Efficacy and Safety Evaluation of Tarlatamab in Advanced Extrapulmonary Neuroendocrine Carcinoma Patients

Inclusion Criteria: \- 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, esophagus, 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) Exclusion Criteria: * Symptomatic central nervous system (CNS) metastases: • Subjects with treated brain metastases are eligible provided the following criteria are met: * Subject is asymptomatic from brain metastases * Whole brain radiation or surgery was completed at least 2 weeks prior to first dose of study treatment (stereotactic radiosurgery completed at least 7 days prior to first dose of study treatment) * Any CNS disease is clinically stable, subject is off steroids for CNS disease for at least 5 days (unless steroids are indicated for a reason unrelated to CNS disease), and subject is off or on stable doses of anti-epileptic drugs at least 14 days prior to first dose of study treatment • Subjects with untreated brain metastases that are asymptomatic and do not require corticosteroids, nor local therapy per investigators standard of practice are allowed Diagnosis or evidence of leptomeningeal disease. Prior history of immune checkpoint inhibitors resulting in: * Any severe or life-threatening immune-mediated adverse event, History of immune-mediated encephalitis or other immune-mediated CNS event (any grade) * Grade ≥ 2 immune-mediated recurrent pneumonitis, Infusion-related reactions leading to permanent discontinuation of immunotherapy agent Exception: Subjects with a history of immune checkpoint inhibitor-induced endocrinopathy which is clinically stable on replacement therapy. * Active autoimmune disease that has required systemic treatment (except replacement therapy) within the past 2 years or any other diseases requiring immunosuppressive therapy while on study. * History of solid organ transplantation. * History of other malignancy within the past 2 years, with the following exceptions: * low-risk malignancy treated with curative intent and with no known active disease present for ≥ 1 year before enrollment and believed to be at low risk for recurrence per investigator discretion. * adequately treated non-melanoma skin cancer or lentigo maligna without evidence of disease, cervical carcinoma in situ without evidence of disease, breast ductal carcinoma in situ without evid