Genetic and functional evidence links a missense variant in B4GALT1 to lower LDL and fibrinogen.

Increased blood levels of low-density lipoprotein cholesterol (LDL-C) and fibrinogen are independent risk factors for cardiovascular disease. We identified associations between an Amish-enriched missense variant (p.Asn352Ser) in a functional domain of beta-1,4-galactosyltransferase 1 (B4GALT1) and 13.9 milligrams per deciliter lower LDL-C (P = 4.1 × 10­19) and 29 milligrams per deciliter lower plasma fibrinogen (P = 1.3 × 10­5). B4GALT1 gene­based analysis in 544,955 subjects showed an association with decreased coronary artery disease (odds ratio = 0.64, P = 0.006). The mutant protein had 50% lower galactosyltransferase activity compared with the wild-type protein. N-linked glycan profiling of human serum found serine 352 allele to be associated with decreased galactosylation and sialylation of apolipoprotein B100, fibrinogen, immunoglobulin G, and transferrin. B4galt1 353Ser knock-in mice showed decreases in LDL-C and fibrinogen. Our findings suggest that targeted modulation of protein galactosylation may represent a therapeutic approach to decreasing cardiovascular disease.

A staged hybrid approach to an aberrant right subclavian artery with symptomatic Kommerell's diverticulum.

Aberrant right subclavian is a rare anomaly presenting in 0.3-3.0% of the population. Kommerell's diverticulum is an aneurysm associated with this phenomen; data relating to its incidence is sparse. Currently there are no well-established guidelines for the treatment of Kommerell's diverticulum, limitation being the rare occurrence of disease and heterogenous population with disease presentation. This case report illustrates a novel approach to the repair of a symptomatic Kommerrel's diverticulum with severe coronary disease. Management should be tailored on a case by case basis to the individual patient.

Fenestration of the common iliac vein: an unusual cause of deep venous thrombus.

Iliac venous anomalies are reported in 20.9% of patients; however, fenestration or bifurcation of the common iliac vein only accounts for ~0.4% of patients [ 1]. Herein, we present and discuss the rare case of an iliofemoral deep vein thrombosis precipitated by a fenestrated left common iliac vein.

Evaluating the frequency of positive paraneoplastic antibodies and associated malignancy risk.

OBJECTIVE: To evaluate the association between malignancy and frequently positive paraneoplastic antibodies. METHODS: A retrospective cohort study was carried out for all patients who received paraneoplastic antibody testing in 2013-2014 at a tertiary referral center. Available medical records on included patients were reviewed through July 2020. Patients were divided into antibody positive and negative subgroups. Focused analysis was performed on the subgroup of patients who received testing via a commonly used antibody panel. RESULTS: A total of 1860 patients (the full cohort) received 19,323 antibody testing via panel or individual antibody testing, and were followed-up for a mean period of 36.2 months (range 0-83 months). Altogether 229 antibodies in 196 patients were positive, and 9 (3.9%) in 7 patients were against onconeuronal antigens. The remaining 220 (96.1%) were positive for mostly antibodies against cell surface or synaptic antigens. A total of 1161 patients received Mayo Clinic paraneoplastic antibody panel tests (the panel cohort), and 14.9% (173) of these patients possessed one or more positive antibodies. For the panel cohort, no difference was found between antibody positive and negative groups with respect to the prevalence of previously existing malignancy (15.6% versus 16.6%, p = 0.745) or incidence of new malignancy (4.0% vs. 3.7%, p = 0.848) during the follow-up period. No difference was observed in the incidence of new malignancy during follow-up between the antibody positive and negative groups for the 7 most frequently positive antibodies. CONCLUSIONS: The presence of frequently positive antibodies, mostly to cell surface or synaptic antigens, is not clearly associated with the development of malignancy in the subsequent three years.

Online coupling of analytical hydrophobic interaction chromatography with native mass spectrometry for the characterization of monoclonal antibodies and related products.

