Bioanalytical LC–MS/MS of protein-based biopharmaceuticals

Proteomics and Its Current Application in Biomedical Area: Concise Review

Biomedical researchers tirelessly seek cutting-edge technologies to advance disease diagnosis, drug discovery, and therapeutic interventions, all aimed at enhancing human and animal well-being. Within this realm, proteomics stands out as a pivotal technology, focusing on extensive studies of protein composition, structure, function, and interactions. Proteomics, with its subdivisions of expression, structural, and functional proteomics, plays a crucial role in unraveling the complexities of biological systems. Various sophisticated techniques are employed in proteomics, including polyacrylamide gel electrophoresis, mass spectrometry analysis, NMR spectroscopy, protein microarray, X-ray crystallography, and Edman sequencing. These methods collectively contribute to the comprehensive understanding of proteins and their roles in health and disease. In the biomedical field, proteomics finds widespread application in cancer research and diagnosis, stem cell studies, and the diagnosis and research of both infectious and noninfectious diseases. In addition, it plays a pivotal role in drug discovery and the emerging frontier of personalized medicine. The versatility of proteomics allows researchers to delve into the intricacies of molecular mechanisms, paving the way for innovative therapeutic approaches. As infectious and noninfectious diseases continue to emerge and the field of biomedical research expands, the significance of proteomics becomes increasingly evident. Keeping abreast of the latest developments in proteomics applications becomes paramount for the development of therapeutics, translational research, and study of diverse diseases. This review aims to provide a comprehensive overview of proteomics, offering a concise outline of its current applications in the biomedical domain. By doing so, it seeks to contribute to the understanding and advancement of proteomics, emphasizing its pivotal role in shaping the future of biomedical research and therapeutic interventions.

Rapid isolation of anti-idiotype aptamers for quantification of human monoclonal antibodies against SARS-CoV-2 spike protein

Therapeutic antibodies that block viral entry have already proven to be important, first line drugs for treatments of viral infections. In the case of SARS-CoV-2, combinations of multiple therapeutic antibodies may need to be rapidly identified and formulated in a way that blocks each new, predominant variant of the virus. For efficient introduction of any new antibody combination into patients, it is important to be able to monitor patient-specific pharmacokinetics of individual antibodies, which would include the time course of their specific capacity to block the viral spike proteins. Here, we present three examples of microfluidic-based rapid isolation of companion reagents useful for establishing combination antibody therapies. These reagents are specific three-dimensional imprints of variable regions of individual human monoclonal antibodies against the -spike protein of SARS-CoV-2 virus in the form of oligonucleotide-based ligands (aptamers). We implement these anti-idiotypic aptamers as bioreceptors in graphene-based field-effect transistor sensors to accomplish label free, rapid, and sensitive detection of matching antibodies within minutes. Through this work we have demonstrated the general applicability of anti-idiotype aptamers as capture reagents in quantification of active forms of monoclonal antibodies in complex biological mixtures.

Rapid and simple quantification of belimumab in human plasma using ultra-high performance liquid chromatography with tandem mass spectrometry

OBJECTIVE

Belimumab is a monoclonal antibody against the B-lymphocyte stimulating factor and is approved for the treatment of patients with systemic lupus erythematosus (SLE) not responding adequately to existing therapies. In this study, we established and validated an assay for quantifying belimumab in human plasma.

METHODS

From the peptides generated by trypsin digestion of belimumab, in silico analysis was used to search for unique peptides to determine the surrogate peptides. Samples were trypsin digested, pretreated with solid phase extraction, and analyzed by ultra-high performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) to quantify the surrogate peptide in the samples. The assay was validated according to the Food and Drug Administration (FDA) bioanalytical method validation guidance. We used the established assay to quantify plasma belimumab concentrations in two SLE patients treated with belimumab.

RESULTS

Among the unique peptides identified by the in silico analysis, the peptide with the best peak shape when measured by UHPLC-MS/MS was selected as the surrogate peptide. The validation results of this assay met the acceptable criteria recommended by the FDA guidance. The lower limit of quantification (LLOQ) for belimumab was 2 µg/mL. Recovery rates and matrix effects when corrected for internal standards were 91.5-114.3 % and 96.9-108.4 %, respectively. Plasma concentrations of belimumab were measured in 12 samples from two belimumab-treated SLE patients. All concentrations were within the calibration range.

CONCLUSIONS

We have established and validated a method for measuring plasma belimumab concentrations using UHPLC/MS-MS. By measuring plasma belimumab concentrations in more patients, this method is expected to contribute to appropriate use of belimumab.

Quantitative analysis of therapeutic proteins in biological fluids: recent advancement in analytical techniques

Pharmaceutical application of therapeutic proteins has been continuously expanded for the treatment of various diseases. Efficient and reliable bioanalytical methods are essential to expedite the identification and successful clinical development of therapeutic proteins. In particular, selective quantitative assays in a high-throughput format are critical for the pharmacokinetic and pharmacodynamic evaluation of protein drugs and to meet the regulatory requirements for new drug approval. However, the inherent complexity of proteins and many interfering substances presented in biological matrices have a great impact on the specificity, sensitivity, accuracy, and robustness of analytical assays, thereby hindering the quantification of proteins. To overcome these issues, various protein assays and sample preparation methods are currently available in a medium- or high-throughput format. While there is no standard or universal approach suitable for all circumstances, a liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay often becomes a method of choice for the identification and quantitative analysis of therapeutic proteins in complex biological samples, owing to its high sensitivity, specificity, and throughput. Accordingly, its application as an essential analytical tool is continuously expanded in pharmaceutical R&D processes. Proper sample preparation is also important since clean samples can minimize the interference from co-existing substances and improve the specificity and sensitivity of LC-MS/MS assays. A combination of different methods can be utilized to improve bioanalytical performance and ensure more accurate quantification. This review provides an overview of various protein assays and sample preparation methods, with particular emphasis on quantitative protein analysis by LC-MS/MS.

Quantitative bioanalysis of proteins by digestion and LC-MS/MS: the use of multiple signature peptides

The use of multiple signature peptides for the quantification of proteins by digestion and LC-MS/MS is reviewed and evaluated here. A distinction is made based on the purpose of the use of multiple peptides: confirmation of the protein concentration, discrimination between different protein forms or species and in vivo biotransformation. Most reports that describe methods with at least two peptides use these for confirmation, but it is not always mentioned how the peptides are used and how possible differences in concentration between the peptides are handled. Differences in concentration are often reported in the case of monitoring different protein forms or in vivo biotransformation, and this offers insight into the biological fate of the protein.

