Introduction: Poor CD34 + cells mobilization in allogeneic donors could affect transplant outcome. In a subgroup of patient mobilization with granulocyte colony-stimulating factor (G-CSF) alone is unsatisfactory, and Plerixafor could be used to enhance CD34 + cells release from bone marrow niche. Materials and methods: We conducted a retrospective single-center, cohort study on healthy allogeneic donors both related and unrelated, treated by Udine Transfusion Center over the last 10 years (2012–2022). In the 195 allogeneic donors treated we analyzed age, sex, body weight, BMI, comorbidities, G-CSF dosage and even baseline white blood cell count as possible predictor of insufficient CD34 + cells mobilization on day 5. In the subgroup of related donors we evaluated even baseline CD34 + cells (measured before mobilization start). Processed donor blood volume, collection efficiency and apheresis product were examined. Additionally a comparative analysis was conducted between G-CSF alone treated donors and poor mobilizing ones, in which Plerixafor was administered at a dose of 0.24 mg/kg as a pre-emptive or rescue agent. Results: In 9 donors, due to poor mobilization (defined as CD34 + < 20/μL or estimated yield < 1 ×106 kg/recipient body weight), the use of plerixafor was necessary. PLX at a dose of 0.24 mg/kg was administered 5 h before collection, inducing an average increase of 5.1 (1.7–12.6) in CD34 + circulating cells. In this subgroup of patients, BMI and weight were significantly lower (p = 0.03). Interestingly, baseline CD34 + cells (measured before the onset of mobilization) also seems to predict poor mobilization (p = 0.003). In donors additionally treated with Plerixafor compared to those who received G-CSF alone, collection efficiency was higher (p = 0.02) and CD34 + cells collected were comparable (p = 0.2). Side effects related to the administration of plerixafor, if they occurred, were well tolerated. Conclusions: Plerixafor is a safe and effective drug in the rescue and prevention of poor mobilization. New prospective studies on allogeneic donors should be performed to increase the treatable population to avoid inadequate collection and mobilization. New laboratory predictors such as baseline CD34 + cells should be investigated in larger cohorts and then used as early screening.
