LAUSR

3,3′‐Diindolylmethane (DIM), a natural product‐derived compound formed upon ingestion of cruciferous vegetables, was recently described to act as a partial agonist of the anti‐inflammatory cannabinoid (CB) receptor subtype CB2. In the present study, we synthesized and evaluated a series of DIM derivatives and determined their affinities for human CB receptor subtypes in radioligand binding studies. Potent compounds were additionally evaluated in functional cAMP accumulation and β‐arrestin recruitment assays. Small substituents in the 4‐position of both indole rings of DIM were beneficial for high CB2 receptor affinity and efficacy. Di‐(4‐cyano‐1H‐indol‐3‐yl)methane (46, PSB‐19837, EC50: cAMP, 0.0144 µM, 95% efficacy compared to the full standard agonist CP55,940; β‐arrestin, 0.0149 µM, 67% efficacy) was the most potent CB2 receptor agonist of the present series. Di‐(4‐bromo‐1H‐indol‐3‐yl)methane (44, PSB‐19571) showed higher potency in β‐arrestin (EC50 0.0450 µM, 61% efficacy) than in cAMP accumulation assays (EC50 0.509 µM, 85% efficacy) while 3‐((1H‐indol‐3‐yl)methyl)−4‐methyl‐1H‐indole (149, PSB‐18691) displayed a 19‐fold bias for the G protein pathway (EC50: cAMP, 0.0652 µM; β‐arrestin, 1.08 µM). DIM and its analogs act as allosteric CB2 receptor agonists. These potent CB2 receptor agonists have potential as novel drugs for the treatment of inflammatory diseases.