Native mass spectrometry (native MS) has seen tremendous development and an increase in application over the past decade for the study of proteins and protein complexes. Although conventionally performed using a static nanospray emitter in an offline fashion, native MS has been increasingly applied in hyphenated methods, where a wide variety of separation techniques are directly coupled to online native MS detection. Those new developments have greatly expanded the utility of native MS in protein biopharmaceutical characterization. Analytical hydrophobic interaction chromatography (HIC) method, although frequently used for the characterization of monoclonal antibodies (mAbs) and antibody-drug-conjugates (ADCs), has rarely been explored for online coupling with native MS. This is largely due to the high salt concentrations used in HIC analysis that are not compatible with direct MS detection. In this study, we overcame this challenge via an innovative makeup and splitting flow design and successfully achieved online coupling of analytical HIC separation with native MS detection. The development and experimental setup of this HIC-MS method is outlined in detail to elucidate how this design could tackle the high salt concentrations used in HIC separation and ultimately achieve both good chromatographic resolution and MS data quality. Subsequently, the utility of this HIC-MS method was demonstrated in three different applications, where a mAb mixture, mAb molecular variants resulting from PTMs, and a Cys-based ADC mimic were all readily characterized in detail. Unlike previously reported HIC-MS methods, this newly developed method utilizes an analytical scale HIC column with conventional ligand so that the achieved separation profile is highly comparable to those obtained by a standard HIC-UV method. As a result, this HIC-MS method not only provides an alternative approach for in-depth characterization of mAbs and related products during their development but could also be readily applied to assist peak assignment and identity elucidation for the HIC-UV method used in quality control.

A one-step NIST traceable HPLC method for quantitation of vitamin B6 and 4-pyridoxic acid in human plasma.

OBJECTIVES: Vitamin B6 deficiency is associated with a wide spectrum of clinical syndromes. While vitamin B6 status is primarily assessed by measuring the biologically active form of the vitamin, pyridoxal 5-phosphate (PLP), concurrent measurement of the final metabolite 4-pyridoxic acid (PA) can provide additional information regarding supplement intake and hypophosphatasia. The aim of this study is to develop a simple method traceable to the NIST standard reference material 3950 for simultaneous detection of PLP and PA. DESIGN & METHODS: A one-step reverse phase HPLC method with fluorescence detection was developed by evaluating different derivatization conditions, the use of an internal standard and different calibration strategies. The assay analytical performance was evaluated. RESULTS: Pre-column derivatization with semicarbazide showed the best overall performance in terms of signal to noise ratio, retention time and peak shape when compared to pre- or post-column derivatization with chlorite, pre-column or in-mobile phase derivatization using sodium bisulfite. The final method provided an analytical measurement range from 7.8 to 350 â€‹nmol/L for PLP and 3.3-339 â€‹nmol/L for PA, total imprecision <15% and <5% for PLP and PA respectively. Calibration against the NIST standard produced measured values within 3% of NIST assigned PLP values. The use of 4-deoxypyridoxine as internal standard did not improve precision or accuracy when compared to calibration using 5-level external standards. CONCLUSIONS: This method combines derivatization and protein precipitation in one step and is traceable to NIST standard reference material 3950. It is simple and reliable for routine evaluation of vitamin B6 nutrition status.

Improved Host Cell Protein Analysis in Monoclonal Antibody Products through Molecular Weight Cutoff Enrichment.

Host cell proteins (HCPs) are process-related impurities that are generated by the host organism and are typically present at low levels in recombinant biopharmaceutical products, such as therapeutic antibodies. While overall HCP levels are usually monitored by enzyme-linked immunosorbent assay (ELISA), liquid chromatography coupled to mass spectrometry (LC-MS) is emerging as a powerful tool that can provide both qualitative and quantitative information about HCP levels during purification process development. However, a major challenge for LC-MS-based methods is that there can be a more than 5 orders of magnitude difference in the concentration between HCPs and therapeutic antibody in solution, which precludes the effective identification of low abundance HCPs in antibody product. This work reports a simple and powerful strategy to identify HCPs in antibody drug substance by applying molecular weight cutoff (MWCO) filtration step followed by shotgun proteomic analysis. After dissociating the interaction between HCPs and antibody with an anionic detergent, the depletion of antibody from HCPs can be easily achieved with the MWCO filtration step. Using this method, we observed that the dynamic range across proteins in the HCP samples was significantly decreased up to 1000-fold. In addition, by spiking in known amounts of HCPs to purified antibody drug substance with low levels of HCPs, we demonstrated that our method could detect HCP with low molecular weight (11 kDa and 17 kDa) at a concentration as low as 1 ppm. When applying this methodology to the study of HCPs in NIST monoclonal antibody (NISTmAb), more than 150 HCPs were confidently identified, which doubles the number of identified HCPs that have been previously reported. Parallel reaction monitoring (PRM) results confirmed that the novel HCPs found using this method were present in very low abundance (0.01-8 ppm), highlighting that our method reduces the dynamic range by removing antibody interference and improving the sensitivity of HCP identification and quantification.

