Currently both bispecific T cell engagers (BiTE) and innate immune checkpoint blockades (eg. Anti-CD47/SIRPα) have been under development. In this study, we developed a novel compound pegylated anti-CD3 x anti-CD47 which could act with dual mechanisms of both a BiTE and an innate immune checkpoint blockade. The compound did not induce hemagglutination of RBC cells at the extremely high concentration of 2250 ug/ml, while the corresponding monoclonal antibody Hu5F9-G4 did at the concentration as low as 16.67 ug/ml. Meanwhile, in a T cell apoptosis assay, the apoptotic T cells were 16.13%, only 5.9% higher than that of the control T cell sample at the concentration of 100ug/ml of the compound and were about the same as the control sample (10.23%) at concentration of 10 ug/ml of the compound. For comparison, the reported T cell apoptosis induced by 10ug/ml Hu5F9-G4 was as high as 70%. Furthermore, the target affinity by flow cytometry demonstrated that at the concentration 10ug/ml of the compound, stained RBCs were 0.551%, while the compound bound BxPC3 cells were 22.1%, a 40-fold difference in binding. At the concentration 100ug/ml of the compound, only 7.24% RBCs were stained positively, but stained BxPC3 cells were as high as 89.3%. Although not completely understood yet, unique structure of the compound (PEGylated scFv antibody v.s. Fc-bearing antibodies) may have contributed to the differential effect of the compound to healthy cells and tumor cells, resulting in high safety performance of the compound. Furthermore, pharmacokinetics study demonstrated that in vivo elimination half-life of the compound in wild type C57BL/6 mice was 18.4 hours for the single dose of 1mg/kg. Further preclinical study about the compound is still ongoing.

Citation Format: Shumin Liu, Weidong Lyu, Yang Lei, Shuangyu Tan, Zibin Wu, Shuqiang Yin, Liling Zheng, Qiudong Zhuo, Yu (Yvonne) Wen, David Wu. A long acting bi-specific T cell engager differentially targeting CD47 positive malignant cells but not CD47 expressing healthy cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1868.