Tagraxofusp Maintenance Therapy to Prevent Relapse in Patients with CD 123+ Myelofibrosis, Chronic Myelomonocytic Leukemia, Myelodysplastic Syndrome, or Acute Myeloid Leukemia who have Undergone a Stem Cell Transplant

Inclusion Criteria

• The patient is >=18 years old and =< 75 years old
• The patient has a life expectancy of > 6 months
• The patient has an Eastern Cooperative Oncology Group (ECOG) performance status (PS) of 0-2
• Left ventricular ejection fraction (LVEF) >= 50% as measured by multigated acquisition scan (MUGA) or 2-dimensional (2-D) echocardiogram (ECHO) and no clinically significant abnormalities on a 12-lead electrocardiogram (ECG) (withing 28 days of start of therapy)
• Serum creatinine =< 1.5 mg/dL (within 28 days of start of therapy)
• Bilirubin =< 1.5 mg/dL (within 28 days of start of therapy)
• Aspartate transaminase (AST) and alanine transaminase (ALT) =< 2.5 times the upper limit of normal (ULN) (within 28 days of start of therapy)
• Absolute neutrophil count (ANC) >= 0.5 × 10^9/L (withing 28 days of start of therapy)
• Platelets >= 80,000/mm^3 (within 28 days of start of therapy)
• Serum albumin >= 3.2 (within 28 days of start of therapy) (note that albumin infusions are not permitted in order to enable eligibility)
• Patient meets the 2016 World Health Organization (WHO) diagnostic criteria for MF, is CD123+, and has an International Prognostic Scoring System (IPSS)/Dynamic International Prognostic Scoring System (DIPSS)/DIPSS-plus intermediate-1 with anemia (hemoglobin [Hb] < 10g/dl), splenomegaly (> 12 cm), leukocytosis (WBC > 25K) intermediate-2 or high-risk disease pre transplant -Or- Patient has a 2016 WHO-defined diagnosis of CMML (persistent monocytosis >= 1 x 10^9/L for at least 3 months, with other causes excluded, and monocytes >= 10% of white blood cell [WBC] in peripheral blood, no criteria and no previous history of chronic myeloid leukemia [CML], essential thrombocythemia [ET], polycythemia vera [PV], and acute promyelocytic leukemia) pre transplant and is CD123+ -Or- Patient has 2016 WHO-defined CMML-1 (2-4% blasts in peripheral blood and/or 5-9% blasts in bone marrow) and CMML-2 (5-19% blasts in peripheral blood and/or 10-19% blasts in bone marrow, and/or presence of Auer rods) pre-transplant and is CD123+ -Or- Patient has CD123+ AML in morphologic remission pre transplant -Or- Patient has Intermediate or high risk MDS by Revised International Prognostic Scoring System (IPSS-R) or moderate or high risk by Molecular International Prognostic Scoring System for Myelodysplastic Syndromes (IPSS-M) pre transplant and has had no morphologic progression of disease post-transplant
• Receipt of first allogeneic stem cell transplant (related, unrelated, haploidentical or cord blood) 60-120 days prior to study registration
• Patient is in morphologic remission according to bone marrow biopsy completed within 30 days prior to planned start of study treatment
• Provision of signed and dated informed consent form
• Stated willingness to comply with all study procedures and availability for the duration of the study
• For females and males of reproductive potential: agreement to use adequate contraception for at least one month prior to screening, during and following participation
• For males of reproductive potential: use of condoms or other methods to ensure effective contraception with partner during and following participation
• Agreement to adhere to lifestyle considerations throughout study duration

Exclusion Criteria

• Treatment with any disease-related therapy, including radiation therapy or investigational agent, within 14 days of study entry
• Previous treatment with tagraxofusp or known hypersensitivity to any components of the drug product
• Active malignancy and/or cancer history (excluding myeloproliferative disorders and concomitant myeloid malignancies as specified in the inclusion criteria) that can confound the assessment of the study endpoints. Patients with a past cancer history (within 2 years of entry) and/or ongoing active malignancy or substantial potential for recurrence must be discussed with the sponsor before study entry. Patients with the following neoplastic diagnoses are eligible: non-melanoma skin cancer, carcinoma in situ (including superficial bladder cancer), cervical intraepithelial neoplasia, or organ-confined prostate cancer with no evidence of progressive disease
• Known active or suspected disease involvement of the central nervous system (CNS)
• Receiving > 10 mg prednisone daily for GVHD
• Overall >= grade 2 acute GVHD per Magic criteria at time of registration
• Pregnant or breast feeding
• Requirement of supplemental oxygen
• Clinically significant cardiovascular disease (e.g., uncontrolled or any New York Heart Association Class 3 or 4 congestive heart failure, uncontrolled angina, history of myocardial infarction or stroke within 6 months of study entry, uncontrolled hypertension or clinically significant arrhythmias not controlled by medication)
• Uncontrolled, clinically significant pulmonary disease (e.g., chronic obstructive pulmonary disease, pulmonary hypertension) that in the opinion of the Investigator would put the patient at significant risk for pulmonary complications during the study
• Uncontrolled intercurrent illness including, but not limited to, uncontrolled infection, disseminated intravascular coagulation, or psychiatric illness/social situations that would limit compliance with study requirements
• Known positive status for human immunodeficiency virus or active or chronic hepatitis B or hepatitis C
• Receiving treatment for known or suspected fungal infection (prophylaxis is acceptable)
• Known positive severe acute respiratory syndrome coronavirus-2 (SARS-COV-2) test within 3 weeks of study entry. Exception: Tests that reflect past, resolved infection where the patient is determined to not be infectious, according to an infectious disease specialist, do not exclude the patient from participation
• Pedal edema >= grade 2