Investigators will undertake an eighteen-week single centre, open label study in participants with cystic fibrosis infected with Mycobacterium abscessus (M. abscessus)-pulmonary disease (-PD).~The study will treat particpants with cystic fibrosis (CF) attending the Adult Cystic Fibrosis Centre at the Royal Papworth Hospital, Cambridge, United Kingdom. Participants will be consented and screened for the RESP301-003 study to enable approximately 12 participants to commence treatment with RESP301.~Participants will have M abscessus-PD as defined by the ATS/IDSA, specifically: (i) two or more positive sputum cultures for M. abscessus; (ii) radiological change consistent with NTM-PD; and (iii) symptoms consistent with NTM-PD, after exclusion of other causes.~Participants will be recruited who (1) have not commenced antibiotic treatment for M. abscessus-PD or (2) have treatment refractory M. abscessus-PD (defined as remaining sputum culture positive after 6 months or more of treatment). Treatment-refractory participants will be suitable for enrolment in the study if date of first dosing is at least 2 months since a change in M. abscessus treatment (or 4 months since change of Clofazimine).
To evaluate the change in M. abscessus cfu/g in induced sputum samples from baseline to the end of treatment with RESP301 in patients with cystic fibrosis who have treatment-naïve or treatment-refractory M. abscessus-pulmonary disease~To assess the safety and tolerability of RESP301 during treatment (28 days) and follow up (84 days) in patients with cystic fibrosis who have treatment naïve or treatment refractory M. abscessus-pulmonary disease