Lilly’s Mounjaro outperforms rival in landmark head-to-head trial, setting new benchmark for obesity therapies

Eli Lilly’s Mounjaro (tirzepatide) has demonstrated significantly greater weight loss and waist circumference reduction than Novo Nordisk’s Wegovy (semaglutide) in the first head-to-head trial comparing the two therapies.

Findings from the Phase 3 SURMOUNT-5 trial were unveiled at the European Congress on Obesity, highlighting Mounjaro’s superiority in treating adults with obesity or those overweight with weight-related comorbidities, excluding type 2 diabetes, over a 72-week period.

The results were striking: participants receiving the dual GIP-GLP-1 receptor agonist Mounjaro lost an average of 20.2% (22.8kg) of their body weight, compared to 13.7% (15kg) in those treated with the mono GLP-1 receptor agonist Wegovy. Waist circumference reductions followed a similar pattern, down 18.4 cm with Mounjaro versus 13.0 cm with Wegovy, a 42% greater decrease for Mounjaro.

Lilly’s obesity therapy also led across all major weight-loss thresholds. More than 64% of patients on Mounjaro achieved at least a 15% reduction in body weight, compared to 40.1% of those on Wegovy.

Associate Professor Sarah Glastras, Head of Department and Senior Staff Specialist in Endocrinology at Royal North Shore Hospital Sydney, called the results “highly significant for doctors, patients, and the healthcare system more broadly.”

“The publication of this trial data is an exciting development, giving us a deeper understanding of weight management medications and ensuring doctors and patients are in a better position to make informed decisions on treatment,” Associate Professor Glastras explained. “There is a wealth of evidence to support the use of these medicines in people living with obesity and overweight. The health gains and community benefits of significant and sustained weight loss can’t be ignored.”

Dr Bradley Curtis, Executive Director and Medical Lead, Cardiometabolic Health at Eli Lilly Australia and New Zealand, reinforced the clinical impact of the findings.

“The 47% relative weight loss benefit of Mounjaro over Wegovy is highly significant, while the lower rate of treatment cessation with Mounjaro is also noteworthy,” he said. “The dual action of Mounjaro on GIP and GLP-1 continues to set new benchmarks for chronic weight management, as it has for glycaemic control in people with type 2 diabetes.”

With over a third of Australian adults living with obesity, the burden on the healthcare system is mounting. The National Obesity Strategy estimates the annual direct and indirect costs of obesity to be around $12 billion. In this context, the findings of SURMOUNT-5 are not just clinically relevant, they carry significant economic and public health implications.

Lilly is hopeful the results will influence the Pharmaceutical Benefits Advisory Committee (PBAC), which is currently reviewing advice requested by Federal Health Minister, Mark Butler, on pathways to equitable access for obesity medications.

The Royal Australian College of General Practitioners (RACGP) has also pivoted its stance, now supporting the inclusion of effective weight-loss therapies on the Pharmaceutical Benefits Scheme (PBS).

Dr Terri-Lynne South, RACGP Specific Interest Obesity Management Chair, said “If a medicine is effective and safe, and the cost of a condition to the health system outweighs the cost of treating it with a medicine, there’s a strong case to subsidise that medicine.”

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