Inclusion Criteria:  Participants must be ≥18 years of age at the time of signing the informed consent.  Male or female participants with a confirmed diagnosis of CF related lung disease:  a. Stable CF treatment for at least 30 days and willing to remain on a stable regimen throughout the treatment period.  Has a body mass index ≥18 kg/m^2.  Male and female participants must use contraceptives that are consistent with local regulations regarding the methods of contraception for those participating in clinical studies.  Male participants, who are not sterile, with female partners of childbearing potential must be using effective contraception from Day 1 to at least 90 days after the last dose. Women must be postmenopausal (defined as no menses for 12 months without an alternative medical cause), surgically sterile, or using highly effective contraception methods (ie, methods that alone or in combination achieve <1% unintended pregnancy rates per year when used consistently and correctly) from Day 1 to at least 90 days after the last dose. Male participants with pregnant or nonpregnant women of childbearing potential partners must use a condom.  Exclusion Criteria:  Severe or unstable CF, per Investigator's judgement. . Currently being treated for allergic bronchopulmonary aspergillosis or nontuberculous mycobacteria or tuberculosis. Active and current infection by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). History of malignancy in the past 5 years, except completely treated in situ carcinoma of the cervix and completely treated non-metastatic squamous or basal cell carcinoma of the skin. Established diagnosis of hepatitis B viral infection or positive for hepatitis B surface antigen (HBsAg) at Screening. History of human immunodeficiency virus (HIV) infection. Acute upper or lower respiratory tract infection, pulmonary exacerbation, or changes in therapy (including intravenous and oral antibiotics) for pulmonary disease within 4 weeks prior to Day 1 (administration of the first dose of study drug). Participants meeting this criterion could be rescreened 4 weeks after resolution of symptoms. History of solid organ or hematological transplantation. Currently being treated for periodontal disease. Received any live attenuated vaccine within 4 weeks prior Screening. Ongoing participation in another therapeutic clinical study or prior participation in an investigational drug study within 90 days prior to Screening. Known history of hypersensitivity to brensocatib or any of its excipients. Use of any immunomodulatory agents within 4 weeks before the Screening Visit is prohibited during the study through end of study (including, but not limited to: bortezomib, ixazomib, thalidomide, cyclophosphamide, mycophenolate, Janus kinase inhibitors, interferon gamma (IFN-γ], and azathioprine). Continuous use of high-dose non-steroidal anti-inflammatory drugs (NSAIDs) is prohibited during the study through end of study. History of alcohol, medication, or illicit drug abuse. Current smoker, as defined by Centers for Disease Control and Prevention: An adult who has smoked 100 cigarettes in his or her lifetime and who currently smokes cigarettes.