Trapping-Enrichment Multi-dimensional Liquid Chromatography with On-Line Deuterated Solvent Exchange for Streamlined Structure Elucidation at the Microgram Scale

At the forefront of chemistry and biology research, development timelines are fast-paced and large quantities of pure targets are rarely available. Herein, we introduce a new framework, which is built upon an automated, online trapping-enrichment multi-dimensional liquid chromatography platform (TE-Dt-mDLC) that enables: 1) highly efficient separation of complex mixtures in a first dimension (¹ D-UV); 2) automated peak trapping-enrichment and buffer removal achieved through a sequence of H₂ O and D₂ O washes using an independent pump setup; and 3) a second dimension separation (² D-UV-MS) with fully deuterated mobile phases and fraction collection to minimize protic residues for immediate NMR analysis while bypassing tedious drying processes and minimizing analyte degradation. Diverse examples of target isolation and characterization from organic synthesis and natural product chemistry laboratories are illustrated, demonstrating recoveries above 90 % using as little as a few micrograms of material.

A simple mathematical treatment for predicting linear solvent strength behaviour in gradient elution: application to biomolecules

This paper describes an approach to rapidly and easily calculate the linear solvent strength parameters, namely log k₀ and S, under reversed‐phase liquid chromatography conditions. This approach, which requires two preliminary gradient experiments to determine the retention parameters, was applied to various representative compounds including small molecules, peptides, and proteins. The retention time prediction errors were compared to the ones obtained with a commercial HPLC modeling software, and a good correlation was found between the values. However, two important constraints have to be accounted for to maintain good predictions with this new approach: i) the retention factor at the initial composition of the preliminary gradient series have to be large enough (i.e., log k_i above 2.1) and ii) the retention models have to be sufficiently linear. While these two conditions are not always met with small molecules or even peptides, the situation is different with large biomolecules. This is why our simple calculation method should be preferentially applied to calculate the linear solvent strength parameters of protein samples.

Monitoring multiple quality attributes of a complex Fc-fusion protein during cell culture production processes by mD-LC-MS peptide mapping

Fc-fusion proteins represent a successful class of biopharmaceutical products. They are considered highly heterogeneous products due to the common degradation of amino acids that occurs during their production in upstream and downstream processes (e.g., oxidation and deamidation) and, above all, their complex glycosylation profile. Multi-dimensional liquid chromatography-mass spectrometry (mD-LC-MS) has recently gained much interest for process analytical technology, enabling the integration of this analytical technology in production and purification environments. In this study, an online mD-LC-MS/MS peptide mapping method was developed for monitoring multiple quality attributes, including the N-glycosylation state of a complex Fc-fusion protein, which is made by combining two heavily glycosylated cytokines with an Fc domain. This fully automated workflow includes sample purification, reduction, digestion, peptide mapping, and subsequent mass spectrometric analysis. Two immobilized enzyme cartridges based on trypsin and Lys-C protease were employed to generate a detailed glycosylation mapping, as trypsin allowed the identification of only one of four glycosylation sites, while Lys-C was more informative for two other sites. Site-specific glycosylation information such as antennarity, sialyation, and core fucosylation state was also determined. In addition to glycans, other post-translational modifications could be monitored simultaneously during the cell culture production processes by the mD-LC-MS/MS approach. In summary, the generated data demonstrate the applicability of mD-LC-MS for the monitoring and trending of multiple attributes for complex antibody formats over production processes in an automated and fast manner, compared to the complex and time-consuming traditional offline assays.

