{ { Drugbox
| verifiedrevid = 449586687
| IUPAC_name = N-(1-Methyl-1H-indol-5-yl)-''N-(3-methylisothiazol-5-yl)urea
| image = SB-204,741_structure.png
| width = 220
| tradename =
| pregnancy_AU =
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| CAS_number_Ref =
| CAS_number = 152239-46-8
| UNII_Ref =
| UNII = 9VHM49MS42
| ATC_prefix =
| ATC_suffix =
| PubChem = 3277600
| ChEBI = 140936
| IUPHAR_ligand = 221
| DrugBank_Ref =
| DrugBank =
| ChemSpiderID = 2526822
| C=14 | H=14 | N=4 | O=1 | S=1
| smiles = c2c(C)nsc2NC(=O)Nc3ccc1n(C)ccc1c3
| synonyms = SB-204,741
| StdInChI = 1S/C14H14N4OS/c1-9-7-13(20-17-9)16-14(19)15-11-3-4-12-10(8-11)5-6-18(12)2/h3-8H,1-2H3,(H2,15,16,19) | StdInChIKey = USFUFHFQWXDVMH-UHFFFAOYSA-N }}SB-204741''' is a drug which acts as a potent and selective antagonist at the serotonin 5-HT2B receptor, with around 135x selectivity over the closely related 5-HT2C receptor, and even higher over the 5-HT2A receptor and other targets. It is used in scientific research for investigating the functions of the 5-HT2B receptor.