Pexacerfont is a highly potent and selective CRF1 receptor antagonist that displays no agonist properties. It is specific for CRF1 receptors and has more than 1,000- fold less affinity for CRF2 receptors, and more than 100- fold less affinity for the CRF-binding protein. In extensive preclinical studies, pexacerfont has been shown to inhibit specific binding of CRF to rat, dog, monkey, and human CRF1 receptors. The functional anxiolytic effects of CRF1 receptor occupancy were demonstrated in two rodent models of anxiety, situational anxiety and elevated plus maze paradigms. Pexacerfont did not demonstrate efficacy compared to placebo for the treatment of generalized anxiety disorder in human. The bogus taste tests suggested some protective effect of pexacerfont against eating after a laboratory stressor. Pexacerfont had been in phase II clinical trials for the treatment of irritable bowel syndrome and depression depression.