Automated ion exchange chromatography screening combined with in silico multifactorial simulation for efficient method development and purification of biopharmaceutical targets

Bioprocess development of increasingly challenging therapeutics and vaccines requires a commensurate level of analytical innovation to deliver critical assays across functional areas. Chromatography hyphenated to numerous choices of detection has undeniably been the preferred analytical tool in the pharmaceutical industry for decades to analyze and isolate targets (e.g., APIs, intermediates, and byproducts) from multicomponent mixtures. Among many techniques, ion exchange chromatography (IEX) is widely used for the analysis and purification of biopharmaceuticals due to its unique selectivity that delivers distinctive chromatographic profiles compared to other separation modes (e.g., RPLC, HILIC, and SFC) without denaturing protein targets upon isolation process. However, IEX method development is still considered one of the most challenging and laborious approaches due to the many variables involved such as elution mechanism (via salt, pH, or salt-mediated-pH gradients), stationary phase's properties (positively or negatively charged; strong or weak ion exchanger), buffer type and ionic strength as well as pH choices. Herein, we introduce a new framework consisting of a multicolumn IEX screening in conjunction with computer-assisted simulation for efficient method development and purification of biopharmaceuticals. The screening component integrates a total of 12 different columns and 24 mobile phases that are sequentially operated in a straightforward automated fashion for both cation and anion exchange modes (CEX and AEX, respectively). Optimal and robust operating conditions are achieved via computer-assisted simulation using readily available software (ACD Laboratories/LC Simulator), showcasing differences between experimental and simulated retention times of less than 0.5%. In addition, automated fraction collection is also incorporated into this framework, illustrating the practicality and ease of use in the context of separation, analysis, and purification of nucleotides, peptides, and proteins. Finally, we provide examples of the use of this IEX screening as a framework to identify efficient first dimension (¹D) conditions that are combined with MS-friendly RPLC conditions in the second dimension (²D) for two-dimensional liquid chromatography experiments enabling purity analysis and identification of pharmaceutical targets.

Improving Selectivity in the Chromatographic Analysis of Monoclonal Antibodies (mAbs) Through the Use of Multi-Isocratic Elution Mode

When characterizing monoclonal antibodies (mAbs) with reversed-phase liquid chromatography (RPLC), it is often challenging to attain sufficient selectivity between mAbs and their related variants. A new strategy, referred to as multi-isocratic elution mode, has recently been developed. It is based on setting a series of consecutive isocratic steps and very short steep gradient segments at solute elution. This elution mode offers several advantages compared to the usually applied linear gradient mode. Large biomolecules can benefit the most because of their “on/off” elution behavior. Arbitrary selectivity can be set between closely related protein variants while maintaining sharp peaks because of the strong band compression effects occurring at elution within the steep gradient segments.

Direct coupling of size exclusion chromatography and mass spectrometry for the characterization of complex monoclonal antibody products

The present study describes the possibilities offered by an innovative bioinert size exclusion chromatography column for size variant characterization of complex monoclonal antibody products. This size exclusion chromatography column includes a novel column hardware surface. The column was prepared from metallic hardware components that were treated to have prototype hydrophilically modified hybrid organic–inorganic silica surfaces called hybrid surface technology. This provides a significant reduction in nondesired hydrophobic and electrostatic interactions that can occur between column and analyte when performing size exclusion chromatography analysis with volatile mobile phase.

Compared to a reference stainless‐steel column packed with the same batch of packing material, peak tailing, band broadening, and above all recovery of high molecular weight species were distinctly improved for all types of monoclonal antibody products. Based on our observations, we found that 50 mM ammonium acetate in water was a suitable mobile phase offering good compromise in terms of liquid chromatography performance and mass spectrometry sensitivity. In addition, method repeatability (intra‐ and interday relative standard deviations) on elution times and high molecular weight species peak areas were found to be excellent.

By using this innovative size exclusion chromatography material, the low and high molecular weight species contained in various stressed and nonstressed monoclonal antibody products were successfully characterized with mass spectrometry detection.

