Was REDEFINE 4 randomised?

Yes — randomised but open-label. Its registry record lists allocation as randomised and masking as none.

Why does blinding matter more for weight than for other endpoints?

Weight responds to behaviour, and knowing your assignment can change adherence, persistence through side effects and reporting.

Does open-label mean the trial is unreliable?

No. It is a real limitation that weakens the comparison, and blinding two different injectables is genuinely difficult.

GLP-1 & Incretin Science

What Open-Label Does to a Weight-Loss Trial

JMWritten & reviewed by Jack Muncaster · Founder, UK PeptidesLast reviewed 2026-08-233 cited sources

REDEFINE 4 was randomised but open-label — its ClinicalTrials.gov record lists masking as none. Knowing which drug you received can influence adherence, behaviour and adverse event reporting, which matters more for a behaviourally sensitive outcome like body weight than for a hard endpoint.

Key facts

REDEFINE 4 allocation: Randomised
REDEFINE 4 masking: None — open-label
Registration: NCT06131437
Randomisation protects: Comparability at baseline
Blinding protects: What happens afterwards
Most vulnerable outcomes: Behaviourally influenced ones

Two different protections

Randomisation and blinding do different jobs and are frequently confused. Randomisation makes groups comparable at the start by distributing known and unknown differences by chance. Blinding protects what happens after that — how participants behave, how investigators assess, how adverse events get reported. A trial can have one without the other, and REDEFINE 4 did.

Why weight is a vulnerable endpoint

Body weight responds to behaviour. A participant who knows they received the drug they hoped for may adhere differently, eat differently, or persist through early side effects that would otherwise have caused them to stop. None of that requires anyone to act in bad faith — it is ordinary human response to information, and blinding exists precisely to remove it.

Research material referenced

Retatrutide 10mg — third-party HPLC tested

View — £59.99

Where it shows up in the numbers

Most visibly in discontinuation, which then propagates into the treatment-policy estimand. If knowledge of assignment affects who stops and when, it affects the estimand that counts everyone regardless of adherence. That is one plausible contributor to the gap between REDEFINE 4's two reported estimands, though a gap would exist in a blinded trial too.

Why it is sometimes unavoidable

Blinding two injectables with different administration schedules, devices and side-effect profiles is genuinely difficult. Participants often work out their assignment from the experience regardless of packaging. Running open-label is frequently a practical decision rather than a careless one — which is a reason to note the limitation, not to dismiss the trial.

The pattern across recent incretin evidence

REDEFINE 4 was open-label. The survodutide dose-response trial in Diabetologia carried an open-label semaglutide arm. Where a comparator is unblinded, the comparison is weaker than a fully blinded one, and that qualification belongs beside the numbers rather than in a limitations paragraph nobody reads.

How to check

The ClinicalTrials.gov record states allocation and masking directly. For NCT06131437 it reads randomised, masking none. It takes seconds and it is more reliable than a press release, which will rarely lead with the design limitation.

Extended research context

The GLP-1 & Incretin Science deep dive

Deep dive: the two routes to a bigger effect

Every compound trying to beat GLP-1 alone has taken one of two routes. The first adds more receptors from the same hormone family — GIP in tirzepatide, GIP and glucagon in retatrutide. The second adds a non-incretin satiety hormone, which in practice means amylin: CagriSema combines cagrilintide with semaglutide, and amycretin engages both receptors from one molecule. Both routes work, because they recruit signalling pathways that do not fully overlap. Neither has escaped the constraint that binds all of them, which is that gastrointestinal tolerability worsens as effect size grows.

Deep dive: why a percentage is not a result

The most-quoted numbers in this field are the least comparable. REDEFINE 1 reported 22.7% and 20.4% for the same compound in the same trial — the first among participants who adhered to treatment, the second across everyone randomised. TRIUMPH-1 reported 28.3% in an uncomplicated obesity population while TRIUMPH-3 reported up to 22.6% in adults with established cardiovascular disease, using the same compound. Before any two figures can be compared they have to match on estimand, population, duration, comparator and whether the number is placebo-adjusted. Most published comparisons match on none of them.

Deep dive: what happens after the trial stops

Every headline figure describes weight while treatment continues. The STEP-1 extension found that a year after semaglutide was stopped, participants had given back roughly two-thirds of what they lost, moving from 17.3% mean reduction to a net 5.6% — though average weight remained below baseline and nearly half stayed at least 5% down. Meta-analysis puts regain at around 0.8 kg per month. This is why maintenance studies such as TRIUMPH-6 matter more to the field's future than another two points of peak reduction.

Research applications

▸Comparing incretin and amylin compounds on a like-for-like basis
▸Interpreting estimands, thresholds and placebo-adjusted figures in trial reports
▸Tracking the obesity pipeline across sponsors and jurisdictions
▸Understanding receptor pharmacology behind GLP-1, GIP, glucagon and amylin
▸Distinguishing licensed medicines from investigational compounds

Handling checklist

✓Identify which estimand a quoted percentage comes from before citing it
✓Check the trial population and baseline BMI against the comparison you are making
✓Confirm the duration and whether the reduction curve had plateaued
✓Read discontinuation rates alongside efficacy figures
✓Verify every NCT identifier against ClinicalTrials.gov rather than secondary reporting

Common research-handling mistakes

Learnt from thousands of researcher orders across our UK labs.

✗ Comparing headline percentages across different trials

Fix: Population, duration, estimand and comparator all differ; the numbers are not interchangeable.

✗ Quoting the larger of two figures from the same trial

Fix: Name the estimand. Efficacy and treatment-policy answer different questions.

✗ Treating peak reduction as a durable outcome

Fix: Substantial regain follows cessation across the class; peak figures describe a maintained state.

✗ Assuming an oral route means a weaker mechanism

Fix: Route and receptor count are independent. Orforglipron is weaker because it hits one receptor, not because it is a tablet.

✗ Reading investigational compounds as available treatments

Fix: Most of this pipeline holds no authorisation anywhere; mazdutide is approved only in China.

Continue researching

Peer-reviewed guides, comparators and matched reference materials.

Frequently asked questions

Was REDEFINE 4 randomised?: Yes — randomised but open-label. Its registry record lists allocation as randomised and masking as none.
Why does blinding matter more for weight than for other endpoints?: Weight responds to behaviour, and knowing your assignment can change adherence, persistence through side effects and reporting.
Does open-label mean the trial is unreliable?: No. It is a real limitation that weakens the comparison, and blinding two different injectables is genuinely difficult.

Primary sources & clinical trials

Peer-reviewed research and registered trials from PubMed, ClinicalTrials.gov, PubChem, FDA and NIH. All links open in a new tab and point to the primary source, so every claim can be verified at origin.

Written and reviewed by

Jack Muncaster · Founder, UK Peptides

Jack founded UK Peptides in Manchester after repeatedly receiving research compounds with missing or recycled paperwork. He is responsible for supplier selection, batch release decisions and the content published in this research library. Every article here is sourced to primary literature and every product page to a signed third-party certificate.

How we write and check this content Report a factual error in this article

More GLP-1 & Incretin Science articles

Popular across the research hub

One flagship guide from every other research category — keep exploring.

← Back to Forum