Authors:

Xueming Qian¹, Fei Teng¹, Huanhuan Guo¹, Xinlai Yao¹, Lei Shi¹ , Yadong Wu¹, Dongting Zhao¹, Yi Gu^1
1Suzhou Transcenta Therapeutics Co., Limited, Suzhou, China

Background:

• Osemitamab (TST001) is a best-in-class humanized antibody with improved CLDN18.2 binding affinity and ADCC activity.

• Here, we evaluated the dynamics of on-treatment PD-L1 expression on the tumor cells in both in vivo tumor models and in vitro tumor cells, and studied preclinical efficacy of the combination of Osemitamab and anti-PD-L1/PD-1 mAb +/- oxaliplatin/5-FU (Oxa/5-FU) in both CLDN18.2+/PD-L1+ and CLDN18.2+/PD-L1- PDX tumor models.

Conclusions:

• PD-L1 upregulation and increasing of TIL after Osemitamab treatment provided a rationale for combination potential of Osemitamab and anti-PD-L1/PD-1 mAb.

• The synergistic effects of Osemitamab and GC standard of care (SoC: antiPD-1 mAb + Oxa/5-FU) observed in our preclinical tumor models support Osemitamab in combination with SoC chemotherapy +/- Nivolumab in G/GEJ patients regardless of PD-L1 status.