A Study of Cusatuzumab in Combination With Azacitidine Compared With Azacitidine Alone in Patients With Higher-risk Myelodysplastic Syndrome (MDS) or Chronic Myelomonocytic Leukemia (CMML) and Who Are Not Candidates for Hematopoietic Stem Cell Transplantation (HSCT)

Prior treatment

• Received prior HSCT or any prior treatment, including hypomethylating agent (HMAs), for higher-risk MDS or CMML. Prior supportive therapies including transfusion and growth factors are acceptable
• Received prior treatment with cusatuzumab
• Received a live, attenuated vaccine within 4 weeks prior to initiation of study drug

Other illness

• Any active systemic infection

Other

• Presence of the breakpoint cluster region protein-Abelson murine leukemia (bcr-abl) rearrangement

• Diagnosis of de novo or secondary higher-risk Myelodysplastic Syndrome (MDS) or Chronic Myelomonocytic Leukemia (CMML) per World Health Organization (WHO) 2016 criteria
• At study entry, higher-risk MDS (intermediate, high, and very high risk MDS per Revised International Prognostic Scoring System [IPSS R]) OR higher-risk CMML (intermediate-2 or high risk CMML per CMML-specific Prognostic Scoring System [CPSS-Mol]). Participants with previous lower-risk MDS or CMML that has evolved to higher-risk MDS or CMML are eligible
• At study entry, not a candidate for Hematopoietic Stem Cell Transplantation (HSCT)
• Eastern Cooperative Oncology Group (ECOG) performance status score of 0, 1, or 2
• Adequate liver and renal function defined as follows: Aspartate aminotransferase (AST) or alanine aminotransferase (ALT) less than (<) 3 * upper limit of normal (ULN); Total bilirubin less than or equal to (<=) 1.5 * ULN, unless bilirubin rise is due to Gilbert's syndrome or of non hepatic origin; and Creatinine clearance (CrCl) greater than (>) 30 milliliter per minute per 1.73 square meters (mL/min/1.73 m\^2) (by Modification of Diet in Renal Disease formula)