Assessing the hydrophobicity of glycopeptides using reversed-phase liquid chromatography and tandem mass spectrometry

Retention time is one of the most important parameters that has been widely used to demonstrate the separation results obtained from liquid chromatography (LC) platforms. However, retention time can shift when samples are tested with different instruments and laboratories, which hinders the identification process of analytes when comparing data collected from different LC systems. To address this problem, hydrophobicity index was introduced for retention time normalization of the glycopeptides separated by reversed-phase LC (RPLC). Tandem MS was used for the detection and identification of glycopeptides. In addition, the influence of different types of glycans on the hydrophobicity of peptide backbones was studied by comparing the retention time of glycopeptides with their non-glycosylated counterparts. The hydrophobicity of tryptic digested glycopeptides derived from model glycoproteins, including bovine fetuin, α1-acid glycoprotein, and haptoglobin from human plasma, were evaluated based on the hydrophobicity index of the standard peptides from a peptide retention time calibration mixture. The reduction of hydrophobicity of multiple peptide backbones was observed due to the hydrophilic glycan structures. By comparing the hydrophobicity index of glycopeptides collected from different time and instruments, the day-to-day and lab-to-lab comparisons suggested high reliability and reproducibility of this approach. The RSD% of hydrophobicity index from inter-lab experiments was 1.2%, while the RSD% of retention time was 5.1%. Then, the applications of this method were demonstrated on complex glycopeptide samples extracted from human blood serum. The hydrophobicity index can be applied to address the retention time shift when using different instruments, thereby boosting confidence of the characterization of glycopeptides.

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.

An antibody-free LC-MS/MS method for the quantification of sex hormone binding globulin in human serum and plasma

OBJECTIVES

Sex hormone binding globulin (SHBG) is a hormone binding protein which plays an important role in regulating the transport and availability of biologically active androgens and estradiol to target cells and used to calculate free testosterone concentrations.

METHODS

A liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed, featuring an albumin removal step followed by a tryptic digestion. After a reduction step with dithiothreitol and alkylation with iodoacetamide three signature peptides were used for the quantification of SHBG.

RESULTS

The method enables the quantification of serum and plasma SHBG over the clinically relevant range of 200-20,000 ng/mL and was validated according to the most recent guidelines. The LC-MS/MS method correlates well with the Abbott Alinity immunoassay (R2>0.95), but the LC-MS/MS results are on average 16-17% lower than the immunoassay results, which is consistent for all three signature peptides.

CONCLUSIONS

The LC-MS/MS method which includes an albumin depletion step allows quantification of SHBG in serum and plasma without an immunocapture step at clinically relevant SHBG levels, thus contributing to better lab-to-lab consistency of results.

Development of an Anti-Idiotype Aptamer-Based Electrochemical Sensor for a Humanized Therapeutic Antibody Monitoring

Therapeutic monoclonal antibodies (mAbs) are currently the most effective medicines for a wide range of diseases. Therefore, it is expected that easy and rapid measurement of mAbs will be required to improve their efficacy. Here, we report an anti-idiotype aptamer-based electrochemical sensor for a humanized therapeutic antibody, bevacizumab, based on square wave voltammetry (SWV). With this measurement procedure, we were able to monitor the target mAb within 30 min by employing the anti-idiotype bivalent aptamer modified with a redox probe. A fabricated bevacizumab sensor achieved detection of bevacizumab from 1–100 nM while eliminating the need for free redox probes in the solution. The feasibility of monitoring biological samples was also demonstrated by detecting bevacizumab in the diluted artificial serum, and the fabricated sensor succeeded in detecting the target covering the physiologically relevant concentration range of bevacizumab. Our sensor contributes to ongoing efforts towards therapeutic mAbs monitoring by investigating their pharmacokinetics and improving their treatment efficacy.

Simultaneous quantification of thalidomide, lenalidomide and pomadomide in plasma by LC-MS/MS

OBJECTIVE

To develop a new method for quantitatively analyzing three immunomodulators (thalidomide, lenalidomide and pomadomide) by liquid chromatography tandem mass spectrometry (LC-MS/MS).

METHODS

Using thalidomide-d4 as internal standard, the three analytes were separated on Agilent Zorbax SB-C18(2.1 mm × 100 mm, 3.5 μm, Agilent, USA) column and monitored in multiple reactions monitoring mode in Agilent G6460A triple quadrupole mass spectrometer operating in positive ionization mode. The sample was pretreated by protein precipitation using methanol at 3-fold volume to sample. The mobile phase was comprised of 0.1% formic acid in water (phase A) and acetonitrile (phase B) and was delivered in gradient elution program. The flow rate was 0.3 mL/min, and the injection volume was 5 μL.

RESULTS

The accuracy and stability of the method are within ±15.0%, and the precision is not >15.0%. The recoveries were 85.04% ∼ 119.07%, and the matrix effect was 73.68% ∼ 116.75%. Specificity, linearity, LLOQ, carry-over and dilution were all in line with the requirements of pharmacopeia and guidelines. The peak concentrations of thalidomide, lenalidomide shows huge inter-individual differences.

CONCLUSIONS

This newly developed method was sensitive, simple, and robust and can be used in therapeutic drug monitoring of three immunomodulators in multiple myeloma patients.

Biotransformation of Trastuzumab and Pertuzumab in Breast Cancer Patients Assessed by Affinity Enrichment and Ion-Exchange Chromatography

Therapeutic proteins (TPs) are known to be heterogeneous due to modifications that occur during the production process and storage. Modifications may also occur in TPs after their administration to patients due to in vivo biotransformation. Ligand binding assays, which are widely used in the bioanalysis of TPs in body fluids, are typically unable to distinguish such modifications. Liquid chromatography coupled to mass spectrometry is being increasingly used to study modifications in TPs, but its use to study in vivo biotransformation has been limited until now. We present a novel approach that combines affinity enrichment using Affimer reagents with ion-exchange chromatography (IEX) to analyze charge variants of the TPs trastuzumab and pertuzumab in plasma of patients undergoing therapy for HER2-positive breast cancer. Affimer reagents were immobilized via engineered Cys tags to maleimide beads, and the TPs were eluted under acidic conditions followed by rapid neutralization. The enriched TPs were analyzed by cation-exchange chromatography (IEX) using pH-gradient elution, resulting in the separation of about 20 charge variants for trastuzumab and about five charge variants for pertuzumab. A comparison between in vitro stressed TPs spiked into plasma, and TPs enriched from patient plasma showed that the observed profiles were highly similar. This indicates that in vitro stress testing in plasma can mimic the situation in patient plasma, as far as the generation of charge variants is concerned. SIGNIFICANCE STATEMENT: This research attempts to elucidate the modifications that occur in therapeutic proteins (TPs) after they have been administered to patients. This is important because there is little knowledge about the fate of TPs in this regard, and certain modifications could affect their efficiency. Our results show that the modifications discovered are most likely due to a chemical process and are not patient specific.

