The pharmacological profile and initial clinical evaluation of tiacrilast (Ro 22-3747): a new antiallergic agent
Tiacrilast (Ro 22-3747) is an allergic mediator release inhibitor which has demonstrated potent oral activity in two IgE-mediated animal models of immediate hypersensitivity: the rat passive cutaneous anaphylaxis test (ID50 of 0.65 mg/kg) and a model in which anaphylactic bronchospasm is induced in passively sensitized rats (ID50 of 0.022 mg/kg). In addition to oral efficacy, in the latter model Ro 22-3747 was 23-fold more potent than cromoglycate by the aerosol (nebulization) route of administration.In vitro studies have confirmed that the mechanism of action of Ro 22-3747 in thein vivo models is through allergic mediator release inhibition since Ro 22-3747 was a potent inhibitor of antigen-induced (IgE-mediated) histamine release from passively sensitized rat peritoneal cellsin vitro (IC50 values of 0.25 and 1.5 μM for Ro 22-3747 and cromoglycate, respectively), and Ro 22-3747 did not display end organ antagonism to histamine, serotonin, or the leukotrienes. Clinical evaluations of Ro 22-3747 at a 350 mg oral dose have been conducted in patients with allergic asthma and allergic rhinitis. In a limited study in allergic asthmatics, Ro 22-3747 demonstrated significant inhibitory activity relative to placebo in reducing acute airway responses to inhaled pollen extracts in patients with ragweed sensitivity (measured by changes in log PD20 FEV1 and log PD35 SGaw). The activity seen, however, was less than that observed with cromoglycate (20 mg) administered by inhalation. In a pilot evaluation in patients with allergic rhinitis, Ro 22-3747 administered at a 350 mg oral dose exhibited activity significantly greater than placebo in terms of improvements in the objective measurement of changes in nasal airflow at 2 and 3 hrs after treatment and the subjective overall global evaluation made by the patients at the end of the treatment period. The preclinical pharmacology and initial clinical efficacy of Ro 22-3747 support the continued clinical evaluation of this drug for prophylactic use in the management of asthma and other allergic disorders.
KeywordsAllergic Rhinitis Allergic Asthma Cromoglycate Nasal Airflow Passive Cutaneous Anaphylaxis
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