PURPOSE: Evaluate the safety and efficacy of efbemalenograstim alfa for reducing the risk of febrile neutropenia in breast cancer patients undergoing myelosuppressive chemotherapy. METHODS: A phase III, randomized, double-blind, placebo-controlled study was conducted. A total of 122 subjects received up to 4 cycles of TA chemotherapy (75 mg/m2 docetaxel + 60 mg/m2 doxorubicin). Patients were randomized in a 2:1 ratio to subcutaneously inject a single 20 mg of efbemalenograstim alfa or placebo on day 2 of cycle 1, and all subjects received efbemalenograstim alfa on day 2 of cycles 2, 3, and 4. Duration of severe (grade 4) neutropenia (DSN), depth of neutrophil nadir, incidence of febrile neutropenia (FN), time to neutrophil recovery, and safety information were recorded. RESULTS: For the primary endpoint, the mean DSN in cycle 1 was 1.3 days and 3.9 days for efbemalenograstim alfa and placebo respectively (95% CI, 2.3, 3.4). As the lower bound of the 95% CI was > 0, superiority of efbemalenograstim alfa over placebo can be declared. In addition, the incidence of FN in Cycle 1 was lower in efbemalenograstim alfa group than in placebo group (4.8% vs. 25.6%; p = 0.0016). Patients in the efbemalenograstim alfa group required less intravenous antibiotics (3.6% vs. 17.9%; p = 0.0119). Most adverse events were consistent with those expected for breast cancer patient receiving TA chemotherapy. CONCLUSION: Efbemalenograstim alfa is effective and safe for significantly decreasing the duration of severe neutropenia and the incidence of febrile neutropenia in breast cancer patients who are receiving TA chemotherapy. TRIAL REGISTRATION: NCT02872103, August 19, 2016.