Could a new treatment developed by the US pharmaceutical company Lilley mean “the beginning of the end” of Alzheimer’s? Could we even cure the disease some day? These are the types of headlines and questions swirling around after news of a new drug, called donanemab, showed promising results in phase-3 trials at slowing down the decline in cognitive functions and reducing the deterioration in the ability to undertake daily tasks independently.
Alzheimer’s is the most common cause of dementia, accounting for 60-70% of cases. It is not a normal part of ageing, even though it largely affects those over 65. It’s a degenerative disease where symptoms worsen over years, starting with mild memory loss and moving towards the complete loss of ability to recognise loved ones and caregivers, confusion and disorientation between the past and present, and the inability to live independently. It can be heartbreaking for families to watch the deterioration of loved ones who almost become like a different person, with extreme mood and behavioural changes.
The brain science behind Alzheimer’s is complex, but CT and MRI scans suggest that toxic changes occur in the brain, including the abnormal buildups of proteins called amyloid plaques and tau tangles. The damage starts in the parts of the brain essential for forming memories but then spreads throughout the organ, with brain tissue shrinking significantly.
Developing treatments for Alzheimer’s has been a challenge, with almost 20 years passing with no new drugs. But in the last year, two new ones have emerged: donanemab and lecanemab. Neither are cures or magic bullets for the disease, but they do address key symptoms. They target the amyloid proteins that can accumulate in the brain and damage neurons, slowing down the progression of the disease. Lilley claimed in a press release that donanemab slowed mental decline by 35% in a 1,736-person trial.
And while this news is exciting, there are major caveats. One is whether it will ever become available on the NHS. The cost is estimated to be about £20,000 per person per year of treatment. While lucrative for drug companies, and likely to be aimed at the US healthcare market, in the UK it could become a “luxury” good for those able to pay vast sums of money in the growing private healthcare sector.
Another is the serious side-effects: in the study, brain swelling occurred in 24% of participants and brain bleeding occurred in 31.4% on the drug compared with 13.6% in the placebo group. There were also three deaths during the trial, which have been linked to Aria (amyloid-related imaging abnormalities) – seizures and bleeding in the brain. Regulators such as the US Food and Drug Administration and Britain’s Medicines and Healthcare products Regulatory Agency play an important role in assessing these findings and determining whether the drug’s effectiveness outweighs the side-effects, or whether use should be limited to a more targeted group. They will probably make a decision by the end of 2023 on approval for clinical use.
Part of the problem for me, as an academic, in assessing the drug is that the full results of the trial haven’t yet been shared publicly or published in a peer-review journal. So far all the information is by pharmaceutical press release (“science by press release” was also a challenge at the height of the Covid-19 pandemic). This means we cannot access the full data or scrutinise the trial yet, and there is always an incentive for private companies to overstate the effectiveness of new drugs. Trial results need to be assessed robustly by an independent body of experts.
While it is unlikely to change clinical practice until at least 2025, the news of donanemab is again an indication that science is continuing to make progress when it comes to treating the major causes of illness and death, even one related to the highly complex inner workings of the brain.
We’ve rarely managed to “cure” a disease completely, but we have managed to develop tools to reduce the pain and debilitating symptoms of various diseases – and improve the quality and quantity of people’s lives. So, there are caveats and the need for caution, but these new Alzheimer’s drugs are indeed the grounds for that rare thing these days: hope.
Prof Devi Sridhar is chair of global public health at the University of Edinburgh