Association of Clinical Research Professionals (ACRP) Certified Professional Practice Exam

Which of the following is true regarding the comparison of Phase III and Phase IV trials?

1. Phase III has longer follow-ups

2. Phase IV usually has more subjects than Phase III

3. Phase III is also known as post-market

4. Phase IV trials are solely focused on new drugs

The correct answer is: Phase IV usually has more subjects than Phase III

Phase III trials are primarily designed to assess the efficacy and safety of a new treatment in a large patient population, which is typically the final stage of clinical trials before a drug can receive regulatory approval. These trials usually involve a significant number of subjects, often ranging in the thousands, in order to generate comprehensive data on how the treatment performs across diverse demographics and conditions. Phase IV trials, also known as post-marketing studies, take place after a drug has been approved and is available for use in the general population. They are often larger and can involve even more subjects compared to Phase III trials, as they seek to gather additional information on the drug's effects, optimal use, and long-term safety in a more real-world setting. This extensive data collection in Phase IV helps identify any uncommon side effects or interactions that were not apparent during the more controlled conditions of earlier trials. The statement that Phase IV usually has more subjects is accurate in highlighting that these trials can enroll a broader swath of patients, who may be taking the medication as prescribed in a general healthcare environment, thus enriching data on the drug's performance and safety profile.