• Capable of giving signed informed consent prior to any study procedure.

• Participant must be at least 18 years or the legal age of consent in the jurisdiction in which the study is taking place at the time of signing the ICF.

• Histologically confirmed unresectable, locally advanced or metastatic adenocarcinoma of gastric, GEJ, or distal esophagus (distal third of the esophagus) and the following requirement:

• (a) Participants with positive CLDN18.2 expression from archival tumor collected within past 24 months or from a fresh biopsy.

• Disease progression on or after at least one prior line of treatment (LoT) for advanced or metastatic disease, which included a fluoropyrimidine and a platinum, for advanced or metastatic disease.

• Must have at least one measurable or evaluable lesion assessed by the Investigator based on RECIST 1.1.

• ECOG performance status of 0 or 1 with no deterioration over the previous 2 weeks prior to baseline or day of first dosing.

• Predicted life expectancy of ≥ 12 weeks.

• Adequate organ and bone marrow function

• Body weight of ≥ 35 kg.

⁃ Sex and Contraceptive Requirements