US regulators have approved Biogen’s aducanumab as a treatment to address an underlying cause of Alzheimer's disease.
But what is aducanumab, why is it controversial and will it be available in the UK?
Here’s what you need to know.
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What is Biogen’s aducanumab drug?
Aducanumab is an antibody which is designed to remove amyloid plaque from the brain.
Plaques form when protein pieces called beta-amyloid clump together.
Beta-amyloid comes from a larger protein found in the fatty membrane surrounding nerve cells and can gradually build up into plaques.
The National Institute on Aging explains that “in the Alzheimer’s brain, abnormal levels of this naturally occurring protein clump together to form plaques that collect between neurons and disrupt cell function.”
However, only one of two large-scale trials showed that Biogen’s aducanumab drug significantly slowed progression of Alzheimer’s.
Aducanumab was studied in patients with early disease who test positive for a component of amyloid brain plaques, but some trial patients needed to be monitored for brain swelling.
However, all previous experimental medicines employing the same approach to the disease have so far failed.
Why is the FDA’s approval of the drug contoversial?
Biogen estimates that around 1.5 million Americans would be eligible for aducanumab, which is given by monthly infusion. Aducanumab is the first new Alzheimer’s medication since 2003 and will cost tens of thousands of dollars annually per patient.
It’s not yet available in the UK, but the FDA’s approval in the US could prompt it to be approved on the NHS in the future.
However, although some patient advocates were lobbying for the drug to be approved in the US, some doctors remained unsure.
In November 2020, a panel of outside advisers to the Food and Drug Administration (FDA) voted that aducanumab had not been proven to slow Alzheimer's progression, despite a report from agency staff that said results from the successful trial were persuasive.
After the committee voted overwhelmingly against recommending approval of the drug last November, Dr. Lon Schneider, director of the California Alzheimer’s Disease Center at the University of Southern California and one of many site investigators who helped conduct one of the aducanumab trials, said: “This should not be approved, because substantial evidence of effectiveness hasn’t been shown.”
Dr Schneider added: “There’s very little potential that this will address the needs of patients.”
However, the FDA has now said that the clinical trials for the treatment, which will be sold under the brand name Aduhelm, showed a reduction in the plaques that is expected to lead to a reduction in the clinical decline of patients.
FDA said in a statement: "Although the Aduhelm data are complicated with respect to its clinical benefits, FDA has determined that there is substantial evidence that Aduhelm reduces amyloid beta plaques in the brain and that the reduction in these plaques is reasonably likely to predict important benefits to patients."