Novel, low potency CB2 receptor silent antagonist and CB1 receptor partial inverse agonist. Competitively antagonizes effects of CP 55,940 (pA2 = 6.1) and SR 144528 (pEC50 = 5.3) at CB2 receptors and acts as a partial inverse agonist at CB1 receptors (pIC50 = 5.5). Displays modest activity at human melatonin MT1 and muscarinic M4 receptors, but is selective over several other GPCRs.