Eisai (TSE:4523) won FDA approval for LEQEMBI IQLIK—flexible IV or subcutaneous dosing with at‑home use—and data show its SC autoinjector matches IV exposure and effects; interim LEADER safety found mostly mild ARIA, while E2814 trials report rapid, large tau biomarker reductions.

Previous Week Recap

• Eisai FDA Approves LEQEMBI IQLIK: Eisai (4523) reported FDA approval of LEQEMBI IQLIK for early Alzheimer’s: flexible IV or subcutaneous dosing, switchable routes, and at-home administration from initiation through maintenance. 1 2
• Lecanemab SC Autoinjector Bioequivalent: Eisai (4523): lecanemab SC autoinjector 500 mg weekly showed bioequivalent exposure to IV start (104%, 90% CI 99.1–109%). Similar amyloid reduction, clinical outcomes, ARIA‑E rates, 1.4% ADA. 3
• LEADER Update: ARIA Incidence: Eisai (4523): LEADER interim safety update shows ARIA in 12.3% overall (ARIA-E 6.3%, ARIA-H 7.9%), mostly mild/asymptomatic; ARIA-E incidence differed by APOE ε4 status; no new large hemorrhages. 4
• AAIC 2026: E2814 Tau Reductions: Eisai (4523): at AAIC 2026, E2814 cut plasma eMTBR‑tau243 ~78% at 3 months and >90% at 9 months; CSF eMTBR‑tau243 down 62% at 3 months, 89% at 9 months; CSF p‑tau and total tau also fell. 5