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Is SURMOUNT-3 a fair comparison of tirzepatide against its comparator arm?

Asked 15 Mar 2026Modified 4 months agoViewed 5.9k times
This question was marked as a duplicate of Is STEP 1 a fair comparison of a GLP-1 receptor agonist against its comparator arm?Closed 1 Apr 2026. It remains here because the answers below are specific to how it was asked.
20

For reference: SURMOUNT-3 · tirzepatide.

I would like to know whether this claim survives contact with evidence.

If the answer is "nobody has tested that", I would like that stated so I can stop looking.

How well supported is this claim?

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askedsasha_ferreira9.4k1515 Mar 2026

1 Answer

Accepted answer first, then by votes
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Accepted answer

Fair depends on the comparator arm, and in SURMOUNT-3 that means asking whether the comparator was titrated to the same ambition as the experimental one. A head-to-head that runs its comparator to a dose below the one it is licensed at is not measuring the two agents, it is measuring one agent against a handicapped version of the other. Check three things: the maximum comparator dose reached, the proportion of the comparator arm that reached it, and whether the titration schedules had the same duration. If those match, the comparison is fair on dosing and the argument moves to the endpoint. If they do not, the effect size is partly an artefact of the protocol.

This is answerable from the published record, but only if you take the placebo arm seriously rather than reading the active arm alone.

Trial populations are selected. Exclusion criteria in this class routinely remove people with significant renal impairment, prior pancreatitis and unstable psychiatric illness, which is exactly the population the results are then quoted for.

Relative to absolute, worked

QuantityValueDerivation
Control-arm event rate8.0 %From the trial table, not the abstract
Hazard ratio0.80Reported
Treated event rate6.4 %8.0 × 0.80
Absolute risk reduction1.6 pp8.0 − 6.4
Number needed to treat631 ÷ 0.016
Relative risk reduction20 %1 − 0.80

The last two rows describe the same finding. Only one of them is used in headlines.

Open-label extensions are not the same evidence as the randomised phase. Once everyone knows what they are taking, the reported outcomes acquire a bias that no analysis fully removes.

The cardiovascular outcome programme in this class runs to several large randomised trials — LEADER for liraglutide, SUSTAIN-6 and SELECT for semaglutide, REWIND for dulaglutide — and they are the reason the class is discussed as more than a weight intervention.

Read the protocol and the statistical analysis plan if the result matters to you. Both are usually published alongside.

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answered · acceptedcoring_risk27k2719 Mar 2026
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Ask PeptideStack is a static archive. Posting is closed, but the norms are worth stating: answer the question that was asked, show your working, cite the trial or the certificate, and say plainly where the evidence runs out.

Not medical advice. Research-use-only compounds are not approved for human use.