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.

Evaluating a Multiscale Mechanistic Model of the Immune System to Predict Human Immunogenicity for a Biotherapeutic in Phase 1.

A mechanistic model of the immune response was evaluated for its ability to predict anti-drug antibody (ADA) and their impact on pharmacokinetics (PK) and pharmacodynamics (PD) for a biotherapeutic in a phase 1 clinical trial. Observed ADA incidence ranged from 33 to 67% after single doses and 27-50% after multiple doses. The model captured the single dose incidence well; however, there was overprediction after multiple dosing. The model was updated to include a T-regulatory (Treg) cell mediated tolerance, which reduced the overprediction (relative decrease in predicted incidence rate of 21.5-59.3% across multidose panels) without compromising the single dose predictions (relative decrease in predicted incidence rate of 0.6-13%). The Treg-adjusted model predicted no ADA impact on PK or PD, consistent with the observed data. A prospective phase 2 trial was simulated, including co-medication effects in the form of corticosteroid-induced immunosuppression. Predicted ADA incidences were 0-10%, depending on co-medication dosage. This work demonstrates the utility in applying an integrated, iterative modeling approach to predict ADA during different stages of clinical development.

Report on the AAPS Immunogenicity Guidance Forum.

In September 2018, the American Association of Pharmaceutical Scientists (AAPS) conducted an Annual Guidance Forum on the considerations related to immunogenicity testing for therapeutic protein products. In addition to a broad representation by the pharmaceutical industry, the event included strong representation by leading scientists from the US Food and Drug Administration (FDA). The agency and industry perspectives and updates to the guidance were presented. Specific topics that were discussed included the strategies of anti-drug antibody (ADA) assay cut-point assessments, the selection of ADA-positive controls (PCs), and the evaluation of PC performance. Assessment strategies and relevance of ADA assay attributes were also discussed, including assay drug tolerance and ADA assay sensitivity. The following is a summary of the discussion.

Bead-extraction and heat-dissociation (BEHD): A novel way to overcome drug and matrix interference in immunogenicity testing.

Biological therapeutics are foreign antigens and can potentially induce immune response resulting in the formation of anti-drug antibodies (ADA), which in turn may lead to a wide range of side effects. Neutralizing Ab (NAb) is a subset of ADA that can bind to the pharmacological activity regions of therapeutic to inhibit or complete neutralize its clinical efficacy. A cell-based functional NAb assay is preferred to characterize its neutralization activity. However, cell-based NAb assays are often vulnerable to drug interference, as well as interference from numerous serum factors, including but not limited to growth factors and disease-related cytokines. Bead Extraction with Acid Dissociation (BEAD) has been successfully applied to remove circulating drug and/or other interfering factors from human serum samples, thereby enriching for ADA/NAb. However, the harsh acid used in the extraction procedure can cause irreversible denaturing of NAb and lead to underestimated NAb measurement. Herein we describe a new approach when acid-dissociation is not optimal for a PEGylated domain antibody (Ab). We further demonstrate that heating at 62 °C can not only dissociate drug/ADA/NAb immune complex but also selectively and irreversibly denature domain Ab drug due to much lower thermal stability of the domain Ab, when compared to that of full antibodies. The irreversible denaturing of the drug favors the formation of an immune complex between ADA/NAb and the added biotinylated drug thus increasing the recovery of ADA/NAb from samples. We call this new procedure Bead Extraction with Heat Dissociation (BEHD), which can potentially be applied to other NAb assays that have poor compatibility with acid dissociation.

Concerted application of LC-MS and ligand binding assays to better understand exposure of a large molecule drug.

AIM: A ligand-binding assay (LBA) was used to measure exposure of PRM-151, the recombinant form of human pentraxin-2 (PTX-2), a complex pentamer with multiple binding partners. However, the assay showed a lack of dose-dependent exposure in select preclinical species and it could not differentiate the infused PRM-151 from the endogenous PTX-2 in nonhuman primates. MATERIALS & METHODS: Instead of assessing interference from its multiple binding partners, which could be time consuming and laborious, a LC-MS assay avoid of these interference was implemented to measure 'total' drug without the use of immunoaffinity capture reagents. RESULTS & CONCLUSION: The resultant LC-MS data confirmed the original data and the lack of dose-dependent exposure is now understood to be due to the multiple and diverse targets and functions and resultant complex biodistribution rather than an assay artifact.

Development and validation of a functional cell-based neutralizing antibody assay for ipilimumab.

