ICI-170809, also known as ZM-170809, is a selective serotonin 5-HT<sub>2</sub> receptor antagonist which was under development for the treatment of major depressive disorder, arrhythmias, thrombosis, and ischemic heart disorders but was never marketed. It was being developed by AstraZeneca. The drug reached phase 2 clinical trials prior to the discontinuation of its development.