Background: Therapeutic options for metastatic poorly differentiated neuroendocrine carcinoma (NEC) after prior platinum‐based chemotherapy are unknown. Camptothecin analogs, like topotecan and irinotecan, are approved chemotherapy in small cell lung cancer (SCLC). NEC is considered to have similar biological behavior to SCLC. The aim of this study was to analyze the efficacy of TLC388 (Lipotecan) Hydrochloride, which is a novel camptothecin analog, in pretreated metastatic NEC patients. Methods: This single-arm, 2-stage, phase 2 clinical trial was conducted at 4 community and academic centers in Taiwan. Patients aged 20 years or older enrolled between July 2015 to May 2018 had confirmed metastatic NEC with prior systemic therapy with etoposide plus cisplatin. Patients received intravenous 40 mg/m² of TLC388 on Days 1, 8 and 15 of a 28-day cycle until disease progression or unacceptable toxic effects. Results: twenty-three patients with a median age of 61 (range, 44-73) years, including 18 men (78%), were enrolled. Patients received a median of 2 (range, 0-6) treatment cycles. Among 20 evaluable patients, three patients showed a stable disease and no patient a complete or partial remission, resulting in a disease control rate of 15%. Median PFS was 1.8 (95% CI, 0.4-15) months and median OS was 4.3 (95% CI, 1.7-15) months. The most common treatment-related hematologic adverse events at grade 3 or higher were leukopenia (22.7%), anemia (31.8%), and thrombocytopenia (18.2%), respectively. Conclusions: TLC388 shows modest antitumor activity in metastatic NEC. Clinical trial information: NCT02457273