Glial Cell Line-Derived Neurotrophic Factor (GDNF) is a protein that has been investigated for its potential to treat various neurodegenerative diseases, including Parkinson’s disease. It is a member of the TGF-β (Transforming Growth Factor-beta) superfamily of cytokines and is essential for the development and maintenance of the nervous system. GDNF has been shown to play a role in the survival and differentiation of dopaminergic neurons in the brain, which are the neurons that degenerate in Parkinson’s disease. Despite promising preclinical results, however, clinical trials of GDNF have so far yielded mixed and inconclusive results. Research into GDNF is ongoing, and further studies are needed to determine its potential use as a therapeutic agent.