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Is SOUL a fair comparison of oral semaglutide against its comparator arm?

Asked 21 Jun 2025Modified 10 months agoViewed 22k times
21

The particulars: SOUL · oral semaglutide.

The claim is plausible, which is exactly why I want to check it.

I am able to read a paper if someone points me at one.

Is there data behind this, or is it received wisdom?

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AN
askedamara_nwachukwu20k2721 Jun 2025
6Can you link the publication rather than the summary? The summary usually drops the interval. – swab_stopper 10 months ago
5Is this the randomised phase or the open-label extension? – u100_marks 8 months ago
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4 Answers

Accepted answer first, then by votes
112

Accepted answer

The honest answer here is that the published evidence supports part of the claim and is silent on the rest, and it is worth being precise about which part is which.

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.

Headline results, principal programmes

TrialAgentnDurationPrimary result
STEP 1Semaglutide 2.4 mg1,96168 wk−14.9 % vs −2.4 % weight
STEP 2Semaglutide 2.4 mg, T2DM1,21068 wk−9.6 % vs −3.4 % weight
SURMOUNT-1Tirzepatide 5/10/15 mg2,53972 wk−15 / −19 / −21 % weight
SURMOUNT-4Tirzepatide, withdrawal67088 wkContinued loss vs substantial regain
SELECTSemaglutide 2.4 mg17,604~40 moMACE HR 0.80 (0.72–0.90)
FLOWSemaglutide 1.0 mg, CKD3,533~3.4 yrRenal composite reduced; stopped early
SURMOUNT-OSATirzepatide, OSA46952 wkAHI reduced with and without PAP

Put another way, 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.

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

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

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

edited 4 Sept 2025 by Dr_Ilse_Vandenberg — added a caveat about sampling

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DV
answered · acceptedDr_Ilse_Vandenberg113k2484 Sept 2025
8Which population was that figure from? It moves a lot between the trials. – t_oyelaran 2 months ago
7Good answer, but the confidence interval in the cited trial is wider than implied. – birk_nordahl 19 days ago
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43

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.

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.

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 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.

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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CR
answeredcoring_risk27k2715 Sept 2025
5The number needed to treat is the framing that finally made this concrete for me. – mala_venkatesh 5 months ago
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32

On the detail: 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.

Worth being precise here: 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.

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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DL
answeredDr_Otto_Lindqvist72k5812 Aug 2025
25

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.

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.

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.

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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DA
answeredDr_Rosalind_Achebe69k14724 Aug 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.