Lilly scores against Novo Nordisk in weight loss contest

There’s no data from a head-to-head trial directly comparing Eli Lilly and Novo Nordisk’s GLP-1 agonist drugs yet, but an observational study has found that Lilly’s tirzepatide seems to be better at achieving weight loss.

Tirzepatide – a dual GLP-1/GIP agonist sold as Mounjaro for diabetes – was significantly more likely to achieve a weight loss of 5% or greater than those taking Novo Nordisk’s GLP-1 agonist semaglutide, the active ingredient in diabetes drug Ozempic.

The study looked at electronic health record (EHR) data from more than 18,000 overweight or obese people who were new users of tirzepatide or semaglutide labelled for diabetes treatment; in other words, not the higher strength formulations sold, respectively, as Zepbound and Wegovy for obesity.

More than half of the patients in the cohort were diabetic, which provides an indication of how often the drugs were being used off-label for weight loss in the study period, which extended from May 2022 to September 2023. Greater reductions in weight were seen in the group with diabetes.

All told, nearly 82% of patients taking Mounjaro lost at least 5% of their weight within a year, compared to around 67% of the Ozempic group.

A similar pattern was seen at higher weight reduction thresholds, with the proportion of patients achieving a 10% or greater reduction coming in at 62% and 37%, respectively, and 42% and 18% for 15% or more.

The researchers behind the study write in JAMA Internal Medicine that they believe this is the first comparative effectiveness study of tirzepatide and semaglutide in adults with obesity or who are overweight, but point out that the relative weight-loss results are fairly consistent to what has been seen in clinical trials of the two drugs.

They acknowledge the limitations of observational studies in giving a reliable answer to clinical comparisons, but point to the size of the study, consistent results across different subgroups, and the inclusion of people unlikely to be studied in clinical trials because of accompanying conditions like major depressive disorder (MDD), which was recorded in the EHR of nearly a quarter (22%) of the cohort.

Lilly is running a head-to-head trial comparing tirzepatide to semaglutide in non-diabetic patients with obesity or who are overweight – called SURMOUNT-5 – with a readout expected later this year.

The significance of a difference in weight-loss efficacy is hard to gauge, even if it is confirmed in Lilly’s comparative trial, given that Ozempic and Wegovy have found their way into everyday parlance as brands used for weight loss – much in the same way as Prozac became associated with antidepressants and Viagra with erectile dysfunction treatments back in the day.

Novo Nordisk has also been faster out of the blocks when it comes to adding to the label of its semaglutide therapies, with cardiovascular risk reduction in people who are overweight with underlying risk factors already on semaglutide’s label and a filing in chronic kidney disease due shortly, based on the FLOW trial results.

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