A Dose-escalation Study of ARX788, IV Administered in Subjects With Advanced Cancers With HER2 Expression

This is a 2-part, Phase 1 FIH study with Phase 1a designed to determine the maximum tolerated dose (MTD)/recommended Phase 2 dose (RP2D) in subjects with metastatic cancers with a human epidermal growth factor receptor 2 (HER2) test result that is in situ hybridization (ISH) positive (+) or immunohistochemistry (IHC) 3+ or 2+, and Phase 1b designed to assess anticancer activity and safety in three expansion cohorts: two different advanced breast cancer expansion cohorts (namely, for tumors that test as HER2 ISH positive or IHC3+ and for tumors that test as HER2 ISH negative with IHC 2+), and one advanced gastric cancer expansion cohort (for tumors that test as HER2 ISH positive or IHC3+).