Auto Hematopoietic Stem Cell Transplantation Combined with Another Target Humanized CAR-T Cells for Refractory/Relapsed B-Cell Non-Hodgkin Lymphoma after Failure of Murinized CD19-CAR-T Therapy

Background: The prognosis of refractory/relapsed aggressive B-cell non-Hodgkin lymphoma (r/r B-NHL) is extremely poor especially for the patients who failed to CD19-Specific chimeric antigen receptor-T (CAR-T) cells therapy.Even sequentially autologous hematopoietic stem cell transplantation(ASCT) could not maintain a durable remission in most patients.

Aims: To prolong relapse-free survival, we combined ASCT and another target humanized CAR-T cells to treat r/r B-NHL patients failed to murinized CD19-CAR-T cells therapy with either CD22 or CD20 antigen expression on tumor cell.The safety and efficacy will be evaluated.

Methods: From December 2019 to March 2021, 12 patients were enrolled. The median age was 38 (16-68) years old. The diagnosis included DLBCL (n=8) ,BL(n=3) and PMBCL (n=1). The median IPI score was 3 (range,2-4).There were 9 patients(9/12,75%) with extranodal lesions. Six cases(6/12,50%) were with TP53 mutations. The disease status was progressive disease in all patients who failed to multi-line therapies and murinized CD19-CAR-T cells therapy.In order to further reduce the tumor burden, all patients were treated with combined chemotherapy before transplantation. Before the trial, the expression of CD20 and CD22 antigen in tumor tissue was positive confirmed by immunohistochemistry,and the target was selected according to the antigen expression. Conditioning with BEAM-based regimen was applied. The kinetics and function of CAR-T cells was monitored by quantitative PCR and flow cytometry. The efficacy was evaluated by PET-CT every 3 month after transplantation. Results: The autologous peripheral blood stem cells were infused with the median CD34 ⁺ cells 3.91(range,0.46-9.46)×10 ⁶/kg.Humanized CAR-T cells with the median 1.85 (range,0.13-3.26)×10 ⁶/kg were infused 2 day after stem cells,including target antigen CD20(7/12,58.3%) and CD22(5/12,41.7%). Cytokine release syndrome (CRS) occurred in 11 cases with 5 cases in grade I, 3 case in grade II and 3 cases in grade III.One case developed immune effector cell-associated neurotoxicity syndrome (ICANS) in grade IV. The peak of cytokine IFN-γ and IL-6 post baseline in patients with grade III CRS were significantly higher than those in patients with grade I-II CRS,especially in ICANS patient.Six cases with grade II and III were relieved with glucocorticoid. The neutrophil and platelets engraftment was achieved in all cases on median days 14 (range,9-22) and 14(range,8-35) respectively post-transplant .Seven cases of bacterial enteritis were seen. Pneumonia occurred in 7 cases.For CAR-T cells expansion,the peak time in vivo was on median 11(range,7-28) days after CAR-T cells infusion.The median peak lever of CAR-T cells was 20.3 (range,0.13-60.4)×10 ⁶/L, which was positively correlated with the number of CART infused. The tumor burden before transplantation was not significantly associated with CAR-T cells expansion.The median duration of CAR-T cells in vivo was 30 days, and the longest lasting time was 139 days post-transplant so far. B-cell aplasia was documented in all cases(7/7,100%) of CD20-CART group and two cases(2/5,40%) of CD22-CART group during the follow-up. With the median follow-up 266 (range,118-565) days, 9/12(75%) patients survived,seven cases(7/12,58.3%) achieved complete remission(CR),2 cases(2/12,16.7%) achieved PD and survival with tumor.Kaplan-Meier survival analysis showed that OS and PFS rates were 71.3% and 66.6% respectively at 9 months after transplantation.Two cases(2/12,16.7%) with BL and one with DLBCL (1/12,8.3%)died of PD.Significantly lower levels of Cumulative CAR T cell levels (AUC) during the first 1 month post transplantation were observed in patients with disease progression compared with those who had durable responses (P<0.0001).

Conclusion: CRS is manageable and has no influence on hematopoiesis reconstitution.With current protocol, complication was mild and encouraging disease control was found. ASCT combined with another target humanized CAR-T therapy is a safe and effective salvage strategy for r/r B-NHL after failure of murinized CD19-CAR-T. Long-term follow-up is needed.

[Key words] refractory/relapsed B-cell non-Hodgkin lymphoma; failure of CD19-CAR-T; another target CAR-T cell; autologous hematopoietic stem cell transplantation