Peptide basics

One compound, two trials: SELECT was 72% men, STEP 1 was 74% women

This page contains no dose, schedule or route, and makes no claim about what any compound does. It compares the enrolled populations of two trials of the same compound to show how much a roster depends on the question being asked.

The two tables, side by side

STEP 1's posted baseline characteristics record 1,453 female and 508 male participants out of 1,961 randomised, with a mean age of 46 years. Its inclusion criteria required an age of 18 or over.¹⁴

SELECT's posted baseline characteristics record 12,732 male and 4,872 female participants out of 17,604 randomised, with a mean age of 61.6 years. Its inclusion criteria required an age of 45 or over.²³

• Sex: 74.1% female in STEP 1; 72.3% male in SELECT.
• Mean age: 46 years in STEP 1; 61.6 years in SELECT.
• Minimum entry age: 18 in STEP 1; 45 in SELECT.
• Size: 1,961 randomised in STEP 1; 17,604 in SELECT.¹²

Same compound, same sponsor, overlapping years. The populations are close to inverted on sex and separated by more than fifteen years on mean age.¹²

The criteria that produced the difference

SELECT required established cardiovascular disease, evidenced by prior myocardial infarction, prior ischaemic or haemorrhagic stroke, or symptomatic peripheral arterial disease. That single criterion selects a population, and it selected this one.²

STEP 1 required a body-mass index at or above 30, or at or above 27 with a listed weight-related comorbidity, plus a history of at least one self-reported unsuccessful dietary effort to lose weight. No cardiovascular event was required.¹

Both trials excluded participants with a glycated haemoglobin at or above 48 mmol/mol (6.5%) at screening, so diabetes status does not explain the gap between them.¹²

The trial in the middle

STEP 2 studied people with type 2 diabetes and sits between the two extremes. It randomised 1,210 participants: 616 female and 594 male, with a mean age of 55 years.⁵

Three trials of one compound, three different populations, ordered by how much comorbidity the entry criteria required. That is a gradient, not noise.¹²⁵

Why this matters when reading a claim

Most claims about semaglutide are stated without naming the trial. If the claim is about weight, it almost certainly traces to a population that was three-quarters women in their forties. If it is about cardiovascular events, it traces to one that was almost three-quarters men in their sixties.¹²

Those are not interchangeable. A result established in one of those groups has not been established in the other, and neither trial was designed to bridge the gap.³⁴

The approved US labeling keeps them separate for the same reason, describing weight-management study results and cardiovascular outcome study results in distinct sections rather than merging them into one claim.⁶

Semaglutide is the only compound on this site with two very large trials in near-opposite populations. When a claim about it appears without a trial name attached, the first useful question is which of the two it came from.

Common questions