Preclinical imaging evaluation of a bispecific antibody targeting hPD1/CTLA4 using humanized mice
Xingguo Hou, Song Liu, Ziqing Zeng, Zilei Wang, Jin Ding, Yan Chen, Xiangyu Gao, Jianghua Wang, Guanxi Xiao, Baiyong Li, Hua Zhu, Zhi Yang
Abstract
The lack of an efficient way to screen patients who are responsive to immunotherapy challenges PD1/CTLA4-targeting cancer treatment. Immunotherapeutic efficacy cannot be clearly determined by peripheral blood analyses, tissue gene markers or CT/MR value. Here, we used a radionuclide and imaging techniques to investigate the novel dual targeted antibody cadonilimab (AK104) in PD1/CTLA4-positive cells in vivo . First, humanized PD1/CTLA4 mice were purchased from Biocytogen Pharmaceuticals (Beijing) Co., Ltd. to express hPD1/CTLA4 in T-cells. Then, mouse colon cancer MC38-hPD-L1 cell xenografts were established in humanized mice. A bispecific antibody targeting PD1/CTLA4 (AK104) was labeled with radio-nuclide iodine isotopes. Immuno-PET/CT imaging was performed using a bispecific monoclonal antibody (mAb) probe 124 I-AK104, developed in-house, to locate PD1 + /CTLA4 + tumor-infiltrating T cells and monitor their distribution in mice to evaluate the therapeutic effect. The 124 I-AK104 dual-antibody was successfully constructed with ideal radiochemical characteristics, in vitro stability and specificity. The results of immuno-PET showed that 124 I-AK104 revealed strong hPD1/CTLA4-positive responses with high specificity in humanized mice. High uptake of 124 I-AK104 was observed not only at the tumor site but also in the spleen. Compared with PD1- or CTLA4-targeting mAb imaging, 124 I-AK104 imaging had excellent standard uptake values at the tumor site and higher tumor to nontumor (T/NT) ratios. The results demonstrated the potential of translating 124 I-AK104 into a method for screening patients who benefit from immunotherapy and the efficacy, as well as the feasibility, of this method was verified by immuno-PET imaging of humanized mice. • An antibody-PET probe targeting PD1/CTLA4 was radiolabeled. • High affinity to PD1/CTLA4 in vitro and in vivo. • This tracer can noninvasively demonstrate the presence of PD1/CTLA4-positive infiltrating T cells at the tumor site in humanized mice using an imaging method.