Ipilimumab is the first US FDA-approved immune checkpoint-blocking antibody drug to harness the patient's own immune cells. One of the postmarketing requirements is to develop a cell-based neutralizing antibody assay. Here, we share some of the most challenging aspects encountered during the assay development: new cell line construction; an unexpected inhibition of T-cell activation by low concentrations of ipilimumab; and two issues caused by sample pretreatment with acid dissociation to overcome drug interference: instability of neutralizing antibody positive control at low pH, and incompatibility of commonly used acid dissociation buffers in the cell assay. After troubleshooting and optimization, we successfully validated the assay and used the assay to test clinical samples to date.

Surface plasmon resonance as a tool for ligand-binding assay reagent characterization in bioanalysis of biotherapeutics.

Ligand-binding assay (LBA) performance depends on quality reagents. Strategic reagent screening and characterization is critical to LBA development, optimization and validation. Application of advanced technologies expedites the reagent screening and assay development process. By evaluating surface plasmon resonance technology that offers high-throughput kinetic information, this article aims to provide perspectives on applying the surface plasmon resonance technology to strategic LBA critical reagent screening and characterization supported by a number of case studies from multiple biotherapeutic programs.

2017 White Paper on recent issues in bioanalysis: a global perspective on immunogenicity guidelines & biomarker assay performance (Part 3 - LBA: immunogenicity, biomarkers and PK assays).

The 2017 11th Workshop on Recent Issues in Bioanalysis took place in Los Angeles/Universal City, California, on 3-7 April 2017 with participation of close to 750 professionals from pharmaceutical/biopharmaceutical companies, biotechnology companies, contract research organizations and regulatory agencies worldwide. WRIB was once again a 5-day, week-long event - a full immersion week of bioanalysis, biomarkers and immunogenicity. As usual, it was specifically designed to facilitate sharing, reviewing, discussing and agreeing on approaches to address the most current issues of interest including both small- and large-molecule analysis involving LC-MS, hybrid ligand-binding assay (LBA)/LC-MS and LBA approaches. This 2017 White Paper encompasses recommendations emerging from the extensive discussions held during the workshop, and is aimed to provide the bioanalytical community with key information and practical solutions on topics and issues addressed, in an effort to enable advances in scientific excellence, improved quality and better regulatory compliance. Due to its length, the 2017 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 3) covers the recommendations for large-molecule bioanalysis, biomarkers and immunogenicity using LBA. Part 1 (LC-MS for small molecules, peptides and small molecule biomarkers) and Part 2 (hybrid LBA/LC-MS for biotherapeutics and regulatory agencies' inputs) are published in volume 9 of Bioanalysis, issues 22 and 23 (2017), respectively.

A systematic study of the effect of low pH acid treatment on anti-drug antibodies specific for a domain antibody therapeutic: Impact on drug tolerance, assay sensitivity and post-validation method assessment of ADA in clinical serum samples.

We developed a homogeneous bridging anti-drug antibody (ADA) assay on an electro chemiluminescent immunoassay (ECLIA) platform to support the immunogenicity evaluation of a dimeric domain antibody (dAb) therapeutic in clinical studies. During method development we evaluated the impact of different types of acid at various pH levels on polyclonal and monoclonal ADA controls of differing affinities and on/off rates. The data shows for the first time that acids of different pH can have a differential effect on ADA of various affinities and this in turn impacts assay sensitivity and drug tolerance as defined by these surrogate controls. Acid treatment led to a reduction in signal of intermediate and low affinity ADA, but not high affinity or polyclonal ADA. We also found that acid pretreatment is a requisite for dissociation of drug bound high affinity ADA, but not for low affinity ADA-drug complexes. Although we were unable to identify an acid that would allow a 100% retrieval of ADA signal post-treatment, use of glycine pH3.0 enabled the detection of low, intermediate and high affinity antibodies (Abs) to various extents. Following optimization, the ADA assay method was validated for clinical sample analysis. Consistencies within various parameters of the clinical data such as dose dependent increases in ADA rates and titers were observed, indicating a reliable ADA method. Pre- and post-treatment ADA negative or positive clinical samples without detectable drug were reanalyzed in the absence of acid treatment or presence of added exogenous drug respectively to further assess the effectiveness of the final acid treatment procedure. The overall ADA results indicate that assay conditions developed and validated based on surrogate controls sufficed to provide a reliable clinical data set. The effect of low pH acid treatment on possible pre-existing ADA or soluble multimeric target in normal human serum was also evaluated, and preliminary data indicate that acid type and pH also affect drug-specific signal differentially in individual samples. The results presented here represent the most extensive analyses to date on acid treatment of a wide range of ADA affinities to explore sensitivity and drug tolerance issues. They have led to a refinement of our current best practices for ADA method development and provide a depth of data to interrogate low pH mediated immune complex dissociation.

