An evaluation of zafirlukast in the treatment of asthma with exploratory subset analyses

Abstract

Background: Consensus asthma guidelines recommend antileukotriene agents as alternative therapy to existing anti-inflammatory medications; however, the full therapeutic potential of these medications has not yet been determined. Objective: The purpose of this study was to assess the efficacy and safety of the oral leukotriene receptor antagonist zafirlukast (20 mg twice daily) in subgroups of patients who have asthma with the use of integrated data from four 13-week trials. Methods: The trials had comparable designs, entry criteria, and clinical assessments. Patient subgroups were characterized by demographic and baseline asthma characteristics. Analysis of covariance models were tested for overall treatment effect and for interactions between treatment and subgroup characteristics. Results: Patients with mild-to-moderate asthma (12 to 76 years old) who were treated with albuterol alone were randomized (n Z = 879; n P = 605) and included in subset analyses. Significant overall treatment effects, favoring zafirlukast, were noted for measures of daytime and nighttime symptoms, β 2 -agonist use, and pulmonary function ( P < .05). A significant, quantitative, treatment-by-age interaction was noted for β 2 -agonist use ( P < .03), suggesting greater reductions in rescue medication use with increasing patient age. Compared with placebo, similar size and/or direction of response was noted with zafirlukast in the various subgroups, indicating a benefit with zafirlukast regardless of subgroup. Significant treatment-by-strata interactions ( P < .05), favoring zafirlukast, were noted for various outcome measures in subgroups with the greatest amount of baseline β 2 -agonist use (>8 puffs/day) and with greater baseline peak flow variability (≥20%) and baseline airflow obstruction (FEV 1 /forced vital capacity ratio, <0.70). The overall treatment failure rate was significantly lower in the zafirlukast group compared with the placebo group ( P < .003). No associations were observed between any adverse events and subgroups defined by demographic characteristics. Conclusions: Exploratory subset analyses showed that zafirlukast is similarly efficacious in patients with asthma who have differing demographic characteristics and degrees of subjective symptoms. Additionally, zafirlukast appears to be incrementally beneficial in patients with more moderate disease, defined by a greater requirement for as-needed rescue medication and more abnormal pulmonary function at baseline. Over 13 weeks, zafirlukast was well tolerated and demonstrated a safety profile clinically indistinguishable from placebo. (J Allergy Clin Immunol 1999;103:246-54.)