Most new drugs that begin the clinical trial process do not get approved. Istradefylline, a potential Parkinson's drug, met that fate late last week when the U.S. Food and Drug Administration (FDA) refused to approve it.
The FDA saw insufficient evidence that it was effective at helping people with Parkinson's disease. If it's manufacturer, Kyowa Pharmaceuticals, can provide more data about its benefits, it may still be considered for future approval.
Istradefylline is a messenger chemical similar to dopamine. It appears to connect with the A2A neuroreceptor. Rather than replacing or imitating dopamine, it opens another communication link to the brain. It helps nerve and brain signals bypass the damaged dopamine system.
Sources:
Pharmaceutical Business Review, February 2008