Abstract Topic: 14. Myeloma and other monoclonal gammopathies - Clinical
Background: Tec is the first BCMA-directed bispecific antibody approved for the treatment of triple-class exposed RRMM. Tal, a bispecific antibody targeting the novel myeloma antigen GPRC5D, has shown promising efficacy in pts with RRMM. Simultaneously targeting 2 validated myeloma target antigens, using tec + tal in combination may lead to improved outcomes by overcoming resistance mechanisms, such as antigen escape.
Aims: We report the first results from the phase 1b RedirecTT-1 trial (NCT04586426) in pts with RRMM.
Methods: Enrolled pts had MM per International Myeloma Working Group 2016 criteria; were RR or intolerant to the last line of therapy (LOT); were exposed to a proteasome inhibitor, immunomodulatory drug, and anti-CD38 therapy; and had measurable disease. All pts provided informed consent. The primary objectives are to evaluate safety and to identify a recommended phase 2 regimen (RP2R) for the combination. Responses were investigator assessed. AEs were graded per CTCAE v5.0. Cytokine release syndrome (CRS) and immune effector cell-associated neurotoxicity syndrome (ICANS) were graded per ASTCT criteria.
Results: As of Dec 12, 2022, 63 pts received tec + tal. Median (range) age was 67 y (39–81); median (range) prior LOT was 5 (1–11); 33% (15/45) had high-risk cytogenetics; 78% (49/63) were triple-class refractory; 63% (40/63) were penta-drug exposed; and 43% (27/63) had extramedullary disease (EMD; all bone independent). Median (range) duration of follow-up was 14.4 mos (0.5–21.9). The most common treatment-emergent AEs were CRS (81%; grade [gr] 3, 3%, no gr 4), neutropenia (76%; gr 3/4, 75%), and anemia (60%; gr 3/4, 43%). Dose-limiting toxicities (DLTs) were reported at dose level 1 (gr 3 herpetic stomatitis) and dose level 3 (gr 3 AST/ALT elevation). One ICANS event was reported at dose level 3. No DLTs were reported at the RP2R. Across all dose levels, overall response rate (ORR) was 84% (52/62) among all evaluable pts and 73% (19/26) among evaluable pts with EMD; rate of CR or better (≥CR) was 34% (21/62) and 31% (8/26), respectively. At the RP2R, ORR was 92% (12/13) among all evaluable pts and 83% (5/6) among evaluable pts with EMD; rate of ≥CR was 31% (4/13) and 33% (2/6), respectively. Median duration of response has not been reached. Updated data, with 19 additional pts at the RP2R, will be presented.
Summary/Conclusion: In this first combination study of a BCMA- and GPRC5D-targeted bispecific antibody, tec + tal at the RP2R has a manageable safety profile consistent with each of the monotherapies. A 92% ORR was observed in pts with advanced RRMM at the RP2R and an ORR of 83% was achieved in pts with EMD, a high-risk population with unmet need, supporting further evaluation of the combination. © 2023 American Society of Clinical Oncology, Inc. Reused with permission. This abstract was accepted and previously presented at the 2023 ASCO Annual Meeting. All rights reserved.
Keywords: Multiple myeloma, Phase I, Bispecific, B-cell maturation antigen