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Chemoattractant receptor homologous molecule expressed on Th2 lymphocytes, (CRTH2), is a receptor for prostaglandin D2 (PGD2) and in humans is thought to play a role in Th2‐dependent allergic inflammation. Little is known of the functional significance of CRTH2 in disease.

Clinical Studies

Clinical StudiesAbstract
Prostaglandin metabolism in human hair follicle. Prostaglandins regulate a wide number of physiological functions. Recently PGF(2alpha) analogue such as latanoprost was shown to have a real impact on hair regrowth. The aim of this study was to investigate and describe the expression profile in human hair follicle of prostaglandin metabolism key enzymes, i.e. carbonyl reductase-1 (CBR1), microsomal prostaglandin E synthase-1 (mPGES-1) and microsomal prostaglandin E synthase-2 (mPGES-2), cytosolic prostaglandin E synthase (cPGES), the aldoketoreductase AKR1C1 and the prostaglandin F synthase AKR1C3. Quantitative RT-PCR on plucked hair follicles revealed some sex-related differences, mPGES-2 and AKR1C3 expression levels being higher in women. Cell and hair follicle compartment specificity was investigated using Western blot, PGE(2) and PGF(2alpha) ELISA assays and immunohistochemistry. Most of the hair cell types were endowed with prostaglandin metabolism machinery and were thus able to produce PGE(2) and/or PGF(2alpha). The epithelial part of the hair bulb was identified by immunohistology and EIA assays as the main source of prostaglandin synthesis and interconversion. All these observations support the concept that prostaglandins might be involved in hair growth and differentiation control.
The CRTH2 antagonist OC000459 reduces nasal and ocular symptoms in allergic subjects exposed to grass pollen, a randomised, placebo-controlled, double-blind trial. BACKGROUND: CRTH2 mediates activation of Th2 cells, eosinophils and basophils in response to prostaglandin D(2) . The CRTH2 antagonist OC000459 has previously been demonstrated to reduce airway inflammation and improve lung function in moderate persistent asthma. The objective of the present study was to determine the involvement of CRTH2 in promoting nasal and ocular symptoms in allergic subjects exposed to grass pollen. METHODS: A single centre, randomised, double-blind, placebo-controlled, two-way crossover study was conducted in 35 male subjects allergic to grass pollen comparing OC000459 200 mg bid with placebo for 8 days. Subjects were exposed to grass pollen (≥1400 grains/m(3) ) for 6 h on the 2nd and 8th days of treatment and assessed for nasal symptoms, ocular symptoms, other symptoms, nasal secretion weight and rhinomanometry over the 6-h period. After a washout period of 3 weeks, subjects were switched to the alternative treatment for a further 8 days. The trial was registered on the clinical database (Identifier NCT01448902). RESULTS: During the first treatment period, treatment with OC000459 significantly reduced both nasal and ocular symptoms in allergic subjects compared with placebo after challenge with grass pollen. A significant effect was observed on the 2nd day of dosing which was increased on the 8th day of dosing. The therapeutic effects of OC000459 persisted into the second treatment period despite a 3-week washout phase. The safety profile of OC000459 was similar to that of placebo. CONCLUSION: Treatment with OC000459 was well tolerated and led to a significant and persistent reduction in the symptoms of rhinoconjunctivitis.
Inhibition of the asthmatic allergen challenge response by the CRTH2 antagonist OC000459.. CRTH2 is a G protein-coupled receptor expressed by Th2 lymphocytes and eosinophils that mediates prostaglandin D2 (PGD2) driven chemotaxis. We studied the efficacy of the oral CRTH2 antagonist OC000459 in steroid naive asthmatic patients.A randomised, double-blind, placebo-controlled, two-way crossover study of 16 days treatment with OC000459 (200 mg twice·day(-1)) on the late (LAR) and early (EAR) asthmatic responses to bronchial allergen challenge was conducted, with 16 subjects completing the study.There was a 25.4% reduction in the LAR area under the curve (AUC) for change in FEV1 with OC000459 compared to placebo (95% CI 5.1-45.6, p=0.018), but no effect on the EAR. Sputum eosinophil counts at 1 day post allergen challenge were lower after OC000459 treatment (p=0.002). PGD2 induced blood eosinophil shape change ex-vivo was assessed at day 7 (n=7). The AUC of eosinophil shift for OC000459 was lower than placebo; the mean difference was -33.6% (95% CI -66.8 to -0.4, p=0.048).OC000459 treatment inhibited the LAR and the post allergen increase in sputum eosinophils. This CRTH2 antagonist appears to inhibit allergic inflammation in asthma.
