Efficacy of Azithromycin to Prevent Bronchiolitis Obliterans Syndrome After Allogeneic Hematopoietic Stem Cell Transplantation

Overview

The occurrence of bronchiolitis obliterans syndrome (SBO) after allogeneic hematopoietic stem cell transplantation (HSCT) is considered to be a chronic pulmonary graft versus host disease (GVHD) that is associated with significant mortality and morbidity. The reported incidence of SBO varies from 6 to 26% of allogeneic HSC recipients and is usually diagnosed within 2 years after transplantation. The diagnosis of SBO relies on the occurrence of a new airflow obstruction identified during pulmonary function testing, and the definition differs between studies. Currently, no curative immunosuppressive treatment is available, and recent data suggest that the use of these treatments, especially corticosteroids, should be limited because of their toxicity. The impairment of lung function parameters is likely caused by fibrous small airway lesions. Few data on the pathogenesis of SBO after allogeneic HSCT are available. Several hypotheses are based on the occurrence of SBO during chronic graft rejection after lung transplantation, which shares many clinical and histopathological similarities with SBO after allogeneic HSCT. One hypothesis is that the first step leading to SBO is lung epithelium injury. SBO is then identified as an alloimmune reaction with only one clearly identified risk factor: extrathoracic chronic GVHD. Due to their anti-inflammatory and immunomodulatory properties, recent data suggest that low-dose macrolides may be effective at preventing SBO after lung transplants. This well-tolerated treatment may be useful for preventing SBO after allogeneic HSCT. The objective of this Phase 3 multicentre randomized, double-blinded, clinical trial is to evaluate the efficacy of azithromycin in preventing BO syndrome after allogeneic HSCT in patients with malignant hematological diseases.