A 52-week, Placebo- and Active- Controlled (Roflumilast, Daliresp® 500µg) Study to Evaluate the Efficacy and Safety of Two Doses of CHF6001 DPI (Tanimilast) as add-on to Maintenance Triple Therapy in Subjects With COPD and Chronic Bronchitis. (PILLAR)

Inclusion Criteria: * Adults aged ≥ 40 years, with COPD and with chronic bronchitis. * Current smokers or ex-smokers (history of ≥10 pack years). * Post-bronchodilator FEV1 \<50% of the patient predicted normal value and FEV1/FVC ratio \< 0.7. * At least, one moderate or severe COPD exacerbation in the 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 before study entry and randomisation * Subjects with known α-1 antitrypsin deficiency as the underlying cause of COPD. * Subjects with primary diagnosis of emphysema not related to COPD. * Subjects with known respiratory disorders other than COPD. * Subjects with lung volume reduction surgery. * Subjects with active cancer or a history of lung cancer. * 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 condition. * Subjects with neurological disease. * Subjects with clinically significant laboratory abnormalities. * Subjects with moderate or severe hepatic impairment.