Inclusion Criteria:  Subject's and/or subject legal representative's written informed consent obtained prior to any study related procedure. Age: ≥18 and ≤75 years of age. Established diagnosis of permanent asthma for at least 6 months prior to screening/randomisation visit Subject on maintenance therapy treated by Foster® (CHF1535 100/6 µg pMDI) for at least 6 months prior to screening/randomisation visit Asthma Control Test (ACT) ≥ 20 at screening/randomisation visit. Subject must have a cooperative attitude and the ability to be trained to use correctly the diary and answer the Visual Analogue Scale (VAS) Subject willing and able to download the application on their personal electronic device to fill in the study e-diary. Female subject of non-childbearing potential defined as physiologically incapable of becoming pregnant or female subject + male Partner must be willing to use a highly effective birth control method from the signature of the informed consent and until Visit 4  Exclusion Criteria:  Pregnant or lactating woman History of 'at risk' asthma Recent exacerbation Non-permanent asthma Asthma requiring more than 1 inhaler for maintenance treatment and more than 1 inhaler for reliever treatment. Asthma requiring use of biologics Respiratory disorders Lower tract respiratory infection Current smoker or ex-smoker with a smoking current use/history of ≥ 10 pack-years Cardiovascular diseases subject with historical or current evidence of uncontrolled concurrent disease such as but not limited to hyperthyroidism, diabetes mellitus or other endocrine disease; haematological disease; autoimmune disorders Alcohol/drug abuse