Pharmacological characterization of a selective COX-2 inhibitor MF-tricyclic, [3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl)phenyl)-2-(5H)-furanone], in multiple preclinical species

Selective type 2 cyclooxygenase (COX-2) inhibitors are often used in preclinical studies without potency and selectivity data in the experimental species. To address this issue, we assessed a selective COX-2 inhibitor MF-tricyclic in four commonly used species, namely mice, rats, guinea pigs and rabbits, in the present study. In both the guinea pig and rabbit whole blood assay, the compound inhibited lipopolysaccharide (LPS)-induced PGE2 production with an IC50 (COX-2) of 0.6 and 2.8 μM, respectively. By comparison, the compound displayed a much weaker activity on clot-induced formation of thromboxane with an IC50 (COX-1) of > 10 μM (guinea pigs) and 23 μM (rabbits). In keeping with the in vitro potency data, the compound significantly inhibited interleukin-1 beta (IL-1β) -induced PGE2 formation in the rabbit synovium at plasma concentrations near the whole blood assay IC50 for COX-2 but much lower than that for COX-1. MF-tricyclic was also potent and selective toward COX-2 in mice, inhibiting carrageenan-induced PGE2 accumulation in the air pouch dose-dependently (ED50 = 0.5 mg/kg) without affecting stomach PGE2 levels. In rats, MF-tricyclic was found to be effective in three standard in vivo assays utilized for assessing COX-2 inhibitors, namely, LPS-induced pyresis, carrageenan-induced paw edema and adjuvant-induced arthritis at the doses that did not inhibit stomach PGE2 levels. Similar to that in rats, the compound displayed pharmacological efficacy in mice, guinea pigs and rabbits when tested in the LPS pyresis model. Our data reveal that MF-tricyclic has the desired biochemical and pharmacological properties for selective COX-2 inhibition in all four test species.