In vitro activity: Cilomilast produces a concentration-dependent increase in cAMP content in U937 cells. Cilomilast produces a concentration-dependent increase in cAMP content in U937 cells. In isolated human monocytes, Cilomilast and (R)-rolipram are equipotent at suppressing LPS-induced TNF-α formation with -log (IC50) of 7.0 and 7.2, respectively. Both Cilomilast and (R)-rolipram produces a modest prevention of fMLP-induced degranulation of human neutrophils. Cilomilast and (R)-rolipram are equipotent at suppressing neutrophil activation with -log (IC50) of 7.1 and 6.4, respectively. Cilomilast significantly decreases the expression of TNF-α in the cornea and IL-1α, IL-1β, and TNF-α in the conjunctivaas compared to vehicle control. Cilomilast treatment markedly decreases the presence of CD11b+ antigen-presenting cells in the central and peripheral cornea, and leads to decreased conjunctival expression of cytokines IL-6, IL-23, and IL-17. Moreover, Cilomilast decreases the expression of IL-17 and IL-23 in the draining lymph nodes. Cilomilast reduces TLR4 expression, IL-8 release and neutrophil chemotactic activity as well as it increased IP-10 release and lymphocyte chemotactic activity.

Kinase Assay: Cilomilast(SB 207499; Ariflo) is a potent PDE4 inhibitor with IC50 of about 110 nM, has anti-inflammatory activity and low central nervous system activity. IC50 value: 110 nM Target: PDE 4 Cilomilast (SB-207499) inhibits HPDE4 and LPDE4 catalytic activity with equal potency (Ki ≈100 nM). SB-207499 and rolipram are equipotent against LPDE4, but Cilomilast (Ariflo, SB-207499) is 100-fold less potent against HPDE4. This profile suggests that Cilomilast (Ariflo, SB-207499) retain the anti-inflammatory activity of rolipram yet have a decreased tendency to produce side effects.

Cell Assay: U937 cells (1-2 × 10 6) are incubated at 37 °C in a shaking water bath with Cilomilast for 1 min before the addition of 0.1 μM PGE2 (total volume of 200 μL). The incubation proceeds for an additional 4 min and is stopped by the addition of 0.1 mL of HClO4 (17.5%), neutralized with 0.15 ml of K23 (1.0 M) and diluted to 1 mL with sodium acetate buffer. Samples are centrifuged at 3000 × g for 10 min. Aliquots of the supernatant fraction are assayed for cAMP content by radioimmunoassay using commercially available kits.