Profiling of dihydroorotate dehydrogenase, p38 and JAK inhibitors in the rat adjuvant-induced arthritis model: a translational study

BACKGROUND AND PURPOSE Translational animal models are essential in the prediction of the efficacy and side effects of new chemical entities. We have carried out a thorough study of three distinct disease-modifying antirheumatic drugs (DMARDs) in an adjuvant-induced arthritis (AIA) model in the rat and critically appraised the results in the context of the reported clinical experience in rheumatoid arthritis (RA) patients. EXPERIMENTAL APPROACH Teriflunomide a dihydroorotate dehydrogenase (DHODH) inhibitor; AL8697 a selective p38 MAPK inhibitor; and tofacitinib a Janus kinase (JAK) inhibitor; were selected as representatives of their class and dose-response studies carried out using a therapeutic 10-day administration scheme in arthritic rats. Paw swelling and body weight were periodically monitored, and joint radiology and histology, lymph organ weight and haematological and biochemical parameters evaluated at study completion. KEY RESULTS All three drugs demonstrated beneficial effects on paw swelling, bone lesions and splenomegalia, with p38 inhibition providing the best anti-inflammatory effect and JAK inhibition the best DMARD effect. Leukopenia, body weight loss and gastrointestinal toxicity were dose-dependently observed with teriflunomide treatment. p38 MAPK inhibition induced leukocytosis and increased total plasma cholesterol. JAK inhibition, normalized platelet, reticulocyte and neutrophil counts, and alanine aminotransferase (ALT) levels while inducing lymphopenia and cholesterolemia. CONCLUSIONS AND IMPLICATIONS This multiparametric approach can reveal specific drug properties and provide translational information. Whereas the complex profile for p38 inhibition in AIA is not observed in human RA, immunosuppressants such as DHODH and JAK inhibitors show DMARD properties and side effects seen in both AIA and RA.