A Study of IMAB362 in Japanese Subjects With Locally Advanced or Metastatic Gastric or Gastro-esophageal Junction (GEJ) Adenocarcinoma

Inclusion Criteria: * Subject has histologically or cytologically confirmed diagnosis of gastric or gastro-esophageal junction adenocarcinoma. * Subject has gastric or gastroesophageal junction (GEJ) adenocarcinoma based on radiographic imaging or endoscopic examination. * Subject agrees not to participate in another interventional study while on treatment. * Subject has Eastern Cooperative Oncology Group (ECOG) performance status 0-1. * Subject has predicted life expectancy ≥ 12 weeks. * Subject must have an available tumor specimen collected at any time prior to the first dose of study treatment. * Subject must meet all of the pre-specified criteria on the laboratory tests that will be analyzed locally within 7 days prior to the first dose of study drug. * Locally advanced or Metastatic gastric or GEJ adenocarcinoma with no standard of care treatment option or subject is ineligible to receive available standard of care treatment option. * Subject's tumor sample has Claudin (CLDN)18.2 membranous staining with any intensity as determined by central Immunohistochemistry (IHC) testing. (Safety part only) * Subject has CLDN18.2 high expression in ≥75% of tumor cells demonstrating moderate to strong membranous staining as determined by central IHC testing. (Expansion Part Only) * Subject is an appropriate candidate for a tumor biopsy and is amenable to undergo a tumor biopsy during the Screening period and on-treatment tumor biopsy. (Expansion Part Only) * Subject has at least 1…