RecruitingPhase 2Biological interventionStudy With Phage for CF Subjects With Pseudomonas Lung InfectionThe goal of this Phase 2b clinical trial is to see if nebulized phage (BX004) can treat chronic Pseudomonas aeruginosa (PsA) lung infection in CF subjects. The primary goal is to see if 8 weeks of twice daily BX004 can reduce the amount of PsA in the sputum compared to placebo (on top of background CF therapy).