On Friday, the pharmaceutical company Biogen announced the Food and Drug Administration accepted its application to conduct a priority review of their experimental Alzheimer’s drug for approval. The speedier-than-usual process sets the stage for the treatment, called aducanumab, to be the first new approved drug for the incurable, degenerative condition in nearly two decades. But there are many questions about whether aducanumab has enough evidence for its effectiveness.
Aducanumab is a lab-created antibody designed to target amyloid, a protein found in the brain. In those with Alzheimer’s disease, sticky clumps of amyloid called plaque form and amass in the brain. Amyloid has long been thought to play a leading role in causing the brain damage that’s characteristic of Alzheimer’s, so many scientists had theorized that drugs capable of destroying plaque could slow or prevent further destruction of the brain.
In March 2019, however, Biogen and its Japanese partner Eisai both suspended their Phase III clinical trials of aducanumab, after an independent review found that the drug was unlikely to meet the trials’ primary goal of slowing down cognitive impairment in people believed to have mild Alzheimer’s.
At the time, aducanumab was seen as the latest failure for the once-promising line of anti-plaque drugs that had reached clinical trials. This lack of success has started to convince scientists to look elsewhere for potential treatments, such as drugs that interact with tau, another protein in the brain that forms into clumps called tangles in Alzheimer’s patients.
In October 2019, though, Biogen made a surprising announcement. They had looked at their trial data (including results collected after the analysis that prompted the trial shutdown was completed) and concluded there actually was data from the first trial showing that the drug would have met the goal of noticeably slowing down cognitive decline in volunteers, compared to a placebo. The company also said it had hopeful data from a subset of patients in the second trial given a high dose of the drug, though the trial overall still didn’t show a clinically significant result. With that, the company announced that it planned to submit the drug for review by the FDA.
This new development means that the FDA will conduct a priority review of the drug for approval. The agency will have to make a decision by March 7, 2021, though it may come down sooner than that. If the drug was approved, it would be the first new approved drug for Alzheimer’s to emerge in about 17 years, and likely the first intended to slow down or prevent the worsening of the condition. The five currently approved treatments for Alzheimer’s only treat its symptoms.
Outside scientists and experts, however, have been skeptical about the evidence for aducanumab, even after the company made some of its newer data available last December. And some have wondered out loud whether the company is simply spinning the data favorably to salvage a failed drug.
The next step of the process may provide some clarity to those questions. Before the FDA weighs in on an approval, it convenes a panel of independent experts in related fields to look over the evidence themselves and make a recommendation. Though the recommendations are not binding, the FDA rarely disagrees with them. Time will soon tell whether aducanumab will pass muster there.