Abstract Rationale Autoimmune pulmonary alveolar proteinosis (aPAP) is characterized by impaired alveolar macrophage function and elevated anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies. Previous studies demonstrated that human bone marrow-derived mesenchymal stem cells (hBMMSCs) can remodel the alveolar immune microenvironment and enhance macrophage phagocytic function. We conducted the first clinical study of hBMMSC therapy for aPAP to evaluate its safety and preliminary efficacy. Methods This phase IIa, open-label, single-arm clinical trial enrolled 10 aPAP patients, assigned to three groups: low-dose (1 × 106 cells/kg, single infusion), high-dose (2 × 106 cells/kg, single infusion), and high-dose repeated (2 × 106 cells/kg, two infusions two weeks apart), all via intravenous infusion. The primary endpoint was change in alveolar-arterial oxygen gradient (A-aDO2) from baseline to 24 weeks. Safety and tolerability were assessed by incidence of serious adverse events (SAEs). Results Of 10 subjects enrolled, 3 withdrew and 7 completed 24-week evaluation. No treatment-related SAEs occurred. In 7 evaluable subjects, A-aDO2 and oxygenation index (P/F ratio) improved significantly at 24 weeks compared with baseline (both p 0.05). Repeated high-dose infusion produced greater A-aDO2 improvement than single-dose groups. Conclusion This first clinical trial of hBMMSC therapy for aPAP demonstrates that the treatment is safe, well tolerated, and improves A-aDO2 and P/F ratio. Repeated dosing appears more effective than a single infusion, providing initial real-world clinical evidence supporting potential therapeutic application. This abstract is funded by: Jiuzhitang Maker(Beijing) Cell Technology Co.Ltd
Song et al. (2026) studied this question.