This study focuses on people with Cystic Fibrosis who have ongoing lung infections caused by bacteria called Pseudomonas aeruginosa. The study will test a new inhaled treatment called BX004, which contains natural substances called bacteriophages that specifically target these bacteria. The treatment is given through a special breathing device called an eFlow Nebulizer System, which turns the medication into a fine mist that can be inhaled into the lungs.

The main goal of this research is to determine if BX004 can reduce the amount of Pseudomonas aeruginosa bacteria in the lungs of people with Cystic Fibrosis after 8 weeks of treatment. During the study, some participants will receive BX004 while others will receive a placebo through the nebulizer. Neither the participants nor their doctors will know which treatment they are receiving during the study.

The study will last for about 60 days, during which participants will need to inhale the study medication. Throughout the study, doctors will collect samples and monitor how well the treatment is working by checking lung function, quality of life, and watching for any side effects. The treatment being tested is designed to be used alongside standard medications that patients normally take for their Cystic Fibrosis.