Pan et al. prepared anti-CD22 CAR T cells to treat 34 relapsed/refractory B-ALL patients, most of whom failed or relapsed after anti-CD19 CAR therapy. 70.5% of patients showed complete response (CR) by day 30, correlating with CAR T cell expansion. Median CAR T persistence was 28 days. Subsequent hematopoietic stem cell transplant sustained responses but most non-transplant patients experienced relapse, without evidence of antigen loss. Normal B cells were found only in relapsed patients, implying CAR persistence was key in maintaining CR. Cytokine release syndrome and neurotoxicity, both low grade, were common adverse events.
Contributed by Alex Najibi
Despite worldwide promising clinical outcome of CD19 CAR-T therapy, relapse after this therapy is associated with poor prognosis and has become an urgent problem to be solved. We conducted a CD22 CAR T-cell therapy in 34 relapsed or refractory (r/r) B-ALL pediatric and adult patients who failed from previous CD19 CAR T-cell therapy. Complete remission (CR) or CR with incomplete count recovery (CRi) was achieved in 24 of 30 patients (80%) that could be evaluated on day 30 after infusion, which accounted for 70.5% of all 34 enrolled patients. Most patients only experienced mild cytokine-release syndrome and neurotoxicity. Seven CR patients received no further treatment, and 3 of them remained in remission at 6, 6.6, and 14 months after infusion. Eleven CR patients were promptly bridged to transplantation, and 8 of them remained in remission at 4.6 to 13.3 months after transplantation, resulted in 1-year leukemia-free survival rate of 71.6% (95% CI, 44.2-99.0). CD22 antigen loss or mutation was not observed to be associated with relapsed patients. Our study demonstrated that our CD22 CAR T-cells was highly effective in inducing remission in r/r B-ALL patients, and also provided a precious window for subsequent transplantation to achieve durable remission.