Fast Optimization of Supercritical Fluid Chromatography-Mass Spectrometry Interfacing Using Prediction Equations

The effect of makeup solvent composition in ultrahigh-performance supercritical fluid chromatography-triple quadrupole mass spectrometry using electrospray ionization was studied using a set of 91 compounds, 3 stationary phases, and 2 organic modifiers of the mobile phase. The 24 tested makeup solvents included pure alcohols and methanol in combination with commonly used additives such as water, formic and acetic acid, ammonia, and ammonia salts with varying molarity. The behavioral trends for different makeup solvent additives were established in the first step. Subsequently, the correlations between physicochemical properties and the MS responses were calculated using the Pearson correlation test and matrix plots. The regression analysis was performed using five descriptors: molecular weight, pK_a, log P, number of hydrogen donors/acceptors, and the MS responses obtained with methanol as the makeup solvent. The resulting regression equations had a high prediction rate calculated as R²-predicted coefficient, especially when 10 mmol/L ammonium in methanol was used as an organic modifier of the mobile phase in positive mode. The trueness of these equations was tested via the comparison between experimental and predicted responses expressed as R². Values of R² > 0.8 were found for 88% of the proposed equations. Thus, the MS response could be measured using only one makeup solvent and the responses of other makeup solvents could be easily estimated. The suitability and applicability of determined regression equations was confirmed by the analysis of 13 blind probes, i.e., compounds not included in the original set of analytes. Moreover, the predicted and experimental responses followed the same increasing/decreasing trend enabling one to predict makeup solvent compositions leading to the highest sensitivity.

Challenges in ESI-MS-based Untargeted Metabolomics

Untargeted metabolomics is now widely recognized as a useful tool for exploring metabolic changes taking place in biological systems under different conditions. In this article, we aim to provide a short overview of the liquid-phase separation methods hyphenated to MS to perform untargeted metabolomics of biological samples. Each approach is complemented by up-to-date literature to guide readers, as well as practical information for avoiding or fixing some of the most frequently encountered pitfalls. This article covers mainly data acquisition, but a short discussion is provided regarding signal processing and data treatment, as well as data analysis and its biological interpretation in the context of metabolomic studies.

Bispecific antibody characterization by a combination of intact and site-specific/chain-specific LC/MS techniques

Bispecific antibodies (bsAbs) are considered as an important class of biopharmaceutical drugs, with about 160 products in clinical trials. From an analytical point of view, the correct chain-association is one of the most critical challenge to monitor during bsAbs development and production. In the present study, a full analytical workflow has been developed based on the use of various chromatographic modes: size exclusion chromatography (SEC), ion exchange chromatography (IEX), reversed phase liquid chromatography (RPLC), and hydrophilic interaction chromatography (HILIC), all combined with high resolution mass spectrometry (MS). This analytical strategy was applied to Hemlibra® (emicizumab), which is certainly the most successful commercial bsAb to date. Using this strategy, it was possible to monitor the presence of mispaired bsAb species and detect and identify additional post-translational modifications (PTMs).

Ultra-short ion-exchange columns for fast charge variants analysis of therapeutic proteins

The purpose of this work was to study the potential of recently developed ultra-short column hardware for ion exchange chromatography (IEX). Various prototype and commercial columns having lengths of 5, 10, 15, 20 and 50 mm and packed with non-porous 3 µm particles were systematically compared. Both pH and salt gradient modes of elution were evaluated. Similarly, what has been previously reported for reversed phase liquid chromatography (RPLC) mode, an "on-off" retention mechanism was observed in IEX for therapeutic proteins and their fragments (25-150 kDa range). Because of the non-porous nature of the IEX packing material, the column porosity was relatively low (ε = 0.42) and therefore the volumes of ultra-short columns were very small. Based on this observation, it was important to reduce as much as possible all the sources of extra-column volumes (i.e. injection volume, extra-bed volume, detector cell volume and connector tubing volume), to limit peak broadening. With a fully optimized UHPLC system, very fast separations of intact and IdeS digested mAb products were successfully performed in about 1 min using an IEX column with dimensions of 15 × 2.1 mm. This column was selected for high-throughput separations, since it probably offers the best compromise between efficiency and analysis time. For such ultra-fast separations, PEEK tubing was applied to bypass the column oven (column directly connected) to the optical detector via a zero dead volume connection.

