CD19 CAR T-Cell Therapy in Refractory Autoimmune Hemolytic Anemia

CD19 chimeric antigen receptor (CAR) T-cell therapy emerged as a novel treatment in autoimmune diseases. Refractory autoimmune hemolytic anemia (rAIHA) is characterized by life-threatening hemolysis, and traditional B-cell-targeting treatments often fail to halt the disease. We hypothesize that resetting aberrant autoimmunity through deep depletion of B cells by CD19 CAR T-cell could be a potential strategy for rAIHA to achieve sustained drug-free remission (DFR).

Refractory AIHA patients who had failed at least three lines of therapies were enrolled in a compassionate-use CD19 CAR T-cell program (n = 5) and phase I clinical trial (NCT06231368) (n = 3) to evaluate the safety and efficacy. Patients received a single dose infusion of autologous CD19 CAR T-cell 1×10⁶ cells/kg (compassionate use) and 0.5×10⁶ cells/kg (phase I clinical trial, dose 1) respectively after preconditioning with fludarabine (25 mg/m²/day on days -5 to -3) and cyclophosphamide (1.0 g/m²/day on day -3). Safety assessments included cytokine release syndrome (CRS), immune effector cell-associated neurotoxicity syndrome (ICANS), hematologic and non-hematologic toxicities were assessed according to Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Efficacy was evaluated based on hemoglobin levels and biochemical markers of hemolysis. Single-cell RNA sequencing (scRNA-seq) and single-cell V(D)J sequencing were performed to monitor the process of B cell reconstitution in bone marrow (BM) and peripheral blood (PB) at baseline, 12 weeks (W12), and month 6 (M6) after CD19 CAR T-cell infusion.

As of July 31, 2024, the median follow-up time for the 8 patients were 6.8 months (range, 0.8-10.5 months). The safety profile in these 8 patients was satisfactory: 5 patients experienced grade 1 CRS, and two patients experienced grade 2 CRS. One patient each had grade 1 CRS and grade 1 ICANS. No hospitalization due to severe infections occurred during the follow-up period. Among the 7 patients currently evaluable for efficacy, all achieved complete remission (CR), yielding a CR rate of 100%. One relapse was observed in compassionate-use UPN2 of at 6.8 months, maintaining DFR for 6.3 months. The median duration of sustained DFR was 6.3 months (range, 1.3-9.7 months). The median time to partial remission (PR) was 15 days (range, 11-27 days) and to CR was 57 days (range, 26-118 days). CAR T-cell levels rapidly expanded after infusion, reaching peak concentrations at a median time of 10 days (range, 7-11 days). At the peak of expansion, the median number of circulating CAR T-cell was 118.8 cells/ul (range, 44.9 to 244.6 cells/ul). B-cell aplasia lasted a median of 85 days (range, 57-91 days) in 6 patients who have undergone immune B cells reconstitution. scRNA-seq and single-cell V(D)J sequencing data showed that B-cell lineage and plasmablasts were reset in both BM and PB.

CD19 CAR T-cell therapy induce rapid remission, unprecedented DFR, and favorable safety profile in rAIHA patients. These exciting data support CAR T-cell as a novel strategy for autoimmune hemolytic anemia, and provide rationale for further clinical trials.