AT-56 inhibits human and mouse L-PGDSs in a concentration (3–250 μm)-dependent manner. AT-56 inhibits the L-PGDS activity in a competitive manner against the substrate PGH2 (Km = 14 μm) with a Ki value of 75 μm. AT-56 inhibits the production of PGD2 by L-PGDS-expressing human TE-671 cells after stimulation with Ca2+ ionophore (5 μm A23187) with an IC50 value of about 3 μm without affecting their production of PGE2 and PGF2α.
