CHRONO-MOBILIZE: Chronotherapy of G-CSF for CD34+ Mobilization in Healthy Donors

Healthy donors are commonly mobilized with granulocyte colony-stimulating factor (G-CSF) to collect peripheral blood stem cells for allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the efficiency of mobilization varies among donors, and suboptimal mobilization may require additional collection procedures or rescue strategies. This prospective, multicenter, randomized trial evaluates whether the timing of daily G-CSF administration (morning vs evening) affects the level of circulating CD34+ cells prior to apheresis in healthy donors. Participants will be randomly assigned to receive subcutaneous G-CSF 10 μg/kg once daily for 5 consecutive days either at 08:00 (±15 minutes) or at 20:00 (±15 minutes). The primary endpoint is the peripheral blood CD34+ cell count measured approximately 12 hours after the last G-CSF dose and within 60 minutes before the start of the first apheresis session. Secondary endpoints include collection efficiency and CD34+ yield metrics, the proportion of donors achieving the target CD34+ dose on the first collection day, the need for a second collection day, and donor safety outcomes. The goal of the study is to identify a practical dosing schedule that may improve stem cell mobilization and streamline donor collection procedures.