Eisai Co., Ltd. is a Japanese pharmaceutical company headquartered in Tokyo, specializing in oncology, neurology, and specialty care. Founded in 1941, Eisai is a key player in Alzheimer's disease research, having co-developed lecanemab (Leqembi) with Biogen — the first amyloid-targeting antibody to receive full FDA approval.
| Attribute |
Details |
| Ticker |
TSE: 4523 |
| Headquarters |
Tokyo, Japan |
| Founded |
1941 |
| CEO |
Haruo Naito (CEO) |
| Employees |
~10,000 |
| Revenue |
~$6 billion (FY2023) |
- Mechanism: Amyloid-beta monoclonal antibody targeting Aβ protofibrils
- Target: Protofibrils of amyloid-beta ( soluble oligomers)
- Approval: FDA accelerated approval January 2023, full approval July 2023
- Developer: Jointly developed with Biogen
- Status: Marketed in US, Japan, China, South Korea, Taiwan, Israel
- Clinical Trial: Clarity AD (NCT04437511)
- Efficacy: 27% slowing of clinical decline (CDR-SB) in Clarity AD; 31% slower decline in amyloid-related imaging abnormalities (ARIA)
- Sales: ~$18M in Q3 2024 (early launch phase)
Leqembi Mechanism of Action:
Leqembi binds to protofibrils — the soluble, toxic oligomeric forms of amyloid-beta that are believed to be primary drivers of synaptic dysfunction and cognitive decline in AD. By selectively targeting protofibrils rather than monomeric Aβ or plaque, Leqembi reduces both soluble toxic species and existing amyloid plaques.
| Drug |
Mechanism |
Phase |
Indication |
| Lecanemab (Leqembi) |
Anti-amyloid β protofibril mAb |
Approved |
Early AD |
| E2814 |
Anti-tau mAb (Mosaic) |
Phase 1/2 |
AD (DIAN-TU) |
| E2027 |
PDE9 inhibitor |
Phase 2 |
AD |
| E2028 |
Tau aggregation inhibitor |
Phase 1 |
AD |
¶ E2814 (Anti-tau Monoclonal Antibody)
- Mechanism: Anti-tau monoclonal antibody designed to bind multiple phospho-tau epitopes
- Target: Pathological phosphorylated tau in brain
- Phase: Phase 1/2 being evaluated in DIAN-TU trial (Dominantly Inherited Alzheimer Network Trials Unit)
- Rationale: Complement amyloid-targeting with tau-focused approach; prevent spread of tau pathology across brain regions
- Unique Feature: "Mosaic" design targets multiple tau epitopes for broader coverage
- Clinical Trials: DIAN-TU (NCT01760005)
- Research: First-in-human study published showing safety and target engagement
DIAN-TU Study Context:
The DIAN-TU platform tests therapies in individuals with autosomal dominant AD mutations, allowing for earlier intervention before symptom onset. E2814 is being evaluated alongside other anti-amyloid and anti-tau candidates.
- Mechanism: Phosphodiesterase 9 (PDE9) inhibitor
- Target: cGMP signaling pathway in neurons
- Phase: Phase 2
- Rationale: Enhance synaptic plasticity and memory function by increasing cGMP levels
- Rationale Basis: PDE9 is enriched in brain regions affected by AD and is involved in NMDA receptor-mediated signaling
- Mechanism: Small molecule inhibitor of tau aggregation
- Target: Pathological tau protein aggregation
- Phase: Phase 1
- Rationale: Prevent formation of neurofibrillary tangles (NFTs)
- Mechanism: BACE (Beta-Secretase) inhibitor
- Target: BACE1 enzyme
- Status: Discontinued Phase 2/3 (2021)
- Reason: Safety concerns (liver toxicity, cognitive worsening in some patients)
- Lesson: Taught the field about risks of aggressive amyloid reduction
Eisai has limited Parkinson's disease programs. The company focuses primarily on Alzheimer's disease. No significant PD candidates in current pipeline.
| Drug |
Mechanism |
Indication |
| Fycompa (perampanel) |
AMPA receptor antagonist |
Epilepsy |
| Zebinix/Bexolvera (eslicarbazepine) |
Sodium channel blocker |
Epilepsy |
| Drug |
Mechanism |
Indication |
| Lenvima (lenvatinib) |
VEGFR, FGFR, PDGFRA, KIT inhibitor |
Multiple cancers |
| Halaven (eribulin) |
Microtubule inhibitor |
Breast cancer |
| Kisplyx (lenvatinib) |
VEGFR inhibitor |
Renal cell carcinoma |
- Scope: Joint development and commercialization of lecanemab (Leqembi)
- Structure: 50/50 profit-sharing in US; Eisai leads in Japan and Asia; Biogen receives royalties in other regions
- History: Established in 2014; first major collaboration for AD therapeutics
- University of Cambridge — Tau research collaboration for E2814
- DIAN-TU Consortium — Anti-tau antibody development in familial AD
- Various biomarker partnerships with academic medical centers for patient selection and monitoring
| Year |
Revenue |
Key Products |
| 2023 |
$6.0B |
Leqembi, Lenvima, Fycompa |
| 2022 |
$5.9B |
Lenvima, Halaven, Fycompa |
| 2021 |
$5.7B |
Lenvima, Halaven, Fycompa |
- Haruo Naito — Chief Executive Officer
- Ivan Cheung — President & CEO, Eisai Inc. (US)
- Masamichi Ohno — President, Eisai Japan