Weight-loss jab Mounjaro helps people shed much more weight than rival

Irish Examiner

20-05-2025

Weight-loss jab Mounjaro – dubbed the 'King Kong' of similar medicines – helps people shed significantly more weight than rival Wegovy, new research suggests.
Key research pitching the drugs against each other found Mounjaro was superior when it came to shedding pounds and losing inches, though both drugs worked.
Experts presented their findings at the European Congress on Obesity in Malaga and published them in the New England Journal of Medicine.
Both Mounjaro (tirzepatide) and Wegovy (semaglutide) are weight-loss medicines that make people feel fuller for longer and therefore less hungry.
The new randomised controlled trial involved 751 adult with obesity, but without type 2 diabetes.
They received either Mounjaro at the maximum tolerated dose (10mg or 15mg) or Wegovy (1.7mg or 2.4mg) once a week for 72 weeks.
The typical age of the people was 45 and most (65%) were female, with a typical body mass index (BMI) of 39.
All had at least one known obesity-related complication, such as high blood pressure, sleep apnoea or heart disease.
The typical drop in body weight at the end of the trial was a 20.2% reduction with Mounjaro and 13.7% with Wegovy, showing Mounjaro was superior.
The drop in waist circumference was also 18.4cm on average with Mounjaro and 13cm with Wegovy.
People on Mounjaro were more likely to reach their weight loss goals.
One limitation to the study was that people knew which drug they were taking, though the researchers said the findings were in line with previous studies.
The research was sponsored by Eli Lilly and Company, the manufacturer of Mounjaro.
Our study shows that treatment with tirzepatide was superior to semaglutide with respect to reduction in body weight and waist circumference
Dr Louis Aronne, from Weill Cornell Medicine in New York, who led the work, said the dual action of Mounjaro may explain the findings.
Both Mounjaro and Wegovy mimic a hormone produced in the body called GLP-1 – a substance that is released in the gut when people consume food.
This hormone slows the rate at which food is emptied from the stomach, reduces appetite via the brain and works on insulin levels.
But Mounjaro also mimics another hormone known as GIP (glucose-dependent insulinotropic polypeptide).
Dr Aronne said: 'Our study shows that treatment with tirzepatide was superior to semaglutide with respect to reduction in body weight and waist circumference.
'Tirzepatide, while a single molecule, pharmacologically activates two metabolic receptors, GIP and GLP-1, which have both overlapping and non-overlapping expression and function.
'This dual agonism of tirzepatide may contribute to the higher weight reduction observed in the current study compared to semaglutide, a mono-agonist.'
As people lost weight in the study, health factors such as blood pressure and unhealthy blood fats all improved.
Speaking at the European Congress on Obesity in Malaga, Spain on Sunday, Dr Aronne said: 'This is actually the first head-to-head trial of two obesity medications, so I think we're going to start seeing more of these as new medications become available.
'I saw a list the other day of 150 medications… that are now in development, so many people now realise how important it is to manage body weight in addition to other metabolic factors.
'I've called it the golden age of obesity treatment. It took a long time!'
Dr Aronne said semaglutide still remained an 'extremely effective' weight loss medication and that the trial did not intended to minimise its effects.
He added: 'For example, if you have a patient with a BMI of 32, which is class one obesity, they could get to a BMI in the mid 20s, right around 25 (with semaglutide), which is normal.
'So the majority of people with obesity will do just fine on semaglutide. People at the higher end – class two, class three obesity – may ultimately do better with tirzepatide.'