 The objective of the REACT trial is to investigate the effect of roflumilast 500 μg tablets once daily versus placebo on exacerbation rate and pulmonary function in COPD patients who are concomitantly treated with a fixed combination of long-acting β2-agonists LABA and inhaled glucocorticosteroids ICS. In addition, data on safety and tolerability of roflumilast will be obtained. An additional objective is to further characterize the population pharmacokinetic profile of roflumilast and roflumilast N oxide and to further characterize their pharmacokineticspharmacodynamics PKPD relationship in terms of efficacy and relevant safety aspects. 