MN-25 (compound 4a) is an orally active indole pyridinone that functions as a novel cannabinoid ligand. It exhibits binding affinities (Ki) of 245 nM for CB1 and 11 nM for CB2 receptors. As a CB2 agonist, MN-25 inhibits TNF-R release from human peripheral blood mononuclear cells in vitro, with an IC50 of 33 μM. However, in an acute inflammation model in mice, MN-25 did not demonstrate efficacy at oral doses up to 50 mg/kg.

CB2:11 nM (Ki), CB1:254 nM (Ki)