This study consists of two parts. In Part A, patients will receive MRG002 as a monotherapy at doses of 2.2 or 2.6 mg/kg intravenously (IV) over 60-90 minute on Day 1 of every 3 weeks (Q3W), to determine the maximum tolerated dose (MTD) and recommended phase II dose (RP2D). In part B, patients will receive a single IV infusion of MRG002 at RP2D on Day 1 of Q3W.
The objective of this study is to assess the safety, efficacy, and pharmacokinetics of MRG002, as well as the immunogenicity as defined by the incidence of anti-drug antibody (ADA) of MRG002 in patients with HER2-positive advanced solid tumors and locally advanced or metastatic gastric/gastroesophageal junction (GEJ) cancer.