Background8MW0511 is a novel, long-acting recombinant human granulocyte-colony stimulating factor (G-CSF) produced by the fusion of the N-terminus of highly active modified G-CSF with the C-terminus of human serum albumin (HSA). Current G-CSF treatments require frequent administration and have limitations in efficacy and convenience, highlighting the need for a longer-acting alternative with fewer injections and improved outcomes. Here, we report a phase III study comparing the efficacy and safety of 8MW0511 with those of the approved PEG-rhG-CSF.MethodsPatients with breast cancer were randomized at a 2:1 ratio to receive either 8MW0511 or PEG-rhG-CSF after four cycles of standard chemotherapy with docetaxel and cyclophosphamide, with or without doxorubicin. The primary efficacy endpoint was to evaluate the duration of severe neutropenia (DSN) between 8MW0511 and PEG-rhG-CSF during the first cycle.ResultsEligible patients were enrolled and randomly assigned to receive either 8MW0511 (n = 328) or PEG-rhG-CSF (n = 164). During the first cycle, the average DSN was 0.24 days for the 8MW0511 group and 0.25 days for the PEG-rhG-CSF group. The mean difference in DSN [-0.02 days (95% Confidence interval: -0.12, 0.08)] met the primary study endpoint. During cycles 2-4, the DSN results were consistent with those of cycle 1. The incidence of grade 4 neutropenia was lower in the 8MW0511 group than in the PEG-rhG-CSF group across all chemotherapy cycles. The incidence of febrile neutropenia (FN) across all cycles showed no significant difference between the two groups. Other efficacy endpoints and adverse events were comparable between the two groups.ConclusionsThe study findings confirm that 8MW0511 is not inferior to PEG-rhG-CSF in terms of efficacy and shows comparable safety profiles. Additionally, 8MW0511 has the potential to significantly decrease the duration of chemotherapy-induced neutropenia, along with a reduction in the occurrence of FN and severe neutropenia.