This study is a phase 2b, multicenter, randomized, double-blind, placebo-controlled, parallel-group, dose range finding study designed to explore the efficacy, safety, and tolerability of 2 active treatment regimens of CSL787 (immunoglobulin G [IgG] inhalation solution) compared with placebo over a period of 6 to 12 months independent of the occurrence of pulmonary exacerbations.

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 TTF exacerbation.

Inclusion Criteria:

• Adult between the ages of 18 to 85 years
• 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 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 either 1 of the following:
• >= 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 > 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 percentage of the predicted normal forced expiratory volume in 1 second of expiration [FEV1% predicted] > 35% and forced expiratory volume in 1 second (FEV1) >= 1 liter (L) obtained in accordance with American Thoracic Society (ATS) / European Respiratory Society (ERS) standards for spirometry during Screening and at Baseline.

Exclusion Criteria:

• History of 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 immunoglobulin.
• Primary diagnosis of other pulmonary disorders, including chronic obstructive pulmonary disease (COPD) asthma or, diffuse panbronchiolitis (DPB), as determined by the investigator.
• Pulmonary exacerbation requiring antibiotic therapy within the 4 weeks before Baseline.

CSL will consider on a case-by-case basis requests to share Individual Patient Data (IPD) with external bona-fide, qualified scientific and medical researchers. For information on the process and requirements for submitting a voluntary data sharing request for IPD, please contact CSL at clinicaltrials@cslbehring.com.

Requests for IPD will generally be considered once review by major regulatory authorities (i.e. FDA, EMA) is complete and the primary publication is available.

Proposed research should seek to answer a previously unanswered important medical or scientific question.

Applicable country specific privacy and other laws and regulations will be considered and may prevent sharing of IPD.

If the request is approved and the researcher has executed an appropriate data sharing agreement, IPD that has been appropriately anonymized will be available.