BoShengJi Pharma Advances Bispecific CD19/CD22 CAR-T with EAAAK Linker into Clinical Development Following Promising Preclinical Results

    To address the high recurrence rate after CD19 CAR-T cell therapy, it is necessary to further design and develop new CAR-T constructs. Dual therapeutic targets have become a consensus among many researchers. Currently, there are numerous reports on the development of bispecific CAR-T cells, some of which have shown encouraging therapeutic effects, while others have demonstrated limited efficacy.Research finds that the clinical trial of decitabine combined with CD19/CD22 CAR-T achieves a 63.6% complete remission rate, with no severe cytokine release syndrome or neurotoxicity observed. Moreover, the study suggests that CD19/CD22 CAR-T may be the optimal consolidation therapy for primary patients with persistent minimal residual disease after early consolidation treatment.Moreover, a large number of clinical trials have shown that bispecific CAR-T has certain significance in solving antigen-negative relapse caused by single-target CAR-T treatment. However, the actual clinical efficacy of bispecific CAR-T still has much room for improvement.

CD22 is a member of the sialic acid-binding immunoglobulin-like lectin family, primarily expressed intracellularly during the early stages of B-cell development. As B cells mature, it transitions to extracellular expression and is highly expressed in most B-cell malignancies. Therefore, CD22 is speculated to be a potential target that may synergize with CD19 in CAR-T cell therapy to reduce disease recurrence rates.

Recently, fromBo Sheng Ji Medicine Science and TechnologyResearchers from Bo Sheng Ji Medicine Science and Technology (Suzhou) Co., LTD and Soochow University published a research paper titled "Enhanced efficacy of CD19/CD22 bispecific CAR-T cells with EAAAK linker on B-cell malignancies" in the European Journal Of Haematology.The study designed four different CD19/CD22 CAR structures using G4S and EAAAK, and ultimately screened out the optimal bispecific CAR structure.This structure exhibited superior cytotoxicity and in vivo anti-tumor effects compared to single-target CAR-T cells in both in vitro and in vivo experiments, offering a promising option for clinical patients with low...ResponseOr recurrence provides research strategies.

ResearchUtilize (G4S) 4 and（EAAAK)3 two structures as linkers, constructing CD19/CD22 bispecific CAR-T cells,The results showed that dual-target CAR-T had increased cytotoxicity and cytokine secretion levels compared to single-target CAR-T, but the use of (EAAAK)3 was even more significant.

Further research on dual-target CAR-T constructs (Bis-C CAR-T, Bis-D CAR-T) based on (EAAAK)3 showed that Bis-C CAR-T had a higher proportion of central memory T cells while reducing the expression of inhibitory receptors PD-1, LAG-3, and TIM-3. This indicates that Bis-C CAR-T cells exhibit better sustained killing ability and memory phenotype differentiation.

Subsequently, NSG xenograft mice were constructed with subcutaneous transplantation of 100% Raji, or 50% Raji + 50% CD19KO Raji, or 100% CD19KO Raji. The results showed that,In in vivo experiments simulating CD19-negative relapse, Bis-C CAR-T was more effective than CD19 CAR-T in controlling tumor progression in mice with low or no CD19 expression, prolonging mouse survival.

Studies have shown that bispecific CAR-T cells can simultaneously target CD19 or CD22 positive tumor cells, providing a new strategy to address the limitations of single-target CAR-T therapy for B-cell tumors (limited response or relapse).

Thinking

This study designs various dual-targeting CAR-T cells with different structures, and by comparing these structures, screens out the optimal Bis-C CAR-T cell with good performance in sustained killing, cytokine secretion, target antigen specificity, and memory phenotype. Meanwhile, the study finds that the linker also has an important impact on the function of bispecific CAR-T. Bispecific CAR-T with EAAAK linker shows better efficacy than that with G4S linker.This discovery may have guiding significance for designing bispecific CAR-T or antibodies targeting other targets.

    Reference：Enhanced efficacy of CD19/CD22 bispecific CAR-T cells with EAAAK linker on B-cell malignancies. Eur J Haematol. 2023 Sep 6. doi: 10.1111/ejh.14090.