The findings support a fully subcutaneous treatment pathway from initiation through maintenance treatment, offering greater convenience and flexibility for patients and care partners, the company states.

Key findings:

The data were presented during the Developing Topics session, “Lecanemab Subcutaneous Formulation in Early Alzheimer’s Disease: Emerging Clinical Evidence and Practical Use Considerations”. The session highlighted findings from the lecanemab SC-AI development program in early Alzheimer’s disease, including pharmacokinetic (PK), pharmacodynamic (PD), efficacy, safety and real-world patient and care partner experience data.

Results showed that once-weekly 500 mg SC-AI achieved drug exposure similar to the approved IV initiation regimen (10 mg/kg every two weeks), supporting the expectation of similar clinical efficacy and safety, regardless of the route of administration.

The subcutaneous dosing option may offer a convenient at-home alternative to IV infusion, with the potential to expand treatment access and support more flexible care delivery across healthcare settings.

Data showed

  • Bioequivalence achieved: Once-weekly 500 mg SC-AI demonstrated bioequivalence to the IV initiation regimen (10 mg/kg every two weeks), with an exposure ratio of 104% (90% confidence interval [CI]: 99.1%–109%). Exposure remained consistent across body weight quartiles, demonstrating a stable pharmacokinetic profile in a broad patient population.
  • Efficacy driven by exposure, not route of administration: Amyloid removal measured by amyloid PET, clinical efficacy measured by CDR-SB, and the incidence of ARIA-E were driven by lecanemab exposure rather than the route of administration. The 500 mg SC-AI initiation regimen achieved exposure comparable to the IV initiation regimen, supporting the expectation of a comparable efficacy and safety profile despite the different route of administration.
  • Consistent results across patient populations: The 500 mg SC-AI initiation regimen demonstrated consistent exposure, amyloid clearance as measured by amyloid PET, clinical efficacy and safety across body weight groups. Amyloid clearance and clinical outcomes were not meaningfully affected by body weight, supporting the use of a fixed-dose regimen.
  • Flexible administration options: Patients may switch between IV and SC administration as needed, and if a dose is missed, treatment can be administered the following day or up to six days later, providing greater flexibility and convenience in Leqembi administration.

Safety profile of subcutaneous Leqembi aligned with the IV formulation

  • Overall safety profile of SC-AI was generally consistent with that observed for the IV formulation. 
  • Incidence of ARIA-E with the 500 mg SC-AI initiation regimen was predicted to be similar to that observed with the IV initiation regimen. 
  • Injection-related reactions were observed with subcutaneous Leqembi, most of which were localized, while systemic reactions were less frequently observed. 
  • The incidence of anti-drug antibodies was low, at 1.4% in the 500 mg SC-AI group. No neutralizing antibodies were observed, confirming that the low immunogenicity profile was maintained with the SC-AI formulation.

Clinical trial perspectives and real-world evidence: sustained clinical benefit with SC-AI

Data from two US Alzheimer’s treatment centers (Alzheimer’s Research and Treatment Center, and First Choice Neurology and Visionary Investigators Network) provide early insight into clinical trial and real-world use of subcutaneous Leqembi:

  • At Alzheimer’s Research and Treatment Center, 28 patients receiving SC administration demonstrated slower cognitive decline as measured by CDR-SB[1] over 36 months relative to a matched Alzheimer’s Disease Neuroimaging Initiative (ADNI) natural history cohort. The cohort included 25 patients newly initiated on SC administration and 3 patients who transitioned from IV administration. 
  • In a separate case series from First Choice Neurology and Visionary Investigators Network, 10 of 11 evaluable patients (91%) showed improvement or remained stable on MMSE[2] compared with baseline before maintenance therapy. At this center, patients who had received maintenance therapy with SC administration for at least 6 months were included in the analysis.
  • Patient and care partner surveys conducted at these two sites demonstrated high satisfaction with subcutaneous Leqembi administration, with satisfaction rates ranging from 75% to 97%, convenience ratings from 83% to 97%, and willingness to recommend treatment ranging from 92% to 100%.

Results presented in this session further reinforce the importance of early and continuous treatment, highlighting how Leqembi SC initiation and maintenance administration provides greater optionality for long-term disease management, the company states.