A new weekly injection for type 2 diabetes, retatrutide, has shown significant reductions in blood sugar and body weight in a phase 3 trial. The drug mimics three gut hormones—GLP-1, GIP, and glucagon—to control appetite, blood sugar, and metabolism, and also increases energy expenditure, unlike existing treatments.
The trial, published in the Lancet, involved 930 adults with type 2 diabetes who were not taking other diabetes medications. Participants received either 4mg, 9mg, or 12mg of retatrutide or a placebo for 40 weeks. Those on retatrutide lost an average of 11.5% to 15.3% of their body weight, compared to 2.6% for the placebo group. Blood sugar levels (HbA1c) dropped by 1.7 to 1.9 percentage points on the drug, versus 0.8 points for placebo.
Side effects were generally mild to moderate, with gastrointestinal symptoms being most common. Fourteen serious adverse events occurred, including two in the placebo group. The authors suggest retatrutide could improve outcomes for patients needing more intensive treatment, though further trials are ongoing.
Experts have welcomed the findings but urge caution. Dr Kath McCullough of the Royal College of Physicians called the results 'very encouraging' but stressed that medications are not a 'silver bullet'. Dr Marie Spreckley from the University of Cambridge noted that head-to-head trials with existing drugs like semaglutide are needed to determine comparative effectiveness. Dr Lucy Chambers of Diabetes UK said the findings are promising and look forward to further research on long-term effects.
