Abstract 3192: A novel long acting pegylated T cell engager targeting CD3 and cd19 with effective tumor killing and no potential CRS risk in CD19+ hematologic malignancies

Abstract The development of bispecific T cell engagers represents a highly effective immunotherapy strategy for the treatment of hematologic malignancies. However, Blinatumomab, a bispecific T cell engager of CD3/CD19, has disadvantages in clinical setting due to the adverse pharmacokinetics (PK), which resulted in less than 2 hours of in vivo elimination half-life, neurotoxicity, and cytokine release syndrome. In this study, a bispecific antibody JY108 was developed to target CD19 and CD3e with much reduced affinities towards both targets (revealed by Biacore assay results). JY108 was prepared by a patented pegylation bispecific linker technology, which could address the limitations of current therapeutic approaches. In vitro cytotoxicity assay results demonstrated that the EC50s of the drug specific cytotoxicity of T cells mediated by JY108 are in the concentrations of ng/ml, while blinatumomab mediated cytotoxicity to the same CD19+ cells are in the concentrations of pg/ml. Despite the weaker in vitro cytotoxicity than Blinatumomab, JY108 presents comparable tumor inhibition effects with Blinatumomab in different in vivo studies, which include the PBMC reconstructed models with established MEC-1 or Farage tumors, the delayed drug administration on human PBMCs/tumor co-transplanted model of Raji. In addition, JY108 prolonged the survival of animals with Nalm6 brain metastasis more significantly than Blinatumomab at the same dosage. Furthermore, the PK study revealed that at the different dosages, the circulation T1/2s of JY108 in mice are above 20 hours, which is expected to result in more significant efficacious benefits in clinical setting. Meanwhile, the completed package of GLP-toxicity study did not observe any drug related tox to the model animals (including no cytokine release in vivo, no neurotoxicity, no respiratory toxicity, etc. ), and JY108 did not induce significant cytokine release than the blank control to the whole blood or PBMCs from healthy donor in vitro. In the efficacious concentrations of exerting cytotoxicity to CD19+ tumor cells in the presence of PBMC, JY108 did not induce significant cytokine release than the blank control, while blinatumomab always induced significant cytokine release. We postulated that the lower CD3 affinity of JY108 most probably resulted in the decoupling of the signaling for activating the gene expression of cytokines from the secretion of the polarized lytic granules by T cells, which resulted in a much milder T cell activation by JY108. Currently, JY108 is a phase I trial candidate and awaits further evaluations. Citation Format: Shumin (Sam) Liu, Yu (Yvonne) Wen, Weidong Lyu, Shuqiang Yin, Yang Lei, Dechun Wu, Zibin Wu, Qiudong Zhuo. A novel long acting pegylated T cell engager targeting CD3 and cd19 with effective tumor killing and no potential CRS risk in CD19+ hematologic malignancies abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 3192.