Effect of suplatast tosilate, a Th2 cytokine inhibitor, on steroid-dependent asthma: a double-blind randomised study

Background Th2 cytokines play an important part in the pathogenesis of asthma. Our aim was to study the effect of suplatast tosilate, a selective Th2 cytokine inhibitor, on asthma control and asthma exacerbations during reduction of inhaled corticosteroid dose in patients with steroid-dependent asthma. Methods 85 patients with moderate to severe asthma taking high doses (greater-or-equal, slanted1500 μg per day) of inhaled beclometasone dipropionate, were assigned suplatast tosilate (100 mg three times daily) or placebo for 8 weeks in a double-blind, randomised, parallel-group, multicentre trial. During the first 4 weeks, other medications remained unchanged (add-on phase); during the next 4 weeks, the doses of beclometasone were halved (steroid-reduction phase). Main outcome measures were pulmonary function, asthma symptoms, and use of β2-agonists. Findings Data were available from 77 patients. During the add-on phase, suplatast tosilate treatment, compared with placebo, was associated with higher forced expiratory volume in 1 s (mean difference between groups for changes from baseline at week 4, 0·20 L [95% CI 0·16–0·24], p=0·043), morning peak expiratory flow (18·6 L/min [14·1–23·1], p=0·037), and less diurnal variation in peak expiratory flow rate, asthma symptom scores (7·1 [6·6–7·6], p=0·029), and serum concentrations of eosinophil cationic protein and IgE. In the steroid-reduction phase, pulmonary function, asthma symptoms, and use of β2-agonist deteriorated significantly more in the placebo group than in the suplatast group. Interpretation Treatment with a Th2 cytokine inhibitor in steroid-dependent asthma improves pulmonary function and symptom control, and allows a decrease in dose of inhaled corticosteroid without significant side-effects. Some improvements in pharmacokinetics are, however, needed.