This study is researching an investigational drug called linvoseltamab ("study drug") in participants at moderate risk of developing multiple myeloma (about 3 to 10% average annual risk), a group that consists of patients with precancerous conditions called High-Risk Monoclonal Gammopathy of Undetermined Significance (HR-MGUS) and Non-High-Risk Smoldering Multiple Myeloma (NHR-SMM). The primary purpose of the study is to understand how well the study drug can eliminate abnormal plasma cells and laboratory signs of HR-MGUS and NHR-SMM. The study is looking at several other research questions, including: * How many participants treated with linvoseltamab have improvement of their HR-MGUS or NHR-SMM? * What side effects may happen from taking the study drug? * How much study drug is in the blood at different times? * Whether the body makes antibodies against the study drug (which could make the drug less effective or could lead to side effects).