DPP4 and insomnia: These molecules are: celecoxib and lonazolac, approved COX-2 inhibitor drugs [6,7]; crizotinib [8], an anticancer drug; sildenafil [8] (Viagra), a PDE5 inhibitor; zometapine [9], an antidepressant; lorediplon A, used for the treatment of insomnia [10]; anagliptin E, an inhibitor of dipeptidyl peptidase-4 (DPP-4) for the treatment of type 2 diabetes mellitus [11] (Figure 2); and many others.