Leqembi’s ¥29.3 Billion Quarter

A sales figure is a strange way to measure memory.

It can tell investors how many yen crossed company accounts. It can suggest that neurologists are writing more prescriptions, hospitals have built treatment pathways and insurers are paying. It cannot tell a daughter whether her father still remembers the walk to the station, whether a husband can continue managing the household money or whether eighteen months gained on a clinical scale will feel large enough inside one family’s life.

That tension sits inside the ¥29.3 billion in preliminary global Leqembi sales Eisai disclosed on July 29. The anti-amyloid antibody, known generically as lecanemab, is no longer a scientific promise waiting for a pivotal trial. It is a commercial medicine in 53 countries and regions, a source of royalty income for Sweden’s BioArctic, a shared product for Eisai and Biogen, and the center of Eisai’s effort to build an Alzheimer’s treatment franchise.

The number also contains a century of scientific argument. It reaches back to a woman named Auguste Deter, whose disorientation and lost language helped Alois Alzheimer describe an unfamiliar disease in 1906; to a family in northern Sweden whose inherited mutation made amyloid clump unusually quickly; to generations of failed drugs; and to a clinical trial whose benefit was statistically clear but modest enough to demand careful explanation.

Leqembi is a milestone because it slows decline in selected people with early Alzheimer’s disease. It is not a cure, it does not rebuild dead neurons, and it is not appropriate for everyone with dementia. Its commercial ascent matters precisely because the medicine is both consequential and limited.

What actually grew

The United States supplied slightly more than half of the quarter’s global revenue. Sales there reached ¥15.4 billion, up 69 percent from ¥9.1 billion in the same period of 2025. Japan rose 11 percent to ¥6.1 billion from ¥5.5 billion. China fell on the reported comparison, to ¥4.8 billion from ¥7.7 billion.

That Chinese decline is more accounting than collapse. The 2025 figure included about ¥5.3 billion of inventory accumulated by a distributor. Remove that exceptional stockbuilding and the year-earlier China base was roughly ¥2.4 billion; on that simple adjusted comparison, the new ¥4.8 billion is about twice as large. BioArctic expressed the cleaner comparison through royalties: excluding the stockpiling effect, its second-quarter royalty revenue grew about 43 percent.

The remaining countries contributed an arithmetic remainder of about ¥3.0 billion, up from roughly ¥0.8 billion a year earlier. That residual is not a separately reported company segment and should not be overinterpreted, but it shows a franchise beginning to extend beyond its first three markets.

Market	Apr–Jun 2026	Apr–Jun 2025	What the comparison says
United States	¥15.4bn	¥9.1bn	Up 69.2%; the principal driver of reported growth.
Japan	¥6.1bn	¥5.5bn	Up 10.9%; growth inside a tightly specified treatment system.
China	¥4.8bn	¥7.7bn	Down 37.7% as reported, but 2025 included roughly ¥5.3bn of one-time distributor stockbuilding.
Other markets	About ¥3.0bn	About ¥0.8bn	Calculated remainder, not a separately disclosed regional total.
Global	¥29.3bn	¥23.1bn	Up 26.8%; preliminary and unaudited.

Biogen reported the same global in-market activity as $184 million, up 15 percent year on year. At the ¥163.41 reference rate used in this edition, ¥29.3 billion converts to about $179 million. The figures are close, but currency translation and partner presentation make them unsuitable for false precision. The yen disclosure is the clean base for evaluating Eisai.

The target hidden inside the number

Eisai recorded ¥88.0 billion in Leqembi sales in the fiscal year ended March 2026, double the prior year’s ¥44.3 billion. It forecasts ¥143.5 billion for the year ending March 2027, another 63 percent increase. The first ¥29.3 billion represents 20.4 percent of that annual target.

Simple arithmetic shows the slope ahead. Eisai needs another ¥114.2 billion over the final three quarters—an average of about ¥38.1 billion a quarter, almost 30 percent above the April–June pace. That is an inference, not company guidance, and pharmaceutical revenue is not evenly distributed. The late-August U.S. launch of the newly approved at-home initiation regimen, additional maintenance approvals and geographic rollout could change the shape of the year.

