The inhibitory effect of anti-allergic agent suplatast tosilate (IPD-1151T) on methacholine- and allergen-induced bronchoconstriction in sensitized mice. asakazu@med.showa-u.dc.jp

Recent research and developmental strategy of anti-asthma drugs

Extensive research over the past decade has provided information about the pharmacotherapy of bronchial asthma (BA). Anti-asthma drugs are classified into two categories: relievers (for the relief of asthma attack symptoms) and controllers (for the prevention of asthma symptoms). This paper aims to review the recent advancements of anti-asthma drugs that are controller medicines. The controllers mainly act on immune and inflammatory responses in BA development. 1) Immunomodulators. Drugs that act on the immune response are classified into two categories: immunosuppressors and immunomodulators, including immunopotentiators. The immunomodulation of the Th1 and Th2 imbalance is the first strategy of the controller because allergic BA is thought to be caused by Th2-polarized immunity. Suplatast is a novel immunomodulator that can adjust the imbalance in the Th1/Th2 immune response and shows clear clinical efficacy against BA. The immunomodulator approach has shifted from a more theoretical and conceptual model to one supported by evidence of clinical efficacy.2) Anti-inflammatory agents. Corticosteroids,mast cell stabilizers and autacoid inhibitors are anti-inflammatory agents for BA. The clinical superiority of the combined therapy of inhaled corticosteroids and long-acting beta2 agonists is evident. This combined therapy shows a potent synergic anti-inflammatory effect compared to the effect by corticosteroids alone. Currently, the anti-inflammatory agents for BA under development are drugs affecting lipid mediators. The prostaglandin (PG) D2 antagonist, PGE2, EP3 agonist and PGI2 agonist are being considered in addition to well-established leukotriene and thromboxane A2 inhibitors. New development strategies and therapeutics for controllers are described in this review.

Suplatast tosilate inhibits eosinophil production and recruitment into the skin in murine contact sensitivity

Antiallergic drugs and antihistamines have been widely used for controlling mucosal allergic diseases in which eosinophilia is prominent. Although H1-receptor antagonists are effective for treating histamine-induced wheal and itch in urticaria, the effects of antihistamines and antiallergic agents on other eosinophilic skin diseases remain to be determined. We investigated the effects of oral administration of antiallergic drugs and antihistamines, such as suplatast tosilate, emedastine difumarate, and azelastine hydrochloride, on a novel murine model of eosinophilia in contact sensitivity to picryl chloride. Among the drugs tested, only suplatast tosilate remarkably inhibited blood and tissue eosinophilia and the ear swelling responses. The inhibitory effects on eosinophilia seemed to be mediated by the suppression of IL-5 production in spleen cells during eosinophil development, while the effects on the ear swelling response seemed to be mediated by suppression of IL-4 production in immune lymph node cells in the efferent phase. Suplatast tosilate may effectively treat eosinophilic skin diseases in which Th2-cell-derived cytokines are predominant.