Brain bleeds and age affect risk
In an interview with MDedge Neurology, neurologist Madhav Thambisetty, MD, PhD, a senior investigator with the National Institute on Aging in Baltimore, and a member of the FDA advisory committee that recommended against approval for aducanumab, said that while physicians are aware that APOE4 carriers face higher risks of treatment-related complications, the new safety findings offer additional guidance on patient selection.
Dr. Madhav Thambisetty
“The older you are the greater your risk of ARIA, and the more micro-hemorrhages you have at baseline the greater your risk. Those are important findings that were not previously well publicized before,” Dr. Thambisetty said.
In the EMERGE and ENGAGE trials, Dr. Thambisetty pointed out, patients with four or more micro-hemorrhages at baseline were excluded. The new findings reveal that even a small number of bleeds at baseline can contribute to ARIA risk.
“Patients in real-world clinical practice are going to be very different from the tightly controlled, well-screened participants who were enrolled in these trials. Microbleeds are very common in Alzheimer’s patients, occurring in 18-32%. Now that these findings are available, it’s important for a practicing physician to obtain a baseline MRI scan and really pay attention to microbleeds, because that will affect treatment decisions.”
Additional concerns
Dr. Thambisetty cautioned that the new results made no mention of another important safety outcome: loss of brain volume associated with treatment.
Changes in brain volume have been seen associated with other amyloid-lowering treatments, though the reasons for this are poorly understood. Participants in EMERGE and ENGAGE “received numerous MRI scans,” Dr. Thambisetty said. “This was one of the strengths of the trials. Thanks to an open-label extension we now have more than 2 years of MRI data from meticulously monitored patients, and there has been no mention of brain volume changes despite this being a prespecified outcome. This, for me, is one of the glaring omissions of this paper, and the fact that it’s not even mentioned is really worrisome.”
The sponsor of the aducanumab trials, Biogen, has yet to publish efficacy findings in a peer-reviewed journal, instead presenting them piecemeal at conferences.
“The current paper was a secondary analysis,” Dr. Thambisetty said. “The authors say the primary analysis will be published elsewhere. I think it’s important to reflect upon the fact that these clinical trials enrolled more than 3,000 participants at more than 300 trial centers in 20 countries. We now have an approved drug that’s commercially available. And yet we don’t have a single peer-reviewed publication discussing the efficacy data. None of this is in the interest of our patients, or in advancing the science.”
The EMERGE and ENGAGE trials were funded by Biogen. Eight of the current paper’s 14 authors are Biogen employees. Dr. Salloway, the lead author, disclosed financial support from Biogen and other manufacturers, as did two of his coauthors. Dr. Thambisetty disclosed no financial conflicts of interest.