Combination Therapy of GCNT and Tislelizumab in Advanced Biliary Tract Cancer

Inclusion Criteria * Histologically confirmed biliary tract cancer (BTC), including intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, and gallbladder cancer (excluding neuroendocrine tumors, sarcoma, mixed cholangiocarcinoma-HCC, and ampullary carcinoma). * Age ≥ 19 years at the time of signing informed consent. * Treatment-naïve for unresectable or metastatic BTC, or recurrence/metastasis at least 6 months after curative surgery or adjuvant chemotherapy. * Measurable lesions per RECIST v1.1. * ECOG Performance Status (PS) of 0-1 within 14 days prior to the first dose. * Life expectancy of ≥ 3 months. * Adequate organ function (within 14 days prior to the first dose): * Hematologic function: Hemoglobin (Hb) ≥ 9.0 g/dL, Absolute neutrophil count (ANC) ≥ 1,500/μL, Platelet count ≥ 100,000/μL * Renal function: Serum creatinine ≤ 1.5 × ULN or CrCl (Cockcroft-Gault) ≥ 45 mL/min * Hepatic function: AST and ALT ≤ 3.0 × ULN (≤ 5.0 × ULN for hepatic metastases), Total bilirubin ≤ 1.5 × ULN * Coagulation: INR ≤ 1.5 or prothrombin time ≤ 1.5 × ULN, aPTT ≤ 1.5 × ULN * Reproductive status: * Female participants must provide proof of non-childbearing status or a negative serum pregnancy test within 7 days before the first dose. * Female subjects receiving cisplatin must agree to effective contraception for 14 months after the last dose; male subjects must agree for 11 months. * Women of childbearing potential and non-sterilized men must use at least two effective contraceptive methods during the study and for 6 months after the last dose. * Cardiac function: * Left ventricular ejection fraction (LVEF) ≥ 50% (by echocardiography or MUGA scan) * No serious valvular disorders or arrhythmias * Corrected QT interval ≤ 470 msec at screening * Willingness to provide tumor tissue samples by biopsy (endoscopic or excisional). Exclusion Criteria * Prior treatment history: * Prior systemic chemotherapy, biological therapy, immunotherapy, or hormone therapy for unresectable or metastatic BTC * Prior adjuvant chemotherapy or radiation therapy within 6 months before recurrence * History of another malignancy within 5 years, except: * Completely resected basal cell carcinoma, stage 1 squamous cell carcinoma, carcinoma in situ, or superficial bladder cancer * Unresolved toxicities from prior treatment that could affect study evaluation * Known hypersensitivity to any study drug (tislelizumab, gemcitabine, cisplatin, nab-paclitaxel) * Active or history of autoimmune disease, except: * Hypothyroidism (on stable hormone therapy), vitiligo, or psoriasis not requiring treatment * History of interstitial lung disease, pulmonary fibrosis, or radiation pneumonitis * Active gastrointestinal disease: * Active peptic ulcer, colitis, or diverticulitis Known central nervous system (CNS) metastasis * Uncontrolled tumor-related complications: Pericardial effusion, pleural effusion, or ascites requiring intervention, Uncontrolled tumor-related pain * Significant cardiovascular conditions: * Myocardial infarction within 180 days before enrollment * Uncontrolled angina within 180 days before enrollment * NYHA Class III or IV congestive heart failure * Persistent hypertension ≥ 150/90 mmHg despite treatment * Arrhythmias requiring medical intervention * Thrombosis or vascular diseases requiring surgery * Uncontrolled diabetes mellitus * Active infections requiring systemic treatment within 14 days before the first dose * Recent treatment history: * Systemic corticosteroids (except prophylactic or short-term use) or immunosuppressants within 28 days before the first dose * Antitumor therapy (cytotoxic, targeted, or immunotherapy) within 28 days before the first dose * Pleurodesis within 28 days before the first dose * Major surgery under general anesthesia within 28 days before the first dose * Local anesthesia or minor surgery within 14 days before the first dose * Radiation therapy within 28 days before the first dose (bone metastasis radiation within 14 days is allowed) * Positive for: * HIV-1 or HIV-2 * Active Hepatitis B or C (except HBV DNA \<500 IU/mL with stable antiviral therapy) * Pregnant or breastfeeding women * Use of unapproved drugs within 28 days before enrollment * Cognitive impairment preventing informed consent * Severe neuropathy (Grade ≥ 2, CTCAE v5.0) * Hearing impairment * Inability or unwillingness to provide informed consent