Ruxolitinib Before, During and After Hematopoietic Cell Transplant in Older Patients With Myelofibrosis and Myelodysplastic Syndrome/Myeloproliferative Neoplasm Overlap Syndromes

OUTLINE: PART 1: Patients receive ruxolitinib or an alternate JAK-inhibitor for at least 8 weeks prior to the start of HCT conditioning. Starting on day -4, patients receive 5 mg of ruxolitinib orally (PO) or via nasogastric tube twice daily (BID) for 12 months then PO via nasogastric tube once daily (QD) until 18 months. Patients receive high intensity conditioning with cyclophosphamide intravenously (IV) on days -7 and -6 and busulfan IV over 3 hours on days -5 to -2 or reduced intensity conditioning with fludarabine IV over 30 minutes on days -6 to -2 and melphalan IV over 15-30 minutes on days -3 and -2. PART 2: Patients receive stem cells infusion on day 0. Starting on day -3, patients receive tacrolimus IV over 1-2 hours or PO every 12 hours for at least 100 days. Patients also receive methotrexate IV on days 1, 3, 6, and 11. Additionally, patients undergo urine sample collection, echocardiography (ECHO), chest computed tomography (CT) and pulmonary function testing prior to conditioning and blood sample collection throughout the study. Patients may also undergo bone marrow biopsy and aspiration, and/or spleen ultrasound or CT at multiple time points before and after transplant. After completion of study treatment, patients are followed at days 28, 100, 180, and at 9 months, 1 year, 18 months and 2 years.