Background Orally available small molecular weight compounds with ability to suppress the proinflammatory mediator Tumour Necrosis Factor alpha (TNF) are of high interest for the treatment of rheumatoid arthritis (RA). Roflumilast (3-cyclopropylmethoxy-4-difluoromethoxy-N-[3,5-di-chloropyrid-4-yl]-benzamide) is a highly potent and selective inhibitor of phosphodiesterase type 4 (PDE4), that effectively suppresses TNF production in vitro and in vivo.1,2 This compound is currently in clinical development for asthma and COPD.
Objectives We investigated the capacity of Roflumilast to reduce the release of TNF in vivo in mice, and also examined its antiarthritic potential in murine collagen-induced arthritis (CIA).
Methods For induction of systemic TNF release, male BALB/c mice were injected intraperitoneally with lipopolysaccharide (LPS, S. abortus equi, 5 mg/kg). Mice were orally treated with 1 or 10 mg/kg of Roflumilast 30 min prior to LPS challenge. Plasma was obtained 90 min after challenge for determination of cytokines by ELISA. CIA was induced in male DBA/1 mice by intradermal injection of 200 μg of type II collagen (CII) in Freund?s complete adjuvant, followed by a booster injection of CII on day 21 (200 μg in PBS i.p.). Roflumilast (1 or 5 mg/kg) was given once daily p.o. on days 23‑33. Arthritic scores (0‑3) and paw thicknesses were monitored between days 21‑39. In parallel experiments, groups of mice were sacrificed and cells from draining lymph nodes were restimulated in vitro with graded concentrations of CII. TNF, Interleukin-6 (IL-6), and Interferon-gamma (IFN), released within 72 h of in vitro culture, were measured by ELISA. Histological analysis was performed on joints taken on day 35 after primary immunisation.
Results Roflumilast dose-dependently suppressed LPS-induced TNF production in vivo (75% with 10 mg/kg). By contrast, plasma levels of the anti-inflammatory cytokine Interleukin-10 were substantially raised (500% with 10 mg/kg). In addition, Roflumilast dose-dependently protected mice against CIA. This was also evident histologically by a significant reduction of joint inflammation and bone/cartilage erosion. The in vitro capacity of lymph node cells to produce TNF, IL-6, and IFN upon CII-stimulation was markedly reduced, even when cells were prepared one week after withdrawal of drug treatment.
Conclusion These data demonstrate that Roflumilast is a promising candidate for the oral treatment of rheumatoid arthritis.
Bundschuh DS, et al. J Pharmacol Exp Ther., in press
Hatzelmann A, et al. J Pharmacol Exp Ther., in press