• Medicare would spend $5 billion if 216,500 patients become eligible for Alzheimer's treatment Leqembi, according to research published in JAMA Internal Medicine.
• The study authors said the estimated costs to the program for seniors are conservative and spending on Leqembi might increase more than anticipated.
• Patients could face an annual bill of about $6,600 per year depending on the state they live in and whether they have supplemental insurance.
• Medicare coverage of Leqembi is severely restricted right now, though that could change in July.

The new Alzheimer's antibody treatment Leqembi could cost Medicare up to $5 billion per year, according to research published in a leading medical journal this week.

Medicare would spend about $2 billion per year if around 85,700 patients test positive for the disease and are treated with the Eisai and Biogen product Leqembi, according to the research published Thursday in JAMA Internal Medicine.

The program for seniors would spend $5 billion if around 216,500 patients become eligible for the breakthrough treatment, according to the study.

The authors said the estimated costs to Medicare are conservative and that spending on Leqembi might increase more than anticipated depending on demand and other factors.

The researchers who conducted the JAMA study included physicians and public health and policy experts. They are affiliated with the University of California Los Angeles, the Rand Corporation, Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, among other institutions.

Eisai and Biogen have priced the twice-monthly antibody infusions at $26,500 per year.

There are also additional annual costs estimated at $7,300 per patient associated with neurologist visits, MRI tests and PET scans, administration of infusions, and monitoring for and treatment of potential side effects, according to the researchers.

The study assumed Medicare would cover 80% of the costs, with patients left to pay the remaining 20% in full or in part depending on whether they have supplemental insurance.

Patients could face an annual bill of about $6,600 per year depending on the state they live in and whether they have supplemental insurance, according to the study. Some lower-income people who qualify for Medicare and Medicaid would pay nothing out of pocket.

The Alzheimer's Association, which lobbies on behalf of patients living with the disease, estimates Alzheimer's and other forms of dementia will cost the U.S. $345 billion this year. Those costs could rise to $1 trillion by 2050, according to the association.

"That's the case without treatment. Prevention and treatment is the only path toward reducing this cost over time," Robert Egge, the association's head of public policy, said in a statement.

"But it's not cost that should determine if people have access to life improving care — it's about the impact on people," Egge said. "Treatments taken in the early stages of Alzheimer's could mean a better quality of life."

Leqembi had a positive effect on patients with early Alzheimer's disease in clinical trial results published in the New England Journal of Medicine in January.

The expensive treatment is not available to the overwhelming majority of patients right now because Medicare has severely restricted coverage of the antibody.

Medicare has promised to provide broader coverage of Leqembi if the FDA grants full approval of the treatment in July. Leqembi received expedited approval from the Food and Drug Administration in January.

The Alzheimer's Association, members of Congress and state attorneys general are pushing for Medicare to drop its restrictions and fully cover Leqembi.

The antibody treatment, which targets brain plaque associated with the disease, slowed cognitive decline by 27% in Eisai's clinical trial.

There are currently no other drugs on the market that have demonstrated this level of efficacy at slowing Alzheimer's disease. Eli Lilly's donanemab demonstrated promising clinical trial results earlier this month. The company plans to apply for full FDA approval this quarter.

Leqembi and donanemab both carry serious risks of brain swelling and bleeding.