The Food and Drug Administration has fully approved the first drug shown to slow down Alzheimer's disease.

The action means that Leqembi, whose generic name is lecanemab, should be widely covered by the federal Medicare health insurance program, which primarily serves adults age 65 and older. So more people who are in the early stages of the disease will have access to the drug – and be able to afford it.

"It's not something that's going to stop the disease or reverse it," says Dr . Sanjeev Vaishnavi, director of clinical research at the Penn Memory Center. "But it may slow down progression of the disease and may give people more meaningful time with their families."

In studies reviewed by the FDA, Leqembi appeared to slow declines in memory and thinking by about 27% after 18 months of treatment. It also dramatically reduced the sticky beta-amyloid plaques that tend to build up in the brains of people with Alzheimer's.

"It's very exciting that we're targeting the actual pathology of the disease," Vaishnavi says.

Just to be talking about a treatment "is an incredible point for the Alzheimer's cause overall," says Joanne Pike, president and CEO of the Alzheimer's Association.

Leqembi comes from the Japanese pharmaceutical company Eisai and its U.S. partner Biogen. The companies have said Leqembi will cost about $26,500 a year.

In January, the drug received what's known as accelerated approval from the FDA, based on its ability to remove the substance beta-amyloid from the brains of people in the early stages of Alzheimer's. Full or traditional approval reflects the FDA's assessment that Leqembi also helps preserve memory and thinking.

Also in January, the Centers for Medicare and Medicaid Services announced it would broaden coverage of Leqembi on the same day the drug received full FDA approval. That should mean the drug will now be covered for most Medicare patients with early signs of cognitive problems and elevated levels of amyloid.

Wider coverage, limited use

Until now, Medicare has paid for Leqembi only for patients in certain clinical trials.

Under the expanded coverage, a million or more Medicare patients are potential candidates for the drug. But it's likely that a much smaller number will actually get it in the next year or so.

One reason is the drug's potentially life-threatening side effects, Vaishnavi says.

"I think [patients] are a little wary because they hear about bleeding or swelling in the brain," Vaishnavi says. "They are concerned, and I think rightfully so."

Another limiting factor is that the U.S. healthcare system simply isn't prepared to diagnose, treat, and monitor a large number of Alzheimer's patients, Pike says.

Leqembi requires an initial test to determine amyloid levels in the brain, intravenous infusions every other week, and periodic brain scans to detect side effects.

"We don't have enough specialists who understand how to provide this treatment," Pike says. "We don't have enough primary care physicians with knowledge and the confidence to provide a referral."

But Leqembi does have much more support from doctors and payers than an ill-fated predecessor.

In 2021, the FDA granted conditional approval to a drug called Aduhelm. It also removes amyloid from the brain.

But it was unclear whether Aduhelm, also known as aducanumab, slowed down the loss of memory and thinking. So many doctors refused to prescribe it. And Medicare declined to cover the costly drug, except for patients in certain clinical trials.

Leqembi shouldn't have those problems.

'You really don't have anything to lose'

"It seems that the scientific and clinician community understands the difference in this moment with Leqembi versus Aduhelm," Pike says.

Much of what scientists have learned about Leqembi is thanks to people like Ken and Susan Bell in St. Charles, Missouri.

Susan, who is 70, began showing signs of Alzheimer's about four years ago. So she enrolled in a clinical trial of Leqembi at Washington University in St. Louis and has been receiving the drug ever since.

The drug hasn't stopped the disease, though.

"There has been, certainly, some degradation in her cognitive powers and so forth," Ken says.

But Susan's decline has been relatively slow. The couple are still able to travel and play golf, which could signal that the drug is working.

"We don't have enough experience, like the medical folks do, to know what would have happened" without the drug, Ken says.

Still, Susan thinks other people in the early stages of Alzheimer's should try Leqembi.

"I would tell them, 'Go for it,'" she says, "because you really don't have anything to lose."