Relapsed disease is the primary cause of treatment failure after hematopoietic cell transplant (HCT). In this study, patients are given increasing levels of tagraxofusp (Tag) to evaluate the safety of each dose. Participants will start treatment with Tag starting between 60 and 120 days following HCT. Tag will be given by IV over about 15 minutes on days 1 through 3 of cycles 1-4 of treatment (28 day cycles) and then on days 1 and 2 of subsequent cycles, for up to 9 cycles or until disease progression or if you have a bad side effect. In the first cycle, Tag will be given while participants are inpatient. In all other cycles, Tag will be given outpatient and participants will be observed for 4 hours following each infusion. After about 4 cycles of treatment and again about 1 year after HCT, participants will have a bone marrow biopsy and also take a questionnaire about their quality of life. During the study, participants will have their blood checked regularly to monitor for side effects.
In this study, tagraxofusp (Tag) is given to patients with CD 123+ myelofibrosis (MF), chronic myelomonocytic leukemia (CMML), and acute myeloid leukemia (AML) after allogeneic stem cell transplant (HCT) to help prevent relapse. Patients will receive up to about 9 cycles of treatment with Tag and have a bone marrow biopsy after cycle 4 and about 1 year after HCT.