Study compares Mounjaro to Wegovy for weight loss

A new study has shed a light on the effectiveness of two popular weight loss drugs, and while the research was sponsored by one of the manufacturers, GPs say it reflects an ‘extension of evidence’ about the medications.
 
The research comes at a time when the medications investigated, tirzepatide and semaglutide, are more popular than ever in Australia and around the world, with widespread patient interest.
 
The ‘head-to-head’ SURMOUNT-5 clinical trial, sponsored by Eli Lilly and released on Wednesday, found ‘Mounjaro delivered a clinically meaningful benefit and statistically significant weight loss’, saying patients experienced a 47% greater relative weight loss compared to Wegovy after 72 weeks.
 
It found participants using the medications both lost significant amounts of weight, with those using tirzepatide (sold as Mounjaro) losing an average of 20.2% (22.8 kg) of body weight compared with those on semaglutide (Wegovy), who averaged a 13.7% (15 kg) loss.
 
However, Dr Gary Deed, member of the RACGP Expert Committee – Quality Care (REC–QC) and Clinical Editor of the college’s diabetes management handbook, told newsGP sponsored studies always carry ‘concerns about risks of biases’, adding that the results are preliminary and not yet peer reviewed.
 
‘It reflects an extension of evidence that, based upon sound lifestyle advice including calorie restriction and physical activity, these medications are emerging as effective weight management strategies when used appropriately,’ he said.
 
‘My clinical findings align that both agents when used appropriately, and with the support from lifestyle changes, may be effective in people wanting to utilise them.
 
‘Individual responses vary but the ability to have a choice between different therapies allows us to individualise management.’
 
Dr Deed said the research acts as an increase in the evidence base for GPs, as they work towards ‘more tailored interventions for obesity which is a chronic disease that underscores many metabolic conditions’.
 
However, with the popularity of both medications showing no sign of slowing down, Eli Lilly said it is working with stakeholders to ‘secure a path to affordable and equitable access to Mounjaro in Australia’.
 
The study compared efficacy of tirzepatide and semaglutide in adults who had a body mass index (BMI) greater than 30, or a BMI greater than 27–30 together with weight-related health impacts.
 
The 700 participants did not have diabetes, and participants and researchers both knew which medications participants were taking.
 
Chair of the REC–QC Professor Mark Morgan described the trial as ‘open-label and therefore subject to potential biases’.
 
The research’s release comes after a separate, much larger-scale cohort study of 41,000 people investigated differences in weight loss between patients receiving tirzepatide compared with semaglutide.
 
‘In this population of adults with overweight or obesity, use of tirzepatide was associated with significantly greater weight loss than semaglutide,’ the study concluded.
 
‘Future study is needed to understand differences in other important outcomes.’
 
But in this study too, Professor Morgan said ‘detail was lacking about safety and side effects’.
 
In August, Wegovy was launched in Australia for the first time, making it the latest semaglutide drug specifically targeted for weight loss to hit the market.
 
Just one month later, GPs were allowed to prescribe Mounjaro to eligible patients as a treatment for overweight and obesity, after it was previously only indicated for the treatment of adults with insufficiently controlled type 2 diabetes, as an adjunct to diet and exercise.
 
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Mounjaro semaglutide tirzepatide Wegovy