Inclusion Criteria:

          -  Subjects who have relapsed or refractory MDS.

          -  Subject enrolled in venetoclax monotherapy must have documented failure of prior
             therapy with a hypomethylating agent (HMA). HMA-failure is defined as:

               1. Relapse after initial complete or partial response or hematological improvement
                  after at least 4 cycles of azacitidine or at least 4 cycles of decitabine within
                  the last 5 years, OR

               2. Failure to achieve complete or partial response or hematological improvement
                  after at least 4 cycles of azacitidine or at least 4 cycles of decitabine within
                  the last 5 years

          -  Subjects must have presence of < 20% bone marrow blasts per bone marrow
             biopsy/aspirate at screening.

          -  Subject is not a candidate to undergo allogenic hematopoietic stem cell
             transplantation (HSCT).

          -  Subject must have an Eastern Cooperative Oncology Group (ECOG) performance score of
             ≤2.

          -  Subject must have adequate hematologic, renal, and hepatic function.

        Exclusion Criteria:

          -  Subject has received prior therapy with a BH3 mimetic.

          -  Subject has MDS evolving from a pre-existing myeloproliferative neoplasm (MPN).

          -  Subject has MDS/MPN including chronic myelomonocytic leukemia (CMML), atypical chronic
             myeloid leukemia (CML), juvenile myelomonocytic leukemia (JMML) and unclassifiable
             MDS/MPN.

          -  Subject has received allogeneic HSCT or solid organ transplantation.

          -  Subject has received a live attenuated vaccine within 4 weeks prior to the first dose
             of study drug.

          -  Subject is pregnant or breastfeeding.