A Study Comparing the Efficacy and Safety of CHF 1535 (BDP +FF) Inhalation Powder, Administered Via the NEXT Inhaler, Versus CHF 1535 (BDP +FF), Administered Via a pMDI, in Moderate to Severe Asthma

Inclusion Criteria: * Written informed consent * Outpatients of both sexes, aged \> 12 years * Moderate to severe symptomatic asthma * Forced expiratory volume in the first second (FEV1) \> 40% and \< 80% of the predicted normal values * Reversibility test * "Partly controlled" asthma (GINA revised 2006) * Patients free of long-acting beta2-agonists (LABAs) treatment * Under inhaled corticosteroids (ICS) treatment * A minimum inspiratory flow ≥ 40 L/min 10. * Non-smokers or ex smokers * Asthma Control Questionnaire ACQ score ≥ 1.5 Exclusion Criteria: * Pregnant or nursing (lactating) women * Women of child-bearing potential, UNLESS they are menopausal or have acceptable methods of contraception * Significant seasonal variation in asthma or asthma occurring only during episodic exposure to an allergen or a chemical sensitizer * History of near fatal asthma * Occurrence of asthma exacerbations or respiratory tract infections in the 6 weeks preceding the screening visit * Diagnosis COPD * History of cystic fibrosis, bronchiectasis or alpha-1 antitrypsin deficiency * Diagnosis of restrictive lung disease * Patients treated with oral or parenteral corticosteroids in the previous 2 months (3 months for parenteral depot corticosteroids) * Intolerance or contra-indication to treatment with beta2-agonists and/or inhaled corticosteroids * Allergy to any component of the study treatments * Any change in the dose, schedule, formulation or product of an inhaled corticosteroid in the 4 weeks prior to screening visit * Significant medical history of and/or treatments for cardiac, renal, neurological, hepatic, endocrine diseases, or any laboratory abnormality ; * Patients with abnormal QTc