A new drug has been hailed as a “turning point in the fight against Alzheimer’s” after it was found to slow the progression of the disease.

Donanemab was found to slow “clinical decline” by up to 35%, meaning that people with the disease could still go about performing day-to-day tasks including shopping, housekeeping, managing finances and taking medication.

The health spending watchdog in England is already assessing whether the drug can be used in the NHS.

Alzheimer’s Research UK said that “we’re entering a new era where Alzheimer’s disease could become treatable”.

And the Alzheimer’s Society said that treatments like donanemab could one day mean that Alzheimer’s could be likened to other long-term conditions such as asthma or diabetes.

The charity said that new treatments including donanemab – which works by removing a protein called amyloid that builds up in the brains of people with Alzheimer’s – heralds a “new era” for Alzheimer’s disease.

It comes as scientists published the final results of the trial – known as TRAILBLAZER ALZ-2 – examining the safety and efficacy of the drug, manufactured by Eli Lilly and Company.

Researchers examined almost 1,800 people with early-stage Alzheimer’s.

Half of them received a monthly infusion of donanemab and the other half were given a dummy drug, also known as a placebo, over 18 months.

The study, published in the Journal of the American Medical Association and presented to the Alzheimer’s Association International Conference in Amsterdam, concluded that after 76 weeks of treatment, donanemab was able to slow clinical decline by 35.1% in people with early Alzheimer’s whose brain scans showed low or medium levels of a protein called tau.

When the results were combined for people who had different levels of this protein, there was a 22.3% slowing in disease progression.

But researchers did find that among a small number of people in the study there were some serious side effects such as brain swelling.

Meanwhile three deaths in the donanemab group and one in the placebo group were considered “treatment related”.

Eli Lilly and Company said some people taking the drug would be able to finish the course of treatment in six months once their amyloid plaque cleared.

It said treatment with donanemab reduced amyloid plaque on average by 84% at 18 months, compared with a 1% decrease for participants on placebo.

Some 47% of people taking the drug who had early-stage disease and low or medium levels of tau were found to stall the disease for a year.

Dr Mark Mintun, group vice president of neuroscience research and development at Lilly and president of Avid Radiopharmaceuticals, said: “People living with early, symptomatic Alzheimer’s disease are still working, enjoying trips, sharing quality time with family – they want to feel like themselves, for longer.

“The results of this study reinforce the importance of diagnosing and treating disease sooner than we do today.”

The company said it is ready to work with health regulators in the UK as well as the NHS and Government on the “appropriate regulatory next steps”.

Anne White, executive vice president of Eli Lilly and Company and president of Lilly Neuroscience, said: “If approved, we believe donanemab can provide clinically meaningful benefits for people with this disease and the possibility of completing their course of treatment as early as six months once their amyloid plaque is cleared.”

The results come after another drug – lecanemab – was found to reduce memory decline among patients with early-stage disease.

Commenting on the results, Dr Richard Oakley, associate director of research and innovation at Alzheimer’s Society, said: “This is truly a turning point in the fight against Alzheimer’s and science is proving that it is possible to slow down the disease.

“Treatments like donanemab are the first steps towards a future where Alzheimer’s disease could be considered a long-term condition alongside diabetes or asthma – people may have to live with it, but they could have treatments that allow them to effectively manage their symptoms and continue to live fulfilled lives.

“Today’s full results support what we heard about donanemab back in May, that the drug is able to slow down the progression of Alzheimer’s disease by more than 20%.

“This study adds to the growing evidence that treating people as early as possible may be more beneficial, with the effects of donanemab greater in people who were at an earlier stage of the disease.

“Diagnosis will be key to the access of any new treatments.

“We can’t have a situation where treatments are approved for use in the UK but people aren’t diagnosed early or accurately enough to be eligible.

“We need early, and accurate, diagnoses available for everyone and the NHS ready to roll out treatments such as donanemab and lecanemab if and when they are approved in the UK.”

He added: “It’s also important to note that side effects did occur, although serious side effects only occurred in 1.6% of people receiving the drug.

“Regulators will need to balance these side effects against the benefits of the drug.

“We should also note that the majority of people who took part in this trial were white – it’s crucial that in future trials we see more diversity to prove that new drug treatments have similar effects for everyone living with Alzheimer’s disease.

“Just as we’ve seen a transformation in cancer treatment in recent decades, we’re really hopeful we’re on the same path for dementia.”

Dr Oakley also told BBC Breakfast: “In the last 12 months we’ve had two trials, one announced last November and one this afternoon, and these trials show (these drugs) remove a protein called amyloid from the brain really effectively, and that seems to slow down the progression of the disease.

“And it keeps people being able to do things like drive a car, manage finances, talk about current affairs, recognise family members for longer. And that is so important.

“So we really believe this is the beginning of a whole new era for Alzheimer’s disease.”

Dr Susan Kohlhaas, executive director of research and partnerships at Alzheimer’s Research UK, said: “Today’s announcement marks another milestone.

“Thanks to decades of research, the outlook for dementia and its impact on people and society is finally changing, and we’re entering a new era where Alzheimer’s disease could become treatable.

“As a potential first-generation treatment, donanemab’s effects are modest.

“But these results provide further confirmation that removing amyloid from the brain can change the course of Alzheimer’s, and may help people affected by this devastating disease if they’re treated at the right time.

“Set against this, it’s clear that donanemab does come with side effects, which for some can be very serious.

“Regulators will need to balance these benefits and risks before it is given a license for use.

“People living with Alzheimer’s deserve access to safe and effective treatments urgently.

“That’s why Alzheimer’s Research UK has written to the drug’s manufacturer, Eli Lilly, calling on them to put donanemab forward for regulatory review in the UK without delay.

“And this review should be conducted by the UK regulators as a priority.”

Meanwhile, a spokesperson for the National Institute for Health and Care Excellence (Nice), said: “Nice has already started work on its appraisal of donanemab for treating mild cognitive impairment or mild dementia caused by Alzheimer’s disease.

“Our aim is to produce recommendations on its use in the NHS as close as possible to it receiving its UK licence. To do this we are already talking to the NHS and the company.

“Whether a medicine is recommended by Nice is influenced by many factors including the evidence on how well it works but importantly also by its price, which is set by the company.

“It will also be important during our evaluation of donanemab to understand the services required by the NHS to deliver it and how those eligible for treatment will be identified.”

Sir John Hardy, professor of neuroscience and group leader at the UK Dementia Research Institute, UCL, added: “The successful outcome of the Eli Lilly’s anti-amyloid antibody donanemab is great news for Alzheimer’s disease and confirms the positive and similar outcome for Eisai’s lecanemab trial late last year.

“The results are very similar, and that in itself is reassuring.

“Disease progression is slowed about 30%, but it too has occasionally serious complications which require monitoring.

“Scientists now need to work to understand what we need to do to stop the disease rather than just slow it, but the major immediate task will be to organise NHS Alzheimer provision to be able to use these therapies.”