Characterisation of the Urokinase Plasminogen Activation (uPA) System in the Rat Collagen Induced Arthritis Model: Pharmacological Investigations of Methotrexate and uPA Inhibition

Rheumatoid arthritis (RA) is a chronic inflammatory disease of synovial joints. Accumulating evidence implicates the pathogenic role of the urokinase plasminogen activation system (uPAS) in RA and experimental arthritis models. Collagen-induced arthritis (CIA) is one of the most widely used and clinically relevant models of RA for the evaluation of novel anti-arthritic therapeutic candidates. Urokinase plasminogen activator-directed monoclonal antibodies have shown ameliorating effects in a mouse model of CIA. Previous efforts in our laboratory produced novel amiloride analogues as inhibitors of human uPA with improved selectivity over other trypsin-like serine proteases (TLSPs). The lead compound, BB2-30F, completely eliminated metastasis in uPA-driven mouse xenograft cancer models, suggesting the potential for its use in inflammatory disease models such as RA where uPAS is upregulated. As evident from the literature, the CIA model in rats more closely recapitulates human RA than equivalent models in mice. This motivated our selection of rat CIA for testing the effects of BB2-30F in this disease model. However, the uPAS has not been characterised in rat CIA. Thus, the overall objectives of the study were to characterise uPAS in female Lewis rat CIA and then to investigate the in vivo efficacy of BB2-30F compared to the standard of care treatment methotrexate (MTx).