Peptide basics
Six fields on a trial record tell you almost everything
On this page
Every registered trial record has the same structure, so learning it once works for all of them.
The six fields that matter most are phase, allocation, masking, eligibility, enrolment and primary outcome.
Together they tell you how far development had progressed, whether the comparison was fair, who was studied, how many, and what question was asked.
Reading them takes a couple of minutes and prevents most of the common mistakes people make with trial claims.
This page is a guide to reading trial registry records. It explains terminology and uses real records as examples. It does not evaluate any compound and contains no dose, schedule or route.
1. Phase
Phase tells you how far the compound had travelled when this trial ran. Phase 1 is first-in-human safety, phase 2 looks for signs of an effect, phase 3 tests it at scale, and phase 4 happens after approval — which means only an approved product can be in one.4
2. Allocation
Randomised means participants were assigned to groups by chance. That is what makes the groups comparable, and its absence is the single biggest weakness a comparative trial can have. STEP 1 and SELECT are both randomised.234
3. Masking
Masking records who was kept unaware of the assignment. STEP 1 is quadruple-masked: participant, care provider, investigator and outcomes assessor. SURMOUNT-1 is double. Weight and symptom outcomes are especially sensitive to knowing which group you are in.24
4. Eligibility
This is the field people skip and the one that most often changes the meaning of a result. STEP 1 required a BMI of 30 or above, or 27 with a weight-related condition, and set a minimum age of 18. SELECT required a BMI of 27 or above plus established cardiovascular disease, and a minimum age of 45.23
Same compound, two trials, two populations that barely overlap. A result from either one describes the people who could enter it and nobody else.23
5. Enrolment
How many took part, and whether the figure is actual or estimated. STEP 1 posts 1,961 actual; SELECT posts 17,604 actual. Larger trials give more precise estimates and can detect rarer events, which is why outcome trials are so large.23
6. Primary outcome
The one measure the trial was designed and powered to answer, declared before enrolment. Everything else in the record is secondary or exploratory, and secondary findings are far weaker evidence than they look when quoted alone.14
Common questions
What does quadruple masking actually mean?
Four roles were kept unaware of group assignment: participant, care provider, investigator and outcomes assessor. More masking reduces the ways expectation can influence a result.
Is a bigger trial always better?
More precise, not automatically better. A very large trial in a narrow population answers a narrow question extremely precisely.
What if there is no results section?
Many trials publish in journals rather than posting to the registry, and posting deadlines vary. The absence of posted results is not the absence of results.
Sources
- RegulatoryClinicalTrials.gov — learn about studiesU.S. National Library of Medicine, 2026clinicaltrials.gov/study-basics/learn-about-studies ↗↩ Back to text
- Primary studySTEP 1 (NCT03548935) — design, eligibility and baseline dataClinicalTrials.gov, U.S. National Library of Medicine, 2021clinicaltrials.gov/study/NCT03548935 ↗↩ Back to text
- Primary studySELECT (NCT03574597) — design, eligibility and baseline dataClinicalTrials.gov, U.S. National Library of Medicine, 2023clinicaltrials.gov/study/NCT03574597 ↗↩ Back to text
- RegulatoryClinicalTrials.gov — glossary of common study termsU.S. National Library of Medicine, 2026clinicaltrials.gov/study-basics/glossary ↗↩ Back to text