LC-MS/MS method for the quantitation of serum tocilizumab in rheumatoid arthritis patients using rapid tryptic digestion without IgG purification

The quantitation of serum tocilizumab using liquid chromatography tandem-mass spectrometry (LC-MS/MS) method has not been widely applied in clinical settings because of its time-consuming and costly sample pretreatments. The present study aimed to develop a validated LC-MS/MS method for detecting serum tocilizumab by utilizing immobilized trypsin without an immunoglobulin G purification step and evaluate its applicability in the treatment of rheumatoid arthritis (RA) patients administered intravenously or subcutaneously with tocilizumab. The tocilizumab-derived signature peptide was deciphered using a nano-LC system coupled to a hybrid quadrupole-orbitrap mass spectrometer. The serum tocilizumab was rapidly digested by immobilized trypsin for 30 min. The chromatographic peak of the signature peptide and that of the internal standard were separated from the serum digests for a total run time of 15 min. The calibration curve of serum tocilizumab concentration was linear with a range of 2-200 μg/mL. The intra- and inter-day accuracy and relative standard deviation (RSD) were 90.7%-109.4% and <10%, respectively. The serum tocilizumab concentrations in the RA patients receiving intravenous and subcutaneous injections were 5.8-28.9 and 2.4-63.5 μg/mL, respectively. The serum tocilizumab concentrations using the current method positively correlated with those using the enzyme-linked immunosorbent assay, although a systematic error was observed between these methods. In conclusion, a validated LC-MS/MS method with minimal sample pretreatments for monitoring serum tocilizumab concentrations in RA patients was developed.

Investigation of native and aggregated therapeutic proteins in human plasma with asymmetrical flow field-flow fractionation and mass spectrometry

Physiochemical degradation of therapeutic proteins in vivo during plasma circulation after administration can have a detrimental effect on their efficacy and safety profile. During drug product development, in vivo animal studies are necessary to explore in vivo protein behaviour. However, these studies are very demanding and expensive, and the industry is working to decrease the number of in vivo studies. Consequently, there is considerable interest in the development of methods to pre-screen the behaviour of therapeutic proteins in vivo using in vitro analysis. In this work, asymmetrical flow field-flow fractionation (AF4) and liquid chromatography-mass spectrometry (LC-MS) were combined to develop a novel analytical methodology for predicting the behaviour of therapeutic proteins in vivo. The method was tested with two proteins, a monoclonal antibody and a serum albumin binding affibody. After incubation of the proteins in plasma, the method was successfully used to investigate and quantify serum albumin binding, analyse changes in monoclonal antibody size, and identify and quantify monoclonal antibody aggregates.

Development and validation of an LC-MS/MS method for the quantification of fascin proteins in human serum

Background: Fascin is an actin-bundling protein that has been linked to tumor cell migration, invasion, metastasis, disease progression and mortality, thus serving as a novel cancer biomarker. Bioanalytical methods to measure fascin in biological matrices are sparsely reported, while accurate quantitation of fascin levels may lend support for fascin as a promising therapeutic target. Method: An LC-MS/MS-based method involving protein precipitation, enzymatic digestion and solid phase extraction was developed and validated for the quantitation of fascin in human serum. Linearity over a calibration range of 5-500 ng/ml with a LLOQ of 5 ng/ml, great accuracy and precision, excellent parallelism as well as high extraction recovery were achieved. Conclusion: This method provides a valuable tool for anticancer drug development and cancer treatment.

The Pharmacokinetics in Mice and Cell Uptake of Thymus Immunosuppressive Pentapeptide Using LC-MS/MS Analysis

Thymus immunosuppressive pentapeptide (TIPP) is a novel anti-inflammatory peptide with high efficacy and low toxicity. This study aims to establish a selective LC-MS/MS method for analyzing the analyte TIPP in biological samples, laying the foundation for further PK and PD studies of TIPP. Protein precipitation was conducted in acetonitrile supplemented with 2% formic acid and 25 mg/mL dithiothreitol as a stabilizer, which was followed by backwashing the organic phase using dichloromethane. The chromatographic separation of TIPP was achieved on a C18 column with a gradient elution method. During positive electrospray ionization, TIPP was analyzed via multiple-reaction monitoring. The linear relationships between the concentration of TIPP and peak area in murine plasma cell lysates, supernatants, and the final cell rinse PBS were established within the ranges of 20−5000 ng/mL, 1−200 ng/mL, 10−200 μg/mL, and 0.1−20 ng/mL, respectively (r2 > 0.99). Validated according to U.S. FDA guidelines, the proposed method was proved to be acceptable. Such a method had been successfully applied to investigate the pharmacokinetics of TIPP in mice via subcutaneous injection. The plasma half-life in mice was 5.987 ± 1.824 min, suggesting that TIPP is swiftly eliminated in vivo. The amount of TIPP uptake by RBL-2H3 cells was determined using this method, which was also visually verified by confocal. Furthermore, the effective intracellular concentration of TIPP was deduced by comparing the intracellular concentration of TIPP and degrees of inflammation, enlightening further investigation on the intracellular target and mechanism of TIPP.

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.

Review of the Clinical Pharmacokinetics, Efficacy and Safety of Pembrolizumab

BACKGROUND

Treatment of various types of cancer has been improved significantly with the discovery of biologic drugs that act as immune checkpoint inhibitors (ICIs). Pembrolizumab is a humanized monoclonal anti-PD-1 antibody currently approved for the treatment of a wide range of tumors, with more indications still being investigated in ongoing clinical trials.

OBJECTIVE

The aim of this paper is to present all currently available data regarding pembrolizumab pharmacokinetic and pharmacodynamic characteristics. Also, the possibility of using predicative biomarkers to monitor patients during cancer treatment is discussed.

METHODS

Database research was carried out (PubMed, ScienceDirect). Information was gathered from original articles, the European Medicines Agency datasheets and results from clinical trials.

RESULTS

This review summarizes present-day knowledge about the pharmacokinetics, different modeling approaches and dosage regimens, efficacy and safety of pembrolizumab and therapeutic monitoring of disease progression.

