this study is an open, single arm, multi-center Phase I /IIa clinical study. In the phase I, patients with locally advanced unresectable or metastatic malignant solid tumors (gastric cancer, esophageal cancer, gastroesophageal junction cancer, pancreatic cancer, ovarian cancer, cholangiocarcinoma, etc.) that are positive for Claudin 18.2(positive membrane staining observed in any tumor cells) will be included. in Phase I dose escalation phase, 7 dose groups will be preset：0.25 mg/kg、0.5 mg/kg、1.0 mg/kg、1.5 mg/kg、2.0 mg/kg、2.5 mg/kg、3.0mg/kg; In phase I dose confirmation phase, it is initially considered to set up 1~2 dose groups according to the dose-escalation phase MTD/MAD, with 3~6 subjects in each group. In the phase IIa cohort expansion phase, with reference to the results of the phase I study, subjects were grouped according to different tumor types, there are 30 subjects in each group, initially considering the inclusion of Claudin 18.2 positive(a clear cut-off value will be defined based on the results of Phase I) locally advanced unresectable or metastatic gastric cancer, esophageal cancer, gastroesophageal junction cancer, and pancreatic cancer patients.(The specific tumor types and groups will be further adjusted based on the results of the phase I study).
In Phase I, This study will explore the tolerability and safety of RC118 in patients with locally advanced unresectable or metastatic malignant solid tumors with positive Claudin 18.2 expression, and determine the maximum tolerated dose (MTD) and the recommended dose in phase II clinical trials (RP2D); In Phase IIa, to explore the clinical effectiveness and safety of long-term use of RC118 at RP2D doses for patients with different tumor types。