Lys-Sequencer: An algorithm for de novo sequencing of peptides by paired single residue transposed Lys-C and Lys-N digestion coupled with high-resolution mass spectrometry.

RATIONALE: Database-dependent identification of proteins by mass spectrometry is well established, but has limitations when there are novel proteins, mutations, splice variants, and post-translational modifications (PTMs) not available in the established reference database. De novo sequencing as a database-independent approach could address these limitations by deducing peptide sequences directly from experimental tandem mass spectrometry spectra, while concomitantly yielding residue-by-residue confidence metrics. METHODS: Equal amounts of bovine serum albumin (BSA) sample aliquots were digested separately with Lys-C and Lys-N complementary peptidases, separated by reversed-phase ultra-high-performance liquid chromatography (UPLC), and analyzed by collision-induced dissociation (CID)-based mass spectrometry on an Orbitrap mass spectrometer. In the Lys-Sequencer algorithm, matched tandem mass spectra with equal precursor ion mass from complementary digestions were paired, and fragment ion types were identified based on the unique mass relationship between fragment ions extracted from a spectrum pair followed by de novo sequencing of peptides with identification confidence assigned at the residue level. RESULTS: In all the matched spectrum pairs, 34 top-ranked BSA peptides were identified, from which 391 amino acid residues were identified correctly, covering ~67% of the full sequence of BSA (583 residues) with only ~6% (35 residues) exhibiting ambiguity in the sequence order (although amino acid compositions were still correctly assigned). Of note, this approach identified peptide sequences up to 17 amino acids in length without ambiguity, with the exception of the N-terminal or C-terminal peptides containing lysine (18-mer). CONCLUSIONS: The algorithm ("Lys-Sequencer") developed in this work achieves high precision for de novo sequencing of peptides. This method facilitates the identification of point mutation and new PTMs in the protein characterization and discovery of new peptides and proteins with varying levels of confidence.

Quantitation and modeling of post-translational modifications in a therapeutic monoclonal antibody from single- and multiple-dose monkey pharmacokinetic studies using mass spectrometry.

Post-translational modifications (PTMs) of therapeutic monoclonal antibodies (mAbs) are important product quality attributes (PQAs) that can potentially impact drug stability, safety, and efficacy. The PTMs of a mAb may change remarkably in the bloodstream after drug administration compared to in vitro conditions. Thus, monitoring in vivo PTM changes of mAbs helps evaluate the criticality of PQAs during the product risk assessment. In addition, quantitation of the subject exposures to PTM variants helps assess the impact of PTMs on the safety and efficacy of therapeutic mAbs. Here, we developed an immunocapture-liquid chromatography/mass spectrometry (LC/MS) method to quantify in vivo PTM changes a therapeutic mAb overtime in single- and multiple-dose monkey pharmacokinetic (PK) studies. We also built mathematical models to predict the in vivo serum concentrations of PQAs, the subject exposures to PQAs, and the relative abundance of PQAs in single- and multiple-dose regimens. The model predictions are in good agreement with the experimental results. The immunocapture-LC/MS method and mathematical models enable bioanalytical chemists to quantitatively assess the criticality of PQAs during drug development.

Coupling Mixed-Mode Size Exclusion Chromatography with Native Mass Spectrometry for Sensitive Detection and Quantitation of Homodimer Impurities in Bispecific IgG.

