Abstract 800: Safety and efficacy of same-day administration of novel long-acting G-CSF efbemalenograstim α in breast cancer patients undergoing cytotoxic chemotherapy

Abstract Background: There is controversy over whether Granulocyte colony-stimulating factor (G-CSF) can be used within 24 h after chemotherapy. Efbemalenograstim α is a novel long-acting G-CSF approved by FDA in 2023. Guard-02 trial (ChiCTR2300078792) was to evaluate the efficacy and safety of efbemalenograstim α for prevention of chemotherapy-induced neutropenia (CIN) within 24 h after chemotherapy. Methods: This was a prospective, multicenter, single-arm, two-stage clinical study. Breast cancer patients received chemotherapy with epirubicin (90 mg/m2) and cyclophosphamide (600 mg/m2) for 4 cycles were enrolled. If less than 9 cases of grade 3-4 neutropenia occurred in 16 patients in first stage, the toxicity was acceptable and more patients would be recruited in second stage. Patients received 20 mg efbemalenograstim α at 24±4 h (d2) after chemotherapy in first cycle and at 4±1 h (d1) after chemotherapy in subsequent cycles. The primary endpoint was incidence of grade 3-4 (ANC <1×109/L) neutropenia in cycle 1-2. The safety profile was evaluated. Results: The incidence of grade 3-4 neutropenia in cycle 1-2 and cycle 1-4 of 16 patients (median age at 51 years, r.35-60) were 25.00% (90% CI: 9.03%-48.44%) and 31.25% (95% CI: 11.02%-58.66%), both lower than that in phase III trial using efbemalenograstim α at 48 ± 4 h (d3) after EC chemotherapy (NCT04174599, whose incidence of grade 3-4 neutropenia in cycle 1-2 and cycle 1-4 were 34.16% and 36.67%). Using efbemalenograstim α within 24 h after chemotherapy was safe, the most frequently adverse event (AE) related to study drug was muscle pain (6.25%). The incidences of AEs were low and no serious adverse event was related to study drug. Conclusions: Using long-acting G-CSF on same-day of chemotherapy was as safe and effective as on d3 of chemotherapy in reducing CIN. In patients with daytime chemotherapy, efbemalenograstim α provides oncologists an alternative for simplifying management of CIN. Citation Format: Shoubing Zhou, Jing Pan, Qiujun Zhang, Wenyu Li, Dandan Hu, Qianyu Zhang, Shikai Hong, Zhengzhi Zhu, Hu Liu, Xudong Zhang, Hua Xie, Yueyin Pan. Safety and efficacy of same-day administration of novel long-acting G-CSF efbemalenograstim α in breast cancer patients undergoing cytotoxic chemotherapy [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 800.