AT-56

AT-56 is an orally active inhibitor of lipocalin-type prostaglandin D synthase (L-PGDS) (Ki = 75 μM, IC50 = 95 μM). AT-56 Inhibits the production of PGD2 from PGH2 in vitro, with no effect on PGE2 or PGF2α production. AT-56 inhibited human and mouse L-PGDSs in a concentration (3-250 microm)-dependent manner. AT-56 inhibits the L-PGDS activity in a competitive manner against the substrate PGH(2) (K(m) = 14 microm) with a K(i) value of 75 microm. AT-56 did not inhibit the binding of 13-cis-retinoic acid,which is a nonsubstrate lipophilic ligand, to L-PGDS.