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Eli Lilly’s new weight-loss injection has shown remarkable results, with patients shedding up to 29% of their body weight in clinical trials. This development further strengthens the US pharmaceutical giant’s expanding portfolio in the obesity treatment sector.

On Thursday, the company announced that the drug, named retatrutide, not only facilitated weight loss but also enhanced other aspects of physical health. Impressively, one in eight participants reported complete relief from knee pain by the end of the study.

During the late-stage trials, individuals battling obesity and osteoarthritis experienced an average weight loss of 28.7% over 68 weeks. This is a stark contrast to the 2.1% weight reduction observed in those who received a placebo, according to Lilly.

Interestingly, some participants opted out of the trial due to excessive weight loss, the company noted.

“These findings emphasize the significant impact of retatrutide,” stated Kenneth Custer, Lilly’s executive vice president. “We are optimistic that retatrutide could serve as a crucial option for patients seeking substantial weight loss and those facing related issues, such as knee osteoarthritis.”

The company said it expects to announce more trial results for the drug in 2026.

Retatrutide is a next-generation GLP-1 weight-loss drug from Lilly. These weight-loss medicines, such as Zepbound, have helped propel Lilly to become the first pharmaceuticals group to top $1tn in market value, though it has since dipped below that mark. Its shares were up 1 per cent in pre-market trading on Thursday.

Thursday’s results were Lilly’s “strongest efficacy to date” for retatrutide, said Evan Seigerman, an analyst with BMO Capital Markets.

“These results help to solidify retatrutide’s profile as an even higher efficacy next-generation GLP-1+ asset,” he said in a report.

Previous trials of Lilly’s popular weight-loss drug Zepbound, which was approved in the US in 2023, showed average weight loss of about 15 per cent.

Lilly’s trial results also lifted shares of rival Novo Nordisk, which rose 3.6 per cent in Denmark on Thursday.

The results come on the back of a positive August update in which Lilly said its orforglipron pill had met a key target by reducing the body weight of people who were overweight and suffered from diabetes by an average of 10.5 per cent. It said that the side effects were similar to those for its injectable weight-loss drugs.

In November, the US Food and Drug Administration said it would prioritise its review of orforglipron and the drug is expected to go on sale next year.

Lilly announced a drug pricing deal with President Donald Trump last month that included lower prices for weight-loss drugs in exchange for broader access to the drugs in US federal health programmes.