This study investigates the effects of combining an investigational medication with inhaled therapy in people with cystic fibrosis who have a long-term infection with a specific bacteria called P. aeruginosa. Cystic fibrosis is a genetic condition that affects the lungs and digestive system. The study aims to see how this combination affects the health of the participants.

Participants will be randomly assigned to one of two study arms. One arm will receive the investigational medication, which is taken orally three times a week, while the other arm will receive a placebo, which is an inactive substance that looks like the investigational medication but does not contain any medicine. All participants will continue their usual inhaled therapy.

• Who can participate: Eligible participants must have cystic fibrosis and a history of P. aeruginosa infection. They must have used inhaled therapy and be able to stop certain antibiotics for a specified period.
• Study details: Participants will take either the investigational medication or a placebo orally three times a week. They will continue using their usual inhaled therapy. A placebo is an inactive substance that looks like the investigational medication but does not contain any medicine.