A Study of MRG002 in Patients with HER2-Positive Advanced Solid Tumors and Locally Advanced or Metastatic Gastric/Gastroesophageal Junction (GEJ) Cancer

Inclusion Criteria: * The patient must be able to provide written informed consent and follow the requirements specified in protocol. * Age: ≥18 years. * Life expectancy ≥6 months. * Must have histologically or cytologically confirmed HER2-positive metastatic, unresectable cancer and must have had prior disease progression on all standard therapies for their tumor. * Available archival tumor tissue (archival or from a new biopsy). * At least one non-irradiated measurable tumor lesion according to RECIST v1.1. * Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. * Acceptable liver, renal, hematologic and coagulation function. Exclusion Criteria: * Toxicities (except alopecia \& fatigue) due to prior antitumor therapy are higher than CTCAE v5.0 Grade 1. * Toxicities due to radiotherapy (higher than grade 1) have not resolved to CTCAE v5.0 Grade ≤1 at least 21 days prior to the screening visit. * Prior palliative or therapeutic radiation therapy to any RECIST v1.1 target lesion that defines baseline measurable disease for the study. * Untreated or uncontrolled central nervous system (CNS) metastases. * Any chemotherapy, biotherapy, immunotherapy, radiotherapy or other anti-tumor therapy within 3 weeks of the first dose of study treatment. * Any severe cardiac dysfunction within 6 months of enrollment. * Pulmonary embolism or deep vein thrombosis within 3 months prior to the first dose of study drug. * Concurrent malignancy within 5 years prior to entry. *…