Monoclonal Antibodies: New Treatments for Alzheimer’s

Anti-amyloid monoclonal antibodies are the first group of medicines that measurably slow the course of Alzheimer’s disease. For years, treatment could only ease symptoms. The new medicines, lecanemab and donanemab, target one of the core changes of the disease. They do not cure Alzheimer’s and they do not suit everyone. This guide explains what they do, who they are for and what risks they carry.

How monoclonal antibodies work in the brain

In Alzheimer’s disease, a protein called beta-amyloid forms plaques between nerve cells. Together with the tau protein, these plaques add to the gradual damage of brain cells. The antibodies are lab-made proteins that recognise amyloid and help the immune system clear it.

In the trials, PET scans showed a large drop in amyloid. For families, though, the clinical course matters most. Decline in memory and daily function was about 27–35% slower over 18 months. The figure varied by medicine and patient group. In absolute terms, the difference equals a few months of delay over a year and a half. The benefit is real, but modest.

Lecanemab and donanemab: the key differences

• Lecanemab: an intravenous infusion every two weeks, lasting about one hour.
• Donanemab: an intravenous infusion every four weeks, lasting about half an hour. The doctor may stop it once a PET scan shows that the amyloid has cleared.

The European Medicines Agency reviewed lecanemab and later donanemab and approved both in the EU under strict conditions. In Europe, the medicines are for people who do not carry two copies of the APOE4 gene. Access and reimbursement differ from country to country. Ask your neurologist about the situation in Greece.

Who may benefit

The antibodies only have a place in the early stages. They are for people with mild cognitive impairment or mild dementia due to Alzheimer’s. In moderate or severe dementia they have shown no benefit. Before treatment starts, the neurologist usually asks for:

• proof of amyloid with a PET scan or a spinal fluid test.
• APOE4 gene testing, because it affects the risk of side effects.
• a brain MRI, to rule out micro-bleeds and other damage.
• a review of medicines, especially blood thinners.

New blood tests now make the first screening easier. Learn more in our article on the blood test for Alzheimer’s from ΔΕΛΦΙΝΙ. If there is no diagnosis yet, start with the early signs of dementia and talk to a doctor.

The risks: what is ARIA?

The main side effect goes by the name ARIA. It means changes that an MRI shows: local swelling or small bleeds in the brain. In the trials, swelling occurred in about one in eight people on lecanemab and one in four on donanemab. Most of the time it caused no symptoms and settled within weeks or months.

Rarely, ARIA causes headache, confusion, vision problems or seizures. A few serious cases also occurred. The risk is higher in people with two copies of APOE4 and in those on blood thinners. For this reason, the neurologist plans MRI scans before the start and at set points in the first months. If the person has a new headache, confusion or a change in vision, tell the treatment team at once.

What treatment looks like in practice

The person receives the infusion in a hospital or infusion centre. During it, nurses watch for reactions such as fever, chills or dizziness. These reactions are usually mild. Treatment means many visits, a lot of travel and a companion each time. This puts a real load on an older person and their carer, so discuss it from the start.

The antibodies do not replace familiar symptom medicines such as donepezil or memantine. The neurologist decides whether to continue them alongside.

Daily care still comes first

No medicine replaces good daily care. These basics support daily function:

• control of blood pressure and blood sugar.
• regular movement and good sleep.
• good hearing and social contact.

Activities that stimulate thinking support quality of life. Find ideas in our article on cognitive stimulation for older adults from ΔΕΛΦΙΝΙ.

At ΔΕΛΦΙΝΙ, medical follow-up includes close work with the treating neurologist, keeping to the test schedule and attention to any new symptom. The Alzheimer’s Association also offers information for families on its lecanemab page.

Frequently asked questions

Do monoclonal antibodies cure Alzheimer’s?

No. In the trials they slowed decline by about 27–35% over 18 months. The disease keeps progressing, but more slowly.

How often does the person need an MRI?

Before the first infusion and at set points in the first months, following the schedule for each medicine. New symptoms may lead to an extra scan.

Can people with advanced disease receive this treatment?

No. The medicines have approval only for mild cognitive impairment or mild dementia due to Alzheimer’s. In later stages they have shown no benefit.

How do we know if the treatment helps?

The neurologist tracks memory and daily function with tests and talks with the family. Scans show the drop in amyloid. The person may not feel better, because the aim is slower decline.

For personal advice about your relative, please contact us and we will get back to you.