AIR2 Extension Study to Demonstrate Longer-term (> 1 Year) Durability of Effectiveness

The objective of this study is to evaluate durability of effectiveness (beyond one year) of the Alair System in patients with severe persistent asthma. The study will consist of Alair-group subjects who are currently in the follow-up phase (out to 5 years) of the AIR2 Trial (Protocol #04-02, clinicaltrials.gov number NCT00231114). Durability of the treatment effect will be evaluated by comparing the proportion of subjects who experience severe exacerbations during the first year after Alair treatment with the proportion of subjects who experience severe exacerbations during subsequent 12 month periods out to 5 years. All Alair group subjects in the AIR2 Trial are being followed out to 5 years as per the AIR2 Trial protocol. The data that are to be used to determine durability of effectiveness as described in the present protocol (Protocol #10-01) are being collected under the existing AIR2 Trial protocol (Protocol # 04-02). Study Hypothesis: An empirical demonstration of the durability of the treatment effect will be used to show that the proportion of subjects experiencing severe exacerbations for the first year compared with the proportions of subjects experiencing severe exacerbations in subsequent years do not get substantially worse. The primary statistical objective is to demonstrate that the proportion of subjects who experience severe exacerbations in the subsequent 12-month follow-up (for Year 2, Year 3, Year 4 and Year 5 [in 12-month periods]) is not statistically worse when compared with the proportion of first 12-months, which begins 6-weeks after the last Alair treatment. This objective will be met if the upper 95% confidence limit of the difference in proportions (i.e., the subsequent 12-month proportion minus the first 12-month proportion) is less than 20%.