Illustration of the in vitro receptor pharmacology
at the mMC3R and mMC4R for tetrapeptides 1 (Trp), 6 [Nal(2′)], and 7 [DNal(2′)],
Ac-Xaa-(pI)DPhe-Arg-Trp-NH2 and SHU9119 Ac-Nle-c[Asp-His-DNal(2′)-Arg-Trp-Lys]-NH2. The SHU9119 is a representative mMC3R/mMC4R antagonist that
possesses mMC3R partial agonist activity, whereas 1, 6, and 7 possess minimal agonist activity at
concentrations of 100 μM.