Clinical trials in neurological disorders using AAV vectors: promises and challenges.

Currently, there are five phase I clinical trials of recombinant adeno-associated viral vectors for the treatment of neurological disorders that are approved or likely to be approved shortly. Two trials are testing different strategies to treat Parkinson's disease (PD), the third trial is aimed at treating Canavan's disease, a pediatric leukodystrophy, the fourth trial targets Alzheimer's disease (AD), and the fifth will attempt to target the lysosomal storage disorder, Batten's disease. All four clinical trials rely on the de novo expression of an enzyme or a trophic factor to correct neuropathology. Ironically, the theories used to choose enzymes for the two PD trials were widely divergent, whereas the enzymatic strategy used for one of the PD trials and the Canavan's trial have remarkable similarities. Other gene therapy treatment strategies for PD and other disorders, such as amyotrophic lateral sclerosis, are also on the horizon.