• The FDA's decision comes after clinical trial results indicated that lecanemab slows cognitive decline somewhat in people with mild impairment from Alzheimer's.
• But Biogen and Eisai's monoclonal antibody treatment also carries risks of brain swelling and bleeding.
• Eisai, which led the development of lecanemab, is pricing the treatment at $26,500 per year in the U.S

The Food and Drug Administration on Friday granted accelerated approval for the Alzheimer's drug lecanemab, the second treatment from Biogen and its Japanese partner Eisai to receive an early green light in less than two years.

The FDA's approval comes after clinical trial results published in November indicated that lecanemab slows cognitive decline somewhat in people with mild impairment due to Alzheimer's disease, but the treatment also carries risks of brain swelling and bleeding.

Eisai, which led the development of lecanemab, is pricing the treatment at $26,500 per year in the U.S. It will be sold under the name Leqembi.

The FDA can accelerate approval of a drug to quickly bring it to market if it's expected to help patients suffering from serious conditions more than what is currently available. Biogen and Eisai applied for accelerated approval in July.

"Alzheimer's disease immeasurably incapacitates the lives of those who suffer from it and has devastating effects on their loved ones," said Dr. Billy Dunn, director of the FDA's neuroscience division, in a statement. "This treatment option is the latest therapy to target and affect the underlying disease process of Alzheimer's, instead of only treating the symptoms of the disease."

More than 6.5 million people in the U.S. suffer from Alzheimer's. The irreversible disease destroys memory, thinking skills, and eventually the ability to carry out simple tasks.

The decision on lecanameb comes after Congress issued a scathing report last week about how the FDA handled the controversial approval of another Alzheimer's drug developed by Biogen and Eisai, called Aduhelm. The 2021 approval of that treatment, which experts said did not show a clear clinical benefit, was "rife with irregularities," according to the report.

The congressional report said the "FDA must take swift action to ensure that its processes for reviewing future Alzheimer's disease treatments do not lead to the same doubts about the integrity of FDA's review."

Modestly slows disease

Lecanemab is a monoclonal antibody that targets a protein called amyloid which builds up on the brain in people with Alzheimer's. The antibody is administered intravenously every two weeks in doses determined by a patient's body weight with 10 milligrams given per kilogram.

The FDA approved lecanemab based on the reduction of amyloid plaque observed in clinical trial participants who received the treatment, according to a statement from the agency. Participants who did not receive the treatment, the placebo arm, had no reduction in amyloid plaque.

The clinical trial results, published in the New England Journal of Medicine, found that cognitive decline was 27% slower over 18 months in people who received lecanemab compared with those who did not receive the treatment. The study was funded by Biogen and Eisai.

Cognitive decline was measured using a system called the clinical dementia rating, which is an 18-point scale with a higher score indicating a greater level of impairment. It measures cognitive functions such as memory, judgement and problem solving.

Alzheimer's disease progressed 1.21 points on average in the group that received lecanemab compared with 1.66 points in the group that did not receive the treatment, a modest difference of 0.45 points.

Nearly 1,800 people ages 50 to 90 years old with early Alzheimer's participated in the trial, about half of whom received lecanemab and half of whom did not.

Safety concerns

Though lecanemab may slow cognitive decline somewhat, the treatment also carries risks.

Nearly 13% of those who received lecanemab developed brain swelling compared with about 2% in the group that didn't receive the treatment. However, most of these cases were mild to moderate in severity, did not cause symptoms, and typically resolved within four months.

About 3% of patients who received lecanemab had more serious brain swelling with symptoms that included headache, visual disturbance and confusion.

About 17% of those who received lecanemab had brain bleeding, compared with 9% in the group that did not take the treatment. The most common symptoms associated with the bleeding was dizziness.

Overall, 14% of people who received lecanemab suffered serious adverse events in the clinical trial, compared with 11% of those who did not receive the treatment.

The authors of the study said longer clinical trials were needed to determine the efficacy and safety of lecanemab in patients with early Alzheimer's disease.

The FDA said the prescribing information for lecanemab will include a warning about a risk of swelling and bleeding, broadly referred to as amyloid-related imaging abnormalities.

The death of a clinical trial participant in the Chicago area could also possibly be linked to lecanemab, according to a research letter published in the New England Journal of Medicine this week.

The 65-year-old suffered a stroke and was hospitalized four days after their third lecanemab infusion. A CT scan performed after the patient's stroke found extensive bleeding in the brain. An MRI performed 81 days before the stroke had not found any bleeding.

The patient had also received a medication, called t-PA, used to break apart blood clots that cause strokes. But extensive brain bleeding would be an unusual complication of this medication alone, according to the physicians who penned the research letter.

Researchers involved in the lecanemab clinical trial, in a response letter, argued that the blood clot medication appeared to be the immediate cause of the patient's death, with the first symptoms occurring 8 minutes after they received an infusion of the blood-clot buster.