A First-in-Human Study Using BDC-4182 as a Single Agent in Advanced Gastric and Gastroesophageal Cancer

Key Inclusion Criteria: * Has disease that is measurable by Response Evaluation Criteria in Solid Tumors (RECIST) v.1.1. * Subjects must have histologically/cytologically confirmed gastric or gastroesophageal cancer that is metastatic (Stage 4) or unresectable (Stage 3). * Subjects must have received at least 1-2 prior lines of locally available standard therapies or must be intolerant of standard therapies. * For subjects in escalation: If prior Claudin 18 IHC expression is known, the subject must have some degree of Claudin 18 expression as defined as Positive or have expression ≥ 1% of tumor cells IHC ≥ 2+. Consult with Medical Monitor as needed. * Adequate organ function * Agree to have a biopsy prior to enrollment, at acceptable risk in the judgement of the Investigator. If a biopsy is not safely accessible or clinically feasible, an adequate archival tumor sample must be submitted. Key Exclusion Criteria: * Known central nervous system (CNS) metastases except for disease that is asymptomatic, clinically stable, and has not required steroids for at least 14 days before starting study treatment. * Cardiac disease, pulmonary disease, or hepatic disease * Active infection * History of inflammatory eye disease * Residual toxicity from a previous treatment * Any investigational agent or standard anti-cancer therapies within 28 days before starting study treatment or within 5 estimated elimination half-lives, whichever is shorter.