RC48 Combined With Adebrelimab, Apatinib and S-1 as Neoadjuvant Therapy in Locally Advanced Gastric Cancer

Inclusion Criteria:

* 1\. Participants voluntarily join this study, are able to complete the signing of the informed consent form, and have good compliance;
* 2\. Age between 18 to 75 years old (at the time of signing the informed consent form), with no gender restrictions;
* 3\. Gastrointestinal cancer or gastroesophageal junction adenocarcinoma confirmed by histology and/or cytology, diagnosed as locally advanced according to the 8th edition of the AJCC standards, with a cTNM diagnosis of T3-4aN+M0 and T4aNanyM0 based on ultrasound endoscopy or enhanced CT/MRI scan (and diagnostic laparoscopy if necessary), and agree to receive curative surgical treatment, with the investigator assessing the potential for tumor resectability;
* 4\. Have not previously received systemic treatment for the current disease, including anti-tumor chemotherapy/immunotherapy, etc.;
* 5\. HER2 overexpression confirmed by IHC results from endoscopic biopsy tissue (defined as: IHC 2+, 3+);
* 6\. ECOG score of 0-1;
* 7\. Estimated life expectancy of ≥6 months;
* 8\. Good major organ function:

Exclusion Criteria:

* 1\. Concurrent malignant disease other than gastric cancer (excluding early-stage tumors that have been radically treated);
* 2\. Tumor lesions with a tendency to bleed (such as active ulcerative tumor lesions with positive fecal occult blood test, history of hematemesis or melena within 2 months before signing the informed consent form, or assessed by the investigator as being at risk of significant gastrointestinal hemorrhage, etc.) or having received blood transfusion treatment within 4 weeks before the study medication; 3. Inability to take oral medication;
* 4\. Currently participating in another interventional clinical study treatment, or having received other investigational drugs or used investigational medical devices within 4 weeks before the first administration of the study medication;
* 5\. Has had systemic treatment required within 2 years before the first administration of the study medication;
* 6\. Known allogeneic organ transplantation (except for corneal transplantation);
* 7\. Known allergy to any medication used in this study;
* 8\. Peripheral neuropathy of grade ≥2;
* 9\. Known history of human immunodeficiency virus (HIV) infection (i.e., positive for HIV 1/2 antibodies);
* 10\. Active hepatitis B or C infection;
* 11\. Received live vaccines within 30 days before the first administration (Day 1 of Cycle 1);
* 12\. Pregnant or breastfeeding women;
* 13\. Presence of any severe or uncontrollable systemic disease.