Solanezumab: What is the landmark first drug to 'slow progression' of Alzheimer's disease?

The first drug aimed at slowing the progression of Alzheimer's disease is set to be unveiled today (22 July) in what is hoped will be a breakthrough in tackling the most common cause of dementia.

Promising results of the latest trial into a new drug called Solanezumab will be presented at around 12 noon at the Alzheimer's Association International Conference in Washington.

The drug, which is being tested by US pharmaceutical giant Eli Lilly, is hoped to be able to slow the decline in memory and thinking skills over time.

How does Solanezumab work?

Scientists hope the drug can bind amyloids – deformed proteins – that build up and form plaques in the brain as an early pathological feature of Alzheimer's disease. It is thought the formation of these sticky plaques of amyloid build up between nerve cells, which leads to brain cell death over time.

Current treatments only tackle the symptoms of the disease, rather than the causes of Alzheimer's itself. If the drug is successful, it will be a breakthrough in slowing the pace of brain decline if taken early enough by patients.

The anti-amyloid treatment Solanezumab completed phase III trials in 2012 but failed to reach its targets in patients with mild to moderate Alzheimer's disease. Analysis of these trials showed those with mild Alzheimer's did show some improvements in memory, thinking and function. Further trials have shown progress is slowing brain decline.

Dr Eric Karran, director of research at Alzheimer's Research UK, said Solanezumab "could indeed be acting on the disease processes that drive Alzheimer's".

"While this could be evidence of the first disease-modifying treatment for Alzheimer's, the ultimate test will be whether these promising effects repeat again in the third, more targeted, phase III trial in people with mild Alzheimer's due to finish late next year," he said. "We await the results of that trial with great interest."

Dr Karran, who previously worked for Eli Lilly, told BBC Radio 4's Today programme that the drug will not be on the market for NHS patients for several years.

What causes Alzheimer's disease?

Alzheimer's disease is the most common cause of dementia, a term which describes a set of symptoms that can include memory loss and problems with thinking, language or problem-solving. It is a progressive disease, meaning more parts of the brain will be damaged over time.

During the course of the disease, proteins build up in the brain to form structures known as "plaques" and "tangles" – which leads to the loss of connections between nerve cells and their eventual death. According to Alzheimer's Research UK, people with the disease also have a shortage of some chemicals in their brain.

Data from the charity states there are about 850,000 people with dementia in the UK, 40,000 of whom are young people. By 2025, it is estimated one million people will have dementia in Britain.

Dementia disproportionately affects women, roughly two-thirds of people with the disease are female. One in six people aged 80 and over have dementia and 60,000 deaths a year are attributable to the disease.