Banerjee, Rahul

Introduction: Anti-BCMA CAR-T therapies like idecabtagene vicleucel (ide-cel) and ciltacabtagene autoleucel (cilta-cel) have revolutionized RRMM treatment. However, the 6-8-week manufacturing period often leads to disease progression and/or death in up to 25% of patients (pts), necessitating effective bridging strategies. Talquetamab (talq), a bispecific antibody targeting GPRC5D, is approved for RRMM pts with four prior lines of therapy and offers rapid disease debulking without impacting BCMA. This study assesses the safety and efficacy of a short course of talq as a bridging therapy for pts receiving cilta-cel or ide-cel. Methods: This multicenter retrospective study involved 14 US academic medical centers within the US Multiple Myeloma Immunotherapy Consortium. We included pts with RRMM who underwent leukapheresis and received talq bridging therapy with the intent to proceed to commercial cilta-cel or ide-cel. We assessed the safety, feasibility, and efficacy of talq bridging therapy. Safety outcomes included cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), talq-related unique toxicities, and delayed neurotoxicity (NT). Efficacy outcomes included response rates to talq and CAR-T therapies. Results: Between June 2023 and May 2024, 77 pts received talq bridging therapy after apheresis with the intention to proceed to CAR-T. The median age was 66 years (range, 58-73); 14% were Black and 10% Hispanic. Poor prognostic features, including high-risk cytogenetics, were present in 45%, extramedullary disease (EMD) in 43%, and 72.7% were triple-class refractory. The median number of prior lines of therapy was 5 (range 3-11) and 10 pts (13%) had prior BCMA targeted therapy. Out of 77 pts, 10 pts were pending CAR-T infusion at the time of last follow up; 6 pts could not receive CAR-T infusion due to manufacturing failures. Of the remaining 61 patients who underwent successful CAR-T manufacturing, 58 (95%) pts were successfully infused with CAR-T therapy following talq bridging. Three (5%) pts died due to disease progression prior to CAR-T infusion. Talq was given 0.8 mg/kg biweekly in 59 (76%) pts and the median time on talq was 22 days (IQR: 10-41 days). Following talq bridging, none of the pts had grade >=3 CRS and 2 (2.5%) had grade 3 ICANS. Skin toxicities occurred in 32 (41%), nail toxicities in 19 (25%), and oral toxicities in 43 (56%) pts mainly grade 1. Most oral, skin, and taste changes resolved at the last follow-up (60%). Response to talq was evaluable in 72 out of 77 patients. An overall response was noted in 45/72 (62%) pts including unconfirmed CR in 14, VGPR in 10 and PR in 21 pts. There was no association of AEs and response to talq with high-risk cytogenetics, EMD and high baseline ferritin levels. Out of the 58 patients who went on to receive CAR-T therapy following talq bridging (45 cilta-cel and 13 ide-cel), 38 (65%) experienced CRS, with grade 3 CRS noted in 2 (3%) pts. ICANS occurred in 5 (8.6%) pts, with 1 (1.7%) grade 3 ICANS. Only 1 pt had delayed NT (facial nerve palsy) at the last follow up. No treatment related deaths were observed. Of these 58 pts, response was evaluable in 40 pts and a response at day +30 was noted in 39/40 (97.5%) pts (14 in CR, 10 in VGPR, 15 in PR). The median follow-up from CAR-T was 61 days (28-113). For the 58 pts who received CAR-T, the median time from the last talq dose to CAR-T infusion was 25 days (IQR: 19-36), and to lymphodepletion was 24 days (IQR: 18-33). There was no difference in the CAR-T related AEs by the duration of Talq washout (>4 weeks vs. =< 4 weeks). Conclusions: Talquetamab is an excellent bridging option before BCMA-targeted CAR-T therapy, showing high response rates even with short-term use and enabling most pts to receive CAR-T. Most oral, skin, and taste changes resolved post CAR-T. These findings underscore the effectiveness of a short course of talq bridging to maintain disease control and improve outcomes post CAR-T. Updated data with longer follow-up will be presented at the meeting.

Abstract Background: Several immune effector cell (IEC) therapies have been approved for multiple myeloma (MM), including chimeric antigen receptor T-cell (CAR-T) therapies such as idecabtagene vicleucel (ide-cel) and ciltacabtagene autoleucel (cilta-cel). We report 14 cases of IEC-associated enterocolitis, in five cases fatal, following CAR-T therapy in MM. Methods: We performed a retrospective analysis of cases of diarrhea, enterocolitis, or colitis following commercial ide-cel or cilta-cel (including out-of-specification products) at 10 centers within the United States Myeloma Immunotherapy Consortium. Patients were treated according to the local standard of care at each participating center. Results: We identified 14 cases of IEC-associated enterocolitis out of 1159 CAR-T infusions, corresponding to a 1.2% incidence (0.2% for ide-cel and 2.3% for cilta-cel). This proportion excludes 3 cases of potential or confirmed T-cell lymphoproliferative disorders of the bowel. Patients developed acute-onset symptoms (typically non-bloody Grade 3+ diarrhea) with negative infectious workup beginning a median of 79 days (range: 22-210 days) after CAR-T therapy and a median of 74 days after cytokine release syndrome resolution (range: 2-202 days). Biopsies uniformly demonstrated inflammation, with specific findings including intra-epithelial lymphocytosis, crypt dropout on colon biopsies, and villous blunting on duodenal biopsies. Systemic corticosteroids were initiated in 10 patients (71%) a median of 26 days (range: 1-80 days) following symptom onset. Only 40% of steroid-treated patients had symptomatic improvement; subsequent infliximab or vedolizumab led to improvement in 50% and 33% of corticosteroid-refractory patients, respectively. With a median follow-up of 224 days, n = 4 have had diarrhea resolution, n = 5 have had improved or stable symptoms, and n = 5 (36%) have died from IEC-associated enterocolitis or treatment-emergent infections. Conclusions: IEC-associated enterocolitis is a distinct but rare complication of CAR-T therapy characterized by non-bloody diarrhea typically beginning 1-3 months after infusion. Thorough diagnostic workup (including evaluation for potential T-cell malignancies) and appropriate management with an expert gastroenterologist are essential. Further research is critical to understand the pathogenesis of this novel toxicity. In the interim, the early use of infliximab or vedolizumab may potentially hasten symptom resolution and lower reliance on high-dose corticosteroids during the post-CAR-T period.