This is a dose-finding study for the investigational product Lancovutide (Moli1901) in the exploratory phase IIb to establish minimum effective dose, optimal dose, and maximum safe dose. Additionally, the tolerability of Moli1901 shall be investigated.

Study Moli1901-010B is a multi center, parallel group, placebo controlled, double-blind efficacy and safety evaluation of three different dosage schedules of aerosolized Moli1901 in adolescents (12 years of age or older), and adults. Study will start with a screening period (visit 1) followed by an 8 weeks double blind comparative treatment period (visit 2-7). Thereafter, subjects will be observed for additional 4 weeks without treatment (follow-up period and visit 8). Spirometry, pulse oximetry and other safety measurements will be performed up to 120 min after study medication inhalation. The study will be conducted in 30 sites in 9 European countries.

Inclusion Criteria:

• Body mass index
• Confirmed diagnosis of cystic fibrosis
• FEV1 between 50% and 85% of predicted
• Oxygen saturation level measured by pulse oximetry (SpO2) >90 % on room air

Exclusion Criteria:

• Bronchial hyperresponsiveness
• Unstable lung function
• Pulmonary disease such as pneumonia, tuberculosis, or lung cancer
• Acute upper respiratory tract infection within the last 2 weeks
• Acute lower respiratory tract infection (requiring antibiotics or hospitalization) within the last 4 weeks
• Pulmonary exacerbation within the last 4 weeks
• Changes from routine maintenance therapy within the last 4 weeks
• Scheduled changes to inhaled antibiotics regimen during the course of the study
• Receive or are planned to receive any treatment via "on-off" regimen (e.g. Tobramycin - TOBI®); last dose of any "on-off" treatment within the last 6 weeks
• Any clinically significant liver, renal, cardiac, neurological, or hematological disease
• ABPA or colonization with Burkholderia cepacia
• Poorly controlled diabetes mellitus