Graft-versus-host disease (GvHD) is a major complication of allogeneic hematopoietic stem cell transplantation affecting 30-60 % of patients despite prophylactic treatment. Acute GvHD (aGvHD) primarily affects the gut, the liver and/or the skin while chronic GvHD (cGvHD) typically resembles rheumatological or autoimmune disorders [1]. The standard for first-line therapy of acute and chronic GvHD are corticosteroids while the second-line treatment is less standardized and includes among others calcineurin inhibitors, mycophenolate mofetil (MMF), mTOR-and JAK2-inhibitors. Methotrexate (MTX) is an established agent for GvHD prophylaxis but not for GvHD treatment [2, 3].