CONCLUSION

This review points out consistent pharmacokinetic characteristics of pembrolizumab in various cancer patients, the lack of pharmacokinetic-pharmacodynamic/outcome relationships, the need of adequate biomarkers predicting treatment success. Hence, there is a clear necessity for more data and experience in order to optimize pembrolizumab treatment for each individual patient.

Development of a DNA aptamer that binds to the complementarity-determining region of therapeutic monoclonal antibody and affinity improvement induced by pH-change for sensitive detection

Therapeutic monoclonal antibodies (mAbs) are successful biomedicines; however, evaluation of their pharmacokinetics and pharmacodynamics demands highly specific discrimination from human immunoglobulin G naturally present in the blood. Here, we developed a novel anti-idiotype aptamer (termed A14#1) with extraordinary specificity against the anti-vascular endothelial growth factor therapeutic mAb, bevacizumab. Structural analysis of the antibody-aptamer complex showed that several bases of A14#1 recognized only the complementarity determining region (CDR) of bevacizumab, thereby contributing to its extraordinary specificity. As the CDR of bevacizumab is predicted to be highly positively charged under mildly acidic conditions and that DNA is negatively charged, the affinity of A14#1 to bevacizumab markedly increased at pH 4.7 (K_D = 44 pM) than at pH 7.4 (K_D = 12 nM). A14#1-based electrochemical detection method capable of detecting 31 pM of bevacizumab at pH 4.7 was thus developed. A14#1 could be potentially useful for therapeutic drug measurement as a novel ligand of bevacizumab.

Intact Mass Quantitation of Therapeutic Antibodies for Pharmacokinetic Studies Using Immuno-Purification

The quantitation of therapeutic antibodies by mass spectrometry often utilizes a surrogate peptide approach following enzymatic digestion of the antibody. Although this approach has been widely adopted, it is labor intensive with limited throughput in most instances. In addition, this approach can pose challenges when attempting to infer details such as quantity and modification state of the intact analyte. Recent enhancements in instrumentation and sample preparation have enabled quantitation through mass spectrometry detection of the intact protein circumnavigating many limitations of the surrogate peptide approach. Presented here is a method for quantitative analysis of therapeutic monoclonal antibodies (mAb) at the fully intact level in a complex pharmacokinetic study. This methodology yielded sensitivity down to 0.1μg/mL from 30μL of a biological sample volume to be utilized across multiple preclinical species without the need for pooling.

THE IMPACT OF COLORECTAL CHROMENDOSCOPY WITH ENHANCED MUCOSAL IMAGING ON ADENOMA MISS RATE IN SCREENING COLONOSCOPY

BACKGROUND

Colonoscopy is the gold standard for the diagnosis and treatment of adenomas. It is related with decreased colorectal cancer incidence and mortality. However, an important problem is missed colorectal adenoma. All efforts should be undertaken to reduce this rate. Enhancing imaging technologies including electronic chromoendoscopy and magnification has been increasingly adopted for improving the colorectal neoplasia detection rate and the detailed study of its surface, as well. I-scan images (Pentax, Tokyo, Japan) provides virtual chromoendoscopy in real-time during the examination to view the surface pattern, highlighting the microvasculature of the neoplastic lesion. The evidence on the impact of the use of I-scan on the colorectal adenoma detection rate is scarce.

OBJECTIVE

To evaluate whether the use of I-scan has impact on the adenoma miss rate (AMR) of screening colonoscopy exams.

METHODS

Observational and prospective study conducted by monitoring patients over 50 years undergoing colonoscopy. There were two groups: Group 1 - first inspection with standard high-definition white-light (HDWL) followed by a second inspection with I-scan 1; Group 2 - first inspection with I-scan 1 followed by a second inspection with standard HDWL. The primary outcome was the AMR from the first exam, calculated with the number of adenomas detected in the second exam, divided by the total number of adenomas detected in both exams.

RESULTS

A total of 85 patients participated in the study. 14 were excluded, with a final sample of 71 patients, in the Group 1, 34 patients, and the Group 2, 37. A total of 58 adenomas were detected, 40 in the first inspection (20 in each group) and 18 in the second inspection in group 1. The overall AMR was higher for the Group 1 than the Group 2 (47.4% vs 0% P=0.0002).

CONCLUSION

The use of I-scan 1 during colonoscopy exam reduces the AMR.

Quo vadis blood protein adductomics?

Chemicals are measured regularly in air, food, the environment, and the workplace. Biomonitoring of chemicals in biological fluids is a tool to determine the individual exposure. Blood protein adducts of xenobiotics are a marker of both exposure and the biologically effective dose. Urinary metabolites and blood metabolites are short term exposure markers. Stable hemoglobin adducts are exposure markers of up to 120 days. Blood protein adducts are formed with many xenobiotics at different sites of the blood proteins. Newer methods apply the techniques developed in the field of proteomics. Larger adducted peptides with 20 amino acids are used for quantitation. Unfortunately, at present the methods do not reach the limits of detection obtained with the methods looking at single amino acid adducts or at chemically cleaved adducts. Therefore, to progress in the field new approaches are needed.

A generic sample preparation method for the multiplex analysis of seven therapeutic monoclonal antibodies in human plasma or serum with liquid chromatography-tandem mass spectrometry

Due to the increasing number of therapeutic monoclonal antibodies (mAbs) used in the clinic, there is an increasing need for robust analytical methods to quantify total mAb concentrations in human plasma for clinical studies and therapeutic drug monitoring. We developed an easy, rapid, and robust sample preparation method for liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis. The method was validated for infliximab (IFX), rituximab (RTX), cetuximab (CTX), dupilumab (DPL), dinutuximab (DNX), vedolizumab (VDZ), and emicizumab (EMZ). Saturated ammonium sulfate (AS) was used to precipitate immunoglobulins in human plasma. After centrifugation, supernatant containing albumin was decanted, and the precipitated immunoglobulin fraction was re-dissolved in buffer containing 6M guanidine. This fraction was then completely denatured, reduced, alkylated, and trypsin digested. Finally, signature peptides from the seven mAbs were simultaneously quantified on LC-MS/MS together with their internal standards stable isotopically labeled peptide counterparts. The linear dynamic ranges (1 - 512 mg/L) of IFX, CTX, RTX, and EMZ showed excellent (R2 > 0.999) linearity and those of DPL, DNX, and VDZ showed good (R2 > 0.995) linearity. The method was validated in accordance with the EMA guidelines. EDTA plasma, sodium citrate plasma, heparin plasma, and serum yielded similar results. Prepared samples were stable at room temperature (20°C) and at 5°C for 3 days, and showed no decline in concentration for all tested mAbs. This described method, which has the advantage of an easy, rapid, and robust pre-analytical sample preparation, can be used as a template to quantify other mAbs in human plasma or serum.

