Biomarker Assay Validation by Mass Spectrometry

Decades of discussion and publication have gone into the guidance from the scientific community and the regulatory agencies on the use and validation of pharmacokinetic and toxicokinetic assays by chromatographic and ligand binding assays for the measurement of drugs and metabolites. These assay validations are well described in the FDA Guidance on Bioanalytical Methods Validation (BMV, 2018). While the BMV included biomarker assay validation, the focus was on understanding the challenges posed in validating biomarker assays and the importance of having reliable biomarker assays when used for regulatory submissions, rather than definition of the appropriate experiments to be performed. Different from PK bioanalysis, analysis of biomarkers can be challenging due to the presence of target analyte(s) in the control matrices used for calibrator and quality control sample preparation, and greater difficulty in procuring appropriate reference standards representative of the endogenous molecule. Several papers have been published offering recommendations for biomarker assay validation. The situational nature of biomarker applications necessitates fit-for-purpose (FFP) assay validation. A unifying theme for FFP analysis is that method validation requirements be consistent with the proposed context of use (COU) for any given biomarker. This communication provides specific recommendations for biomarker assay validation (BAV) by LC-MS, for both small and large molecule biomarkers. The consensus recommendations include creation of a validation plan that contains definition of the COU of the assay, use of the PK assay validation elements that support the COU, and definition of assay validation elements adapted to fit biomarker assays and the acceptance criteria for both.

A continued method performance monitoring approach for the determination of pediatric renin samples - application within a European clinical trial

Background Plasma renin levels were determined in the academia-driven, EU-funded "Labeling of Enalapril from Neonates up to Adolescents" (LENA) project to evaluate its role in pediatric heart failure. Quality-controlled bioanalysis is crucial to ensure reliable data generation. However, a comprehensive bioanalytical quality control (QC) concept to monitor the method performance within an academic environment was lacking. Methods Thus, a QC concept was designed encompassing regulatory guidance, international recommendations and current scientific discussions. The concept included (1) a system-suitability test, (2) verification of single bioanalytical runs by calibration curve performance and evaluation of QCs, (3) assessment of the inter-run accuracy according to Clinical Laboratory Standards Institute (CLSI) guideline, (4) monitoring of reproducibility by pediatric incurred samples, (5) blank-sample analysis and (6) participation in interlaboratory testing. Results The concept was successfully applied to the academic project. About 11% of single runs were identified as invalid and triggered a re-analysis of unknown samples being included in those runs. The usefulness of the customized inter-run monitoring was demonstrated and proved the good accuracy from the first to the last run. All 147 reanalyzed incurred sample pairs complied with regulatory requirements. Conclusions The regulatory complied QC concept was customized for the demands of academia-driven pediatric trials and contributed to the reliable quantification of 965 pediatric renin samples.

A comprehensive quality control system suitable for academic research: application in a pediatric study

Aim: Clinical research in pediatrics is progressively initiated by academia. As the reliability of pharmacodynamic measures is closely linked to the quality of bioanalytical data, bioanalytical quality assurance is crucial. However, clear guidance on comprehensive bioanalytical quality monitoring in the academic environment is lacking. Methods & results: By applying regulatory guidelines, international recommendations and scientific discussions, a five-step quality control system for monitoring the bioanalysis of aldosterone by immunoassay was developed. It comprised performance qualification, calibration curve evaluation, analysis of the intra- and inter-run performance via quality control samples, incurred sample reanalysis and external quality assessment by interlaboratory testing. A total of 55 out of 70 runs were qualified for the quantification of aldosterone in the study sample enabling the evaluation of 954 pediatric samples and demonstrating reliability over the 29-month bioanalysis period. Conclusion: The bioanalytical quality control system successfully monitored the aldosterone assay performance and proved its applicability in the academic environment.

New approaches for biomarker stability determination in regulated bioanalysis: trending, bridging and incurred samples

Aim: Determining the stability of biomarkers continues to present challenges. Disease states, complex matrices and differences between recombinant and endogenous analytes require new approaches to maintain stability and measure it. In this report, we determine stability for two assays using trending and statistical analysis. Methodology & results: Monitoring trends helps identify out of specification measurements and determine whether concerns are due to the stability of the analyte. We also describe challenges presented when measuring arginase activity in human sputum, a complex matrix, for respiratory diseases. We controlled preanalytical protease activity and collection heterogeneity and monitored incurred sample stability to improve stability of arginine. Conclusion: These new approaches to achieving and determining biomarker stability may provide solutions for increasingly complex biomarker measurements.