To learn if the combination of cladribine, cytarabine, venetoclax, and azacitidine can help to control higher-risk myelodysplastic syndrome (MDS) with excess blasts and/or higher-risk chronic myelomonocytic leukemia (CMML).
Age >/= 18 years.
MDS relapsed cohort (Cohort A): MDS with IPSS-R score >3.5 and >5% blasts with no response after 6 cycles of azacitidine, decitabine, guadecitabine or ASTX727 (decitabine/cedazuridine) or relapse or progression after any number of cycles
CMML relapsed cohort (Cohort B): CMML 1 or 2 with no response after 6 cycles of azacitidine, decitabine, guadecitabine or ASTX727 (decitabine/cedazuridine) or relapse or progression after any number of cycles
MDS HMA-naïve cohort (Cohort C): MDS with IPSS-R score >3.5 and >/= 10% blasts
Uncontrolled infection not adequately responding to appropriate antibiotics
New York Heart Association (NYHA) Class III or IV congestive heart failure or LVEF <50% by echocardiogram or multigated acquisition (MUGA) scan.
History of myocardial infarction within the last 6 months or unstable/uncontrolled angina pectoris or history of severe and/or uncontrolled ventricular arrhythmias.
Female patients who are pregnant or lactating.