Eisai Co. and Biogen Inc. (NASDAQ: BIIB) released results from the real-world Lecanemab in Early Alzheimer's Disease (LEADER) Study showing that 82.5% of early Alzheimer's disease patients enrolled in the study remained stable or improved while receiving Leqembi over an average of 17 months of treatment.

The interim analysis, presented at the Alzheimer's Association International Conference in London on July 14, 2026, included 432 patients with early Alzheimer's disease who received at least seven Leqembi infusions as of May 2026. Among those patients, 75.9% remained in the same disease stage throughout treatment, while 6.6% improved, moving from mild Alzheimer's dementia to mild cognitive impairment. Nearly 87% of patients chose to remain on treatment.

The LEADER Study is a multicenter, retrospective study drawing on deidentified chart and electronic medical record data from 13 U.S. sites. The mean patient age was 74 years, and 55.8% were female. Results were consistent across sex, race, ethnicity, and APOE genotype groups.

Of 155 patients who transitioned to once-every-four-weeks intravenous maintenance therapy, nearly 81% remained stable or improved. Of 14 patients who transitioned to subcutaneous maintenance treatment, 85.7% maintained their disease stage.

Safety observations were consistent with the U.S. FDA-approved label. Amyloid-related imaging abnormalities were observed in 12.3% of patients overall, with most cases asymptomatic and mild in radiographic severity. No new ARIA-E events or significant hemorrhages were reported during intravenous maintenance therapy.

The study notes limitations common to retrospective real-world research, including potential biases, lack of a control group, and data inconsistency. Eisai serves as the lead for lecanemab's development and regulatory submissions globally, with Eisai and Biogen co-commercializing the product.