Extravagant Wegovy Claims with Limited Evidence at ESC
It is eye-popping really. Novo Nordisk issued a press release from the European Society of Cardiology (ESC) Congress over the weekend, with extravagant claims for Wegovy versus tirzepatide. Specifically, the claim was that “Wegovy cuts risk of heart attack, stroke or death by 57% compared to tirzepatide.”
This is quite an amazing claim to make. The only trouble is that the evidence to back it up has some pretty severe limitations. Honestly, it appears to be more of an exercise in salesmanship than science.
Claiming Causality
First and foremost is the issue with claiming causality based upon a retrospective observational study of electronic patient records. In the fine print of their press release, Novo Nordisk says it plainly enough. “While associations can be demonstrated, causal relationships cannot be definitively established” with such a study.
But the headline makes a pretty strong claim of causality: “Wegovy cuts the risk.”
Limited Follow-Up
Another obvious thing to note is that the follow-up on the patients in this study is extremely limited. For the per-protocol analysis that yields the 57% reduction claim, the mean is only four months. Contrast that with more than three years of follow-up in the SELECT RCT that gave Wegovy its impressive claim of a 20% reduction in strokes, heart attacks, and deaths.
Inconsistency with Prior Evidence
But perhaps what gives us the greatest trouble is the 57% reduction claim itself, because on its face, it seems inconsistent with prior evidence. In the very carefully conducted SELECT study, semaglutide yielded a 20% reduction in stroke, heart attack, and death – compared to placebo. How can it be that semaglutide yields a too-good-to-be-true 57% reduction when compared to a highly effective drug like tirzepatide? It strains credibility.
On top of that, other observational studies (e.g., Anson et al and Dani et al) have reported good outcomes for major adverse cardiovascular events with tirzepatide in comparison to semaglutide.
Credibility
Straining credibility is not really a good idea for such a fine research organization as Novo Nordisk. Semaglutide is clearly the only obesity medicine with a strong claim for preventing heart attacks, strokes, and deaths. Lilly is working on such a claim for tirzepatide with the SURMOUNT-MMO study, which is well underway. But Novo clearly has the advantage for now.
The extravagant claims in this study, coming from Novo’s Evidence Generation unit, without involving any independent experts, are not very persuasive.
Click here for the press release and here for the slides presented at the meeting. For press coverage, click here and here.
An Extravagant Stroll Along the Seashore, painting by Joaquín Sorolla / Wikimedia Commons
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September 2, 2025
September 02, 2025 at 8:14 am, JenCan said:
They also didn’t have a non-treated/control group, so it’s actually possible both medications produced positive improvements, though Wegovy’s may have been more significant. Without a control group, you can’t make the argument that Wegovy was alone in reducing MACE/all-cause mortality.
AND there’s no mention of the studied tirzepatide doses. They clearly say they studied semaglutide 2.4mg but the dosages of tirzepatide are mysteriously absent in their press release.
September 03, 2025 at 5:32 am, Michael Toft said:
Interesting critique, but it drifts into oversimplification. Calling a 57% reduction “too-good-to-be-true” is editorial, not evidence – it’s simply what the data showed. And implying that “a highly effective drug like tirzepatide” must deliver CV benefit because it drives weight loss overlooks the possibility that these effects are molecule-specific to semaglutide, as the study itself concludes. One might ask: are your conclusions grounded in evidence, or in intuition?
September 03, 2025 at 6:10 am, Ted said:
I confess that an observational study with short follow-up that is inconsistent with other research arouses suspicions that extravagant claims arising from it might be too good to be true.