Abstract 4686: Efficacy and safety of efbemalenograstim alfa as primary prophylaxisfor concurrent chemo-radiotherapy induced neutropenia

Background: Concurrent chemo-radiotherapy (CCRT) occupies a pivotal position in the therapeutic management of various malignant tumors and frequently causes significant hematologic toxicity, particularly leukopenia and neutropenia. Nonetheless, granulocyte-macrophage colony-stimulating factor (GM-CSF) is not recommended for preventing CCRT, while granulocyte colony-stimulating factor (G-CSF) is seldom investigated in this setting. This study aims to evaluate the effectiveness and safety of efbemalenograstim alfa, a novel long-acting G-CSF, as a primary prophylaxis during CCRT. Method: This multicenter, open-label, randomized controlled trial will enroll 120 patients who are scheduled to undergo definitive CCRT for malignancies, including non-small cell lung cancer, small cell lung cancer, esophageal cancer, nasopharyngeal carcinoma, head and neck squamous cell carcinoma, or cervical cancer. Patients will be randomized 1:1 to study group or control group. In the study group, patients will receive efbemalenograstim alfa approximately 48 hours post-chemotherapy. In the control group, patients will receive rhG-CSF upon an absolute neutrophil count (ANC) drop below 1.0 × 109/L. Patients who developed febrile neutropenia (FN) or dose-limiting neutropenic event in the control group will receive efbemalenograstim alfa in the subsequent chemotherapy cycles. The primary endpoint is the incidence of 3/4 grade neutropenia (ANC < 1.0 × 109/L) throughout the CCRT period. Result: Efbemalenograstim alfa administration significantly reduced the incidence of grade 3/4 neutropenia during the CCRT period. Four patients (12.90%) in the efbemalenograstim alfa group experienced grade 3/4 neutropenia, compared to 14 (45.16%) in the control group, resulting in a difference of -32.26% (90% CI: -49.20%, -13.66%, p= 0.0035). The incidence of grade 3/4 neutropenia was 9.68% (study group) vs 45.16% (control group) (p=0.0009) across first chemotherapy cycle, and 3.23% (study group) vs 16.13% (control group) (p=0.0881) across second cycle. Efbemalenograstim alfa administration also resulted in shorter duration of grade 3/4 neutropenia, with a median duration of 0 day (IQR: 0-0) in study group and 0 day (IQR: 0-5) in control group (p=0.008). The depth of ANC nadir is higher in study group than that in control group (3.19 (0.26-8.45) × 109/L vs 1.00 (0.06-4.43) × 109/L, p < 0.001), the mean difference was 2.10 (1.39, 2.71) × 109/L. Efbemalenograstim alfa was well-tolerated, as no≥3 grade treatment-related adverse event (TRAE) was reported in both group. The most common treatment-emergent AEs in study group included thrombocytopenia (48.39%), anemia (45.16%) and hypokalemia (35.48%). Conclusion: Primary prophylaxis with efbemalenograstim alfa provide effective neutrophil support to patients undergoing CCRT, with good safety. Citation Format: Yuanyuan Chen, Qiwen Li, Zunbei Wen, Yi Ouyang, Shuzhen Lai, Rong Huang, Minying Li, Xuefang Zhang, Yongling Ji, Chen Wang, Ming Chen. Efficacy and safety of efbemalenograstim alfa as primary prophylaxisfor concurrent chemo-radiotherapy induced neutropenia [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 4686.