Inetetamab Plus Chemotherapy ± PD-1/PD-L1 in HER2+ Advanced Biliary Cancer

Inclusion Criteria: * Males or females aged ≥18 years; * Histologically confirmed HER2-positive metastatic biliary tract cancer; * ECOG performance status of 0 to 1; * No prior treatment with anti-HER2 therapies; * Patients have not received any systemic anticancer treatment in the recurrent/metastatic setting; * Patients who have experienced disease recurrence more than 6 months after curative surgery; if adjuvant therapy (chemotherapy and/or radiotherapy) was received post-surgery, patients must have had recurrence more than 6 months after completion of adjuvant therapy; * Presence of at least one measurable lesion; * Adequate function of major organs as defined by the following criteria; * Estimated survival of ≥3 months; * Voluntary participation in this study, signing of the informed consent form, good compliance, and willingness to cooperate with follow-up. Exclusion Criteria: * Known allergy or contraindication to any component of the study drugs; * Previous treatment with anti-HER2 therapies; * Prior use of immunotherapy; * Use of immunosuppressive agents within 14 days before the first dose, except: Intranasal, inhaled, topical steroids, or local injections (e.g., intra-articular) Systemic corticosteroids ≤10 mg/day prednisone or equivalent Steroids for hypersensitivity reactions (e.g., premedication for CT scans) * Known active central nervous system metastases or carcinomatous meningitis; * Other malignancies within 5 years, excluding cured cervical carcinoma in situ, basal cell carcinoma, or squamous cell skin cancer; * Major surgery or significant trauma within 4 weeks before randomization, or planned major surgery; * Severe cardiac disease; * Resting dyspnea due to tumor progression or comorbidities, or requiring supplemental oxygen; * Neuropathy ≥ Grade I per NCI criteria; * Active interstitial lung disease (ILD) or pulmonary disease requiring bronchodilators; * History of immunodeficiency; * Participation in another drug trial within 4 weeks before screening; * Pregnant or breastfeeding women, or women of childbearing potential with a positive pregnancy test at screening; unwillingness to use effective contraception during and for 6 months after the study; * Any serious concomitant illness or conditions that may interfere with the planned therapy or render participation unsuitable.