Targeted liquid chromatography-tandem mass spectrometry analysis of proteins: Basic principles, applications, and perspectives

Liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) is now the main analytical method for the identification and quantification of peptides and proteins in biological samples. In modern research, identification of biomarkers and their quantitative comparison between samples are becoming increasingly important for discovery, validation, and monitoring. Such data can be obtained following specific signals after fragmentation of peptides using multiple reaction monitoring (MRM) and parallel reaction monitoring (PRM) methods, with high specificity, accuracy, and reproducibility. In addition, these methods allow measurement of the amount of post-translationally modified forms and isoforms of proteins. This review article describes the basic principles of MRM assays, guidelines for sample preparation, recent advanced MRM-based strategies, applications and illustrative perspectives of MRM/PRM methods in clinical research and molecular biology.

Liquid Chromatography-Multiple Reaction Monitoring-Mass Spectrometry Assay for Quantitative Measurement of Therapeutic Antibody Cocktail REGEN-COV Concentrations in COVID-19 Patient Serum

REGEN-COV is a cocktail of two human IgG1 monoclonal antibodies (REGN10933 + REGN10987) that targets severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein and has shown great promise to reduce the SARS-CoV-2 viral load in COVID-19 patients enrolled in clinical studies. A liquid chromatography-multiple reaction monitoring-mass spectrometry (LC-MRM-MS)-based method, combined with trypsin and rAspN dual enzymatic digestion, was developed for the determination of total REGN10933 and total REGN10987 concentrations in several hundreds of pharmacokinetic (PK) serum samples from COVID-19 patients participating in phase I, II, and III clinical studies. The performance characteristics of this bioanalytical assay were evaluated with respect to linearity, accuracy, precision, selectivity, specificity, and analyte stability before and after enzymatic digestion. The developed LC-MRM-MS assay has a dynamic range from 10 to 2000 μg/mL antibody drug in the human serum matrix, which was able to cover the serum drug concentration from day 0 to day 28 after drug administration in two-dose groups for the clinical PK study of REGEN-COV. The concentrations of REGEN-COV in the two-dose groups measured by the LC-MRM-MS assay were comparable to the concentrations measured by a fully validated electrochemiluminescence (ECL) immunoassay.

Bioanalytical strategies in drug discovery and development

A reliable, rapid, and effective bioanalytical method is essential for the determination of the pharmacokinetic, pharmacodynamic, and toxicokinetic parameters that inform the safety and efficacy profile of investigational drugs. The overall goal of bioanalytical method development is to elucidate the procedure and operating conditions under which a method can sufficiently extract, qualify, and/or quantify the analyte(s) of interest and/or their metabolites for the intended purpose. Given the difference in the physicochemical properties of small and large molecule drugs, different strategies need to be adopted for the development of an effective and efficient bioanalytical method. Herein, we provide an overview of different sample preparation strategies, analytical platforms, as well as procedures for achieving high throughput for bioanalysis of small and large molecule drugs.

Chemometric optimization of trypsin digestion method applying infrared, microwave and ultrasound energies for determination of caseins and ovalbumin in wines

Caseins and ovalbumin are frequently used as wine fining agents to remove undesirable compounds like polymeric phenols. Their presence in wines is a subject of concern because may cause adverse effects on susceptible consumers, especially when their presence is not labeled. A key step for its determination is trypsin digestion, which is considered the bottleneck of bottom-up approach workflow because usually requires several hours. To reduce this time, the objective of this work was to carry out a chemometric optimization of trypsin digestion method applying infrared, microwave and ultrasound energies to determine caseins and ovalbumin in wines. The conditions of each accelerated digestion method were optimized using a Response Surface Methodology based on central composite design. The parameters optimized were digestion time and trypsin: protein ratio. The response variable evaluated was digestion yield, which was determined through the peak area of each protein transition determined by liquid chromatography-mass spectrometry. The most effective technique was microwave followed by ultrasound and infrared. Since optimal values of microwave and ultrasound-assisted digestion were the same, the later was chosen considering sample preparation and cost. Applying the proposed approach, a reduction of ca. 140 and 240-fold on digestion time was achieved compared with optimized and non-optimized conventional methods, respectively. With this workflow, both proteins were digested in a single 3 min process allowing its detection by liquid chromatography-mass spectrometry at µg L^-1 level, which is ca. 60 times lower than the current limit of 0.25 mg L^-1.

Recent Advances in Sensing Applications of Molecularly Imprinted Photonic Crystals

Photonic crystals (PhCs) with a brightly colored structure are novel materials and are widely used in chemical and biological sensing. Combining PhCs with molecular imprinting technology (MIT), the molecularly imprinted PhC (MIPC) sensors are fabricated, which can specifically recognize the target molecules. Aside from high sensitivity and selectivity, the MIPC sensors could recognize the naked eye detection because of its optical properties. In this review, an overview of recent advances in sensing applications of MIPC sensors including the responsive mechanisms, application in environmental monitoring, and the application to human health were illustrated. The MIPC sensors all responded to the analytes specifically and also showed high sensitivity in real samples, which provided a method to realize the rapid, convenient, naked eye, and real-time detection. Furthermore, the current limitations and potential future directions of MIPC sensors were also discussed.

Development of a chromatography-free method for high-throughput MS-based bioanalysis of therapeutic monoclonal antibodies

Aim: Our objective was to test the feasibility of developing an LC-free, MS-based approach for high-throughput bioanalysis of humanized therapeutic monoclonal antibodies. Methodology: A universal tryptic peptide from human IgG1, IgG3 and IgG4 was selected as the surrogate peptide for quantitation. After tryptic digestion, the surrogate peptide was fractionated via solid-phase extraction before being subjected to direct infusion-based MS/MS analysis. A high-resolution, multiplexed (MSX = 2) parallel reaction monitoring method was developed for data acquisition. Results & conclusion: This proof-of-concept study demonstrated the feasibility of achieving high-throughput MS-based bioanalysis of monoclonal antibodies using an LC-free workflow with sensitivity comparable to conventional LC-MS/MS-based methods.