PGH1, the precursor for the anti-inflammatory prostaglandins of the 1-series, is a potent activator of the pro-inflammatory receptor CRTH2/DP2. Prostaglandin H(1) (PGH(1)) is the cyclo-oxygenase metabolite of dihomo-γ-linolenic acid (DGLA) and the precursor for the 1-series of prostaglandins which are often viewed as "anti-inflammatory". Herein we present evidence that PGH(1) is a potent activator of the pro-inflammatory PGD(2) receptor CRTH2, an attractive therapeutic target to treat allergic diseases such as asthma and atopic dermatitis. Non-invasive, real time dynamic mass redistribution analysis of living human CRTH2 transfectants and Ca(2+) flux studies reveal that PGH(1) activates CRTH2 as PGH(2), PGD(2) or PGD(1) do. The PGH(1) precursor DGLA and the other PGH(1) metabolites did not display such effect. PGH(1) specifically internalizes CRTH2 in stable CRTH2 transfectants as assessed by antibody feeding assays. Physiological relevance of CRTH2 ligation by PGH(1) is demonstrated in several primary human hematopoietic lineages, which endogenously express CRTH2: PGH(1) mediates migration of and Ca(2+) flux in Th2 lymphocytes, shape change of eosinophils, and their adhesion to human pulmonary microvascular endothelial cells under physiological flow conditions. All these effects are abrogated in the presence of the CRTH2 specific antagonist TM30089. Together, our results identify PGH(1) as an important lipid intermediate and novel CRTH2 agonist which may trigger CRTH2 activation in vivo in the absence of functional prostaglandin D synthase.
Optimization of phenylacetic acid derivatives for balanced CRTH2 and DP dual antagonists. Our first generation CRTH2 and DP dual antagonists, represented by AMG 009, are more potent toward the CRTH2 receptor than to the DP receptor. Here we report our efforts in the discovery of CRTH2 and DP dual antagonists with more balanced potencies to both receptors, such as compound 15.
Discovery of potent, selective, and orally bioavailable alkynylphenoxyacetic acid CRTH2 (DP2) receptor antagonists for the treatment of allergic inflammatory diseases.. New phenoxyacetic acid antagonists of CRTH2 are described. Following the discovery of a hit compound by a focused screening, high protein binding was identified as its main weakness. Optimization aimed at reducing serum protein binding led to the identification of several compounds that showed not only excellent affinities for the receptor (41 compounds with K(i) < 10 nM) but also excellent potencies in a human whole blood assay (IC(50) < 100 nM; PGD2-induced eosinophil shape change). Additional optimization of the PK characteristics led to the identification of several compounds suitable for in vivo testing. Of these, 19k and 19s were tested in two different pharmacological models (acute FITC-mediated contact hypersensitivity and ovalbumin-induced eosinophilia models) and found to be active after oral dosing (10 and 30 mg/kg).
A randomized, double-blind, placebo-controlled study of the CRTH2 antagonist OC000459 in moderate persistent asthma.. BACKGROUND: CRTH2 is a G-protein-coupled receptor that mediates the activation of Th2 lymphocytes, eosinophils and basophils in response to prostaglandin D(2) and may be involved in the pathogenesis of airway inflammation and dysfunction in asthma. OBJECTIVE: To evaluate the effects of a potent and selective CRTH2 antagonist, OC000459, on the lung function, symptoms and eosinophilic airway inflammation in a double-blind, parallel group trial in steroid-free subjects with moderate persistent asthma. METHODS: Adult subjects were randomized to oral OC000459 200 mg twice daily (N=65) or a placebo (N=67) for 28 days. The primary end-point was the change from baseline in pre-bronchodilator forced expiratory volume in 1 s (FEV(1) ); eosinophilic airway inflammation was assessed by induced sputum differential eosinophil count. The trial was registered on the database (Identifier NCT01057927). RESULTS: Data were analysed for both the Full Analysis (FA) population and the Per Protocol (PP) population (55 treated with OC000459 and 52 with placebo), which excluded non-compliant subjects. In the FA population, the mean change in FEV(1) was 7.1% on OC000459 compared with 4.3% on placebo (not significant); in the PP population, the mean changes were 9.2% and 1.8%, respectively (P=0.037). Improvement in quality of life was apparent in both FA and PP populations [difference from the placebo in AQLQ(S) total score of 0.29, P=0.0113 and 0.37, P=0.0022, respectively]. OC000459 also improved the night-time symptom scores (mean reduction of 0.36 vs. 0.11, P=0.008, FA population; 0.37 vs. 0.12, P=0.022, PP population). The geometric mean sputum eosinophil count reduced from 2.1% to 0.7% (P=0.03) after OC000459, but this effect was not significant when compared with the change on placebo (P=0.37). Adverse events on OC000459 were comparable to those on placebo; respiratory infections were notably less common during OC000459 than the placebo treatment. CONCLUSION AND CLINICAL RELEVANCE: This study provides the first clinical evidence that CRTH2 receptors contribute to airflow limitation, symptoms and eosinophilic airway inflammation in asthma. OC000459 shows promise as a novel oral treatment for asthma and related disorders.
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. 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 D₂ (PGD₂). (5-Fluoro-2-methyl-3-quinolin-2-ylmethylindo-1-yl)-acetic acid (OC000459) is an indole-acetic acid derivative that potently displaces [³H]PGD₂ from human recombinant DP₂ (K(i) = 0.013 μM), rat recombinant DP₂ (K(i) = 0.003 μM), and human native DP₂ (Th2 cell membranes; K(i) = 0.004 μM) 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 μM) of human Th2 lymphocytes and cytokine production (IC₅₀ = 0.019 μM) by human Th2 lymphocytes. OC000459 competitively antagonized eosinophil shape change responses induced by PGD₂ 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 bioavailable in rats and effective in inhibiting blood eosinophilia induced by 13,14-dihydro-15-keto-PGD₂ (DK-PGD₂) in this species (ED₅₀ = 0.04 mg/kg p.o.) and airway eosinophilia in response to an aerosol of DK-PGD₂ 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.


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