In the battle of weight loss drugs, international researchers have found that tirzepatide – commonly sold under the names Mounjaro or Zepbound – does a better job of cutting the kilos than semaglutide among overweight and obese people.
The researchers investigated the effects of close to 20,000 people taking either drug and while most of them went on to lose 5% or more of their weight, the effects were greater for tirzepatide: those receiving tirzepatide were more likely to achieve 5% or greater, 10% or greater, and 15% or greater weight loss and experienced larger reductions in body weight at three, six, and 12 months.
Lead author, Dr Nicholas Stucky from the Portland Center for Cardiovascular Analytics, Research and Data Science, said that to their knowledge, this was the first clinical comparative effectiveness study of tirzepatide and semaglutide in adults who were overweight or obese.
“Data from head-to-head trials comparing these therapies in patients with overweight or obesity are not yet available. Further, it remained unclear whether the magnitude of weight loss in clinical settings mirrored that in RCTs, given well-described differences between these populations,” he said.
“Finally, because these medications are costly and insurance coverage is limited for patients without T2D, actual adherence may differ from clinical trials, potentially attenuating the treatment effect.”
The study took place between May 1, 2022 (the month of tirzepatide approval) and September 30, 2023, and relied on the brand as a proxy for target dose: 0.5 mg for semaglutide labelled for T2D and 5.0 mg for tirzepatide (labelled exclusively for T2D at the time of this analysis).
The standard dose escalation schedule for both drugs was four weeks and the baseline weight was similar between groups (tirzepatide: 110kg; semaglutide: 109kg).
The mean on-treatment change in bodyweight was −5.9% for tirzepatide vs −3.6% for semaglutide at three months, −10.1% vs −5.8% at six months, and −15.3% vs −8.3% at 12 months; and after adjusting for residual confounding, the absolute difference in weight loss between tirzepatide and semaglutide was −2.4%, −4.3%, and −6.9% at three, six-, and 12-months receiving treatment, respectively.
“While data from head-to head trials has been more limited, a single study that evaluated the glucose-lowering effect of tirzepatide (5 mg per week) compared with semaglutide (1 mg per week) in patients with T2D also found that 5% weight loss was achieved by 69% and 58%, respectively,” Dr Ng said.
“Importantly, a trial comparing tirzepatide to semaglutide in patients with overweight or obesity, but without T2D is underway (SURMOUNT-5, NCT05822830). The results, however, are not expected until late 2024.”