Inclusion Criteria:

          1. Patients with histologically proven CD117-positive and/or c-kit or PDGFR mutation
             gastrointestinal stromal tumor (GIST), which is metastatic or unresectable, locally
             advanced, and have failed to or intolerance of prior imatinib and sunitinib treatment

          2. At least one measurable lesion according to the RECIST criteria (version 1.1)

          3. Aged between 20-75 years

          4. With Eastern Cooperative Oncology Group (ECOG) performance score 0-2.

          5. Life expectancy ≥ 4 months

          6. At least 4 weeks apart from prior systemic (including chemotherapy, approved targeted
             therapy or investigational agent) and surgical treatment, and recovery from all prior
             treatment-related toxicity to grade < 1 according to Common Terminology Criteria for
             Adverse Events (CTCAE) v4.0.

          7. With adequate organ and marrow function as defined below:

               -  WBC ≥ 3.00 × 103/ mm3 and absolute neutrophil count ≥ 1.50 × 103/ mm3

               -  Platelet count ≥ 100.0 × 103/mm3

               -  Hemoglobin level ≥ 9 gm/dL

               -  Serum creatinine (Cr) ≦1.5 x UNL or eGFR ≥ 60 ml/min (by Cockroft-Gault method)

               -  Serum bilirubin ≤ 1.5 x UNL , ALT ≤ 2.5x UNL. If obstructive jaundice with proper
                  drainage, serum bilirubin ≤ 3 x UNL is acceptable.

          8. Women of childbearing potential and men must agree to use accepted methods of
             contraception during the course of the study and at least 3 months after last dose of
             treatment

          9. Willing to have tumor biopsy at screening (all patients) and able to comply with study
             requirement at 4 weeks post treatment

         10. With ability to understand and the willingness to sign Informed Consent Form.

        Exclusion Criteria:

          1. Have received imatinib or sunitinib, chemotherapy, any investigational agents or
             participate in any investigational drug study within 28 days before enrolment

          2. Have major surgery within 28 days before enrolment (diagnostic biopsy or line
             placement is not considered major surgery)

          3. With active multiple cancers or history of other malignancy within the last three
             years, except treated curable non-melanoma skin cancer, in-situ cervical cancer,
             Dukes' A colorectal cancer.

          4. With known CNS metastasis

          5. Symptoms of heart failure or greater to Class III (by NYHA criteria) or history of
             uncontrolled dysrrhythmias

          6. Sinus bradycardia (resting heart rate <50 beats/min) secondary to intrinsic conduction
             system disease; Patients with sinus bradycardia secondary to pharmacologic treatment
             may enrol if they are allowed to withdraw the treatment and can result in
             normalization of the resting heart rate to within normal limits

          7. Myocardial infarction or active ischemic heart within 6 months

          8. Screening QTc >450 msec in males; QTc >470 msec in females, or previous history of QTc
             prolongation while taking other medications

          9. Presence of active infection or systemic use of antimicrobials within 72 hours prior
             to enrolment

         10. Treatment with therapeutic doses of coumadin-type anticoagulants. [Maximum daily dose
             of 2mg, for line patency permitted]

         11. Patients who are unable to comply protocol requirement, i.e. tumor tissue sampling or
             blood sampling for pharmacodynamic and pharmacokinetics study

         12. Patients who have know hypersensitivity or prior therapy of any HSP90 inhibitor
             compound or its derivatives