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Anti-Amyloid Drugs (Lecanemab & Donanemab): What They Do for Early Alzheimer's

If you or your loved one has been diagnosed with mild cognitive impairment or early-stage Alzheimer's, you may have heard about two new drugs called lecanemab and donanemab. These are not a cure, but they are the first treatments that actually target the disease itself by removing amyloid plaques from the brain, and they can modestly slow down the progression of symptoms. Real-world experience shows they are generally safe when used carefully, and many patients and families report feeling satisfied with the results. This article will help you understand exactly what these drugs do, who qualifies, what the risks are, and how to talk with your doctor about whether they might be right for you.

Key points

  • Lecanemab and donanemab are the first disease-modifying drugs for Alzheimer's; they remove amyloid plaques and modestly slow cognitive decline.
  • They are only for people with confirmed early Alzheimer's (MCI or mild dementia) and require a PET scan or spinal tap for diagnosis.
  • Serious side effects include ARIA (brain swelling or bleeding), which is why regular brain MRIs are mandatory.
  • Genetic testing for APOE e4 is recommended because it increases the risk of side effects.
  • These drugs are not a cure; people on them still decline, but more slowly than without them.
  • Real-world data from clinics and memory centers shows safety and effectiveness similar to clinical trials, and patients are generally satisfied.

What Are Lecanemab and Donanemab?

For more than 20 years, the only FDA-approved Alzheimer's drugs were ones that managed symptoms, like donepezil (Aricept) and memantine (Namenda). Those medications help with thinking and memory for a while, but they do not slow the underlying disease. Lecanemab and donanemab are different: they are the first disease-modifying therapies for Alzheimer's. They are monoclonal antibodies, which means they are lab-made proteins that act like your body's own immune system to target and remove a sticky protein called beta-amyloid that builds up in the brain during Alzheimer's disease. By clearing this amyloid, these drugs can modestly slow the progression of cognitive decline, meaning people on the drug decline more slowly than those not on it. They are not a cure, and they do not work for everyone, but they represent a real breakthrough after decades of no new options.

Who Can Take These Drugs?

These drugs are only for people in the very earliest stages of Alzheimer's disease, specifically mild cognitive impairment (MCI) or mild dementia due to Alzheimer's. To qualify, a person must have a confirmed diagnosis of Alzheimer's disease, usually through a PET scan or spinal fluid test that shows amyloid plaques in the brain. They must also be in good general health, because the drugs require regular intravenous infusions and close monitoring. People with a history of bleeding in the brain, those on blood thinners, or those with certain genetic risk factors (like having two copies of the APOE e4 gene) may be at higher risk for serious side effects, including brain swelling or small brain bleeds. Your doctor will likely recommend genetic testing for APOE e4 before starting treatment.

How Do They Work and What Are the Risks?

Lecanemab and donanemab are given as intravenous infusions, usually every two weeks or every four weeks, depending on the drug. They work by binding to amyloid plaques and signaling the immune system to clear them away. In clinical trials, lecanemab slowed cognitive decline by about 27% over 18 months compared to placebo, and donanemab showed similar or slightly better results. However, these drugs also carry risks. The most common side effects are infusion-related reactions like fever, chills, or nausea. More serious risks include ARIA (amyloid-related imaging abnormalities), which can show up on MRI scans as brain swelling or small bleeds. Most ARIA is mild and goes away on its own, but in rare cases it can cause serious symptoms like headache, confusion, or even stroke. Because of this, anyone taking these drugs needs regular brain MRIs to monitor for these changes.

General caregiving information, not medical advice. Check medications and major care changes with your clinician.

Practical tools

  • Amyloid PET scan or CSF analysis

    Required to confirm Alzheimer’s pathology before starting anti-amyloid therapy. Not interchangeable with clinical diagnosis alone.

  • Baseline and serial MRI (3T preferred)

    Baseline prior to first infusion, then at predefined intervals (e.g., after doses 1–5) to detect ARIA. Sequences should include T2* GRE/SWI, FLAIR, and DWI.

  • ARIA management protocol

    Standardized protocol for asymptomatic ARIA (continued treatment with monitoring) and symptomatic ARIA (temporary or permanent discontinuation, steroid taper, neurology consultation).

Discuss with your clinician

Ask your doctor: 'What is my risk of ARIA (brain swelling or bleeding) based on my age, health, and genetic status?'

Ask: 'If I am on a blood thinner, can I safely take these drugs? Do I need to stop the blood thinner temporarily?'

Ask: 'How often will I need brain MRIs, and what symptoms should I watch for between scans?'

Ask: 'Can I continue taking donepezil, memantine, or other medications while on lecanemab or donanemab?'

Ask: 'What is the cost of these drugs, and will my insurance cover them? Are there patient assistance programs?'

Ask: 'If I have a serious side effect, what is the treatment? Can I stop the drug safely?'

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