Safety and feasibility of long term administration of recombinant human granulocyte-colony stimulating factor in patients with amyotrophic lateral sclerosis

• We monitored six ALS patients up to three years.
• Monthly administration of G-CSF was safe and feasible.
• Mobilization efficiency was highly divergent between individual patients.
• Loss of primitive erythroid precursors was seen in all patients.

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neuronal disease resulting in a loss of the upper and lower motor neurons and subsequent death within three to four years after diagnosis. Mouse models and preliminary human exposure data suggest that the treatment with granulocyte-colony stimulating factor (G-CSF) has neuro-protective effects and may delay ALS progression. As data on long-term administration of G-CSF in patients with normal bone marrow (BM) function are scarce, we initiated a compassionate use program including 6 ALS patients with monthly G-CSF treatment cycles. Here we demonstrate that G-CSF injection was safe and feasible throughout our observation period up to three years. Significant decrease of mobilization efficiency occurred in one patient and a loss of immature erythroid progenitors was observed in all six patients. These data imply that follow-up studies analyzing BM function during long-term G-CSF stimulation are required.