Axatilimab With or Without Azacitidine for the Treatment of Patients With Advanced Phase Myeloproliferative Neoplasms, Myeloproliferative Neoplasm/Myelodysplastic Syndrome Overlap or High Risk Chronic Myelomonocytic Leukemia

Inclusion Criteria

• Signed informed consent must be obtained prior to participation in the study
• Age ≥ 18 years at the date of signing the informed consent form (ICF)
• Morphologically confirmed diagnosis of the following based on 2016 World Health Organization (WHO) classification (Arber et al 2016): Phase 1b, patients with relapsed or refractory of any of the following; phase 2, patients with newly diagnosed of any of the following: * Chronic myelomonocytic leukemia (CMML), classified as intermediate-2, OR high-risk per the CMML Specific Prognostic Scoring System (CPSS) Molecular Model * Atypical chronic myelocytic leukemia (aCML) * MDS/MPN unclassified (MDS/MPN-U) * Myeloproliferative neoplasm accelerated phase (MPN-AP) * MPN-AP requires a previous diagnosis of polycythemia vera (PV), essential thrombocythemia (ET), or primary myelofibrosis (PMF) with intermediate-2 or high risk disease according to International Prostate Symptom Score (IPSS) as well as progression on or failure to respond to at least one line of therapy. * Myelodysplastic syndrome/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/MPN-RS-T) or MDS/MPN with SF3B1 mutation and thrombocytosis (MDS/MPN-SF3B1-T). * Not suitable for immediate myeloablative/intensive chemotherapy based on investigator assessment of age, comorbidities, local guidelines, institutional practice (any or all of these)
• Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1 or 2
• Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 3 × upper limit of normal (ULN)
• Total bilirubin ≤ 1.5 × ULN (except in the setting of isolated Gilbert syndrome)
• Estimated glomerular filtration rate (eGFR) ≥ 30 mL/min/1.73m^2 (estimation based on Modification of Diet in Renal Disease [MDRD] formula, by local laboratory)
• Patient is able to communicate with the investigator and has the ability to comply with the requirements of the study procedures
• Women of childbearing potential and men, if not surgically sterilized, should use adequate contraception from 14 days prior to study entry and until 90 days after the last follow-up visit. Adequate contraception is defined as using hormonal contraceptives or an intrauterine device combined with at least 1 of the following forms of contraception: a diaphragm or cervical cap, or a condom

Exclusion Criteria

• Previous treatment for MPN or MDS/MPN overlap with chemotherapy or other antineoplastic agents including lenalidomide and hypomethylating agent (HMAs) such as decitabine or azacitidine or INQOVI (oral decitabine) (patients who had up to 2 cycles of hypomethylating agents [HMAs] can be included). However, previous treatment with hydroxyurea and/or ruxolitinib is permitted
• Diagnosis of acute myeloid leukemia (AML) including acute promyelocytic leukemia and extra-medullary AML based on WHO 2016 classification (Arber et al 2016)
• Patients who are candidates for myeloablative or intensive chemotherapy treatment or who do not provide consent for this treatment
• History of organ transplant or allogenic hematopoietic stem cell transplant
• Participants with prior malignancy, except: * Participants with history of adequately treated malignancy for which no anticancer systemic therapy (namely chemotherapy, radiotherapy or surgery) is ongoing or required during the course of the study. * Participants who are receiving adjuvant therapy such as hormone therapy are eligible. However, participants who developed therapy related neoplasms are not eligible
• Previous known allergy/sensitivity to components of axatilimab
• History of acute or chronic pancreatitis
• History of myositis