FDA Approves Leqembi Subcutaneous Starting Dose; Real-World Data and KCL-286 Show Progress

The U.S. Food and Drug Administration has approved a new subcutaneous (SC) starting dosage regimen for Leqembi (lecanemab-irmb) for the treatment of Alzheimer disease in patients with mild cognitive impairment or mild dementia stage of disease. Real-world data presented at the Alzheimer’s Association International Conference (AAIC) 2026 showed that more than three-quarters of early Alzheimer’s patients receiving lecanemab remained at the same disease stage after an average of 17 months, and a mouse study found that the experimental drug KCL-286 repaired DNA damage and reduced inflammation.

Lecanemab is a humanized immunoglobulin G1 monoclonal antibody directed against aggregated soluble and insoluble forms of amyloid beta. Previously, the SC regimen was only indicated for maintenance therapy, following 18 months of the intravenous (IV) dosage regimen. The SC autoinjector form of the drug (Leqembi Iqlik) received FDA approval for maintenance dosing in August 2025. According to Biogen and Eisai, the SC initiation dose is expected to reduce patient clinic visits and administrative burdens, while also preserving infusion capacity for patients who prefer or require IV therapy. The approval of SC lecanemab as an initiation dose was based on established data from the IV formulation, as well as evidence demonstrating comparable efficacy and amyloid removal benefits between the two formulations.

Substudies within the long-term extension phase of the CLARITY AD trial compared once-weekly SC lecanemab 500mg (two 250mg injections) with once every 2 weeks IV lecanemab 10mg/kg. Results showed the SC regimen demonstrated bioequivalence in drug exposure to the original IV regimen (exposure ratio, 104% [90% CI, 99.1-109]). Additionally, clinical data and modeling analyses showed the occurrence of exposure-related adverse events such as amyloid-related imaging abnormalities with edema/effusion (ARIA-E) was independent of the route of administration. The safety profile of SC lecanemab was consistent with that of IV administration, with most injection-related reactions being localized. Patients may now initially receive lecanemab therapy as an SC dose of 500mg once weekly, administered as two 250mg injections, providing a new at-home alternative to the established IV regimen. Following 18 months of the starting dosage regimen, patients may transition to a maintenance dose of either lecanemab IV 10mg/kg once every 4 weeks or lecanemab SC 360mg once every week.

At AAIC 2026, the drug manufacturers Eisai and Biogen highlighted findings from the LEADER (Lecanemab in Early Alzheimer’s Disease) study, an ongoing retrospective analysis evaluating how lecanemab performs in routine clinical practice across multiple healthcare centers in the United States. The interim analysis included 432 participants who had received at least 7 Leqembi infusions and had sufficient follow-up data to assess changes in disease stage. According to the study investigators, 75.9% of patients remained clinically stable over the treatment period, while an additional 6.6% improved by one disease stage, meaning nearly 83% of evaluable participants were either stable or showed improvement after receiving Leqembi for an average of 17 months. Researchers reported that treatment outcomes appeared broadly consistent across sex, race, ethnicity, and APOE e4 genetic status. The investigators also found that nearly 87% elected to continue treatment. The safety profile reported in the study was generally consistent with earlier clinical trials and the FDA-approved label, with adverse events occurring in 12.3% of people, most reported as mild and asymptomatic. The data were presented at AAIC 2026 but have not yet undergone peer review.

The conference takes place as lecanemab’s real-world performance is under scrutiny. In April 2026, the Cochrane Collaboration published a review of 17 Phase 3 trials involving more than 20,000 participants treated with amyloid-targeting antibodies and concluded that the absolute effects on cognitive decline and dementia severity were 'nonexistent or negligible.' The UK Dementia Research Institute called the methodology 'fundamentally flawed,' arguing that the review pooled 15 largely failed or withdrawn drugs alongside lecanemab and donanemab, the only two agents that have demonstrated measurable slowing of decline in large randomized trials. Eisai responded that 'extensive long-term clinical data out to four years and real-world experience with tens of thousands of patients globally show that patients who receive lecanemab continue to benefit from treatment.'

In a separate development, researchers at King's College London found that KCL-286, an experimental drug originally developed for spinal cord injury that has already passed Phase 1 safety trials, reduced multiple hallmarks of Alzheimer's disease in a mouse model. KCL-286 is a first-in-class, orally bioavailable small molecule that works by activating a specific protein in the retinoic acid pathway, which helps the body process vitamin A. The study found that KCL-286 repaired DNA double-strand breaks and reduced inflammation in mice with Alzheimer's disease, targeting multiple disease mechanisms rather than focusing on amyloid or tau alone. The findings were published in FEBS Open Bio. Because KCL-286 has already completed Phase 1 safety testing for another condition, researchers believe it could move more quickly into Alzheimer's clinical testing.