Aim: Critical reagents have significant impact on ligand-binding assay performance. The critical reagents selected during method development should be well-evaluated, as the quality of these reagents will dictate performance of the assay over time. Critical reagents in ligand-binding assays are almost always produced using a biological system, so batch yield, purity and performance tend to vary greatly. Due to the essential nature of critical reagents in the assay, changes in critical reagents can have dramatic impact on the assay and results, so close monitoring of assay performance is required. Methodology & results: We present here three examples of critical reagent lot changes that required creative solutions to maintain assay performance. The first case study is an example of the impact of different lots of analyte within a quantitative assay that resulted in the need to redevelop the assay in a different format. Case study two outlines an assay where a surrogate matrix is the critical reagent in an assay and the difficulties encountered over the course of several years and lot changes. The third case study covers an immunogenicity assay with a commercial detection that did not have sufficient quantity to cover the entire study lifecycle. As a result of the reagent change, a new assay was developed. Discussion & conclusion: A robust plan for critical reagent generation and lifecycle management should be adapted in order to avoid costly delays and rework. The performance of an assay depends on the continuity of the critical reagent supply. Reagents should be carefully selected to include the binding and performance properties required for an assay.
Workshop Report: AAPS Workshop on Method Development, Validation, and Troubleshooting of Ligand-Binding Assays in the Regulated Environment