1. Prostaglandin D2: Therapeutic Indications World Allergy Organisation Cancun 2011 Andy Wardlaw

2. Disclosures Research grants from Glaxo Smith Kline (GSK), AstraZeneca and Pfizer Honorariums for advisory boards from GSK and Cephalon

3. Airway inflammation leads to several patho- physiological outcomes Environmental Trigger AllergenInfectionSmoking BRONCHIAL INFLAMMATION EosNeuts Airway Damage (fixed airflow obstruction Bronchiectasis) Variable Airflow Obstruction & AHR (Asthma Like) Uncontrolled Falls in FEV 1 (Severe Exacerbations) Increased cough reflex (cough)

4. The A to E of Airway disease Pavord ID and Wardlaw AJ Clin Exp Allergy 2010;40:62-67 A Airway hyperresponsiveness –Rapid variations in airflow obstruction B Bronchitis –Eosinophilic:neutrophilic:both C Cough D Damage –Bronchiectasis –fixed airflow obstruction –emphysema E Extrapulmonary factors –Psychological and lifestyle issues including adherence –Obesity and obstructive sleep apnoea –Dysfunctional breathing: –Treatment side effects and co-morbidities

5. Eosinophilic Airway Inflammation and Variable Airflow Obstruction (AHR) are Largely Independent Methacholine PC 20 (mg/ml) Sputum Eosinophil Count (%) Eosinophilic Inflammation Severe Exacerbations Smooth Muscle Dysfunction Uncontrolled, Treatment Unresponsive Falls in FEV 1 Variable Airflow Obstruction/AHR Asthma Symptoms

6. PGD 2 Prostaglandin is produced (outside the brain), mainly by mast cells by the combined action of cyclooxygenase enzymes and prostaglandin D 2 synthase 50ng per 10 6 mast cells Not produced in significant amounts by basophils Released as part of the early but not the late response to allergen challenge

7. Roy Pettipher et al Nature Reviews Drug Discovery 6, 313-325 (April 2007) Synthetic pathway for PGD 2

8. PGD 2 Some evidence synthesis is increased in clinical asthma although concentrations in sputum and BAL are variable with inconsistent difference between asthma and healthy subjects. Inhalation causes bronchoconstriction and vasodilation. Injection into the skin causes recruitment of neutrophils and to a lesser extent eosinophils.

9. Mediator concentrations ng/ml sputum *p<0.05, ANOVA Brightling et al Am J Respir Crit Care Med 2000; 162: 878-882 No increase in PGD 2 in sputum from patients with asthma

10. Antagonism and over-expression of PGD 2 PGD 2 is primarily synthesised by COX 1 and PGE 2 by COX 2. Non-specific COX inhibitors will inhibit both so cancelling each other out –Dahem K et al CEA 2011 PGD 2 synthase transgenic mouse had increased production of PGD2 and increased Th2 inflammation in the mouse model of asthma –Fujitana et al J Immunol 2002

11. PGD 2 Receptors Three receptors: –DP 1 receptor expressed on airway smooth muscle, vascular tissue, dendritic cells and T cells. –DP 2 ; Chemoattractant receptor homologous molecule expressed on Th2 cells (CRTh2). Expressed on Th2 cells (also Th1 in mice), basophils and eosinophils –TP: Thromboxane A 2 receptor expressed on airway smooth muscle PGD 2 metabolites bind to CRTh2 but not DP 1

12. DP 1 receptor Primary function appears to be vasodilation but may also mediate bronchodilation In vitro down-regulates Th1 and dendritic cell function possibly leading to increased Th2 responses. DP 1 gene deleted mouse had reduced inflammation and AHR in the mouse model of asthma as did mice and sheep treated with a DP1 antagonist. (Shichijo et al CEA 2009) However DP 1 agonist was anti-inflammatory in allergic responses in skin in mouse and in the mouse model of asthma by modulating dendritic cell and Treg function. (Hammad et al J Exp Med 2007)

