The drug, lecanemab, slowed progress of the brain-wasting disease by 27% compared with a placebo, meeting the study's main goal, and potentially offering hope for patients and their families desperate for an effective treatment.
"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.
Eisai, leader of the 50-50 partnership's lecanemab program, is seeking FDA approval under an accelerated pathway, with a decision expected in early January. On Tuesday the Japanese drugmaker said it will use the new efficacy results to submit lecanemab for traditional FDA review as well.
The company said it will also seek authorization in Japan and Europe during its current fiscal year, ending March 31.
Eisai said 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.
"This means that treating amyloid is a step in the right direction," Petersen said.
Shares of Biogen and Eisai were halted, but shares of Eli Lilly & Co , which is also developing an Alzheimer's drug, rose as much as 6.7% in after hours trade.
The lecanemab data suggest "a potentially new multi-billion dollar franchise," Jefferies analyst Michael Yee said in a research note.
Lecanemab, like the partners' previous drug Aduhelm, is an intravenous antibody designed to remove amyloid deposits. Unlike Aduhelm, lecanemab targets forms of amyloid that have not yet clumped together.
"If you can slow a disease by almost 30% that's fantastic. This is what we have been looking for," said Dr. Jeff Cummings, director of the Chambers-Grundy Center for Transformative Neuroscience at the University of Nevada Las Vegas.
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. read more
Patient advocacy groups hailed the news of positive lecanemab trial results.
"This is important because it demonstrates that each of these drugs is different ... I would hope that the FDA approves the drug in January," USAgainstAlzheimer's Chairman George Vradenburg told Reuters.
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.
The rate of a brain swelling side effect associated with anti-amyloid treatments was 12.5% in the lecanemab group, versus 1.7% in the placebo group. But many cases did not cause symptoms, with symptomatic brain swelling seen in 2.8% of those in the lecanemab group, the companies said.
Micro hemorrhages in the brain occurred at a rate of 17% in the lecanemab group, and 8.7% in the placebo group.
Petersen said the side effect rate was 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 and other similar drugs 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.
Michael Irizarry, Eisai's deputy chief clinical officer, said on a conference call that the company will have discussions with the Medicare agency regarding coverage of lecanemab.
The number of Americans living with Alzheimer's is expected to rise to around 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.
Other plaque-targeting antibodies in late-stage development for Alzheimer's patients include Roche Holding AG's (ROG.S) gantenerumab and Eli Lilly's donanemab.