Development of an orexin-2 receptor selective agonist, [Ala11, -Leu15]orexin-B

Investigation of -alanine and -amino acid replacement of orexin-B revealed that three -leucine residues at the positions of 11, 14, and 15 in orexin-B were important to show selectivity for the orexin-2 receptor (OX2) over the orexin-1 receptor (OX1). -Alanine substitution at position 11 and -leucine substitution at positions 14 and 15 maintained the potency of orexin-B to mobilize [Ca2+]i in CHO cells expressing the OX2, while their potency for the OX1 was significantly reduced. In combined substitutions, we identified that [Ala11, -Leu15]orexin-B showed a 400-fold selectivity for the OX2 (EC50=0.13 nM) over OX1 (EC50=52 nM). [Ala11, -Leu15]orexin-B is a beneficial tool for addressing the functional roles of the OX2.