A Study Evaluating Venetoclax in Combination With Azacitidine in Subjects With Treatment-Naïve Higher-Risk Myelodysplastic Syndromes (MDS)

Inclusion Criteria:

- Participant must have documented diagnosis of de novo MDS with:

- International Prognostic Scoring System (IPSS) risk categories Int-2 or High
(IPSS overall score ≥ 1.5) and

- Presence of less than 20% bone marrow blasts per bone marrow

- Eastern Cooperative Oncology Group (ECOG) performance score of less than or equal to
2.

- Participant is not a candidate to undergo intensive chemotherapy or allogeneic
hematopoietic stem cell transplantation (HSCT).

Exclusion Criteria:

- Participant has received prior therapy for MDS. (Prior supportive care in form of
transfusions or growth factors, etc., is not considered prior therapy.)

- Participant has received prior therapy with a BH3 mimetic.

- Participant has a diagnosis other than previously untreated de novo MDS with IPSS risk
categories Int-2 or High, including:

- MDS with IPSS risk categories Low or Int-1 (overall IPSS score < 1.5)

- Therapy-related MDS (t-MDS)

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

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

- Participant has received allogeneic HSCT or solid organ transplantation.

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