Ruxolitinib Phosphate and Chemotherapy Given Before and After Reduced Intensity Donor Stem Cell Transplant in Treating Patients With Myelofibrosis

This pilot clinical trial studies the side effects and best dose of ruxolitinib phosphate when given together with chemotherapy before and after a donor stem cell transplant in treating patients with myelofibrosis. Ruxolitinib phosphate may stop the growth of cancer cells by blocking some of the enzymes needed for cell growth. Drugs used in chemotherapy, such as fludarabine phosphate and melphalan, work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Giving ruxolitinib phosphate together with chemotherapy before and after a donor stem cell transplant may help stop the growth of cells in the bone marrow, including normal blood-forming cells (stem cells) and cancer cells. It may also stop the patient's immune system from rejecting the donor's stem cells. When the healthy stem cells from a donor are infused into the patient they may help the patient's bone marrow make stem cells, red blood cells, white blood cells, and platelets. The donated stem cells may also replace the patient?s immune cells and help destroy any remaining cancer cells.