Two drugs sit at the center of the current prevention push. Lecanemab, sold under the brand name Leqembi, received full FDA approval in July 2023 as the first therapy proven to slow cognitive decline by clearing amyloid from the brain. The drug is made by the pharmaceutical companies Eisai and Biogen, and its Phase 3 data came from the Clarity AD trial, published in The New England Journal of Medicine. In patients with early Alzheimer’s, lecanemab reduced brain amyloid levels and slowed cognitive decline by 27% over an 18-month period. The AHEAD 3–45 trial is now taking that same drug into a preclinical population – people with no symptoms at all.

The second drug, donanemab (brand name Kisunla), came next. Manufactured by Eli Lilly, it targets amyloid beta administered intravenously and received FDA approval in July 2024. Its Phase 3 clinical trial data, published in JAMA, was striking. Cognitive and functional decline slowed on all outcome measures: 35% on the iADRS scale, 37% on the CDR-SB, 32% on the ADAS-Cog13, and 40% on ADCS-iADL measures – all statistically significant results. Looking at the data another way, 47% of people on donanemab stayed stable on the CDR-SB over one year, compared with 29% on placebo.

Both approvals share an important boundary. Both lecanemab and donanemab are currently approved for early symptomatic Alzheimer’s disease – specifically, patients with mild cognitive impairment or mild dementia with confirmed amyloid pathology. The prevention trials now underway aim to move that window back considerably, to people who haven’t yet developed any symptoms at all.