The story

In the 1980s Mac Hadley and Victor Hruby at the University of Arizona built Melanotan II as a sunless tanning peptide. Volunteers kept reporting spontaneous erections, and Hunter Wessells at Arizona confirmed it caused erections in men with psychogenic erectile dysfunction. Palatin Technologies in New Jersey then made bremelanotide, PT-141, keeping the desire effect. James Pfaus in Montreal showed it raised female desire, not just arousal, in animals, and in 2019 it was registered in the US for low desire in women.