Pharmacological evaluation of a novel cannabinoid 2 (CB2) ligand, PF-03550096, in vitro and in vivo by using a rat model of visceral hypersensitivity

Previous studies have shown that cannabinoid 2 (CB(2))-receptor agonists might have analgesic effects on visceral hypersensitivity. To extend these results, we have determined the pharmacological characteristics of a newly designed CB(2) ligand, N-[(1S)-1-(aminocarbonyl)-2,2-dimethylpropyl]-3-(3-hydroxy-3-methylbutyl)-2-oxo-2,3-dihydro-1H-benzimidazole-1-carboxamide (PF-03550096), in vitro and in vivo. PF-03550096 showed high affinity to human (K(i) = 7.9 +/- 1.7 nM) and rat CB(2) receptors (K(i) = 47 +/- 5.6 nM). In a cell-based functional assay, PF-03550096 behaved as a full agonist and showed high selectivity for human CB(2) receptors. Orally administered PF-03550096 (3, 10 mg/kg) inhibited the 2,4,6-trinitrobenzene sulfonic acid (TNBS)-induced decrease in colonic pain threshold with statistical significance. The inhibitory effect of PF-03550096 (10 mg/kg) was significantly reversed by a selective CB(2) antagonist, N-(1S)-endo-1,3,3-trimethylbicyclo[2.2.1]heptan-2-yl-5-(4-chloro-3-methylphenyl)-1(4-methylbenzyl)-pyrazole-3-carboxamide (SR144528), while SR144528 itself did not modify colonic pain threshold. These results indicate that PF-03550096 is a potent CB(2) agonist and possesses efficacy in a rat model of visceral hypersensitivity.