FDA Approves At-Home Starting Dose for Lecanemab, Marking First Subcutaneous Initiation Option for Alzheimer Disease Treatment

According to an announcement, the FDA has approved a subcutaneous starting dose regimen for lecanemab-irmb (Leqembi; Eisai/Biogen), allowing patients with early Alzheimer disease (AD) to initiate treatment at home via weekly self-injection for the first time. The decision marks a meaningful shift in how the therapy can be delivered, removing the prior requirement that patients complete 18 months of intravenous infusions before becoming eligible for at-home subcutaneous dosing.¹

The approval builds on more than two years of regulatory and formulation development for lecanemab. The drug first received FDA accelerated approval in January 2023, followed by traditional approval in July 2023, in its intravenous formulation at 10 mg/kg given every two weeks, based on data from the phase 3 Clarity AD trial (NCT03887455) in 1,795 patients with confirmed amyloid pathology and MCI or mild dementia.² That trial showed lecanemab slowed clinical decline by 27% versus placebo on the CDR-SB scale over 18 months. Patients were then limited to IV treatment throughout.

In August 2025, the FDA approved the subcutaneous autoinjector formulation of lecanemab, branded as Leqembi Iqlik, for maintenance dosing following an 18-month IV induction period.³ The 360 mg/1.8 mL autoinjector delivers a dose in approximately 15 seconds and was supported by Clarity AD open-label extension data showing the SC formulation produced 14% greater amyloid plaque clearance at 6 months compared with IV dosing, with pharmacokinetic data confirming bioequivalence within the 80% to 125% accepted range.³ Shortly after that approval, Eisai and Biogen submitted a supplemental BLA seeking to allow the 500 mg weekly SC starting dose, comprising two 250 mg injections, as an alternative to the IV induction requirement entirely.⁴

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The current approval grants that request. Patients can now initiate lecanemab treatment with weekly subcutaneous self-injection rather than requiring infusion center visits throughout the 18-month induction phase.¹ The FDA noted that while the subcutaneous formulation was not independently tested in large clinical outcome trials, its effectiveness is supported by the IV formulation's proven efficacy and evidence that SC administration produces equivalent drug exposure and comparable amyloid reductions.¹

The safety profile of the SC starting dose regimen is consistent with the broader lecanemab program. The most common adverse events include headache, injection site reactions, and amyloid-related imaging abnormalities (ARIA). ARIA remains the most clinically significant risk, presenting as temporary brain swelling or small bleeds on imaging that are often asymptomatic but can occasionally be serious. A boxed warning is included in the prescribing information, and testing for ApoE e4 status is recommended before initiating treatment given that homozygous ApoE e4 carriers face substantially higher ARIA rates than heterozygotes or non-carriers.¹ Caution is also recommended in patients taking anticoagulants, given increased intracerebral hemorrhage risk observed in that subgroup.

The practical implications for patients and health systems are considerable. IV administration requires regular infusion center visits, which impose burdens on patients, caregivers, and providers in terms of time, cost, and logistics. A U.S. cost comparison model published in Neurology and Therapy in 2025 estimated that SC administration could yield per-patient societal savings of $72,891 to $80,925 over four years compared with IV, driven by reductions in treatment costs, administration time, and quality-of-life-related expenses. At the population level, researchers estimated this could translate to $3.16 to $3.71 billion in total savings across the roughly 63,000 patients currently receiving lecanemab treatment.³

Lecanemab is currently approved in 48 countries and under regulatory review in 10 others. With the SC starting dose now cleared in the United States, the path from diagnosis to at-home treatment is substantially more direct for eligible patients with early-stage disease.

REFERENCES
1. FDA approves first at-home starting dose for Alzheimer's disease treatment. News release. US Food and Drug Administration. Accessed July 13, 2026. https://www.fda.gov/drugs/news-events-human-drugs/fda-approves-first-home-starting-dose-alzheimers-disease-treatment
2. van Dyck CH, Swanson CJ, Aisen P, et al. Lecanemab in early Alzheimer's disease. N Engl J Med. 2023;388(1):9-21. doi:10.1056/NEJMoa2212948. https://doi.org/10.1056/NEJMoa2212948
3. FDA approves LEQEMBI IQLIK (lecanemab-irmb) subcutaneous injection for maintenance dosing for the treatment of early Alzheimer's disease. News release. Eisai Co., Ltd. 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
4. Eisai and Biogen submit sBLA to FDA for once-weekly subcutaneous lecanemab starting dose. News release. Eisai Co., Ltd. September 2025. Accessed September 2025. https://www.eisai.com/news/2025/news202500001.html