By Jamie Gumbrecht, CNN

(CNN) — An oral version of semaglutide, the active ingredient in blockbuster drugs Ozempic and Wegovy, failed to slow the progression of Alzheimer’s disease in closely watched trials, drugmaker Novo Nordisk said Monday.

In two Phase 3 trials of more than 3,800 adults receiving standard care for Alzheimer’s, the company evaluated whether an older pill form of semaglutide worked better than a placebo. The drug was shown to be safe and led to improvements in Alzheimer’s-related biomarkers, the company said, but the treatment did not delay disease progression.

Novo had long treated Alzheimer’s as a long-shot bet for the popular GLP-1 drugs. Use of these drugs for diabetes and weight loss has exploded in recent years, and they have shown benefits for a wide range of additional health conditions, such as protecting the heart and kidneys, reducing sleep apnea and potentially helping with addiction.

Smaller trials and animal studies had suggested that GLP-1s might help slow cognitive decline or reduce neuro-inflammation, but larger trials like Novo’s were needed to confirm whether patients saw actual benefits.

“Based on the significant unmet need in Alzheimer’s disease as well as a number of indicative data points, we felt we had a responsibility to explore semaglutide’s potential, despite a low likelihood of success,” Dr. Martin Holst Lange, chief scientific officer and executive vice president of research and development at Novo Nordisk, said in a statement Monday that thanked the trial participants.

A one-year extension of the trials will be discontinued, Novo said. Results from the trials have not yet been peer-reviewed or published but will be presented at upcoming scientific conferences.

Despite disappointment over the new results, there are more questions to consider around GLP-1s and dementia. Scientists are eager to see more details about Novo’s trials, including the reported changes in biomarkers for Alzheimer’s.

“Considering the amount of real-world evidence emerging in the field, we really need to evaluate whether these agents work more for prevention rather than treatment of established cases,” said Dr. Paul Edison, a professor of neuroscience at Imperial College London who has studied another GLP-1, liraglutide, and cognitive decline.

The Alzheimer’s Association said Monday that research involving GLP-1s will continue.

“These results will help us refine our understanding of this class of drugs,” said Dr. Maria Carrillo, the Alzheimer’s Association’s chief science officer and medical affairs lead. “Though this semaglutide pill did not help against Alzheimer’s, the field will continue to investigate this class of drugs, as they may act differently.”

Novo shares fell Monday after the Alzheimer’s trial announcement. The company has been facing increased competition in the weight loss market and recently announced lowered prices for some cash-paying patients using Ozempic and Wegovy.

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CNN’s Meg Tirrell contributed to this report.