FDA Grants Lecanemab Full Approval for Early Alzheimer's Disease (2023)
On 6 July 2023 the U.S. Food and Drug Administration converted lecanemab-irmb, an antibody drug for early Alzheimer’s disease, from accelerated approval to traditional approval. The drug had first been approved six months earlier, on 6 January 2023, under the FDA’s accelerated approval pathway; the July action followed a confirmatory study of 1,795 patients and a unanimous vote of an FDA advisory committee on 9 June 2023. The FDA called it “the first amyloid beta-directed antibody to be converted from an accelerated approval to a traditional approval for the treatment of Alzheimer’s disease.” The disease itself is described on the site’s Alzheimer’s Disease page.
This page reports what the FDA documents say: the two approval steps and what each one means, the confirmatory study, the advisory committee meeting, the side effects and the Boxed Warning, who the labeling raises concerns for, what the approval does not do, the drug’s status as of 18 October 2026, and how the action fits other FDA steps. The drug is referred to only by its generic (nonproprietary) name; no brand name or company is named here.
Table of Contents
- What the FDA Did
- Two Steps in One Year: January and July 2023
- Accelerated Approval, Surrogate Endpoints and Traditional Approval
- What the Drug Targets
- The Confirmatory Study
- The June 2023 Advisory Committee Meeting
- Side Effects and the Boxed Warning on ARIA
- Who the Labeling Raises Concerns For
- What the Approval Does Not Do
- Dates and Legal Status as of 18 October 2026
- How the Approval Fits Other FDA Actions
- Primary Documents
- Key Research Papers
- Connections
- Featured Videos
1. What the FDA Did
The FDA press release of 6 July 2023, “FDA Converts Novel Alzheimer’s Disease Treatment to Traditional Approval,” opens: “Today, the U.S. Food and Drug Administration converted [lecanemab-irmb], indicated to treat adult patients with Alzheimer’s Disease, to traditional approval following a determination that a confirmatory trial verified clinical benefit.” Its subtitle reads: “Action Follows Confirmatory Trial to Verify Clinical Benefit.”
The acting director of the Office of Neuroscience in the FDA’s Center for Drug Evaluation and Research (CDER) was quoted in the release: “Today’s action is the first verification that a drug targeting the underlying disease process of Alzheimer’s disease has shown clinical benefit in this devastating disease,” and “This confirmatory study verified that it is a safe and effective treatment for patients with Alzheimer’s disease.”
The one 2023 Federal Register document in this story is the notice that announced the June advisory committee meeting and opened a public docket (an online file where anyone can read and submit comments) under Docket No. FDA-2023-N-1114.
2. Two Steps in One Year: January and July 2023
- 6 January 2023 — accelerated approval. Lecanemab-irmb is entry number 1 on the FDA’s list “Novel Drug Approvals for 2023,” with an approval date of 1/6/2023 and the approved use “To treat Alzheimer’s disease.” The July press release confirms that the drug “was approved in January under the Accelerated Approval pathway.”
- 11 April 2023 — meeting notice. The FDA announced in the Federal Register (88 FR 21690) a meeting of its Peripheral and Central Nervous System Drugs Advisory Committee.
- 9 June 2023 — advisory committee. The committee met virtually and voted on whether the confirmatory study verified clinical benefit.
- 6 July 2023 — traditional approval. The FDA converted the approval.
The FDA list counts 55 novel drugs approved by CDER in 2023 — “new drugs never before approved or marketed in the U.S.” — and lecanemab-irmb is the first of them by date.
3. Accelerated Approval, Surrogate Endpoints and Traditional Approval
The July press release explains the two kinds of approval involved. The accelerated approval pathway, it says, “allows the FDA to approve drugs for serious conditions where there is an unmet medical need, based on clinical data demonstrating the drug’s effect on a surrogate endpoint… that is reasonably likely to predict a clinical benefit to patients.”
A surrogate endpoint is a measurement that stands in for the outcome patients actually care about. For lecanemab-irmb, the surrogate endpoint was “reducing amyloid plaques in the brain” — a change seen on brain imaging, not a direct measure of memory or daily function.
Accelerated approval comes with a condition. In the release’s words: “As a postmarketing requirement of the accelerated approval, the FDA required the applicant to conduct a clinical trial, often referred to as a confirmatory study, to verify the anticipated clinical benefit.” Traditional approval is granted when that benefit has been shown directly. The July 2023 action was the FDA’s determination that the confirmatory trial had done so.
4. What the Drug Targets
The FDA describes Alzheimer’s disease as “an irreversible, progressive brain disorder affecting more than 6.5 million Americans,” one that “slowly destroys memory and thinking skills and eventually, the ability to carry out simple tasks.” It notes that the specific causes “are not fully known,” but that the disease is characterized by changes in the brain — “including the formation of amyloid beta plaques and neurofibrillary, or tau, tangles” — that result in loss of neurons and their connections.
