Background: G-CSF given as split dose increased the harvested number of CD34+ cells in comparison to a once daily schedule, but the mechanism is poorly understood.
Study design and methods: To investigate the schedule dependency of G-CSF in healthy volunteers with respect to CD34+ cell mobilization, the same dose of G-CSF was applied in four healthy volunteers in two different schedules (once daily vs. split doses twice daily) in a crossover design after a washout period of 3 months. CD34+ cell kinetics in serum were determined as well as G-CSF serum kinetics on Days 1 and 4 after stimulation.
Results: In all volunteers, the twice daily schedule led to a higher CD34+ cell count after 4 days of G-CSF stimulation (median, 94.5 vs. 47/ microL; p = 0.05). On Days 1 and 4, there was a higher peak serum concentration of G-CSF serum level after the once daily application (15,175 vs. 6,859 pg/mL and 7440 vs. 2388 pg/mL, respectively) than after the twice daily schedule. In contrast, after the once daily application the minimum serum level of G-CSF serum level was lower than after the twice daily schedule (663 vs. 1361 pg/mL and 246 vs. 441 pg/mL, respectively). No difference of area under the curve for G-CSF was observed on Days 1 and 4 after G-CSF stimulation.
Conclusion: It is suggested that application of G-CSF twice daily leads to a higher CD34+ cell mobilization owing to a higher minimum serum level and therefore to a more continuous serum baseline level resulting in a more efficient CD34+ cell mobilization.