The late-stage trial showed that patients on Wegovy had a 20% lower incidence of heart attack, stroke or death from heart disease compared to those on a placebo, Novo said.
That's significantly better than the 15-17% expected by investors and analysts ahead of the eagerly awaited data. The results have not been peer reviewed.
The study, called SELECT, involved 17,500 overweight or obese people with a history of heart disease aged 45 years or older with no prior history of diabetes. It started almost five years ago to test if the weekly injection has medical benefits.
The news sent shares in Europe's second-most valuable listed company after LVMH (LVMH.PA) up more than 13% to record highs. The shares have surged almost 150% over the past two years.
The results may help persuade insurers in the U.S. and cost-conscious health authorities in Europe to cover the cost of Wegovy for a broader segment of patients.
The U.S. Medicare health plan for older Americans, for example, classifies weight-loss treatments as lifestyle drugs.
Experts say the new data could lead the U.S., where Wegovy costs $1,300 a month, to reassess that.
The results will likely stir debate about whether the long-term medical benefits are enough to reduce the overall burden on healthcare systems and the cost of treating heart disease in overweight and obese people.
"I suspect that medical claims savings from this are years away," said Dr. Jeff Levin-Scherz, a consultant at Willis Towers Watson, which advises employers on benefits.
He said the drugs at best may prove to be cost effective in terms of improving patients' lives, rather than lowering their total cost of care.
Large U.S. companies who manage their employees' healthcare benefits and traditionally covered weight-loss treatments have scaled back due to spiralling costs.
Still, the landmark trial data shows Wegovy has "the potential to change how obesity is regarded and treated", said Martin Holst Lange, executive vice president for development at Novo Nordisk, in the statement.
Novo Nordisk said it expects to file for regulatory approvals of a label indication expansion for the weekly injection in the U.S. and European Union this year.
The detailed results from the trial will be presented at a scientific conference later in 2023. Analysts will be seeking more detail on the data when Novo releases second-quarter results on Thursday.
CAUSE A STIR
The increasingly popular Wegovy has transformed the weight-loss market since its U.S. launch in June 2021, capturing the attention of patients, investors and celebrities worldwide and boosting Novo's shares.
The injection makes patients feel full for longer and leads to an average weight loss of around 15% when combined with changes to diet and exercise. It belongs to a class of drugs known as GLP-1 agonists, originally developed to treat type 2 diabetes.
Over 650 million adults worldwide are obese, more than three times as many as in 1975, and roughly another 1.3 billion are overweight, exacerbating conditions such as heart disease and diabetes, the World Health Organization says.
Sydbank analyst Soren Lontoft Hansen said the better-than-expected results will cause a stir among doctors who prescribe anti-obesity drugs.
"It may also increase the likelihood that payers in certain markets will engage in dialogue regarding Novo also being able to obtain subsidies in some markets," he said.
Barclays analysts have said a positive outcome from the study could boost uptake of Wegovy by 25% by 2030 if it gets approval for expanded use.
The company is already struggling to meet sky-rocketing U.S. demand.
In May, it said it was halving the supply of starter doses to the U.S. market to ensure supplies for existing patients. Reuters has reported that larger doses are also in short supply, which Novo has denied.
