A drug called retatrutide cut body weight by an average of 18.8% at its highest dose over 80 weeks in people living with obesity and type 2 diabetes, according to phase 3 trial results published in The Lancet.
A next-generation weight loss drug has produced substantial weight loss in a large trial of adults living with obesity or overweight and type 2 diabetes. Retatrutide — a drug not yet approved for general use — produced average weight loss of 11.9%, 16.8% and 18.8% at its 4mg, 9mg and 12mg once-weekly doses over 80 weeks, against 5.1% on placebo, in 1,152 adults. Among participants who started with a body mass index of 35 or more, those on the top dose lost more than a fifth of their body weight.
The results are from TRIUMPH-2, a phase 3 trial, so they reflect outcomes in a controlled research setting rather than everyday clinical use. Earlier this week, results from a separate trial, TRIUMPH-1, showed the drug also eased knee pain and sleep apnoea in people with obesity. No indication has been given as to when or whether the drug might reach patients through standard NHS prescribing routes.
Retatrutide works differently from existing weight loss medicines. It targets three separate hormone receptors — GLP-1, GIP, and glucagon — compared with drugs such as semaglutide (sold as Ozempic and Wegovy), which target only one. That triple action is thought to account for the larger weight reduction seen in the trial.
Type 2 diabetes (a condition where the body struggles to control blood sugar levels) and obesity are closely linked. The NHS already uses GLP-1 receptor drugs to treat both conditions, but access remains limited by cost and eligibility criteria.
Trial results don’t always translate directly into approved treatments. Drugs must pass further safety and efficacy reviews before regulators such as the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK consider approval. No timeline for that process has been announced for retatrutide.