Automated ELISA for potency measurements of therapeutic antibodies and antibody fragments

Potency assays are essential for the development and quality control of biopharmaceutical drugs, but they are often a time limiting factor due to manual handling steps and consequently low analytical throughput. On the other hand, automation of potency assays can be challenging due to their complexity and the use of biological materials. ELISA (enzyme-linked immunosorbent assay) is widely used for potency determination and is a good candidate for automation as all ELISA types depend on the same basic steps: coating, blocking, sample incubation, detection, and signal measurement. Nevertheless, ELISA for relative potency measurements still require drug-specific development and assay validation thereby complicating automation efforts. To simplify potency testing by ELISA, we first developed a manual protocol generally applicable to different drugs and then adapted this protocol for automated measurements. We identified unexpected critical parameters which had to be adapted to transfer the manual ELISA to an automated liquid handling system and we demonstrated that gravimetric sample dilution is unnecessary with the automated protocol. Both manual and automated protocols were validated and compared using multiple biotherapeutics. The automated protocol showed similar or higher precision and accuracy when compared to the manual method.

Generic UPLC-MS/MS and Gyrolab assays with blood microsampling for pharmacokinetic assessments of therapeutic antibodies in mice

Serial blood sampling from one animal is useful to understand relationship between pharmacokinetics (PK) and pharmacological or toxicological events in individual animals. To assess its feasibility in mice, two therapeutic antibodies were used to evaluate impacts by different blood sampling methods, sampling sites, and assay platforms on PK. Denosumab and Panitumumab were intravenously administered to mice and only 0.05 mL of blood sample per point was collected from jugular vein or tail vein. Blood samples were collected serially from a mouse or collected by traditional composite sampling from each mouse. Plasma concentrations of the two drugs were assayed by a generic ligand binding assay using Gyrolab or by a generic ultra-performance liquid chromatography with tandem mass spectrometry. The two assay platforms showed acceptable accuracy and precision and gave comparable PK parameters of the drugs, suggesting that both assays were successfully applied to the PK assessments. Comparable results in the PK profiles were noted between serial and composite blood samplings and differences in the two sampling sites did not impact PK. These findings suggest that microsampling combined with generic assays is useful to assess PK profiles of therapeutic antibodies in mice.

Use of a Microfluidic Platform To Evaluate and Predict Reagent Performance in Microtiter Plate-Based Immunoassays

Selection and characterization of antibodies are critically important in establishing robust immunoassays to support the development efforts of vaccines. Plate-based ELISA can be time- and resource-intensive to select initial antibody clones or characterize downstream resupply lots while providing limited information regarding the binding characteristics of the antibodies beyond concentration-response curves. This work applied the microfluidic Gyrolab to holistically evaluate immunoassay reagents through analyses of concentration-response curves as well as antibody-antigen interactions visualized in column images and affinity estimates. We exploited the automation capability of the Gyrolab to reduce the resources (time, reagents, and scientists) required for screening and evaluating antibody reagents. Using a flexible semi-universal assay format, we compared antibody clones for selection and resupply lots of sera and monoclonal antibodies in a simple "plug-and-play" manner without antibody modifications. We found that the performance of antibodies in the Gyrolab correlated well with the trends observed in traditional ELISAs, while the Gyrolab provided additional advantages over plate-based assays such as column images of antibody binding and affinity measurements.

The respiratory syncytial virus fusion protein-specific B cell receptor repertoire reshaped by post-fusion subunit vaccination