Visualizing the spatial localization of ciclesonide and its metabolites in rat lungs after inhalation of 1-μm aerosol of ciclesonide by desorption electrospray ionization-time of flight mass spectrometry imaging

Inhaled ciclesonide (CIC), a corticosteroid used to treat asthma that is also being investigated for the treatment of corona virus disease 2019, hydrolyzes to desisobutyryl-ciclesonide (des-CIC) followed by reversible esterification when exposed to fatty acids in lungs. While previous studies have described the distribution and metabolism of the compounds after inhalation, spatial localization in the lungs remains unclear. We visualized two-dimensional spatial localization of CIC and its metabolites in rat lungs after administration of a single dose of a CIC aerosol (with the mass median aerodynamic diameter of 0.918-1.168 μm) using desorption electrospray ionization-time of flight mass spectrometry imaging (DESI-MSI). In the analysis, CIC, des-CIC, and des-CIC-oleate were imaged in frozen lung sections at high spatial and mass resolutions in negative-ion mode. MSI revealed the coexistence of CIC, des-CIC, and des-CIC-oleate on the airway epithelium, and the distribution of des-CIC and des-CIC-oleate in peripheral lung regions. In addition, a part of CIC independently localized on the airway epithelium. These results suggest that distribution of CIC and its metabolites in lungs is related to both the intended delivery of aerosols to pulmonary alveoli and peripheral regions, and the potential deposition of CIC particles on the airway epithelium.

Design and Analysis of a Sample-and-Hold CMOS Electrochemical Sensor for Aptamer-based Therapeutic Drug Monitoring

In this paper, we present the design and the analysis of an electrochemical circuit for measuring the concentrations of therapeutic drugs using structure-switching aptamers. Aptamers are single-stranded nucleic acids, whose sequence is selected to exhibit high affinity and specificity toward a molecular target, and change its conformation upon binding. This property, when coupled with a redox reporter and electrochemical detection, enables reagent-free biosensing with a sub-minute temporal resolution for in vivo therapeutic drug monitoring. Specifically, we design a chronoamperometry-based electrochemical circuit that measures the direct changes in the electron transfer (ET) kinetics of a methylene blue reporter conjugated at the distal-end of the aptamer. To overcome the high-frequency noise amplification issue when interfacing with a large-size (> 0.25 mm2) implantable electrode, we present a sample-and-hold (S/H) circuit technique in which the desired electrode potentials are held onto noiseless capacitors during the recording of the redox currents. This allows disconnecting the feedback amplifiers to avoid its noise injection while reducing the total power consumption. A prototype circuit implemented in 65-nm CMOS demonstrates a cell-capacitance-insensitive input-referred noise (IRN) current of 15.2 pArms at a 2.5-kHz filtering bandwidth. We tested our system in human whole blood samples and measured the changes in the ET kinetics from the redox-labeled aptamers at different kanamycin concentrations. By employing principal component analysis (PCA) to compensate for the sampling errors, we report a molecular noise floor (at SNR = 1) of 3.1 µM with sub 1-sec acquisition time at 0.22-mW power consumption.

Development and Validation of an LC-MS-Based Quantification Assay for New Therapeutic Antibodies: Application to a Novel Therapy against Herpes Simplex Virus

Multiple therapeutic monoclonal antibodies (mAbs) are currently under development or in (pre)clinical study phases to reach regulatory approval. Among these, a new mAb against herpes simplex virus, HDIT101, was recently tested in healthy volunteers during a phase I clinical trial (first-in-human, dose escalation). In the frame of the pharmacokinetic evaluation of this new therapy, a mass spectrometric (MS)-based method was developed for the quantification of HDIT101 in human plasma using liquid chromatography coupled to tandem mass spectrometry. In this work, we describe the development of this bioanalytical assay using the quantification of a HDIT101 surrogate peptide, the assay validation procedure according to the FDA guidelines within the calibration range from 20 to 5000 μg/mL, and its application to plasma samples from the first-in-human clinical trial. This work presents a generic workflow for the development of MS-based quantification assays of new therapeutic antibodies that allows reaching high immunopurification recovery (>98% for HDIT101 over the full calibration range with a precision of 6.9% CV). Surrogate peptide and stable isotopically labeled internal standard were stable, and batch-to-batch accuracies and precisions at the four quality standard levels ranged between -2 and 5% bias and 8 and 11% CV, respectively.

Bottom-up sample preparation for the LC-MS/MS quantification of anti-cancer monoclonal antibodies in bio matrices

Therapeutic monoclonal antibodies (mAbs) are rapidly taking over the treatment of many malignancies, and an astonishing number of mAbs is in development. This causes a high demand for quantification of mAbs in biomatrices both for measuring therapeutic mAb concentrations and to support pharmacokinetics and pharmacodynamics studies. Conventionally, ligand-binding assays are used for these purposes, but LC-MS is gaining popularity. Although intact (top-down) and subunit (middle-down) mAb quantification is reported, signature peptide (bottom-up) quantification is currently most advantageous. This review provides an overview of the reported bottom-up mAb quantification methods in biomatrices as well as general recommendations regarding signature peptide and internal standard selection, reagent use and optimization of digestion in bottom-up quantification methods.

Approaching sites of action of drugs in clinical pharmacology: New analytical options and their challenges

Clinical pharmacology is an important discipline for drug development aiming to define pharmacokinetics (PK), pharmacodynamics (PD) and optimum exposure to drugs, i.e. the concentration-response relationship and its modulators. For this purpose, information on drug concentrations at the anatomical, cellular and molecular sites of action is particularly valuable. In pharmacological assays, the limited accessibility of target cells in readily available samples (i.e. blood) often hampers mass spectrometry-based monitoring of the absolute quantity of a compound and the determination of its molecular action at the cellular level. Recently, new sample collection methods have been developed for the specific capture of rare circulating cells, especially for the diagnosis of circulating tumour cells. In parallel, new advances and developments in mass spectrometric instrumentation now allow analyses to be scaled down to the cellular level. Together, these developments may permit the monitoring of minute drug quantities and show their effect at the cellular level. In turn, such PK/PD associations on a cellular level would not only enrich our pharmacological knowledge of a given compound but also expand the basis for PK/PD simulations. In this review, we describe novel concepts supporting clinical pharmacology at the anatomical, cellular and molecular sites of action, and highlight the new challenges in mass spectrometry-based monitoring. Moreover, we present methods to tackle these challenges and define future needs.

