As a marker of minimal residual disease in B-cell acute lymphoblastic leukemia (B-ALL), CD58 has been reported in B-ALL at diagnosis and short-term follow-ups after standard chemotherapies. However, there are no data available in relapsed/refractory (r/r) patients who have received long-term and multiline therapies, especially chimeric antigen receptor (CAR) T cells; here, we focused on investigating CD58 status in these patients.
CD58 expression on lymphoblasts was detected by multiparameter flow cytometry. CD58 status was evaluated in patients with r/r B-ALL before CAR-T therapy, and the patients who failed or relapsed after CAR-T.
Among 274 pediatric and adult patients prior to exposure to CAR-T cells (22.3% of them underwent allogeneic hematopoietic cell transplantation, allo-HCT), 228 (83.2%) showed CD58 positivity. Furthermore, among 58 patients who were CD58 positive before CAR-T failed or relapsed after CAR-T (half also received CD22 CAR-T or allo-HCT as a consolidation treatment following CD19 CAR-T), the frequency of CD58 expression was 79.3% (46/58) in all patients and 86.2% (25/29) in patients exposed to CD19 CAR-T cells alone.
CD58 antigen was stably expressed in patients with r/r B-ALL after multiline therapies, including allo-HCT and CAR-T, indicating that it could still be a leukemic marker in heavily treated patients.

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