Leqembi and Kisunla are the two FDA-approved anti-amyloid antibody drugs for early Alzheimer's in 2026, and neither has been proven better in a head-to-head trial. Leqembi (lecanemab) is given indefinitely with an at-home maintenance option, while Kisunla (donanemab) can often be stopped once brain plaques clear — the single biggest practical difference between them.
Both drugs are IgG1 antibodies that clear amyloid, a sticky protein that builds up in the Alzheimer's brain. Both slow decline modestly, both carry the same class risk of brain swelling and bleeding, and both demand genetic testing and repeated MRI scans. Choosing between them is less about raw effectiveness and more about dosing schedule, monitoring burden, and how each fits your life.
Medical information disclaimer: This article is for general educational purposes only and does not provide medical advice, diagnosis, or treatment. Always consult a physician or other qualified health professional about symptoms, medications, tests, or treatment decisions.
Table of Contents
- What each drug is and who qualifies
- How much do they actually slow decline?
- The core practical difference — finite course vs. ongoing therapy
- Risks and required monitoring
- Cost, coverage, and what to check before starting
- Frequently Asked Questions
What each drug is and who qualifies
Leqembi (lecanemab-irmb) is approved for early Alzheimer's — the mild cognitive impairment or mild-dementia stage — in people with confirmed amyloid buildup. According to the FDA and Eisai, the standard dose is 10 mg/kg by IV infusion every two weeks. Kisunla (donanemab-azbt) treats the same population — MCI or mild dementia with confirmed amyloid — and was FDA-approved on July 2, 2024, per Drugs.com's FDA approval history.
It is infused every four weeks, half as often as standard Leqembi. Neither drug is for moderate or advanced Alzheimer's, and neither works without documented amyloid. That means a PET scan or spinal fluid test is required before either can start. Both are treatments for the earliest symptomatic stage, not a cure and not a memory booster for healthy aging.
How much do they actually slow decline?
In the CLARITY AD trial, Leqembi slowed cognitive decline by 27% on the CDR-SB scale over 18 months versus placebo. In the separate TRAILBLAZER-ALZ 2 trial, Kisunla slowed decline by 35% on the iADRS scale, roughly 3.25 points over 144 weeks, as summarized in this JAMA-published analysis. Those percentages look different, but they come from different trials using different measuring scales.
There has been no head-to-head study, so you cannot conclude one drug outperforms the other from these numbers alone. It also helps to understand what "slowing decline" means. These drugs do not reverse symptoms or restore lost memory. At best they buy time — a person may stay at a given level of function somewhat longer than they otherwise would.
The core practical difference — finite course vs. ongoing therapy
Kisunla can be stopped once PET scans show the amyloid plaques are cleared, making it a finite course of treatment. Per Eli Lilly, this is a defining feature: many patients complete treatment and stop infusions. Leqembi follows a different model. After 18 months of IV infusions, it transitions to ongoing maintenance dosing rather than stopping.
In August 2025 the FDA approved Leqembi IQLIK, a once-weekly 360 mg subcutaneous autoinjector for maintenance — the first at-home anti-amyloid option, removing the need for infusion-center visits during maintenance. So the trade-off is clear. Kisunla offers a potential endpoint; Leqembi offers convenience during long-term dosing. If avoiding indefinite treatment matters most to you, Kisunla's model appeals. If you prefer an at-home injection over lifelong infusion trips, Leqembi's maintenance path may suit you better.
Risks and required monitoring
Both drugs carry a boxed warning for ARIA — amyloid-related imaging abnormalities — which means brain swelling (ARIA-E) or small brain bleeds (ARIA-H). Per an NIH review, this risk is higher in people who carry two copies of the APOE ε4 gene, so both drugs require genetic testing and both baseline and serial MRIs before and during treatment.
Kisunla's risk profile improved in 2025. The FDA approved a modified titration schedule that cut ARIA-E incidence about 41% at 24 weeks and about 35% at 52 weeks versus the original dosing, without losing efficacy — a meaningful safety upgrade. Watch for ARIA warning signs and report them promptly: Many ARIA cases cause no symptoms and are caught only on scheduled MRIs, which is why the monitoring schedule is not optional.
- New or worsening headache
- Confusion or disorientation
- Dizziness or trouble walking
- Vision changes
- Nausea or seizures
Cost, coverage, and what to check before starting
Medicare Part B covers both drugs under coverage-with-evidence-development. Per CMS, you need confirmed amyloid, a provider participating in an eligible registry, and MRIs before your 5th, 7th, and 14th doses. Before starting either drug, walk through these checks with your care team: If you carry two copies of APOE ε4, discuss your elevated ARIA risk carefully; for some people that risk outweighs the modest expected benefit.
- Confirm amyloid with a PET scan or spinal fluid test
- Get APOE ε4 genetic testing to gauge ARIA risk
- Complete a baseline MRI
- Verify your provider participates in a Medicare-eligible registry
- Decide which dosing model — finite (Kisunla) or maintenance (Leqembi) — fits your life
Frequently Asked Questions
Can I switch from one drug to the other?
There is no head-to-head trial or established protocol for switching, so any change should be a careful decision made with your neurologist, factoring in your ARIA history and MRI results.
Do these drugs cure Alzheimer's or restore memory?
No. Both only slow the rate of decline in early-stage disease. They do not reverse symptoms or recover lost function.
Why do I need genetic testing before treatment?
APOE ε4 status, especially carrying two copies, strongly raises the risk of brain swelling and bleeding, so testing guides both the decision to treat and how closely to monitor you.
