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Timapiprant, also known as OC000459, is a potent, selective and orally active CRTH2 antagonist. OC000459 reduces nasal and ocular symptoms in allergic subjects exposed to grass pollen, a randomised, placebo-controlled, double-blind trial. OC000459 inhibits mast cell-dependent activation of T helper 2 lymphocytes and eosinophils. OC000459 treatment inhibited LAR and post-allergen increase in sputum eosinophils. OC000459 appears to inhibit allergic inflammation in asthma.

Timapiprant sodium (OC000459 sodium) is a potent, selective, and orally active D prostanoid receptor 2 (DP2, also known as CRTH2) antagonist. Timapiprant sodium (OC000459 sodium) potently displaces [3H] PGD2 from human recombinant DP2 (Ki=13 nM), rat recombinant DP2 (Ki=3 nM), and human native DP2 (Ki=4 nM). Timapiprant sodium (OC000459 sodium) inhibits mast cell activation of Th2 lymphocytes and eosinophils[1].

[1] Singh D, Cadden P, Hunter M, Inhibition of the asthmatic allergen challenge response by the CRTH2 antagonist OC000459. Eur Respir J. 2013 Jan;41(1):46-52. DOI:10.1183/09031936.00092111
[2] Horak F, Zieglmayer P, Zieglmayer R, The CRTH2 antagonist OC000459 reduces nasal and ocular symptoms in allergic subjects exposed to grass pollen, a randomised, placebo-controlled, double-blind trial. Allergy. 2012 Dec;67(12):1572-9. DOI:10.1111/all.12042
[3] Pettipher R, Vinall SL, Xue L, Pharmacologic profile of OC000459, a potent, selective, and orally active D prostanoid receptor 2 antagonist that inhibits mast cell-dependent activation of T helper 2 lymphocytes and eosinophils. J Pharmacol Exp Ther. 2012 DOI:10.1124/jpet.111.187203