Zolbetuximab combined with EOX as first-line therapy in advanced CLDN18.2+ gastric (G) and gastroesophageal junction (GEJ) adenocarcinoma: Updated results from the FAST trial.

16Background: Physiologically, the tight junction protein CLDN18.2 is present only in the gastric mucosa. Upon malignant transformation, CLDN18.2 epitopes are exposed on the cell surface and accessible to targeted therapy. Zolbetuximab (formerly IMAB362) is a chimeric mAb that mediates specific killing of CLDN18.2+ cancer cells through immune effector mechanisms; single-agent activity has been reported in G/GEJ cancer. Methods: Patients (pts) with advanced HER2-negative (HER–) G/GEJ cancer with CLDN18.2 expression of ≥ 2+ staining intensity with the anti-CLDN18 43-14A mAb in ≥ 40% tumor cells were eligible (NCT01630083). Patients were randomized 1:1 to receive first-line EOX ± zolbetuximab (loading dose 800 mg/m2, then 600 mg/m2) Q3W. The study was extended with an exploratory arm of 1000 mg/m2 zolbetuximab + EOX Q3W (data not presented). Primary endpoint was PFS; secondary endpoints included OS, ORR, and safety/tolerability. Results: A total of 161 pts (G, n = 128; GEJ, n = 27; esophagus n = 6) were rand...