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1986 Debulking Conventional Chemotherapy before Treatment By Anti-BCMA Bispecific Antibody in Extramedullary and/or High Tumor Burden Relapsed/Refractory Multiple Myeloma

Program: Oral and Poster Abstracts
Session: 654. Multiple Myeloma: Pharmacologic Therapies: Poster I
Hematology Disease Topics & Pathways:
Adult, Clinical Practice (Health Services and Quality), Plasma Cell Disorders, Therapy sequence, Diseases, Treatment Considerations, Lymphoid Malignancies, Human, Study Population
Saturday, December 7, 2024, 5:30 PM-7:30 PM

Thomas Chalopin, MD1*, Hélène Demarquette2*, Andrea Pieragostini3*, Cécile Sonntag, MD4*, Caroline Jacquet, MD5*, Zoe van De Wyngaert, MD6*, Anne Rumpler7*, Murielle Roussel, MD8*, Gaelle Labouré9*, Veronique Morel, MD10*, Laure Vincent, MD11*, Valéry Salle12*, Elise Cellerin13*, Titouan Cazaubiel14* and Salomon Manier, MD, PhD15

1Centre Hospitalier Universitaire de Tours, Tours, France
2CH Dunkerque, Dunkerque, France
3Hematology, CHU Dijon, Dijon, France
4Centre Hospitalier Universitaire Hautepierre, Strasbourg, FRA
5CHU de Nancy, Vandoeuvre Les Nancy, FRA
6Department of Clinical Hematology and Cellular Therapy, Sorbonne University, Saint Antoine Hospital, Assistance Publique - Hôpitaux de Paris, Paris, France
7CHU de Besançon, Besançon, France
8Hématologie Clinqiue, CHU de Limoges, Limoges Cedex 1, FRA
9Centre Hospitalier Robert Boulin, Libourne, France
10Clinical Hematology, Pitie-Salpetriere Hospital, APHP, Sorbonne Universite, Paris Cedex 13, FRA
11Department of Clinical Hematology, Hôpital St Eloi, CHU de Montpellier, Montpellier, France
12CHU d’Amiens, Amiens, FRA
13Centre Hospitalier Universitaire de Tours, Tours, AL, France
14CHU De Bordeaux, Bordeaux, FRA
15Centre Hospitalier Universitaire - Hôpital Huriez, Lille, France

Background. New immunotherapies have improved response rates and survival in relapse/refractory multiple myeloma (RRMM) setting. However, patients with extramedullary disease (EMD) and/or high tumor burden continue to have poor response rates and inferior survival, representing an unmet medical need. Currently, there are no recommended strategies to enhance the efficacy anti-BCMA bispecific antibodies (BsAb) for these patients. In this study, we aim to evaluate the efficacy and tolerability of conventional chemotherapy as a debulking strategy prior to the administration of anti-BCMA BsAb in patients with EMD and/or high tumor burden with RRMM.

Methods. We conducted a retrospective study across 15 IFM centers, including patients with RRMM treated with anti-BCMA BsAb between March 2022 and May 2023. Patients received chemotherapy in the month prior BsAbs administration. EMD was defined as a lesion restricted to soft tissue without contact with bony structures. High tumor-burden was based on medullary plasma cell infiltration, para-medullary disease and/or high levels of monoclonal component. High-risk cytogenetic status was defined by presence of 17p deletion, t(4;14) and t(14;16). Patients with plasma-cell leukemia were excluded.

Results. In total, 36 patients were included with median age of 68 years (range: 52-84), and 49% were female. Among them, 97% (n=35) were triple-class refractory, 53% (n=19) had EMD, 33% (n=12) had high-risk cytogenetic abnormalities with 42% of 17p deletion (n=8). Eighteen (50%) had an ISS score of 3, 38% (n=11) and 40% (n=14) had elevated levels of LDH and B2m, respectively.

Regarding debulking chemotherapy, 92% (n=33) received alkylating agents, including cyclophosphamide (89%, n=32) and belustine (14%, n=5), 42% (n=15) received anthracyclines, 56% (n=20) received etoposide, 11% (n=4) received vincristine, and 14% (n=5) received cisplatin. Twenty-five patients (69%) received one cycle. Teclistamab was used in 29 patients (81%) and elranatamab in 7 patients (19%) with a median interval between chemotherapy and BsAb administration of 36 days (range: 4-197). CRS rate was 67% with one grade 3 (4.2%) and ICANS rate was 8.3% with one grade 4. Tocilizumab was used in 7 patients (19%) and dexamethasone in 4 patients (11%). Cytopenia grade≥3 occurred in 31% (n=11) and infections in 40% (n=14).

With a median follow-up of 11 months (range: 1-28), the overall response rate (ORR) after cycle 1 of BsAb was 63% with 37% of complete response (CR) and 49% of very good partial response (VGRP) or better. After cycle 3, the ORR was 74%, 88% at cycle 6 and 75% at one year. Median progression-free survival (PFS) was 9.4 months (95%CI: 4.11-18.1). Death occurred in 15 patients (42%), ten due to disease progression, 3 to infection and 2 others causes.

Conclusion. This study confirms the feasibility of debulking chemotherapy before use of an anti-BCMA BsAb in a high-risk population. We reported a high response rate and a PFS comparable to the overall population receiving BsAb. This strategy can be used in a challenging population to improve response to novel immunotherapy.

Disclosures: van De Wyngaert: Janssen-Cilag, BMS, Sanofi: Honoraria. Roussel: Pfizer: Honoraria, Other: meeting fees and travel grants; janssen: Other: meeting fees and travel grants; GSK: Other: travel grants; sanofi: Research Funding; bms: Research Funding. Vincent: Janssen: Membership on an entity's Board of Directors or advisory committees, Other: Financing access to congress; BMS: Membership on an entity's Board of Directors or advisory committees, Other: Financing access to congress; Takeda: Membership on an entity's Board of Directors or advisory committees, Other: Financing access to congress; Sanofi: Membership on an entity's Board of Directors or advisory committees, Other: Financing access to congress; Pfizer: Other: Financing access to congress. Manier: GlaxoSmithKline: Consultancy; Janssen: Consultancy; Novartis: Consultancy; Regeneron: Consultancy; Roche: Consultancy; Sanofi: Consultancy; Takeda: Consultancy; Celgene/BMS: Consultancy; Amgen: Consultancy; Adaptive Biotechnology: Consultancy; Abbvie: Consultancy.

*signifies non-member of ASH