A multiplexed immunocapture liquid chromatography tandem mass spectrometry assay for the simultaneous measurement of myostatin and GDF-11 in rat serum using an automated sample preparation platform.

Myostatin, also known as growth differentiation factor 8 (GDF-8), is a protein acting as a negative regulator in skeletal muscle growth. Inhibition of myostatin by therapeutic agents provides opportunities for current unmet medical needs. In order to better understand drug engagement to aid the drug development, we have developed a hybrid LC-MS/MS method which can differentially measure myostatin and another protein from the same GDF family, GDF-11. Although the two proteins share high homology, the LC-MS/MS assay provided the specificity based on monitoring of unique surrogate peptide generated from enzymatic digestion. An automated sample preparation platform, Agilent AssayMap Bravo, was used for automated immunocapture. Capture antibody that is non-competing with our investigational drug and has similar binding affinity to both myostatin and GDF-11 was used. Therefore, total myostatin and GDF-11 including both free form and drug-bound form were captured and measured. The enriched sample was digested after reduction and alkylation. Two surrogate peptides (IPAMVVDR for myostatin and IPGMVVDR for GDF-11) were monitored and the lower limit of quantitation (LLOQ) was established at 1.0 ng/mL for myostatin and 0.1 ng/mL for GDF-11. The accuracy was demonstrated with recovery for IPAMVVDR between 99.2% and 103.1% and for IPGMVVDR between 90.3% and 114.5%. The developed hybrid assay exhibits sufficient sensitivity, accuracy and specificity to differentiate between the highly structurally similar myostatin and GDF-11. This analytical approach was successfully applied to a rat toxicology study, and was demonstrated to be a powerful tool for biomarker measurement in the present of a therapeutic agent.

Characterization of labeled reagents in ligand-binding assays by a surface plasmon resonance biosensor.

AIM: Ligand-binding assay (LBA) reagent labeling may change the binding characteristics of the reagent to its target and degrade its performance in LBAs. RESULTS: A surface plasmon resonance (SPR) biosensor was used to evaluate the impact of the biotin labeling process on reagent-binding kinetics and affinity for a specific target. The SPR results demonstrate that the biotin molar challenge ratio affects both association and dissociation rates for the labeled reagent binding to its target. The SPR results also predict the labeled reagent performance in LBAs. CONCLUSION: The methodology used in this study provides an example of using an SPR biosensor as an efficient way to analytically and functionally characterize critical reagents and to understand their performance postmodification in LBAs.

Accelerating Regulated Bioanalysis for Biotherapeutics: Case Examples Using a Microfluidic Ligand Binding Assay Platform.

The Gyrolab™ xP is a microfluidic platform for conducting ligand binding assays (LBAs) and is recognized for its utility in discovery bioanalysis. However, few reports have focused on the technology for regulated bioanalysis. This technology has the advantage of low reagent consumption, low sample volume, and automated ligand binding methods. To improve bioanalysis testing timelines and increase the speed at which biotherapeutics are delivered to patients, we evaluated the technology for its potential to deliver high-quality data at reduced testing timelines for regulated bioanalysis. Six LBA methods were validated to support bioanalysis for GLP toxicokinetic or clinical pharmacokinetic studies. Validation, sample analysis, and method transfer are described. In total, approximately 4000 samples have been tested for regulated bioanalysis to support 6 GLP toxicology studies and approximately 1000 samples to support 2 clinical studies. Gyrolab™ xP had high run pass rates (≥83%) and high incurred sample reanalysis (ISR) pass rates (>94%). The maximum total error observed across all QC levels for a given assay was <30% for all six LBAs. High instrument response precision (CV ≤5%) was observed across compact discs (CDs), and methods were validated to use a single standard curve across multiple CDs within a Gyrolab™ xP run. Reduced bioanalysis timelines were achieved compared to standard manual plate-based methods, and methods were successfully transferred across testing labs, paving the way for this platform for use in late-stage clinical development.

Antibody-drug conjugate bioanalysis using LB-LC-MS/MS hybrid assays: strategies, methodology and correlation to ligand-binding assays.

