Experts say trial provides further evidence that attacking the build-up of proteins in the brain can slow the progression of the disease.

United States pharmaceutical giant Eli Lilly announced on Wednesday that in a late-stage trial of nearly 1,200 people in the early stages of Alzheimer’s disease, the drug, donanemab, slowed the progression of symptoms by 35 percent over a period of 18 months compared with a placebo.

The effect was measured by cognition and the patients’ ability to carry out daily tasks like managing finances, driving, engaging in hobbies and conversing about current events in a standardised index called the Integrated Alzheimer’s Disease Rating Scale (iADRS).

Side effects included temporary swelling in parts of the brain, which occurred in almost a quarter of the treated patients.

Lilly said the incidence of serious brain swelling in the study was 1.6 percent, including two deaths attributed to the condition, while a third might have also died from the treatment.

Nonetheless, the data was widely praised by independent experts, who said donanemab had the potential, if it secured regulatory approval, to significantly improve the lives of people suffering from the most common form of dementia.

Lilly said it was “extremely pleased” at the study outcome and would submit its results to the US Food and Drug Administration (FDA) as well as other global regulators and hoped to get US approval by as early as the end of the year.

Mark Mintun, a top Lilly executive in neuroscience R&D, acknowledged, however, that “like many effective treatments for debilitating and fatal diseases, there are associated risks that may be serious and life-threatening”.

More than 55 million people worldwide are living with dementia, according to the World Health Organization (WHO), presenting a significant challenge to healthcare systems. With population ageing, the United Nations health agency expects the number of sufferers to rise to 78 million by 2030, and 139 million by 2050.

In January, the US approved lecanemab, an Alzheimer’s drug produced by Biogen and Eisai, which was found to slow the rate of cognitive decline by 27 percent and also declared a game-changer by experts.

Alzheimer’s disease is characterised by a build-up of tau and amyloid beta proteins, which form plaques and tangles causing brain cells to die and the brain to shrink.

Like lecanemab, donanemab is an antibody therapy that targets amyloid beta.

The patients in the late-stage trial had intermediate levels of tau.

“This clinical trial is a real breakthrough, demonstrating a remarkable 35 percent slowing of cognitive decline in Alzheimer’s patients with high amyloid beta but low tau burden,” said Marc Busche, the UK Dementia Research Institute’s group leader at University College London.

Experts say treatments targeting both proteins might be even more successful.

Alzheimer’s disease accounts for as many as 80 percent of cases of dementia, according to the Alzheimer’s Association. It progressively destroys thinking and memory, robbing people of the ability to carry out the simplest of tasks.

“These are the strongest phase 3 data for an Alzheimer’s treatment to date,” said Maria Carrillo, the chief science officer at the US Alzheimer’s Association. “This further underscores the inflexion point we are at for the Alzheimer’s field.”