An experimental drug just showed it can help slow Alzheimer's, offering new hope for patients and a major boost to pharma giant Eli Lilly

• An experimental drug for Alzheimer's disease has cleared a big hurdle, moving it closer to approval.
• The pharma giant Eli Lilly said donanemab slowed cognitive decline in people with Alzheimer's.

After years of stagnation, treatments for Alzheimer's are experiencing a revival.

On Wednesday, the pharma giant Eli Lilly said its experimental drug donanemab had successfully slowed cognitive and functional decline in patients with early-stage Alzheimer's, offering some hope to people with a condition that lacks good treatment options. Lilly said it would submit the data to US regulators before the end of June and hoped to win approval by the first half of next year.

The positive results, provided in a press release, come months after a similar Alzheimer's drug from Biogen and Eisai, called Leqembi, received accelerated approval from the US Food and Drug Administration. That drug can moderately slow the progression of Alzheimer's in people who have the early stages of the disease.

New Alzheimer's treatments could rack up billions in sales by slowing the disease

Neither drug amounts to a cure for Alzheimer's, which affects roughly 6.5 million Americans. Still, Wall Street analysts estimate that each could generate billions in sales. Jefferies, for example, said in a March 13 note that donanemab could bring in $7.5 billion a year for Lilly at its peak. Lilly's stock jumped 8.8% in early trading on Wednesday, after the results were announced.

Eli Lilly's trial primarily looked at how its drug would affect patients' ability to perform daily tasks like driving and making a meal, as measured by the integrated Alzheimer's Disease Rating Scale, or iADRS. By that measure, the late-stage trial, which included 1,182 participants, slowed their rate of decline by 35% over 18 months. Lilly said it planned to submit the results for publication in a peer-reviewed journal.

"This is the first Phase III trial of any investigational medicine in Alzheimer's disease to deliver 35% slowing of clinical and functional decline," Dawn Brooks, the global development leader overseeing donanemab, said in an interview.

"This does surpass what we've seen in the field to date," Brooks added. "Less progression means more time for patients."

Weighing donanemab's benefits and side effects

In the trial, nearly half of patients who got donanemab saw no worsening of their Alzheimer's symptoms after a year of treatment, while 71% of patients who got the placebo saw their disease advance.

"We want more time to remember more things. And so I think that time concept is kind of universal and helpful to convey clinical meaningfulness," Dr. John Sims, the head of medical for donanemab, told Insider.

Patients and their physicians will have to weigh the drug's benefits against some serious side effects. Taking the drug can lead to cases of swelling or other abnormalities in the brain, the trial found. While most cases aren't serious, Lilly said at least two deaths were linked to these side effects.

Donanemab, like Leqembi, works to lower levels of proteins in the brain that are thought to be responsible for the progression of Alzheimer's. In the trial, patients received donanemab until scans showed their brains were clear of those proteins, called beta-amyloid. Leqembi, on the other hand, is intended to be given for a longer period of time. Both are given by IV, with donanemab administered every four weeks and Leqembi every two weeks.

Comparing Alzheimer's treatments

Clinicians and analysts will most likely pore over the data on Leqembi and donanemab to suss out the advantages and disadvantages of each drug. Leqembi slowed the rate of cognitive decline in Alzheimer's patients by 27% over 18 months in a late-stage study. By the same measure, known as CDR-SB, donanemab slowed cognitive decline by 36%.

SVB Securities analysts said in an April 16 note that if donanemab showed "notably better efficacy" compared with Leqembi, meaning a 35% slowing as measured by CDR-SB, they expected Eli Lilly's shares to jump.

Sims said that because patients receive donanemab for a set period of time, that would help lower the burden for many patients.

"I think that will be an attractive aspect for people," he added. "What we now are thrilled about is that we hope there will be multiple options for patients."

New products could give Eli Lilly a boost

Right now, Leqembi isn't covered by the US government's Medicare program, making it difficult for patients to get the treatment. That could change if the drug gets full approval from the FDA, which could happen as soon as July.

Another high-profile drug for Alzheimer's received accelerated approval in 2021 but has flopped commercially because of mixed data on whether it actually helps patients. That drug, Aduhelm, was also developed by Eisai and Biogen.

Lilly is counting on new products like donanemab to help it boost sales. Revenue tumbled 11% in the first quarter as sales of the company's coronavirus-fighting antibody treatment declined. Another new product that could generate significant sales is Lilly's diabetes drug Mounjaro. The company recently published data indicating the drug could help patients lose almost 16% of their body weight and said it planned to ask FDA to approve the treatment for weight loss.