This is a randomized, double-blind, placebo-controlled study to measure the reduction in mucus plug score at 24 weeks of treatment with SAR445399 compared with placebo in adult participants aged 18 to 80 years with non-cystic fibrosis bronchiectasis (NCFB).

Inclusion Criteria:

• Participants must be 18 to 80 years of age inclusive, at the time of signing the informed consent
• Clinical history consistent with NCFB, such as chronic productive cough and/or recurrent respiratory infections
• Documented evidence of at least 2 PEx defined as episodes requiring a physician-prescribed course of antibiotics (oral and/or IV) for ≥5 days for signs and symptoms of respiratory infection within the 12 months prior to the Screening Visit
• Radiologic evidence of bronchiectasis, confirmed by a chest HRCT
• A minimum MPS of 4 (out of maximum 18) on chest HRCT performed before Baseline Visit
• Current sputum production with a documented history of chronic expectoration lasting ≥3 months within the previous 12 months
• Participants must have a post-bronchodilator FEV1 ≥30% of predicted normal value

Exclusion Criteria:

• A primary diagnosis of smoking-related COPD or asthma as determined by the Investigator. Participants with comorbid smoking-related COPD may be included if bronchiectasis is confirmed as their primary diagnosis and is the predominant cause of their respiratory symptoms
• Diagnosis of ABPA or any of the allergic bronchopulmonary mycoses
• Active NTM lung infection or incomplete NTM treatment course
• Bronchiectasis due to any of the following: CF, CVID, AAT or PCD
• History of significant hemoptysis (requiring medical intervention and/or requiring blood transfusion)
• Current tobacco smokers
• Known or suspected immunosuppression, including history of invasive opportunistic infections (eg., histoplasmosis, listeriosis, coccidioidomycosis, pneumocystosis, aspergillosis), despite infection resolution, or otherwise recurrent infections of abnormal frequency, or prolonged infections suggesting an immune-compromised status, as judged by the Investigator
• Participants with active autoimmune disease or participants using immunosuppressive therapy for autoimmune disease, including but not limited to connective tissue diseases (eg., systemic lupus erythematosus, scleroderma, polymyositis, dermatomyositis, mixed connective tissue disease), rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis, Hashimoto's thyroiditis, Graves' disease, primary biliary cirrhosis, and psoriasis vulgaris

The above information is not intended to contain all considerations relevant to a participant's potential participation in a clinical trial.

Qualified researchers may request access to patient level data and related study documents including the clinical study report, study protocol with any amendments, blank case report form, statistical analysis plan, and dataset specifications. Patient level data will be anonymized and study documents will be redacted to protect the privacy of trial participants. Further details on Sanofi's data sharing criteria, eligible studies, and process for requesting access can be found at: https://vivli.org

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