Viral 'Barbie drug' for tanning can cause brain swelling and even cancer, experts warn Your body already makes a hormone that tells your skin to tan. Melanotan 2 is a synthetic peptide engineered to mimic that hormone but in a version that's more potent and longer lasting than Melanotan II (MT II) Peptide Therapy Beverly Hills Structure of Melanotan II and bremelanotide. Download Scientific Diagram Melanotan 2 Injectable Peptide