Same‐day rescue plerixafor during leukapheresis is safe and effective in allogeneic donors suboptimally responding to granulocyte colony‐stimulating factor mobilization

Abstract Background Plerixafor (P) is a rescue mobilization agent given to improve circulating CD34+ for peripheral blood stem cell (PBSC) collection in donors with inadequate response to granulocyte colony‐stimulating factor (G‐CSF, [G]). In this study, we evaluated the impact of immediate plerixafor administration without leukapheresis interruption for the same‐day PBSC collection in G‐mobilized allogeneic donors with pre‐apheresis peripheral blood CD34+ count ≤30/μL. Study Design Retrospective analysis of two‐center data from 10/2023 to 11/2025 was conducted. The study group (G + P) received G‐CSF for 5 days and plerixafor without leukapheresis interruption ( n = 12). The control group (G, n = 24) received 5‐day G‐CSF and had similar median apheresis procedure time as study group. Outcomes were evaluated at early procedure (EP) and late procedure (LP) periods, separated by the timing of the interim PBSC product characterization. Results G + P donors did not experience increased platelet loss or grade 2 or greater adverse reactions in gastrointestinal and immune systems or required day‐2 collection. During the LP period, G + P group had approximately 5.5‐fold increase in median CD34+ cells/L processed/h apheresis ( p < .0001). During the LP period, while G + P group had significant gains in CD34+ yield, there was a significant loss in the control group ( p < .0087). CD34+ collection efficiency was significantly higher in G + P ( p < .0001). All PBSC products from G + P group contained ≥4.5 × 10 6 CD34+/kg recipient while only 63% of controls met this threshold ( p = .016). Conclusions Same‐day rescue plerixafor without leukapheresis interruption in allogeneic donors suboptimally responding to G‐CSF results in safe and efficient leukapheresis collection while preserving PBSC product quality.