BACKGROUND: Antibody-drug conjugates (ADCs) are complex drug constructs with multiple species in the heterogeneous mixture that contribute to their efficacy and toxicity. The bioanalysis of ADCs involves multiple assays and analytical platforms. METHODS: A series of ligand binding and LC-MS/MS (LB-LC-MS/MS) hybrid assays, through different combinations of anti-idiotype (anti-Id), anti-payload, or generic capture reagents, and cathepsin-B or trypsin enzyme digestion, were developed and evaluated for the analysis of conjugated-payload as well as for species traditionally measured by ligand-binding assays, total-antibody and conjugated-antibody. RESULTS & CONCLUSION: Hybrid assays are complementary or viable alternatives to ligand-binding assay for ADC bioanalysis and PK/PD modeling. The fit-for-purpose choice of analytes, assays and platforms and an integrated strategy from Discovery to Development for ADC PK and bioanalysis are recommended.

Validation of an integrated series of ligand-binding assays for the quantitative determination of antibody-drug conjugates in biological matrices.

BACKGROUND: The bioanalytical strategy for antibody-drug conjugates (ADC) includes multiple integrated measurements of pharmacologically relevant ADC. METHODS & RESULTS: Three ligand-binding assays were validated for the measurement of total antibody, active ADC and total ADC. Accuracy and precision demonstrate %bias from -8 to 14%, %CV from 3 to 11% and total error from 3 to 21%, with >98% samples meeting incurred sample reanalysis criteria. Each assay met stability, selectivity, dilutional integrity, carry over and specificity criteria with no interference from associated metabolite/impurity. Given the active ADC assay sensitivity to payload, active ADC was used to assess drug to antibody ratio. DISCUSSION & CONCLUSION: Implementation of a microfluidic automated platform enabled high throughput sample analysis of multiple analytes with minimal sample processing.

Current Challenges and Potential Opportunities for the Pharmaceutical Sciences to Make Global Impact: An FIP Perspective.

The chairs of each of the 8 Special Interest Groups of the Board of Pharmaceutical Sciences of the International Pharmaceutical Federation have compiled opinions with regard to major challenges for the pharmaceutical sciences over the next 5-10 years. Areas covered are drug design and discovery, natural products, formulation design and pharmaceutical technology, pharmacokinetics/pharmacodynamics and systems pharmacology, translational and personalized medicine, biotechnology, analytical sciences and quality control, and regulatory science.

Development and characterization of antibody reagents to assess anti-PEG IgG antibodies in clinical samples.

BACKGROUND: Polyethylene glycol (PEG) is a polymer that can be conjugated with therapeutic proteins. Monitoring anti-PEG antibodies in human subjects may be required as part of immunogenicity assessment. The lack of well-characterized anti-PEG reagents have limited our understanding of anti-PEG humoral response. RESULTS: Antibodies reactive to PEG were engineered with a human IgG1 Fc. Surface plasmon resonance and plate-based methods demonstrated that their binding was dependent on molecular weight (MW) of PEG. Specificity experiments using chemical analogs identified their specificity. CONCLUSION: Affinity, specificity and MW of PEG are critical characteristics that impact interactions of anti-PEG antibodies with PEG. These attributes especially MW of PEG and the assay formats may impact the ability to detect anti-PEG antibodies.

Development of a Generic Anti-PEG Antibody Assay Using BioScale's Acoustic Membrane MicroParticle Technology.

Immunogenicity testing for PEGylated biotherapeutics should include methods to detect both anti-protein and anti-PEG antibodies (anti-PEG). Although some methods have been published for the detection of anti-PEG antibodies, the information is incomplete and, in some cases, reagents used (such as Tween-20) are known to interfere with detection. This rapid communication describes the use of BioScale's Acoustic Membrane MicroParticle (AMMP®) technology using the ViBE® Workstation to measure anti-PEG antibodies in human serum samples. Briefly, a sample spiked with monoclonal human IgG anti-PEG antibody is diluted in buffer and incubated with paramagnetic beads coated with linear chain mPEG to capture anti-PEG antibodies. The complex is then captured on an acoustic membrane coated with Protein A. The change in mass on the membrane caused by the binding of the complex to the membrane results in a signal proportional to the mass of anti-PEG antibodies. The data indicate that an assay with a sensitivity of less than 1000 ng/mL for IgG is achievable. This level of sensitivity is better than current published reports on IgG anti-PEG antibody detection.