Abstract 1562: Pre-clinical research of ZHB015, an anti-CD26/CD3 bispecific T-cell-engaging antibody

Abstract PURPOSE: CD26 is a highly expressed transmembrane target in multiple solid tumors such as renal cell carcinoma, prostate cancer and malignant pleural mesothelioma. YS110 is the first reported monoclonal antibody targeting CD26 and has been proved safe in phase I/II clinical trials in Japan and France, but the efficacy is not satisfying. Although FDA approved axitinib in combination with avelumab as the first-line treatment for PD-L1 positive advanced renal cell carcinoma in 2019, the problems still exist such as individual differences and drug tolerance. Consequently, we developed ZHB015, a bispecific T-Cell-Engaging antibody that targets CD26 high-expressing solid tumors, and furtherly to validate its efficacy and safety. METHODS: ZHB015, which is expressed and manufactured from recombinant CHO cells, has a tandem single chain variable fragment antibody (BiTE) structure. CD26 expression level in tumor cells was detected by FACS. CD26 expression in tumor tissues was detected by immunohistochemistry. The affinity between ZHB015 with human CD26 or CD3 were detected by Octet. The killing effect of ZHB015-mediated PBMC on tumor cells was detected by Calcein-AM release. ELISA was used to detect the cytokine secretion of ZHB015 in the process of mediating the killing effect. The antitumor activity in vivo was studied in mouse xenograft models. Daily intravenous administration dosage of ZHB015 was 1.5mg/kg. Both axitinib in combination with avelumab and YS110 were served as control in vivo. RESULTS: ZHB015 pilot production process was performed and confirmed good scale-up feasibility. The positive rates of CD26 in 786-0, 0S-RC-2 and A498 renal cancer cells were all over 95%. 99.4% mesothelioma cell NCI-H226 and 93.8% prostate cancer cell PC-3 were CD26 positive. IHC experiments confirmed that CD26 is highly expressed in renal cancer tissues. ZHB015 has an affinity of 0.91nM with CD26 and 0.75nM with human CD3. ZHB015 can bind to both CD26 and CD3 simultaneously. 786-0, OS-RC-2, NCI-H226, and PC-3 CD26 expressing tumor cells were lysed with EC50 values in a range of 219.6 to 752.3pg/ml, and the killing activity was significantly higher than homemade YS110. In the process of mediating PBMC to kill target cells, ZHB015 induced a lower cytokines secretion than control molecule YS110-BiTE. In the xenograft models of OS-RC-2 and A498, TGI of ZHB015 was 100%, TGI of different doses of axitinib in combination with avelumab did not exceed 71%, and YS110 had no antitumor effect. The TGI of ZHB015 in PC-3 and NC1-H226 models was 96% and 66%, respectively. CONCLUSION: ZHB015 simultaneously binds to tumor CD26 and T cell CD3, inducing T cell mediated antitumor effects. ZHB015 has an outstanding anti-tumor activity in vitro and in vivo, which is superior to YS110 and the current first line treatment. Thus, ZHB015 is being further developed as a potential therapy for CD26 positive solid tumor. Citation Format: Chennan Ge, Peipei Cao, Jianhua Hang, Tao Zhang, Yu Zhuang, Na Ding, Bruce Y. Ma. Pre-clinical research of ZHB015, an anti-CD26/CD3 bispecific T-cell-engaging antibody [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1562.