Cinanserin (; developmental code name SQ-10643) is a serotonin 5-HT2A and 5-HT2C receptor antagonist which was discovered in the 1960s and was never marketed. It has about 50-fold higher affinity for the 5-HT2A receptor than for 5-HT2C, and very low affinity for 5-HT1 receptors. The drug also inhibits the 3C-like protease of SARS-CoV-1 and SARS-CoV-2, but with much lower affinity.
{{Drugbox | Verifiedfields = changed | verifiedrevid = 449572536 | image = Cinanserin.svg | image_class = skin-invert-image | width = 250px
| tradename = | pregnancy_category = | legal_status = | routes_of_administration = | class = Serotonin 5-HT2 receptor antagonist; Serotonin 5-HT2A receptor antagonist | ATC_prefix = None | ATC_suffix =
Discovered by embedding cosine similarity (sentence-transformers MiniLM, 384-dim).