Primary Endpoint — What It Means in Clinical Trials

Plain English Definition

The primary endpoint is the main outcome measure that a trial is specifically designed and powered to evaluate. It is the single most important question the trial must answer. The trial's success or failure is judged primarily on this endpoint. Regulatory agencies base their approval decisions largely on whether the primary endpoint is met.

Why It Matters

The primary endpoint tells you what the researchers consider most important. If the primary endpoint is "progression-free survival," the trial is primarily asking: does this drug keep the disease from getting worse for longer?

Example