Itacitinib

This research is being done to learn whether drug called itacitinib, which is a novel inflammation- and immune-lowering drug (immunosuppressant), can be given before and after non-myeloablative peripheral blood stem cell transplantation (PBSCT; also known as a 'mini' transplant) to help prevent certain complications such as cytokine release syndrome (CRS) for patients with blood cancers, using peripheral blood from a relative. The investigators will also examine if by using itacitinib the investigators can reduce the duration of MMF (other immune suppressive drug administration posttransplant).