The first drug shown to slow down Alzheimer's disease is likely to receive full approval from the Food and Drug Administration by July 6.

In theory, the move would make lecanemab (Leqembi) available to more than a million Medicare patients in the early stages of Alzheimer's. In practice, though, the number is likely to be much smaller.

"I'd be surprised if right away we saw demand from that many people," says Dr. David Rind, chief medical officer of the Institute for Clinical and Economic Review. The number could be in the hundreds of thousands, though, he says.

Lecanemab's rollout could be slowed by factors ranging from the extra paperwork required of doctors to a shortage of medical personnel trained to diagnose and treat patients, experts say.

The FDA granted lecanemab a conditional approval in January, based on the drug's success removing a substance called amyloid-beta from the brains of people in the early stages of Alzheimer's. Full approval usually requires evidence that a drug also helps patients.

And until the FDA grants full approval, lecanemab isn't covered for most Medicare patients, who represent the vast majority of people with Alzheimer's.

That makes the impending FDA action a big deal for patients, even though the drug is far from a cure.

"Just the idea that they could gain more time is profoundly important and exciting," says Robert Egge, chief public policy officer of the Alzheimer's Association. "That's why patients [and] their families have been speaking up so loudly for the need for Medicare coverage."

Full FDA approval is all but assured. On June 9, an advisory committee voted unanimously that lecanemab had demonstrated the ability to slow down Alzheimer's, and FDA staff have given the drug a favorable evaluation.

With full approval, Medicare plans to cover lecanemab treatment in "appropriate settings," according to a statement from The Centers for Medicare And Medicaid Services.

Obstacles after approval

But finding treatment may remain a challenge for many Medicare patients.

One reason is that Medicare will require doctors to participate in a registry designed to track the drug's safety and effectiveness.

The extra paperwork may keep some doctors from prescribing the drug, Egge says.

"We're most likely to see that happen in areas that are already traditionally underserved, where doctors are already stretched thin," he says. "Our biggest concern is that there will be whole communities that will be left out entirely."

Another concern is that payers may not fully cover the brain scans and related services that go with lecanemab treatment. And insurers may require doctors and medical facilities to meet certain criteria in order to provide treatment.

"If that requirement becomes very restrictive, then only specialized centers will really be able to do this," says Dr. Zaldy Tan, Medical Director of the Jona Goldrich Center for Alzheimer's and Memory Disorders at Cedars Sinai Health System in Los Angeles.

Even patients who could get the drug may choose not to, Tan says, noting that it takes 18 months of treatment to slow the loss of memory and thinking by about six months.

"'So what does that six months mean to them?' is my question," Tan says, "and whether that is worth showing up for an infusion every two weeks and risking brain bleeding and swelling."

Even so, Tan supports the FDA's expected approval of lecanemab. "It is a positive thing," he says. Even if the drug isn't a perfect solution, "we need to start somewhere."

That view is shared by Dr. Mia Yang, a geriatrician in Winston-Salem and an assistant professor at Wake Forest University School of Medicine.

Lecanemab represents a big improvement over its predecessor, aducanumab, Yang says.

Aducanumab got a conditional approval from the FDA in 2021 despite a lack of evidence that it changed the course of the disease. Insurers generally decided not to cover the drug, and it only reached a few patients.

"Aducanumab kind of gave the whole class of [amyloid] medicines a bad rap," Yang says.

Lecanemab appears to work, even though the benefit is modest, Yang says. But she worries that the U.S. doesn't have enough memory specialists or infusion clinics to handle all the potential patients.

"I think we're all flying the plane while we're building it in terms of the health care infrastructure," she says.

It will take a huge effort just to identify the right patients, Yang says. People with advanced Alzheimer's, for example, are not eligible. And people taking blood thinners may face a higher risk of bleeding in the brain.

"So of the millions of Americans who have Alzheimer's disease," she says, "I definitely don't think that this is a drug that's applicable for the majority of them."

A costly treatment

Lecanemab's price may pose another barrier, even with insurance coverage.

The drug's maker, Eisai, expects the medicine alone to cost $26,500 a year. Diagnostic and follow-up tests will add to that. And a patient's share could run into the thousands of dollars.

An analysis of lecanemab's efficacy and value to patients found that the price is too high, Rind says. "A fair price for this would range from about $8,900 up to $21,500 per year, which is a very wide price range," he says.

Rind favors something toward the lower end of that range.

But at its current price, he says, lecanemab could be very profitable for Eisai and its U.S. partner, Biogen.

"I would guess, though, that there are going to be a lot of people with early Alzheimer's who are going to be asking for this drug," he says. "So it could be a multi-billion-dollar drug."