Multicenter phase ib-2 study of first-line zanidatamab plus tislelizumab and CAPOX for HER2-positive gastric/gastroesphageal junction adenocarcinoma

A multicenter phase 1b-2 study in South Korea evaluated zanidatamab (HER2-directed bispecific antibody) plus tislelizumab (anti-PD-1 antibody) and CAPOX chemotherapy for patients with advanced HER2-positive gastric/gastroesophageal junction cancer (aGC/GEJC). Adult patients (n=33) with previously untreated HER2+ aGC/GEJC) received 3-week cycles of zanidatamab, tislelizumab and CAPOX. Confirmed investigator-assessed objective response rate was 75.8%. Median duration of response, progression-free survival, and overall survival were 23.3, 16.7, and 32.4 months, respectively. The most common treatment-related adverse events were diarrhea (100%), nausea (63.6%), and decreased appetite (48.5%); grade ≥ 3 TRAES were reported for 66.7%; diarrhea was the most common (27.3%). The authors conclude that first-line zanidatamab plus tislelizumab and CAPOX had clinically meaningful antitumor activity with a manageable safety profile in patients with HER2+ aGC/GEJC.