An experimental Alzheimer’s drug developed by Eisai and Biogen significantly slowed cognitive and functional decline in a large trial of patients in the early stages of the disease, the companies said Tuesday. 

The injected drug, lecanemab, slowed progress of the brain-wasting disease by 27% compared with a placebo, meeting the study’s main goal and offering an apparent win for the companies and potentially for patients and their families desperate for an effective treatment. 

Eisai said the results from the 1,800-patient trial prove the longstanding theory that removal of sticky deposits of a protein called amyloid beta from the brains of people with early Alzheimer’s can delay advance of the debilitating disease. 

“It’s not a huge effect, but it’s a positive effect,” said Ronald Petersen, director of the Mayo Clinic Alzheimer’s Disease Research Center in Rochester, Minnesota, adding that the results were extremely important for Alzheimer’s research. 

“This means that treating amyloid is a step in the right direction,” he said. 

Results considered a “win”

Wall Street analysts, such as Salim Syed at Mizuho Securities, have said the results would be considered a “win” if lecanemab slowed the rate of decline by about 25%, and that shares of both companies could jump on the news. 

Shares of Biogen and Eisai were halted, but shares of Eli Lilly, which is also developing an Alzheimer’s drug, were up 6.7% in after-hours trading. 

Lecanemab, like the companies’ previous drug Aduhelm, is an antibody designed to remove those amyloid deposits. Unlike Aduhelm, lecanemab targets forms of amyloid that have not yet clumped together. 

The so-called amyloid hypothesis has been challenged by some scientists, particularly after the U.S. Food and Drug Administration’s controversial approval of Aduhelm in 2021 based on its plaque-clearing ability rather than proof that it helped slow cognitive decline. The decision came after the FDA’s own panel of outside experts had advised against approval. 

Aduhelm was the first new Alzheimer’s drug approved in 20 years after a long list of high-profile failures for the industry. 

Eisai, leader of the 50-50 partnership’s lecanemab program, is seeking FDA approval under the same accelerated pathway as Aduhelm, with a decision expected in early January. But on Tuesday, the Japanese drugmaker said it would use the new efficacy results to submit lecanemab for traditional FDA review. 

The company said it will also seek authorization in Japan and Europe during its current fiscal year, ending March 31. 

The Phase III trial evaluated the drug’s ability to reduce cognitive and functional decline based on the Clinical Dementia Rating-Sum of Boxes (CDR-SB), a numerical scale used to quantify the severity of dementia in patients in areas such as memory, orientation, judgment and problem-solving and personal care. 

Brain swelling 

The rate of ARIA-E, a brain swelling side effect associated with anti-amyloid treatments, was 12.5% in the lecanemab group, versus 1.7% in the placebo group. 

While the side effect showed up on imaging, many of these cases were not symptomatic, the companies said. Symptomatic brain swelling was seen in 2.8% of those in the lecanemab group and none of the placebo group, they said. 

The trial also tracked the rate of micro hemorrhages in the brain, which occurred at a rate of 17% in the lecanemab group, and 8.7% in the placebo group. 

The total incidence of both conditions was 21.3% in the lecanemab group and 9.3% in the placebo group, rates that fell within an expected range, the companies said. 

Petersen said the side effect was present, but much less than with Aduhelm, and “certainly tolerable.” 

Aduhelm’s approval was a rare bright spot for Alzheimer’s patients, but critics have called for more evidence that amyloid-targeting drugs are worth the cost. 

The controversy and reluctance by some payers to cover Aduhelm led Biogen to slash the drug’s price to $28,000 per year from an initial $56,000. 

But Medicare, the U.S. government health plan for people 65 and older, this year said it would only pay for Aduhelm if patients were enrolled in a valid clinical trial, which sharply curtailed the medication’s use. Since Alzheimer’s is a disease of aging, an estimated 85% of patients eligible for the drug are covered by the government plan. 

The number of Americans living with Alzheimer’s is expected to rise to about 13 million by 2050 from more than 6 million currently, according to the Alzheimer’s Association. Globally, that figure could rise to 139 million by 2050 without an effective treatment, according to Alzheimer’s Disease International. 
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