PETRI DISH PERSPECTIVES

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PETRI DISH PERSPECTIVES

Episode 40: Eisai

January 29, 2026 • Manead Khin • Season 1 • Episode 40

0:00 | 23:23

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What does it take to spend decades chasing one of medicine’s hardest problems while the rest of the industry walks away?

In this episode, we explore the remarkable story of Eisai, the Japanese pharmaceutical company that built its global identity around Alzheimer’s disease. From its founding during World War II and early commitment to ethical medicine, to the blockbuster success of Aricept, and finally the long, controversial road to Leqembi, Eisai’s journey is one of persistence, philosophy, and scientific conviction.

We break down how Eisai partnered with Biogen, why leadership under Haruo Naito stayed the course when others exited neuroscience, and how a Japan-based company became a global force in CNS drug development. Along the way, we examine Eisai’s approach to risk, regulation, M&A, and what its future looks like beyond Alzheimer’s.

This is a story about long-term thinking in a short-term industry and what happens when belief outlasts doubt.

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Hello and welcome to Petri Dish Perspectives, the podcast where we geek out about science and the companies shaping the future of healthcare. I’m your host, Manead, and I’m a PhD scientist by training, biotech storyteller by choice. With every new episode released on Thursday, my goal is to deliver digestible pieces of information on healthcare companies under 30 mins.

Eisai is one of the most revealing case studies in global pharma because it defies almost every modern incentive structure. While most large pharmaceutical companies rotate in and out of therapeutic areas based on investor sentiment, Eisai stayed committed to Alzheimer’s disease for decades, through repeated scientific failures, public skepticism, and enormous financial risk. This episode is about how a mid-sized Japanese pharma built a global identity around one of medicine’s hardest problems, how leadership philosophy shaped scientific persistence, and why Eisai’s choices continue to influence how neurodegenerative diseases are developed, regulated, and debated today.

Quick disclaimer, I give full credit to the original articles cited in the references in the transcript!

Grab a coffee or tea, settle in, and let’s jump in!

Segment 1: Founding, Early History, and Corporate Identity

Born in 1889 in Fukui Prefecture, Toyoji Naito was a quintessential self-made man whose journey from a second-grade dropout to a titan of the pharmaceutical industry is nothing short of cinematic. After a period of rigorous self-study and early roles in German and British trading firms, Naito’s perspective was shaped by a unique blend of international commerce and hands-on medical experience gained as a military medic.

His career truly ignited in 1915 at the Tanabe Motosaburo Store, where he spent 29 years rising from a trade clerk to Managing Director. During this time, he revolutionized the Japanese medicine cabinet by developing legendary products like Salomethyl and Halibut Liver Oil.

In 1941, driven by a conviction that R&D was the true heartbeat of medicine, he established Nihon Eisai Co., Ltd. By 1955, the company was renamed simply Eisai Co., Ltd., a name now synonymous with global healthcare.

Eisai was founded during a turbulent period marked by war and resource scarcity. Toyoji Naito was not a traditional industrialist. He believed that pharmaceuticals carried a moral obligation to society, rooted in a philosophy that emphasized dignity, compassion, and service to patients. This belief later crystallized into Eisai’s defining concept of “human health care,” which prioritized patient well-being over short-term profit.

After World War II, Japan’s pharmaceutical industry was fragmented and underdeveloped. Eisai focused on rebuilding trust by emphasizing ethical promotion, physician education, and consistent product quality. Unlike many Japanese companies that diversified into chemicals or consumer products, Eisai remained narrowly focused on pharmaceuticals, believing specialization was essential for credibility.

Eisai went public relatively early compared to many Japanese firms, listing on the Tokyo Stock Exchange in 1961. The IPO provided capital for research expansion but did not fundamentally alter Eisai’s governance philosophy. The company remained tightly controlled by internal leadership rather than external financial pressures, allowing it to pursue long-term R&D strategies that would later distinguish it from peers.

From my research, it looks like Toyoji had 5 children, however, he only passed on the role of CEO to one of them. Even after passing the torch of leadership to his son, Yuji Naito, in 1966, his commitment to the advancement of science remained steadfast through the establishment of the Naito Foundation, marking a legacy of innovation that spanned 88 years and transformed the landscape of Japanese healthcare.

Unfortunately, he passed away in 1978 at the age of 88.

Segment 2: Leadership, Haruo Naito, and the Rise of Aricept

Then, the grandson came into the picture. Haruo Naito, son of Yuji, joined Eisai in 1980 after training in pharmacology and health economics. He rose steadily through research and strategic roles before becoming CEO in 1988. Haruo Naito became the modern embodiment of the founder’s philosophy, translating it into a global corporate context.

Under Haruo Naito’s leadership, Eisai made a decisive bet on central nervous system disorders, particularly Alzheimer’s disease. This was a controversial move at the time, as neuroscience drug development was already considered high risk.

Aricept, known generically as donepezil, emerged from Eisai’s internal research into acetylcholinesterase inhibitors. The scientific rationale stemmed from the cholinergic hypothesis of Alzheimer’s, which suggested that declining acetylcholine levels contributed to cognitive symptoms. Eisai scientists identified donepezil as a compound that balanced efficacy with tolerability, a critical factor for elderly patients.

Aricept was approved in Japan in 1996 and in the United States shortly thereafter. It became the first Alzheimer’s drug to achieve widespread global adoption, eventually generating billions in annual revenue. Eisai partnered with Pfizer for commercialization in the US and Europe, marking one of Eisai’s earliest large-scale global collaborations. While Aricept did not halt disease progression, it established Eisai as a leader in neurodegenerative disease and provided both capital and institutional confidence to pursue more ambitious programs.

