We developed two pharmacokinetic ligand binding assays in human serum and urine for a drug program using a commercially available cytokine as reference material to align with prior preclinical studies. The material was supplied in activity units and released based on biological activity testing.
Although matrix and heterophilic antibody interference were resolved through antibody screening, optimization, and blocking strategies, significant variability persisted between independently prepared standards and quality controls. Standardized dilution schemes and automated liquid handling improved consistency but did not eliminate inter-run variability. During validation, inter-run QC precision reached 26.1%, and instrument response variability among standard preparations ranged from 11.3% to 60.3%. Extensive troubleshooting did not resolve the inconsistency.
Because variability occurred in both matrices, focus shifted to the shared reference material. Adsorption testing demonstrated analyte loss up to 61% bias. Reformulation with 0.2% surfactant reduced inter-run QC precision to 3.5%, enabling successful validation of both assays.
Learning Objectives:
Upon completion, participants will be able to identify and mitigate critical reagent–related variability to improve robustness and reproducibility in quantitative ligand binding assays.
Upon completion, participants will be able to explore sources of inter-run variability and apply troubleshooting strategies during ligand binding assay development and validation.
Upon completion, participants will be able to understand the impact of reference material formulation and adsorption on assay performance and implement mitigation strategies to improve assay consistency.
