Authors:

Lin Shen¹, Dan Liu¹, Ning Li², Weijian Guo², Tianshu Liu², Hongli Li², Jiayi Li², Yuxian Bai², Yanhong Deng², Zhixiang Zhuang², Meili Sun², Qingxia Fan², Fuyou Zhao², Liang Han², Zhenzhong Xia³,
Jianming Wang³, Chuan Qi³, Li Xu³, Xueming Qian³, Caroline Germa^3
1. Peking University Cancer Hospital.

². Investigators.

³. Transcenta Therapeutics Inc

Background：

• Adding an anti-claudin18.2(CLDN18.2) antibody to a chemotherapy is a clinically validated approach for patients with high CLDN18.2 expressing gastric tumors.

• TST001 is a potential best-in-class antibody with higher CLDN18.2 binding affinity and lower fucose, resulting in enhanced antibody-dependent cellular cytotoxicity (ADCC) activity.

• Pre-clinical studies showed that TST001 has stronger tumor growth inhibition effect than the IMAB362-analog at the same dose, regardless of CLDN18.2 expression levels, which may lead to anti-tumor activity even in low to median CLDN18.2-expressing gastric cancer.

Results:

• As of April 21st, 2023, 64 patients were dosed with TST001 in combination with CAPOX, 15 patients received TST001 at doses ranging from 1 to 8 mg/kg Q3W in the dose escalation and 49 patients at 6 mg/kg in the expansion phase. 41 out of 49 patients in dose expansion were CLDN18.2 positive (defined in method). The median follow up is 197.5 days. Patient characteristics were typical of 1st line G/GEJ cancer, with relatively higher percentage of peritoneal disease (40.6%). 18 patients are still on treatment.

• No patients experienced dose-limiting toxicity; Treatment-emergent adverse events (TEAEs) were mostly grade 1-2, including nausea, hypoalbuminaemia, anaemia and vomiting. Only one patient experienced grade 3 nausea and vomiting at dose of 6mg/kg, one patient experienced grade 3 hypoalbuminaemia at dose of 8mg/kg. No patient experienced such event of grade 4.