AdComm exodus: 2nd expert quits over FDA approval of Biogen's Aduhelm

Mayo Clinic neurologist David Knopman, M.D. (Mayo Clinic)

Another member of the FDA’s advisory committee on nervous system drugs has quit over the approval of Biogen’s Alzheimer’s disease product Aduhelm, Reuters reports. Mayo Clinic neurologist David Knopman, M.D., is the latest expert to leave the committee because of the FDA approval.

Since the FDA went against the Peripheral and Central Nervous System (PCNS) Drugs advisory committee to authorize Aduhelm, two of the experts who normally sit on the panel have quit. In following Washington University neurologist Joel Perlmutter, M.D., out the door, Knopman expressed his displeasure at how the FDA handled the situation.

“I was very disappointed at how the advisory committee input was treated by the FDA,” Knopman said. “I don't wish to be put in a position like this again.”

Knopman wasn’t part of the panel that debated and recommended against Aduhelm in November as he was a site investigator for ENGAGE, one of the two clinical trials Biogen used to seek FDA approval. Aduhelm failed to reduce clinical decline in ENGAGE, but Biogen tried to use the results to validate the findings of its other phase 3 by doing a post hoc analysis of high-dose patients. 

While Knopman was unable to participate in the aducanumab advisory committee, he was quoted by Michael Carome, M.D., director of Public Citizen's Health Research Group, at the meeting. The quote makes Knopman’s opinion on Biogen’s case for approval clear. 

“The evidence that aducanumab has any benefit in persons with Alzheimer's disease is terribly weak,” Knopman said.

With Knopman and Perlmutter quitting in quick succession, the FDA has lost two of the nine voting members of its PCNS committee. The departures deprive the FDA of two of the three voting members who are listed as having “neurology” as their only area of expertise. 

However, the timing of the departures may mitigate the impact, assuming there are other experts in neurology willing to replace them. Perlmutter’s four-year term was originally due to end in January 2020 but was extended by two years. The extension meant Knopman and Perlmutter were both due to leave the committee in January 2022; the FDA would have needed to replace them soon anyway.

Most of the other experts currently on the advisory committee have longer to run on their terms. The exception is chairperson and University of Virginia neurology professor Nathan Fountain, M.D., whose four-year term is up at the end of January 2022.