Low-Risk Myelodysplastic Syndrome (LR-MDS)

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