Melanotan II is a synthetic cyclic peptide analog of alpha-melanocyte-stimulating hormone (α-MSH) supplied for Research Use Only (RUO) in laboratory studies involving melanocortin receptor signaling, particularly pathways associated with MC1R, MC3R, MC4R, and MC5R activity. It is commonly investigated in preclinical and in vitro research models related to melanogenesis, pigmentation biology, energy-balance signaling, appetite-regulation pathways, and neuroendocrine peptide activity. Melanotan II is intended strictly for controlled laboratory research and analytical applications. Not for human or animal consumption, therapeutic use, diagnostic use, cosmetic use, or clinical application.