Safety and Efficacy Comparison Between CHF5993 100/6 12.5µg pMDI to Seretide Evohaler 125/25µg pMDI in Adolescent Subjects With Asthma

Inclusion Criteria: * Subject's written informed consent obtained prior to any study related procedure; * Male and female adolescent aged ≥ 12 and \<18 years; * Subject participating in the Pharmacokinetic(s) (PK) part of the study, body weight should be ≥ 30kg * A documented history of asthma for at least 6 months * Subjects in treatment with double therapy with medium doses of inhaled corticosteroids (ICS) in fixed or free combination with a long-acting β2-agonist (LABA) ( \> 500-1000 μg daily dose Beclomethasone Dipropionate non-extrafine or estimated clinically comparable dose plus formoterol 24 µg/day or salmeterol 100 µg/day or vilanterol 25 µg/day) at a stable dose for at least 4 weeks prior to screening; * Subjects must have a cooperative attitude and the ability to be trained to use correctly the pMDI inhalers and e-Diary, to be able to read/write, to be able to perform the required outcomes measurements (e.g., technically acceptable spirometry, e-Diary completion) and the ability to understand the risks involved. * Subjects with a pre-Bronchodilator (BD) Forced Expiratory Volume in the first second (FEV1) ≤90% and ≥60% of their predicted normal value, after appropriate washout from BDs, at the Screening and Randomization Visits * Subjects with a positive response to a reversibility test at screening, defined as FEV1 ≥12% and ≥200 mL over baseline, 10 to 15 minutes (min) after inhaling 200-400 µg of salbutamol pMDI. * Subjects with uncontrolled asthma evidenced by an ACQ-7 total score ≥1.5 at screening; * A documented history of one or more asthma exacerbations requiring treatment with systemic corticosteroids (SCS) or emergency department visit or in-patient hospitalization in the previous 12 months; Exclusion Criteria: * History of "at risk" asthma: history of near fatal asthma or of a past hospitalization for asthma in an intensive care unit which, in the judgement of the Investigator, may place the subject at undue risk; * Recent exacerbation or respiratory tract infection: hospitalization, emergency room admission or use of SCS for an asthma exacerbation or a documented diagnosis of lower respiratory tract infection that required antibiotics or an unresolved respiratory tract infection within 4 weeks prior to Screening Visit (V1) or during the run-in period; * Respiratory disorders other than asthma: this can include but is not limited to: α1-antitrypsin deficiency, active tuberculosis, bronchiectasis, cystic fibrosis, sarcoidosis, pulmonary hypertension and interstitial lung disease; * Current smokers (including e-cigarettes, vaping and hookah), or ex-smokers with a smoking history of ≥5 pack-years (pack-years = the number of cigarette packs per day times the number of years), or current use of inhaled or oral cannabis products. Ex-smokers must have stopped smoking ≥1 year (≥6 months for e-cigarettes); * Other severe acute or chronic medical (such as but not limited to thyrotoxicosis, diabetes mellitus, and untreated hypokalemia) or malignancy or psychiatric condition or laboratory abnormality that may increase the risk associated with study participation or study treatment administration or may interfere with the interpretation of study results and, in the judgment of the Investigator, would make the subject inappropriate for entry into this study; * Any change in dose, schedule or formulation of the combination ICS plus LABA in the 4 weeks prior to Screening Visit (V1) * Subjects using SCS medication in the 4 weeks or slow-release corticosteroids in the 12 weeks, prior to screening * Only for subjects included in the subset for PK assessment: Veins unsuitable for repeated venipuncture; Blood donation or blood loss (\>450 mL) in the 4 weeks before randomization.