The phase III open study enrolled 170 chemically naive, female, breast cancer patients, who received Zarzio (Sandoz GmbH), at a dose of 300 mg or 480 mg administered via the SC route. Patients were undergoing four cycles of doxorubicin and docetaxel (Taxotere) chemotherapy, and were therefore at high risk for severe neutropenia (low white blood cell count in the blood causing reduced host defence).

Efficacy

The mean duration of severe neutropenia with Zarzio was 1.8 days in cycle 1, compared to (historically) up to 7 days without growth factor. Over the four cycles, this was comparable (or lower) than historical data with the reference product, Neupogen (Amgen GmbH).

The incidence of febrile neutropenia in cycle 1 was 7.6% compared with 17.5% without growth factor. This also compared well with the reference product.

In clinical practice filgrastim is provided as pre-filled syringes of 300 mg or 480 mg. The corresponding individual doses therefore ranged from 3.7mg/kg to 8.4 mg/kg. Analysis of the effects in patients stratified by dose per kg body weight demonstrated similar therapeutic efficacy.

Safety

Zarzio was well tolerated in cancer patients. The overall incidence of adverse events was within the range of the reference product. Transient reversible increases in aspartate aminotransferase and lactate dehydrogenase were in the range of those previously reported with rhG‑CSF.

Analysis of the effects in patients stratified by dose per kg body weight also demonstrated a comparable safety profile for all dose groups.

Immunogenicity

Development of antidrug antibodies is of major concern during safety assessment of biopharmaceuticals. In clinical studies using Neupogen an incidence rate of 3% (11 patients out of 333) of non-neutralising antibodies has been reported. In the phase I studies and the phase III study of Zarzio none of the 316 subjects developed anti-rhG-CSF antibodies.

This study confirmed that the administration of Zarzio was efficacious and safe, triggering no immunogenicity.

(link to Development of a new biosimilar filgrastim product (Zarzio) and Phase I studies of a new biosimilar filgrastim product (Zarzio) published)

Reference:

Gascon P, Fuhr U, Sorgel F et al. Development of a new G-CSF product based on biosimilarity assessment. Ann Oncol. 2009 Dec 17. doi: 10.1093/annonc/mdp574