Association of Protocol Design-Related Factors With Enrollment Duration in Clinical Trials

Area of Science:

• Clinical Research
• Drug Development
• Health Services Research

Background:

• Patient enrollment is crucial for clinical trial success, yet many trials face recruitment delays.
• Protocol design is a significant barrier to efficient participant recruitment.
• Quantitative studies linking protocol design to enrollment duration are limited.

Purpose of the Study:

• To quantitatively assess the association between clinical trial protocol design elements and enrollment duration.
• To compare these associations across pre- and post-COVID-19 pandemic periods.

Main Methods:

• Cross-sectional study using data from ClinicalTrials.gov and a related database.
• Included industry-sponsored phase 2 and 3 drug trials completed between January 2017 and September 2024.
• Multiple linear regression analysis to identify factors associated with enrollment duration.

Main Results:

• 1286 trials met the inclusion criteria.
• Longer enrollment duration was associated with a higher number of original enrollments, more inclusion criteria, and more days of assessment.
• Pre-pandemic, assessment days were the primary factor; post-pandemic, inclusion criteria became the strongest factor.

Conclusions:

• Clinical trial enrollment duration is significantly influenced by protocol design features.
• Careful planning of inclusion criteria, assessment burden, and enrollment targets is essential for improving recruitment efficiency.
• Further research is needed to examine causal relationships.