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expert reaction to study looking at giving the drug tirzepatide once weekly as a treatment for obesity

A study published on Saturday in the New England Journal of Medicine (NEJM) looks at the use of tirzepatide once weekly for the treatment of obesity.


Dr Adam Jacobs, Senior Director of Biostatistics at Premier Research, said:

“This seems to be a well conducted study and I see no obvious problems with their conclusions that tirzepatide is effective as a treatment for obesity over a period of 72 weeks.

“The biggest limitation is that 72 weeks is not a very long time in this context.  Obesity is something that affects people for years or decades, and we don’t know if those who lost weight during trial will maintain that weight loss in the longer term.

“It’s also worth noting that although the treatment seemed relatively safe, it was not without side effects.  For a small, but not negligible, number of patients (6-7% in the 2 higher dose groups), they were serious enough that patients stopped taking the drug because of them.  Over 30% of patients in the 2 highest dose groups experienced at least some nausea, and over 20% experienced at least some diarrhoea, though the authors state that these were mostly transient.

“One final thought is that the paper notes that the trial was conducted almost entirely during the covid-19 pandemic.  Running clinical trials in a pandemic is not easy, and the triallists deserve credit for getting the trial done to a high standard in such difficult circumstances.”


Prof Sir Stephen O’Rahilly, Professor of Clinical Biochemistry and Medicine, and Director of the Medical Research Council Metabolic Diseases Unit, University of Cambridge, said:

“The results of this trial are very impressive.  Treatment of people with obesity with a weekly injection of tirzepatide produced weight loss similar to that seen with weight loss surgery.  Side effects were mild to moderate and generally related to some nausea and vomiting.  These adverse effects reduced in severity over the time of the trial.  Blood test showed improvements in all the markers of metabolic and cardiovascular health.

“This study, and recent similar reports of a related agent semaglutide, provide secure evidence that people with obesity can be effectively and safely treated using a medication based on the modification of naturally occurring hormones.

“About 40 years ago we started to understand how hormonal signals coming from the body could respond to our nutritional state and act on the brain to influence appetite and satiety.  This field has continued to make rapid progress.  These new drugs are a striking example of how the development of safe and effective therapies for important diseases are often based on decades of meticulous, basic scientific research.”



‘Tirzepatide once weekly for the treatment of obesity’ by Ania M. Jastreboff et al. was published in the New England Journal of Medicine on Saturday 4 June 2022.

DOI: 10.1056/NEJMoa2206038



Declared interests

Prof Sir Stephen O’Rahilly is remunerated for advice to several pharmaceutical companies in the area of drug development for obesity and metabolic disease.  These companies do not currently include the manufactures of either tirzepatide or semaglutide.

No others received.

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