The aim of this study was to assess the effects of a new purine-2,6-dione derivative, compound 34 (Figure 1), being a strong inhibitor of PDE4 and PDE7 in animal models of ADs, namely MOG35–55-induced EAE in mice, which is a model of MS [10], collagen-induced arthritis (CIA) in rats, which is a model of RA [24], and ConA-induced hepatitis in mice that, in many aspects, resembles human AIH [20]. Here, PDE4A is linked to rheumatoid arthritis.