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BERLIN, Jan 27 (Reuters) - Roche's ROG.S experimental obesity drug, which works in a similar way to Eli Lilly's LLY.N Zepbound, produced as much as 22.5% weight loss in a mid-stage trial, underpinning the Swiss drugmaker's efforts to catch up with dominant rivals.

The company said on Tuesday that the Phase-II efficacy rate - adjusted for the placebo effect - reflected 48 weeks of treatment and was based on participants who fully followed the treatment regimen.

Taking into account patients who fell behind the treatment plan, the placebo-adjusted weight loss was 18.3%. The company said treatment for longer would likely yield better results.

Roche's experimental obesity drug CT-388 - a once-weekly injection - is a so-called dual GLP-1/GIP receptor agonist that regulates blood sugar and reduces appetite and is in the same class as Lilly's market-leading Zepbound, also known as tirzepatide and Mounjaro.

CT-388 was acquired through Roche's $2.7 billion purchase of U.S. biotech firm Carmot Therapeutics in 2023.

RESULTS VALIDATE TWO LARGER TRIALS DUE TO START

Roche said the results, based on the highest of five doses tested, validated its choices on two larger Phase III trials it designed late last year and due to start this quarter.

Roche, whose shares have been bolstered by positive trial results in multiple sclerosis and breast cancer, has costly ambitions to catch up with Lilly and Novo Nordisk NOVOb.CO in an obesity drug market some analysts say could reach $150 billion annually by the early 2030s.

Investors were lukewarm on the trial's results, with shares gaining 0.5% in morning trading, because it will be years until the drug is launched in an already-crowded market.

"The headline data released today puts CT-388 pretty much into the same efficacy ballpark as Zepbound," Jefferies analysts said in a research note.

ROCHE HOPES IT HAS SUPERIOR MODE OF ACTION

Still, the company's hopes remained intact that CT-388 offered a superior mode of action, said Manu Chakravarthy, Roche's head of development in the cardiovascular, renal, and metabolic fields.

"To see no plateau and this very steep linear trajectory is likely a reflection of this potential for higher efficacy," he told Reuters, adding that the result further reinforced Roche's "commitment to the field."

Roche has six drug candidates in trials for the treatment of obesity and related conditions like type 2 diabetes and hypertension, which could all be launched by 2030.

It forecasts three of them could become blockbusters with annual sales over $1 billion.

(Reporiting by Miranda Murray and Ludwig Burger; Editing by Shri Navaratnam and Bernadette Baum)

((Ludwig.Burger@thomsonreuters.com;))