Phase 2 trial sample size typically ranges from:

• A. 100-300
• B. 20-80
• C. 1000-3000
• D. 400-800

Answer: (A)

Phase 2 trials aim to confirm whether a treatment shows signals of efficacy while further assessing safety in a broader group than Phase 1. To do this effectively, you need enough participants to reasonably detect treatment effects and common adverse events, but not so many that the study becomes impractical or unnecessarily costly.

The typical size is in the low hundreds. This provides enough statistical power to observe a treatment effect and characterize safety profiles across a somewhat diverse patient population, without committing to the large numbers required for definitive proof of benefit.

Smaller Phase 1 studies (tens of participants) focus on safety and dosing, not efficacy. Very large Phase 3 trials involve thousands of participants to confirm efficacy and monitor rare side effects in a broad population. So the most appropriate match for Phase 2 is enrollments in the hundreds, not just tens or thousands.