SAN DIEGO, June 25 (Reuters) - Novo Nordisk on Sunday said a late-stage trial found that a high-dose oral version of its drug semaglutide helped overweight or obese adults lose 15% of their body weight, which is in line with recent results for other experimental obesity pills.

Novo plans to seek U.S. and European regulatory approval of the high-dose pill later this year, but timing of a market launch is "to be determined," according to Mico Guevarra, medical director at Novo Nordisk.

The Danish company has had supply issues and struggled to keep up with soaring U.S. demand for Wegovy and Ozempic, the respective brand names for semaglutide sold as once-weekly injections for treating obesity and diabetes. Wegovy contains 2.4mg of semaglutide.

The drug, designed to activate hormones that regulate blood sugar, slow stomach emptying and decrease appetite, is part of a new class that has reignited researcher and investor interest in the weight-loss treatment market, which is estimated to reach $100 billion by the end of the decade.

"We are upping production as much as we can," Guevarra said in an interview here on the sidelines of the annual meeting of the American Diabetes Association.

Novo Nordisk already markets an oral semaglutide, under the brand name Rybelsus, for treatment of type 2 diabetes, but its highest dose is 14mg.

The late-stage trial of 667 obese and overweight adults tested a dose of 50mg, showing that it resulted in average weight loss of 15.1% after 68 weeks, when used alongside diet and physical activity, compared with 2.4% for the placebo group.

Oral semaglutide, according to the FDA label, needs to be taken in the morning on an empty stomach, 30 minutes before eating, drinking, or using any other oral medication - you are allowed only 4 ounces of plain water. If you eat too soon, the pill is less effective, but if you wait longer than 30 minutes its absorption may be enhanced.

Other companies are working on obesity pills that don't have such dietary restrictions, and would in theory also appeal to patients who don't want to inject themselves weekly.

Dr. Filip Knopf, professor of endocrinology at Gentofte Hospital, University of Copenhagen and Novo's study presenter, said his experience is that 20% to 25% of patients would rather have a daily pill instead of a weekly semaglutide injection.

At the ADA meeting on Friday, results from an Eli Lilly mid-stage trial showed that the highest dose of its experimental pill orforglipron helped people who were obese or overweight lose 14.7% of their body weight after 36 weeks, and their weight loss had not yet appeared to plateau.

Novo Nordisk said most patients in its obesity trial reported gastrointestinal side effects from oral semaglutide, including mostly mild-to-moderate nausea, constipation, diarrhea and vomiting.

Around 13% of patients experienced "altered skin sensation," which was mostly resolved after several weeks, Dr. Knopf said.

Results from a separate late-stage trial presented at the ADA meeting showed once-daily oral semglutide, at a dose of up to 50mg, helped patients with type 2 diabetes reduce their blood sugar levels by as much as 2 percentage points.

Details of both Novo trials were also published in the peer-reviewed Lancet medical journal.

(Reporting By Deena Beasley; editing by Diane Craft)