Background:High-grade neuroendocrine neoplasms (NENs) have limited treatment options following first-line platinum-based chemotherapy, often resulting in poor clinical outcomes. Dual immune checkpoint blockade targeting CTLA-4 and PD-1 offers a synergistic approach by enhancing T-cell activation and amplifying anti-tumor immune responses. This study evaluates the efficacy and safety of HBM4003, a novel fully human anti-CTLA-4 monoclonal antibody, in combination with toripalimab, a PD-1 inhibitor, in patients with high-grade, refractory NENs.
Methods:This multicenter, open-label, phase II study enrolled patients with neuroendocrine carcinomas (NECs), grade 3 NETs (NETs G3), and mixed neuroendocrine-non-neuroendocrine neoplasms (MiNENs) who had progressed on first-line therapy. Patients received HBM4003 at either 0.3 mg/kg or 0.45 mg/kg in combination with toripalimab (240 mg) every three weeks. The primary endpoint was the objective response rate (ORR). The study was registered on ClinicalTrials.gov (NCT05167071).
Findings:Between December 2021 and May 2024, a total of 29 patients were enrolled (NECs, n = 22; NETs G3, n = 3; MiNENs, n = 4). All patients had previously undergone chemotherapy, with 11 receiving ≥2 lines of therapy. Thirteen (13) patients had lung metastasis and 18 had liver metastasis. Patients were assigned to the HBM4003 0.3 mg/kg cohort (n = 13) or the 0.45 mg/kg cohort (n = 16), with 26 patients forming the efficacy analysis set. The overall ORR was 34.6% (95% confidence intervals [CI], 17.2-55.7), and the disease control rate (DCR) was 65.4% (95% CI, 44.3-82.8). Median progression-free survival (PFS) and overall survival (OS) were 4.0 months (95% CI, 1.6-5.1) and 21.8 months (95% CI, 16.7-not estimated [NE]), respectively. For 19 NEC patients in the efficacy analysis set, the ORR and DCR were 36.8% (95% CI, 16.3-61.6) and 68.4% (95% CI, 43.4-87.4), respectively. The median PFS was 4.0 months (95% CI, 1.6-5.4), while the median OS was not reached (95% CI, 13.5-NE). Of the 29 NEN patients receiving at least one dose of study treatment, all patients experienced at least one treatment-related adverse event (TRAE), with 10 (34.5%) experiencing grade ≥3 TRAE and eight (27.6%) experiencing grade ≥3 immune-related adverse events.
Interpretation:HBM4003 combined with toripalimab demonstrated promising anti-tumor activity and manageable safety in patients with refractory NENs, supporting further investigation of this combination therapy.
Funding:This study was funded by Harbour BioMed (Shanghai) Co. Ltd.
Keywords:HBM4003; Immune checkpoint inhibitors; Neuroendocrine neoplasms; Toripalimab.

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乐备实（上海优宁维生物科技股份有限公司旗下全资子公司），是国内专注于提供高质量蛋白检测以及组学分析服务的实验服务专家，自2018年成立以来，乐备实不断寻求突破，公司的服务技术平台已扩展到单细胞测序、空间多组学、流式检测、超敏电化学发光、Luminex多因子检测、抗体芯片、PCR Array、ELISA、Elispot、PLA蛋白互作、多色免疫组化、DSP空间多组学等30多个，建立起了一套涵盖基因、蛋白、细胞以及组织水平实验的完整检测体系。

 
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