A Study of Disitamab Vedotin Combined With Tislelizumab and Chemotherapy Versus Tislelizumab Combined With Chemotherapy in HER2-Low Advanced Gastric or Gastroesophageal Junction Adenocarcinoma

A Phase III, Randomized Trial Comparing RC48 Plus Chemotherapy and Tislelizumab With Tislelizumab Plus Chemotherapy as First-line Treatment in Participants With HER2 Low Advanced Gastric or Gastrioesophageal Junction Adenocarcinoma (RC48-C039)

The purpose of this study is to evaluate the efficacy and safety of **Disitamab Vedotin combined with Tislelizumab and CAPOX versus Tislelizumab combined with CAPOX** as first-line treatment for patients with HER2-low advanced gastric or gastroesophageal junction adenocarcinoma.

Inclusion Criteria:

• Voluntarily consent to participate in the study and sign the informed consent form
• Expected survival period >12 weeks
• ECOG Performance Status 0 or 1
• Histologically confirmed unresectable locally advanced, metastatic, or recurrent gastric or gastroesophageal junction adenocarcinoma
• No prior systemic therapy for locally advanced or metastatic gastric cancer
• HER2-low expression
• At least one assessable lesion according to RECIST v1.1 criteria
• Adequate organ function
• For female subjects: They should be surgically sterilized, postmenopausal, or agree to use a medically approved contraceptive method (such as an intrauterine device, contraceptive pill, or condom) during the study treatment period and for 6 months after the end of the study treatment. A blood pregnancy test must be negative within 7 days before the study medication is administered, and they must not be breastfeeding
• For male subjects: They should be surgically sterilized or agree to use a medically approved contraceptive method during the study treatment period and for 6 months after the end of the study treatment
• Able to understand the study requirements and willing to comply with the study and follow-up procedures

Exclusion Criteria:

• Presence of central nervous system (CNS) metastasis and/or carcinomatous meningitis
• Peripheral neuropathy > Grade 1
• Tumor lesions with a tendency to bleed
• Uncontrolled diarrhea
• Bone metastases with a risk of paraplegia
• Past or current interstitial lung disease, or presence of drug-induced pneumonia, radiation pneumonia, or severely impaired lung function
• Other malignancies within 5 years before the first dose, except for those expected to be cured with treatment (e.g., adequately treated thyroid cancer, cervical carcinoma in situ, basal or squamous cell skin cancer, or ductal carcinoma in situ of the breast treated with curative surgery)
• Pregnant or breastfeeding women