GDNF and amyotrophic lateral sclerosis: Robert H. Baloh et al. demonstrated in clinical trials that human neural progenitor cells transduced with GDNF (CNS10–NPC–GDNF) via exogenous transduction of lentivirus differentiated into astrocytes and were safe for 18 ALS patients in a phase 1/2a study (NCT0294388) [28].