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Osemitamab plus Capecitabine and Oxaliplatin (CAPOX) as the First-Line Treatment of Advanced G/GEJ Cancer -Updated Efficacy Data per Claudin 18.2 Expression Level from Study TranStar102/TST001-1002-Cohort C

14 Jun, 2023


Lin Shen1, Dan Liu1 , Ning Li2, Weijian Guo2, Tianshu Liu2, Hongli Li2, Jiayi Li2, Fuyou Zhao2, Meili Sun2, Yuxian Bai2, Yanhong Deng2, Zhixiang Zhuang2, Qingxia Fan2, Liang Han2, Simon Xia3, Xuelian Zhu3, Chuan Qi3, Li Xu3 , Xueming Qian3, Caroline Germa3;

1. Peking University Cancer Hospital. 

2. Investigators. 

3. Transcenta Therapeutics Inc.


  • Adding CLDN18.2 antibody to chemotherapy is a clinically validated approach to improve longterm outcomes for patients with high CLDN18.2 expressing tumors (proved by GLOW and SPOTLIGHT).

  • Osemitamab (TST001) is a potential best-in-class humanized antibody with high affinity for CLDN18.2 and enhanced ADCC (antibody-dependent cellular cytotoxicity), delivering potent antitumor activities in both low and high CLDN18.2 expressing tumors.

  • Osemitamab monotherapy has stronger tumor growth inhibition effect than the zolbetuximab (IMAB362)-analog at the same dose, regardless of CLDN18.2 expression levels.

  • Preclinical studies showed that TST001 plus chemotherapy had better inhibitory effects on tumor growth than chemotherapy.


  • As of Apr. 21, 2023, a total of 64 patients were dosed with osemitamab in combination with CAPOX, 15 patients received osemitamab at doses ranging from 1 to 8 mg/kg Q3W in the dose escalation and 49 patients at 6 mg/kg in the dose expansion. The median follow-up was 195 days.

  • 41 out of 49 patients in the dose expansion at 6mg/kg had CLDN18.2 positive tumor (see below for definitions, High: n=9, Medium: n=13, Low: n=19), 8 patients didn’t get their tumor tested (unknown CLDN18.2 expression). The baseline demographics of this dose expansion are similar to the overall population published on 2023 ASCO (abstract 4046*) and there are no clinically significant differences in baseline characteristics across different CLDN18.2 expression levels.

  • The safety profile of osemitamab is mainly characterized by manageable on-target off-tumor effects and has been presented during 2023 ASCO (abstract 4046*). Most of these AEs are of grade 1 or 2 and occurring during the first 2 cycles.

  • As of April 21, 2023, among the 49 patients at 6mg/kg from dose expansion, 42 patients had measurable lesions and at least one post treatment tumor assessment, 28 (66.7%) achieved partial response. Best overall response assessment by CLDN18.2 expressions levels at 6mg/kg in the dose expansion are presented in Table 1. The response rate appears similar regardless of the CLDN18.2 expression levels.

  • As of the cut-off date, there is no clear trend between progression-free survival and the total (1+/2+/3+combined) CLDN18.2 expression levels (Figure 4). The same trend was observed whether CLDN18.2 expression was assessed by 2+/3+ combined or 3+ only (data not shown).

  • As of cut-off date, 26 out of 64 patients had progression disease or death, with an estimated median progression-free survival (PFS) 9.5 months, median PFS stratified according to CLDN18.2 was immature and need long term follow-up (Figure 5).