MT-1 (melanotan I, INN afamelanotide) is [Nle4, D-Phe7]-alpha-MSH, also abbreviated NDP-MSH: a linear 13-residue analogue of alpha-melanocyte-stimulating hormone in which methionine 4 is replaced by norleucine and phenylalanine 7 by its D-isomer. It was described in 1980. Early research used pigment cell bioassays in frog and lizard skin and mouse melanoma cells, followed by toxicology studies in mice. A review by the originating group traces the development of melanotan I and the related cyclic analogue melanotan II. Afamelanotide has also been the subject of registered clinical trials.