Fit-for-purpose protein biomarker assay validation strategies using hybrid immunocapture-liquid chromatography-tandem-mass spectrometry platform: Quantitative analysis of total soluble cluster of differentiation 73

In recent years, biomarkers have played more extensive roles as indicators of disease progression, safety, and drug efficacy. Targeted quantitative analysis of biomarkers including drug targets have become increasingly important to drive critical decision-making in various drug development stages, as well as to improve the success rates of clinical trials. There are many analytical challenges when developing and validating the bioanalytical methods associated with the measurement of an endogenous protein biomarker, especially when using LC-MS based analysis. Moreover, the current regulatory guidelines for assay development and validation using LC-MS platform mainly focuse on regulated bioanalysis for therapeutic drugs. In this manuscript, we use total soluble CD73 (sCD73) as an example to present a "fit-for-purpose" assay using a hybrid immunocapture-LC-MS/MS assay platform. A non-competing antibody (to the therapeutic drug) was used to isolate and enrich the total sCD73 from biological matrix. The enriched sample was digested after immunocapture and a surrogate peptide was monitored for quantification. The assay showed good accuracy, precision, specificity and sensitivity with the LLOQ of 1.00 ng/mL, and was applied in a clinical study to measure the total sCD73 as a potential pharmacodynamic (PD) marker. Some recommendations and considerations for "fit-for-purpose" validation of this assay, and hybrid LC-MS assays in general, for the quantitative analysis of an endogenous protein biomarkers is also discussed.

A simple and rapid LC-MS/MS and CE-MS/MS analytical strategy for the determination of therapeutic peptides in modern immunotherapeutics and biopharmaceutics

Modern therapy of metabolic, neurodegenerative, inflammation, or cancer diseases is recently based on an immunotherapeutic approach. The peptide conjugates represent innovative and effective therapeutics that are better tolerated and are much more specific than small molecule-based medicines. The nature and manufacturing process of these therapeutics make their analysis very challenging. Here, two robust analytical methods based on an on-line combination of ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) and capillary electrophoresis with tandem mass spectrometry (CE-MS/MS) were developed for fast determination of immunogenic synthetic peptide (peptide sequence CADNLHKVVGQST) in a conjugate with bovine serum albumin (BSA) as a carrier protein and is a peptide, conjugate formulated with a vaccine adjuvant - Alhydrogel® 2 %. An effective non-enzymatic release step of the peptide from the final peptide conjugate based on acid hydrolysis with the use of 2% formic acid was successfully tested and implemented. The proposed methods were validated according to the ICH guideline and parameters such as linearity, precision, and accuracy, the limit of detection (LOD) or limit of quantification (LOQ) were assessed. Calibration curves were linear within the range of 1-30 μg.mL^-1 and the correlation coefficients were higher than 0.99. The intraday and interday precisions were 3.2-8.1 % (UHPLC-MS/MS), 1.6-9.3 % (CE-MS/MS) and 3.6-10.3 % (UHPLC-MS/MS), 4.1-10.2 % (CE-MS/MS), respectively. The recovery ranged in the interval of 98.4-107.4 % for UHPLC-MS/MS method and 100.3-103.2 % for CE-MS/MS method. The presented approaches represent an effective tool for simple, rapid and robust quantification of immunogens in modern immunotherapeutics and other biopharmaceuticals with appropriate peptide sequences.

Evaluation, identification and impact assessment of abnormal internal standard response variability in regulated LC-MS bioanalysis

Internal standard (IS) plays an important role in LC-MS bioanalysis by compensating for the variability of the analyte of interest in bioanalytical workflow. Due to the complexity of biological sample compositions and bioanalytical processes, a certain level of IS response variability across a run or a study is anticipated. However, an extensive variability may raise doubts to the accuracy of the measured results and also suggest nonoptimal analytical method. In this current paper, recent publications and guidelines regarding IS response in LC-MS bioanalysis were thoroughly reviewed with focus on the evaluation, identification and impact assessment of 'abnormal' IS response variability. A systematic decision tree was proposed to facilitate investigation into abnormal IS response variability after each run.

Quality Control and Outlier Detection of Targeted Mass Spectrometry Data from Multiplex Protein Panels

Increased throughput as well as increased multiplexing of liquid chromatography coupled to selected reaction monitoring mass spectrometry (LC-SRM-MS) assays for protein quantification challenges routine data analysis. Despite the measurement of multiple transitions from multiple peptides, for clinical applications a single (quantifier) transition from one (quantifier) signature peptide is used to represent the protein quantity with most data used solely to validate the quantifier result. To support the generation of reliable protein results from multiplexed LC-SRM-MS assays with large sample numbers, we developed a data analysis process for quality control and outlier detection using data from an 11-protein multiplex LC-SRM-MS method for dried blood samples (195 492 chromatographic peaks from 1481 samples * 11 proteins * 2 peptides * 3 transitions * 2 isotopologues). The 2-tiered data analysis process detects outliers for ion transition ratio, peptide ratio, and % difference between duplicates, applying less stringent criteria to samples with a small % difference between duplicates (Tier 1) and more stringent criteria to samples with unassessed or a large % difference between duplicates (Tier 2). After manual peak review, 1127 samples (76%) were selected based on the sample quality. The data analysis process thereafter automatically selected quantifier transitions/peptides, removed quality control failures and outliers (8%), averaged duplicates, and generated a comprehensive report listing 6085 quality controlled protein-level results. The proposed data analysis process serves as a starting point toward standardized data analysis of multiplexed LC-SRM-MS protein assays.

Establishing an optimized method for the separation of low and high abundance blood plasma proteins

The study tested the efficiency and reproducibility of a method for optimal separation of low and high abundant proteins in blood plasma. Firstly, three methods for the separation and concentration of eluted (E: low abundance), or bound (B: high abundance) proteins were investigated: TCA protein precipitation, the ReadyPrep™ 2-D cleanup Kit and Vivaspin Turbo 4, 5 kDa ultrafiltration units. Secondly, the efficiency and reproducibility of a Seppro column or a ProteoExtract Albumin/IgG column were assessed by quantification of E and B proteins. Thirdly, the efficiency of two elution buffers, containing either 25% or 10% glycerol for elution of the bound protein, was assessed by measuring the remaining eluted volume and the final protein concentration. Compared to the samples treated with TCA protein precipitation and the ReadyPrep™ 2-D cleanup Kit, the E and B proteins concentrated by the Vivaspin4, 5 kDa ultrafiltration unit were separated well in both 1-D and 2-D gels. The depletion efficiency of abundant protein in the Seppro column was reduced after 15 cycles of sample processing and regeneration and the average ratio of E/(B + E) × 100% was 37 ± 11(%) with a poor sample reproducibility as shown by a high coefficient of variation (CV = 30%). However, when the ProteoExtract Albumin/IgG column was used, the ratio of E/(B + E) × 100% was 43 ± 3.1% (n = 6) and its CV was 7.1%, showing good reproducibility. Furthermore, the elution buffer containing 10% (w/v) glycerol increased the rate of B protein elution from the ProteoExtract Albumin/IgG column, and an appropriate protein concentration (3.5 µg/µl) for a 2-D gel assay could also be obtained when it was concentrated with Vivaspin Turbo 4, 5 kDa ultrafiltration unit. In conclusion, the ProteoExtract Albumin/IgG column shows good reproducibility of preparation of low and high abundance blood plasma proteins when using the elution buffer containing 10% (w/v) glycerol. The optimized method of preparation of low/high abundance plasma proteins was when plasma was eluted through a ProteoExtract Albumin/IgG removal column, the column was further washed with elution buffer containing 10% glycerol. The first and second elution containing the low and high abundance plasma proteins, respectively, were further concentrated using Vivaspin® Turbo 4, 5 kDa ultrafiltration units for 1 or 2-D gel electrophoresis.

