Protein LC-MS Tools for the Next Generation of Biotherapeutic Analyses from Preclinical and Clinical Serum.

LC-MS analysis of therapeutic antibodies and other biotherapeutics from in-life studies (e.g., serum/plasma) has evolved from simple peptide digestion to peptide mapping and intact mass monitoring. From more advanced analytical approaches, a deeper understanding as to the fate of the biotherapeutic in vivo is gained. Here, we examine the next generation of approaches to facilitate the most comprehensive understanding of large molecule drug fate in circulation. Three case studies are presented: (1) use of relative and absolute calibration curves for biotherapeutic quantitation from the same sample set; (2) top-down mass spectrometry applied to bioanalytical assays; (3) biotherapeutic protein complexes from serum analyzed by native protein MS. We anticipate that these approaches will be further adapted and applied by other research groups.

Determination of label efficiency and label degree of critical reagents by LC-MS and native MS.

Degree of labeling and label efficiency are key factors for optimal characterization of critical reagents that are used in ligand binding assays. Here, three case studies are shown demonstrating how liquid chromatography-mass spectrometry (LC-MS) was utilized to characterize critical reagents using three unique methodologies. Critical reagent batches were prepared for LC-MS analysis by use of: 20 mM dithiothreitol (DTT) (Case 1), rapid PNGaseF (Case 2), and a mobile phase diluent (Case 3). LC-MS was run at three different MS method conditions in each troubleshooting case specific for reduced IgG, intact IgG, and native LC-MS, respectively. Specified LC-MS methods based on sample type and configuration elucidated clear MS profiles, allowing for degree of labeling and label efficiencies to be calculated. Ultimately the LC-MS analyses were fine-tuned for critical reagent characterization, and practices for analyzing similar reagents in the future can be established.

Top-Down Characterization and Intact Mass Quantitation of a Monoclonal Antibody Drug from Serum by Use of a Quadrupole TOF MS System Equipped with Electron-Activated Dissociation.

Time-of-flight MS systems for biopharmaceutical and protein characterization applications may play an even more pivotal role in the future as biotherapeutics increase in drug pipelines and as top-down MS approaches increase in use. Here, a recently developed TOF MS system is examined for monoclonal antibody (mAb) characterization from serum samples. After immunocapture, purified drug material spiked into monkey serum or dosed for an in-life study is analyzed by top-down MS. While characterization aspects are a distinct advantage of the MS platform, MS system and software capabilities are also shown regarding intact protein quantitation. Such applications are demonstrated to help enable comprehensive protein molecule quantitation and characterization by use of TOF MS instrumentation.

An antibody-free platform for multiplexed, sensitive quantification of protein biomarkers in complex biomatrices.

Sensitive, multiplexed protein quantification remains challenging despite recent advancements in LC-MS assays for targeted protein biomarker quantification. High-sensitivity protein biomarker measurements usually require immuno-affinity enrichment of target protein; a process which is highly dependent on capture reagent and limited in capability to measure multiple analytes. Herein, we report a novel antibody-free platform, which measures multiple biomarkers from complex matrices employing a strategically optimized solid-phase extraction cleanup and orthogonal multidimensional LC-MS. Eight human protein biomarkers with different specifications were spiked into canine plasma as a model investigation system. The developed strategy achieved the desired sensitivity, robustness, and throughput via the following steps: (1) post digestion mixed-mode cation exchange-reverse phase SPE enrichment cleaned up the sample initially; (2) rapid, high-pH peptide fractionation further eliminated background components efficiently while selectively enriched signature peptides (SP) to provide sufficient sensitivity for multiple targets; and (3) trapping-micro-LC-MS analysis delivered high sensitivity comparable to a nano-LC-MS method but with much better robustness and throughput for the final analysis. Compared with a conventional LC-MS assay with direct protein digestion and limited clean-up, analysis with this antibody-free platform improved the LLOQ by 1-2 orders of magnitude for the eight protein biomarkers, reaching as low as 5 ng/mL in plasma, with feasible robustness and throughput. This platform was applied for the quantification of biomarkers of respiratory conditions in patients with various lung diseases, demonstrating real-world applicability.

2021 White Paper on Recent Issues in Bioanalysis: Mass Spec of Proteins, Extracellular Vesicles, CRISPR, Chiral Assays, Oligos; Nanomedicines Bioanalysis; ICH M10 Section 7.1; Non-Liquid & Rare Matrices; Regulatory Inputs (Part 1A - Recommendations on Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC & Part 1B - Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine).

