PDE4-IN-18 (compound 1l) is a PDE4 inhibitor ( IC 50 =1.55 μM) with anti-inflammatory activity. PDE4-IN-18 exerts anti-inflammatory effects by reducing excessive immune cell infiltration and intestinal membrane formation, as well as reducing the mRNA expression of pro-inflammatory cytokines (such as TNF-α and IL-6 ) in synovial tissue. PDE4-IN-18 can be used in the study of rheumatoid arthritis and psoriasis.