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In surprise result, Alzheimer’s drug from Eisai, Biogen shows benefit in large trial

An experimental Alzheimer’s disease drug developed by Eisai and Biogen succeeded in a large Phase 3 trial, raising its chances for regulatory approval and boosting a long-running hypothesis about how to treat the most common cause of dementia.

Trial results showed treatment with the drug, called lecanemab, slowed clinical decline by 27% compared to a placebo over an 18-month period, the companies said in a Tuesday statement. Alzheimer’s symptoms were measured on a commonly used rating scale that assesses cognitive and functional performance.

Treatment was associated with higher rates of an imaging abnormality that’s typical of drugs like lecanemab and can involve swelling and microhemorrhages in the brain. Most cases were not symptomatic, however, according to Eisai and Biogen’s statement.

The findings are a positive surprise, following years of setbacks and failures for similar Alzheimer’s drugs from Eli Lilly, Roche, Pfizer and others. They could factor into the Food and Drug Administration’s current review of lecanemab, which Biogen and Eisai already submitted for accelerated approval based on earlier data. The Phase 3 trial that’s now read out results is meant to confirm those earlier findings.

With positive data in hand, Eisai plans to ask the FDA for full approval of lecanemab by the end of March. The company aims to seek clearance in Japan and Europe by that time as well.

Eisai and Biogen only disclosed limited details on the study results, which they will present in full at a medical conference in November and are likely to be pored over by the Alzheimer’s research field.

In absolute terms, the difference in scores between study participants who received treatment and those given a placebo was 0.45 on the main symptom rating scale, known as CDR-SB. That difference is near what some analysts had previously said would represent a clinically meaningful benefit.

The imaging abnormality, known as ARIA, occurred in 21% of patients treated with lecanemab and 9% of those on placebo. About 3% of patients on lecanemab patients had symptomatic ARIA with swelling in the brain, and 0.7% had symptomatic ARIA with micro-bleeding.

Success with lecanemab would help Biogen recover from its disastrous attempts to sell its first Alzheimer’s drug. Called Aduhelm, the drug controversially won FDA approval last summer despite conflicting results in clinical testing. Since then, Aduhelm has earned negligible revenue amid fierce pushback from both doctors and insurers. The U.S. Medicare program for older adults refused to pay for it because of the drug’s questionable benefit.

In response, Biogen has eliminated commercial support for the drug, laid off staff and announced plans for its CEO to step down. Biogen and Eisai were also partnered on Aduhelm but in March reworked terms of their collaboration, with Biogen taking full control of commercialization decisions.

For lecanemab, Eisai is taking the lead on development and regulatory submissions. The companies will share profits equally, however.

Like Aduhelm, lecanemab has had a mixed track record in clinical testing, although past results will now be overshadowed by the positive Phase 3 findings. In late 2017, the companies declared it was unlikely lecanemab would show a benefit in a mid-stage study, only to later find positive signs. The data were difficult to parse, however, and were much debated by researchers.

Eisai and Biogen pushed on, beginning in 2019 the Phase 3 study called CLARITY AD. The trial enrolled 1,795 people with early Alzheimer’s, who were randomized to receive either lecanemab or placebo.

Along with lifting Eisai and Biogen, lecanemab’s results might also reinvigorate research into the main hypothesis surrounding Alzheimer’s, which points to the buildup of a protein called amyloid in the brain as the disease’s cause.

Lecanemab as well as two other drugs still in late-stage development — Eli Lilly’s donanemab and Roche’s gantenerumab — seek to treat the disease by eliminating the toxic clumps of amyloid.