Safety, Tolerability and Efficacy Study of ARCT-032 in People With Cystic Fibrosis

Key Inclusion Criteria: 1. Confirmed diagnosis of Cystic Fibrosis 2. Not eligible for CFTR modulator therapy or not taking CFTR modulators for at least 60 days prior to dosing (e.g. due to intolerance, poor response, or lack of access to modulators) 3. FEV1 between 40% to 100% (cohorts 1-3) and 45% to 90% (cohort 4, inclusive) of predicted value for age, sex and height Exclusion Criteria: 1. History of illness or medical condition that might pose an additional risk or may confound study results 2. Recent moderate or severe hemoptysis 3. Recent major surgery 4. Solid organ or hematologic transplant 5. Requirement of supplemental oxygen while awake or \> 2L per minute while sleeping. 6. Chronic maintenance systemic corticosteroids exceeding equivalent of daily 15 mg oral prednisone or 30 mg every other day 7. Adequate liver and kidney function as determined by lab tests