Inclusion Criteria:

1. Must be >= 18 years of age and, in selected countries, adolescents aged 12 years and greater and weighing >=30 kilogram (kg) at time of randomization.
2. Must undergo deoxyribose nucleic acid (DNA)-based human leukocyte antigen (HLA) matching and be 8 of 8 or 7 of 8 HLA-matched (singe allele or antigen mismatch at HLA-A, -B, and -C, and HLA-DRB1 is allowable) unrelated hematopoietic stem cell transplantation (HSCT) from either peripheral blood or bone marrow stem cells for a hematologic malignancy or myeloproliferative disorder.
3. For whom a myeloablative conditioning or reduced intensity conditioning (RIC) is planned.
4. Allo-HSCT eligible (meeting institutional criteria)-participants planned medical care should include aGvHD prophylaxis with a combination of calcineurin inhibitor (CNI) (cyclosporine \[CYS\] or tacrolimus \[TAC\]) and methotrexate (MTX) or CNI and mycophenolate mofetil (MMF). With the exception of antithymocyte globulin (ATG) (antithymocyte globulin-Fresenius \[ATG-F\] or thymoglobulin), all other therapies, approved or investigational, for GvHD prophylaxis are excluded.
5. Eastern Cooperative Oncology Group (ECOG) performance status of <= 2 for participants aged >=18 years at randomization or >=60 % using the Karnofsky performance status for adolescent participants aged >=16 years at randomization or the Lansky performance status for adolescent participants aged 12 to < 16 years at randomization.

Exclusion Criteria:

1. Had prior allo- HSCT.
2. Planned umbilical cord blood transplant or planned to receive posttransplant cyclophosphamide, in vivo or ex vivo T cell-depleted hematopoietic stem cells (HSCs) with the exception of ATG (ATG-F or thymoglobulin).
3. Planned allo-HSCT for nonmalignant hematological disorders (example, aplastic anemia, sickle cell anemia, thalassemias, Fanconi anemia or immunodeficiency).