Inclusion Criteria:
1. 19 years of age or older at the time of signing informed consent
2. Subjects with histologically confirmed metastatic thymic epithelial tumor
3. Have at least one measurable target lesion for evaluation according to RECIST v1.1 criteria
4. Patients who are not candidates for surgery and require consolidation chemotherapy
5. Radiologic progression of disease after first-line standard therapy
6. ECOG performance status of 0 or 1
7. Life expectancy greater than 3 months
8. Patients with adequate bone marrow and organ function \[Bone marrow function\]
* Neutrophils (ANC) \> 1,500/mm3
* Platelets \> 100,000/mm3
* Hemoglobin \> 9 g/dL \[Liver function\]
* Total bilirubin ≤ 1.5 x upper limit of normal (if liver metastases are present, up to 3 x upper limit of normal is allowed)
* AST, ALT ≤ 3 x upper limit of normal (if liver metastases are present, up to 5 x upper limit of normal is allowed) \[Renal function\]
* Creatinine clearance \> 50 mL/min (Cockcroft-Gault equation)
9. Subjects who have voluntarily decided to participate in this study and have given written informed consent and are able to participate in all periods of the study.
Exclusion Criteria:
1. Patients with more than 22 concurrent tumors and/or other active malignancies requiring systemic treatment within the last 22 years at the time of the first dose of investigational drug (however, patients may participate in the study if the principal investigator determines that the previous malignancy has been treated and no further treatment is required).
2. Patients treated with a previous anti-angiogenic agent (ex. Sunitinib, bevacizumab etc)
3. Patients with difficult to control central nervous system metastases
4. Those with spinal cord compression, leptomeningeal carcinomatosis
5. Patients with uncontrolled systemic disease, including uncontrolled hypertension, active bleeding, or active infection.
However, individuals with the following hepatitis B/C infections may be enrolled
* Hepatitis B surface antigen (HBsAg) positive, with an ALT in the normal range and HBV DNA \<2,000 IU/ml, and taking antiviral therapy to prevent hepatitis reactivation may be enrolled.
* HBs Ag negative, hepatitis B core antibody (IgG anti-HBc) positive, and HBV DNA below the lower limit of quantification may be enrolled.
* Anti-HCV Ab positive individuals can be enrolled if HCV RNA is the lower limit of quantification.
6. Unresolved toxicities from prior therapy greater than or equal to grade 1 based on CTCAE version 5.0.
7. Received extensive radiotherapy within the last 2 weeks, or received localized radiotherapy or gamma knife surgery with a limited scope of radiotherapy for palliative purposes within the last 1 week.
8. Unable to swallow investigational medication due to intractable nausea and vomiting or chronic gastrointestinal disease.
9. Participation in another interventional clinical trial within 30 days of screening
10. Pregnant or lactating women
11. Unwilling to agree to use a medically acceptable method of contraception from the first dose of investigational drug until 1 month after the last dose.
* Female patients of childbearing potential who are sexually active and their partners must agree to use adequate medically acceptable contraception for the duration of the study and for 1 month after the last dose.
* Male patients who have not undergone a vasectomy must agree to use adequate contraception and are prohibited from providing sperm until 1 month after the last dose of study medication.
* Adequate contraception includes: hormonal contraceptives (subcutaneous fat, injections, oral contraceptives, etc.), intrauterine devices (IUD, intrauterine device or IUS, intrauterine system), sterilization of you or your partner (vasectomy, tubal ligation, etc.).
12. Failure to provide 20 unstained slides (if additional biopsies are not available from the patient, participation in the study may be possible after discussion with the study coordinator).
13. Those who are inappropriate to participate in the study for other reasons (e.g., ethically or because it may affect the outcome of the study) as judged by the principal investigator.
