The dose escalation phase will enroll subjects with HER2-expressing locally advanced or metastatic gastric cancer, including gastroesophageal junction adenocarcinoma. HER2 expression is defined as follows (meets one of the following):~• HER2 IHC3+, 2+, 1+; (Subjects with HER2 immunohistochemistry (IHC) results of IHC1+, IHC 2+, and IHC 3+, previous test results (confirmed by the investigator) or research center test results are acceptable;~The dose-escalation phase preset doses for this combination therapy are as follows:~RC48-ADC: 2.5mg/kg Q2W; RC98 increasing dose: 5.0mg/kg Q2W, 10.0mg/kg Q2W, 15.0mg/kg Q2W. The dose escalation phase of the combination therapy adopts the Bayesian optimal interval (BOIN) design method: the fixed dose of RC48-ADC is 2.5 mg/kg, and the dose of RC98 is escalated, and the initial incremental dose of RC98 is 5.0 mg/kg. MTD has a target toxicity rate of 0.3 and a maximum sample size of 24. The subjects will be enrolled in units of 3, with a maximum of 12 subjects in each dose group; the 28 days after the first dose will be used as the observation window of DLT to make decisions such as dose increase and decrease. If the DLT criteria were not met within 28 days after the first dose, dose escalation was not continued to observe DLT and MTD. After the dose escalation period is over, the investigator decides the recommended phase 2 dose (RP2D) based on the available safety, tolerability, PK, and efficacy information.~After completing the dose-limiting toxicity (DLT) evaluation, the subject can continue to receive the original dose of study drug treatment (but not more than the currently ongoing escalating dose or the maximum tolerated dose under the condition that the investigator judges that there may be benefits) ), subjects received treatment until intolerable toxicity, disease progression, or termination of the study by the sponsor.
This is a single-center, open-label, dose-escalation phase I clinical study.This study aimed to evaluate the safety, tolerability, pharmacokinetics and preliminary clinical efficacy of RC48-ADC combined with RC98 in subjects with advanced gastric cancer.Which will provide a reference basis for dose confirmation in subsequent clinical studies.