Biosimilar filgrastim, EP2006, and the reference filgrastim, Neupogen, are similar with no clinically meaningful differences in efficacy or safety for the prevention of severe neutropenia in patients with breast cancer receiving (neo)adjuvant myelosuppressive chemotherapy, a new study published online ahead of print in the journal Annals of Oncology has shown.

For the phase 3 trial, researchers enrolled 218 patients with breast cancer. Participants were randomly assigned to receive 1:1:1:1 non-alternating biosimilar or reference filgrastim or alternating treatments during each cycle of biosimilar or reference filgrastim. Patients received 5 µg/kg/day of filgrastim or its biosimilar over six chemotherapy cycles.

Results demonstrated a duration of severe neutropenia of 1.17±1.11 days with the biosimilar product and 1.20±1.02 days with the reference product.

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Researchers found no clinically meaningful differences regarding incidence of febrile neutropenia or infections, hospitalizations due to febrile neutropenia, depth and time of absolute neutrophil count nadir, or time to absolute neutrophil count recovery during all cycles, between the treatment arms.

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In regard to safety, the frequency of adverse events was similar among all four treatment arms.

The findings suggest that biosimilar filgrastim could represent a potential alternative to Neupogen and may ultimately improve access to filgrastim treatment.

In March 2015, the U.S. Food and Drug Administration (FDA) approved Zarxio (filgrastim-sndz), becoming the first FDA-approved biosimilar product.


  1. Blackwell K, Semiglazov V, Krasnozhon D, et al. Comparison of EP2006, a filgrastim biosimilar, to the reference: a phase III, randomized, double-blind clinical study in the prevention of severe neutropenia in patients with breast cancer receiving myelosuppressive chemotherapy. Ann Oncol. 2015. [epub ahead of print]. doi: 10.1093/annonc/mdv281.