The study is aimed to assess the dose proportional total systemic exposure (when the administration is without the activated charcoal) to B17MP (active metabolite of BDP) and its lung bioavailability (when the administration is with the activated charcoal) after single inhalation of CHF 1535 NEXThaler DPI at two dose strengths.

At the same time, the study will assess if the lung deposition and the total systemic exposure to Formoterol is affected by increasing doses of BDP.

Inclusion Criteria:

• Diagnosis of asthma as defined by Global Initiative for Asthma (GINA) 2011
• Asthmatic patients already treated with low daily doses of Inhaled Corticosteroids (ICS) (eg budesonide or equivalent lower than 400 mcg/day) or low dose of ICS/Long Acting Beta2 Agonists (LABA) fixed combinations.
• Patients with Forced Expiratory Volume in 1 sec (FEV1) >= 70 % of predicted values
• Non or ex-smokers
• Body Mass Index (BMI) >= 18.5 and <= 32 kg/m2

Exclusion Criteria:

• Pregnant or lactating women unless using acceptable methods of contraception
• Diagnosis of Chronic Obstructive Pulmonary Disease (COPD)
• History of near fatal asthma
• Patients with abnormal QTcF at screening Visit
• Hospitalization due to asthma exacerbation within 4 weeks prior to the screening visit or during the run-in period.
• Lower respiratory tract infection within 4 weeks prior to the screening visit or during the run-in period.
• History of drug addiction or excessive use of alcohol ;
• Diagnosis of restrictive lung disease.
• Patients treated with oral or parenteral corticosteroids in the previous 2 months before the screening visit (3 months for parenteral depot corticosteroids)
• Significant medical history or any laboratory abnormality indicative of a significant underlying condition