Mast cell inhibitor R112 is well tolerated and affects prostaglandin D-2 but not other mediators, symptoms, or nasal volumes in a nasal challenge model of allergic rhinitis
ABSTRACT Understanding of the role played by mast cells in allergic rhinitis (AR) has led to the development of novel therapies. The aim of this study was to determine the safety and tolerability of R112, an inhibitor of the tyrosine kinase Syk, in an allergen challenge model of AR. We also examined the effects of R112 on symptoms, mediator release, and nasal airway volumes. This double-blinded, randomized, placebo-controlled, crossover trial enrolled 20 out-of-season volunteers with AR. One intranasal dose of R112 or vehicle was administered and followed by an allergen challenge. In addition to safety monitoring, symptoms; changes in histamine, tryptase, and prostaglandin D2 (PGD2) content of nasal secretions; and acoustic rhinometry were determined over a 15-minute period. R112 was well tolerated. Adverse events were similar between treatments. Five minutes after allergen instillation, PGD2 was decreased when subjects received R112 compared with vehicle (93.4 +/- 23.0 pg/mL versus 171.6 +/- 23.0 pg/mL; p = 0.03), and this correlated with rhinorrhea (p = 0.05). However, at 10 minutes, changes in PGD2, tryptase, and histamine were not significant (46.8 +/- 9.2 pg/mL versus 68.6 +/- 9.2 pg/mL, p = 0.1; 9.5 +/- 2.7 ng/mL versus 16.6 +/- 2.9 ng/mL, p = 0.09; and 1.5 +/- 1.6 ng/mL versus 3.5 +/- 1.6 ng/mL, p = 0.4). No differences were found in symptoms or in acoustic rhinometry between treatment groups. Single-dose R112 appears safe and significantly reduces PGD2 but not histamine or tryptase release in response to allergen challenge in subjects with AR.
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ABSTRACT: Mast cells are central mediators of allergic diseases. Their involvement in allergic reactions is largely dependent on activation through the specific receptor for IgE (Fc epsilon RI). Cross-linking of Fc epsilon RI on mast cells initiates a cascade of signaling events that eventually results in degranulation, cytokine/chemokine production, and leukotriene release, contributing to allergic symptomology. Because of the importance of IgE in allergy, much focus has been placed on deciphering the signaling events that take place downstream of Fc epsilon RI. Studies have identified spleen tyrosine kinase as a key proximal regulator of Fc epsilon RI-mediated signaling. In this review, we discuss the multiple pathways that diverge from spleen tyrosine kinase with emphasis on the role of adapter molecules to orchestrate these signaling events. Understanding the molecular mechanisms underlying mast cell activation ideally will provide insights into the development of novel therapeutics to control allergic disease.Journal of Allergy and Clinical Immunology 04/2007; 119(3):544-52; quiz 553-4. DOI:10.1016/j.jaci.2007.01.017 · 11.25 Impact Factor
- Journal of Allergy and Clinical Immunology 04/2007; 119(3):555-7. DOI:10.1016/j.jaci.2007.01.014 · 11.25 Impact Factor
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ABSTRACT: Mast cells have long been recognized for their role in the genesis of allergic inflammation; and more recently for their participation in innate and acquired immune responses. Mast cells reside within tissues including the skin and mucosal membranes, which interface with the external environment; as well as being found within vascularized tissues next to nerves, blood vessels and glandular structures. Mast cells have the capability of reacting both within minutes and over hours to specific stimuli, with local and systemic effects. Mast cells express the high affinity IgE receptor (FcepsilonRI) and upon aggregation of FcepsilonRI by allergen-specific IgE, mast cells release and generate biologically active preformed and newly synthesized mediators which are involved in many aspects of allergic inflammation. While mast cells have been well documented to be essential for acute allergic reactions, more recently the importance of mast cells in reacting through pattern recognition receptors in innate immune responses has become recognized. Moreover, as our molecular understanding of the mast cell has evolved, novel targets for modulation have been identified with promising therapeutic potential.Clinical & Experimental Allergy 02/2008; 38(1):4-18. DOI:10.1111/j.1365-2222.2007.02886.x · 4.32 Impact Factor