Inclusion Criteria:  Adult patients of ≥18 years at time of informed consent Patients with a clinical diagnosis of CF and confirmed by genetic testing Diagnosis of treatment naïve or treatment refractory M. abscessus-PD Signed informed consent documentation (indicating an understanding of the purpose and a willingness to meet the requirements for participation in the study)  Exclusion Criteria:  FEV1 <30% predicted Methaemoglobin concentration > 2% Use of nitric oxide donor medications such as prilocaine, sodium nitroprusside, and nitroglycerine within 30 days of proposed first treatment Use of phosphodiesterase inhibitors (e.g., sildenafil) within 30 days of proposed first treatment Evidence of pulmonary hypertension History of frequent low volume or massive haemoptysis Liver disease (i.e. liver cirrhosis, portal hypertension) Subjects who have undergone organ transplantation Pregnancy or lactation (female participants only) Subjects who will not use appropriate forms of contraception for the duration of the study Contraindication or unable to complete lung function testing Contraindication or unable to tolerate nebulised hypertonic saline Changes to previous NTM antibiotic regimen within two months of first dose of study treatment (or 4 months for clofazimine) Subject has received investigational treatment as part of another interventional clinical trial within two months of the proposed first day of treatment Required antibiotic treatment for a pulmonary exacerbation within 2 weeks of enrolment to the study. Inability to undergo study related activities and / or commitments Any subject who in the opinion of the investigator would not be best served by participating in this clinical trial.