Inclusion Criteria: 1. Males or females, age 18 to 65 years at Screening Visit, inclusive 2. Diagnosis of CF 3. ppFEV1 value between 50-100% (inclusive) 4. Resting oxygen saturation ≥94% on room air by pulse oximetry 5 . Clinically stable CF disease as assessed by the Investigator and not requiring any new class of interventional treatment within the last 3 months prior to Screening Exclusion Criteria: 1. Any change in established pulmonary treatment (including antibiotics) within 28 days prior to Screening Visit. However, inhaled beta-agonists can be included within 2 weeks prior to Screening Visit. 2. Clinically significant episode of hemoptysis (\>50 mL or ¼ cup or 10 teaspoons per day) within 12 weeks prior to dosing with study drug on Day 1 3. Lung infection with Mycobacterium abscessus associated with a more rapid decline in pulmonary status 4. Currently receiving treatment for active lung infection with Burkholderia cenocepacia or Burkholderia dolosa 5. History of solid organ or hematological transplantation 6. History of clinically significant cirrhosis with or without portal hypertension 7. History of pulmonary hypertension 8. History of cardiotoxicity, a history of known coronary artery disease, and/or existing cardiomyopathy 9. Current active fungal infection (not just a positive culture), acute blood, lung, or bladder infection, clinically significant hepatic or renal dysfunction, and/or viral infection (including human immunodeficiency virus or hepatitis virus B or C) requiring the initiation of new therapy within 30 days prior to Screening 10. History of allergic bronchopulmonary aspergillosis (ABPA) 11. Uncontrolled diabetes mellitus, as evidenced by hemoglobin A1c \>9% at Screening 12. Clinically significant laboratory abnormalities at Screening 13. Subjects with any medical condition or abnormal laboratory result that, in the opinion of the Investigator, will interfere with the safe completion of the study 14. Subjects who received any investigational products within 30 days (or 5 therapeutic half-lives, whichever is longer) prior to Screening 15. Subjects who have previously received any gene therapy agent 16. Subjects with known sensitivity to SP-101, doxorubicin or its excipients