Clinical Study On CAR-T Cells Combined With Dendritic Cells Pulsed With Eps8 Peptide For Refractory/Relapsed Acute Leukemia

BackgroundThe long-term survival rate of leukemia patients is low,and refractory/relapse is the main factor leading to low long-term survival rate of leukemia patients.Chimeric antigen receptor T(CAR-T)cells therapy is a novel targeted immunotherapy in recent years.With the application of CD 19-CAR T cells in refractory/relapsed B cell leukemia,although the effect is significantly better than the conventional therapy,recurrence after remission is the bottleneck restricting the efficacy of CAR-T cells,and minimal residual disease(MRD)is the root of recurrence.In the case of low tumor burden,tumor antigen derived dendritic cells(DCs)vaccine not only can activate immune killer cells to clear MRD,but also produce long-term specific anti-tumor immune memory cells to prevent tumor recurrence.Epidermal growth factor receptor pathway substrate 8(Eps8)is abnormally highly expressed in leukemia patients,and is considered to be used as a new target for MRD monitoring and treatment.In the preclinical study of our team,it was found that the DC vaccine targeting tumor antigen Eps8 can effectively improve the proliferation potential of CAR-T cells,increase the proportion of central memory T cells,and enhance the immune function of CAR-T cellsMethods1.Preparation of DCs pulsed with Eps8 peptide,and identification of activity,purity,phenotype and microorganisms;2.Use mixed lymphocyte reaction,cytotoxicity in vitro,ELISA and ELISPOT to detect cytokines secretion,and MHC tetramer to detect the level of antigen-specific T cells to evaluate the immunological effects of DCs pulsed with Eps8 peptide;3.The patients were divided into 2 groups.The patients in the control group were infused with CAR-T cells.The patients in the study group were infused with CAR-T cells and DCs pulsed with Eps8 peptide.The clinical adverse reactions,liver and kidney function,blood routine and other safty indicators of the two groups were monitored;4.Bone marrow smear to detect the number of bone marrow blasts,flow cytometry to monitor MRD,qPCR to monitor the number of CAR-T cells in vivo,MHC tetramer to detect antigen-specific T cells in vivo.Evaluating the objective response rate,complete response rate,overall survival time,and disease-free survival time of CAR-T cells combined with DCs pulsed with Eps8 peptide.ResultsDCs pulsed with Eps8 peptide was successfully prepared.The killing rate of CTLs induced by DCs pulsed with Eps8 peptide was 60%in vitro.DCs pulsed with Eps8 peptide significantly increased the secretion levels of the factors IL-12p70 and IFN-γ.Furthermore,it also increased the proportion of antigen-specific T cells.It indicated that DCs pulsed with Eps8 peptide had good immune function and ability to induce anti-tumor immune response.Ten patients with refractory relapsed acute leukemia were enrolled in the study.Five of them were treated with CAR-T cells combined with DCs pulsed with Eps8 peptide,others were treated with single CAR-T cells therapy.It was clear that the CAR-T cells combined with DCs pulsed with Eps8 peptide treatment did not significantly increase the adverse effects compared with the single CAR-T cells treatment.And there were no adverse reactions related to the DC vaccine.The median duration of CAR-T cells in vivo of the single CAR-T cells treatment group was 21 days.The median duration of CAR-T cells in vivo of the combined group was 208 days,which was significantly higher than the CAR-T cells treatment group.Three patients in the single CAR-T cells treatment group had complete remission,2 of whom had MRD-negative complete remission,with a median disease-free survival time of 29 days;In the CAR-T cells combined with Eps8 antigen peptide-sensitized DCs treatment group,all patients had achieved complete remission,including 4 patients with MRD-negative complete remission,with a median disease-free survival time of 332 days.CAR-T cells combined with DCs pulsed with Eps8 peptide significantly prolonged the disease-free survival time of patients compared with the single CAR-T cells group.ConclusionTo sum up,this study successfully prepared DCs pulsed with Eps8 peptide.CAR-T cells combined with Eps8 tumor antigen peptide-loaded DC vaccine is safe to treat with refractory/recurrence acute leukemia.DC vaccine targeting Eps8 tumor antigen can increase the efficacy of CAR-T cells and prolong the disease-free survival time of patients.