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HomeMarketBiogen's New Alzheimer's Drug Faces Its Next Test. 4 Big Questions.

Biogen’s New Alzheimer’s Drug Faces Its Next Test. 4 Big Questions.

Biogen and Eisai are working together on lecanemab.

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Adam Glanzman/Bloomberg

Investors are about to learn whether
‘s new Alzheimer’s drug is really as good as it seems.

Two months ago, the Japanese pharmaceutical company announced that lecanemab, its experimental therapy for the disease, performed unexpectedly well in a Phase 3 trial. lt is releasing the full results of the study on Tuesday.

(ticker: BIIB) and Eisai (ESALY) are collaborating on lecanemab’s development.

There had been little reason to expect that the drug would work, before the trial results were announced in September. Enthusiasm for the scientific hypothesis on which the drug is based, which proposes that certain plaques that accumulate in the brain are linked to Alzheimer’s symptoms, had waned after years of disappointments.

What is more, a recent failure was fresh in investors’ minds. Shares of both
and Eisai spiked in June 2021, after the Food and Drug Administration unexpectedly approved Aduhelm, their previous Alzheimer’s disease drug, and then fell back to earth after that drug’s commercial prospects evaporated.

The top-line results announced in September showed that lecanemab slowed the cognitive decline of Alzheimer’s disease patients. Yet while shares of Biogen are up more than 50% since the announcement, the companies have still shared only a press release describing the results of the trial, not the complete results.

That will change on Tuesday evening, when Eisai presents its work at a scientific gathering called the Clinical Trials on Alzheimer’s Disease conference. The company’s presentation is scheduled for 7:50 p.m. Eastern time.

There are lots of factors that could derail the drug’s commercial success. Eisai has filed with the FDA for accelerated approval of lecanemab, but it isn’t certain that the agency will sign off. The deadline for a ruling is Jan. 6. After that, Eisai says it plans to file for full approval by the end of March.

Just as important as the FDA nod is whether the companies can convince the Centers for Medicare and Medicaid Services, which operates the Medicare program, to pay for the drug. It was CMS’s decision not to pay for Aduhelm, Biogen and Eisai’s last crack at an Alzheimer’s drug, that sunk that medicine’s commercial prospects.

Below are some big ideas to watch for on Tuesday.

How clinically significant is lecanemab’s effect?

Eisai said in September that lecanemab slowed cognitive decline by 27%, compared to patients who received a placebo. What that means, exactly, is hard to parse, and investors will be listening closely for more details.

The trial used an 18-point scale known as CDR-SB, which measures cognition and function in dementia patients. That 27% difference between the group that received lecanemab and the placebo group, after 18 months, was less than half a point on the CDR-SB scale.

Eisai will likely address this question directly. In addition to tracking patients using CDR-SB, the trial also used another measure, known as ADCS MCI-ADL, which tracks how patients are able to complete activities associated with daily living. Those results weren’t part of the press release, and will be presented Tuesday; they could confirm the clinical significance of the drug’s effect.

Did the drug’s effect increase over time?

Eisai’s press release said that there were “highly statistically significant changes” in CDR-SB scores “starting as early as six months,” but investors will be interested to see how significant those changes were at different time points. An improvement that appears at six months and increases over time would likely indicate an effective drug. Other results might raise questions.

What about APoE4 carriers?

Analysts expect Eisai to break out results between Alzheimer’s patients who carry a gene known as APoE4, and those who don’t. People who carry the APoE4 gene are thought to be more likely to develop Alzheimer’s. If the lecanemab trial results are far stronger for those patients who carry APoE4, William Blair analyst Myles Minter wrote in a Nov. 11 note, there is a risk that the FDA could approve the drug only for people with that gene.

What will
Roche Holding

A day after the lecanemab presentation, Roche (RHHBY) will present the full results of its Phase 3 trial of gantenerumab, a similar Alzheimer’s antibody therapy. Roche said on Nov. 14 that gantenerumab had failed to slow clinical decline in Alzheimer’s patients, and had performed worse than expected in clearing the brain plaques thought to be linked to Alzheimer’s.

Full data from the trial could help clarify whether its failure can be attributed to the particular characteristics of gantenerumab, or whether it should be seen as a strike against the broad class of drugs, which includes lecanemab.

Write to Josh Nathan-Kazis at


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