SR144528 is an antagonist of the CB2 receptor (Ki = 0.6 nM) and inhibits microsomal ACAT activity (IC50 = 3.6 μM).

(S)-AM1241 binds to cannabinoid (CB) receptors and is selective for the CB2 over the CB1 receptor (Kis = 658 and >10,000 nM, respectively, in a membrane assay using human receptors). (S)-1241 acts as an agonist at human, rat, and mouse CB2 receptors but shows greater activity at human CB2 (EC50 = 131 nM) than at rat and mouse CB2 receptors (EC50 = 785 and 2,000 nM, respectively). Similar to the racemate AM1241 , (S)-AM1241 produces antinociception to thermal, but not mechanical, pain in rats. The pain-reducing effect of (S)-AM1241 is blocked by the CB2-specific inhibitor SR 144528 but not by either the CB1-selective inhibitor rimonabant or the opioid receptor blocker naloxone .

(R)-AM1241 binds to cannabinoid (CB) receptors and has greater than 100-fold selectivity for the CB2 over the CB1 receptor (Kis = 15 and 5,000 nM, respectively, in a membrane assay using human receptors). (R)-AM1241 acts as an agonist at human CB2 receptors (EC50 = 118 nM) but an inverse agonist at rat and mouse CB2 receptors (EC50s = 315 and 341 nM, respectively). Similar to the racemate AM1241 , (R)-AM1241 produces antinociception to thermal, but not mechanical, pain in rats. The pain-reducing effect of (R)-AM1241 is blocked by the CB2-specific inhibitor SR 144528 but not by either the CB1-selective inhibitor rimonabant or the opioid receptor blocker naloxone .

(±)-WIN 55,212-2 is a potent aminoalkylindole cannabinoid (CB) receptor agonist with a Ki value of 62.3 and 3.3 nM for human recombinant central cannabinoid (CB1) and peripheral cannabinoid (CB2) receptors, respectively. In contrast, the enantiomer (-)-WIN 55,212-3 acts a partial inverse agonist at CB1 (pIC50 = 5.5) and as a competitive neutral antagonist of CB2, reversing the inverse agonism evoked by SR 144528 (pEC50 = 5.3). (+)-WIN 55,212 (mesylate) is a mixture of the two enantiomers, (+)-WIN 55,212-2 and (-)-WIN 55,212-3.