SERPINA1 and acute graft versus host disease: Alpha-1-Antitrypsin (AAT), a serine protease inhibitor with anti-inflammatory and immunomodulatory properties, has previously demonstrated good tolerability and clinical efficacy as a treatment for SR acute GVHD.48 BMT CTN 1705 is an ongoing randomized phase III trial that will compare the use of AAT with corticosteroids to corticosteroids alone as first-line therapy for subjects with high risk acute GVHD (NCT04167514).