Detection and quantitation of homodimer impurities in therapeutic bispecific antibody (bsAb) drug products is essential to support development and quality control (QC) release. LC-MS-based techniques have been frequently applied for this analysis. However, sensitive detection of low-abundance homodimer impurities can still be challenging for regular workflows, which is largely due to the lack of chromatographic resolution between the impurities and the main bsAb species. Here, we report the development of a novel analytical method, which couples mixed-mode size exclusion chromatography (mmSEC) with online native MS detection (mmSEC-MS) for highly sensitive detection and quantitation of homodimer impurities in bsAb samples. Secondary interactions between the protein analytes and the column matrix, which are typically unwanted in SEC applications, are utilized to separate mAb species with similar hydrodynamic volume but different surface characteristics. Using four different bsAbs as testing standards, we demonstrated the versatility of this method in separating homodimer species from bsAb based on either electrostatic interaction or hydrophobic interaction, which was easily achieved by utilizing SEC columns with different properties as well as modulating the salt concentrations. The chromatographic separation between homodimer impurities and bsAb, as achieved by the mmSEC method, was demonstrated to be critical for the improved sensitivity in detecting low-abundance homodimer impurities (LOD from 0.01% to 0.1%). To the best of our knowledge, this newly developed mmSEC-MS method represents the most sensitive MS-based technique in both detection and quantitation of homodimer impurities in bsAb samples.

Anti-VEGF drug interference with VEGF quantitation in the R&D systems human quantikine VEGF ELISA kit.

AIM: To evaluate the accuracy of the Quantikine Human VEGF Immunoassay (R&D Systems) in the presence of VEGF inhibitors. MATERIALS & METHODS: Quantikine VEGF ELISA (R&D), anti-VEGF165 mAb (R&D), VEGF165 and aflibercept (Regeneron), ranibizumab and bevacizumab (Genentech). RESULTS: Binding affinity of anti-VEGF165 mAb for VEGF was threefold weaker than aflibercept, but 33- and 40-fold stronger than ranibizumab or bevacizumab. Extended incubation of VEGF complexed with inhibitors led to VEGF dissociation from ranibizumab and bevacizumab, but not aflibercept, and subsequent binding by the immunoassay capture antibody. The immunoassay also detected VEGF:ranibizumab and VEGF:bevacizumab complexes but not VEGF:aflibercept complexes. CONCLUSION: The immunoassay cannot accurately quantitate VEGF in the presence of these VEGF inhibitors as they interfere with the capture and detection of free VEGF.

Fast protein sequencing of monoclonal antibody by real-time digestion on emitter during nanoelectrospray.

Growth in the pharmaceutical industry has led to an increasing demand for rapid characterization of therapeutic monoclonal antibodies. The current methods for antibody sequence confirmation (e.g., N-terminal Edman sequencing and traditional peptide mapping methods) are not sufficient; thus, we developed a fast method for sequencing recombinant monoclonal antibodies using a novel digestion-on-emitter technology. Using this method, a monoclonal antibody can be denatured, reduced, digested, and sequenced in less than an hour. High throughput and satisfactory protein sequence coverage were achieved by using a non-specific protease from Aspergillus saitoi, protease XIII, to digest the denatured and reduced monoclonal antibody on an electrospray emitter, while electrospray high voltage was applied to the digestion mixture through the emitter. Tandem mass spectrometry data was acquired over the course of enzyme digestion, generating similar information compared to standard peptide mapping experiments in much less time. We demonstrated that this fast protein sequencing method provided sufficient sequence information for bovine serum albumin and two commercially available monoclonal antibodies, mouse IgG1 MOPC21 and humanized IgG1 NISTmAb. For two monoclonal antibodies, we obtained sequence coverage of 90.5-95.1% for the heavy chains and 98.6-99.1% for the light chains. We found that on-emitter digestion by protease XIII generated peptides of various lengths during the digestion process, which was critical for achieving sufficient sequence coverage. Moreover, we discovered that the enzyme-to-substrate ratio was an important parameter that affects protein sequence coverage. Due to its highly automatable and efficient design, our method offers a major advantage over N-terminal Edman sequencing and traditional peptide mapping methods in the identification of protein sequence, and is capable of meeting an ever-increasing demand for monoclonal antibody sequence confirmation in the biopharmaceutical industry.

Simple Approach for Improved LC-MS Analysis of Protein Biopharmaceuticals via Modification of Desolvation Gas.

