Melanotan II is a synthetic cyclic heptapeptide that mimics the activity of α-melanocyte-stimulating hormone (α-MSH) by binding to melanocortin receptors, particularly MC1R. It has been extensively studied for its melanogenic effects, primarily increasing melanin synthesis in skin cells, leading to enhanced pigmentation.

In addition to its role in skin photoprotection, Melanotan II has shown activity at other melanocortin receptors, such as MC3R and MC4R, which are involved in regulating appetite, energy homeostasis, and sexual function. This has led to secondary research into its effects on libido, mood regulation, and metabolic processes.

Studies have also explored its potential to protect skin from UV radiation by increasing natural pigmentation, thereby reducing the risk of photodamage. However, Melanotan II remains an experimental compound and is not approved for clinical use. Its multifaceted receptor activity continues to make it a subject of interest in dermatological, neurological, and metabolic research.