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What did the placebo arm of SURMOUNT-2 report for injection-site erythema?

Asked 27 Apr 2026Modified 22 days agoViewed 5.5k times
18

What I am working with: SURMOUNT-2 · injection-site erythema.

I would like help reading this properly rather than being told what conclusion to reach.

I have the full report including the method section, so I can quote specifics if that helps.

What can I legitimately conclude from this figure?

clinical-trials
clinical-trials

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injection-site-reaction
injection-site-reaction

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DK
askedDr_Tomas_Kral53k3827 Apr 2026

5 Answers

Accepted answer first, then by votes
-3

Accepted answer

The SURMOUNT-2 placebo arm is the only thing that makes its treatment arm interpretable, and it is the row nobody quotes. Symptoms reported under placebo in these programmes are not rare, because the population is being asked about them weekly and would have had some of them regardless. The attributable figure is the treated rate minus the placebo rate, and that difference is routinely a fraction of the headline. Two cautions on the subtraction: the arms must have been assessed the same way, and a discontinuation for an event removes that participant from later time points in both arms, which flatters whichever arm loses more people.

The part that matters: a trial establishes what happened to a defined group under a defined protocol. Extending it beyond that group is inference, and inference is allowed as long as it is labelled.

Non-inferiority and superiority designs are not interchangeable. A non-inferiority result says the new agent is not meaningfully worse against a pre-specified margin — it does not say it is as good, and it certainly does not say it is better.

Intention-to-treat and per-protocol analyses answer different questions. ITT asks what happens if you offer the treatment; per-protocol asks what happens if it is taken as directed. The gap between the two is a measure of how tolerable the protocol was.

Registry entries at ClinicalTrials.gov carry the pre-specified primary endpoint with a timestamp, which is the cheapest available check on whether an endpoint was changed after the data were seen.

The short version: check the endpoint, check the comparator, check who was excluded, then look at the number.

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RS
answered · acceptedrota_site36k2725 Jun 2026
6Same experience here, different supplier. – tobias_reint 25 days ago
7Is the open-label extension included in that figure, or just the randomised phase? – Dr_Aoife_Brennan 2 months ago
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25

Look at the discontinuation rate alongside the efficacy figure. A large effect in the two thirds who stayed is a different result from a large effect in everyone.

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.

Confidence intervals matter more than point estimates when two trials disagree. Two studies reporting fifteen and twenty per cent whose intervals overlap heavily have not disagreed about anything.

Meta-analyses in this area are dominated by whichever trial contributed the most participants, so read the forest plot rather than the summary estimate.

One qualification: absence of a signal in a trial of this size is not evidence of absence for a rare event. It is evidence that the event is rarer than the trial could detect.

Quote the interval alongside the estimate and half the disagreements on this site would not start.

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DW
answereddeamidation_watch45k585 Jul 2026
5Which population was that figure from? It moves a lot between the trials. – cal_hennessy 4 months ago
4Adding that the endpoint definition differs between the two trials being compared here. – Dr_Bram_Verhoeven 2 months ago
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16

Stated carefully, the trial answers a narrower question than the headline suggests, and the narrowing is where the useful information is.

A composite endpoint is only as informative as its least serious component. Where a cardiovascular composite combines death, infarction and stroke, ask which component moved, because they are not interchangeable outcomes.

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.

The caveat is that trial evidence is about licensed product administered under supervision. None of it transfers automatically to research-grade material of unverified content.

If a claim cannot be traced to a named trial with a named endpoint, treat it as a claim rather than as evidence.

edited 8 Jul 2026 by eoin_mcgarry — tightened the wording; no substantive change

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EM
answeredeoin_mcgarry18k3830 Jun 2026
8Do you have a reference for the last claim? Not disputing it, just want to read it. – Dr_Otto_Lindqvist 6 months ago
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10

Answer first: read the primary endpoint, the comparator and the population before you read the effect size. Almost every argument on this site about a trial is really an argument about one of those three.

Placebo arms in this class are not nothing. Lifestyle-intervention placebo arms in the major obesity trials commonly lose two to three per cent of body weight, so an active-arm figure quoted without its comparator overstates the drug effect by roughly that much.

Where a result is quoted from a conference abstract rather than a peer-reviewed publication, the numbers routinely move between the two. It is worth checking which one you are reading.

I am not a clinician and this is not medical advice; it is a reading of a published protocol.

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

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DV
answeredDr_Ilse_Vandenberg113k24820 Jun 2026
7

Before comparing two trials, check whether they share an endpoint definition. Frequently they do not, and the numbers then are not comparable in any sense.

Duration decides what can be seen. A 68-week trial can measure weight and glycaemia; it cannot measure anything whose event rate is one per cent per year without enrolling tens of thousands.

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.

Be careful about generalising from a trial population to yourself. The exclusion criteria are usually the most informative page in the supplement.

When two sources disagree, the answer is almost always in the methods section of the one you have not read.

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RS
answeredrota_site36k2715 Jun 2026

Your answer

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.