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…