Quantitative N-Glycan Profiling of Therapeutic Monoclonal Antibodies Performed by Middle-Up Level HILIC-HRMS Analysis

The identification and accurate quantitation of the various glycoforms contained in therapeutic monoclonal antibodies (mAbs) is one of the main analytical needs in the biopharmaceutical industry, and glycosylation represents a crucial critical quality attribute (CQA) that needs to be addressed. Currently, the reference method for performing such identification/quantitation consists of the release of the N-glycan moieties from the mAb, their labelling with a specific dye (e.g., 2-AB or RFMS) and their analysis by HILIC-FLD or HILIC-MS. In this contribution, the potential of a new cost- and time-effective analytical approach performed at the protein subunit level (middle-up) was investigated for quantitative purposes and compared with the reference methods. The robustness of the approach was first demonstrated by performing the relative quantification of the glycoforms related to a well characterized mAb, namely adalimumab. Then, the workflow was applied to various glyco-engineered mAb products (i.e., obinutuzumab, benralizumab and atezolizumab). Finally, the glycosylation pattern of infliximab (Remicade^®) was assessed and compared to two of its commercially available biosimilars (Remsima^® and Inflectra^®). The middle-up analysis proved to provide accurate quantitation results and has the added potential to be used as multi-attribute monitoring method.

Towards a simple on-line coupling of ion exchange chromatography and native mass spectrometry for the detailed characterization of monoclonal antibodies

This work describes the direct hyphenation of cation exchange chromatography (CEX) with a compact, easy-to-use benchtop Time of Flight mass spectrometer (ToF/MS) for the analytical characterization of monoclonal antibodies (mAbs). For this purpose, a wide range of commercial mAb products (including expired samples and mAb biosimilars) were selected to draw reliable conclusions. From a chromatographic point of view, various buffers and column dimensions were tested. When considering pH response, buffer stability over time and MS compatibility, the best compromise is represented by the following recipe: 50 mM ammonium acetate, titrated to pH 5.0 (mobile phase A) and 160 mM ammonium acetate, titrated to pH 8.5 (mobile phase B). Despite the broader peaks observed with the 2.1 mm i.d. CEX column, this was preferentially selected for CEX-MS operation, since the efficiency loss (caused by extra-column dispersion) was still acceptable while MS compatibility was strongly enhanced (thanks to low flow rate). In terms of MS, it was important to avoid the use of glass-bottled mobile phases, laboratory glassware and glass vials to minimize loss of MS resolution, sensitivity, and mass accuracy due to metal contaminants. With this new CEX-MS setup, straightforward and rapid analysis (in less than 10 min) of charge variants was possible, allowing the separation and identification of several charge variants.

Isolation and Identification of Isocoumarin Derivatives With Specific Inhibitory Activity Against Wnt Pathway and Metabolome Characterization of Lasiodiplodia venezuelensis

The Wnt signaling pathway controls multiple events during embryonic development of multicellular animals and is carcinogenic when aberrantly activated in adults. Breast cancers are dependent on Wnt pathway overactivation mostly through dysregulation of pathway component protein expression, which necessitates the search for therapeutically relevant compounds targeting them. Highly diverse microorganisms as endophytes represent an underexplored field in the therapeutic natural products research. In the present work, the objective was to explore the chemical diversity and presence of selective Wnt inhibitors within a unique collection of fungi isolated as foliar endophytes from the long-lived tropical palm Astrocaryum sciophilum. The fungi were cultured, extracted with ethyl acetate, and screened for their effects on the Wnt pathway and cell proliferation. The endophytic strain Lasiodiplodia venezuelensis was prioritized for scaled-up fractionation based on its selective activity. Application of geometric transfer from analytical HPLC conditions to semi-preparative scale and use of dry load sample introduction enabled the isolation of 15 pure compounds in a single step. Among the molecules identified, five are original natural products described for the first time, and six are new to this species. An active fraction obtained by semi-preparative HPLC was re-purified by UHPLC-PDA using a 1.7 µm phenyl column. 75 injections of 8 µg were necessary to obtain sufficient amounts of each compound for structure elucidation and bioassays. Using this original approach, in addition to the two major compounds, a third minor compound identified as (R)-(-)-5-hydroxymellein (18) was obtained, which was found to be responsible for the significant Wnt inhibition activity recorded. Further studies of this compound and its structural analogs showed that only 18 acts in a highly specific manner, with no acute cytotoxicity. This compound is notably selective for upstream components of the Wnt pathway and is able to inhibit the proliferation of three triple negative breast cancer cell lines. In addition to the discovery of Wnt inhibitors of interest, this study contributes to better characterize the biosynthetic potential of L. venezuelensis.