LC-MS based analysis of protein biopharmaceuticals could benefit from improved data quality, which can subsequently lead to improved drug characterization with higher confidence and less ambiguity. In this study, we created a simple device to modify the desolvation gas on a Q-Exactive mass spectrometer and to demonstrate the utility in improving both peptide mapping analysis and intact mass analysis, the two most routinely and widely applied LC-MS techniques in protein biopharmaceutical characterization. By modifying the desolvation gas with acid vapor from propionic acid (PA) and isopropanol (IPA), the ion suppression effects from trifluoroacetic acid (TFA) in a typical peptide mapping method can be effectively mitigated, thus leading to improved MS sensitivity. By modifying the desolvation gas with base vapor from triethylamine (TEA), the charge reduction effect can be achieved and utilized to improve the spectral quality from intact mass analysis of protein biopharmaceuticals. The approach and device described in this work suggests a low-cost and practical solution to improve the LC-MS characterization of protein biopharmaceuticals, which has the potential to be widely implemented in biopharmaceutical analytical laboratories.

Ultrasensitive Characterization of Charge Heterogeneity of Therapeutic Monoclonal Antibodies Using Strong Cation Exchange Chromatography Coupled to Native Mass Spectrometry.

In therapeutic monoclonal antibody (mAb) development, charge heterogeneity of a mAb molecule is often associated with critical quality attributes and is therefore monitored throughout development and during QC release to ensure product and process consistency. Elucidating the cause of each charge variant species is an involved process that often requires offline fractionation by ion exchange chromatography (IEX) followed by mass spectrometry (MS) analysis, largely due to the incompatibility of conventional IEX buffers for direct MS detection. In this study, we have developed a method that combines a generic strong cation exchange (SCX) chromatography step with ultrasensitive online native MS analysis (SCX-MS) optimized for mAb separation and detection. As demonstrated by analyzing mAb molecules with a wide range of pI (isoelectric point) values, the developed method can consistently achieve both high-resolution IEX separation and ultrasensitive MS detection of low-abundance charge variant species. Using this method, we analyzed the charge heterogeneity of NISTmAb reference material 8671 (NISTmAb) at both whole antibody and subdomain levels. In particular, due to the high sensitivity, a nonconsensus Fab glycosylation site, present at a very low level (<0.1%), was directly detected in the NISTmAb sample without any enrichment. The structure and location of this Fab glycosylation was further characterized by peptide mapping analysis. Despite the extensive characterization of NISTmAb material in previous studies, this is the first time that this Fab-glycosylated variant has been identified in the NISTmAb, demonstrating the value of this new method in achieving a more comprehensive characterization of charge heterogeneity for therapeutic mAbs.

Positivity rates of in vitro inhalant/respiratory and food allergy tests in the northern midwestern United States.

Rates of allergy-test positivity vary by country and by regions within countries. Several studies have looked at allergy test results to determine the most common allergens. Many of these studies have been based on surveys or on studies of small numbers of tests. Positivity rates for allergy tests are poorly defined in the northern midwestern region of the United States. We conducted a study to identify the rates of positive allergy tests for both inhalant/respiratory allergens and food allergens in the upper Midwest. We extracted from our laboratory database the results of all test samples sent for one of eight allergen panels that had been analyzed between Sept. 1, 2014, and Sept. 1, 2015. All testing was performed at The Cleveland Clinic with the Phadia ImmunoCAP system. The percentage of positive tests, the distribution of the most frequently positive tests, and the class of in vitro responses were identified. A total of 148,628 test results for 63 different allergens were identified. Of the 125,190 tests for inhalant/respiratory allergens, the most frequently positive were dog dander (24% of tests), cat dander (23%), dust mites (23% for both Dermatophagoides pteronyssinus and Dermatophagoides farinae), and June grass (21%). Of the 23,438 food tests, the most frequently positive test results were for milk (18%), peanut (17%), wheat (16%), and egg white (15%). Most of the results fell into classes 1 through 3, although there was still a notable number of very high responses (class 5 and 6). These findings suggest that there is wide variability in the positivity of in vitro allergy tests and that the likelihood of a positive result in screening panels can be estimated. Evaluating such rates will help identify the most and least common allergens and will help to cost-effectively refine allergy screening panels.

