Section to complete information about the inclusion and exclusion criteria for participant selection, including age and gender.
Inclusion criteria:
1. Age: 18-75 years (including the limit values), male or female;
2. ECOG performance status score 0-1;
3. Gastric adenocarcinoma or esophagogastric junction adenocarcinoma confirmed by histology or cytology;
4. Metastatic or recurrent disease, previously treated with standard first-line chemotherapy regimens (including platinum-containing and/or fluoropyrimidine-containing regimens) (recurrence or metastasis during adjuvant therapy or within 6 months after completion will be considered first-line treatment), or who received targeted therapy, or received immunotherapy, with disease progression confirmed by the investigator or in the medical history;
5. According to RECIST 1.1 evaluation criteria, there must be at least one measurable lesion;
6. High EGFR expression (IHC2 or IHC3) detected during the recruitment period in primary or metastatic lesion tissue (when multiple samples are available at the same time, the preference will be: the complete specimen instead of a biopsy sample, and metastatic tissue instead of the primary lesion);
7. Estimated survival ≥12 weeks;
8. Adequate organ function, defined as:
Total bilirubin ≤ 1.5 times the upper limit of normal (ULN); alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≤ 2.5 times ULN in the absence of liver metastases; ALT or AST ≤ 5 times ULN in the presence of liver metastases;
Serum creatinine ≤ 1.5 times ULN; neutrophil count ≥1.5×10^9/L; white blood cell count ≥ 3.0×10^9/L; platelets ≥ 100×10^9/L; hemoglobin ≥ 90 g/L;
9. If the patient is of childbearing potential, both the patient and their partner must be willing to use contraception;
10. Negative pregnancy test in women of potential fertility/negative serum hCG within 72 hours prior to randomization (postmenopausal women with at least 12 months of amenorrhea are considered infertile, and women known to have undergone tubal ligation are not required to have a pregnancy test);
11. The subject understands and agrees with the study procedures, decides to participate voluntarily, and signs the informed consent form.
Exclusion criteria:
1. Prior treatment received before study initiation: a. Disease progression following prior paclitaxel chemotherapy or anti-EGFR antibody therapy; or administration of paclitaxel chemotherapy or anti-EGFR antibody treatment within 4 weeks prior to randomization. b. Participation in another therapeutic/interventional clinical trial (counted from the last administration of first-line treatment), or receipt of prohibited concomitant therapies specified in the study protocol within 4 weeks prior to randomization or at screening.
2. Major surgical procedure, incisional biopsy (e.g., laparotomy), or significant traumatic injury within 4 weeks prior to randomization.
3. Presence of brain metastases or leptomeningeal metastases.
4. History of malignant tumors other than gastric adenocarcinoma or gastroesophageal junction adenocarcinoma (exceptions: cured cervical carcinoma in situ, cutaneous basal cell carcinoma, or other malignancies cured for at least 5 years).
5. Severe hemorrhagic disorders (e.g., severe gastrointestinal bleeding) or vasculitis occurring within 3 months prior to randomization.
6. Presence of other severe illnesses, including but not limited to:
a. Refractory congestive heart failure (NYHA Class III or IV, see Appendix 2), unstable angina, poorly controlled arrhythmias, uncontrolled moderate to severe hypertension (systolic blood pressure >160 mmHg or diastolic blood pressure >100 mmHg);
b. Uncontrolled diabetes mellitus;
c. Psychiatric disorders impairing the ability to provide informed consent and/or protocol compliance;
d. Other severe medical conditions rendering the patient ineligible for study participation at the investigator’s discretion.
7. Known allergies or contraindications to any components of anti-EGFR antibody formulations, paclitaxel, or other study medications.
8. Toxicities from prior anti-tumor therapy that have not resolved to Grade ≤1 per CTCAE v5.0, with the following allowable exceptions:
a. Alopecia;
b. Other toxicities deemed clinically insignificant by the investigator (e.g., stable Grade 2 fatigue, hyperpigmentation).
9. History of clinically significant third-space fluid accumulation (including large-volume pleural effusion or ascites) unmanageable with drainage or other interventions.
10. Pre-existing Grade 2–4 peripheral neuropathy per CTCAE criteria.
11. Known past or current active primary or secondary immunodeficiency.
12. Confirmed positive HIV serology or syphilis infection. For patients with positive Treponema pallidum antibodies, a non-treponemal syphilis serology test (RPR or TRUST) will be performed; the investigator will also review clinical history and prior treatment records to confirm latent/inactive syphilis. Active hepatitis B or C infection at screening is also exclusionary:
• Active hepatitis B: HBsAg positive plus HBV DNA >1000 copies/mL;
• Active hepatitis C: Anti-HCV antibody positive plus HCV RNA >1000 copies/mL.
13. Females of childbearing potential who are pregnant, breastfeeding, planning pregnancy, or not using effective contraception. Sexually active male patients who refuse contraceptive measures throughout the study period and for 3 months after the last study drug dose, or intend to donate sperm during this timeframe.
14. Any medical, psychiatric, or other condition deemed by the investigator to pose risks to subject safety or compromise the integrity of study data should the patient enroll in this clinical trial.
