A Proof-of-Concept Study to Learn Whether Linvoseltamab Can Eliminate Abnormal Plasma Cells That May Lead to Multiple Myeloma in Adult Patients With High-Risk Monoclonal Gammopathy of Undetermined Significance or Non-High-Risk Smoldering Multiple Myeloma

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).

Key Inclusion Criteria: 1. HR-MGUS or NHR-SMM as defined in the protocol 2. Eastern Cooperative Oncology Group (ECOG) performance status ≤1 3. Adequate hematologic and hepatic function, as described in the protocol 4. Estimated glomerular filtration rate (GFR) ≥30 mL/min/1.73 m\^2 by the Modification of Diet in Renal Disease (MDRD) equation Key Exclusion Criteria: 1. High-risk SMM, as defined in the protocol 2. Evidence of any of myeloma-defining events, as described in the protocol 3. Diagnosis of systemic light-chain amyloidosis, Waldenström macroglobulinemia (lymphoplasmacytic lymphoma), solitary plasmacytoma, or symptomatic MM 4. Clinically significant cardiac or vascular disease within 3 months of study enrollment, as described in the protocol 5. Any infection requiring hospitalization or treatment with intravenous (IV) anti-infectives within 28 days of the first dose of linvoseltamab 6. Uncontrolled Human Immunodeficiency Virus (HIV), Hepatitis B Virus (HBV), or Hepatitis C Virus (HCV) infection; or other uncontrolled infection or unexplained signs of infection, as described in the protocol NOTE: Other protocol defined inclusion/exclusion criteria apply