BDNF and Parkinson disease: PDGF‐BB has also been shown to have comparable neuroprotective effects to brain‐derived neurotrophic factor in human tyrosine hydroxylase‐positive neurons 30 and is being considered a clinical candidate drug for treatment of Parkinson's disease after promising results in relation to restoring dopaminergic neurotransmission and functional recovery in vivo 31, 32.