Cayman AT-56

Prostaglandin D synthase (PGDS) catalyzes the isomerization of PGH₂ to produce PGD₂. PGD₂ induces sleep, regulates nociception, inhibits platelet aggregation, and acts as an allergic mediator. Two distinct types of PGDS have been identified, namely the lipocalin-type enzyme (β-trace, L-PGDS) and the hematopoietic-type enzyme (H-PGDS).^1,2,3 L-PGDS is localized in the central nervous system, male genital organs of various mammals, and the human heart and is a major protein in human cerebrospinal fluid (CSF).¹ AT-56 is a selective, competitive, and highly bioavailable inhibitor of lipocalin-type prostaglandin D synthase (L-PGDS) with a K_i value of 75 µM.⁴ It inhibits the production of PGD₂ by L-PGDS-expressing cells purified from human CSF and recombinant mouse cells with an IC₅₀ value of 95 µM.⁴ At concentrations as high as 100 µM in vitro or 30 mg/kg in vivo, AT-56 does not affect the production of PGE₂, PGF_2α, or H-PGDS-catalyzed PGD₂.⁴ At 10 mg/kg AT-56, the numbers of total cells, infiltrating eosinophils, and monocytes in bronchoalveolar lavage fluid of L-PGDS transgenic mice were decreased to 23, 6, and 41% of controls, respectively.⁴

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