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