am-251 (drug) am-251 (drug) am-251 is an inverse agonist at the cb1 cannabinoid receptor. am-251 is structurally very close to rimonabant; both are biarylpyrazole cannabinoid receptor antagonists. in am-251, the p-chloro group attached to the phenyl substituent at c-5 of the pyrazole ring is replaced with a p-iodo group. the resulting compound exhibits slightly better binding affinity for the cb1 receptor (with a ki value of 7.5 nm) than rimonabant, which has a ki value of 11.5 nm, am-251 is, however, about two-fold more selective for the cb1 receptor when compared to rimonabant. like rimonabant, it is additionally a μ-opioid receptor antagonist that attenuates analgesic effects. am-251identifiers iupac name 1-(2,4-dichlorophenyl)-5-(4-iodophenyl)-4-methyl-n-(1-piperidyl)pyrazole-3-carboxamide cas number183232-66-8 ypubchem cid2125iuphar/bps3317chemspider2040 yunii3i4fa44maichebichebi:90724 ychemblchembl285932 ycomptox dashboard (epa)dtxsid7042695 echa infocard100.162.062 chemical and physical dataformulac22h21cl2in4omolar mass555.24 g·mol−13d model (jsmol)interactive image smiles o=c(nn1ccccc1)c4nn(c2ccc(cl)cc2cl)c(c3ccc(i)cc3)c4c inchi inchi=1s/c22h21cl2in4o/c1-14-20(22(30)27-28-11-3-2-4-12-28)26-29(19-10-7-16(23)13-18(19)24)21(14)15-5-8-17(25)9-6-15/h5-10,13h,2-4,11-12h2,1h3,(h,27,30) ykey:buzajrplugxrab-uhfffaoysa-n y (verify) am251 has shown an in vitro antimelanoma activity against pancreatic and colon cancer cells.