∙ 1\. Patients must be ≥ 18 years of age at the time of signing the informed consent form (ICF) 2. The Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤ 2 3. Patient must be a candidate for serial bone marrow aspirate and/or biopsy according to the institutions guidelines and must be willing to undergo a bone marrow aspirate.

∙ 4\. Patients must have one of the following for eligibility into the study:

• In dose optimization: IPSS-R defined very low, low or intermediate risk Myelodysplastic Syndrome (LR MDS) who failed to respond to or did not tolerate ESAs or luspatercept or HMAs and patients with del 5q who failed to respond to or did not tolerate lenalidomide; or

• In dose optimization and expansion: IPSS-R defined very low, low or intermediate risk Chronic Myelomonocytic Leukemia (LR CMML) who failed to respond to or did not tolerate hydroxyurea or HMAs.

• changes for dose expansion (applicable as of amendment 3):

‣ LR MDS with ≤ 10% bone marrow blasts, IPSS-R score of ≤ 3.5, transfusion independent (TID) status as per IWG 2006 criteria (requiring \<4U pRBC in 8 weeks), clinically meaningful cytopenia(s) and no or limited (\<4 months) prior therapy for MDS.

⁃ LR CMML patients with symptomatic cytopenias and/or constitutional symptoms refractory, intolerant or unsuitable for standard first-line therapy.

⁃ HR-CCUS: Diagnosis of high-risk CCUS by clonal hematopoiesis risk score (CHRS) with clinically meaningful cytopenias and no prior therapy for a myeloid neoplasm.