A 4-week Study to Test Different Doses of BI 1265162 in Adolescents and Adults With Cystic Fibrosis Using the Respimat® Inhaler - BALANCE - CF™1

Inclusion Criteria: * Male or female patients, 12 years of age or older at screening; * Documented diagnosis of cystic fibrosis including: * positive sweat chloride ≥ 60 mEq/L, by pilocarpine iontophoresis OR * genotype with 2 identifiable mutations consistent with cystic fibrosis accompanied by one or more clinical features with cystic fibrosis phenotype; * Patients able to perform acceptable spirometric manoeuvres according to American Thoracic Society (ATS) standards; * FEV1 ≥ 40% and ≤ 90% of predicted values at screening and predose at Visit 2; * Women of childbearing potential (WOCBP) must be willing and able to use highly effective methods of birth control per ICH M3 (R2) that result in a failure rate of less than1% per year when used consistently and correctly. A list of contraception methods meeting these criteria is provided in the patient (or patient's legal guardian) information; * Signed and dated written informed consent and assent in accordance with ICH Harmonized Guideline for Good Clinical Practice (GCP) and local legislation prior to admission in the trial. Exclusion Criteria: * Evidence of acute upper or lower respiratory tract infection within 4 weeks prior to randomization based on investigator's judgement; * Pulmonary exacerbation requiring use of i.v./oral/inhaled antibiotics or oral corticosteroids within 4 weeks prior to randomisation; * Patients with history of Acute Tubular Necrosis (ATN); * Any documented active or suspected malignancy or history of malignancy within 5 years prior to screening, except appropriately treated basal cell carcinoma of the skin or in situ carcinoma of uterine cervix; * Patients unable to inhale trial drug in an appropriate manner from the Respimat® inhaler based on investigator's judgement; * Patients who have started a new chronic medication for CF within 4 weeks of randomisation; * Patients who have previously received a lung transplant or patients who are currently on a waiting list to receive a lung transplant; * Patients with a significant history of allergy/hypersensitivity (including medication allergy) which is deemed relevant to the trial as judged by the investigator or with a known hypersensitivity to trial drug or its components. "Significance" in this context refers to any increased risk of hypersensitivity reaction to trial medication; * Any clinically significant laboratory abnormalities at screening as judged by the investigator, or any of the following: * Potassium \> upper limit of normal (ULN) in non-haemolysed blood * Abnormal renal function defined as estimated Glomerular Filtration Rate (eGFR) \< 60ml/min/1.73m² * Abnormal liver function, defined by serum level of either alanine transaminase (ALT), aspartate transaminase (AST) or total bilirubine ≥ 3 x upper limit of normal (ULN) * Clinically significant disease or medical condition other than CF or CF-related conditions that, in the opinion of the investigator, would compromise the safety of the patient or the data quality. This includes significant haematological, hepatic, renal, cardiovascular and neurologic disease. Patients with diabetes may participate if their disease is under good control prior to screening; * Patients not expected to comply with the protocol requirements or not expected to complete the trial as scheduled; * Previous randomisation in this trial; * Currently enrolled in another investigational device or drug trial, or less than 30 days or six half-lives (whichever is greater) since ending another investigational device or drug trial(s), or receiving other investigational treatment(s); * Chronic alcohol or drug abuse or any condition that, in the investigator's opinion, makes them an unreliable trial patient or unlikely to complete the trial; * Women who are pregnant, nursing, or who plan to become pregnant while in the trial.