FDA Approves Lecanemab Autoinjector, Marking First At-Home Treatment for Alzheimer Disease

The FDA has approved a new autoinjector formulation for lecanemab (Leqembi; Eisai), an antiamyloid therapy indicated for patients with early-stage Alzheimer disease (AD) and mild cognitive impairment (MCI) from AD. With the decision, the subcutaneous autoinjector (SC-AI) becomes the first-ever at-home, self-administered option for ongoing AD treatment, improving convenience and access for patients in the United States.¹

The new SC-AI, approved based on data from the pivotal phase 3 Clarity AD trial (NCT03887455), provides quicker administration for patients, lasting about 15 seconds total. In clinical trial settings, it demonstrated comparable exposure, improved tolerability, enhanced amyloid clearance, and better user-friendliness in patient, caregiver, and healthcare surveys. In addition, there is a belief that this new SC-AI will have significant societal cost savings, lowering treatment and administration expenses.

"This FDA action demonstrates continued progress in the field of Alzheimer's treatment," said Maria C. Carrillo, PhD, chief science officer and medical affairs lead at Alzheimer's Association, said in a statement.² "We are seeing the evolution of amyloid targeting antibody treatments, including improvements in drug delivery and acknowledgment that this class of treatments continues to demonstrate clinical benefit beyond the 18-month clinical trial data."

Branded as Leqembi Iqlik (pronounced "I click"), the subcutaneous autoinjector contains 360 mg/1.8 mL (200 mg/mL), administered over approximately 15 seconds. Its specific indication is for maintenance dosing to treat AD in patients with MCI or the mild dementia stage of the disease. Following an 18-month course of lecanemab-irmb IV treatment at 10 mg/kg every 2 weeks, patients can either continue those infusions at 10 mg/kg every 4 weeks or begin on this new weekly 360-mg subcutaneous injection with the autoinjector.

"The expectation with subcutaneous delivery of Alzheimer's treatment is that patients and care partners find it easier, simpler and more convenient to use, and that it reduces the need to travel for hospital or infusion center visits, compared to intravenous infusion," Carrillo said in a statement.² "The result is that more people will continue taking their medicine and experiencing treatment benefits."

The Clarity AD trial, published in the New England Journal of Medicine, enrolled 1795 patients with confirmed amyloid pathology and followed them for 18 months of treatment with lecanemab. Although the drug was initially approved in its biweekly IV form, a subsequent analysis led by Reisa Sperling, MD, a neurologist at Brigham and Women’s Hospital, examined outcomes with the SC-AI formulation.³

Results showed that after 6 months, patients receiving SC-AI achieved 14% greater amyloid plaque clearance compared with IV dosing. Pharmacokinetic analyses further confirmed that subcutaneous administration achieved drug exposure within accepted bioequivalence limits (80%–125%), supporting Eisai’s selection of a dose that delivers efficacy comparable to the IV formulation while potentially offering patients a more convenient treatment option.

Study investigators believe this new SC-AI formulation may improve the risk of amyloid-related imaging abnormalities (ARIA), a concern for amyloid-targeting treatments like lecanemab. In Clarity AD, the rates of ARIA-edema, ARIA-hemorrhage, and ARIA-H alone with intravenous lecanemab, the original formulation, were 12.6%, 17.3%, and 8.9%, respectively. In comparison, the corresponding rates for those on SC-AI were 16.7%, 22.2%, and 8.3%, though interpretation was limited by smaller sample size.

READ MORE: NeuroVoices: Howard Fillit, MD, on AAIC 2025 Highlights in Alzheimer Disease Prevention, Biomarkers, and Therapeutics

"This shift to subcutaneous maintenance dosing is a crucial step toward making Leqembi more accessible for patients, similar to how diabetes and GLP-1 medications are delivered, and represents the first step towards the day when patients can bypass infusions altogether," Howard Fillit, MD, cofounder and chief science officer of the Alzheimer's Drug Discovery Foundation (ADDF), said in a statement. “This milestone lessens the burden on patients and caregivers by reducing the logistical challenges of receiving Alzheimer’s treatment, while also bringing us closer to the day when patients can more easily receive a combination of drugs, potentially administered from home."

