CP 316311 is a potent and selective CRF1 receptor antagonist with an IC₅₀ value of 6.8 nM. IC50 & Target: IC50: 6.8 nM (CRF1 receptor)^[1] In Vitro: CP 316311 fully antagonizes CRF-stimulated adenylate cyclase activity in rat cortex and at human CRF1 receptors endogenously expressed in IMR32 cells with apparent K_i values of 7.6 and 8.5 nM, respectively^[1]. In Vivo: CP 316311 (3.2 mg/kg) inhibits ¹²⁵I-oCRF binding by >80% in rats. CP 316311 significantly attenuates activation of the hypothalamic−pituitary−adrenal (HPA) axis, with an MED value of 10 mg/kg, p.o. CP 316311 blocks the effects of both the exogenous and endogenous CRF in the CNS. CP 316311 blocks the effects induced by the exogeneous or endogeneous CRF in the brain in rat models^[1].