Lecanemab Granted Priority Review by Regulators in Japan

Alzheimer's therapy just won accelerated approval in US as Leqembi

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by Steve Bryson, PhD |

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Lecanemab (BAN2401), an amyloid-targeted antibody therapy for early Alzheimer’s disease, has been granted priority review in Japan, according to Eisai and Biogen, its developers.

Priority review, as designated by the Japanese Ministry of Health, Labour and Welfare (MHLW), shortens the review period of applications seeking approval in the country for new medicines for serious medical conditions.

Earlier this month, the therapy was granted accelerated approval in the U.S. under the brand name Leqembi to treat Alzheimer’s patients with mild cognitive impairment or mild dementia.

At the same time, Eisai also submitted an application to U.S. regulators asking for the therapy’s approval under a traditional pathway. Similar approval applications are now being reviewed in Europe and China, according to a Biogen press release.

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Full Phase 3 Trial Data Support Lecanemab for Early Alzheimer’s

Eisai, Biogen seeking therapy’s approval in Japan

Lecanemab, infused directly into the bloodstream, is an antibody-based therapy that binds to a harmful version of the protein beta-amyloid. This protein forms toxic clumps called amyloid plaques in the brains of those with Alzheimer’s, leading to nerve cell loss and symptoms of cognitive decline and/or dementia.

By blocking beta-amyloid, lecanemab is designed to enable the immune system to clear this protein before it forms plaques, potentially slowing disease progression.

The application submitted to Japanese authorities requesting lecanemab’s approval contained data from two clinical trials: a Phase 2b trial, called Study 201 (NCT01767311), and the Phase 3 Clarity AD trial (NCT03887455).

Study 201 enrolled 856 patients with Alzheimer’s dementia or mild cognitive impairment with confirmed beta-amyloid plaques in their brains. Participants received a placebo, or the therapy, at one of three doses, once or twice per month.

Data showed that 18 months (1.5 years) of treatment with lecanemab at the highest dose (10 mg/kg twice monthly) significantly slowed cognitive decline by 30% compared with the placebo. Cognitive benefits were seen as early as six months, as indicated by the Alzheimer’s Disease Composite Score (ADCOMS).

PET scans also revealed less beta-amyloid accumulation in the brain, with about 81% of lecanemab-treated patients no longer showing evidence of amyloid plagues after 18 months. Data from Study 201’s open-label extension study (10 mg/kg dose for up to two years) showed that treatment rapidly and sustainably reduced brain beta-amyloid after one year.

Clarity AD included 1,795 people with early Alzheimer’s, who were given either lecanemab at a dose of  10 mg/kg or a placebo for 1.5 years. Similarly to Study 201, the therapy significantly delayed cognitive decline by 27% versus the placebo, as assessed with the Clinical Dementia Rating-Sum of Boxes (CDR-SB) scale.

In participants treated with lecanemab, CDR-SB scores increased — indicating dementia progression — at a slower rate than those given a placebo (1.21 vs. 1.66 points). Treatment also slowed disease progression, as demonstrated by other measures, including ADCOMS, and sustainably reduced the amount of amyloid plaques in the brain.

Lecanemab’s long-term safety and efficacy are being evaluated in CLARITY AD’s extension study, in which all participants are receiving treatment.

Moving forward, the Phase 3 AHEAD 3-45 trial (NCT04468659) will test the therapy’s impact in up to 1,400 people, ages 55–80, with elevated levels of amyloid in their brains but without overt disease symptoms, or preclinical Alzheimer’s disease. Top-line data from this study, which is now recruiting at more than 100 clinical sites, many in the U.S., is expected in 2027.