Ozempic Rival Retatrutide Delivers 25% Weight Loss In Phase 3 Trial

An experimental weight-loss injection has helped people with obesity lose an average of up to 25 per cent of their body weight at the highest dose, according to results from a large Phase 3 clinical trial. The drug, called retatrutide, is being developed by Eli Lilly. Researchers studied 2,339 adults with obesity who did not have diabetes. Participants were given weekly injections of 4 mg, 9 mg or 12 mg of retatrutide, or a placebo.

After 80 weeks, people receiving the highest 12 mg dose had lost an average of 25 per cent of their starting body weight. Those taking 9 mg lost an average of 23.7 per cent, while the 4 mg group recorded an average reduction of 17.6 per cent. The placebo group lost 3.9 per cent.

The researchers also looked at some health problems linked to obesity. Among participants with knee osteoarthritis, those receiving the 12 mg dose experienced a greater reduction in knee pain than those given the placebo.

The drug was also tested in people with obstructive sleep apnoea. At the highest dose, the number of breathing disruptions during sleep fell by an average of 32.1 episodes per hour, compared with a reduction of 9.6 episodes per hour in the placebo group.

A smaller group of 532 participants was followed for a further 24 weeks. Among those who had initially received the 12 mg dose, average weight loss reached 29.9 per cent after 104 weeks. However, these longer-term results came from a smaller extension group and should not be treated as a two-year comparison with placebo.

Retatrutide works differently from medicines that target only one or two hormone pathways. It activates receptors linked to GLP-1, GIP and glucagon, with the aim of reducing appetite while also affecting the body's energy use.

However, the treatment was also linked to side effects. Gastrointestinal problems were among the most common, particularly during dose increases. About 42 per cent of people receiving the highest dose reported nausea. Around 11 per cent stopped treatment because of adverse events, compared with 4.6 per cent in the placebo group.

Researchers said the trial was not designed to establish the drug's cardiovascular safety. It also did not directly compare retatrutide with existing weight-loss medicines such as semaglutide or tirzepatide.

Eli Lilly funded the research and was involved in collecting and analysing the data.

The research has been published in The New England Journal of Medicine.