The efficacy of mesenchymal stem cells in bronchiolitis obliterans syndrome after allogeneic HSCT: A multicenter prospective cohort study

BACKGROUND: Bronchiolitis obliterans syndrome (BOS) after allo-HSCT is a devastating complication with limited therapeutic options. We aimed to assess the efficacy and safety of mesenchymal stem cells (MSCs) in BOS after allo-HSCT. METHODS: This multicenter prospective cohort study enrolled 81 allo-HSCT recipients whose BOS were diagnosed within 6 months. The choice of prednisone and azithromycin combined with or without MSCs was based on patient preferences (MSC n = 49, non-MSC n = 32). The primary endpoint was response rate at 3 months, defined as the proportion of patients achieving FEV1 improvement or steroid sparing. The trial was registered at ClinicalTrials.gov (NCT02543073). FINDINGS: Response rate was 35/49 patients (71%, 95% CI 59 to 84%) and 14/32 (44%, 27 to 61%) in MSC and non-MSC group, respectively (p = 0.013). The addition of MSCs was associated with a better difference for change in FEV1 rate of decline, compared to non-MSC group (53 mL/months, 2 to 103; p = 0.040). The 3-year overall survival post-diagnosis was 70.6% (55.9 to 85.3%) and 58.2% (36.1 to 78.5%) in MSC and non-MSC group, respectively (p = 0.21). Clinical improvement was accompanied by a significant increase of interleukin (IL)-10-producing CD5+B cells. There was no statistical difference in the rates of infections and leukemia relapse between the two groups. MSCs were well-tolerated with no serious adverse events. INTERPRETATION: MSCs offer an effective and safe therapeutic option for BOS after allo-HSCT. Our study strengthens evidence for clinical use of MSC therapy in BOS. These data also provide novel insight into potential biological mechanisms of MSC treatment and support further investigation in larger randomized controlled trials. FUNDING: National Key R&D Program of China, National Natural Science Foundation of China, Health Collaborative Innovation Major Projects of Guangzhou City, Science and Technology Planning Project of Guangdong Province.