Actually the bremelanotide (PT-141) precursor melanotan II was the first scientifically developed drug to be established as having aphrodisiac effects.
Palatin Technologies the company that licensed melanotan II (which they called 'PT-14') for development went on to develop PT-141. They claimed that it was improved over melanotan II but a more likely explanation is that they wanted to get out from underneath the licensing requirements of melanotan II so they made some slight alterations to it. Both melanotan II and bremelanotide are what is known as alpha-melanocyte stimulating hormone analogs. They act as melanocortin receptor agonists.
