Dose Range Finding, Efficacy, and Safety Study of Nebulized CSL787 in Adults With Non-cystic Fibrosis Bronchiectasis (NCFB)

This study is a proof-of-concept phase 2b, multicenter, randomized, double-blind, placebo-controlled, parallel-group, dose selection study designed to explore the efficacy, safety, and tolerability of 2 active treatment regimens of CSL787 (human normal immunoglobulin G \[IgG\] inhalation solution) compared with placebo over 52 weeks. The primary aim of the study is to characterize the overall effect of CSL787 as well as the dose response of 2 active treatment regimens of inhaled CSL787 administered to participants with NCFB toward prolonging the time to first (TTF) exacerbation.

Inclusion Criteria: * Adult between the ages of 18 to 85 years * Capable of spontaneous sputum production at Screening. * Primary diagnosis of NCFB confirmed by chest computed tomography (CT) scan, where bronchiectasis has been documented by a radiologist. Diagnosis in the medical records based on documented historical scans is acceptable if the chest CT, scan confirming the participant's NCFB diagnosis was performed within 12 months before enrollment. Participants for whom no chest CT scan results are available within the previous 12 months will undergo a chest CT scan during the Screening Period. * Exacerbation history within the previous 1 year defined as one of the following: * greater than or equal (≥) 2 documented exacerbations requiring oral and/or intravenous (IV) antibiotic therapy to treat a pulmonary infection. OR * 1 documented exacerbation requiring oral and/or IV antibiotic therapy to treat a pulmonary infection and a St. George's Respiratory Questionnaire (SGRQ) Symptoms score of greater than (\>) 40 at Screening. * Note: Other medications to treat NCFB such as: oral macrolides, or dipeptidyl peptidase-1 (DPP-1) inhibitors are allowed, provided ≥ 1 historical exacerbation occurred while on the medication for ≥ 3 months at a stable dose. * Postbronchodilator percent predicted forced expiratory volume in 1 second (FEV1%) \> 35% and forced expiratory volume in 1 second (FEV1) ≥ 1 L obtained in accordance with American Thoracic Society (ATS) / European Respiratory Society (ERS) standards for spirometry during Screening and at Baseline on Day 1. Exclusion Criteria: * History of severe or uncontrolled asthma, or bronchospasm in response to inhaled therapies including inhaled antibiotics. * Known or suspected hypersensitivity, or other severe reactions, to the investigational product (IP), to any excipients of the IP, or to other immunoglobulins. * Primary diagnosis of other pulmonary disorders, including chronic obstructive pulmonary disease (COPD), asthma, or diffuse panbronchiolitis (DPB), as determined by the investigator. * Use of oral, IV, or inhaled antibiotic therapy to treat a pulmonary exacerbation or any other condition within 4 weeks before Baseline measurements on Day 1.