The 15th edition of the Workshop on Recent Issues in Bioanalysis (15th WRIB) was held on 27 September to 1 October 2021. Even with a last-minute move from in-person to virtual, an overwhelmingly high number of nearly 900 professionals representing pharma and biotech companies, contract research organizations (CROs), and multiple regulatory agencies still eagerly convened to actively discuss the most current topics of interest in bioanalysis. The 15th WRIB included 3 Main Workshops and 7 Specialized Workshops that together spanned 1 week in order to allow exhaustive and thorough coverage of all major issues in bioanalysis, biomarkers, immunogenicity, gene therapy, cell therapy and vaccines. Moreover, in-depth workshops on biomarker assay development and validation (BAV) (focused on clarifying the confusion created by the increased use of the term "Context of Use - COU"); mass spectrometry of proteins (therapeutic, biomarker and transgene); state-of-the-art cytometry innovation and validation; and, critical reagent and positive control generation were the special features of the 15th edition. This 2021 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 2021 edition of this comprehensive White Paper has been divided into three parts for editorial reasons. This publication (Part 1A) covers the recommendations on Endogenous Compounds, Small Molecules, Complex Methods, Regulated Mass Spec of Large Molecules, Small Molecule, PoC. Part 1B covers the Regulatory Agencies' Inputs on Bioanalysis, Biomarkers, Immunogenicity, Gene & Cell Therapy and Vaccine. Part 2 (ISR for Biomarkers, Liquid Biopsies, Spectral Cytometry, Inhalation/Oral & Multispecific Biotherapeutics, Accuracy/LLOQ for Flow Cytometry) and Part 3 (TAb/NAb, Viral Vector CDx, Shedding Assays; CRISPR/Cas9 & CAR-T Immunogenicity; PCR & Vaccine Assay Performance; ADA Assay Comparabil ity & Cut Point Appropriateness) are published in volume 14 of Bioanalysis, issues 10 and 11 (2022), respectively.

Intact Protein Mass Spectrometry for Therapeutic Protein Quantitation, Pharmacokinetics, and Biotransformation in Preclinical and Clinical Studies: An Industry Perspective.

Recent advancements in immunocapture methods and mass spectrometer technology have enabled intact protein mass spectrometry to be applied for the characterization of antibodies and other large biotherapeutics from in-life studies. Protein molecules have not been traditionally studied by intact mass or screened for catabolites in the same manner as small molecules, but the landscape has changed. Researchers have presented methods that can be applied to the drug discovery and development stages, and others are exploring the possibilities of the new approaches. However, a wide variety of options for assay development exists without clear recommendation on best practice, and data processing workflows may have limitations depending on the vendor. In this perspective, we share experiences and recommendations for current and future application of mass spectrometry for biotherapeutic molecule monitoring from preclinical and clinical studies.

Intact mAb LC-MS for drug concentration from pre-clinical studies: bioanalytical method performance and in-life samples.

Background: Antibody biotherapeutic measurement from pharmacokinetic studies has not been traditionally based on intact molecular mass as is the case for small molecules. However, recent advancements in protein capture and mass spectrometer technology have enabled intact mass detection and quantitation for dosed biotherapeutics. A bioanalytical method validation is part of the regulatory requirement for sample analysis to determine drug concentration from in-life study samples. Results/methodology: Here, an intact protein LC-MS assay is subjected to mock bioanalytical method validation, and unknown samples are compared between intact protein LC-MS and established bioanalytical assay formats: Ligand-binding assay and peptide LC-MS/MS. Discussion/conclusion: Results are presented from the intact and traditional bioanalytical method evaluations, where the in-life sample concentrations were comparable across method types with associated data analyses presented. Furthermore, for intact protein LC-MS, modification monitoring and evaluation of data processing parameters is demonstrated.

Antibody Subunit LC-MS Analysis for Pharmacokinetic and Biotransformation Determination from In-Life Studies for Complex Biotherapeutics.

Complex biotherapeutics present challenges from drug discovery, screening, and development perspectives. While monoclonal antibody drugs are not monitored for metabolites in the same manner as small molecules, biotherapeutics such as fusion proteins, antibody-drug conjugates, or bispecific antibodies may undergo biotransformation (such as clipping, deamidation, or oxidation) in vivo, resulting in catabolites that can have a direct impact on drug safety or efficacy. Here antibody subunit LC-MS is utilized for evaluation of two classes of complex biotherapeutics: an antibody-drug conjugate and a mAb-fusion biotherapeutic. Pharmacokinetic concentration, biotransformation, and DAR data are collectively presented using the subunit LC-MS approach for the two molecules, and the methods shared in detail can be applied to any humanized IgG1 mAb biotherapeutic for preclinical study support. Overall, the data generated from antibody LC-MS analyses can provide key information in early phase development and deliver multiple study end points with a single data set.

Biotherapeutic Antibody Subunit LC-MS and Peptide Mapping LC-MS Measurements to Study Possible Biotransformation and Critical Quality Attributes In Vivo.

