Supplemental Material for: Severe Refractory Immune Effector Cell-Associated Enterocolitis After Ciltacabtagene Autoleucel With Clonal Persistence of CAR-T Construct-Positive T Cells in the Gastrointestinal Tract: A Case Report

Molecular testing detected CAR-T construct transcripts and T-cell clonality, supporting clonal persistence or expansion of CAR-T construct–positive T cells in the gut without definitive evidence of overt CAR-T cell lymphoma. His course was complicated by steroid-refractory enterocolitis, pneumatosis intestinalis, pneumoperitoneum, malnutrition, and need for exploratory laparotomy without gross necrosis or frank perforation.

He required bowel rest, total parenteral nutrition, intravenous immunoglobulin, and multimodal immunosuppression including infliximab, vedolizumab, ruxolitinib, tacrolimus, budesonide, systemic corticosteroids, and cyclophosphamide.</p><p dir="ltr">Conclusion:</p><p dir="ltr">This case highlights severe refractory immune effector cell–associated enterocolitis after ciltacabtagene autoleucel with biopsy-proven clonal persistence of CAR-T construct–positive T cells in gastrointestinal tissue.

Tissue-based CAR-T construct testing and T-cell clonality assessment should be considered in severe or refractory post–CAR-T enterocolitis, particularly when biopsies show atypical T-cell infiltrates.</p>