Purpose: The US Food and Drug Administration (FDA) approved the biologic medication filgrastim to mobilize hematopoietic progenitor cells (HPCs) into the peripheral blood for collection by leukapheresis for hematopoietic stem cell transplant (HSCT). The FDA-approved biosimilar tbo-filgrastim is currently used off-label for this indication in both autologous and allogeneic HSCT at the Tennessee Valley Healthcare System. This study compares the efficacy of filgrastim and tbo-filgrastim for these indications.
Methods: This was a retrospective, single center, observational cohort study approved by the Institutional Review Board. Patients were identified from the bone marrow transplant clinic and included in data collection if they received filgrastim or tbo-filgrastim for HPC mobilization between September 1, 2012 and September 1, 2018. The primary outcome was the proportion of patients with a CD34+ count > 15 ×103 cells/uL on day 4 of filgrastim or tbo-filgrastim mobilization for autologous transplantation. Secondary outcomes were the proportion of donors with a CD34+ count > 15 ×103 cells/uL on day 4 of filgrastim or tbo-filgrastim mobilization for allogeneic transplantation and the use of plerixafor in both patient populations.
Continuous data were described using mean and standard deviation. Associations between independent and dependent variables were assessed using t-tests for continuous variables and Fishers Exact tests for dichotomous variables.
Results: A total of 469 patients were identified for study inclusion; 367 underwent mobilization for autologous and 102 for allogeneic HSCT. Primary outcome was achieved in 47.5% of patients who received filgrastim compared with 50.24% who received tbo-filgrastim (P=0.67). There was no difference in patients eligible for collection on day 4 of filgrastim or tbo-filgrastim administration in the allogeneic HSCT population (97.6% vs 100% respectively; P=0.41). No statistically significant differences were identified in the number of patients requiring plerixafor use in the autologous or allogenic HSCT populations.
Conclusion: The use of the biosimilar tbo-filgrastim for mobilization in either autologous or allogeneic HSCT has comparable outcomes to that of the biotherapeutic reference product filgrastim at a reduced cost.