Sequential momentum is real. Calendar Q1 sales were ¥26.2 billion, so calendar Q2 added ¥3.1 billion, or 11.8 percent. But calendar Q1 belonged to the final quarter of Eisai’s previous fiscal year. Mixing those labels can make a clean chart tell a false story. For Eisai, the ¥29.3 billion quarter is the opening movement, not the second checkpoint, of the ¥143.5 billion target year.

A treatment, not a rewind button

Leqembi is an antibody designed to bind aggregated forms of amyloid beta, with particular affinity for soluble protofibrils. It is indicated for Alzheimer’s disease, but treatment was studied and should be initiated at the mild cognitive impairment or mild dementia stage in patients whose amyloid pathology has been confirmed. That is a much narrower group than “people with memory problems” or even “people with dementia.”

The decisive Clarity AD trial enrolled 1,795 participants. After 18 months, the average change on the Clinical Dementia Rating–Sum of Boxes was 1.21 points with lecanemab and 1.66 with placebo. The 0.45-point difference represented 27 percent less decline relative to placebo on that scale. Amyloid plaques also fell substantially, and all key secondary clinical endpoints favored lecanemab.

The often repeated “27 percent” requires discipline. It does not mean memory improved by 27 percent. It does not mean 27 percent of patients were cured, or that every treated person received the same benefit. It is the relative difference between two average rates of worsening over eighteen months. Both groups declined; the treated group declined more slowly.

Whether 0.45 points is meaningful cannot be answered by a slogan. A population average can conceal larger benefit for some people and none for others. A small delay may matter intensely if it preserves independent travel, cooking or conversation; it may feel disappointing beside the cost, medical burden and risk. That decision belongs in a candid conversation among patient, care partner and specialist, not in a revenue chart.

The risk appears on an MRI

The defining safety issue is amyloid-related imaging abnormalities, or ARIA. ARIA-E involves edema or fluid accumulation; ARIA-H involves microhemorrhages and deposits of blood-breakdown products. These changes are often asymptomatic and resolve, but they can cause headache, confusion, dizziness, vision disturbance, nausea or seizures. Rare events can be serious, life-threatening or fatal.

In Clarity AD, ARIA-E occurred in 12.6 percent of lecanemab recipients and 1.7 percent of placebo recipients. ARIA-H occurred in 17.3 percent and 9.0 percent, respectively. Infusion-related reactions occurred in 26.4 percent of the lecanemab group. Risk is higher in people with two copies of the APOE ε4 allele, which is why U.S. prescribing information says APOE ε4 testing should be performed before treatment to inform the discussion.

Baseline and follow-up MRI scans are not optional decoration around the drug. They are part of the treatment. So are an emergency plan, review of anticoagulant use and a clinical team able to interpret symptoms and imaging. An at-home injector may remove a trip to an infusion chair; it does not remove the brain, genetic and bleeding risks that make supervision necessary.

From Auguste Deter to the Arctic mutation

In November 1906, Alois Alzheimer described the case of Auguste Deter, a woman admitted in Frankfurt at 51 after developing profound memory, language and behavioral changes. After her death he examined her brain and reported the plaques and neurofibrillary tangles that would become the disease’s pathological signatures. The microscope saw the ruins. It could not yet reveal the molecular sequence that built them.

Later work identified amyloid beta as a major component of plaques and linked rare inherited changes in amyloid precursor protein to early-onset disease. The “amyloid cascade” hypothesis proposed that abnormal amyloid accumulation stood upstream of tau pathology, neuronal injury and clinical decline. It became enormously influential—and vulnerable to a hard objection: if amyloid was central, why did so many amyloid-targeting drugs fail?

A family in northern Sweden supplied a more specific clue. Lars Lannfelt’s group identified an APP mutation, published in 2001 and named “Arctic” for the family’s origin. The mutation accelerated formation of soluble amyloid protofibrils. It suggested that the most relevant target might not be only the dense plaque visible at the end of aggregation, but mobile intermediate clusters that can interact with neurons.

