In vitro activity: URB602 is a selective inhibitor of the monoacylglycerol lipase (MGL) which inhibits rat brain MGL enzyme with IC50 of 28±4 μM via a noncompetitive mechanism. MGL is a serine hydrolase involved in the biological deactivation of the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG). Pretreatment with URB602 protects from the long-term consequences of neonatal hypoxic-ischemic brain injury in rats. URB602 inhibits monoacylglycerol lipase and selectively blocks 2-arachidonoylglycerol degradation in intact brain slices. RB602 (100 microM) elevates 2-AG levels in hippocampal slice cultures without affecting levels of other endocannabinoid-related substances. Thus, URB602 may provide a useful tool by which to investigate the physiological roles of 2-AG and explore the potential interest of MGL as a therapeutic target. Without URB602, the apparent Michaelis constant (Km) of MGL for 2-AG is 24±1.7 μM and the maximum velocity (Vmax) is 1814±51 nmol min per mg protein; with URB602, the Km is 20±0.4 μM and the Vmax is 541±20 nmol min per mg protein (n=4). When organotypic slice cultures of rat forebrain are incubated with URB602 (100 μM), both baseline and Ca2+-ionophore-stimulated 2-arachidonoylglycerol (2-AG) concentrations are increased. URB602 is an inhibitor of monoacylglycerol lipase (MGL), a serine hydrolase involved in the biological deactivation of the endocannabinoid 2-arachidonoyl-sn-glycerol (2-AG). URB602 weakly inhibits recombinant MGL (IC50=223±63 μM) through a rapid and noncompetitive mechanism.

Kinase Assay: Samples containing either URB602 (300 μM), MGL (1.4 pM), or both URB602 and MGL are incubated at 37°C for 30 min in assay buffer. At various time points, the reaction is stopped with an equal volume of ice-cold methanol and directly analyzed in positive ionization mode by LC/MS. A SB-CN column (150×2.1 mm i.d., 5 μm) eluted is used with a linear gradient of methanol in water containing 0.25% acetic acid and 5 mM ammonium acetate (from 60% to 100% of methanol in 8 min) at a flow rate of 0.5 mL/min with column temperature at 50°C. Capillary voltage is set at 4 kV and fragmentor voltage is 100V. Nebulizer pressure is set at 60 psi. N2 is used as drying gas at a flow rate of 13 liters/min and a temperature of 350°C. ESI is in the positive mode and a full scan spectrum is acquired from m/z 100 to 600. Extracted ion chromatograms are used to quantify URB602 ([M+H]+, m/z 296).

Cell Assay: RB602 (100 microM) elevates 2-AG levels in hippocampal slice cultures without affecting levels of other endocannabinoid-related substances.