These studies test new treatments, drugs, medical devices, or procedures. Participants are assigned specific interventions by the researcher, and their effects are measured. This is the most common type of clinical trial.

Observational

Researchers observe participants without intervening or altering their care. These studies track health outcomes in groups of people receiving different treatments as part of their normal care, without assigning specific interventions.

Expanded Access

These programs allow patients with serious or life-threatening conditions to access investigational treatments outside of clinical trials when no comparable alternatives exist. They're sometimes called "compassionate use" programs.

Trial Phases Explained

Early Phase 1

Initial studies to determine safety, dosage range, and side effects in a very small number of participants. Sometimes called "Phase 0" trials.

Phase 1

Tests a new treatment in a small group (20–80 people) to evaluate safety, determine safe dosage ranges, and identify side effects.

Phase 2

Treatment given to a larger group (100–300 people) to see if it's effective and to further evaluate its safety.

Phase 3

Treatment given to large groups (1,000–3,000 people) to confirm effectiveness, monitor side effects, compare to commonly used treatments, and collect information for safe usage.

Phase 4

Post-marketing studies after a treatment has been approved for use, providing additional information about risks, benefits, and optimal use.

Other / Not Applicable

Trials that don't fit into standard phase categories, including observational studies that don't test interventions or expanded access programs.

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