Orexin receptors are activated by the endogenous polypeptides orexin-A and orexin-B (also known as hypocretin-1 and -2; 33 and 28 aa) derived from a common precursor, preproorexin or orexin precursor, by proteolytic cleavage and some typical peptide modifications . Currently the only orexin receptor ligands in clinical use are suvorexant and lemborexant, which are used as hypnotics. Orexin receptor crystal structures have been solved [2,3,4,5,6].
Sakurai T, Amemiya A, Ishii M, et al. Orexins and orexin receptors: a family of hypothalamic neuropeptides and G protein-coupled receptors that regulate feeding behavior. Cell 1998;92:573-85.
Yin J, Mobarec JC, Kolb P, et al. Crystal structure of the human OX2 orexin receptor bound to the insomnia drug suvorexant. Nature 2015;519:247-50.