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
Author
Pettipher, Roy
Vinall, Shan L.
Xue, Luzheng
Speight, Graham
Townsend, Elizabeth R.
Gazi, Lucien
Whelan, C.J.
Armer, Richard E.
Payton, Mark A.
Hunter, Michael G.
Attention
2299/7812
Abstract
D prostanoid receptor 2 (DP2) [also known as chemoattractant receptor-homologous molecule expressed on T helper 2 (Th2) cells (CRTH2)] is selectively expressed by Th2 lymphocytes, eosinophils, and basophils and mediates recruitment and activation of these cell types in response to prostaglandin D-2 (PGD(2)). (5-Fluoro-2-methyl-3-quinolin-2-ylmethylindo-1-yl)-acetic acid (OC000459) is an indole-acetic acid derivative that potently displaces [H-3]PGD(2) from human recombinant DP2 (K-i = 0.013 mu M), rat recombinant DP2 (K-i = 0.003 mu M), and human native DP2 (Th2 cell membranes; K-i = 0.004 mu M) but does not interfere with the ligand binding properties or functional activities of other prostanoid receptors (prostaglandin E1-4 receptors, D prostanoid receptor 1, thromboxane receptor, prostacyclin receptor, and prostaglandin F receptor). OC000459 inhibited chemotaxis (IC50 = 0.028 mu M) of human Th2 lymphocytes and cytokine production (IC50 = 0.019 mu M) by human Th2 lymphocytes. OC000459 competitively antagonized eosinophil shape change responses induced by PGD(2) in both isolated human leukocytes (pK(B) = 7.9) and human whole blood (pK(B) = 7.5) but did not inhibit responses to eotaxin, 5-oxo-eicosatetraenoic acid, or complement component C5a. OC000459 also inhibited the activation of Th2 cells and eosinophils in response to supernatants from IgE/anti-IgE-activated human mast cells. OC000459 had no significant inhibitory activity on a battery of 69 receptors and 19 enzymes including cyclooxygenase 1 (COX1) and COX2. OC000459 was found to be orally bio-available in rats and effective in inhibiting blood eosinophilia induced by 13,14-dihydro-15-keto-PGD(2) (DK-PGD(2)) in this species (ED50 = 0.04 mg/kg p.o.) and airway eosinophilia in response to an aerosol of DK-PGD(2) in guinea pigs (ED50 = 0.01 mg/kg p.o.). These data indicate that OC000459 is a potent, selective, and orally active DP2 antagonist that retains activity in human whole blood and inhibits mast cell-dependent activation of both human Th2 lymphocytes and eosinophils.