In a study by scientists at University College London, 46 patients with the neurodegenerative disease were given injections of a drug called IONIS-HTTRx into their spinal fluid. By the end of the trial – the first time the drug has been tested in humans – patients had lowered levels of the harmful protein that causes brain cell damage. The patients tolerated the drug well, without severe side effects, the scientists reported.
It is the first time that this protein – called huntingtin – has been lowered in patients' nervous systems. The greater the dose of the drug patients received, the less huntingtin protein was measured in their spinal fluid. In healthy people, the gene that encodes this protein is involved in brain development. In its mutated form in Huntington's patients, the protein it makes kills brain cells and leads to progressive decline in memory, cognitive ability, behaviour and movement.
'You end up in almost a vegetative state, it's a horrible end,' Peter Allen, one of the early-stage Huntington's patients involved in the trial, told the BBC. 'You know the last day was better than the next one's going to be.'
'For the first time we have the potential, we have the hope, of a therapy that one day may slow or prevent Huntington's disease. This is of ground-breaking importance for patients and families,' Professor Sarah Tabrizi, director of the Huntington's Disease Centre at UCL and leader of the trial, told the BBC.
Neurodegenerative disease researchers not involved in the study have also welcomed the results as a breakthrough. Professor John Hardy, a neurological disease researcher not involved in the study, told the Guardian: 'If I'd have been asked five years ago if this could work, I would have absolutely said no. The fact that it does work is really remarkable.'
However, the drug IONIS-HTTRx will need to be successful in further clinical trials before it could be confirmed as an effective treatment. The details of the study have not yet been published or scrutinised in peer-review, cautions Professor Tara Spires-Jones, UK Dementia Research Institute programme lead and Deputy Director of the Centre for Discovery Brain Sciences at the University of Edinburgh.
'With that caveat in mind, the approach used in this trial has excellent potential to prevent Huntington's disease, and if the next stage of larger trials live up to their promise, this will be a breakthrough,' Professor Spires-Jones said.
The pharmaceutical firm Roche has already paid a $45 million licence fee to develop the drug. If it does become a successful treatment for Huntington's, researchers have suggested that a similar method could work for other neurodegenerative diseases, such as Alzheimer's. Similar drugs targeting the RNA for the faulty amyloid or tau proteins, involved in Alzheimer's, could potentially slow the disease.
'Huntington's alone is exciting enough,' Hardy told the Guardian. 'I don’t want to overstate this too much, but if it works for one, why can’t it work for a lot of them? I am very, very excited.'