Lannfelt and Pär Gellerfors founded BioArctic in 2003. In 2005, researchers at Uppsala University isolated mAb158, an antibody that selectively recognized protofibrils; BioArctic and Eisai began a research collaboration the same year. Eisai licensed the humanized candidate BAN2401 in 2007. Biogen joined development and commercialization in 2014. BAN2401 eventually became lecanemab.

The cemetery of anti-amyloid hopes

Leqembi’s origin story can sound inevitable when read backward. It was not. Bapineuzumab failed to show clinical benefit in Phase 3. Solanezumab repeatedly missed major endpoints. Secretase inhibitors intended to block amyloid production ran into toxicity or worsening cognition. Each disappointment strengthened the argument that amyloid was the wrong target—or that treatment was being attempted too late, against the wrong form of the protein, at an ineffective dose or in patients without adequate biomarker confirmation.

Then came Aduhelm. The FDA granted aducanumab accelerated approval in 2021 based on plaque reduction despite conflicting clinical trial results and opposition from its advisory committee. The decision triggered a storm over evidence, price and regulatory standards. Medicare restricted coverage; uptake remained extremely limited; Biogen discontinued development and commercialization in 2024.

Leqembi did something different. Its 2023 traditional U.S. approval followed a large confirmatory trial that showed both plaque removal and a measured clinical benefit. That did not end debate over clinical meaningfulness, safety or cost. It changed the debate from “does an anti-amyloid antibody alter decline at all?” to “for whom is the demonstrated slowing worth the risk and burden?”

Eli Lilly’s donanemab, sold as Kisunla, added competition after U.S. and Japanese approvals in 2024. It is administered intravenously every four weeks and has a strategy that may allow stopping after amyloid clearance under its label. Leqembi began as every-two-week infusion and argues for continued suppression, with monthly IV maintenance and weekly subcutaneous options. There is no direct head-to-head outcomes trial proving one is superior. Commercial positioning should not be mistaken for comparative evidence.

Japan as both home market and proving ground

Japan approved Leqembi on September 25, 2023, for slowing progression of mild cognitive impairment and mild dementia due to Alzheimer’s disease. National insurance coverage began December 20. The official 2023 price was ¥45,777 for a 200-milligram vial; the Central Social Insurance Medical Council estimated annual drug cost at about ¥2.98 million for a typical regimen.

The price came with boundaries. Japan’s optimal-use guidelines require the proper cognitive stage, confirmation of amyloid by PET or cerebrospinal-fluid testing, MRI capability, trained physicians and facilities able to recognize and manage ARIA. The government forecast that treated patients would remain a fraction of the much larger disease population, reaching about 32,000 at a projected 2031 peak under the assumptions used for pricing.

That gap is fundamental. Health ministry estimates place 4.716 million older people in Japan with dementia in 2025 and 5.643 million with mild cognitive impairment. By 2040, the estimates rise to 5.842 million and 6.128 million. Not all dementia is Alzheimer’s; not all MCI is caused by Alzheimer’s; not all eligible people will want or safely receive an antibody. The addressable treatment population is created by a chain of tests and judgments, not by multiplying prevalence by price.

Japan’s ¥6.1 billion quarter shows that a pathway exists. It does not prove equal access. Amyloid PET scanners, lumbar-puncture services, dementia specialists and MRI slots are concentrated unevenly. Older people living alone or far from a specialist center may face a larger practical barrier than patients near major urban hospitals. A treatment that must begin early makes delay itself a form of exclusion.

The route to the drug is the market

For ordinary medicines, a company can expand sales by persuading more doctors to prescribe. Leqembi requires an ecosystem. A person must notice subtle change, enter a clinic before disease becomes too advanced, complete cognitive assessment, rule out other causes, demonstrate amyloid, obtain baseline imaging, understand APOE-associated risk and return for monitoring. The infusion center, radiology department, payer and care partner are part of the product’s real-world capacity.

