Typical GvHD prophylaxis and treatment consists of standard immunosuppressive medication such as calcineurin inhibitors (ciclosporin or tacrolimus) and/or methotrexate, anti-T-lymphocyte globulin (ATG), and post-transplant cyclophosphamide, as well as steroids and several candidates for steroid-refractory GvHD, including ibrutinib (which is approved by the FDA), alemtuzumab, JAK inhibitors, rituximab, mammalian target of rapamycin (mTOR) inhibitors, and others [15]. The gene discussed is MTOR; the disease is graft versus host disease.