The research team, led by senior author Jay S. Schneider, Ph.D.,  Director of the Parkinson's Disease Research Unit and Professor in the  Department of Pathology, Anatomy and Cell Biology and the Department of  Neurology at Jefferson, found that administration of GM1 ganglioside, a  substance naturally enriched in the brain that may be diminished in  Parkinson's disease brains, acted as a "neuroprotective" and a  "neurorestorative" agent to improve symptoms and over an extended period  of time slow the progression of symptoms.
What's more, once the study participants went off the drug, their  disease worsened. The study enrolled 77 subjects and followed them over a  120-week period and also followed 17 subjects who received current  standard of care treatment for comparison.
"The drugs currently available for Parkinson's disease are designed  to treat symptoms and to improve function, but at this time there is no  drug that has been shown unequivocally to slow disease progression,"  said Dr. Schneider. "Our data suggest that GM1 ganglioside has the  potential to have symptomatic and disease-modifying effects on  Parkinson's disease. If this is substantiated in a larger clinical  study, GM1 could provide significant benefit for Parkinson's disease  patients."
Ref : http://www.jns-journal.com/article/S0022-510X%2812%2900581-3/abstract 
Promising drug slows down advance of Parkinson's disease and improves symptoms