Lecanemab-irmb is an antibody. According to the FDA, it “works by reducing amyloid plaques that form in the brain, a defining pathophysiological feature of the disease.” The FDA calls it “amyloid beta-directed,” meaning it is aimed at the amyloid beta that forms these plaques.
5. The Confirmatory Study
The FDA based the July decision on the results of a phase 3 trial the press release calls Study 301. The release describes it as follows:
- Design: multicenter, randomized, double-blind, placebo-controlled, parallel-group. “Randomized” means patients were assigned by chance; “double-blind” means neither patients nor investigators knew who received the drug; “placebo-controlled” means the comparison group received an inactive infusion.
- Size: 1,795 patients with Alzheimer’s disease.
- Who was enrolled: treatment was started in patients at the mild cognitive impairment or mild dementia stage of disease, with confirmed presence of amyloid beta pathology.
- Dosing: patients were assigned 1:1 to placebo or the drug at 10 milligrams per kilogram of body weight, once every two weeks.
- Main result: the drug “demonstrated a statistically significant and clinically meaningful reduction of decline from baseline to 18 months on the primary endpoint, the Clinical Dementia Rating Scale Sum of Boxes score, compared to placebo.”
- Secondary results: statistically significant differences were also shown on all secondary endpoints, which included the Alzheimer’s Disease Assessment Scale Cognitive Subscale 14 and the Alzheimer’s Disease Cooperative Study-Activities of Daily Living Scale for Mild Cognitive Impairment.
The published report of this trial is the first paper listed under Key Research Papers.
6. The June 2023 Advisory Committee Meeting
The Federal Register notice of 11 April 2023 (FR Doc. 2023-07526) announced that the Peripheral and Central Nervous System Drugs Advisory Committee would meet “virtually on June 9, 2023, from 10 a.m. to 5 p.m. Eastern Time.” The notice states that the committee’s general function “is to provide advice and recommendations to FDA on regulatory issues,” that the meeting would be open to the public, and that the FDA was establishing a docket for public comment.
According to the July press release, the committee met “to discuss whether Study 301 provided evidence of clinical benefit” for the treatment of Alzheimer’s disease. “All committee members voted affirmatively that the results of the study verified the clinical benefit” for the indicated use.
7. Side Effects and the Boxed Warning on ARIA
The FDA lists the most common side effects as headache, infusion-related reactions and amyloid-related imaging abnormalities, known as ARIA — “a side effect known to occur with the class of antibodies targeting amyloid.”
The press release describes ARIA this way:
- It “most commonly presents as temporary swelling in areas of the brain seen on imaging studies that usually resolves over time and may be accompanied by small spots of bleeding in or on the surface of the brain.”
- It is often not associated with any symptoms, but symptoms can occur and include headache, confusion, dizziness, vision changes and nausea.
- It “can also infrequently present with serious and life-threatening brain edema that can be associated with seizures and other severe neurological symptoms.”
- “Intracerebral hemorrhages can occur in patients treated with this class of medications and can be fatal.” An intracerebral hemorrhage is bleeding inside the brain.
A Boxed Warning (a warning set apart in a box in the prescribing information) “is included in the prescribing information to alert patients and caregivers to the potential risks associated with ARIA.”
The FDA also reports that the drug is contraindicated (not to be used) in patients with serious hypersensitivity to lecanemab-irmb or to any of its inactive ingredients, and that adverse reactions may include angioedema (swelling) and anaphylaxis (a severe allergic reaction).
8. Who the Labeling Raises Concerns For
People with two copies of the ApoE ε4 gene variant. ApoE is a gene; ε4 is one version of it, and a person can carry zero, one or two copies. The FDA reports that patients treated with the drug “who are homozygous for the ApoE ε4 allele” (who carry two copies) “have a higher incidence of ARIA, including symptomatic, serious and severe ARIA, compared to heterozygotes and noncarriers.” According to the FDA, the prescribing information calls for testing for ApoE ε4 status before treatment starts, “to inform the risk of developing ARIA.”
People taking anticoagulants (blood thinners). The FDA reports that anticoagulant use “was associated with an increased number of intracerebral hemorrhages in patients taking [the drug] compared to placebo,” and that the prescribing information “recommends caution” when the drug is considered for patients taking anticoagulants or with other risk factors for bleeding in the brain.
People with serious hypersensitivity to the drug or its ingredients, in whom it is contraindicated.
Decisions about starting, continuing or stopping any medicine belong with a clinician.
9. What the Approval Does Not Do
- It does not cover every stage of Alzheimer’s. The FDA states that treatment is to be started in the mild cognitive impairment or mild dementia stage, “the population in which treatment was studied in clinical trials,” and that “the labeling states that there are no safety or effectiveness data on initiating treatment at earlier or later stages of the disease than were studied.”
- It is not a cure. The effect the FDA describes is a reduction of decline over 18 months compared with placebo — a slower rate of worsening — and the FDA calls Alzheimer’s disease “irreversible” and “progressive.”
- It does not remove the ARIA risk. The Boxed Warning on ARIA is part of the traditional approval’s prescribing information.