Ion mobility-high resolution mass spectrometry in doping control analysis. Part II: Comparison of acquisition modes with and without ion mobility

In the second part of this study, a systematic comparison was made between two ion fragmentation acquisition modes, namely data-independent acquisition (DIA) and DIA with ion mobility spectrometry (IMS) technology. These two approaches were applied to the analysis of 192 doping agents in urine. Group I included 102 compounds such as stimulants, diuretics, narcotics, and β2-agonists, while Group II contained 90 compounds included steroids, glucocorticoids, and hormone and metabolic modulators. Important method parameters were examined and compared, including the fragmentation, sensitivity, and assignment capability with the minimum occurrence of false positive hits. The results differed between Group I and II in number of detected fragments when exploring the MS/MS spectra. In Group I only 13%, while in the Group II 64% of the substances had a higher number of fragments in DIA-IMS mode vs. DIA. In terms of sensitivity, the performance of the two modes with and without activated IMS dimension was identical for about 50% of the doping agents. The sensitivity was higher without IMS, i.e. in simple DIA mode, for 20-40% of remaining doping agents. Despite this sensitivity reduction with IMS, 82% of compounds from both Groups met the minimum required performance level (MRPL) criteria of the World Anti-Doping Agency (WADA) when the DIA-IMS mode was applied. Automated data processing is important in routine doping analysis. Therefore, processing methods were optimized and evaluated for the prevalence of false peak assignments by analysing the target substances at different concentrations in urine samples. Overall, a significantly higher number of misidentified compounds was observed in Group II, with an almost 2-fold higher number of misidentifications in DIA compared to DIA-IMS. This result highlights the benefit of the IMS dimension to reduce the rate of false positive in screening analysis. The optimized UHPLC-IM-HRMS method was finally applied to the analysis of urine samples from administration studies including nine doping agents from both Groups. However, to limit the number of interferences from the biological matrix, an emphasis is needed on the adequate settings of the data processing method.

Enantiomeric methadone quantitation on real post-mortem dried matrix spots samples: Comparison of liquid chromatography and supercritical fluid chromatography coupled to mass spectrometry

This study describes two bioanalytical methods for the quantitation of the two methadone enantiomers in dried matrix spots using high performance liquid chromatography coupled to tandem mass spectrometry (HPLC-MS/MS) and high performance supercritical chromatography tandem mass spectrometry (HPSFC-MS/MS). Dried matrix spots were obtained by spotting 10 µL of each sample fluid on a Whatman paper. Methadone and its main metabolite, EDDP, were extracted with 100 µL methanol and subsequently injected into the LC-MS/MS and SFC-MS/MS systems. Enantiomeric separation was achieved with AGP-column for the LC conditions and with Chiralpak IH-3 in SFC. The two methods were fully validated and 93 post-mortem samples were analysed with both analytical methods. Results from validation parameters and results obtained for all post-mortem samples were compared with a significant spearman correlation of r_s = 0.9978 for R-methadone and r_s = 0.9981 for S-methadone. The LC method provided better results in terms of uncertainty, retention factor and resolution, whereas SFC provides better sensitivity, with lower LOD. Median R-/S-methadone ratio in peripheral blood was found equal to 1.60 (N = 32), varying from 0.79 to 4.23. The reported values were in good agreement with previously published results. Based on the results obtained here, SFC-MS/MS can be considered a reliable alternative to the widely used LC-MS/MS for the quantitation of methadone enantiomers in bioanalysis and should be evaluated for other bioanalytical methods. Both methods can be easily and quickly used in toxicological routine analysis for the methadone quantitation in human fluids matrices, even if considering that the polysaccharide coated column IH-3 used in SFC does not allow the enantiomeric EDDP separation.

