Denmark's Novo Nordisk is sizing up a high-price niche market for its drug liraglutide as a weight-loss treatment, with the United States the prime opportunity.

The premium-price approach could turn it into a multibillion-dollar-a-year product, the company believes.

Novo is studying the injected drug - already on the market as a treatment for type-2 diabetes under the brand name Victoza - as a therapy for the seriously obese, with pivotal clinical trial results due in the first half of next year.

While some in the industry are sceptical about using so-called GLP-1 diabetes drugs such as liraglutide to fight obesity, Novo's Chief Science Officer Mads Krogsgaard Thomsen believes the approach can offer cost-effective benefits.

Glucagon-like peptide-1, or GLP-1, drugs work by stimulating insulin release when glucose levels become too high. Their ability to induce weight loss is an added benefit, since type-2 diabetes is linked to obesity.

What is more, the willingness of the U.S. Food and Drug Administration to license new obesity pills from Vivus and Arena Pharmaceuticals last summer shows the door is open to such new medicines, Thomsen said.

"It's positive. More physicians are now knowledgeable that pharmacotherapy can make a difference and the political establishment in the U.S. now knows that behaviour change alone is not enough," he said in an interview in London.

More than a third of American adults, or some 100 million people, are obese and the figure is rising fast, posing a growing threat to the nation's health.

Among this population group, liraglutide may help the severely obese, including those with related problems like interrupted breathing during sleep and pre-diabetes, who might otherwise receive stomach surgery.

"We are not going out to treat the 100 million ... We see this as solving a problem in a niche of maybe a few million patients," Thomsen said.

"If you took one million patients and gave them liraglutide at 3.0 milligrams (a day) at the U.S. price that would be a $6 billion market."

When used in diabetes as Victoza, liraglutide is given at daily doses of either 1.2 or 1.8 mg. Novo is betting on a higher dose to produce greater weight-loss in the obese. A key unknown is whether this will produce unacceptable side effects - and Thomsen admits this makes it something of a "joker" in the company's line-up of new products.

The main adverse effect of Victoza is nausea in some patients, although this is not strong enough in itself to account for the weight loss seen with the drug and Thomsen does not see nausea as a hurdle to regulatory approval.

More worrying, would be any evidence that high-dose liraglutide is linked to pancreatitis.

Given the high safety bar required for a new obesity drug, analysts are currently divided as to whether liraglutide will make it for weight loss - especially given past disappointments with diet drugs such as Sanofi's Acomplia.

If all goes according to plan, however, Novo aims to file for approval at the end of next year, implying a potential U.S. launch in late 2014 or early 2015 for a product that would add a new string to the bow of the world's biggest maker of insulin.