Phase 3 trials enroll approximately how many volunteers with the disease or condition?

• A. 10-100 volunteers
• B. 300-3,000 volunteers with the disease/condition
• C. 5,000-10,000 volunteers
• D. 50-100 volunteers

Answer: (B)

Phase III trials aim to confirm how well a drug works and how safe it is in a larger, more diverse group of patients who have the disease or condition. To achieve reliable statistical power and to detect less common adverse effects, these studies enroll hundreds to thousands of participants. The typical range for Phase III is about 300 to 3,000 participants with the disease, which balances the need for broad representation with practical trial size. Smaller enrollments are characteristic of Phase I or early Phase II studies, while enrollments well beyond several thousand are less common for standard Phase III designs, though there can be exceptions.