Inter-laboratory study to evaluate the performance of automated online characterization of antibody charge variants by multi-dimensional LC-MS/MS

An international study was conducted to evaluate the performance and reliability of an online multi-dimensional (mD)-LC-MS/MS approach for the characterization of antibody charge variants. The characterization of antibody charge variants is traditionally performed by time-consuming, offline isolation of charge variant fractions by ion exchange chromatography (IEC) that are subsequently subjected individually to LC-MS/MS peptide mapping. This newly developed mD-LC-MS/MS approach enables automated and rapid characterization of charge variants using much lower sample requirements. This online workflow includes sample reduction, digestion, peptide mapping, and subsequent mass spectrometric analysis within a single, fully-automated procedure. The benefits of using online mD-LC-MS/MS for variant characterization include fewer handling steps, a more than 10-fold reduction in required sample amount, reduced sample hold time as well as a shortening of the overall turnaround time from weeks to few days compared to standard offline procedures. In this site-to-site comparison study, we evaluated the online peptide mapping data collected from charge variants of trastuzumab (Herceptin®) across three international laboratories. The purpose of this study was to compare the overall performance of the online mD-LC-MS/MS approach for antibody charge variant characterization, with all participating sites employing different mD-LC-MS/MS setups (e.g., instrument vendors, modules, columns, CDS software). The high sequence coverage (95%-97%) obtained in each laboratory, enabled a reproducible generation of tryptic peptides and the comparison of values of the charge variants. Results obtained at all three participating sites were in good agreement, highlighting the reliability and performance of this approach, and correspond with data gained by the standard offline procedure. Overall, our results underscore of the benefit mD-LC-MS/MS technology for therapeutic antibody characterization, confirming its potential to become an important tool in the toolbox of protein characterization scientists.

Interlaboratory study of a supercritical fluid chromatography method for the determination of pharmaceutical impurities: Evaluation of multi-systems reproducibility

Modern supercritical fluid chromatography (SFC) is now a well-established technique, especially in the field of pharmaceutical analysis. We recently demonstrated the transferability and the reproducibility of a SFC-UV method for pharmaceutical impurities by means of an inter-laboratory study. However, as this study involved only one brand of SFC instrumentation (Waters®), the present study extends the purpose to multi-instrumentation evaluation. Specifically, three instrument types, namely Agilent®, Shimadzu®, and Waters®, were included through 21 laboratories (n = 7 for each instrument). First, method transfer was performed to assess the separation quality and to set up the specific instrument parameters of Agilent® and Shimadzu® instruments. Second, the inter-laboratory study was performed following a protocol defined by the sending lab. Analytical results were examined regarding consistencies within- and between-laboratories criteria. Afterwards, the method reproducibility was estimated taking into account variances in replicates, between-days and between-laboratories. Reproducibility variance was larger than that observed during the first study involving only one single type of instrumentation. Indeed, we clearly observed an 'instrument type' effect. Moreover, the reproducibility variance was larger when considering all instruments than each type separately which can be attributed to the variability induced by the instrument configuration. Nevertheless, repeatability and reproducibility variances were found to be similar than those described for LC methods; i.e. reproducibility as %RSD was around 15 %. These results highlighted the robustness and the power of modern analytical SFC technologies to deliver accurate results for pharmaceutical quality control analysis.

Empirical correction of non-linear pH gradients and a tool for application to protein ion exchange chromatography

This concept article reports a practical solution to improve the linearity of effluent pH response as observed in pH gradient cation exchange chromatography (CEX). When performing pH gradient CEX, it is not easy to develop buffer systems that will universally provide pH response proportional with the mobile phase (buffer) composition. It is an especially challenging pursuit when exploring MS compatible buffers (e.g. ammonium-acetate, ammonium-carbonate). In addition to "non-proportional" behavior from the mobile phase composition, the chromatographic column itself will sometimes impose an unpredictable impact on the effluent pH. Here, we propose a simple approach based on the on-line measurement of effluent pH response, conversion of pH to mobile phase volume fraction (φ) and then generation of the inverse response function in the time domain. In the end, when setting the inverse function as the gradient program instead of a linear gradient, an improved - ideally linear - pH response can be produced. A simple Excel tool was developed to assist analysts with this correction procedure, and it has been made available by download for public use.

