Novo-Nordisk A/S said on Monday an older oral version of its semaglutide drug failed to meet its main goal in late-stage trials testing whether the medicine can slow cognitive decline in Alzheimer's patients, sending its share price down 12%.

The data is key for Novo because Alzheimer's disease would be a large new market for GLP-1 medicines like semaglutide after blockbuster success in the treatment of obesity and diabetes. Alzheimer's patients currently have limited treatment options.

The drug being tested is Novo's Rybelsus, a pill currently approved only for treatment of type 2 diabetes. Both Rybelsus and Novo's blockbuster drugs Ozempic and Wegovy are based on the same active ingredient, semaglutide, a GLP-1 medicine.

"While semaglutide did not demonstrate efficacy in slowing the progression of Alzheimer's disease, the extensive body of evidence supporting semaglutide continues to provide benefits for individuals with type 2 diabetes, obesity, and related comorbidities," Chief Scientific Officer Martin Holst Lange said in a statement.

The results from the two trials of early-stage patients, called EVOKE and EVOKE+, mark another setback for the Danish drugmaker, which boomed on the success of blockbuster medicine Wegovy before slowing sales growth and a tumbling share price prompted a CEO change and mass layoffs.

The setback reinforces analyst scepticism about Novo's Alzheimer's ambitions, with UBS having estimated just a 10% probability of success.

The company's Executive Vice President for Product and Portfolio Strategy Ludovic Helfgott had described the Alzheimer's trials as a "lottery ticket" in September, a reference to its uncertain prospects yet huge potential.

Alzheimer's disease and other dementias affect more than 55 million people globally. There is no cure.