Cilomilast(Ariflo, SB-207499) is among the first of a new generation of PDE4 inhibitors (Ki ≈100 nM). 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.