Although ciliary neurotrophic factor (CNTF), glial-derived neurotrophic factor (GDNF), insulin-like growth factor (IGF-1), and erythropoietin (EPO) improved motor behavior and reduced motor neuron loss and astrocyte/microglia activation in preclinical animal models [66, 67], clinical trials in ALS patients lacked therapeutic efficacy [68]. This evidence concerns the gene GDNF and amyotrophic lateral sclerosis.