Patients Switched Between Biosimilar and Reference Filgrastim With No Clinically Meaningful Difference

A study presented at the 2017 Annual Meeting of the American Society of Clinical Oncology (ASCO) found that there was no clinically meaningful difference when patients with breast cancer were switched from treatment with reference filgrastim (Neupogen) to EP2006, the first FDA-approved filgrastim biosimilar (marketed as Zarxio).

The phase 3, randomized, double-blind registration study sought to assess the safety and efficacy of alternating treatment with EP2006 and the reference filgrastim for the prevention of severe neutropenia in patients undergoing myelosuppressive chemotherapy in the neoadjuvant setting.

The study comprised 218 patients who received the reference filgrastim or its biosimilar together with 6 cycles of chemotherapy. The patients were randomized into 4 arms; 2 arms received only 1 of the treatment products, either the EP2006 or the reference, and did not switch treatments. 2 arms received alternating treatments of the biosimilar and reference product (or vice versa) over cycles 1 to 6. The analysis compared the safety and efficacy of the 2 treatments between the pooled switched groups and the unswitched reference group over cycles 2 to 6. The researchers pre-defined a margin with a 95% confidence interval (CI), to demonstrate non-inferiority of the biosimilar product in febrile neutropenia (FN) rates between the switched an unswitched groups, for treatment cycles 2 to 6.

A total of 107 patients switched treatment, while 51 patients received the reference product in all cycles. Baseline characteristics were similar between the 2 treatment groups. The incidence of FN for the switched group was 3.4%, compared with 0% in the group that received the reference product alone (95% CI, range -9.65 to 4.96), a rate that fell within the pre-defined margin. Only 1 patient (switched group) was hospitalized due to FN. Infections were noted in 9.3% of the switched group versus 9.9% of the reference group. Treatment emergent adverse events were reported in 42.1% of patients in the switched group versus 39.2% of the reference group. Musculoskeletal and connective tissue disorders related to treatment with filgrastim were noted in 35.5% of the switched group versus 39.2% of the reference group. No patients developed anti-drug antibodies during the study period.

The researchers concluded that there was no evidence of clinically meaningful differences when patients undergoing treatment for breast cancer were switched between biosimilar filgrastim and reference filgrastim, or vice versa.