U.S.-approved for treatment begun at the mild cognitive impairment or mild dementia stage with confirmed amyloid pathology. FDA approved subcutaneous initiation on July 13, 2026. AHEAD 3-45 is testing earlier, preclinical disease.
Clarity AD reports a 0.45-point smaller increase in the 18-point CDR-SB impairment score at 18 months: 1.21 with lecanemab versus 1.66 with placebo. That is about 27% relative slowing; both groups worsened on average.
29 Nov 2022 · peer-reviewed randomized phase 3 trial
Study results apply to their own population, dose and analysis. They do not establish a ranking between therapies.
Evidence in the atlas
0 results
Each result belongs to its own study population, dose and analysis. Open a result for its chart, comparator, safety findings and limitations.
peer-reviewed randomized phase 3 trial · 29 Nov 2022
A measurable, modest slowing of decline
Clarity AD reports a 0.45-point smaller increase in the 18-point CDR-SB impairment score at 18 months: 1.21 with lecanemab versus 1.66 with placebo. That is about 27% relative slowing; both groups worsened on average.
The randomized trial enrolled 1,795 people with amyloid-confirmed mild cognitive impairment or mild dementia. The between-group difference was −0.45 points (95% CI −0.67 to −0.23). ARIA with edema or effusions occurred in 12.6% of lecanemab recipients. These are trial averages, not an individual forecast.
ARIA with edema or effusions occurred in 12.6% of lecanemab recipients.
28 Aug 2025 · regulatory safety update: FDA calls for an additional MRI before the third IV infusion after reviewing serious and fatal ARIA-E cases early in treatment. This is a safety-monitoring update, not a new efficacy result.
Detailed trial charts have not been added for this program. See its sourced development timeline and research notes.
Biology & identity
Status in this atlas: U.S.-approved for treatment begun at the mild cognitive impairment or mild dementia stage with confirmed amyloid pathology. FDA approved subcutaneous initiation on July 13, 2026. AHEAD 3-45 is testing earlier, preclinical disease.
A recombinant humanized IgG1 monoclonal antibody directed against aggregated amyloid beta.
Uses, doses and availability depend on the formulation, indication and country. Study doses below describe research; they are not prescribing instructions.
The molecule
A recombinant humanized IgG1 monoclonal antibody directed against aggregated amyloid beta.
Structure not yet verified
Exact antibody structure not verified
A recombinant humanized IgG1 monoclonal antibody directed against aggregated amyloid beta.
Shown: Full monoclonal antibody
The official label confirms the antibody class. No exact full-drug atomic model was verified in the sources checked; a generic antibody is not substituted. The PubChem name lookup returned no CID.
21 Dec 2028 · Can earlier treatment protect cognition?
Estimated primary-completion date in NCT04468659, last updated June 4, 2026; checked September 13, 2026.
AHEAD 3-45 studies biomarker-selected people with preclinical Alzheimer's disease. Its registry estimates primary completion on December 21, 2028; that is not a promised readout, publication or approval date.
The A45 primary endpoint measures cognition at week 216; A3's primary endpoint measures amyloid PET. The checked record is active, not recruiting, with no results posted. Prevention must be assessed separately from approved early symptomatic treatment.
U.S.-approved for treatment begun at the mild cognitive impairment or mild dementia stage with confirmed amyloid pathology. FDA approved subcutaneous initiation on July 13, 2026. AHEAD 3-45 is testing earlier, preclinical disease. Slower average decline is not reversal or a cure. ARIA can involve brain swelling or bleeding and can be serious or fatal; APOE ε4 homozygotes have greater risk. Approved symptomatic treatment does not establish prevention in cognitively unimpaired people.
Clarity AD reports a 0.45-point smaller increase in the 18-point CDR-SB impairment score at 18 months: 1.21 with lecanemab versus 1.66 with placebo. That is about 27% relative slowing; both groups worsened on average.
Actual online publication; print issue January 5, 2023. · peer-reviewed randomized phase 3 trial Source
Initial approval uses an amyloid surrogate
FDA grants accelerated approval based on reduced amyloid plaques, a surrogate considered reasonably likely to predict clinical benefit. Confirming clinical benefit is a separate regulatory requirement.
Actual FDA approval date. · regulatory decision SourceSource
Clinical results support traditional approval
FDA converts Leqembi to traditional approval after reviewing Clarity AD. Treatment begins in early symptomatic, amyloid-confirmed Alzheimer's disease; this decision does not authorize prevention in people without cognitive symptoms.
Actual FDA decision and announcement. · regulatory decision Source
Postmarketing safety changes monitoring
FDA calls for an additional MRI before the third IV infusion after reviewing serious and fatal ARIA-E cases early in treatment. This is a safety-monitoring update, not a new efficacy result.
Dated FDA Drug Safety Communication. · regulatory safety update SourceSource
An autoinjector expands maintenance options
FDA approves once-weekly subcutaneous Leqembi IQLIK maintenance after 18 months of initial treatment. It changes delivery burden; it does not establish a larger cognitive benefit than IV treatment.
Original approval date in FDA Purple Book, corroborated by the same-day sponsor announcement. · formulation approval SourceSourceSource
Subcutaneous treatment can begin at home
FDA approves subcutaneous initiation, allowing home administration from the start. Effectiveness is bridged from IV outcomes using drug-exposure and amyloid findings, rather than a separate large subcutaneous clinical-outcome trial.
Dated FDA approval bulletin; the companion FDA evidence page explains the bridging basis. · formulation and regimen approval SourceSource
Can earlier treatment protect cognition?
AHEAD 3-45 studies biomarker-selected people with preclinical Alzheimer's disease. Its registry estimates primary completion on December 21, 2028; that is not a promised readout, publication or approval date.
Estimated primary-completion date in NCT04468659, last updated June 4, 2026; checked September 13, 2026. · planned prevention-trial milestone Source