Leukotrienes have been implicated in the mediation of airway obstruction induced by hyperventilation of cold dry air in asthmatic subjects. The effect of a novel inhibitor of 5-lipoxygenase activating protein, BAYx 1005, on the bronchospastic response to cold dry air hyperventilation was investigated in asthmatic patients.
After a screening cold dry air hyperventilation challenge to document cold air responsiveness, 16 asthmatic subjects (baseline forced expiratory volume in one second (FEV1) > 60% of predicted) underwent cold air challenge three hours after receiving 750 mg of BAYx 1005 or placebo using a randomised, double blind, crossover design. Leukotriene synthesis inhibition was estimated by measuring the concentration of leukotriene B4 in whole blood stimulated with calcium ionophore A21387.
Treatment with BAYx 1005 produced a 34% (95% CI 11 to 63) increase in the amount of cold air minute ventilation required for a 10% decrease in FEV1 (PD10VE) compared with placebo (mean (SE) 37.6 (1.12) 1/min compared with 28.0 (1.13) 1/min, p < 0.006). The PD20VE increased 19% (95% CI 8 to 31) after treatment with BAYx 1005 compared with placebo (57.3(1.10)1/min versus 48.1 (1.10) 1/min, p < 0.002). Treatment with BAYx 1005 produced a 15.4% decrease in ionophore-stimulated LTB4 production, while treatment with placebo produced a 7.1% increase in ex vivo LTB4 (p < 0.02).
Treatment with BAYx 1005, a novel inhibitor of leukotriene synthesis, produced a significant blunting of cold dry air responsiveness consistent with the hypothesis that leukotrienes mediate part of the bronchoconstriction induced by hyperventilation of cold dry air.