July 6, 2023—Today, the US Food and Drug Administration granted full approval to the drug lecanemab (brand name Leqembi®), a monoclonal antibody that has been demonstrated to lower levels of amyloid plaques in the brain and slow cognitive and functional decline in people living with Mild Cognitive Impairment and mild dementia due to Alzheimer’s disease. The approval is the first full approval of a new drug for Alzheimer’s disease in nearly 2 decades.
The full, or traditional, approval is distinguished from “accelerated” approval, which lecanemab was also granted in January of this year. The full approval communicates that the agency believes that clinical trial data demonstrated benefit of treatment, in this case slowing cognitive and functional worsening, that is substantial and sufficient to warrant clinical use of the new medication. Indeed, last month an advisory panel voted unanimously in favor of approval. Full approval is also important because Medicare indicated a willingness to cover lecanemab, now that it is fully approved.
The distinguishing factor that led to full, compared to accelerated, approval for lecanemab is the trial data, including a large Phase 3 trial and a smaller Phase 2 trial, which were consistent in demonstrating a significant slowing of disease progression in patients taking lecanemab, compared to patients taking placebo. The data also demonstrated important risks for side effects with lecanemab, including brain bleeding and brain swelling, which occurred in about 13% of participants in the Phase 3 trial. Though most of these cases did not experience any noticeable symptoms, some did; and some were quite serious. Additionally, a few patients who went on to participate in an extension study and received lecanemab treatment died. For all of these reasons, lecanemab has been given a “black box warning” to urge treating clinicians to consider these potentially serious side effects.
Lecanemab is also not a convenient treatment. It requires twice-a-month infusions and frequent MRI brain scans to ensure safety. It is appropriate only for patients with mild disease—defined as Mild Cognitive Impairment or mild dementia. It is unclear just how many people that will include, or how many of them will seek to take it.
Nevertheless, this approval and the availability of lecanemab will signal the beginning of a new era in Alzheimer’s disease treatment. This era will hopefully include many new treatments, as well as greater access to diagnostic technologies that identify the patients who are most appropriate for new treatments as early as possible. Combined with continued research into the causes and potential solutions for Alzheimer’s disease and related dementias, this could be a time in which we see real change for people living with cognitive impairment and their families.