Mecapegfilgrastim Combined With Adebrelimab and Chemotherapy as Neoadjuvant Therapy in Resectable GC/GEJC

Inclusion Criteria: * 1.Subjects aged 18-75 years (including 18 and 75 years old); * 2.Subjects who understand the study procedures and content, and voluntarily sign the written informed consent form; * 3.Subjects with HER2-negative or HER2 status unknown gastric or gastroesophageal junction adenocarcinoma, clinically staged as T3-4a/N+M0 locally advanced gastric cancer by ultrasound gastroscopy, CT/MRI and other imaging evaluations. * 4.Subjects who have not received prior systemic therapy. * 5.Subjects with Eastern Cooperative Oncology Group Performance Status score (ECOG PS score): 0-1; * 6.Subjects with life expectancy ≥ 12 months; * 7.Subjects with good major organ function, that is, the relevant investigation indicators within 14 days before enrollment meet the following requirements: haemoglobin ≥ 90 g/L ; neutrophil count \> 1.5 × 109/L; platelet count ≥ 100 × 109/L; total bilirubin ≤ 1.5 × ULN (upper limit of normal); alanine transaminase (ALT) or aspartate transaminases (AST) ≤ 2.5 × ULN; endogenous creatinine clearance ≥ 60 mL/min (Cockcroft-Gault formula); cardiac ultrasound doppler assessment: left ventricular ejection fraction (LVEF) ≥ 50%; * 8.Subjects with thyroid function indicators: thyroid stimulating hormone (TSH), free thyroxine (FT3/FT4) within the normal range or with slight and clinically insignificant abnormalities; * 9.Subjects weighing more than 40 kg, or with BMI \> 18.5; Exclusion Criteria: * 1.Subjects with a history of or concurrent with othe…