Experts have welcomed full data showing an experimental drug can slow cognitive decline in Alzheimer’s patients, but warned improvements were comparatively small and said it remained unclear how much difference it might make in people’s lives.
Japanese drugmaker Eisai and its United States partner Biogen had announced in September that preliminary data from a trial of lecanemab found it slowed cognitive decline by 27 percent across an 18-month period.
The companies on Tuesday provided the full results of the study on nearly 1,800 people in the earliest stages of the disease, the most common cause of dementia among older adults.
Every two weeks for 18 months, study participants received intravenous lecanemab or a placebo. Researchers tracked them using an 18-point scale that measures cognitive and functional ability.
Those given lecanemab declined more slowly – a difference of not quite half a point on that scale, concluded the research team led by Christopher van Dyck at Yale University.
That is a hard-to-understand change, but measured a different way, lecanemab delayed patients’ worsening by about five months over the course of the study, Eisai’s Dr Michael Irizarry told The Associated Press (AP) news agency. Also, lecanemab recipients were 31 percent less likely to advance to the next stage of the disease during the study.
“That translates to more time in earlier stages” when people function better, Irizarry said.
But doctors are divided over how much difference those changes may make for patients and families.
“It is unlikely that the small difference reported in this trial will be noticeable by individual patients,” said Madhav Thambisetty, of the National Institute on Aging, who told AP he was not speaking for the government agency.
He said many researchers believe a meaningful improvement would require at least a difference of a full point on that 18-point scale.
But Ron Petersen, an Alzheimer’s expert at the Mayo Clinic, said the drug’s effect was “a modest one but I think it’s clinically meaningful” – because even a few months’ delay in progression could give someone a little more time when they are functioning independently.
The trial is important because it shows a drug that attacks a sticky protein called amyloid – considered one of several culprits behind Alzheimer’s – can delay disease progression, said Maria Carrillo, the chief science officer for the Alzheimer’s Association.
“We all understand that this is not a cure and we’re all trying to really grasp what it means to slow Alzheimer’s, because this is a first,” Carrillo said.
But any delay in cognitive decline early on could be meaningful for “how much time we have with our loved ones in a stage of disease where we can still enjoy family and outings, vacations, bucket lists,” she said.
Amyloid-targeting drugs can cause side effects that include swelling and bleeding in the brain – and lecanemab did as well. One type of this swelling was seen in about 13 percent of recipients. Eisai said most were mild or asymptomatic.
Also, two deaths have been publicly reported among lecanemab users who also were taking blood-thinning medications for other health problems. Eisai said on Tuesday the deaths cannot be attributed to the Alzheimer’s drug.
But Mayo’s Petersen said if lecanemab is approved for use in the United States, he would avoid prescribing it to people on blood thinners, at least initially.
And Thambisetty said the death reports raise concern about how the drug may be tolerated outside of research studies “where patients are likely to be sicker and have multiple other medical conditions.
Speaking to Al Jazeera on Wednesday, Bart de Strooper, the director of the UK Dementia Research Institute, said the risk of side effects “has to be evaluated from patient to patient”.
“Most of the side effects are hardly noticed by the patient, so it’s a few rare cases where this can be life-threatening … this needs to be further investigated,” de Strooper said.
“I wouldn’t expect a drug without side effects; I don’t think that really exists. So it’s a balance about risk and how much you want to avoid Alzheimer’s disease.”
The Food and Drug Administration (FDA) is considering approving lecanemab under its fast-track programme, with a decision expected in early January. If approved, it would be the second anti-amyloid drug on the market.
Nearly all treatments available for people with Alzheimer’s only temporarily ease symptoms. Scientists do not yet know exactly how Alzheimer’s forms but one theory is that gunky amyloid buildup plays a key role, although drug after drug that targets it has failed.
In a contentious move last year, the FDA approved the first amyloid-targeting drug, Biogen’s Aduhelm, despite a lack of evidence of better patient outcomes. Insurers and many doctors have hesitated to prescribe the pricey drug – another reason experts have anxiously awaited word of how well the newer lecanemab may work.