Fernandez‐Pol, Sebastian

Abstract Chimeric antigen receptor (CAR) T-cell therapy has emerged as a transformative treatment for hematological malignancies, yet its potential to drive lymphomagenesis poses significant clinical concerns. In this study, we investigated the mechanisms underlying CAR T-cell–associated lymphomagenesis in the gastrointestinal (GI) tract on a single case, focusing specifically on the role of integrin α4β7 expression and a predisposing somatic SH2B3 mutation. We observed oligoclonal CAR T cells homing to, and clonally expanding in, the GI tract, with the dominant expanded clone harboring both a pathogenic SH2B3 mutation and a CAR transgene integration within a TFCP2 locus. The clonal CAR T cells subsequently transitioned beyond the GI tract into the peripheral blood, suggesting a potential pathway for systemic dissemination. We found clinical, histological, and molecular evidence demonstrating the efficacy of cyclosporine in reducing the expanded malignant clone and achieving durable clinical remission for more than a year. Our findings highlight the complex interplay between CAR T-cell therapy, preexisting genetic vulnerabilities, and the GI microenvironment, emphasizing the need for vigilant monitoring and tailored therapeutic strategies to address the risks associated with CAR T-cell lymphomagenesis.

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.