Trial in Progress: A Phase 2 Study of Linvoseltamab for the Treatment of High-Risk Smoldering Multiple Myeloma (LINKER-SMM1)

Background and Significance

Smoldering multiple myeloma (SMM) is an asymptomatic clonal plasma cell disorder that precedes the development of multiple myeloma (MM). Traditionally, patients with SMM have undergone observation until progression to MM, but this paradigm can result in poor outcomes for some patients. Phase 3 clinical trials have demonstrated that early treatment with lenalidomide with or without dexamethasone can delay the development of end-organ damage and improve overall survival among SMM patients with high-risk features. Linvoseltamab (REGN5458) is a fully human B-cell maturation antigen (BCMA)×CD3 bispecific antibody that targets BCMA on plasma cells and CD3 on T cells, resulting in targeted T-cell-mediated cytotoxicity. In the Phase 1/2 LINKER-MM1 study, linvoseltamab alone induced deep and durable responses with a generally manageable safety profile in patients with relapsed/refractory MM (Lee et al. EHA. 2023). These data highlight the potential of novel immunotherapies with promising single-agent activity to be attractive therapeutics for early intervention to prevent progression to MM.

Study Design and Methods

LINKER-SMM1 is an open-label, Phase 2 study (NCT05955508) designed to evaluate the safety and efficacy of linvoseltamab monotherapy in adult participants with SMM who are at a high risk of progression to MM. High-risk criteria include having both ≥95% clonal plasma cells in the bone marrow (BM) and immunoparesis and/or ≥2 of the following: serum M-protein >2 g/dL, free light chain ratio >20, and BM plasma cells >20%. Participants must have a confirmed diagnosis of SMM within 5 years of enrollment, Eastern Cooperative Oncology Group performance status ≤1, and adequate organ function to be eligible. Participants will be excluded from enrollment if they have myeloma-defining events, uncontrolled infection, history of allogeneic stem cell transplantation, or received prior treatment for SMM.

The study will take place at approximately 15 sites in Spain and will include two parts: Part 1 (safety run-in) to evaluate the preliminary safety and tolerability of linvoseltamab and Part 2 (expansion) to evaluate the clinical activity of the selected dosing regimen. In Part 1, at least 6 participants will receive linvoseltamab starting with a step-up schedule before reaching the full dose. All subsequent treatment with full-dose linvoseltamab will be given over 28-day cycles until completion of 24 cycles or occurrence of a protocol-defined reason for discontinuation. Assuming that initial safety is shown to be acceptable, an additional 34 participants will be enrolled in Part 2 according to the dosing regimen established in Part 1.

Post-treatment safety monitoring will continue for up to 90 days after the last dose of linvoseltamab, and participants with an ongoing response will continue routine efficacy assessments until confirmed biochemical progression, start of non-protocol cancer therapy, or death. Long-term follow-up will continue for up to 5 years after the last dose of linvoseltamab.

The primary endpoints in Part 1 are frequency of adverse events (AEs) of special interest, including grade ≥2 cytokine release syndrome and immune effector cell-associated neurotoxicity syndrome, and frequency and severity of treatment-emergent AEs. In Part 2, the primary endpoints are complete response (assessed by International Myeloma Working Group criteria) and minimal residual disease (MRD) negativity (10 ^-5 sensitivity) after 12 and 24 months of treatment. Secondary endpoints include cumulative safety, overall response rate, duration of response, sustained MRD negativity, biochemical and clinical progression-free survival (PFS), time to myeloma-defining event, time to initiation of first-line treatment for MM, and overall survival as well as immunogenicity and serum concentration of linvoseltamab over time. Exploratory endpoints include PFS after the start of first-line treatment for MM, adequacy of stem cell collection, patient-reported outcomes, and various biomarker changes. As this is a proof-of-concept study, results will be analyzed using descriptive statistics and no formal hypothesis testing is planned.

Study accrual is planned to begin in Q4 2023.