🧠 Lecanemab (Leqembi): Anti-Amyloid Therapy in Early Alzheimer’s Disease

📄 Abstract

Lecanemab (Leqembi), a humanized IgG1 monoclonal antibody targeting amyloid-beta protofibrils, represents a significant advancement in the treatment of early-stage Alzheimer’s disease (AD). Developed by Eisai and Biogen, Lecanemab received accelerated approval from the U.S. FDA in January 2023, followed by full approval in July 2023, based on data demonstrating its ability to reduce amyloid plaque burden and modestly slow cognitive decline.

This monograph reviews the drug’s mechanism of action, clinical trial evidence (notably the CLARITY-AD and Study 201 trials), safety profile, and regulatory background. Lecanemab is indicated for patients with mild cognitive impairment or mild dementia stage of Alzheimer’s disease, confirmed by amyloid pathology. While it has shown statistically significant benefits in cognitive function scores, concerns remain around risks of amyloid-related imaging abnormalities (ARIA), cost-effectiveness, and long-term outcomes.

As one of the first disease-modifying therapies to show a clinically meaningful impact in AD, Lecanemab marks a shift in Alzheimer’s treatment philosophy — from symptomatic relief to modifying disease progression. However, real-world effectiveness, accessibility, and patient selection remain areas of active research.

🧬 Introduction

Alzheimer’s disease (AD) affects millions worldwide and remains a leading cause of cognitive disability and dependency in older adults. Until recently, therapeutic options were limited to cholinesterase inhibitors and NMDA receptor antagonists that only offered symptomatic relief without altering disease progression. The development of disease-modifying treatments (DMTs), particularly targeting amyloid-beta (Aβ), has reignited hope for earlier intervention and improved outcomes.

Lecanemab (Leqembi) is among the first therapies to demonstrate clinically meaningful slowing of cognitive decline in early-stage AD by targeting soluble Aβ protofibrils. Approved based on rigorous clinical trial data, it reflects a paradigm shift toward targeting the underlying pathology of Alzheimer's disease. This monograph summarizes the pharmacology, evidence, safety, and therapeutic potential of Lecanemab.

🧪 Sample Sections / Headers

⚙️ Mechanism of Action

Lecanemab is a monoclonal antibody selectively targeting soluble Aβ protofibrils, believed to be the most neurotoxic form of amyloid aggregates. By promoting immune-mediated clearance, it reduces amyloid plaque deposition, thereby slowing neurodegeneration.

📊 Key Clinical Trials & Evidence

CLARITY-AD (Phase 3): Showed 27% slower cognitive decline (CDR-SB) over 18 months vs placebo
Study 201 (Phase 2): Demonstrated dose-dependent plaque reduction and cognitive benefits
Safety: Risk of ARIA-E and ARIA-H in ~10–15% of patients, especially APOE4 carriers

📋 Indications, Dosage & Administration

Indicated for patients with confirmed early-stage Alzheimer’s disease (MCI or mild dementia)
Administered via IV infusion every 2 weeks (10 mg/kg)
Amyloid PET or CSF confirmation required before initiation

✅ Conclusion & Key Takeaways

First FDA-approved DMT for early Alzheimer’s with demonstrated impact on disease progression
Targets soluble Aβ protofibrils, a key contributor to neurotoxicity
Clinical trials show modest but meaningful cognitive benefits
ARIA risk and cost remain critical considerations
Ongoing trials may further define real-world utility and long-term safety