In my opinion, although hoping for the best, we should be cautious about how we interpret these results.

The Cure Parkinson's Trust report says [1]:

"The participants did not report noticeable improvements in their symptoms during the trial period beyond what their standard medication already did for them."

Although progression is usually slow in PD, one would still have expected some comments along the lines of "I've had a good year". This raises the question of whether the MDS-UPDRS is the correct measure to use for assessing the efficacy of progression slowing drugs. In my opinion, there is too low a priority given to non-motor symptoms.

The "Science of Parkinson's disease" gives graphs of the results [2]. Even at face value, the size of the changes are small: after 48 weeks, the difference between the placebo group and the Exenatide group is only about 4 points on the MDS-UPDRS part III scale, motor examination [3]. Part III adds 33 scores each of 0, 1, 2, 3, 4, giving a total score of from 0 (good) to 132 (bad).

The Exenatide graph show a steep improvement from the baseline at time 0 to the next measure after 12 weeks of taking the drug, a fairly flat performance during weeks 12 to 48 where the drug is taken throughout, followed with a decline in performance once the drug is removed. This may indicate not a slowing of progression but, rather, a symptomatic effect.

Tupelo3, I'll be grateful if you could point me to the full paper.

References:

[1] Cure Parkinson's Trust | Breaking News: Diabetes Drug Shows Potential as Disease-Modifying Therapy for Parkinson’s

[2] Exenatide: One step closer to joblessness! | The Science of Parkinson's disease

[3] Rehab Measures - Movement Disorder Society sponsored Unified...

John