Typically, IV therapies impose more significant burdens on costs and payers, providers, patients, and caregivers. A U.S. cost comparison model study, published this summer in Neurology and Therapy, showed that SC-AI may offer substantial societal savings by lowering treatment costs, minimizing time demands, and relieving quality of life (QOL) burdens for patients and caregivers.

In the analysis, costs were estimated from a societal perspective over 4 years, including a per-patient, head-to-head analysis and population-level assessment accounting for population size, current treatment rates, and SC uptake. All told, SC-AI was estimated to yielded per-patient savings of $72,891–$80,925 over 4 years compared with IV administration, corresponding to annual savings of $18,223–$20,231 at willingness-to-pay thresholds of $150,000 and $200,000 per quality-adjusted life-year gained, respectively.⁵

The analysis estimated that 1,259,263 patients in the U.S. with early AD would be eligible for treatment with lecanemab, with 62,963 patients receiving treatment. In the IV scenario, all treated patients were assigned to the IV regimen; in the SC scenario, 31,093 (49.4%) were assigned to the SC administration, while 31,870 (50.6%) were assigned to the IV regimen.

The projected savings with SC-AI lecanemab were driven by reductions of $40,638 in treatment costs, $8151 in administration time, and $24,102–$32,136 in QOL related expenses per patient. When modeled at the population level over four years, this translated into $3.16–$3.71 billion in total societal savings, including $1.26 billion from treatment costs, $253 million from administration time, and $1.65–$2.20 billion from QOL-related improvements.

"We’ve long known that Alzheimer’s is not a one-target disease, and the future lies in precision combination therapies tailored to each patient based on their individual biomarker profiles," Fillit said in a statement.⁴ "Subcutaneous delivery is more than an upgrade – it’s a gateway to the next generation of Alzheimer’s care, accelerating our ability to bring effective, multi-modal treatment regimens to the millions of patients who need them."

REFERENCES
1. FDA Approves LEQEMBI® IQLIK™ (lecanemab-irmb) Subcutaneous Injection for Maintenance Dosing for the Treatment of Early Alzheimer's Disease. News release. August 29, 2025. Accessed August 29, 2025. https://www.prnewswire.com/news-releases/fda-approves-leqembi-iqlik-lecanemab-irmb-subcutaneous-injection-for-maintenance-dosing-for-the-treatment-of-early-alzheimers-disease-302542371.html
2. Alzheimer’s Association Welcomes FDA Action Approving Leqembi Weekly Subcutaneous Maintenance Dosing. News Release. Alzheimer’s Association. Published August 29, 2025. Accessed August 29, 2025. https://www.alz.org/news/2025/fda-action-approving-leqembi-subcutaneous-maintenance-dosing
3. Irizarry M, Li D, Dhadda S, Hersch S, Reyderman L, Kramer L. Preliminary update on lecanemab safety in Clarity AD open-label extension, including subcutaneous formulation. Presented at: CTAD conference; October 24-27, 2023; Presentation 4.
4. FDA Approval of Leqembi Subcutaneous Formulation Charts Path to Combination Therapies for Alzheimer’s Disease. News Release. Alzheimer's Drug Discovery Foundation. Published August 29, 2025. Accessed September 2, 2025. https://www.alzdiscovery.org/news-room/announcements/fda-approval-of-leqembi-subcutaneous-formulation-charts-path-to-combination-therapies-for-alzheimers-disease
5. Monfared AAT, Barrows S, Fox L, et al. Societal Costs and Efficiency of Subcutaneous versus Intravenous Lecanemab in Early Alzheimer’s Disease: A U.S. Cost Comparison Model. Neurology & Therapy. Published online July 4, 2025. doi:10.1007/s40120-025-00790-2