The US drug regulator on Thursday said only people with mild dementia should receive the first new Alzheimer's medicine in decades, after facing intense backlash from many in the medical community over its authorization.
Biogen's Aduhelm received an "accelerated approval" by the Food and Drug Administration in June, despite the fact that an independent expert panel advising the agency found insufficient evidence of its benefit.
"Since the agency approved Aduhelm, prescribers and other stakeholders have expressed confusion regarding the intended population for treatment," FDA spokesman Michael Felberbaum said in a statement sent to AFP.
"It was important to clarify the intent of currently approved labeling for prescribers; specifically, that it is appropriate to initiate treatment in patients with the mild cognitive impairment or mild dementia stages of Alzheimer's disease," he added.
The new label is consistent with the patient population studied in clinical trials.
While it doesn't stop physicians prescribing Aduhelm to patients in more advanced stages of the disease, it is a notable reversal.
Aduhelm, an intravenously infused monoclonal antibody, also known by its generic name aducanumab, was tested in two late-stage human trials, known as Phase 3 trials.
It convincingly showed a reduction in the build-up of a protein called beta-amyloid, which creates a plaque in the brain tissue of Alzheimer's patients.
But whether this correlated with a reduction in cognitive decline is not certain -- one study suggested it did, while the other did not.
As a result, many experts reacted with dismay at Aduhelm's approval, and at least three of the 11-member independent committee that voted unanimously against recommending the drug to the FDA subsequently resigned.
Beyond the false hope it might offer for patients and loved ones, Aduhelm's whopping price tag of $56,000 a year could cost Medicare, the federally run insurance program for elderly Americans, tens of billions of dollars a year, experts argued.
"With Alzheimer's disease affecting six million Americans, the financial and human implications of the approval are staggering," wrote Vinay Prasad, an associate professor of medicine at the University of California San Francisco, in an op-ed in Medpage Today.
The Alzheimer's Association reacted positively to Thursday's announcement.
"We appreciate the FDA's thoughtful consideration and response to the Alzheimer's Association and others in the community including physicians, researchers and patients to ensure this treatment is prescribed only to those who may see benefit," the group said.