Characterization of product-related low molecular weight impurities in therapeutic monoclonal antibodies using hydrophilic interaction chromatography coupled with mass spectrometry.

Traditional SDS-PAGE method and its modern equivalent CE-SDS method are both widely applied to assess the purity of therapeutic monoclonal antibody (mAb) drug products. However, structural identification of low molecular weight (LMW) impurities using those methods has been challenging and largely based on empirical knowledges. In this paper, we present that hydrophilic interaction chromatography (HILIC) coupled with mass spectrometry analysis is a novel and orthogonal method to characterize such LMW impurities present within a purified mAb drug product sample. We show here that after removal of N-linked glycans, the HILIC method separates mAb-related LMW impurities with a size-based elution order. The subsequent mass measurement from a high-resolution accurate mass spectrometer provides direct and unambiguous identification of a variety of low-abundance LMW impurities within a single LC-MS analysis. Free light chain, half antibody, H2L species (antibody possessing a single light chain) and protein backbone-truncated species can all be confidently identified and elucidated in great detail, including the truncation sites and associated post-translational modifications. It is worth noting that this study provides the first example where the H2L species can be directly detected in a mAb drug product sample by intact mass analysis without prior enrichment.

Assessment of Patient Medication Adherence, Medical Record Accuracy, and Medication Blood Concentrations for Prescription and Over-the-Counter Medications.

Importance: Inaccurate medication records and poor medication adherence result in incomplete knowledge of therapy for patients. Objective: To study accuracy of medical records and patient adherence by measuring blood concentrations of medications. Design, Setting, and Participants: This cross-sectional study validated a serum-based liquid chromatography-tandem mass spectrometry assay to simultaneously quantify 263 medications used for acute and chronic conditions. The assay panel was applied to 3 clinical patient cohorts: residual serum from 1000 randomly selected samples sent for routine clinical chemistry testing between April 8 and October 6, 2015 (residuals cohort), 50 prospectively enrolled patients in a gastroenterology clinic between March 1 and March 15, 2016, who were prescribed more than 5 medications (gastroenterology care cohort), and a convenience cohort of 296 patients with hypertension who sought care in an emergency department (ED care cohort) between July 1, 2012, and April 25, 2013. Integrated data analysis of the cohorts was performed from August 22 to November 29, 2017. Main Outcomes and Measures: Medication serum concentrations, electronic health record medication lists, and predicted drug interactions. Results: Of the 1346 total samples, 1000 came from the residuals cohort (640 women and 360 men; median age, 60 years [interquartile range (IQR), 44-71 years]), 50 from the gastroenterology care cohort (30 women and 20 men; median age, 66 years [IQR, 62-70 years]), and 296 from the ED care cohort (160 women and 136 men; median age, 59 years [IQR, 52-66 years]). Median medication adherence, defined as the subset of detected medications from the prescription record, was 83% (IQR, 50%-100%) in the residuals cohort, 100% (IQR, 84%-100%) in the gastroenterology care cohort, and 78% (IQR, 57%-100%) in the ED care cohort. Patients adherent to 1 medication were more often adherent to other medications. Among patients prescribed 3 medications or more, there were no significant associations between medication adherence and sex or number of prescribed medications, and there was a modest association between adherence and age. By comparing detected vs prescribed medications, we detected a median of 0 (IQR, 0-2) medications per patient that were not listed in the electronic health record in the residuals cohort, 1 (IQR, 0-2) medication per patient that was not listed in the electronic health record in the gastroenterology care cohort, and 1 (IQR, 0-2) medication per patient that was not listed in the electronic health record in the ED care cohort. A total of 435 patients (43.5%) in the residuals cohort had no discrepancy between the electronic health record and detected medication lists, 22 patients (44.0%) in the gastroenterology care cohort had no discrepancy between the electronic health record and detected medication lists, and 41 patients (13.9%) in the ED care cohort had no discrepancy between the electronic health record and detected medication lists. Half of adverse drug reaction alerts occurred among medications detected without prescription. Conclusions and Relevance: Comprehensive medication monitoring offers promise to improve adherence, the accuracy of medical records, and the safety for patients with polypharmacy.