13. Clinical efficacy of a DP 1 antagonist laropiprant ( Phillip G et al JACI 2009:124:942-8) Rhinitis: –767 patients with seasonal allergic rhinitis treated with laropiprant for two weeks: no difference in nasal symptom score from placebo Asthma: –100 patients with asthma randomised to laropiprant or placebo for three weeks: no difference in asthma symptoms or FEV1

14. TP receptor Receptor for a stable metabolite of PGD 2 (9alpha11betaPGF2), as well as thromboxane A 2 Mediates bronchoconstrictor activities of PGD 2 A selective antagonist of the TP receptor, GR32191 blocked PGD 2 induced bronchoconstriction and had a modest effect on the early response to allergen challenge, but no effect on exercise induced asthma or clinical disease after three weeks of treatment

15. CRTh2 receptor Identified in 2001 as a receptor for PGD 2 expressed on eosinophils, Th2 cells (hence its name) and basophils where it mediates activation and migration –Hirai et al J Exp Med 2001:193:255 Gene deletion showed increased eosinophil accumulation in the mouse model of asthma with short term exposure but decreased eosinophil infiltration with chronic exposure –Chevalier et al J Immunol: 2005:175:2056. Kagawa et al Int Arch All Imm 2011:155suppl Gene deletion inhibits allergic skin inflammation in mice –He et al JACI:2010:126:784. Satoh et al J Immunol 2006:177:2621

16. CRTh2 expression on T cells in asthma Mutalithas K et al Clin Exp Immunol 2010:161:34-40

17. CRTh2 is preferentially expressed on Th2 cells Asthma Healthy

18. CCR3, CCR4, CRTh2 and CCR8 are preferentially expressed on Th2 cells but only a minority of Th2 cells express these receptors IL-4 IFN 

19. % of BAL T cells expressing CRTH2

20. PGD 2 concentrations in BAL

21. Antagonists of CRTh2 in clinical development It has been relatively easy to make potent and effective CRTh2 antagonists and there are several in early phase clinical trials which appear safe and well tolerated Some are based on NSAID’s as indomethacin was found to be a selective antagonist and some based on the structure of angiotensin receptor antagonists. Ramatroban used for allergic rhinitis in Japan is a potent TP antagonist with moderate antagonism for CRTh2, but there is little literature on clinical efficacy

22. Trial of a CRTh2 inhibitor (OC000459) in moderate steroid naïve asthma Barnes et al CEA 2012 epub Double blind placebo controlled with parallel group design carried out in Russia Moderate asthma but not taking inhaled corticosteroids One month treatment Change in FEV1 was primary outcome Modest improvement which was significant in the per protocol, but not the full analysis population

23. Study design

24. Placebo (n=50) vs. OC000459 (n=55) OC000459 Clinic FEV 1 9.2% greater than baseline at end of randomised treatment period; Treatment difference OC000459-Placebo = 7.4%; p-value = 0.037 OC000459 Clinic FEV 1 214mL greater than baseline at end of randomised treatment period; Treatment difference OC000459-Placebo = 184mL OC000459 Phase II Asthma Study Effect on FEV 1 (Per Protocol Population ) Clinically relevant improvement in FEV 1 % Change in FEV 1 vs. Baseline Change in FEV 1 (ml) vs. Baseline Start double blind treatment End double blind treatment End Placebo washout Start double blind treatment End double blind treatment End Placebo washout

25. Effect of OC000459 on sputum eosinophilia in 28 day asthma study

26. Conclusions PGD2 is a major mast cell derived mediator with several activities relevant to allergic disease Three receptors, DP 1 (vasodilation and immune modulation), TP (bronchoconstriction) and CRTh2 (immune modulation, cell recruitment) Mouse models for a role for DP 1 and CRTh2 are conflicting and not particularly compelling for an important role of DP 1 and CRTh2 in asthma Human studies of antagonists of TP and DP 1 have been negative Single study in humans of CRTh2 antagonist in moderate asthma demonstrated modest effect at best, but several antagonists in early phase development

27. Acknowledgements Das MutalithasC Guillen Caroline Day C Brightling ID Pavord F Symon Asthma UK GSK