The drug is called lecanemab and it’s a monoclonal antibody treatment given by IV infusion. It targets and removes amyloid plaques in the brain. Amyloid is a protein that clumps together and forms plaques. Scientists call it the amyloid hypothesis and the theory is that these plaques lead to Alzheimer’s disease. However, this is the 16th drug that’s been developed to clear these plaques and all the others failed. So naturally, there are questions – and the main one is “What’s different this time”?
For a start, the drug was tested in patients with early-stage Alzheimer's disease vs late-stage. The trial was large with roughly 1800 participants – so it provides a good sample size. Researchers used new types of scans that showed beta-amyloid in participants’ brains. Previously, these plaques could only be seen during autopsies. As for the drug itself, it was designed to bind to amyloids at different places and importantly, before they clumped together to form plaques. So, targeting beta-amyloid sooner rather than later could be making an impact as well.
Participants' progress was tracked over 18 months. Results showed cognitive decline overall was slowed by 27% in those who were given the experimental drug lecanemab. The main measure used to evaluate the participants was a survey. And, it was answered by participants’ primary caregivers. So yes, there is concern regarding bias because it’s not uncommon that caregivers would want to see their loved ones improving.
While it was a randomized, placebo-controlled double-blind study, meaning no one would know who was getting the drug or a dummy pill, some people did figure that out because of side effects. If a participant had any prominent side effects, they would have had extra brain scans. So what were these? Well, some participants reacted with shaking, chills, and a low-grade fever. Roughly 1 in 5 participants taking lecanemab experienced brain swelling called ARIA – which stands for amyloid-related imaging abnormalities. For the most part, many people who develop ARIA don’t have symptoms but some can end up hospitalized.
The bottom line, in my opinion, is that this new experimental Alzheimer’s drug looks promising. It could potentially give newly diagnosed Alzheimer’s patients extra time to live a fuller life. But, we won’t know until early January 2023 if lecanemab is a go or not, as that’s when the FDA is expected to make a decision.