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 μg/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.