This is why diagnostics may determine commercial success as much as antibody supply. PET is informative but costly and geographically constrained. Cerebrospinal-fluid testing is established but invasive. Blood-based biomarkers could make triage easier, although a blood test is not a stand-alone diagnosis and abnormal results still require clinical interpretation and, depending on the treatment pathway, confirmation.

In the United States, Medicare broadened coverage after traditional FDA approval, but clinicians must submit information through a qualifying registry. Coverage solved one bottleneck without eliminating specialist, scan, infusion and out-of-pocket burdens. In Japan, universal insurance and the high-cost medical expense benefit reshape the patient bill, but capacity and eligibility remain limiting.

The most valuable commercial asset may therefore be a functioning pathway rather than a patent alone. Once a hospital trains staff, establishes MRI schedules and learns to counsel families, it can treat more patients. It may also use that infrastructure for a competitor. Eisai’s task is to make Leqembi the medicine around which the pathway forms without confusing first-mover infrastructure with permanent clinical superiority.

From one medicine to a franchise

“Franchise” is pharmaceutical language for extending a product across formulations, dosing schedules, geographies and stages of disease. For Leqembi, that strategy is visible. The original regimen was an intravenous infusion every two weeks. Monthly intravenous maintenance after 18 months is approved in eight countries, including Japan, the United States, China and the United Kingdom. Applications are pending elsewhere.

In August 2025, the United States approved the Leqembi Iqlik autoinjector for weekly maintenance after the initial 18 months. On July 13, 2026, the FDA approved subcutaneous initiation at home: 500 milligrams weekly, administered as two 250-milligram injections by a patient or caregiver. Eisai expects U.S. availability in late August.

The convenience is meaningful. It could remove dozens of infusion-center visits and release capacity for new patients. But the FDA emphasized an evidentiary nuance: the subcutaneous formulation was not separately tested in a large clinical-outcomes trial. Approval relied on the demonstrated efficacy of intravenous lecanemab plus evidence of equivalent exposure and similar amyloid reduction. “At home” describes administration location, not freedom from specialist screening and safety monitoring.

Japan is on a different regulatory clock. Eisai submitted the subcutaneous formulation in November 2025, but it remained under review at the reporting cutoff. The U.S. approval does not authorize Japanese use. Conflating global brand strategy with local approval is exactly how a franchise story becomes medical misinformation.

Beyond formulation, the AHEAD 3-45 trial is studying lecanemab in people who are clinically normal but have intermediate or elevated brain amyloid. It was fully enrolled in 2024 and is designed to run for four years. A positive result could move treatment still earlier and enlarge the eligible population; a negative or equivocal result would mark a boundary. Until results arrive, presymptomatic use is research, not an approved promise.

Layer of the franchise	Status at the cutoff	Why it matters
IV initiation	10 mg/kg every two weeks; established clinical-outcomes evidence.	Current foundation of treatment in Japan and many markets.
IV maintenance	Every four weeks after 18 months, approved in eight countries.	Reduces visit frequency while maintaining continued treatment.
U.S. autoinjector	Weekly maintenance approved in 2025; at-home initiation approved July 2026.	Moves administration away from the infusion chair, but not away from monitoring.
Japan autoinjector	Application submitted November 2025; under review.	No Japanese approval should be inferred from the U.S. decision.
Preclinical Alzheimer’s	AHEAD 3-45 trial ongoing.	Potential future expansion, not established benefit or approved use.

What the real world can—and cannot—answer

Randomized trials establish whether a treatment caused an average difference under controlled conditions. Post-approval studies ask how the medicine performs among older, more varied patients and ordinary clinics. Both kinds of evidence matter; they do not carry equal protection against bias.

An Eisai-sponsored U.S. claims analysis reported that 78.4 percent of patients remained on Leqembi at 18 months. At the July 2026 Alzheimer’s Association International Conference, the company’s retrospective LEADER study reported that 75.9 percent of enrolled patients were stable and 6.6 percent improved over an average 17 months.

