Endpoint
Definition
A measurable outcome in a clinical trial used to evaluate whether a treatment is effective. Primary endpoints are the main results a trial is designed to assess; secondary endpoints provide additional evidence of benefit.
Endpoint
In clinical research, an endpoint is a predefined, measurable outcome that is used to determine whether an investigational treatment produces a meaningful effect. Endpoints are specified in the trial protocol before the study begins and form the basis for statistical analysis. The choice of endpoints directly shapes trial design, sample size, and the conclusions that can be drawn from the results.
Endpoints are categorized as primary and secondary. The primary endpoint is the single most important outcome that the trial is statistically powered to detect; it drives the sample size calculation and is the basis for regulatory decision-making. In obesity trials, the primary endpoint is typically the percentage change in body weight from baseline, or the proportion of participants achieving a clinically meaningful weight loss threshold (such as 5% or 10%). In diabetes trials, the primary endpoint is usually the change in HbA1c from baseline. Secondary endpoints provide supplementary information about additional benefits or risks, such as changes in waist circumference, blood pressure, lipid levels, or liver fat content.
In the Phase 2 retatrutide obesity trial (NCT04881706), the primary endpoint was percentage change in body weight at 24 weeks, with a key secondary endpoint extending this assessment to 48 weeks. The trial also measured numerous secondary endpoints including the proportion of participants achieving various weight loss thresholds and changes in cardiometabolic risk factors.