My only quibble is the use of the word "stopped" (i.e. it's a bit too strong). In the title of the article they use the words "may" and "slow".

Also, in the abstract of the research paper they say [1]:

"Whether exenatide affects the underlying disease pathophysiology or simply induces long-lasting symptomatic effects is uncertain."

[1] Exenatide once weekly versus placebo in Parkinson's disease: a randomised, double-blind, placebo-controlled trial, Athauda et al., The Lancet, 03 August 2017.
http://www.thelancet.com/journals/la...585-4/fulltext