Allogeneic Hematopoietic Stem Cell Transplantation with Conditioning Including Donor Humanized CAR-T Cells for Refractory/Relapsed B-Cell Non-Hodgkin Lymphoma and Multiple Myeloma

Background: The prognosis of refractory/relapsed aggressive B-cell non-Hodgkin lymphoma (r/r B-NHL) and multiple myeloma (r/r MM) is extremely poor, especially for the patients who failed to CAR-T cells therapy and/or ASCT.

Aims: Forr/r B-NHLand r/r MM, a clinical trial using Allo-HSCT with conditioning including donor humanized CAR-T cells from the same donor (allo-CAR-T) has been registered, and the safety and efficacy will be evaluated.

Methods: From September 2020 to May 2021, 11 patients were enrolled.The median age was 41 (26-64) years old. The diagnosis included high grade B-cell lymphoma (n=9) and Multiple myeloma (n=2). Seven cases were with TP53 mutations.All patients was progressive disease (PD) who failed to multi-line therapies, including chemotherapy (n=11), ASCT (n=4), autologous CAR-T (n=11).In order to further reduce the tumor burden, all patients were treated with combination therapy before transplantation. Before the trial, the expression of CD19 and/or CD22 or CD20 antigen in tumor tissue of r/r B-NHL and BCMA antigen in r/r MM patients was positive confirmed by immunohistochemistry.There were matched sibling identical donor in 1 case,matched unrelated donor in 1 case and haploidentical donor in 9 cases；Conditioning with busulfan, fludarabine-based regimen combined with allo-CAR-T was applied. Tacrolimus, mycophenolate mofetil, a short-term methotrexate and antithymocyte globulin were used for GVHD prophylaxis. The kinetics and function of CAR-T cells was monitored by quantitative PCR and flow cytometry. The efficacy was evaluated by PET-CT in r/r NHL as well as bone marrow puncture and immunofixation electrophoresis in r/r MM every 2 month after CAR-T infusion.

Results: The median allo-CAR-T cells infused were 4 (range,0.78-4.88)×10 ⁶/kg. CRS occurred in all cases with 6 cases in grade I, 1 case in grade II and 4 cases in grade III.The peak of cytokine IFN-γ and IL-6 in grade III CRS were significantly higher than those with grade I-II.No ICANS was noted. Four cases with grade III CRS were relieved with methylprednisolone. G-CSF-mobilized PBSC were infused 7 days after allo-CAR-T with the median CD34 ⁺ cells 6 (range,3-8.19)×10 ⁶/kg. The neutrophil and platelets engraftment was achieved in all cases on median days 13 (range,11-24) and 16 (range,14-85) respectively post-transplant .All cases were donor type by STR analysis.Three cases of grade II acute GVHD were seen. CMV viremia occurred in 7 cases.For allo-CAR-T cell expansion,the peak time in vivo was on median 14(range,7-28) days after infusion.The median peak lever was 221 (range,0.191-1502)×10 ⁶/L, which positively correlated with the number of allo-CAR-T infused. The tumor burden before transplantation was not significantly associated with allo-CAR-T expansion.Levels of allo-CAR-T cells were very low after the first 2 months of HSCT which detected persistently in 9/11(81.8%) patients, and the longest lasting time was 239 days post-transplant so far. B-cell aplasia was documented in 8/9 cases of r/r B-NHL during the follow-up. With the median follow-up 171 (range,100-295) days, 7/11(63.6%) patients survived,five cases(5/11,45.5%) achieved CR,one cases(1/11,9.1%) obtained PR, and 1 case(1/11,9.1%) of MM achieved SD and survival with tumor .Three cases(3/11,27.3%) with DLBCL died of PD whose disease status before transplantation were SD or PD, one patient(1/11,9.1%) died of infection.Significantly lower levels of Cumulative CAR T cell levels (AUC) during the first 2 month post transplantation were observed in patients who relapsed compared with those who had durable responses (P=0.0001).aGVHD were not associated directly with in vivo CAR T-cell expansion(P=0.193).

Conclusion: Our preliminary results have shown that CRS is manageable and has no influence on hematopoiesis reconstitution. Allo-CAR-T cells still exist persistently post-transplant in majority of patients, which may contribute a long-term anti-lymphoma effect.With current protocol, aGVHD and viral reactivation was mild. Allo-HSCT with conditioning including allo-CAR-T cells is a safe and effective strategy for r/r B-NHL and MM. The Poor clinical efficacy was associated with high tumor burden before transplantation.

[Key words] refractory/relapsed B-cell non-Hodgkin lymphoma; refractory/relapsed multiple myeloma;allogeneic CAR-T cell; allogeneic hematopoietic stem cell transplantation