Trastuzumab is approved for the treatment of HER2-positive breast cancer and gastric cancer. The recent study showed that HER2 overexpression or amplification is noted about 5-15% of total biliary tract cancer patients. The aim of this study is to evaluate the efficacy and safety of trastuzumab in the combination of current standard gemcitabine plus cisplatin.

Inclusion Criteria:

1. The subject with disease that is not amendable to a curative treatment approach or locally advanced or metastatic or unresectable CCC with histological diagnosis

2. At least one measurable(per RECIST 1.1) lesion

3. Primary or metastatic tumor with HER2 positive defined on IHC2+, FISH+ or IHC3+

4. ECOG Performance status 0 or 1

5. At least 3 months for life expectancy Common inclusion criteria

6. Men or women over 19 years at time of signing ICF

7. Signed Informed Consent Form

   Exclusion Criteria:

8. Received prior chemotherapy for advanced/metastatic disease (the adjuvant/neoadjuvant chemotherapy completed at least 6 months before enrolled will be accepted)

9. Not recovery from toxicities related to any prior treatments excluding alopecia (eg, neurological toxicity to ≥ Grade 2)

10. History of malignancy other than CCC within 5 years prior to screening, with the exception of malignancies with a negligible risk of metastasis or death, such as carcinoma in situ or thyroid papillary carcinoma Hematology, chemistry or organ function

11. ANC < 1.5 × 109/L, or Platelet < 100 × 109/L

12. Total bilirubin > 1.5 × ULN; or AST/ ALT > 2.5 × ULN (or if the tumor has expanded into the liver, > 5 × ULN); or, alkaline phosphatase > 2.5 × ULN (or > 5 × if the tumor has expanded into the liver, or > 10 × ULN if the tumor has expanded into the brain without liver,); or albumin < 2.5 g/dL

13. Creatinine clearance < 60 mL/min(calculated using the Cockcroft-Gault formula) Other exclusion criteria related to IP

14. History of proved congestive heart failure; angina with medication; evidence of transmural myocardial infarction on ECG; uncontrolled hypertension(systolic> 180 mmHg or diastolic> 100 mmHg); clinically significant heart valve disease; uncontrolled arrhythmia

15. LVEF < 50% (calculated by cardiac sonography or MUGA)

16. Subject with rest dyspnea due to metastatic tumor or other disease or who needs oxygen therapy

17. Chronic or high-dose corticosteroid treatment

18. Clinically significant Hearing impairment Common exclusion criteria

19. History or evidence of CNS metastases

20. Interstitial pneumonia or pulmonary fibrosis with symptom and exact lesion on chest X-ray

21. Hearing loss

22. Uncontrolled significant systemic disease (eg, infection or uncontrolled DM)

23. Pregnant or lactating females

24. Sexually active fertile subjects without contraception

25. Treatment with other investigational therapy within 4 weeks prior to initiation of study treatment

26. Radiotherapy within 4 weeks prior to initiation of study treatment (the rest at least 2 weeks after palliative radiotherapy for bone metastasis and recovery from the effects of radiation will be accepted.)

27. Major surgery within 4 weeks prior to initiation of study treatment

28. History of HIV and active HBV or HCV

29. Previously identified allergy or hypersensitivity to components of the study treatment formulations