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

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing.

When Regeneron has:

• received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development
• made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry)
• the legal authority to share the data, and
• ensured the ability to protect participant privacy

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf