AZD0901 in Participants With Advanced Solid Tumours Expressing Claudin18.2

This open-label, multi-centre study consists of individual sub studies, each evaluating the safety and tolerability of AZD0901. Sub study 1 will investigate the safety, tolerability, and anti-tumour activity of AZD0901 monotherapy in participants with advanced or metastatic gastric esophageal cancer expressing CLDN18.2. Participants will receive AZD0901 monotherapy via intravenous (IV) infusion and will be randomised in to one of 2 arms. Sub study 2 will consist of two parts, a safety run-in and a dose expansion part to investigate the safety and efficacy of AZD0901 in combination with different chemotherapy agents in participants with pancreatic cancer. Substudy 3 will investigate the safety, tolerability, and anti-tumour activity of AZD0901 monotherapy in participants with advanced or metastatic Biliary tract cancer.