An Alzheimer's drug deemed too costly for the NHS can slow progression of dementia by up to eight years, researchers have claimed. Medicines assessor NICE ruled in June that the benefits of two breakthrough therapies were too modest to justify the price, after trials showed they could delay progression from mild to moderate disease by four to six months. But new data for lecanemab, also known as Leqembi and made by Eisai, presented at a major conference raises hope that the drug's real-world benefits may be greater than first thought.

Researchers found long-term treatment could delay progression from mild cognitive impairment to moderate Alzheimer's disease by 8.3 years among patients with low levels of amyloid protein in the brain and who started treatment at an early stage. Data was also presented about an injectable version of the drug, delivered using an auto-injector.

This could provide a more accessible way to administer the drug at home, without needing an intravenous drip.

Commenting on the research, Dr Richard Oakley, associate director of research and innovation at Alzheimer's Society, said: "For decades, people with Alzheimer's disease have been desperately waiting for treatments that slow disease progression.

"This new data on lecanemab's real-world use outside of clinical trials is promising, as it indicates treating people earlier could provide more benefit.

"We still need to understand what slowing of disease progression means for people living with Alzheimer's disease and their daily life, such as whether it will help them to stay independent and manage everyday tasks for longer."

The findings were presented at the Clinical Trials in Alzheimer's Disease (CTAD) conference in San Diego, USA.

Dr Oakley added that such breakthroughs "will only make a difference if people are diagnosed early and accurately".

He said: "Around one million people are living with dementia in the UK and more than a third don't have a diagnosis.

"While lecanemab is not currently available on the NHS, hope is on the horizon with over 130 Alzheimer's disease drugs in clinical trials.

"The UK Government must act now to improve dementia diagnosis and prepare the NHS for delivering these new treatments."

Another Alzheimer's drug, donanemab, was also approved for use in the UK but rejected for NHS use.

Donanemab and lecanemab are targeted antibody drugs that slow down the early stages of Alzheimer's.

They represent a huge step forward in research because they target a known cause of the disease, rather than just treating symptoms.

Both drugs bind to amyloid, a protein which builds up in the brains of people living with Alzheimer's disease.

Last year, NHS England published a briefing paper suggesting that bringing the drugs to the health service could cost £500 million to £1 billion per year.

Alzheimer's disease is the most common form of dementia. According to Alzheimer's Society, one in three people born in the UK today will develop dementia in their lifetime.

By 2040, about 1.4 million people in the UK could be living with the condition.