GSK-588045 is a serotonin 5-HT<sub>1A</sub>, 5-HT<sub>1B</sub>, and 5-HT<sub>1D</sub> receptor antagonist which was under development for the treatment of depressive and anxiety disorders but was never marketed. It is also a serotonin reuptake inhibitor, albeit much less potently than its serotonin 5-HT<sub>1</sub> receptor antagonism. The drug increases brain serotonin levels in animals. It was being developed by GlaxoSmithKline. GSK-588045 reached phase 1 clinical trials prior to the discontinuation of its development.