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PubChem CID
E number{{#property:P628}}
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Chemical and physical data
Molar mass555.238 g/mol

AM251 is a CB1 cannabinoid receptor antagonist. AM251 is structurally very close to SR 141716A (rimonabant), which both are biarylpyrazole cannabinoid receptor antagonists. In AM251 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 compound to SR 141716A, which has a Ki value of 11.5 nM. However AM251 is about two-fold more selective for the CB1 receptor when compared to SR 141716A.[1]


  1. Lan, R., Liu, Q., Fan, P., et al. Structure-activity relationships of pyrazole derivatives as cannabinoid receptor antagonists. J Med Chem 42 769-776 (1999). PubMed: 10052983