∙ \- Subject has provided informed consent prior to initiation of any study specific activities/procedures.

• Age ≥19 years at the time of signing the informed consent.

• Histologically confirmed relapsed/refractory extra-pulmonary neuroendocrine carcinoma. Neuroendocrine carcinoma includes small cell carcinoma, large cell carcinoma, and mixed histology of neuroendocrine and other histology (e.g., adenoneuroendocrine carcinoma, urothelial carcinoma with neuroendocrine component). In patients with prostate cancer, treatment-emergent neuroendocrine carcinoma (initially adenocarcinoma, but transdifferentiate into neuroendocrine carcinoma after androgen deprivation therapy) will be permitted.

• Cohort 1 (gastrointestinal and pancreaticobiliary cohort): cancers originated from stomach, small intestine, colorectal, pancreas, or bile ducts.

• Cohort 2 (genitourinary cohort): cancers originated from prostate, bladder, ureter, urethra, or kidney.

• Subject has progressed or recurred following 1 platinum-based regimen:

• documented first disease progression must be during or following first-line platinum-based systemic chemotherapy. For patients with prostate cancer, especially in cases with treatment-emergent neuroendocrine carcinoma, platinum-based chemotherapy will not need to be the first line therapy.

‣ patients who received treatment for localized disease who recur are eligible

⁃ patients who received adjuvant Platinum-Etoposide (EP) after resection of their primary tumor who recur are eligible

• Measurable disease as defined per RECIST 1.1 within the 21-day screening period.

• • Screening scans performed as SOC(Standard of Care) and prior to informed consent, may be used to confirm subject eligibility if completed within the 21-day screening period, provided that informed consent for the use of these scans is obtained prior to any transfer of data.

⁃ In patients with prostate cancer, patients without RECIST-defined measurable lesion can be included, if disease can be evaluated with Prostate Cancer Working Group(PCWG)-3 criteria.

• Eastern Cooperative Oncology Group (ECOG) PS(Performance Status) of 0 - 2.

• Minimum life expectancy of 12 weeks.

• Adequate organ function, defined as follows:

• • Hematological function: Absolute neutrophil count ≥ 1.5 x 10\^9 /L Platelet count ≥ 100 x 10\^9/L Hemoglobin \> 9 g/dL (90 g/L)

• • Coagulation function: Prothrombin Time (PT)/International Normalized Ratio (INR) and Partial Thromboplastin Time (PTT) or activated Partial Thromboplastin Time (APTT) ≤ 1.5 x institutional upper limit of normal (ULN) except for subjects undergoing new class anticoagulant therapy (eg, Edoxaban), stable dose for 2 weeks required prior to enrollment.

• • Renal function: estimated glomerular filtration rate (eGFR) based on Modification of Diet in Renal Disease (MDRD) calculation ≥ 30 mL/min/1.73 m\^2 or creatinine clearance ≥ 30 mL/min as determined by Cockcroft-Gault equation (Cockcroft and Gault 1976)

• • Hepatic function: aspartate aminotransferase (AST) and alanine aminotransferase (ALT) \< 3 x ULN (or \<5 x ULN for subjects with liver involvement) total bilirubin (TBL) \<1.5 x ULN (\<2 x ULN for subjects with liver involvement) (except participants with Gilbert syndrome who must have total bilirubin \<3.0 mg/dL)

• • Pulmonary function: no clinically significant pleural effusion. Pleural effusion managed with indwelling pleural catheter (eg, PleurX) are allowed baseline oxygen saturation \>90% on room air

• • Cardiac function: cardiac ejection fraction ≥50%, no clinically significant pericardial effusion as determined by an echocardiogram (ECHO) or multigated acquisition (MUGA) scan, and no clinically significant electrocardiogram (ECG) findings Provision of evaluable tumor samples for central testing (archival or in-study biopsy)