Highly potent, selective OX2 receptor antagonist (IC50 values are 2.3 nM and 1900 nM for OX2 and OX1 respectively). Displays negligible or no inhibition of a panel of 80 receptors. Blocks orexin-B- and orexin-A-invoked calcium mobilization in hOX2-expressing CHO cells (IC50 values are 7.9 nM and 8.8 nM respectively); reverses orexin-B-induced hyperlocomotion in mice. Brain penetrant. Purity 98%. MW (observed): 454.54