Drug curbs Alzheimer’s, but can it make a real difference?

An experimental Alzheimer’s drug modestly slowed the inevitable worsening of the brain disease, but the eagerly awaited new data makes it unclear how much of a difference it could make in people’s lives.

Japanese drugmaker Eisai and its US partner Biogen had announced to early this fall that the drug lecanemab seemed to work, a much-needed bright spot after repeated disappointments in the search for better treatments for the incurable disease.

On Tuesday night, the companies provided the full results of the study of nearly 1,800 people in the early stages of mental illness. The data was presented at an Alzheimer’s meeting in San Francisco and published in The New England Journal of Medicine.

Lecanemab delayed patients’ worsening by about five months over the course of the 18-month study, Eisai’s Dr. Michael Irizarry told The Associated Press. In addition, lecanemab recipients were 31% less likely to progress to the next stage of the disease during the study.

“That translates to more time in the early stages” when people function best, Irizarry said.

Every two weeks, study participants received intravenous lecanemab or a dummy infusion. The researchers tracked them using an 18-point scale that measures cognitive and functional ability.

The study’s key finding: Those who received lecanemab declined more slowly, a difference of no more than half a point on that scale over 18 months, the research team led by Dr. Christopher van Dyck of Yale University concluded.

Doctors are divided on the difference that can make for patients and their families, especially since the drug carries some concerning potential safety risks, including inflammation of the brain.

“Individual patients are unlikely to notice the small difference reported in this trial,” said Dr. Madhav Thambisetty of the National Institute on Aging, noting that he was not speaking on behalf of the government agency.

He said many researchers believe significant improvement would require at least a full point difference on that 18-point scale.

But Dr. Ron Petersen, a Mayo Clinic Alzheimer’s expert, said the drug’s effect was “modest, but I think it’s clinically significant,” because even a few months’ delay in progression could give someone a little more time when you are functioning independently.

The trial is important because it shows that a drug that attacks a sticky protein called amyloid, considered one of several culprits of Alzheimer’s, can slow the progression of the disease, said María Carrillo, scientific director of the Alzheimer’s Association.

“We all understand that this is not a cure and we are all trying to really understand what it means to delay Alzheimer’s, because this is the first time,” Carrillo said.

But any delay in early cognitive decline could be significant for “how much time we have with loved ones at a stage of the disease where we can still enjoy family and going out, vacations, bucket lists,” he said.

Drugs that target amyloid can cause side effects including swelling and bleeding in the brain, and lecanemab did too. One type of this swelling was seen in about 13% of recipients. Eisai said most were mild or asymptomatic.

In addition, two deaths among lecanemab users who were also taking blood-thinning medications for other health problems were publicly reported. Eisai said Tuesday that the deaths cannot be attributed to the Alzheimer’s drug.

But Mayo’s Petersen said that if lecanemab is approved for use in the US, he would avoid prescribing it to people taking blood thinners, at least initially.

And Thambisetty said the reports of death raise concerns about how the drug may be tolerated outside of research studies “where patients are likely to be sicker and have many other medical conditions.”

The Food and Drug Administration is considering approving lecanemab under its fast track program, with a decision expected in early January. If approved, it would be the second anti-amyloid drug on the market.

Almost all of the treatments available to the 6 million Americans with Alzheimer’s, and millions more worldwide with the most common form of dementia, only temporarily relieve symptoms. Scientists still don’t know exactly how Alzheimer’s disease forms, but one theory is that sticky amyloid buildup plays a key role, even though one drug after another that targets it has failed.

In a controversial move last year, the FDA approved the first drug targeting amyloid , Biogen’s Aduhelm, despite a lack of evidence for better patient outcomes. Insurers and many doctors have hesitant to prescribe the expensive drug another reason why experts have eagerly awaited news about how well the new lecanemab might work.

If the FDA approves lecanemab, patients and their families will need a voice in deciding whether it is worth the hassle of IV infusions and the risk of side effects for the possibility of at least some delay in progression, Petersen said.

“I don’t think we’re going to stop the disease in its tracks” with just drugs that target amyloid, he added, saying a combination of drugs that target additional Alzheimer’s culprits will be needed.

Researchers are preparing to test lecanemab with other experimental drugs and how it works in high-risk people before they show the first signs of memory problems.