TOKYO, Japan (AP) — Shares of Biogen and other drugmakers researching Alzheimer’s disease soared early Wednesday after Japan’s Eisai Co said its potential treatment appeared to slow the fatal disease’s progress in a late-stage study.

Eisai announced results late Tuesday from a global study of nearly 1,800 people with early-stage Alzheimer’s.

The drugmaker said early results showed that its treatment, lecanemab, reduced patient clinical decline by 27 per cent when compared to a placebo or fake drug after 18 months of the infused treatment. Patients were monitored using a scale that measures how they do in areas like memory, judgement, problem-solving and personal care.

Eisai Co Ltd said it would discuss full results from the research at a conference in late November. It also plans to publish its findings in a peer-reviewed medical journal.

The company is already seeking an accelerated approval from the US Food and Drug Administration, and the agency is expected to decide by early next year. Eisai and Biogen will co-promote the drug.

The initial results appear to be “quite robust” and will likely support regulatory approval, Mizuho Securities analyst Graig Suvannavejh said in a research note.

A statement from the Alzheimer’s Association called the findings the most encouraging to date for potential treatments of the underlying disease causes.

Alzheimer’s is a progressive neurological disease with no known cure. Long-standing treatments on the market just manage symptoms, and researchers don’t fully understand what causes the disease.

Last year, Biogen’s Aduhelm became the first new Alzheimer’s drug introduced in nearly two decades. But it has largely flopped after debuting with a price tag of $56,000 annually, which Biogen later slashed.

Doctors have been hesitant to prescribe it, given weak evidence that the drug slows the progression of Alzheimer’s. Insurers have blocked or restricted coverage over the drug’s high price tag and uncertain benefit.

Like Aduhelm, lecanemab, which Eisai developed and ran through clinical trials, seeks to remove a protein called beta-amyloid from the brain.

But Eisai executives say lecanemab focuses more on floating clumps of the protein before it forms a plaque, which is what Aduhelm targets.

Eli Lilly and Co also is developing a potential treatment, donanemab, that helps clear the protein.

Shares of Cambridge, Massachusetts-based Biogen Inc jumped more than 50 per cent in pre-market trading Wednesday morning to top $300. The stock had largely tumbled since Aduhelm’s debut last year.

Shares of Indianapolis-based Eli Lilly and Co were up eight per cent.