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Is SELECT a fair comparison of a GLP-1 receptor agonist against its comparator arm?

Asked 29 Dec 2024Modified 16 months agoViewed 15k times
10

Stated plainly: SELECT · a GLP-1 receptor agonist.

This has the shape of a fact but I cannot find its origin.

What I found instead were three secondary sources all citing each other.

Has anyone verified this independently?

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UM
askedunit_math6.2k1529 Dec 2024
7Worth saying whether you want relative or absolute risk. They read very differently. – dead_volume 5 months ago
6Same question, and the two papers I found disagree, which is why I am watching. – swirl_dont_shake 3 months ago
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5 Answers

Accepted answer first, then by votes
79

Accepted answer

The relevant detail is that the trial answers a narrower question than the headline suggests, and the narrowing is where the useful information is.

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.

Mechanically, 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.

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.

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

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

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TH
answered · acceptedthreadlock719k2822 Mar 2025
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70

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.

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.

The part that matters: 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.

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

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

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DK
answeredDr_Tomas_Kral53k3811 Mar 2025
5Worth flagging that this changed with the 2025 publication, so older answers are out of date. – kwn_analytical 7 months ago
6This matches what I was told by a clinician, for whatever that is worth. – ruaidhri_o_shea 9 months ago
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37

The short version: the effect is real, the magnitude depends on the population, and the population is usually the part that gets dropped when a result is quoted second-hand.

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.

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.

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.

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

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JE
answeredjuan_esquivel14k162 Apr 2025
29

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.

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.

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.

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

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TQ
answeredtriple_agonist_q57k3814 Apr 2025
26

To be exact about it, 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.

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.

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.

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DK
answeredDr_Sara_Kuusela28k3726 Jan 2025

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.