• Males are eligible to participate if they agree to use contraception as described in the contraceptive guidance from Screening and throughout the study and for at least 30 days after the last dose of blinded study medication

• Females are eligible to participate if they are not pregnant, not breastfeeding, and 1 of the following conditions apply:

‣ Not a woman of childbearing potential (WOCBP) OR

⁃ A WOCBP who agrees to follow the contraceptive guidance from Screening throughout the study and for at least 30 days after the last dose of blinded study medication

• Clinical history consistent with bronchiectasis (cough, chronic sputum production, and/or recurrent respiratory infections) confirmed by chest CT demonstrating bronchiectasis affecting 1 or more lobes. Confirmation may be based on prior chest CT within the prior 5 years; subjects whose past CT image records are not available will require chest CT scan during screening Notes: If a subject has no clinical history consistent with bronchiectasis, they may not be re-screened

• Current sputum producer with a history of chronic expectoration and able to provide sputum sample spontaneously at the clinic during screening

• ≥ 1 documented pulmonary exacerbation defined by an antibiotic prescription by a physician for the signs and symptoms of respiratory infections in the past 12 months before screening

• Capable of using the study nebulizer correctly

• Ability to perform acceptable spirometry in accordance with American Thoracic Society and European Respiratory Society guidelines