Inclusion Criteria:

• Are able and willing to give informed consent, following a detailed explanation of participation in the protocol and signed consent obtained.
• Are aged 18 years or older of either gender.
• Have been diagnosed with NCFB by CT (or high-resolution CT) as recorded in the subject’s notes.
• Have had at least 2 pulmonary exacerbations requiring oral antibiotics or 1 pulmonary exacerbation requiring intravenous antibiotics in the 12 months preceding the Screening Visit (Visit 1) and had no pulmonary exacerbation with or without treatment during the period between Visit 1 and Visit 2.
• Have a documented history of P. aeruginosa infection.
• Are clinically stable and have not required a change in pulmonary treatment for at least 30 days before the Screening Visit (Visit 1).
• Have pre-bronchodilator FEV1 ≥ 30% of predicted.
• Have had a positive sputum culture for P. aeruginosa from an adequate sample taken at the Screening Visit (Visit 1).

Exclusion Criteria:

• Known bronchiectasis as a consequence of cystic fibrosis (CF).
• Known history of hypogammaglobulinaemia requiring treatment with immunoglobulin, unless fully replaced and considered immuno-competent by the Investigator.
• Myasthenia gravis or porphyria.
• Severe cardiovascular disease such as severe uncontrolled hypertension, ischaemic heart disease or cardiac arrhythmia and any other conditions that would confound the evaluation of safety, in the opinion of the Investigator.
• Have had major surgery in the 3 months prior to the Screening Visit (Visit 1) or planned inpatient major surgery during the study period.
• Are receiving treatment for ABPA.
• Have had massive haemoptysis (greater than or equal to 300 mL or requiring blood transfusion) in the preceding 4 weeks before the Screening Visit (Visit 1) or between Visit 1 and Visit 2.
• Having respiratory failure that would compromise patient safety or confound the evaluation of safety or efficacy of the study in the opinion of the Investigator.
• Current active malignancy, except for basal cell carcinoma of the skin without metastases.
• Taking immunosuppressive medications (such as azathioprine, methotrexate, cyclosporin, tacrolimus, sirolimus, mycophenolate, anti-cytokine medications, rituximab, anti-IL-6 and anti-tumour alpha necrosis factor products) in the preceding year before the Screening Visit (Visit 1).
• Known history of human immunodeficiency virus (HIV).
• Current treatment for non-tuberculous mycobacterial (NTM) lung disease or tuberculosis.
• Known or suspected to be allergic or unable to tolerate colistimethate sodium (intravenous or inhaled) or other polymixins, including evidence of bronchial hyper-reactivity following inhaled colistimethate sodium.
• Treatment with long term (≥ 30 days) prednisone at a dose of greater than 15 mg a day (or equivalent dose of any other corticosteroid) (e.g.,  azithromycin/ erythromycin/clarithromycin) started within six months of the Screening Visit (Visit 1).
• New maintenance treatment with any oral macrolides within 30 days of the Screening Visit (Visit 1) or started between Visit 1 and Visit 2.
• Use of any intravenous or intramuscular or oral or inhaled anti-pseudomonal antibiotic (except chronic macrolides with a stable dose) within 30 days prior to the Screening Visit (Visit 1) and between Visit 1 and Visit 2.
• Pregnant or breast-feeding or plan to become pregnant over the next two years or of child-bearing potential and unwilling to use a reliable method of contraception for at least one month before randomisation and throughout their involvement in the trial.
• Significant abnormality in clinical evaluations and/or laboratory tests (physical examination, vital signs, haematology, clinical chemistry, clinically relevant impaired renal function, defined as serum creatinine levels ≥ 2.0x upper limit of normal, ECG) endangering the safe participation of the patient in the study at the Screening Visit (Visit 1) and during the study.
• Participated in another investigational, interventional trial within 30 days prior to the Screening Visit (Visit 1).
• In the opinion of the Investigator, not suitable for inclusion for whatever reason.

Eligibility last updated 12/7/21. Questions regarding updates should be directed to the study team contact.