PDE4-IN-6 is a potent, safe and moderately selective PDE4 inhibitor with IC 50 s of 0.125 and 0.43 µM for PDE4B and PDE4D, respectively. PDE4-IN-6 can downregulate the expression level of TNF-α and IL-6. PDE4-IN-6 has potent immunomodulatory activity thereby its potential against rheumatoid arthritis. Anti-inflammatory and anti-arthritic effects.