Clinical endpoint sensitivity in rheumatoid arthritis: modeling and simulation

Area of Science:

• Rheumatology
• Clinical Trial Design
• Pharmacometrics

Background:

• Rheumatoid Arthritis (RA) clinical trials commonly use American College of Rheumatology (ACR) response rates (ACR20, ACR50, ACR70) and Disease Activity Score 28-joint count (DAS28) as efficacy endpoints.
• Understanding the discriminative power of these endpoints is crucial for optimizing clinical trial design and evaluating treatment efficacy.

Purpose of the Study:

• To develop longitudinal exposure-response models for ACR and DAS28 endpoints for four biologics used in RA management.
• To simulate clinical outcomes under various treatment regimens and assess the discriminative sensitivity of efficacy endpoints.

Main Methods:

• Longitudinal modeling was used to quantify exposure-response relationships for ACR and DAS28.
• Clinical trial simulations were performed to evaluate endpoint performance.
• Power analysis was conducted to assess the discriminative sensitivity of ACR20 and DAS28.

Main Results:

• Both ACR20 and DAS28 demonstrated lower power in distinguishing between two doses compared to differentiating treatment effects over placebo/Methotrexate (MTX) control.
• The ACR20 response rate generally showed higher power than DAS28 in detecting treatment effects against placebo/MTX control.

Conclusions:

• ACR20 and DAS28 have different strengths in detecting treatment effects in RA clinical trials.
• Findings provide valuable insights for designing future RA clinical trials to improve endpoint selection and statistical power.