Lecanemab, which is marketed under the brand name Leqembi, is a recently approved anti-amyloid monoclonal antibody intended for the treatment of Alzheimer’s disease. This class of medication works by clearing amyloid deposits from the brain. Amyloid is a protein that accumulates in the brains of those suffering from Alzheimer’s, and is the critical component in the resulting dysfunction and damage to the brain.
Compared with prior medications in the same class, the results from the clinical trials for lecanemab show consistent and clinically demonstrable benefits in all measures captured by the study. Naturally, these are extremely important and significant findings.
Dementia is one of the most feared health conditions, and Alzheimer’s disease is the most common cause of dementia in adults, accounting for over 60% of cases. In 2019, more than 50 million people were living with Alzheimer’s worldwide, and that number is expected to triple to 150 million by the year 2050.
Lecanemab has the potential to be the first widely available disease modifying therapy that can slow the progression of Alzheimer’s, which can help millions of people suffering from mild cognitive impairment or mild Alzheimer’s dementia. And even more encouraging, lecanemab is likely to be just the first of a new class of medications, using monoclonal antibodies to target amyloids and other toxic proteins. In the years ahead, many more and better medications could potentially become available to modify the course of Alzheimer’s and neurodegenerative diseases in general.
While Alzheimer’s disease is the most common cause of dementia, it is important to remember that not all patients suffering from dementia have Alzheimer’s. While lecanemab may be helpful to those suffering from Alzheimer’s, it would not be helpful or indicated for patients who have dementia due to other causes. In addition, the patients most likely to benefit from lecanemab would be those with mild cognitive impairment or the early stages of dementia. Those with the disease in more advanced stages, or experiencing greater cognitive impairment would likely not be good candidates for the treatment.
The results of lecanemab’s phase III trial demonstrate a slowing of the progression of Alzheimer’s by about 30%. This clinical benefit is important, but still only moderate. For sake of analogy, compare a 30% reduction to a car hurtling towards a collision with an object at 80 miles per hour. This would result in a speed of 56 miles per hour. A modest improvement, but still a dangerous speed for an impact. The benefits provided by lecanemab may be a modest improvement, but still may have little impact on day to day functioning.
Also importantly, the benefits in the trial were statistically significant, but they still varied substantially from patient to patient. The individual and their circumstances must be considered to decide if lecanemab is an appropriate treatment. The potential benefits, while important, are still only moderate and must be carefully balanced against the risks and side effects and potential complications for each patient. The study included many people with conditions aside from Alzheimer’s, and encouragingly they all seemed to tolerate lecanemab well.