Respiratory syncytial virus (RSV) is the major cause of acute lower respiratory illness in children of less than 5 years of age which usually results in hospitalization or even in death. Vaccine development is hampered in consequence of a failed vaccine trial with fatalities in the 1960s. Even though research has been more focused on the RSV fusion protein in its pre-fusion conformation, maternal vaccination with post-fusion protein (post F) was considered as a promising vaccine strategy for passive immunization of babies, because post F preserves very potent neutralizing epitopes. We extensively analyzed post F-binding B cell receptor (BCR) repertoires of three vaccinees who received a post F-subunit vaccine in the context of a first-in-human, Phase 1, randomized, observer-blind, placebo-controlled clinical trial (ClinicalTrials.gov Identifier: NCT02298179). In order to compare the vaccine-induced BCR repertoires with BCR repertoires induced by natural infection, we also analyzed pre F- and post F-binding BCRs isolated from a healthy blood donor with relatively high F-binding memory B cell (MBC) frequencies. Analysis of the vaccine-induced repertoires revealed that preferentially V_H4-encoded BCRs were expanded in response to vaccination. Estimation of antigen-driven selection further demonstrated that expanded BCRs accumulated positively selected replacement mutations which substantiated the hypothesis that post F-vaccination induces diversification of V_H4-encoded BCRs in germinal centers. Comparison of the vaccine-induced BCR repertoires with clonally related pre and post F-binding BCRs of the healthy blood donor suggested that the vaccine expanded pre/post F cross-reactive MBCs. Interestingly, several vaccine-induced BCRs shared stereotypic VDJ gene junctions with known neutralizing Abs. Once expressed for functional characterization, the selected monoclonal Abs demonstrated the predicted neutralization activities in plaque reduction neutralization assays indicating that the post F-vaccine induced expansion of neutralizing BCRs.

Development of Rabbit Monoclonal Antibodies for Quantitation of Therapeutic Human Antibodies in Preclinical Non-Human Primate Studies

During preclinical studies, there is a great need to develop monoclonal antibodies (mAbs) that are specific to human immunoglobulin (IgG), without binding to monkey IgG, to detect therapeutic human mAb in non-human primates. We took advantage of the latest rabbit B cell cloning technology to develop six unique rabbit anti-human IgG mAb clones for this purpose. These clones are capable of binding to both human IgG and Fab with high affinity without nonspecific binding to cynomolgus monkey IgG. These clones have been evaluated as a generic capture reagent for the detection of human IgG and Fab, in the presence of cynomolgus monkey serum, by Gyrolab™ immunoassay. They may be used in singlet or as pairs for the detection of human IgG, in any host animal, to meet the need for therapeutic mAb development in preclinical studies.

Evaluation of a digital dispenser for direct curve dilutions in a vaccine potency assay

Dilutions are a common source of analytical error, both in terms of accuracy and precision, and a common source of analyst mistakes. When serial dilutions are used, errors compound, even when employing laboratory automation. Direct point dilutions instead of serial dilutions can reduce error but is often impractical as they require either large diluent volumes or very small sample volumes when performed with traditional liquid handling equipment. We evaluated preparation of dilution curves using a picoliter digital dispenser, the HP, Inc. / TECAN D300 which is capable of accurately delivering picoliter volumes directly into sample wells filled with assay diluent. Dilution linearity and variability of the direct dilutions were similar to or less than those generated with a traditional liquid handler as measured using a fluorophore assay and an ELISA used to measure vaccine potency. Minimum concentrations for detergent in the dispensed sample were identified but no correlation with detergent characteristics was observed. The tolerance to protein in the sample was evaluated as well with up to 5% BSA having no impact on dispense linearity and precision. We found the digital dispenser to reduce automation complexity while maintaining or improving assay performance in addition to facilitating complex plate lay-outs.

A semi-universal assay platform to quantitate vaccines with potential applications for biotherapeutics

AIM

Biologics development often requires multiple immunoassays to evaluate both assay reagents and potential drug candidates resulting in extensive analytical development.

METHODOLOGY

We developed a semi-universal, 5-layer platform assay on Gyrolab using secondary antispecies or anti-isotype-specific capture and detection antibodies. We applied the assay to several multivalent vaccines.

RESULTS

Method performance exhibited a median accuracy of 110%, reproducibility of 9% CV and intermediate precision of 11% CV. System suitability criteria were met for 92.5% of the samples and only one out of 31 replicate samples exhibited a %CV greater than 20%.

CONCLUSION

The semi-universal Gyrolab assay allowed assay development without reagent labeling. The format could also be translated into a plate-based assay.

