The study may suggest that other researchers should be less optimistic about the prospects for treating a range of other conditions with newer weight-loss drugs.

The GLP-1 receptor agonist exenatide failed to meet its primary outcome in a phase III trial of Parkinson's disease patients. Weekly injections of the GLP-1 receptor agonist exenatide (Byetta, Bydureon) did not slow Parkinson's disease progression or improve symptoms, the phase III Exenatide-PD3 trial showed.

I wouldn’t do another study like this unless you learn what is the target,” Dr. David Standaert, a Parkinson’s researcher at the University of Alabama at Birmingham, told