Synthesis and Structure−Activity Relationships of 8-(Pyrid-3-yl)pyrazolo[1,5-a]-1,3,5-triazines: Potent, Orally Bioavailable Corticotropin Releasing Factor Receptor-1 (CRF₁) Antagonists

This report describes the syntheses and structure-activity relationships of 8-(substituted pyridyl)pyrazolo[1,5-a]-1,3,5-triazine corticotropin releasing factor receptor-1 (CRF1) receptor antagonists. These CRF1 receptor antagonists may be potential anxiolytic or antidepressant drugs. This research resulted in the discovery of compound 13-15, which is a potent, selective CRF1 antagonist (hCRF(1) IC50 = 6.1 +/- 0.6 nM) with weak affinity for the CRF-binding protein and biogenic amine receptors. This compound also has a good pharmacokinetic profile in dogs. Analogue 13-15 is orally effective in two rat models of anxiety: the defensive withdrawal (situational anxiety) model and the elevated plus maze test. Analogue 13-15 has been advanced to clinical trials.