This study is researching whether the use of tocilizumab before the first dose of linvoseltamab will decrease the risk of Cytokine Release Syndrome (CRS) in participants who have Relapsed or Refractory Multiple Myeloma (RRMM) who have already been treated with at least four lines of treatment for their multiple myeloma, including medicines called a proteasome inhibitor, an immunomodulatory drug, and an anti-Cluster of Differentiation (CD) 38 antibody.

The aim of the study is to see how safe, tolerable and effective linvoseltamab is when given after tocilizumab.

The study is looking at several other research questions, including:

• What side effects may happen from taking tocilizumab before the first dose of linvoseltamab
• Whether tocilizumab has an impact on CRS, including whether participants require hospital care and, if so, how many hospital visits occur and how long they last
• How frequently other medications (for example, corticosteroids or additional doses of tocilizumab) are used to support participants' care if needed

Key Inclusion Criteria:

1. Disease progression on or after at least 4 prior lines of therapy including a(n) Protease Inhibitor (PI), Immunomodulatory imide Drug (IMiD), and anti-CD 38 antibody
2. Eastern Cooperative Oncology Group (ECOG) performance status score ≤2
3. Confirmed progressive disease according to IMWG criteria during or after the most recent line of therapy

Key Exclusion Criteria:

1. Diagnosis of plasma cell leukemia, symptomatic amyloidosis (including myeloma-associated amyloidosis), Waldenström macroglobulinemia (lymphoplasmacytic lymphoma), or Polyneuropathy, Organomegaly, Endocrinopathy, Monoclonal protein, Skin changes (POEMS) syndrome
2. Known myeloma brain lesions or meningeal involvement
3. History of neurodegenerative condition, Progressive Multifocal Leukoencephalopathy [PML], or Central Nervous System (CNS) movement disorder

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