Biotransformation monitoring involves tracking drug modification occurring during in-life studies. Critical Quality Attribute monitoring from forced degraded drug material or in-life sample sets can provide an in-depth assessment of product quality for support in early- or late-stage drug development. For Critical Quality Attribute analysis, biotherapeutic monoclonal antibody (mAb) subunit analysis and peptide mapping liquid chromatography-mass spectrometry (LC-MS) approaches are used, although typically from an in vitro setting (e.g., formulation buffer) not involving biological samples or material. Here, samples from a high-dose rat study (in vivo) are subjected to analysis by ligand binding assay, mAb subunit LC-MS, and peptide mapping by LC-MS. Taken together, data from the 3 analytical approaches provide information regarding drug concentration in circulation, biotransformation, and biotherapeutic drug product quality. The concept of a multitier workflow for preclinical or clinical sample sets can be applied to other biotherapeutic mAb products such as bispecific mAbs, fusions proteins, or antibody-drug conjugates.

Review of approaches and examples for monitoring biotransformation in protein and peptide therapeutics by MS.

Biotherapeutic drugs have emerged in quantity in pharmaceutical pipelines, and increasingly diverse biomolecules are progressed through preclinical and clinical development. As purification, separation, mass spectrometer detection and data processing capabilities improve, there is opportunity to monitor drug concentration by traditional ligand-binding assay or MS measurement and to monitor metabolism, catabolism or other biomolecular mass variants present in circulation. This review highlights approaches and examples of monitoring biotransformation of biotherapeutics by MS as these techniques are poised to add value to drug development in years to come. The increased use of such approaches, and the successful quantitation of biotherapeutic structural modifications, will provide insightful data for the benefit of both researchers and patients.

Drug monitoring by volumetric absorptive microsampling: method development considerations to mitigate hematocrit effects.

AIM: GSKA is a compound that was in development in clinical trials. A bioanalysis method to quantify GSKA using volumetric absorptive microsampling (VAMS) was developed and hematocrit (HCT) related assay bias was investigated. METHODOLOGY: After accurate sampling of 10 µl blood, VAMS tips were air dried approximately 18 h and desorbed by an aqueous solution containing internal standard. The recovered blood underwent liquid-liquid extraction in ethyl acetate to minimize matrix suppression. Assay accuracy, precision, linearity, carryover, selectivity, recovery, matrix effects, HCT effects and long-term quality control stability were evaluated. CONCLUSION: HCT-related assay bias was minimized in 30-60% blood HCT range, and all validation parameters met acceptance criteria. The method is suitable for quantitative analysis of GSKA in human blood.

Toward best practices in data processing and analysis for intact biotherapeutics by MS in quantitative bioanalysis.

AIM: Typically, quantitation of biotherapeutics from biological matrices by LC-MS is based on a surrogate peptide approach to determine molecule concentration. Recent efforts have focused on quantitation of the intact protein molecules or larger mass subunits of monoclonal antibodies. To date, there has been limited guidance for large or intact protein mass quantitation for quantitative bioanalysis. METHODOLOGY: Intact- and subunit-level analyses of biotherapeutics from biological matrices are performed at 12-25 kDa mass range with quantitation data presented. RESULTS: Linearity, bias and other metrics are presented along with recommendations made on the viability of existing quantitation approaches. CONCLUSION: This communication is intended to start a discussion around intact protein data analysis and processing, recognizing that other published contributions will be required.

A whole-molecule immunocapture LC-MS approach for the in vivo quantitation of biotherapeutics.

AIM: Large-molecule biotherapeutic quantitation in vivo by LC-MS has traditionally relied on enzymatic digestion followed by quantitation of a 'surrogate peptide' to infer whole-molecule concentration. MS methods presented here measure the whole molecule and provide a platform to better understand the various circulating drug forms by allowing for variant quantitation. RESULTS: An immunocapture LC-MS method for quantitation of a biotherapeutic monoclonal antibody from human plasma is presented. Sensitivity, precision and accuracy for each molecular portion are presented along with an example of glycoform variant quantitation. CONCLUSION: The method is presented as a basic platform to be further developed for Good Practice (GxP) applications, critical quality attribute analysis or general understanding of molecular forms present as required for the wide range of drug development processes.

Application of high-resolution MS for development of peptide and large-molecule drug candidates.

BACKGROUND: For quantitative bioanalysis utilizing MS, the instrument of choice is typically a triple quadruple mass spectrometer. However, advances in high-resolution MS have allowed sensitivity and dynamic ranges to approach that of triple quadrupole instruments. RESULTS: A matrix-free protein digest, a digested therapeutic protein and the intact peptide therapeutic liraglutide were each analyzed on high-resolution and triple quadrupole mass spectrometers with data compared. Samples from a mouse PK study with liraglutide were analyzed using the two different instruments, and equivalent PK exposure data were demonstrated. CONCLUSION: High-resolution and triple quadrupole mass spectrometers can generate data resulting in identical PK parameters from an in-life sample set, thus giving confidence in either technique in support of biotherapeutic PK exposure studies.

