and may be a more realistic goal for clinical AD drug trials, a new report suggests.
The report is a yearlong undertaking by an expert work group convened by the Alzheimer’s Association and was prompted, in part, by the fallout from the U.S. Food and Drug Administration’s controversial decision to grant aducanumab (Aduhelm) accelerated approval, which came over the objection of an advisory panel that found the drug was ineffective.
The report’s authors call for a “reframing” of how researchers define “clinically meaningful” in randomized controlled trials (RCTs), noting that it’s time to adjust expectations of outcomes from relatively short clinical trials.
“Without lowering the bar, are we expecting too much from a clinical trial by expecting that unless the disease is halted in its tracks and there’s no progression, we failed at treatment?” the report’s lead author and group leader Ronald C. Petersen, MD, PhD, lead author, chair of the work group, and professor of neurology at the Mayo Clinic, Rochester, Minn., told this news organization.
Interpretations of clinical meaningfulness are used in the drug approval process and in decisions about whether an insurer will cover the cost of treatment, the authors note.
While the report doesn’t provide a consensus definition of clinically meaningful benefit, it does offer a starting point for a conversation about how the phrase should be defined in the context of RCTs for disease-modifying therapies (DMTs) in AD, Dr. Petersen said.
“What we tried to do was to put it into some kind of perspective and at least have people reflect on this: If you’re going to design the perfect drug trial in Alzheimer’s disease, what would it be? We wanted to get people to think about it without digging in their heels for or against,” he added.
The report was published online in Alzheimer’s and Dementia: The Journal of the Alzheimer’s Association.
A proactive measure
The expert group began its work in January 2022, less than a year after the FDA approved aducanumab. Since the panel began its work, the FDA has approved a second AD drug, lecanemab (Leqembi), and denied accelerated approval of a third medication, donanemab.
“At the time we started this group, we had one approved treatment, and we just knew that there were others on the way, and we needed to be prepared to have this conversation and be more proactive than reactive,” Christopher Weber, PhD, director of global science initiatives for the Alzheimer’s Association and co-author of the report, said in an interview.
The work group suggests that simply slowing disease progression might be a desired goal for drug trials, especially early on, before cognition and memory are affected.
They also note that a benefit identified during an 18-month clinical trial may ultimately lead to even more meaningful changes over coming years, well beyond the trial’s end.
In addition, the report authors call for the development of better research tools to more accurately assess meaningful change. The Clinical Dementia Rating (CDR) scale is currently the key instrument used as a primary outcome measure in RCTs. However, the report’s authors note that it may not be adequate to measure meaningful change in early-stage disease.
“Developing better tools certainly should be on the radar screen for all of us, because I think we can do better,” Dr. Petersen said. “The CDR, as good as it is and as long as it’s been used in the field, is a pretty blunt instrument, and it’s the result of subjective ratings.”