Safety and Tolerability of REGN17235 in Adult Participants With Clonal Cytopenia of Undetermined Significance and Low-Risk Myelodysplastic Syndrome With SF3B1 Mutation

This study will test a study drug called REGN17235 (the "study drug") to see if it can help treat Clonal Cytopenia of Undetermined Significance (CCUS) and Low-Risk Myelodysplastic Syndrome (LR-MDS) with a specific genetic mutation (SF3B1 Mutation). The study is looking at: * What side effects the study drug might cause * How well the study drug works * How much of the study drug is in the blood at different times * If the body makes antibodies (proteins that attach to substances your body does not recognize) against the study drug; this may cause the study drug to not work as well. * What is the best dose of the study drug to treat CCUS and LR-MDS

Key Inclusion Criteria: 1. Presence of SF3B1 mutation in the bone marrow or peripheral blood AND diagnosis of low-risk MDS OR diagnosis of CCUS as defined by WHO 2022, 5th edition as described in the protocol 2. Adequate bone marrow function as described in the protocol; red blood cell transfusion dependence is permitted 3. Adequate hepatic and renal function as described in the protocol Key Exclusion Criteria: 1. Clinically significant anemia due to non-MDS or non-CCUS etiologies (eg, iron deficiency, vitamin B12 or folate deficiency, autoimmune or hereditary hemolysis, or hemorrhage) diagnosed or treated within the last 3 months prior to informed consent 2. Recent or uncontrolled infections as described in the protocol 3. Diagnosed or treated for malignancy other than MDS as described in the protocol 4. Prior treatment with any systemic therapy for MDS or CCUS within 5 half-lives or within 14 days prior to first administration of study drug, whichever is shorter 5. Allogeneic hematopoietic stem cell transplant within 100 days of enrollment or any signs or symptoms of ongoing Graft-Versus Host Disease (GVHD) as described in the protocol Note: Other protocol defined Inclusion/Exclusion Criteria apply