A Study to Compare Linvoseltamab Monotherapy and Linvoseltamab + Carfilzomib Combination Therapy With Standard-of-Care Combination Regimens in Adult Participants With Relapsed/Refractory Multiple Myeloma (RRMM)

• Linvoseltamab (Drug), also known as REGN5458, Lynozyfic™: Administered per the protocol
• Carfilzomib (Drug), also known as Kyprolis®: Administered per the protocol
• Daratumumab (Drug), also known as Darzalex Faspro®, Darzalex®: Administered per the protocol
• Dexamethasone (Drug), also known as Dexahexal®: Administered per the protocol
• Pomalidomide (Drug), also known as Imnovid®, Pomalyst®: Administered per the protocol
• Bortezomib (Drug), also known as Velcade®: Administered per the protocol

Primary outcomes

• Occurrence of Treatment Emergent Adverse Events (TEAEs) [Up to 5 years]: Part 1
• Severity of TEAEs [Up to 5 years]: Part 1
• Occurrence of Adverse Events of Special Interest (AESI) [Up to 5 years]: Part 1
• Severity of AESIs [Up to 5 years]: Part 1
• Occurrence of Serious Adverse Events (SAEs) [Up to 5 years]: Part 1
• Severity of SAEs [Up to 5 years]: Part 1
• Minimal Residual Disease (MRD)-negative Complete Response (CR) [At 12 months]: Part 2
• Progression-Free Survival (PFS) per IMWG response criteria as determined by BIRC [Up to 5 years]: Part 2