Segment 3: From Aricept to Biogen and the Alzheimer’s Long Game

Despite Aricept’s success, Eisai leadership viewed it as a partial victory rather than a solution. The company reinvested heavily into Alzheimer’s research, particularly amyloid biology. As repeated late-stage failures plagued the field in the 2000s, many pharmaceutical companies exited neuroscience altogether.

Eisai took a different path. Recognizing the scale and cost of Alzheimer’s trials, the company sought a partner that shared its scientific commitment. This led to discussions with Biogen, which had its own legacy in neuroscience and immunology. The collaboration was formalized in 2014, with Eisai assuming responsibility for global clinical development and regulatory strategy, while Biogen contributed scientific expertise and commercial reach.

Their joint focus became lecanemab, a monoclonal antibody designed to selectively target soluble amyloid protofibrils. Eisai believed this approach could reduce amyloid toxicity earlier in the disease process, potentially leading to meaningful clinical benefit.

Segment 4: Leadership During Crisis and the Leqembi Approval

By the time lecanemab reached late-stage development, Alzheimer’s drug approvals had become politically and scientifically fraught. Biogen’s Aduhelm approval in 2021 triggered widespread backlash over regulatory standards and reimbursement.

Eisai’s leadership, still under Haruo Naito, took a more conservative and data-driven approach. Eisai insisted on confirmatory trials and emphasized transparency with regulators. In 2023, lecanemab, branded as Leqembi, received traditional FDA approval based on demonstrated clinical benefit in slowing cognitive decline.

The approval was historic but controversial. Safety concerns, cost debates, and questions about real-world impact dominated public discourse. Eisai framed Leqembi not as a cure, but as a foundational step toward disease modification, reflecting its long-standing philosophical restraint.

Segment 5: Eisai’s Broader Portfolio and Drug Development Philosophy

Beyond Alzheimer’s, Eisai developed and marketed several notable drugs across neurology and oncology. Fycompa, an anti-epileptic drug, represented Eisai’s continued investment in CNS disorders beyond dementia. In oncology, Eisai achieved global success with Halaven, a microtubule dynamics inhibitor for metastatic breast cancer, discovered through Japanese marine natural product research.

These drugs reinforced Eisai’s preference for differentiated mechanisms rather than crowded markets. Eisai often accepted smaller commercial footprints in exchange for scientific novelty and unmet need.

While Alzheimer’s remains central, Eisai has actively diversified into oncology, neurology, and digital health. The company has invested in real-world evidence platforms, patient-reported outcomes, and disease progression modeling, particularly for neurological conditions.

This strategy reflects Eisai’s belief that future drug value will depend on holistic disease management rather than single-molecule efficacy. Eisai has also explored digital therapeutics and data-driven trial design to reduce development timelines in complex diseases.

Segment 6: M&A, Partnerships, and Capital Allocation

Eisai has historically avoided large, transformative acquisitions. Instead, it favors partnerships, co-development deals, and selective licensing. The Biogen collaboration exemplifies this approach. Eisai’s capital allocation strategy prioritizes internal R&D and scientific continuity over aggressive expansion.

That said, Eisai has signaled openness to targeted acquisitions, particularly in early-stage neuroscience and oncology platforms that align with its expertise.

Segment 7: Becoming a Global Pharma from Japan

Eisai’s global expansion began decades before many Japanese peers. The company established meaningful US and European operations, empowered regional leadership, and localized R&D decision-making. Unlike firms that struggled to globalize culturally, Eisai maintained a cohesive identity grounded in its founding philosophy.

Today, Eisai operates in more than 20 countries, balancing Japanese corporate discipline with global scientific collaboration. Eisai is still headquartered in Tokyo, Japan, with over 10,000 employees worldwide. The company operates a network with more than 40 subsidiaries, 14 major R&D/clinical research sites, and 9 production facilities globally.

Segment 8: What’s Next for Eisai

Looking forward, Eisai stands at a crossroads. Its future depends on whether Alzheimer’s treatment adoption accelerates and whether follow-on therapies can improve efficacy, safety, or convenience.

Eisai continues to invest in next-generation Alzheimer’s candidates, earlier intervention strategies, and combination approaches. At the same time, it must navigate pricing pressure, reimbursement complexity, and growing competition as other amyloid and tau-targeting therapies enter the market.

Segment 9: Lessons from Eisai

Eisai offers a rare lesson in pharmaceutical persistence. It demonstrates that walking away from difficult science is often rational, but staying can redefine an industry. Eisai’s story shows the power and cost of conviction, the tension between cultural values and global capitalism, and the reality that meaningful medical progress is often incremental, controversial, and uncomfortable.

Eisai Co., Ltd. is listed in the United States, but not on a major national exchange like the NYSE or NASDAQ. It trades on the OTC (Over-the-Counter) market via American Depositary Receipts (ADRs) under the ticker symbols ESAIY and ESALF. The company's primary listing is on the Tokyo Stock Exchange. By the time the episode was recorded, Eisai’s market cap is at $8.67B and the stock sits at $7.13.

Outro: Three Key Takeaways

First, Eisai demonstrates that scientific persistence can outlast market skepticism and reshape entire therapeutic fields. Second, leadership philosophy matters deeply in drug development, influencing not just what companies pursue, but how long they stay committed. And third, Eisai’s story shows that global success does not require abandoning cultural identity, but rather translating it thoughtfully into action.

Eisai is not just a pharmaceutical company. It is a long-term experiment in conviction-driven medicine.

This has been Petri Dish Perspectives. I’m Manead. Thanks for listening. See you next Thursday. Good bye.

References

Manead Khin

Host