The study was brought to an early close in March 2022 due to major ongoing recruitment issues primarily related to the COVID-19 pandemic and concerns regarding the continued randomization and exposure of subjects to placebo in the study.

The primary objective of the trial was to investigate the effect of the use of inhaled colistimethate sodium (CMS), administered twice a day (b.i.d.) via a specific nebulizer for 12 months, compared to placebo in subjects with non-cystic fibrosis bronchiectasis (NCFB) chronically infected with P. aeruginosa on the annualised frequency of pulmonary exacerbations.

This was a randomised, multi-centre, double-blind, placebo-controlled, parallel-group interventional trial in subjects with NCFB chronic P. aeruginosa infection. Subjects were randomised to CMS or placebo in a 1:1 ratio. The study consisted of 7 clinic visits with a follow-up phone call 12.5 month after randomisation or 2 weeks after discontinuation of treatment. Additional clinic visits, where feasible, and weekly phone calls were conducted during or after pulmonary exacerbations (or any episodes of pneumonia) until resolution.

Every effort was made to have all planned and unscheduled visits at the study site. Mandatory on-site visits were Screening Visit (Visit 1) and Randomisation (Visit 2). However, if one of the visits after Visit 2 could not be performed at site due to COVID-19, remote visits (e.g., by telephone) were permitted. If the final visit (Visit 7) had to be conducted remotely, the subjects were asked to return to the clinic for on-site assessments at the earliest opportunity.

After consulting with the US Food and Drug Administration, the study was brought to an early close primarily due to the difficulty of recruiting subjects in the context of the COVID pandemic, but also due to the potential for loss of scientific equipoise and the ethical implications of continuing to expose subjects to placebo given the positive results from PROMIS I. Recruitment to PROMIS II was stopped as of 27 October 2021, with the study terminated as of 15 March 2022. The study was not stopped prematurely due to any safety or futility concerns and the accrued data were fully analysed and are presented.

Inclusion Criteria:

1. are able and willing to give informed consent, following a detailed explanation of partecipation in the protocol and signed consent obtained;
2. aged 18 years or older of either gender;
3. diagnosed with NCFB by computerised tomography (CT) or high-resolution CT(HRCT) as recorded in the subject's notes and this is their predominant condition being treated;
4. had at least 2 NCFB pulmonary exacerbations requiring oral or inhaled antibiotics or 1 NCFB 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;
5. have a documented history of P. aeruginosa infection;
6. are clinically stable and have not required a change in pulmonary treatment for at least 30 days before the Screening Visit (Visit 1);
7. have pre-bronchodilator FEV1 ≥25% of predicted;
8. had a positive sputum culture for P. aeruginosa from an adequate sample taken at the Screening Visit (Visit 1) or during the screening period.

Exclusion Criteria:

1. known bronchiectasis as a consequence of cystic fibrosis (CF);
2. known history of hypogammaglobulinaemia requiring treatment with immunoglobulin, unless fully replaced and considered immuno-competent by the Investigator;
3. myasthenia gravis or porphyria;
4. 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;
5. had major surgery in the 3 months prior to the Screening Visit (Visit 1) or planned inpatient major surgery during the study period;
6. receiving treatment for allergic bronchopulmonary aspergillosis (ABPA);
7. massive haemoptysis (greater than or equal to 300 mL or requiring blood transfusion) in the preceding 4 weeks before Screening Visit (Visit 1) or between Visit 1 and Visit 2;
8. respiratory failure that would compromise patient safety or confound the evaluation of safety or efficacy of the study in the opinion of the Investigator;
9. current active malignancy, except for basal cell carcinoma or squamous cell carcinoma of the skin without metastases;
10. taking immunosuppressive medications (such as azathioprine, cyclosporine, tacrolimus, sirolimus, mycophenolate, rituximab), and/or anti cytokine medications (such as anti-IL-6 and anti-tumour alpha necrosis factor products) in the preceding year before the Screening Visit (Visit 1);
11. known history of human immunodeficiency virus (HIV);
12. current treatment for non-tuberculous mycobacterial (NTM) lung disease or tuberculosis;
13. 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;
14. treatment with long term (≥ 30 days) prednisone at a dose of greater than 15 mg a day (or equivalent dose of any other corticosteroid) started within six months of the Screening Visit (Visit 1);
15. new maintenance treatment with any oral macrolides ( (e.g. azithromycin/erythromycin/clarithromycin) within 30 days of the Screening Visit (Visit 1) or started between Visit 1 and Visit 2;
16. 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;
17. 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;
18. 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;
19. participated in another investigational, interventional trial within 30 days prior to the Screening Visit (Visit 1);
20. in the opinion of the Investigator not suitable for inclusion for whatever reason.