A Phase III Randomized Equivalence Study of Biosimilar Filgrastim versus Amgen Filgrastim in Patients Receiving Myelosuppressive Chemotherapy for Breast Cancer

Background: Filgrastim was developed to treat chemotherapy-induced neutropenia. This phase III study was designed to demonstrate bioequivalence of Amgen filgrastim and a biosimilar filgrastim developed by Hospira (Study GCF071; sponsored by Hospira). Patients and Methods: Breast cancer patients suitable for treatment with doxorubicin and docetaxel in the neoadjuvant/adjuvant or first-line metastatic setting were enrolled at 37 European centers. Patients were randomized (2: 1) to receive Hospira filgrastim or Amgen filgrastim, after the end of chemotherapy. Filgrastim (5 mu g/kg/day) was administered under double-blind conditions. Primary endpoint to demonstrate bioequivalence was duration of severe neutropenia (DSN) in cycle 1. Results: 184 patients were randomized to Hospira filgrastim and 95 to Amgen filgrastim. Mean DSN in cycle 1 was similar with Hospira filgrastim (1.6 days; n = 165) and Amgen filgrastim (1.3 days; n = 85), meeting predefined criteria for bioequivalence. Secondary endpoints supporting bioequivalence included mean time to absolute neutrophil count recovery and incidence of febrile neutropenia. The most common treatment-related adverse event with Hospira filgrastim was grade 1-2 bone pain. Conclusions: Hospira filgrastim and Amgen filgrastim are bioequivalent in efficacy with similar safety profiles. Hospira filgrastim may be useful for the prophylaxis of complications related to neutropenia caused by chemotherapy.