The FDA approved Biogen's aducanumab without strong evidence of clinical benefits so it could give Alzheimer's patients earlier access to the potentially valuable treatment, three directors at the agency wrote in an opinion piece published June 23 in The Washington Post.
On June 7, the FDA approved aducanumab, sold under the brand name Aduhelm, marking the first approval the agency has granted to an Alzheimer's treatment since 2003. Aduhelm is the first treatment approved by the FDA intended to slow cognitive decline from Alzheimer's disease, as the Alzheimer's drugs the FDA previously cleared are aimed at alleviating symptoms rather than slowing the disease's progression.
The drug's approval sparked an intense debate in the pharmaceutical and medical communities, with critics saying there was not enough evidence of clinical benefits to warrant an approval. From June 9-11, three members of the FDA's advisory committee resigned over the approval.
The FDA released documents June 22 revealing its statisticians and advisors repeatedly objected to Aduhelm's approval. Their objections mirror criticisms the FDA's peripheral and central nervous system drugs advisory committee expressed in November when it voted against the drugs approval: there is not enough evidence to prove the drug's efficacy.
The June 23 opinion piece — which was written by Patrizia Cavazzoni, MD, director of drug evaluation; Peter Stein, MD, director of the office of the new drugs; and Billy Dunn, MD, the director of the office of neuroscience — acknowledges that Aduhelm's trial data did not qualify for standard FDA approval. Instead, the drug was approved using the FDA's accelerated approval process.
"A drug may be approved under this pathway when it is shown to improve a measure of a disease and when it is 'reasonably likely' that this measure predicts clinical benefit," the FDA directors wrote. "Note that the law says 'reasonably likely' to predict, not 'certain' to predict. In other words, accelerated approval was designed for situations in which there is residual uncertainty about clinical benefit."
The directors also wrote that while the data failed to confirm clinical benefit, it did "convincingly and consistently" prove that Aduhelm reduces amyloid plaque in the brains of Alzheimer's patients. They said they reviewed the trial data and publicly available information extensively to conclude that the drug's ability to reduce amyloid plaque is "reasonably likely" to predict clinical benefit.
The directors wrote that the FDA will require the company marketing Aduhelm to conduct a new study to verify and describe the drug’s benefit. If the study is not conducted in a timely manner or fails to prove clinical benefit, the FDA can withdraw the approval.