What does PIONEER-1 tell me about constipation at the 7 mg dose?

Details up front: PIONEER-1 · constipation · 7 mg.

This is presented as though it settles something, and I am not convinced it does.

I have two documents that appear to disagree, which is what prompted this.

Which parts of this are informative and which are decoration?

Only what the 7 mg arm reported, and the denominator is that arm rather than the trial. Adverse-event tables are published per arm, so the 7 mg incidence of constipation has its own numerator and its own denominator, and pooling it with the other arms produces a figure that describes nobody. Two further deductions before you use it. Subtract the placebo arm — constipation occurs in people who received nothing, and the difference is the part attributable to the drug. And check whether PIONEER-1 counted events or counted participants: one participant with six episodes is one row in a participant count and six in an event count, and the two get quoted interchangeably. Nothing here is medical advice.

Start with what the trial was powered for. Everything else in the publication is secondary, exploratory, or a subgroup, and those three words mean three different things.

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 relevant detail is that 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.

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

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

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.

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.

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

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

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.

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.

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.

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.

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

edited 13 Aug 2026 by sunniva_dahl — corrected a unit error in the worked example

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.

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.

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.

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