csp-2503 csp-2503 csp-2503 is a potent and selective 5-ht1a receptor agonist, 5-ht2a receptor antagonist, and 5-ht3 receptor antagonist of the phenylpiperazine class. first synthesized in 2003, it was designed based on computational models and qsar studies. in rat studies, csp-2503 has demonstrated anxiolytic effects, and thus has been suggested as a treatment for anxiety in humans with a multimodal mechanism of action. csp-2503clinical dataatc codenoneidentifiers iupac name 2-hexahydropyrrolopyrazine-1,4-dione cas number581813-10-7pubchem cid10317515chemspider8492979 yunii87ukl3xe5xchemblchembl285066 ychemical and physical dataformulac22h26n4o2molar mass378.476 g·mol−13d model (jsmol)interactive image smiles o=c4n5cccc5c(=o)n(cn3ccn(c2c1ccccc1ccc2)cc3)c4 inchi inchi=1s/c22h26n4o2/c27-21-15-25(22(28)20-9-4-10-26(20)21)16-23-11-13-24(14-12-23)19-8-3-6-17-5-1-2-7-18(17)19/h1-3,5-8,20h,4,9-16h2 ykey:ctzwgzsinbfhfd-uhfffaoysa-n y (verify)