1 January 2022 | New Scientist | 11

Preview of 2022

Controversy over the first drug designed to

treat the cause of Alzheimer’s will continue,

reports Clare Wilson

E

XPECT to see debate over a new

medicine to treat Alzheimer’s

disease, called aducanumab,

continue into 2022. Approved in

the US last June, it is the first drug

designed to treat a possible cause

of this form of dementia, rather

than the symptoms.

Aducanumab targets beta-amyloid,

a protein that makes up plaques in

the brain often seen in people with

Alzheimer’s disease. But the drug has

its critics as well as its cheerleaders.

It hasn’t so far been proven to reduce

memory loss and confusion, the chief

symptoms of Alzheimer’s disease.

Other commonly used medicines

slightly alleviate these symptoms,

but they don’t work for everyone

and their effects wear off.

The US drug regulatory body, the

Food and Drug Administration (FDA),

approved aducanumab for use to

combat early Alzheimer’s on the basis

that it reduces the extent of amyloid

plaques. These have long been seen

as a “biomarker” of Alzheimer’s – in

other words, a biological indicator

of disease progression or severity.

Other medicines have been

approved on the basis of biomarkers –

for instance, levels of “bad

cholesterol” are seen as a biomarker

for heart disease. But for Alzheimer’s,

it is still being debated if plaques are

a valid biomarker.

There is growing concern that they

may not be a cause but something

more like a side effect of the disease

process. Targeting the plaques is

“reasonably likely to have a clinical

effect”, says Susan Kohlhaas at

Alzheimer’s Research UK. “But

that’s still to be tested.”

When the FDA approved

aducanumab, it went against the

recommendations of its scientific

advisory panel, which it usually

follows – none of the 11 members

considered it ready for approval and

three members resigned in protest.

The agency’s acting commissioner

has since asked for an investigation to

take place into the approval process.

The drug’s maker, Biogen, told

New Scientist: “The approval of

aducanumab by the FDA came after

an extensive development, clinical

testing and regulatory review process,

supported by data of more than

3000 patients who participated

in our trials.”

One clinical trial showed that

about 40 per cent of people on the

drug experienced brain swelling

or bleeding visible on a scan.

The FDA has said aducanumab

should now be tested in a larger

clinical trial, but in practice these

can take many years to produce

results. Few people may want to be

in a placebo-controlled trial and risk

taking dummy pills after the drug

has been approved.

On 17 December, the European

Medicines Agency decided not

to approve aducanumab. It is

also under review by the UK’s

Medicines and Healthcare products

Regulatory Agency.

If the drug is approved in the UK,

it would need to be assessed to decide

whether it is cost-effective for use by

the national health services. In the US,

it is priced at $56,000 a year.

“We have to make sure that we

leave no stone unturned in our

search for life-changing treatments,”

says Kohlhaas. “It’s important to

respect the regulatory process that

happens in the UK and elsewhere.

We also need to make sure that our

treatments are evaluated for safety

and effectiveness.” ❚

A participant

in a clinical trial

for aducanumab

Medicine

Alzheimer’s

drug debate

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“ We have to leave

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