Lecanemab (Leqembi) for Alzheimer's Disease
Also known as: Leqembi, BAN2401
The first anti-amyloid antibody to demonstrate clear clinical outcomes reported in Alzheimer's trials, providing evidence for the amyloid hypothesis after decades of debate.
Mechanism of Action
Lecanemab selectively binds large soluble amyloid-beta protofibrils — considered the most neurotoxic amyloid species. Unlike aducanumab (which targets fibrils/plaques), lecanemab's protofibril selectivity may more directly address the toxic species. Clearance occurs through microglial phagocytosis via Fc receptor engagement.
General mechanism: Humanized IgG1 monoclonal antibody targeting soluble amyloid-beta protofibrils. Microglial phagocytic clearance.
Current Evidence
CLARITY AD Phase III showed 27% slowing of cognitive decline (CDR-SB) over 18 months. Significant amyloid plaque reduction on PET imaging. ARIA occurred in 21.3% but was mostly asymptomatic. Subcutaneous formulation in development for convenience.
Clinical Status: FDA full approval (2024). Standard of care for early Alzheimer's with confirmed amyloid pathology. AHEAD 3-45 prevention trial ongoing.
Safety Profile
ARIA (edema and microhemorrhages) in ~21% of patients. Higher risk in APOE4 homozygotes. Infusion reactions. MRI monitoring required.
Key Research Questions
- Can lecanemab prevent Alzheimer's in amyloid-positive, cognitively normal individuals?
- What combination with tau-targeting therapies provides optimal disease modification?
- Can treatment discontinuation after amyloid clearance maintain benefit long-term?
- How does APOE4 status affect risk-benefit for lecanemab treatment?
Frequently Asked Questions
How effective is lecanemab for Alzheimer's?
The CLARITY AD Phase III trial showed lecanemab slowed cognitive decline by 27% over 18 months compared to placebo. It reduced amyloid plaques by 59-74%. ARIA (brain swelling/bleeding) occurred in ~21% of patients (mostly asymptomatic). It's most effective in early-stage Alzheimer's.
Lecanemab vs donanemab for Alzheimer's
Both are anti-amyloid antibodies. Lecanemab (Leqembi) targets protofibrils; donanemab targets pyroglutamate amyloid. Donanemab showed 35% slowing in early/intermediate tau patients. Donanemab has a defined treatment duration (stop after amyloid clearance); lecanemab is ongoing. Both carry ARIA risks.