October 2026 Monoclonal Antibodies for Alzheimers Risks and Benefits

Monoclonal Antibodies for Alzheimer’s Dementia 

Botes Memory Method  |  Research based family handout  |  September 2026 

Key message. Lecanemab and donanemab can modestly slow decline on clinical rating scales in selected people with early Alzheimer’s disease. They do not cure dementia or restore lost skills. Brain swelling and bleeding are the principal safety concerns, and treatment requires specialist screening and MRI monitoring. [1–6] 

Monoclonal antibody and anti amyloid mean different things 

A monoclonal antibody is a laboratory-made protein designed to bind a particular target. “Anti-amyloid” describes the target: amyloid beta, a protein that forms plaques in Alzheimer’s disease. Lecanemab and donanemab are both monoclonal antibodies and anti-amyloid medicines. The terms are not two competing treatment categories. Other monoclonal antibodies target different substances or treat different diseases. [4–6] 

Who might be considered 

A specialist may consider treatment for someone with mild cognitive impairment due to Alzheimer’s disease or mild Alzheimer’s dementia, after confirming amyloid in the brain. The person needs an assessment of disease stage, MRI findings, bleeding risks, other medicines, treatment burden, and care goals. These medicines have not been established for starting in moderate or severe dementia. European authorization excludes people with two APOE4 gene copies; U.S. labeling warns that they have a higher risk of brain imaging abnormalities. [4–6] 

What benefit did the trials measure 

What these numbers mean. Participants in both treatment and placebo groups continued to decline. A relative percentage such as “25% slower decline” is not a 25% recovery of memory or daily ability. The trials used different outcome scales and populations; their numbers do not show which drug is superior. Evidence that treatment reliably preserves bathing, dressing, medication management, or aging in place is lacking. [1–3] 

Risks and treatment burden 

ARIA. Amyloid related imaging abnormalities include swelling (ARIA-E) and small bleeds or iron deposits (ARIA-H). Many are visible only on MRI, but some cause headache, new confusion, vision changes, weakness, dizziness, seizures, or serious brain bleeding. New symptoms require prompt medical assessment. [4–6] 

How often? In lecanemab’s main trial, ARIA-E occurred in 13% of treated participants versus 2% on placebo; ARIA-H occurred in 17% versus 9%. Donanemab’s original regimen produced ARIA-E in 24% versus 2% on placebo. In a separate study using newer gradual dosing, ARIA-E occurred in 16% of treated participants. These are not head-to-head comparisons. [4, 5] 

Who has more risk? Two APOE4 copies, certain prior microbleeds or other MRI signs of fragile blood vessels, and some blood-thinning treatments affect the risk decision. European rules restrict use with anticoagulants; U.S. labels call for caution, particularly with anticoagulants and clot-busting treatment for suspected stroke. Tell emergency clinicians that the person receives an anti-amyloid antibody. [4–6] 

Practical demands. Expect a baseline MRI and repeated MRI scans, treatment appointments or supervised injection arrangements, follow-up visits, possible treatment interruptions, and a discussion of insurance coverage and out-of-pocket costs. The exact schedule depends on the drug and jurisdiction. [4–6] 

How independent reviewers interpret the evidence 

The FDA and European Medicines Agency judged the benefit and risk acceptable for specified early-stage patients. A 2026 Cochrane review pooled 17 trials of several anti-amyloid antibodies, including drugs that were not approved. It judged the average effect on cognition and dementia severity at 18 months trivial and the functional effect small at best, while finding more swelling and microbleeds. The class-wide review and the two approved drugs’ trials answer related but different questions. Longer-term effects on meaningful independence remain uncertain. [1–6] 

Questions for the specialist 

• Is Alzheimer’s amyloid confirmed, and is this the stage studied in the trials? 

• What do the APOE4 result, MRI, bleeding history, and current medicines mean for this person’s risk? 

• What change in a valued daily activity would count as a worthwhile benefit, and when will we reassess? 

• What MRI, treatment, emergency, insurance, and caregiver arrangements will be needed? 

Research and agency sources 

[1] Van Dyck et al. Lecanemab in early Alzheimer’s disease. NEJM, 2023. doi:10.1056/NEJMoa2212948 

[2] Sims et al. Donanemab in early symptomatic Alzheimer disease. JAMA, 2023. doi:10.1001/jama.2023.13239 

[3] Cochrane. Amyloid beta targeting monoclonal antibodies, 2026. doi:10.1002/14651858.CD016297 

[4] U.S. FDA. Leqembi prescribing information, 2026. Read label 

[5] U.S. FDA. Kisunla prescribing information, 2025. Read label 

[6] European Medicines Agency. Leqembi and Kisunla overviews. Leqembi 

EMA Kisunla overview: Read overview