At the American Academy of Neurology meeting held in April 2004, physicians and scientists shared the results of their latest research on a wide variety of neurologic disorders. In one of these seminars, researchers from London presented the findings from their two-year study of five patients with Parkinson’s disease who received an experimental treatment called glial cell-line derived neurotrophic factor, or GDNF. (Click here to learn more about GDNF.) The patients, on average, were 54 years old and had had Parkinson’s disease for 19 years. Medication was no longer effective in controlling their symptoms, and, rather than undergoing one of the commonly performed operations for the treatment of PD (pallidotomy or deep brain stimulation), they opted instead to receive GDNF for two years.
 
Both a rating scale (the Unified Parkinson Disease Rating Scale) and an imaging study (fluorodopa PET scanning) showed that the five patients had positive results. The UPDRS scores improved by 40%, whereas scores normally would have gotten worse over this two-year period, and the density of dopamine transporters seen with the PET scanning increased by 60%, which the investigators think means that the dopamine cells had sprouted new nerve endings, a sign of restored health; however, both of these findings could have alternative explanations.
 
The announcement of these results produced cautious optimism among neurologists who specialize in Parkinson's disease. The results must be confirmed by randomized, double-blind, placebo-controlled studies. There is, in fact, such a study currently underway in which more than 350 patients are enrolled. All of these patients have had an operation to implant the drug-delivery pump, but only half are receiving GDNF. Therefore, both patients and their physicians are “blinded” to their treatment status. The results of this study are expected to be announced in the fall of 2004.
 
Even if these forthcoming results are positive, GDNF will not be available for at least several years because of the lengthy approval process. Both the drug and the delivery device need to be separately approved by the Food and Drug Administration; the use of GDNF has not been approved for any condition, and the device has not been approved for delivery directly into the brain. Before it can be approved, GDNF will need to be shown to be not only effective, but also safe for long-term use; to date, the treatment appears to be safe and well tolerated, but more data in more patients will be needed before all of the remaining questions can be answered.