Secondary outcomes

• Occurrence of grade ≥2 Cytokine Release Syndrome (CRS) [Up to 28 days]: Part 1
• Timing of grade ≥2 CRS [Up to 28 days]: Part 1
• Overall Survival (OS) [Up to 7 years]: Part 2
• Achievement of Partial Response (PR) or better per IMWG response criteria as determined by BIRC [Up to 5 years]: Part 2
• Achievement of Very Good Partial Response (VGPR) or better per IMWG response criteria as determined by BIRC [Up to 5 years]: Part 2
• Achievement of CR or better per IMWG response criteria as determined by BIRC [Up to 5 years]: Part 2
• Duration Of Response (DOR) as per IMWG response criteria [Up to 5 years]: Part 2
• Time To Progression (TTP) as per IMWG response criteria [Up to 5 years]: Part 2
• Time To Next Treatment (TTNT) [Up to 5 years]: Part 2
• Second PFS [Up to 5 years]: Part 2
• MRD-negative CR criteria at any time [Up to 5 years]: Part 2
• Time to PR IMWG response category [Up to 5 years]: Part 2
• Time to VGPR IMWG response category [Up to 5 years]: Part 2
• Time to CR IMWG response category [Up to 5 years]: Part 2
• Time to stringent Complete Response (sCR) IMWG response category [Up to 5 years]: Part 2
• Sustained MRD-negative CR [Up to 5 years]: Part 2
• Duration of MRD-negative CR [Up to 5 years]: Part 2
• Occurrence of TEAEs [Up to 5 years]: Part 2
• Severity of TEAEs [Up to 5 years]: Part 2
• Occurrence of AESIs [Up to 5 years]: Part 2
• Severity of AESIs [Up to 5 years]: Part 2
• Occurrence of SAEs [Up to 5 years]: Part 2
• Severity of SAEs [Up to 5 years]: Part 2
• Concentrations of linvoseltamab in serum over time [Up to 5 years]: Part 2
• Incidence of Antidrug Antibodies (ADAs) to linvoseltamab [Up to 5 years]: Part 2
• Magnitude of ADAs to linvoseltamab [Up to 5 years]: Part 2
• Concentrations total soluble B-cell Maturation Antigen (sBCMA) in serum over time [Up to 5 years]: Part 2
• Change from baseline in Global Health Status (GHS)/Quality of Life (QoL), per European Organization for Research and Treatment of Cancer Quality of Life Questionnaire (EORTC QLQ-C30) [Up to 5 years]: Part 2 The EORTC QLQ-C30 is a 30-item validated questionnaire developed to measure patient-reported QoL using 1 GHS/QoL scale, 5 functioning scales (physical, role, emotional, cognitive and social) and 9 symptom scales / items (fatigue, nausea/vomiting, pain, dyspnea, insomnia, appetite loss, constipation, diarrhea and financial difficulties) among patients with cancer. Participants rate items on a 4-point scale, with 1 as "not at all" and 4 as "very much."
• Change from baseline in Physical Functioning (PF), per EORTC QLQ-C30 [Up to 5 years]: Part 2
• Change from baseline in Role Functioning (RF), per EORTC QLQ-C30 [Up to 5 years]: Part 2
• Change from baseline in pain, per EORTC QLQ-C30 [Up to 5 years]: Part 2
• Change from baseline in fatigue, per EORTC QLQ-C30 [Up to 5 years]: Part 2
• Change in patient reported Disease Symptoms (DS) per EORTC Quality of Life Questionnaire-Multiple Myeloma (MM) module 20 [QLQ-MY20]) [Up to 5 years]: Part 2 EORTC QLQ-MY20 is an accompanying 20-item validated questionnaire that measure quality of life among patients living with MM across 4 scales (disease symptoms, side effect of treatment, body image and future perspective). A high score represents a high level of symptoms or problems.
• Change in patient reported Treatment Side Effects (TSE) per EORTC QLQ-MY20 [Up to 5 years]: Part 2
• Change in patient-reported health state per EuroQoL-5 Dimension-5 Level Scale [EQ-5D-5L]) Visual Analogue Scale (VAS) [Up to 5 years]: Part 2 The EQ-5D-5L is a generic questionnaire that measures HRQoL across 5 dimensions of health (mobility, self-care, usual activities, pain/discomfort and anxiety/depression) across 5 levels (no problems, slight problems, some problems, severe problems and extreme problems) and a VAS of pain (where 0: no pain and 10: worst pain), higher scores indicate higher pain.
• Change in patient-reported overall impact of treatment per Functional Assessment of Chronic Illness Therapy (FACIT) item GP5 [Up to 5 years]: Part 2 FACIT Item GP5 is a recommended item by the Federal Drug Administration (FDA) in its recent draft guidance for cancer trials to assess patient-reported overall impact of treatment toxicity. It uses a single item "I am bothered by side effects of treatment" on a 5-point scale (0= not at all, 1= a little bit, 2= somewhat, 3= quite a bit, 4= very much)

Sex: All, ages: 18 Years to any

Key Inclusion Criteria:

1. Participant with RRMM who received at least 1 but not more than 3 prior lines of therapy, which must have included treatment with lenalidomide and either a Protease Inhibitor (PI) or anti-CD38 monoclonal 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. Prior treatment with a T cell-based immunotherapy targeting BCMA, including BCMA-directed bispecific antibodies, Bispecific T-cell Engagers (BiTEs), and Chimeric Antigen Receptor (CAR) T cells. Antibody-drug conjugates targeting BCMA (eg, belantamab mafodotin) are not excluded
2. Diagnosis of plasma cell leukemia, symptomatic amyloidosis (including myeloma-associated amyloidosis), Waldenström macroglobulinemia (lymphoplasmacytic lymphoma), or POEMS syndrome (polyneuropathy, organomegaly, endocrinopathy, monoclonal protein, and skin changes)
3. Known Central Nervous System (CNS) involvement of myeloma including meningeal involvement
4. History of neurodegenerative condition, Progressive Multifocal Leukoencephalopathy (PML), or CNS movement disorder

NOTE: Other protocol defined inclusion/exclusion criteria apply

• Clinical Trial Management, Study director, Regeneron Pharmaceuticals