Inclusion Criteria:  Age ≥ 18 years; Histologically confirmed locally advanced and metastatic extrapulmonary neuroendocrine carcinoma; No systematic treatments for neuroendocrine carcinoma are received before enrollment; ECOG ≤ 2; Have at least one measurable lesion according to RECIST version 1.1, and the lesion has not received any local treatments; Absolute neutrophil count ≥ 1.5×109 / L, platelet count ≥ 100×109 / L, hemoglobin ≥ 90 g/L; Have ability to sign a written informed consent.  Exclusion Criteria:  Have surgery or trauma within 4 weeks before enrollment, or are expected to receive surgical treatment; Previous use of HDAC inhibitors; Allergy to related drug components; Have a medical history of immune deficiency diseases, or organ transplantation; Have uncontrolled or significant cardiovascular disease; Abnormal liver function (total bilirubin > 1.5×upper limit of normal); Transaminases (ALT/AST) >2.5×upper limit of normal (>5x upper limit of normal for patients with liver metastases), abnormal renal function (serum creatinine > 1.5×upper limit of normal); Pregnancy ; Have serious diseases that may endanger the safety of patients, or affect patients to complete the research; Any serious mental or cognitive disorder; Patients are currently enrolled in another drug clinical trial within 4 weeks prior to enrollment; Any other condition which is inappropriate for the study in the opinion of the investigators.