What is an 'endpoint', and what does it mean when it is a surrogate?
Updated: 2026-09-09 · Safety and evidence
Short answer
The endpoint is the result a study measures to decide whether something worked. It can be clinical — something the person experiences — or surrogate: a lab or imaging marker used as a stand-in because it is faster to measure. A marker improving does not guarantee the outcome that matters improves.
In plain English
- Clinical endpoint: weight, a cardiovascular event, pain, mortality.
- Surrogate endpoint: a laboratory value or a technical measurement.
- Surrogates make trials shorter and cheaper, which is why they are common.
- There are historical cases where the marker improved and the clinical outcome did not.
What we know
- Regulators publish which markers they accept as surrogates and in what context.
- Many peptide studies use intermediate markers rather than clinical outcomes.
What we don't know yet
- For most research peptides there are no long-term clinical outcome data.
- You cannot assume an improving marker predicts real benefit.
Sources
External links to official sources or peer-reviewed studies.