Investigating surrogate cerebrospinal fluid matrix compositions for use in quantitative LC-MS analysis of therapeutic antibodies in the cerebrospinal fluid

As quantitative analysis of biotherapeutics in cerebrospinal fluid (CSF) with LC-MS becomes increasingly widespread, there is a need for method developments towards higher sensitivity. By using artificial CSF (aCSF) in the development phase, the consumption of costly and sparsely available CSF can be limited. The aCSF compositions tested here were made from various dilutions of bovine serum albumin (BSA) or rat plasma to mimic the total protein concentration found in CSF. Focusing on monoclonal antibodies, the aCSF was spiked with human immunoglobulin (hIgG) and prepared with the bottom-up analysis technique using LC-MS. Assuming that the composition of the aCSF would affect the digest, the response from aCSF matrices was compared with CSF from rat, monkey, and dog in terms of estimated sample concentration and matrix effects. The samples were spiked with hIgG in the range of 10 to 1000 ng/mL and volumes of 10 μL were transferred to sample preparation. The results indicate that BSA dilutions from 300 to 2000 μg/mL and rat plasma dilutions of 0.5–2% provide the most accurate concentration estimates when compared with rat CSF. 1000 μg/mL BSA did not produce significantly different concentration estimates for 500 ng/mL samples when compared with CSF from rat, monkey, and dog, and can therefore be used as aCSF for several different species.

LC-MS Compatible Antiadsorption Diluent for Peptide Analysis

Analytical method development for peptides often proves challenging since these molecules can adsorb to the plastic or glass consumables used in the analysis. This adsorption causes considerable loss and unreliable results, especially in the lower concentration range. Therefore, a variety of antiadsorption strategies have previously been developed to cope with this adsorption, often however incompatible with direct liquid chromatography-mass spectrometry (LC-MS) analysis. Here, a novel antiadsorption diluent is introduced, based on controlled hydrolysis and precipitation of bovine serum albumin. This diluent considerably decreases the adsorption of certain peptides to glass. Moreover, it is LC-MS compatible and can also be used in combination with formic acid and/or acetonitrile addition.

Therapeutic potential of polypeptide-based conjugates: Rational design and analytical tools that can boost clinical translation

The clinical success of polypeptides as polymeric drugs, covered by the umbrella term "polymer therapeutics," combined with related scientific and technological breakthroughs, explain their exponential growth in the development of polypeptide-drug conjugates as therapeutic agents. A deeper understanding of the biology at relevant pathological sites and the critical biological barriers faced, combined with advances regarding controlled polymerization techniques, material bioresponsiveness, analytical methods, and scale up-manufacture processes, have fostered the development of these nature-mimicking entities. Now, engineered polypeptides have the potential to combat current challenges in the advanced drug delivery field. In this review, we will discuss examples of polypeptide-drug conjugates as single or combination therapies in both preclinical and clinical studies as therapeutics and molecular imaging tools. Importantly, we will critically discuss relevant examples to highlight those parameters relevant to their rational design, such as linking chemistry, the analytical strategies employed, and their physicochemical and biological characterization, that will foster their rapid clinical translation.

Internal standards in regulated bioanalysis: putting in place a decision-making process during method development

It is common practice to utilize an internal standard (IS) to minimize variance in bioanalytical assays employing liquid chromatography coupled to mass spectrometry. For assays to be deployed in regulated drug development studies, ensuring the IS will compensate for differences in recovery, liquid handling and ionization efficiency should be determined early in the method development process. In this perspective article, we outline key considerations when selecting an IS and propose experiments to perform within the method development phase to demonstrate suitability of the IS within the assay prior to validation. Finally, a series of case studies will be presented, which illustrate analytical challenges related to internal standardization that we have observed in our laboratory.

Pharmacokinetic Analysis of a Novel Human EGFRvIII:CD3 Bispecific Antibody in Plasma and Whole Blood Using a High-Resolution Targeted Mass Spectrometry Approach

Bispecific single chain antibody fragments (bi-scFv) represent an emerging class of biotherapeutics. We recently developed a fully human bi-scFv (EGFRvIII:CD3 bi-scFv) with the goal of redirecting CD3-expressing T cells to recognize and destroy malignant, EGFRvIII-expressing glioma. In mice, we showed that EGFRvIII:CD3 bi-scFv effectively treats orthotopic patient-derived malignant glioma and syngeneic glioblastoma. Here, we developed a targeted assay for pharmacokinetic (PK) analysis of EGFRvIII:CD3 bi-scFv, a necessary step in the drug development process. Using microflow liquid chromatography coupled to a high resolution parallel reaction monitoring mass spectrometry, and data analysis in Skyline, we developed a bottom-up proteomic assay for quantification of EGFRvIII:CD3 bi-scFv in both plasma and whole blood. Importantly, a protein calibrator, along with stable isotope-labeled EGFRvIII:CD3 bi-scFv protein, were used for absolute quantification. A PK analysis in a CD3 humanized mouse revealed that EGFRvIII:CD3 bi-scFv in plasma and whole blood has an initial half-life of ∼8 min and a terminal half-life of ∼2.5 h. Our results establish a sensitive, high-throughput assay for direct quantification of EGFRvIII:CD3 bi-scFv without the need for immunoaffinity enrichment. Moreover, these pharmacokinetic parameters will guide drug optimization and dosing regimens in future IND-enabling and phase I studies of EGFRvIII:CD3 bi-scFv.