Perioperative Therapies in Locally Advanced Unresectable Gastric Cancer

Gastric cancer (GC) is the fifth most commonly diagnosed cancer, with over one million cases diagnosed annually worldwide. Human epidermal growth factor receptor 2 (HER2) overexpression in GC (seen in 4.4% to 53.4% of patients in different reports) is predictive biomarker of response to HER2-targeting therapies. Trastuzumab in combination with cisplatin or oxaliplatin, and a fluoropyrimidine (capecitabine or 5-fluorouracil \[5-FU\]), is approved anti-HER2 therapy for first-line treatment of HER2-positive gastric or gastroesophageal junction (GEJ) cancer. Rilvegostomig 750 mg Q3W was selected as recommended Phase 2 dose based on all available ARTEMIDE-01 clinical safety, efficacy, PK, RO data as well as modeling analysis. The dose of 750 mg Q3W is predicted to achieve intra-tumoral RO of ≥ 90% in the majority of participants across a broad spectrum of conditions. This is a phase II study to initially assess the efficacy of perioperative Trastuzumab Deruxtecan (T-DXd) and Capecitabine combination with or without Rilvegostomig in patients with HER2 positive locally advanced unresectable GC and potentially by subsequent protocol amendment in HER2 low locally advanced GC. Other agents may also subsequently be assessed in this protocol, by protocol amendments