A Randomised, Double-blind, Placebo-controlled, Parallel-group Trial to Evaluate Efficacy and Safety of Tiotropium Inhalation Solution Delivered Via Respimat® Inhaler (2.5 mcg and 5 mcg Once Daily) Over 12 Weeks as add-on Controller Therapy on Top of Usual Care in Adolescents (12 to 17 Years Old) With Severe Persistent Asthma

The overall purpose of the trial is to evaluate efficacy and safety of tiotropium inhalation solution delivered via Respimat® inhaler (2.5 mcg and 5 mcg once daily) over 12 weeks, compared to placebo, as add-on controller therapy on top of usual care in adolescents (12 to 17 years old) with severe persistent asthma. The primary objective of the trial is to demonstrate superiority of tiotropium (5 mcg and possibly 2.5 mcg once daily in the evening) over placebo with regard to the primary pulmonary function endpoint after 12 weeks of treatment. Secondary objectives are to evaluate efficacy of tiotropium with regard to other endpoints, and to evaluate the safety of tiotropium, compared to placebo, as add-on controller therapy on top of usual care in this patient population.