A 52-week, Placebo-controlled Study to Evaluate the Efficacy and Safety of 2 Doses of CHF6001 DPI (Tanimilast), as add-on to Maintenance Triple Therapy in Subjects With COPD and Chronic Bronchitis (PILASTER)

Inclusion Criteria: * Adults aged ≥ 40 years with COPD and chronic bronchitis * Current or ex-smokers (history ≥ 10 pack years). * Post-bronchodilator FEV1 \<60% of the subject predicted normal value and FEV1/FVC ratio \< 0.7. * At least, one moderate or severe COPD exacerbation in previous year. * CAT score ≥ 10 * Subjects on regular maintenance triple therapy for at least 12 months prior to screening and receiving regular maintenance triple therapy for at least 3 months prior to screening visit Exclusion Criteria: * Subjects with current asthma. * Subjects with moderate or severe COPD exacerbation 4 weeks prior to study entry and randomization. * Subjects with known α-1 antitrypsin deficiency as the underlying cause of COPD. * Subjects with COPD emphysema or mixed phenotypes. * Subjects with known respiratory disorders other than COPD. * Subjects with active cancer or a history of lung cancer with full recovery less than 1 year after completing cancer therapy. * Subjects under Roflumilast treatment within 6 months before study entry. * Subjects with a diagnosis of depression, generalised anxiety disorder, suicidal ideation. * Subjects with clinically significant cardiovascular. * Subjects with a significant neurological disease. * Subjects with clinically significant laboratory abnormalities. * Subjects with moderate or severe hepatic impairment