Identification and biochemical analyses of selective CB2 agonists.

Cannabinoid CB1 and CB2 receptors are activated by Δ9-tetrahydrocannabinol, a psychoactive component of marijuana. The cannabinoid CB1 receptor is primarily located in the brain and is responsible for the psychoactive side effects, whereas the cannabinoid CB2 receptor is located in immune cells and is an attractive target for immune-related maladies. We identify small molecules that selectively bind to the cannabinoid CB2 receptor and can be further developed into therapeutics. The affinity of three molecules, ABK5, ABK6, and ABK7, to the cannabinoid CB2 receptor was determined with radioligand competition binding. The potency of G-protein coupling was determined with GTPγS binding. The three compounds bound selectively to the cannabinoid CB2 receptor, and no binding to the cannabinoid CB1 receptor was detected up to 10 μM. Immunoblotting studies show that the amount of ERK1/2 and MEK phosphorylation increased in a Gi/o-dependent manner. Furthermore, an immune cell line (Jurkat cells) was treated with ABK5, and as a result, inhibited cell proliferation. These three compounds are novel cannabinoid CB2 receptor agonists and hold promise to be further developed to treat inflammation and the often-associated pain.