Phase I/II Study of Tagraxofusp in Combination With Decitabine for Patients With Myelomonocytic/Myeloproliferative Neoplasm and High Risk Myelodysplastic Syndromes

Inclusion Criteria: * The participant is ≥ 18 years old * Diagnosis of myelodysplastic/myeloproliferative neoplasm (MDS/MPN) according to World Health Organization (WHO) and: * Phase 1 dose escalation portion: CMML-1 or CMML-2 by WHO or higher-risk MDS (defined as IPSS-Revised score \>3.5 or with TP53 mutations) with \>5% blasts or MDS/MPN (other than CMML) with \>5% bone marrow blasts and no response after 6 cycles of azacitidine, decitabine, guadecitabine or ASTX727 (decitabine-cedazuridine) or relapse or progression after any number of cycles * Phase 2 dose expansion portion: * Relapsed cohort (Cohort A): CMML-1 or CMML-2 or higher-risk MDS (defined as IPSS-Revised score \>3.5 or with TP53 mutations) with \>5% blasts or MDS/MPN (other than CMML) with \>5% bone marrow blasts by WHO and no response after 6 cycles of azacitidine, decitabine, guadecitabine or ASTX727 (decitabine-cedazuridine) or relapse or progression after any number of cycles * Hypomethylating agents (HMA) naive cohort (Cohort B): previously untreated CMML-1 or CMML-2 and intermediate-2 or high-risk IPSS or higher-risk MDS (defined as IPSS-Revised score \>3.5 or with TP53 mutations) with \>5% blasts or MDS/MPN (other than CMML) with \>5% bone marrow blasts. * 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 or 2-dimensional (2-D) echocardiogram (ECHO) within 2…