May 16 (Reuters) - Roche shares gained 4.7% at the market open on Thursday after an early-stage trial showed that the obesity drug candidate by newly acquired Carmot Therapeutics led to significant weight loss.

The Swiss drugmaker said the study in the first of three trial stages required for regulatory approval showed the compound known as CT-388 resulted in weight loss of 18.8%, when adjusted for a placebo effect, after 24 weeks in healthy adults with obesity.

Roche in December agreed to take over unlisted obesity drug developer Carmot for $2.7 billion upfront, joining a list of contestants seeking to challenge the dominant makers of weight-loss drugs Novo Nordisk and Eli Lilly.

Once-a-week injection CT-388 is Carmot's most promising drug candidate, mimicking the effect to two gut hormones GLP-1 and GIP like Lilly's Mounjaro, also known as Zepbound.

(Reporting by Ludwig Burger, editing by Andrey Sychev)