Parkinson's drugs: new hope or false dawn?

Anyone with Parkinson’s - or, I imagine any other long term degenerative condition - soon learns how to read the news. By which I mean we become less likely to crack open a bottle or do a jig when we read excited headlines about some wonder drug or new treatment that might transform our lives.

This week’s headlines were about lixisenatide, one of a class of drugs known as GLP-1 agonists which as well as treating diabetes have been shown to have beneficial impacts on the brain. “Diabetes drug offers hope to Parkinson’s sufferers,” said the Financial Times. The Guardian told us “Diabetes drug may slow progression of Parkinson’s, say researchers”. Taking a different tack, the New York Times said “An Ozempic Relative Slowed Parkinson's Disease in a Small Study.” All three stories were perfectly fair accounts of a trial which showed that a drug used for weight loss as well as diabetes treatment slowed down the progression of motor symptoms - things like a tremor or difficulty walking - while those given a placebo continued to see their symptoms worsen.

But how much “hope to Parkinson’s sufferers”, in the words of the FT, does the drug offer, and how soon? We have learned to look at just where a drug is in the trial process, how many people were involved, whether it was aimed at a particular group of patients, and what sort of side effects it produced.

This was a phase 2 double-blind study - so well beyond the initial “it works on animals” phase, but still quite a way from the finishing line which is a phase 3 trial. Two other drugs, another diabetes GLP-1R agonist exenatide and a cough mixture ambroxol are already heading into phase 3, and if they are successful then the regulators could approve their use as the first drugs to slow the progression of Parkinson’s

But it is worth noting that Exenatide’s successful phase 2 results were announced in 2017 and seven years on it still hasn’t made it through phase 3. Hopefully lixisenatide’s trials won’t be slowed down by another global pandemic, but don’t expect news in a big hurry. For one thing, the researchers will need to recruit far more trial participants than the 156 who took part in phase 2.

There will also need to be a close eye on side effects - 46% of phase 2 participants experienced nausea, with 13% vomiting. The drug was tested on people in the early stages of Parkinson’s, so if and when it is approved it may not be suitable for people who were diagnosed a while ago. If such an outcome is five years away (it always seems to be five years away!) I will be 10 years into my Parkinson’s journey and perhaps not a suitable candidate.

Cure Parkinson’s put out a measured statement about the lixisenatide trial, which it helped to fund along with exenatide’s trials, accepting there was much more work to be done but pointing out that there was now a body of evidence suggesting that GLP-1R agonists could have a positive effect for people with Parkinson’s. (Full disclosure - I am a Patron of the charity).

There is one more hurdle that has to be cleared by lixisenatide - who will make it? It is no longer seen as one of the top diabetes drugs and its manufacturer Sanofi has discontinued production. So if it does turn out to be a Parkinson’s wonder drug, another firm will have to step in.

A cautious welcome then for this week’s news - but don’t hold the front page. That can wait for the results of exenatide’s phase 3 trial, expected later this year. If that is successful, then it really will be time to break out the bubbly,