State-of-the-Art Native Mass Spectrometry and Ion Mobility Methods to Monitor Homogeneous Site-Specific Antibody-Drug Conjugates Synthesis

Antibody-drug conjugates (ADCs) are biotherapeutics consisting of a tumor-targeting monoclonal antibody (mAb) linked covalently to a cytotoxic drug. Early generation ADCs were predominantly obtained through non-selective conjugation methods based on lysine and cysteine residues, resulting in heterogeneous populations with varying drug-to-antibody ratios (DAR). Site-specific conjugation is one of the current challenges in ADC development, allowing for controlled conjugation and production of homogeneous ADCs. We report here the characterization of a site-specific DAR2 ADC generated with the GlyCLICK three-step process, which involves glycan-based enzymatic remodeling and click chemistry, using state-of-the-art native mass spectrometry (nMS) methods. The conjugation process was monitored with size exclusion chromatography coupled to nMS (SEC-nMS), which offered a straightforward identification and quantification of all reaction products, providing a direct snapshot of the ADC homogeneity. Benefits of SEC-nMS were further demonstrated for forced degradation studies, for which fragments generated upon thermal stress were clearly identified, with no deconjugation of the drug linker observed for the T-GlyGLICK-DM1 ADC. Lastly, innovative ion mobility-based collision-induced unfolding (CIU) approaches were used to assess the gas-phase behavior of compounds along the conjugation process, highlighting an increased resistance of the mAb against gas-phase unfolding upon drug conjugation. Altogether, these state-of-the-art nMS methods represent innovative approaches to investigate drug loading and distribution of last generation ADCs, their evolution during the bioconjugation process and their impact on gas-phase stabilities. We envision nMS and CIU methods to improve the conformational characterization of next generation-empowered mAb-derived products such as engineered nanobodies, bispecific ADCs or immunocytokines.

Using 1.5 mm internal diameter columns for optimal compatibility with current liquid chromatographic systems

This article describes the use of a new prototype column hardware made with 1.5 mm internal diameter (i.d.) and demonstrates some benefits over the 1.0 mm i.d. micro-bore column. The performance of 2.1, 1.5 and 1.0 mm i.d. columns were systematically compared. With the 1.5 mm i.d. column, the loss of apparent column efficiency can be significantly reduced compared to 1.0 mm i.d. columns in both isocratic and gradient elution modes. In the end, the 1.5 mm i.d. column is almost comparable to 2.1 mm i.d. column from a peak broadening point of view. The advantages of the 1.5 mm i.d. hardware vs 2.1 mm i.d. narrow-bore columns are the lower sample and solvent consumption, and reduced frictional heating effects due to decreased operating flow rates.

Aptamer-based immunoaffinity LC-MS using an ultra-short column for rapid attomole level quantitation of intact mAbs

Quantification of proteins in biofluids has largely involved either traditional ligand binding assays or "bottom-up" mass spectrometry. Recently, top-down mass spectrometry using reversed-phase liquid chromatography (RPLC) paired with high-resolution mass spectrometry (HRMS) has emerged as a promising technique, due to the potential of better identification of post-translational modifications (PTMs), lack of downstream interferences, and less time-consuming sample preparation and analysis times. However, it can be difficult with this approach to robustly obtain high-fidelity MS data, especially when pushing for low limits of detection. To address these issues, we developed a chromatographic device with an optimized form factor and stationary phase to improve protein recovery, while reducing run times. We have observed that by using this device, it is possible to achieve attomole quantitation of mAbs without the addition of carrier proteins and with over three-fold higher throughput than columns employed in previous studies. Moreover, we have devised a novel affinity capture method, based on repurposing a unique aptamer ligand that can give 93% recovery of mAb using only a 2 h incubation. When hyphenated together, these two technologies greatly improve the ability to analyze proteins in complex matrices.