Those results are encouraging signals about persistence and treated cohorts. They are not a replacement for Clarity AD. LEADER had no randomized concurrent placebo group; clinicians selected patients for treatment; people who stopped early or lacked follow-up can affect the observed picture; “stable” depends on the study’s measures and interval. Company sponsorship does not make a result false, but it makes transparent design and independent replication especially important.

Sales data are further removed. More revenue can mean more patients, longer persistence, higher inventory, favorable currency, more doses per patient or expansion into higher-priced markets. Without patient counts and exposure-adjusted safety data, ¥29.3 billion cannot tell readers how benefit and harm are distributed.

The responsibility inside the revenue

Leqembi has crossed a threshold that most experimental Alzheimer’s drugs never reached. It survived the transition from animal model to human trial, from biomarker effect to clinical outcome, from accelerated approval to traditional approval, and from one market to dozens. A ¥29.3 billion quarter reflects that achievement.

It also increases the obligation to speak accurately. A relative slowing is not memory returned. Amyloid removal is not the same as cure. A home injector is not an unsupervised medicine. Observational stability is not randomized proof. Global approval does not erase local labels. Sales growth does not reveal equal access, and a franchise is not a guarantee that every life-cycle extension will work.

Yet modest does not mean meaningless. Alzheimer’s disease steals continuity in increments: a name, a route, a recipe, the sequence of a familiar morning. If treatment can preserve some function for some people for longer, that time can hold value no quarterly table knows how to price.

The honest interpretation of ¥29.3 billion therefore lies between triumph and dismissal. It is evidence that a once-controversial therapeutic idea has become a functioning global market. The measure of success will not be whether the number grows alone. It will be whether growth brings earlier diagnosis, safer delivery, fairer access and time that patients and families recognize as their own.

Reporting Notes and Sources

Financial, regulatory and medical information was checked through July 30, 2026, at 10:12 a.m. JST. Eisai’s sales disclosure is preliminary and unaudited. Percentage changes and the “other markets” residual were calculated from disclosed figures and rounded. This article distinguishes calendar Q2 2026 from Eisai fiscal Q1 2026 and does not infer patient counts from revenue. Medical information is explanatory and not individual treatment advice.

• Eisai: preliminary April–June 2026 Leqembi revenue and major-market breakdown
• BioArctic: ¥29.3 billion calendar-Q2 sales, royalty and China stockpiling comparison
• Biogen: 2026 second-quarter results and global in-market sales in U.S. dollars
• BioArctic: ¥26.2 billion calendar-Q1 2026 sales
• BioArctic: Eisai’s ¥143.5 billion FY2026 forecast and 63-percent growth target
• New England Journal of Medicine: Clarity AD efficacy and safety results
• U.S. FDA: 2023 traditional approval, population and confirmatory evidence
• U.S. FDA: July 2026 at-home initiation approval, evidentiary basis and ARIA warnings
• Eisai: Leqembi Iqlik initiation regimen and expected late-August U.S. availability
• PMDA: Japanese lecanemab review, indication, efficacy, safety and approval conditions
• Ministry of Health, Labour and Welfare: Japanese price, annual cost estimate, optimal-use conditions and market projection
• Ministry of Health, Labour and Welfare: dementia and MCI prevalence estimates through 2060
• BioArctic: Arctic mutation, mAb158, BAN2401 and partnership chronology
• Nature Neuroscience / Europe PMC: 2001 primary report of the Arctic APP mutation
• Dialogues in Clinical Neuroscience / NIH: Auguste Deter and the discovery of Alzheimer’s disease
• U.S. FDA: 2024 Kisunla approval and dosing
• PMDA: Japanese donanemab review and early-Alzheimer’s evidence
• U.S. CMS: Medicare coverage and registry after traditional approval
• Eisai: company-sponsored U.S. real-world treatment-persistence analysis
• BioArctic: company-sponsored LEADER retrospective study presented at AAIC 2026