This study is to evaluate an investigational study drug, itepekimab, for the treatment of bronchiectasis. The main purpose for this study is to assess the safety, efficacy, and tolerability of itepekimab in bronchiectasis in addition to the current background treatment you are receiving which may include bronchodilators, inhaled corticosteroids, mucolytics, and/or maintenance antibiotics. You will receive either the study drug or a placebo if you participate in this research. This study will include about 300 participants with bronchiectasis across approximately 20 countries worldwide.

Part A of this study will compare the effects of Clofazimine Inhalation Suspension to placebo. The purpose of this study is to find out if Clofazimine Inhalation Suspension can treat NTM lung disease by getting rid of the bacteria from the lungs and to make sure that Clofazimine Inhalation Suspension is safe for use. The participant will continue with current treatment for NTM lung disease in this study. To test if the bacteria are gone from the lungs, sputum will be tested on a regular basis (every month) to see if the culture changes from positive to negative. Participants will be randomly assigned by chance (like drawing numbers from a hat) to either Clofazimine Inhalation Suspension or placebo.

After the participant completes the study treatment in Part A, they will be eligible to receive Clofazimine Inhalation Suspension in Part B.

Approximately 234 participants will take part in the study at approximately 120 sites globally.

The study includes both a retrospective cross-sectional and prospective longitudinal cohort study design. Demographic and clinical data will be obtained through medical record review. 3-4 blood draws will be collected over the course of the study. If participants were also in the MAC2v3 or NTM PRO Cohort study, data collected for that study will be used in this study. About 450 subjects are expected to participate in this study at 7 research sites in the United States. Participation in this study is expected to last up to 12 months. During that time, participants will have about 3-4 study visits.