A Phase II Study of Cladribine and Low Dose Cytarabine in Combination With Venetoclax, Alternating With Azacitidine and Venetoclax, in Patients With Higher-risk Myeloproliferative Chronic Myelomonocytic Leukemia or Higher-risk Myelodysplastic Syndromes With Excess Blasts

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).

Inclusion Criteria: 1. Age \>/= 18 years. 2. Diagnosis of MDS or CMML by WHO and: * 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 * CMML HMA-naïve cohort (Cohort D): CMML-2; OR CMML-1 with at least one of the following high-risk features: extramedullary disease, splenomegaly of \>5cm below costal margin or by sonographic volumetric assessment, platelets \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 * MDS/MPN HMA-naïve cohort (Cohort F): MDS/MPN-NOS or MDS/MPN with neutrophilia (atypical CML) with * \>/=10% blasts or * with \>5% blasts at least one of the following high-risk features: splenomegaly \>5cm below costal margin, WBC \>13x109/L, high risk cytogenetic or molecular features (ASXL1, SETBP1, i(17q), TP53) or * who might not be deemed to benefit from HMA therapy due to proliferative or extramedullary disease. 3. Eastern Cooperative Oncology Group (ECOG) performance status of \ 30 ml/min no end/stage renal disease (using Cockcroft-Gault) 5. Adequate hepatic function with total bilirubin 2x ULN, AST or ALT 2.5 xULN unless deemed to be due to underlying disease involvement. 6. Willing to adhere to and comply with all prohibitions and restrictions specified in the protocol. 7. Patient must have signed an informed consent document indicating that the patient understands the purpose of and procedures required for the study and is willing to participate in the study. 8. English and Non-English speaking patients will be allowed Exclusion Criteria: 1. Uncontrolled infection not adequately responding to appropriate antibiotics 2. New York Heart Association (NYHA) Class III or IV congestive heart failure or LVEF \