Study of AZD5863 in Adult Participants With Advanced or Metastatic Solid Tumors

Key Inclusion Criteria: Age ≥ 18 at the time of signing the informed consent Histologically confirmed diagnosis of adenocarcinoma of the stomach, gastro-esophageal junction, esophagus, or pancreas Must have at least one measurable lesion according to Response Evaluation Criteria in Solid Tumors (RECIST) v1.1 Must show positive CLDN18.2 expression in tumor cells as determined by central immunohistochemistry (IHC) Eastern Cooperative Oncology Group Performance status (ECOG PS): 0-1 at screening Predicted life expectancy of ≥ 12 weeks Adequate organ and bone marrow function measured within 28 days prior to first dose as defined by the protocol Contraceptive use by men or women should be consistent with local regulations, as defined by the protocol Must have received at least one prior line of systemic therapy in the advanced/metastatic setting Key Exclusion Criteria: Unresolved toxicity from prior anticancer therapy of Common Terminology Criteria for Adverse Events (CTCAE) Grade ≥ 2 except for those defined by the protocol Participant experienced unacceptable cytokine release syndrome (CRS) or Immune Effector Cell Associated Neurotoxicity (ICANS) following prior T cell engagers (TCE) or chimeric antigen receptor T (CAR-T) cell therapy Active or prior documented autoimmune or inflammatory disorders within 3 years of start of treatment central nervous system (CNS) metastases or CNS pathology, as defined by the protocol, within 3 months prior to consent Infectious disease including active human immunodeficiency virus (HIV), active hepatitis B/C, uncontrolled active systemic fungal, bacterial or other infection Cardiac conditions as defined by the protocol History of thromboembolic event within the past 3 months prior to the scheduled first dose of study intervention Participant requires chronic immunosuppressive therapy Participants on anticoagulation therapy