Clinical Trial of Inhaled Molgramostim Nebulizer Solution in Autoimmune Pulmonary Alveolar Proteinosis (aPAP)

160 subjects with autoimmune pulmonary alveolar proteinosis (aPAP) will be randomized to receive once daily treatment with inhaled molgramostim (MOL) or placebo (PBO) for 48 weeks. Subjects completing the 48-week placebo-controlled period will receive open-label treatment with once daily inhaled molgramostim for 96 weeks.

Inclusion Criteria: 1. Subject must be ≥18 years of age, at the time of signing the informed consent (≥20 in Japan). 2. A serum anti-GM-CSF autoantibody test result confirming autoimmune PAP. 3. History of PAP, based on examination of a lung biopsy, bronchoalveolar lavage (BAL) cytology, or a high-resolution computed tomogram (HRCT) of the chest. 4. A diffusing capacity for carbon monoxide of 70% predicted or lower adjusted for hemoglobin (%DLCOadj) at the screening and baseline visits. 5. Change in %DLCO adj of \85% during 15 minutes without use of supplemental oxygen at the screening visits. 9. Male or female 10. Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. 1. Male subjects: Males agreeing to use condoms during and until 30 days after last dose of trial treatment, or males having a female partner who is using adequate contraception as described below. 2. Female subjects: Females who have been post-menopausal for \>1 year, or females of childbearing potential after a confirmed menstrual period using a highly efficient method of contraception (i.e. a method with \