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)

Inclusion Criteria:

* 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)

Exclusion Criteria:

* 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
* Presence of the breakpoint cluster region protein-Abelson murine leukemia (bcr-abl) rearrangement
* Received a live, attenuated vaccine within 4 weeks prior to initiation of study drug
* Any active systemic infection