CHICAGO (Reuters)

An experimental Alzheimer’s drug developed by Eli Lilly and Co slowed cognitive decline by 35% in a closely watched late-stage trial, the company said on Wednesday (May 3), raising hopes for a second effective treatment for the brain-wasting disease.

Eli Lilly’s shares opened at a record high of $415 on Wednesday, and were up 4.2% at $421.01 in early trading.

The drug, donanemab, met all goals of the trial. It slowed progression of Alzheimer’s by 35% to 36% compared to a placebo in 1,182 people diagnosed with early-stage disease based on scans showing brain deposits of amyloid protein and intermediate levels of tau protein, Lilly said.

The trial’s other 552 patients had high levels of tau, suggesting they would be less likely to respond to the treatment.

After combining both groups, donanemab was shown to slow progression of Alzheimer’s by 22% using a Lilly-developed scale to measure cognition and activities of daily living, and by 29% based on a more commonly used scale of dementia progression.

“These are the strongest phase 3 data for an Alzheimer’s treatment to date,” said Maria Carrillo, chief science officer for the Alzheimer’s Association.

Using the commonly used dementia scale, trial results published last year showed that Eisai Co Ltd and Biogen Inc’s Leqembi reduced the rate of cognitive decline by 27% in patients with early Alzheimer’s.

In the donanemab treatment group, Lilly said brain swelling, a known side effect of drugs of this type, occurred in 24% of the participants, with 6.1% experiencing symptoms. Brain bleeding occurred in 31.4% of the donanemab group and 13.6% of the placebo group.

In the Leqembi Phase 3 trial, the drug was associated with brain swelling in nearly 13% of its study participants.

Lilly said the incidence of serious brain swelling in the donanemab study was 1.6%, including two deaths attributed to the condition, and a third, after an incident of serious brain swelling.

Dr. Eric Reiman, executive director of the Banner Alzheimer’s Institute, which is running an Alzheimer’s prevention study of donanemab in presymptomatic patients, said he was “very excited” about the findings. “Clearly, one saw benefits here, but there is some risk that needs to be considered.”

Lilly said it plans to file for traditional U.S. approval by the end of June, and with regulators from other countries shortly thereafter.

“There are risks in medicine, but I think when you look at these results in the context of a fatal life-threatening disease, (they) are quite meaningful,” said Lilly Neuroscience executive Anne White in an interview with Reuters.

Study participants received a monthly intravenous infusion of donanemab. When follow-up brain scans showed that amyloid had been removed, the treatment was stopped and volunteers were moved to the placebo-arm of the study. Half of the trial participants had no evidence of amyloid plaques at 12 months, the company said.

It also said 47% of donanemab patients in the 18-month trial had no disease progression at 12 months, compared with 29% of the placebo group.

Lilly’s drug is likely to become the third in its class on the market following U.S. approval of two similar medicines developed by partners Eisai and Biogen – Leqembi and Aduhelm, which failed to gain traction with doctors or insurers after showing little evidence that they slowed cognitive decline.

Both were approved under the FDA’s accelerated review program, based on their ability to remove amyloid plaques.

Leqembi is currently undergoing the FDA’s standard reviewprocess, with a decision due by July 6.

Lilly is still working on finalizing the price for donanemab, and plans it in the same range as other similar therapies, CEO David Ricks told CNBC.

Over 6 million Americans are living with Alzheimer’s,and the number is projected to rise to nearly 13million by 2050, according to the Alzheimer’s Association.