Sintilimab in Patients with Previously Treated Metastatic Neuroendocrine Neoplasms

This phase I study evaluated the safety and efficacy of sintilimab, a monoclonal antibody PD-1 inhibitor, in treating advanced neuroendocrine neoplasms. Background Neuroendocrine neoplasms (NENs) are a group of diseases that show high heterogeneity but have limited treatment options. This phase I study evaluated the safety and efficacy of sintilimab, anti-PD-1 monoclonal antibody, in treating advanced NENs. Methods We prospectively enrolled patients pathologically diagnosed with NENs after standard treatment failure. Neuroendocrine neoplasms were classified into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine cancers (NECs). Every patient received sintilimab, and response was assessed every 9 weeks. Results Twenty-four patients with a median age of 57.0 years were enrolled from November 2016 to 2017. The median Ki-67 index was 60%. Five patients had NET, 1 had NET G3, 17 had NEC, and 1 had mixed adenocarcinoma-neuroendocrine carcinoma. The most common primary tumor sites were the pancreas and gastrointestinal tract in 7 and 10 patients, respectively. In phase Ia trial, 2 patients received sintilimab 1 mg/kg every 2 weeks, one received 3 mg/kg every 2 weeks, and 21 patients enrolled in the phase Ib trial received 200 mg every 3 weeks. The objective response rate was 20.8% in all enrolled patients and 27.8% in NEC patients. The median progression-free survival was 2.2 and 2.1 months in patients with NET and NEC, respectively. The median OS was not applicable (NA) and 10.8 months (95% CI, 4.3, NA) with NET and NEC, respectively. The duration of response (DOR) was not reached, with a median follow-up time of 20.7 months. Treatment-related adverse events (TRAE) occurred in 17 (70.8%) patients. The most frequent TRAE was thyroid dysfunction (41.7%), and a grade 3 pulmonary infection occurred in 1 patient. The programmed cell death 1-ligand 1 (PD-L1)-positive (tumor proportion score >= 1%) rate was 18.8% (3 out of 16) and the expression of PD-L1 did not correlate with response. Conclusion Sintilimab was well-tolerated and showed encouraging response in NECs. ClinicalTrials.gov Identifier NCT02937116.