Solving selectivity issues in LBAs: case study using Gyrolab to quantify CB307, a bispecific Humabody in human serum

Aim: Endogenous interferents can cause nonselectivity in ligand binding pharmacokinetic assays, leading to inaccurate quantification of drug concentrations. We describe the development of a Gyrolab immunoassay to quantify a new modality, CB307 and discuss strategies implemented to overcome matrix effects and achieve selectivity at the desired sensitivity. Results: Matrix effects were mitigated using strategies including increasing minimum required dilution (MRD) and lower limit of quantification, optimization of antibody orientation, assay buffer and solid phase. Conclusion: The strategies described resulted in a selective method for CB307 in disease state matrix that met bioanalytical method validation (BMV) guidance and is currently used to support clinical pharmacokinetic sample analysis in the first-in-human POTENTIA clinical study (NCT04839991) as a secondary clinical end point.

A bridging immunogenicity assay for monoclonal antibody: case study with SHR-1222

Aim: SHR-1222 is a humanized monoclonal antibody targeted to soluble sclerostin. To support the preclinical study of SHR-1222 in cynomolgus monkeys, a method for the detection of anti-drug antibodies is required. Results: A bridging immunogenicity method for the detection of anti-SHR-1222 antibodies was developed and validated. In the method, minimal required dilution, normalization factor and confirmatory cut point were 1:20, 4.35 and 10.45%, respectively. The method was successfully applied to evaluate a multiple-dose toxicity study in monkeys. Conclusion: The proposed method allows for the detection of anti-SHR-1222 antibodies in preclinical studies and aids in the interpretation of pharmacokinetic changes in certain animals. The soluble targets interference on anti-drug antibody detection can be blocked or decreased by the therapeutic drug.

Bypassing nonparallelism of a monoclonal antibody ligand-binding assay by employment of alternative assay formats

Determination of concentration-time profiles in cynomolgus monkeys of a therapeutic monoclonal antibody against a soluble target revealed a substantial discrepancy between a generic anti-human IgG capture/detection and target bridging assay with the target bridging assay leading to dose- and time-dependent underquantification of drug concentrations, lack of parallelism and subsequently different pharmacokinetic parameters. In contrast, plasma levels derived from a target capture and an anti-idiotypic antibody bridging assay were in close concordance with the generic assay and demonstrated parallelism with high precision across several dilutions. The results provide a practical attempt to overcome nonparallelism by employing alternative assay formats utilizing tailored assay reagent combinations in order to obtain unbiased pharmacokinetic data.

Reduction of dilution error in ELISAs using an internal standard

Background: Dilution bias is a major cause of immunoassay variability due to the lack of an internal standard to determine the true versus the expected dilution value. Methodology: We used an internal control to measure dilution bias in an ELISA. Acridine-orange was added at the first dilution step and monitored throughout dilutions. Assay results were corrected using the fluorescent signal ratio between samples and reference. Acridine dilution correlated with analyte-specific assay measurements (R2 = 0.987). Correction of assay results with the measured dilution factor improved both accuracy and precision resulting in a reduction of >50% %CV reduction. Conclusion: Dilution correction can significantly improve accuracy and precision of immunoassays. Additional control strategies may further mitigate other sources of variability.