 Autoimmune PAP is a rare lung disease affecting less than 5,000 individuals in US with no FDA-approved pharmacologic therapy. Results from off-label use in case reports and clinical studies completed outside of the US indicate that inhaled rhGM-CSF may be a safe and effective thera-py for autoimmune PAP. Preliminary clinical trials of inhaled rhGM-CSF in autoimmune PAP patients show promising results, 62-96 therapeutic response rate without any identifiable drug-related adverse effects in at least 73 autoimmune PAP patients. However, the pharmacokinetics PK, pharmacodynamics PD, optimal dose, and treatment duration to maximize efficacy are unknown. 