⁃ Part 1 - Monotherapy

⁃ • Subjects with advanced or metastatic solid tumor in subjects whose disease has progressed despite standard therapy, or who has no further standard therapy, or who is unsuitable for available standard treatment options.

⁃ Part 2 - Combination Therapy Subjects with treatment naïve locally advanced, unresectable or metastatic gastric, GEJ, esophageal adenocarcinoma;

• Eastern Cooperative Oncology Group (ECOG) performance status 0 or 1 with adequate organ function

• Have known PD-L1 status with prior testing by immunohistochemistry and a corresponding combined positive score (CPS)

⁃ For dose expansion and Part 2 Combination subjects:

⁃ • Must have CLDN18.2-positive tumor expression