Belumosudil in patients with bronchiolitis obliterans syndrome phenotype of chronic lung allograft dysfunction: An exploratory single-center real-world retrospective study.

BACKGROUND: Chronic lung allograft dysfunction (CLAD) is a major cause of post-lung transplant mortality, with limited medical treatment options. This exploratory single-center real-world retrospective study aimed to evaluate the clinical outcomes and safety of belumosudil in lung transplant recipients with the bronchiolitis obliterans syndrome (BOS) phenotype of CLAD. METHODS: An exploratory single-center real-world retrospective study was conducted of lung transplant recipients with CLAD-BOS who received belumosudil for at least 3 months between September 2024 and November 2025. Primary endpoint was treatment response to belumosudil as classified based on changes in forced expiratory volume in 1 s (FEV1). RESULTS: A total of 17 CLAD-BOS patients were included (9 CLAD stage 1-2 patients and 8 CLAD stage 3-4 patients). Treatment response to belumosudil was assessed at 3, 6, and 12 months after initiating belumosudil. At 3 months, 17.6% of patients achieved a response, 64.7% remained stable, and 17.6% were non-responders. At 6 and 12 months, most patients showed stabilization or improvement in FEV1 (6 months: 68.8%, 11/16; 12 months: 70%, 7/10), while a minority exhibited a continued decline. All CLAD stage 1-2 patients achieved response or stabilization at 3 months, while no responses were observed in CLAD stage 3-4 patients. This stage-dependent pattern persisted at 6 and 12 months. Mixed-model analyses confirmed more favorable changes in FEV1 and forced vital capacity (FVC) in early-stage patients. No significant adverse events were observed. CONCLUSIONS: This exploratory single-center real-world study provides preliminary hypothesis-generating evidence that belumosudil may be associated with stabilization of pulmonary function in lung transplant recipients with CLAD-BOS, particularly when initiated during earlier disease stages. These findings require confirmation in larger prospective controlled studies.