GCSF with sustained activity has biological efficacy and prolongs the survival of mutant SOD1 mice. Mutant SOD1 mice were treated with pegfilgrastim once a week starting at the age of 12 weeks. Plasma concentration of GCSF remained elevated multiple days after a single injection of 300 μg/kg (A) but returned back to baseline at day 7 before the next dosage (data was obtained from 33 mice, 1-2 blood samples/mouse). This occurred in a similar manner after the first dosage (A, open squares) as well as after the long-term pegfilgrastim treatment (A, black squares). Pegfilgrastim elevated the levels of stem cells (B, p <0.01, n = 11) and granulocytes (C, p <0.01, n = 11) after the first dosage, as analyzed four days after the pegfilgrastim administration, but the mobilization was decreased after prolonged pegfilgrastim treatment (n = 5). Long-term pegfilgrastim treatment increased the survival of mutant SOD1 mice as shown with a Kaplan-Meier survival graph (D, p <0.01, n = 8-9). Pegfilgrastim treatment did not delay the onset of the disease as determined by wire-hang test (E, n = 6) but increased the time from the onset to death (F, p <0.05, n = 4-5). The prolonged survival was accompanied with improved motoric performance in wire-hang test (G, p <0.05, n = 6) when analyzed within 5 weeks after the onset. The first mice died 5 weeks after the onset.