This research is designed to determine if experimental treatment with AZD5863, a T cell-engaging bispecific antibody that targets Claudin 18.2 (CLDN18.2) and CD3, is safe, tolerable and has anti-cancer activity in patients with advanced solid tumors.

This is a first-time in human, modular Phase I/II, open-label multicentre study of AZD5863 monotherapy administered intravenously (Module 1), or AZD5863 monotherapy administered subcutaneously (Module 2) in patients with advanced or metastatic solid tumors. Each module contains dose-escalation (Part A) and dose-expansion (Part B).

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
• Previous history of hemophagocytic lymphohistiocytosis (HLH) / macrophage activation syndrome (MAS)
• 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 infection with EBV, 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 with long-acting anticoagulants or other class of anticoagulants at therapeutic doses

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal Vivli.org. All requests will be evaluated as per the AZ disclosure commitment: https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure

"Yes", indicates that AZ are accepting requests for IPD, but this does not mean all requests will be approved.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA/PhRMA Data-Sharing Principles. For details of our timelines, please refer to our disclosure commitment at https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure

When a request has been approved AstraZeneca will provide access to the anonymized individual patient-level data via secure research environment Vivli.org. A Signed Data Usage Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information.