Mechanism of Inactivation of GABA Aminotransferase by (E)- and (Z)-(1S,3S)-3-Amino-4-fluoromethylenyl-1-cyclopentanoic Acid.

When γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian central nervous system, falls below a threshold level, seizures occur. One approach to raise GABA concentrations is to inhibit GABA aminotransferase (GABA-AT), a pyridoxal 5'-phosphate-dependent enzyme that degrades GABA. We have previously developed (1S,3S)-3-amino-4-difluoromethylene-1-cyclopentanoic acid (CPP-115), which is 186 times more efficient in inactivating GABA-AT than vigabatrin, the only FDA-approved inactivator of GABA-AT. We also developed (E)- and (Z)-(1S,3S)-3-amino-4-fluoromethylenyl-1-cyclopentanoic acid (1 and 2, respectively), monofluorinated analogs of CPP-115, which are comparable to vigabatrin in inactivating GABA-AT. Here, we report the mechanism of inactivation of GABA-AT by 1 and 2. Both produce a metabolite that induces disruption of the Glu270-Arg445 salt bridge to accommodate interaction between the metabolite formyl group and Arg445. This is the second time that Arg445 has interacted with a ligand and is involved in GABA-AT inactivation, thereby confirming the importance of Arg445 in future inactivator design.

Quantitative measurement of intact alpha-synuclein proteoforms from post-mortem control and Parkinson's disease brain tissue by intact protein mass spectrometry.

A robust top down proteomics method is presented for profiling alpha-synuclein species from autopsied human frontal cortex brain tissue from Parkinson's cases and controls. The method was used to test the hypothesis that pathology associated brain tissue will have a different profile of post-translationally modified alpha-synuclein than the control samples. Validation of the sample processing steps, mass spectrometry based measurements, and data processing steps were performed. The intact protein quantitation method features extraction and integration of m/z data from each charge state of a detected alpha-synuclein species and fitting of the data to a simple linear model which accounts for concentration and charge state variability. The quantitation method was validated with serial dilutions of intact protein standards. Using the method on the human brain samples, several previously unreported modifications in alpha-synuclein were identified. Low levels of phosphorylated alpha synuclein were detected in brain tissue fractions enriched for Lewy body pathology and were marginally significant between PD cases and controls (p = 0.03).

Nano-LC FTICR tandem mass spectrometry for top-down proteomics: routine baseline unit mass resolution of whole cell lysate proteins up to 72 kDa.

Current high-throughput top-down proteomic platforms provide routine identification of proteins less than 25 kDa with 4-D separations. This short communication reports the application of technological developments over the past few years that improve protein identification and characterization for masses greater than 25 kDa. Advances in separation science have allowed increased numbers of proteins to be identified, especially by nanoliquid chromatography (nLC) prior to mass spectrometry (MS) analysis. Further, a goal of high-throughput top-down proteomics is to extend the mass range for routine nLC MS analysis up to 80 kDa because gene sequence analysis predicts that ~70% of the human proteome is transcribed to be less than 80 kDa. Normally, large proteins greater than 50 kDa are identified and characterized by top-down proteomics through fraction collection and direct infusion at relatively low throughput. Further, other MS-based techniques provide top-down protein characterization, however at low resolution for intact mass measurement. Here, we present analysis of standard (up to 78 kDa) and whole cell lysate proteins by Fourier transform ion cyclotron resonance mass spectrometry (nLC electrospray ionization (ESI) FTICR MS). The separation platform reduced the complexity of the protein matrix so that, at 14.5 T, proteins from whole cell lysate up to 72 kDa are baseline mass resolved on a nano-LC chromatographic time scale. Further, the results document routine identification of proteins at improved throughput based on accurate mass measurement (less than 10 ppm mass error) of precursor and fragment ions for proteins up to 50 kDa.

Robust analysis of the yeast proteome under 50 kDa by molecular-mass-based fractionation and top-down mass spectrometry.

As the process of top-down mass spectrometry continues to mature, we benchmark the next installment of an improving methodology that incorporates a tube-gel electrophoresis (TGE) device to separate intact proteins by molecular mass. Top-down proteomics is accomplished in a robust fashion to yield the identification of hundreds of unique proteins, many of which correspond to multiple protein forms. The TGE platform separates 0-50 kDa proteins extracted from the yeast proteome into 12 fractions prior to automated nanocapillary LC-MS/MS in technical triplicate. The process may be completed in less than 72 h. From this study, 530 unique proteins and 1103 distinct protein species were identified and characterized, thus representing the highest coverage to date of the Saccharomyces cerevisiae proteome using top-down proteomics. The work signifies a significant step in the maturation of proteomics based on direct measurement and fragmentation of intact proteins.