Abstract CT001: Linvoseltamab, a B-cell maturation antigen-targeted T-cell-engaging bispecific antibody, induces deep and durable responses in patients with relapsed or refractory multiple myeloma including difficult-to-treat subgroups

Abstract

Background We report pivotal results from the registrational filing data cut-off (DCO) of the 200 mg dose used in the LINKER-MM1 (NCT03761108) clinical trial, testing the safety and efficacy of linvoseltamab (a B-cell maturation antigen × CD3 antibody [Ab]) as treatment for relapsed/refractory multiple myeloma (RRMM). Methods Eligible patients had RRMM that either progressed on/after ≥3 lines of therapy that included a proteasome inhibitor (PI), an immunomodulatory drug (IMiD), and an anti-CD38 Ab or that was ≥double- (Phase 1) or triple- (Phase 2) class (PI/IMiD/anti-CD38 Ab) refractory. Phase 2 patients received intravenous linvoseltamab once a week through week 14, then once every 2 weeks (Q2W). Phase 2 patients achieving ≥very good partial response (VGPR) who have received treatment for ≥24 weeks transitioned to Q4W dosing. Primary endpoint was objective response rate (ORR) per Independent Review Committee (IRC). Secondary endpoints included duration of response (DOR), progression free survival (PFS), overall survival (OS), and safety. Results At DCO of Sep 8, 2023, median duration of follow-up for the 117 patients enrolled into the 200 mg dosing cohorts (phase 1+2) was 11.1 months (interquartile range 2.9-14.1). Median age was 70 years (26% ≥75), 17% were African American, 18% had International Staging System (ISS) stage III disease, 16% had extramedullary (excluding paramedullary) plasmacytomas (EMPs) ≥2 cm, 39% had high-risk cytogenetics, and 82% were ≥triple-class refractory. Linvoseltamab induced high rates of deep responses with an ORR of 71% including ≥complete response (CR) rate of 46%. Among all patients with ≥CR, 39% were documented minimal residual disease negative. These frequent and deep responses were observed across prespecified high-risk subgroups including patients with ISS stage III (ORR 62%; ≥CR 43%), and EMPs (ORR 53%; ≥CR 26%). Kaplan-Meier (KM) estimated median DOR was not reached (NR); estimated probability of ongoing response at 12 months was 78% (95% confidence interval [CI] 65-86). KM estimated PFS and OS were NR; and probability of PFS and OS at 12 months were 69% (95% CI 58-77) and 75% (65-82), respectively. The most common treatment emergent adverse event (TEAE) was cytokine release syndrome (CRS; any grade [Gr] 46%, Gr2 10%, Gr3 1%, Gr≥4 0%), which occurred mostly during step-up dosing of linvoseltamab with a median time to onset of 11 hours. Other common TEAEs were neutropenia (any Gr 41%, Gr 3-4 40%), anemia (39%, 31%), cough (36%, 0%), and diarrhea (35%, 2%). Infections occurred in 73% (Gr 3-4 34%) of patients. The frequency and severity of infections decreased after 6 months coincident with Q4W dosing. Conclusions Linvoseltamab induced high rates of deep and durable responses in patients with RRMM including those in high-risk subgroups. Linvoseltamab is associated with a generally predictable timing of CRS, and the Q4W response adapted schedule in patients with ≥VGPR may provide a substantial benefit for patient convenience and is associated with a reduced infection rate. Citation Format: Sundar Jagannath, Joshua Richter, Madhav V. Dhodapkar, James E. Hoffman, Hans C. Lee, Attaya Suvannasankha, Mansi R. Shah, Suzanne Lentzsch, Jeffrey A. Zonder, Rachid Baz, Joseph J. Maly, Swathi Namburi, Ka Lung Wu, Matthew Pianko, Rebecca Silbermann, Chang-Ki Min, Marie-Christiane Vekemans, Markus Munder, Ja Min Byun, Joaquín Martínez Lopez, Michelle DeVeaux, Dhruti Chokshi, Anita Boyapati, Anasuya Hazra, Karen Rodriguez Lorenc, Glenn S. Kroog, Yariv Houvras, Naresh Bumma. Linvoseltamab, a B-cell maturation antigen-targeted T-cell-engaging bispecific antibody, induces deep and durable responses in patients with relapsed or refractory multiple myeloma including difficult-to-treat subgroups [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr CT001.