent that melanotan II produces melanogenesis, this is thought to be caused by activation of the MC1 receptor, whereas its clinically documented sexual effects are thought to be related to its ability to activate the MC4 receptor.
Other effects of melanotan II, mostly regarded as adverse effects, include flushing, nausea, vomiting, stretching, yawning, and loss of appetite.

History

Research in the early 1960s showed that in rats, administration of α-MSH caused sexual arousal, and work on this continued in many labs up through the 1980s, when scientists at University of Arizona began attempting to develop α-MSH and analogs as potential sunless tanning agents, and synthesized and tested several analogs, including melanotan-I and melanotan II.
Very early in the process one of the scientists, who was conducting experiments on himself with an early tool compound, melanotan II, injected himself with twice the dose he intended and got an eight-hour erection, along with nausea and vomiting.
To pursue the tanning agent, melanotan-I was licensed by Competitive Technologies, a technology transfer company operating on behalf of University of Arizona, to an Australian startup called Epitan, which changed its name to Clinuvel in 2006.
To pursue the sexual dysfunction agent, melanotan-II was licensed by Competitive Technologies to Palatin Technologies. Palatin ceased development of melanotan-II in 2000 and synthesized, patented, and began to develop bremelanotide, a likely metabolite of melanotan-II that differs from melanotan-II in that it has a hydroxyl group where melanotan-II has an amide. Competitive Technologies sued Palatin for breach of contract and to try to claim ownership of bremelanotide; the parties settled in 2008 with Palatin retaining rights to bremelanotide, returning rights to melanotan-II to Competitive Technologies, and paying $800,000.
Bremelanotide was approved for use in the United States by the Food and Drug Administration in June 2019 under the brand name Vyleesi to treat hypoactive sexual desire disorder.

Society and culture

A number of products are sold online and in gyms and beauty salons as "melanotan" or "melanotan-1" or "melanotan-2" in their marketing.
The unregulated products are not legal to be sold for human usage in any jurisdiction.
Starting in 2007 health agencies in various countries began issuing warnings against their use.