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.

Nanobody-based microfluidic human Fc assay for preclinical plasma quantification of IgG1/1.1 and IgG1-Fc-conjugates

BACKGROUND

Therapeutic antibodies and Fc-conjugates are becoming increasingly popular for disease management and accurate and sensitive pharmacokinetic measurements are critical in lead candidate selection in pre-clinical drug discovery.

METHODS AND STUDY DESIGN

Human Fc-specific intact monoclonal antibodies, polyclonal antibodies, Fab fragments, aptamers, affibodies and nanobodies were screened for potential as biotinylated capture moieties in a microfluidic assay. Test compounds were Bevacizumab, Rituximab, Infliximab as well as an in-house IgG1.1 and an IgG1-drug conjugate.

RESULTS

Capture molecules were tested for specificity in plasma matrices from beagle dog, rat, mouse, pig, rhesus monkey and cynomolgus monkey. We find that the llama nanobody provides the best selectivity across across species. The assay usability were verified in cynomolgus monkey pharmacokinetic studies of in-house IgG1.1 and IgG1-fusion molecules.

CONCLUSION

The presented generic nanobody-based assay may find relevance in preclinical testing of future human Fc-containing drug conjugates devoid of Fab fragments and intact monoclonal antibodies.

Competitive Protein Binding Assay of Naproxen by Human Serum Albumin Functionalized Silicon Dioxide Nanoparticles

We have developed a new competitive protein binding assay (CPBA) based on human serum albumin functionalized silicon dioxide nanoparticles (nano-SiO₂-HSA) that can be used for naproxen determination in urine. Compared with a conventional multi-well reaction plate, nano-SiO₂ with a high surface-area-to-volume ratio could be introduced as a stationary phase, markedly improving the analytical performance. Nano-SiO₂-HSA and horseradish peroxidase-labeled-naproxen (HRP-naproxen) were prepared for the present CPBA method. In this study, a direct competitive binding to nano-SiO₂-HSAwas performed between the free naproxen in the sample and HRP-naproxen. Thus, the catalytic color reactions were investigated on an HRP/3,3'5,5'-tetramethylbenzidine (TMB)/H₂O₂ system by the HRP-naproxen/nano-SiO₂-HSA composite for quantitative measurement via an ultraviolet spectrophotometer. A series of validation experiments indicated that our proposed methods can be applied satisfactorily to the determination of naproxen in urine samples. As a proof of principle, the newly developed nano-CPBA method for the quantification of naproxen in urine can be expected to have the advantages of low costs, fast speed, high accuracy, and relatively simple instrument requirements. Our method could be capable of expanding the analytical applications of nanomaterials and of determining other small-molecule compounds from various biological samples.

Optimizing NBE PK/PD assays using the Gyrolab Affinity Software; conveniently within the bioanalyst's existing workflow

Aim: The fully automated microfluidics-based Gyrolab is a popular instrument for the bioanalysis of protein therapeutics; requiring minimal sample and reagent volumes. Gyros offers affinity software for determining binding affinity in solution using a high-throughput method and miniaturized reactions. Results: Using this affinity software, multiple CTGF-targeting reagents were characterized on the Gyrolab after <100% target coverage was seen in a cynomolgus pharmacokinetic/PD study dosed with anti-CTGF antibodies. The results uncovered magnitude differences in binding affinities between the dosed antibody, target and assay reagents. Conclusion: The binding affinity values were used to investigate reduced target coverage and results highlight potential of the affinity software for incorporation into the bioanalyst's existing Gyrolab workflow for characterizing reagents and optimizing pharmacokinetic/PD bioanalytical assays.

Overcoming disease-specific matrix effect in a clinical pharmacokinetic assay using a microfluidic immunoassay technology

AIM

Etrolizumab, a humanized monoclonal antibody, has demonstrated clinical remission in a Phase II study of ulcerative colitis patients. In the Phase III program, a second indication, Crohn's disease was added. The pharmacokinetic ELISA used in the Phase I/II studies in normal human and ulcerative colitis sera exhibited matrix interference in the Crohn's disease population, necessitating implementation of a new technology. Methodology & results: Optimization of the original ELISA and assay redevelopment using different antibody pairs did not result in substantive improvements, necessitating implementation of an alternative technology for assay development.

CONCLUSION

We highlight the challenges encountered with optimization/redevelopment of the original ELISA and discuss results of the new assay on the Gyros platform.