Glossary · Methodology
Primary endpoint
In short
The primary endpoint is the one question that a study registers in advance as its main question. If a study misses it, the study is negative — even if something positive shows up elsewhere.
Before the first participant is enrolled, a study team specifies how success will be measured: by one number, at a specific point in time, in a specific group. This specification is filed in a registry and cannot be changed afterwards. That is exactly what makes it valuable — it prevents anyone from searching afterwards for the slice that looks best.
Everything else a study measures is secondary endpoints and subgroups. These may be reported, and they are often interesting. But they do not carry proof of efficacy, because when enough values are measured, something striking will always turn up purely by arithmetic.
That is why our fact checks often contain a sentence like: “The primary endpoint was missed.” That is not a minor detail on the side — that is the result.
A positive incidental finding in a negative study is a hypothesis, not proof.
Where this comes up in the fact checks
- LL-37 – The main endpoint of the wound-healing study was missed; only a subgroup was positive.
- SS-31 (Elamipretide) – The approval decision was made despite the missed primary endpoint of the main study.
- AOD-9604 – The most frequently cited phase 2b study was never published in a scientific journal.
Related terms: Surrogate marker · Relative and absolute effect
Information only, not medical advice. The BK-Score is a subjective assessment according to disclosed rules – not a scientific evaluation. Scoring rules