Effect on Patients' Outcomes of a Change to Biosimilar Filgrastim Product in Autologous Stem Cell Mobilization.

Background Following addition of a biosimilar filgrastim product to the formulary, sites in the authors' provincial health authority transitioned from using the originator filgrastim to the biosimilar for autologous stem cell mobilization. Objective To assess the effect on patient outcomes of a universal change to use of the biosimilar filgrastim in stem cell mobilization. Methods This retrospective pre-post study included patients undergoing autologous stem cell mobilization at 2 cancer hospitals in Alberta, Canada, between July 1, 2018, and November 30, 2019. Clinical outcomes were investigated for patients treated with a granulocyte colony-stimulating factor (biosimilar or originator product) for mobilization before stem cell transplant, approximately 6 months before and after the defined date of product change. Results In total, 102 patients were treated with the originator product and 101 patients with the biosimilar. Effectiveness was similar between the originator and biosimilar products, with 98% successful harvest of stem cells in all patients treated. Independent t tests showed no statistically significant differences between patients receiving the originator and those receiving the biosimilar in terms of time from mobilization to collection (difference of means -0.9 days, 95% confidence interval [CI] -2.12 to 0.32), time for neutrophil engraftment (difference of means 0 days, 95% CI -0.36 to 0.36), time for platelet engraftment (difference of means 1 day, 95% CI -0.55 to 2.55), average length of stay (difference of means -0.7 day, 95% CI -2.71 to 1.31), and CD34+ value (difference of means -1 × 106/kg body weight, 95% CI -2.11 to 0.11). A 98% rate of conversion to use of the biosimilar filgrastim was achieved, with an estimated annual drug-cost saving of $67 500. Conclusions In this pre-post study, changing to the biosimilar product from the originator maintained clinical effectiveness outcomes while decreasing overall drug expenditures. A well-planned change to the biosimilar product, executed in conjunction with clinician consultation and monitoring of effectiveness outcomes, can ensure appropriate patient therapy while significantly improving the uptake of biosimilars and decreasing expenditures for biologic drugs.