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What to know about 2 new Alzheimer's disease drugs approved in Singapore
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One factor that could stand in the way of wider acceptance of these drugs is their costliness.
SINGAPORE – Tackling Alzheimer's disease in Singapore received a boost earlier in 2025, when the authorities approved two new drugs for the neurodegenerative disease.
Although these drugs – lecanemab and donanemab – cannot cure or reverse the effects of Alzheimer's, they have been shown to slow the progression of the disease, which accounts for almost 70 per cent of dementia cases worldwide.
Simply Science looks at what these drugs do, how effective they are, as well as the risks and costs.
How do they work?
The two new drugs are monoclonal antibodies, which are lab-produced proteins that mimic natural antibodies.
They work by targeting and removing beta-amyloids – molecules that accumulate in the frontal cortex and hippocampus of the brain – causing Alzheimer's disease.
Lecanemab, which is marketed as Leqembi, is developed by pharmaceutical firms Eisai, Biogen and BioArctic.
Donanemab, marketed as Lormalzi in Singapore and Kisunla in other countries, is developed by Eli Lilly.
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Both are intravenous injections – lecanemab is administered every two weeks over about 1½ years, and donanemab is administered every four weeks over the same period.
How effective are they?
During clinical trials, both drugs demonstrated the ability to slow Alzheimer's disease.
Findings from the clinical trial of lecanemab, published in the New England Journal of Medicine, showed that it slowed decline for people with early Alzheimer's disease by about 27 per cent to 37 per cent.
Meanwhile, results from donanemab's Phase 3 clinical trial, published in the Journal of the American Medical Association, showed that the drug slowed cognitive decline by about 20 per cent to 29 per cent.
Eisai medical director Amitabh Dash said lecanemab differs from existing drugs, which treat symptoms and manage memory or behavioural issues only temporarily.
'It works by clearing these protofibrils and amyloid plaques, which are believed to contribute to the progression of the disease,' said Dr Dash.
Protofibrils refer to protein aggregrates such as beta-amyloids.
Lecanemab was approved by the US Food and Drug Administration (FDA) in 2023, and by the Medicines and Healthcare products Regulatory Agency in Britain in 2024.
Donanemab received FDA approval in 2024, and was also approved in Britain that year.
In Singapore, the Health Sciences Authority (HSA) confirmed that the two drugs had been approved for use earlier in 2025.
'They are prescription-only medicines, and the treatment should be initiated by a physician experienced in the diagnosis and treatment of Alzheimer's disease,' HSA told The Straits Times.
What are the side effects?
For both drugs, the common side effects include infusion-related reactions such as fever, body aches and joint pains.
However, the drugs have also been known to cause amyloid-related imaging abnormalities, known as Aria, a condition that can cause brain swelling or bleeding.
In many cases, the condition is asymptomatic. But in more severe cases, it can cause seizures, or even death in rare instances.
'MRI monitoring is recommended during treatment to manage this risk safely,' said Dr Dash, referring to magnetic resonance imaging.
What has been the response in Singapore to the drugs?
Doctors in Singapore who have prescribed lecanemab described their experience as largely positive.
Dr Lee Kim En, a neurologist at Mount Elizabeth Hospital, prescribed the drug to 27 patients, who had symptoms such as memory loss affecting their daily lives and difficulty in performing familiar tasks, including handling personal and financial matters.
Most patients had shown a favourable response to the treatment, with a slowing in disease progression and preservation of cognition.
'Only one patient experienced mild confusion, disorientation for several hours after his first treatment,' Dr Lee added.
He described lecanemab as a 'breakthrough treatment' for patients in the early stages of Alzheimer's disease.
'Without intervention, the time course of deterioration may take four to eight years, requiring full-time care and assistance for all aspects of daily living,' he said.
Associate Professor Adeline Ng, a senior consultant at the National Neuroscience Institute's neurology department, had prescribed lecanemab to two women below the age of 65 who were diagnosed with mild Alzheimer's and had gradual mild cognitive decline.
While on treatment, they were able to be more engaged with their families and maintain their ability to look after their daily needs, Prof Ng said, noting that neither had side effects.
She intends to continue prescribing lecanemab, describing the treatment as 'the start of an era of new drug treatments' that could potentially modify the disease course for patients.
Prof Ng stressed that such drugs are effective only in the early stages of Alzheimer's and are not a cure. Rather, they delay progression to the next stage of the disease by about six to eight months.
'The drug is also not suitable for some patients, such as those who have had previous strokes or who take certain blood thinning medication, due to the increased risk of bleeding in the brain,' she added.
What are the costs?
One factor that could stand in the way of wider acceptance of these drugs is their costliness.
In the United States, lecanemab treatment is priced at US$26,500 (S$33,900) per year, while donanemab costs about US$32,000 annually.
Britain's National Institute for Health and Care Excellence has declined to recommend both drugs for routine use under the publicly funded National Health Service, due to the high costs of purchasing and administering the drugs, and a lack of evidence on their long-term effects.
In Singapore, the prices of the two drugs are not publicly available.
However, the Ministry of Health said it is evaluating the clinical efficacy and cost-effectiveness of the two drugs to decide whether to subsidise them in the future.
Dr Dash said such drugs represent a paradigm shift in the approach to Alzheimer's, noting that early diagnosis and treatment will become increasingly important due to the ageing populations in Singapore and across the region.
'The availability of Leqembi may drive healthcare systems to adopt biomarker-based diagnosis, improve infrastructure for safe infusion and monitoring, and offer patients more hope for slowing disease progression rather than only managing symptoms,' he said.
Simply Science is a series that looks at the science behind everyday questions.