10. Dates and Legal Status as of 18 October 2026
- Accelerated approval: 6 January 2023.
- Advisory committee meeting notice: 11 April 2023 (88 FR 21690–21691, FR Doc. 2023-07526, Docket No. FDA-2023-N-1114).
- Advisory committee meeting and vote: 9 June 2023 (virtual).
- Conversion to traditional approval: 6 July 2023.
- Later Federal Register notice: on 29 December 2025 the FDA published its determination of the drug’s “regulatory review period” (90 FR 60717, FR Doc. 2025-23865, Docket No. FDA-2023-E-3236). This is a routine notice, required by law, made because an application had been filed with the U.S. Patent and Trademark Office to extend a patent on the product; it does not change the approval.
Status as of 18 October 2026: traditional approval in effect. A check of the Federal Register through 18 October 2026 for “lecanemab” found no FDA document withdrawing, suspending or otherwise changing the approval; the only later FDA notice naming the drug is the December 2025 patent-term notice above.
11. How the Approval Fits Other FDA Actions
The confirmatory step can go either way. In 2023 the FDA reached the opposite outcome for another accelerated approval. In April 2023 it withdrew approval of hydroxyprogesterone caproate injection, which had been approved in 2011 under accelerated approval to reduce the risk of preterm birth, after its required confirmatory trial did not show improvement in the health of babies. That action is described on FDA Withdraws Approval of the Only Drug for Preventing Preterm Birth (2023). For lecanemab-irmb, the confirmatory study verified benefit and the approval became traditional.
A second antibody of the same class. On 2 July 2024 the FDA approved donanemab, a second amyloid-clearing antibody for early Alzheimer’s disease. That approval is described on FDA Approves Donanemab for Early Alzheimer’s Disease (2024).
The history of the disease is on Alzheimer’s Disease: History and Discovery; the other major FDA actions of the year are listed on the FDA Actions of 2023 hub.
12. Primary Documents
- U.S. Food and Drug Administration (2023). FDA Converts Novel Alzheimer’s Disease Treatment to Traditional Approval. Press release, 6 July 2023 — fda.gov press release
- U.S. Food and Drug Administration, Center for Drug Evaluation and Research. Novel Drug Approvals for 2023 (entry 1, lecanemab-irmb, approved 1/6/2023) — fda.gov Novel Drug Approvals for 2023
- Food and Drug Administration, HHS (2023). Peripheral and Central Nervous System Drugs Advisory Committee; Notice of Meeting; Establishment of a Public Docket; Request for Comments. Federal Register 88 FR 21690–21691, 11 April 2023. Docket No. FDA-2023-N-1114 — FR Doc. 2023-07526
- Public docket FDA-2023-N-1114 — regulations.gov FDA-2023-N-1114
- Food and Drug Administration, HHS (2025). Determination of Regulatory Review Period for Purposes of Patent Extension (lecanemab-irmb; product name omitted here). Federal Register 90 FR 60717, 29 December 2025. Docket No. FDA-2023-E-3236 — FR Doc. 2025-23865
Key Research Papers
- van Dyck CH, Swanson CJ, Aisen P, Bateman RJ, Chen C, Gee M, et al. (2023). Lecanemab in Early Alzheimer’s Disease. New England Journal of Medicine 388(1):9-21 — PubMed PMID: 36449413
- Cummings J, Apostolova L, Rabinovici GD, Atri A, Aisen P, Greenberg S, et al. (2023). Lecanemab: Appropriate Use Recommendations. Journal of Prevention of Alzheimer’s Disease 10(3):362-377 — PubMed PMID: 37357276
- Honig LS, Sabbagh MN, van Dyck CH, Sperling RA, Hersch S, Matta A, et al. (2024). Updated safety results from phase 3 lecanemab study in early Alzheimer’s disease. Alzheimer’s Research & Therapy 16(1):105 — PubMed PMID: 38730496
- Hampel H, Elhage A, Cho M, Apostolova LG, Nicoll JAR, Atri A, et al. (2023). Amyloid-related imaging abnormalities (ARIA): radiological, biological and clinical characteristics. Brain 146(11):4414-4424 — PubMed PMID: 37280110
- Hampel H, Elhage A, Cho M, Nicoll JA, Atri A, et al. (2024). Amyloid-related imaging abnormalities (ARIA) and their radiological, biological and clinical characteristics: a plain language summary. Neurodegenerative Disease Management 14(3-4):51-62 — PubMed PMID: 38949171
- Rabinovici GD, Selkoe DJ, Schindler SE, Aisen P, Apostolova LG, Atri A, et al. (2025). Donanemab: Appropriate use recommendations. Journal of Prevention of Alzheimer’s Disease 12(5):100150 — PubMed PMID: 40155270
The first paper is the published report of the 18-month phase 3 trial behind the July 2023 conversion. The second is an expert panel’s appropriate-use recommendations for the drug; the third reports updated safety results from the same trial. The two Hampel papers review ARIA, the second in plain language for patients and families. The last is the matching expert-panel report for donanemab, the second drug of the class.