Pilot Trial of Inhaled Molgramostim in Non-tuberculous Mycobacterial (NTM) Infection

The study will comprise a Screening Visit, a Baseline Visit, a 24-week treatment period and a 12-week follow-up period. 30 adult participants with a history of chronic NTM infection with at least 2 positive cultures in the prior 2 years, of which at least one is within the last 6 months prior to Screening, will be considered for enrollment. Participants should provide a positive NTM sputum culture at Screening to be eligible. Two subgroups of participants will be recruited: * Group 1: Participants who remain sputum culture positive while currently on a multidrug NTM guideline based antimycobacterial regimen, which has been ongoing for at least 6 months prior to the Baseline Visit. * Group 2: Participants who remain sputum culture positive but have either stopped a multidrug NTM guideline based antimycobacterial regimen at least 28 days prior to Screening due to lack of response or intolerance, or never started such treatment. The treatment period will consist of 14 trial visits (Screening \[within 10 weeks of Baseline\], Baseline, and every 4 weeks to Week 48 \[visits at Weeks 28, 36 and 44 included telephone contact, others included clinic visits\]) and a Follow-up visit 12 weeks after the end of treatment. At the Baseline visit, eligible participants will start treatment with molgramostim nebulizer solution, 300 μg, administered by inhalation using an eFlow Nebulizer System. At each visit, sputum samples will be collected for staining and microscopy, and microbiological culture. In addition, clinical assessments including body weight, patient reported outcomes, and diffusion capacity of the lung for carbon monoxide (DLCO) will be conducted at each clinic visit. Spirometry will be assessed at Baseline, and at Weeks 12, 24, 32, 40 and 48. A 6-minute walk test (6-MWT) will be conducted at Baseline, at Weeks 12, 24, 48 and at the 12-week Follow-up visit. Safety laboratory samples will be collected at Screening, Baseline and at Weeks 4, 12, 24, 32, 40, 48 and at the 12-week Follow-up visit. Anti-GM-CSF antibodies will be assessed at Baseline, at Week 4, 12, 24, 32, 48, and at the 12-week Follow-up visit.