Evidence guide
How Clinical Trials Work
Clinical development moves from early safety and dosing to larger tests of benefit, harms and comparative value.
Phases are not grades
Phase 1 usually emphasizes safety and dose, phase 2 looks for activity and refines design, and phase 3 tests benefit and harms in larger populations. Phase 4 continues after approval.
Endpoints matter
A biomarker can change without improving how people feel, function or survive. Surrogate outcomes need independent validation.
Registration protects the question
Public trial registration and a prespecified protocol reduce the temptation to promote whichever result looked best after the data were seen.
A practical reading checklist
- Which phase is it?
- What was the primary endpoint?
- Was it registered before enrollment?
- Who funded and controlled the data?