An ultra-sensitive clinical biomarker assay: quantitation of thymus and activation-regulated chemokine in human plasma

Background: Thymus and activation-regulated chemokine (TARC) is a Th2 type, pro-allergic secreted chemokine. TARC in plasma/serum has been proposed as a marker for disease activity of atopic dermatitis (AD) and as a pharmacodynamic readout in the clinical development of novel agents for the treatment of AD. Results: An ultra-sensitive electrochemiluminescence assay for TARC in human plasma was developed and analytically validated. The assay demonstrated excellent performance characteristics, including precision, sensitivity, dilution linearity, accuracy and specificity. Stability and biological variability of TARC in plasma were also assessed for clinical sample analysis and data interpretation. Conclusion: The improved sensitivity allowed the measurement of approximately 90% TARC inhibition from baseline levels of healthy subjects and >90% TARC inhibition from baseline levels of AD patients after drug treatment. A validated TARC electrochemiluminescence assay enables pharmacodynamic assessment in the dev...