Tandem CD19/CD22 Dual Targets CAR-T Cells Therapy Obtains Superior CR Rate Than Single CD19 CAR-T Cells Infusion As Well As Sequential CD19 and CD22 CAR-T Cells Infusion for Relapsed/Refractory B-Cell Acute Lymphoblastic Leukemia Patients
Authors: Liu Sining , Zhang Xinyue , Dai Haiping , Cui Qingya , Cui Wei , Yin Jia , Li Zheng , Xue Shengli , Yang Chunxiu , Yang Xiao , Qiu Huiying , Miao Miao , Chen Suning , Jin Zhengming , Fu Chengcheng , Li Caixia , Sun Aining , Han Yue , Wang Ying , Yu Lei , Wu Depei , Tang Xiaowen 
Published: November 2021

Abstract
Background: CD19 chimeric antigen receptor T (CAR-T) cells therapy has shown great success in B-cell acute lymphoblastic leukemia (B-ALL). To reduce the possibility of relapse due to CD19 antigen loss, sequential CD19/CD22 and tandem CD19/CD22 dual targets CAR-T cells have been developed. However, the optimal combination strategy of target antigens for CAR-T cells is still uncertain. This study was designed to compare the efficacy and safety of single CD19, tandem CD19/CD22 and sequential CD19/CD22 CAR-T cells therapies in relapsed/refractory(R/R) B-ALL patients.
Methods: Between March 2016 and August 2020, a total of 200 patients with R/R B-ALL successfully received 230 CAR-T treatments (30 patients received the second CAR-T therapy and 8 patients received the third CAR-T therapy) were screened in this study. Among them, 168 patients received single CD19 CAR-T therapy, 49 patients received tandem CD19/CD22 CAR-T therapy, and 13 patients received sequential CD19/CD22 CAR-T therapy. ALL patients enrolled in the CD19 CAR-T clinical trials (NCT03919240) or CD19/CD22 CAR-T clinical trials (NCT03614858).
Results: The baseline characteristics of patients were similar among the three groups. The complete remission (CR) rates were 82.7% (139/168) in patients who received CD19 CAR-T therapy, 95.9% (47/49) in patients who received tandem CD19/CD22 CAR-T therapy, and 69.2% (9/13) in patients who received sequential CD19/CD22 CAR-T therapy (P=0.012). Tandem CD19/CD22 CAR-T therapy remained one of the significant favorable factors in multivariate logistic regression analysis of CR rate in all patients (hazard ratio, 0.081; 95% CI, 0.010-0.671). Furthermore, minimal residual disease (MRD)-negative CR rates were 66.7%, 81.6% and 61.5%, respectively (P=0.092). There was no significant difference in the incidence of adverse events among the three groups. Severe cytokine release syndrome (CRS, Grade ≥ 3) occurred in 25.0% of patients in CD19 group, 18.4% of patients in tandem CD19/CD22 group, and 23.1% in sequential CD19/CD22 group (P=0.641).
There was no significant difference in overall survival (OS) and leukemia-free survival (LFS) among three groups (6-month OS: 83.1%, 90.0% and 88.9%, respectively, P=0.1620; 6-month LFS: 76.2%, 76.2% and 88.9%, respectively, P=0.8179). Univariate and multivariate Cox regression analyses showed that a better LFS related to less frequencies of relapse, lower tumor burden, MRD-negative CR and bridging allogeneic hematopoietic stem cell transplantation (allo-HSCT).
Conclusions: Tandem CD19/CD22 dual targets CAR-T cells therapy obtains superior CR rate than single CD19 and sequential CD19/CD22 CAR-T cells therapy. This provides an effective treatment option for R/R B-ALL patients with chemotherapy resistance.

Disclosures
No relevant conflicts of interest to declare.