A Study of Cusatuzumab Plus Azacitidine in Japanese Participants With Newly Diagnosed Acute Myeloid Leukemia or High-risk Myelodysplastic Syndrome Who Are Not Candidates for Intensive Treatment

Inclusion Criteria: * For acute myeloid leukemia (AML) participants: AML according to World Health Organization (WHO) 2016 criteria and fulfilling all of the following criteria:(a) more than or equal to (\>=) 75 years of age, or younger participants who are not eligible for or not willing to receive an intensive treatment (including stem cell transplantation) with curative intent and (b) previously untreated AML (except: emergency leukapheresis, low dose of cytarabine and/or hydroxyurea during the screening phase to control hyperleukocytosis but must be discontinued at least one day prior to start of cusatuzumab \[Part 1\] or azacitidine \[Part 2\]). All trans retinoic acid (ATRA) treatment for presumed acute promyelocytic leukemia (APL) is permitted but must be discontinued at least 1 day prior to the start of cusatuzumab (Part 1) or azacitidine (Part 2) * For Myelodysplastic Syndrome (MDS) participants (only for Part 2): MDS according to WHO 2016 criteria and fulfilling all of the following criteria: (a) Not eligible for or not willing to receive allogenic stem cell transplantation,(b) very high or high-risk MDS according to Revised International Prognostic Scoring System (IPSS-R) and (c) previously untreated MDS (except: transfusion and/or cytokine therapy including erythropoietin) * Eastern Cooperative Oncology Group (ECOG) performance status score of 0, 1 or 2 * Must sign an informed consent form (ICF) indicating that he or she understands the purpose of, and procedures required for, the study and is willing to participate in the study * A woman of childbearing potential must have a negative highly sensitive serum (beta human chorionic gonadotropin \[beta hCG\]) or urine pregnancy at screening Exclusion Criteria: * Acute promyelocytic leukemia (APL) with t (15;17), or its molecular equivalent promyelocytic leukemia retinoic acid receptor (PML RAR alpha) * Leukemic involvement or clinical symptoms of leukemic involvement of the central nervous system * Known allergies, hypersensitivity, or intolerance to cusatuzumab or azacitidine or its excipients (example, mannitol, an excipient of azacitidine) * Prior treatment with a hypomethylating agent for treatment of AML or MDS * A diagnosis of other malignancy that requires concurrent nonsurgical treatment