The case for cross-over trials in phase III

Area of Science:

• Clinical Trials Methodology
• Biostatistics
• Drug Development

Background:

• A common belief suggests avoiding cross-over trials in phase III drug development, influenced by past guidance.
• Historically, cross-over trials have been instrumental in the successful development and regulatory approval of numerous established medicines.
• Current understanding of medical indications allows for better identification of advantageous scenarios for phase III cross-over trials.

Purpose of the Study:

• To challenge the prevailing notion that cross-over trials are unsuitable for phase III drug development.
• To review the disadvantages of cross-over trials and discuss early detection methods.
• To highlight the key advantages of cross-over trials, including study size and treatment-by-patient interaction.

Main Methods:

• Review of known disadvantages of cross-over trials compared to parallel group trials.
• Discussion of methods for detecting potential issues in early trial phases (I and II).
• Comparative analysis of different cross-over trial analysis strategies using simulation, particularly when baseline measurements are included.

Main Results:

• Cross-over trials offer significant advantages in study size and understanding treatment-by-patient interactions.
• Concerns regarding analysis methods do not necessitate avoiding cross-over trials, especially with baseline measurements.
• Potential risks associated with cross-over trials tend to diminish treatment effect estimates, posing minimal concern for regulators.

Conclusions:

• Cross-over trials are a valuable and versatile research tool throughout all stages of new medicine development, including phase III.
• Excluding cross-over trials from phase III drug development is unnecessary and counterproductive.
• The strategic use of cross-over designs, supported by appropriate analysis, remains beneficial for pharmaceutical research.