Centrifugal microfluidic platform for ultrasensitive detection of botulinum toxin

We present an innovative centrifugal microfluidic immunoassay platform (SpinDx) to address the urgent biodefense and public health need for ultrasensitive point-of-care/incident detection of botulinum toxin. The simple, sample-to-answer centrifugal microfluidic immunoassay approach is based on binding of toxins to antibody-laden capture particles followed by sedimentation of the particles through a density-media in a microfluidic disk and quantification by laser-induced fluorescence. A blind, head-to-head comparison study of SpinDx versus the gold-standard mouse bioassay demonstrates 100-fold improvement in sensitivity (limit of detection = 0.09 pg/mL), while achieving total sample-to-answer time of <30 min with 2-μL required volume of the unprocessed sample. We further demonstrate quantification of botulinum toxin in both exogeneous (human blood and serum spiked with toxins) and endogeneous (serum from mice intoxicated via oral, intranasal, and intravenous routes) samples. SpinDx can analyze, without any sample preparation, multiple sample types including whole blood, serum, and food. It is readily expandable to additional analytes as the assay reagents (i.e., the capture beads and detection antibodies) are disconnected from the disk architecture and the reader, facilitating rapid development of new assays. SpinDx can also serve as a general-purpose immunoassay platform applicable to diagnosis of other conditions and diseases.

Validation of a microfluidic platform to measure total therapeutic antibodies and incurred sample reanalysis performance

BACKGROUND

A microfluidic platform-based assay was validated to measure a humanized or fully human IgG in rat serum samples.

MATERIALS & METHODS

The cumulative assessment for accuracy and precision was performed with three accuracy and precision runs.

RESULTS

The inter-assay accuracy (mean %bias) ranged from -4.3 to 3.8%, and inter-batch %CV ranged from 5.0 to 9.2%. The method acceptance criterion was determined as 15% total error. The assay dynamic range was 50 to 10000 ng/ml. Incurred sample reanalysis passed with 95% of samples meeting incurred sample reanalysis acceptance criteria. Potential carryover effect was not observed.

CONCLUSION

This study demonstrated the need for evaluating additional platform-specific processes when new technologies are employed to ensure the reproducibility of a successfully validated microfluidic platform method.

Addressing matrix effects in ligand-binding assays through the use of new reagents and technology

Background: Ligand-binding assays (LBAs) used in the quantification of biotherapeutics for pharmacokinetic determinations rely on interactions between reagents (antibodies or target molecule) and the biotherapeutic. Most LBAs do not employ an analyte extraction procedure and are susceptible to matrix interference. Here, we present a case study on the development of a LBA for the quantification of a PEGylated domain antibody where matrix interference was observed. The assay used to support the single ascending dose study was a plate-based electrochemiluminescent assay with a lower limit of quantification of 80 ng/mL. To meet sensitivity requirements of future studies, new reagents and the Gyrolab™ Workstation were evaluated. Results: Assay sensitivity improved nearly threefold in the final method utilizing new antibody reagents, a buffer containing blockers to human anti-animal antibodies, and the Gyrolab Workstation. Conclusion: Experimental data indicate that all factors changed played a role in overcoming matrix effects.

Challenges in selectivity, specificity and quantitation range of ligand-binding assays: case studies using a microfluidics platform

Background: Method developers of plate-based ligand-binding assays (LBAs) often face challenges establishing selectivity, specificity and range of quantitation to meet the needs of a particular study. Case studies are presented to compare different ligand-binding immunoassay platforms (plate-based vs microfluidic system) in method development to support pharmacokinetic and pharmacodynamic studies. Results: Studies highlight the challenges of plate-based LBAs to establish selectivity, specificity and range of quantitation as a result of nonspecific background signal, matrix interference, lack of linearity and drug interference. The fast assay kinetics of a microfluidic immunoassay system was shown to generally reduce nonspecific background and matrix effects, while increasing assay linear range and drug tolerance. Conclusion: The short incubation times with microfluidics can be beneficial for LBAs burdened by matrix effects and in these cases had superior assay performance compared with widely used immunoassay platforms in bioanalysis, for example, Meso Scale Discovery® and enzyme-linked immunosorbent assay.

Assay formats: Recommendation for best practices and harmonization from the global bioanalysis consortium harmonization team

As part of the GBC (Global Bioanalysis Consortium), the L3 assay format team has focused on reviewing common platforms used to support ligand binding assays in the detection of biotherapeutics. The following review is an overview of discussions and presentations from around the globe with a group of experts from different companies to allow an international harmonization of common practices and suggestions for different platforms. Some of the major platforms include Gyrolab, Erenna, RIA, AlphaLISA, Delfia, Immuno-PCR, Luminex, BIAcore, and ELISAs. The review is meant to support bioanalysts in taking decisions between different platforms depending on the needs of the analyte with a number of recommendations to help integration of platforms into a GLP environment.