Itacitinib, Tacrolimus, and Sirolimus for the Prevention of GVHD in Patients With Acute Leukemia, Myelodysplastic Syndrome, or Myelofibrosis Undergoing Reduced Intensity Conditioning Donor Stem Cell Transplantation

Inclusion Criteria: * Documented informed consent of the participant and/or legally authorized representative * Assent, when appropriate, will be obtained per institutional guidelines * Agreement to allow the use of archival tissue from diagnostic tumor biopsies * If unavailable, exceptions may be granted with study principal investigator (PI) approval * Performance status: Karnofsky \>= 70% * Patients with neoplastic hematologic disorders with indication of allogeneic transplant according to the standard guidelines as follows: * Acute leukemia (AL) in first complete response (CR1) or subsequent complete response (CR) or active disease with bone marrow (BM) blast of \< 5% * Myelodysplastic syndrome (MDS) with intermediate-2 or high risk per International Prognostic Scoring System (IPSS) or * Myelofibrosis; primary or secondary if intermediate-2 or high risk per Dynamic International Prognostic Scoring System (DIPPS) * All candidates for this study must have a matched related donor (MRD) who is willing to donate BM or peripheral blood stem cells or an 8/8 allele matched unrelated donor (MUD) * Total bilirubin =\< 1.5 X upper limit of normal (ULN) (unless has Gilbert's disease) (performed within 28 days prior to day 1 of protocol therapy unless otherwise stated. In case of active disease, evaluation should be done within 15 days) * Aspartate aminotransferase (AST) =\< 2.5 x ULN (performed within 28 days prior to day 1 of protocol therapy unless otherwise stated. I…