This is an interventional, randomized, double-blind, 2-arm, parallel groups, placebo-controlled, multi-center, phase 3 trial in adult subjects who are diagnosed with aPAP.~An aPAP diagnosis should be confirmed by an anti-GM-CSF auto-antibody test result, and history of PAP based on either high resolution computed tomography, lung biopsy, or bronchoalveolar lavage cytology, should be available.~The trial consists of a 6-week screening period, a 48-week randomized, double-blind treatment period, a 48-week open-label treatment period, and a conditional 4-week safety follow-up period. The maximum treatment duration will be 97 weeks and the maximum trial duration will be 108 weeks. During the trial, whole lung lavage will be allowed as rescue treatment in case of worsening of aPAP.
160 subjects with autoimmune pulmonary alveolar proteinosis (aPAP) will be randomized to receive once daily treatment with inhaled molgramostim or placebo for 48 weeks. Subjects completing the 48 week placebo-controlled period will receive open-label treatment with once daily inhaled molgramostim for 48 weeks.