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Surufatinib in combination with toripalimab in patients with advanced neuroendocrine carcinoma: Results from a multicenter, open-label, single-arm, phase II trial.

e16199 Background: Patients with advanced neuroendocrine carcinoma (NEC) have a poor prognosis and limited treatment option after first-line treatment. Surufatinib, a multi-kinase inhibitor of VEGFR 1-3, FGFR 1 and CSF-1R, has been approved in patients with advanced or metastatic extra-pancreatic neuroendocrine tumors in China. Toripalimab is a monoclonal humanized IgG4 PD-1 antibody. Surufatinib modulates tumor immune microenvironment and has shown promising antitumor activity in combination with toripalimab in solid tumors, including neuroendocrine tumor and neuroendocrine carcinoma. Herein, we reported the efficacy and safety of surufatinib in combination with toripalimab in a cohort of advanced NEC patients. Methods: The multicenter, open-label, single-arm phase II clinical trial enrolled advanced NEC patients refractory to first-line chemotherapy, and received surufatinib 250 mg once a day orally plus toripalimab 240 mg intravenously on day 1 of a 21-day cycle. The primary end point is objective response rate (ORR) per RECIST 1.1. Results: Twenty-one patients enrolled and received combination therapy. At data cut-off (December 31, 2020), the average treatment cycles were 5.1±3.69 for surufatinib and 5.0±3.68 for toripalimab. Among 20 tumor evaluable patients, 4 patients achieved confirmed PR and 10 patients achieved stable disease. The ORR and disease control rate (DCR) are 20 % (95%CI: 5.7%-43.7%) and 70% (95%CI: 45.7%-88.1%) respectively. The median PFS is 3.94 months (95%CI: 1.31- unknown). OS is not mature till data cut-off. Adverse events (AEs) reported as related to treatment (TRAE) occurred in 100% of patients, of which Grade≥3 TRAEs occurred in 33.3% of patients. The reported Grade≥3 TRAEs were hypertension in 2 (9.5%) patients, and upper abdominal pain, oral mucositis, neutrophil count decreased, leukocyte count decreased, dermatitis, anemia and backache in 1 (4.8%) patient each. Immune related Grade ≥3 AEs, Gamma-glutamyl transpeptidase increased and dermatitis, occurred in 2 (9.5%) patients, respectively. TRAE caused surufatinib or toripalimab interruption occurred in 6 (28.6%) and 4 (19%) patients respectively. There were neither serious AEs nor AEs inducing treatment discontinuations or deaths. Conclusions: As there is no standard second-line treatment, this combination of surufatinib and toripalimab might offer a new promising choice to treat NEC as second-line treatment due to good efficacy and manageable treatment related toxicities. Clinical trial information: NCT04169672.