Separation of cyclotron-produced cobalt-55/58m from iron targets using cation exchange chromatography with non-aqueous solvents and extraction chromatography

Cobalt-55 and -58m form a theranostic pair that has relevant properties for cancer research. We report a cation exchange chromatography/extraction chromatography method that separates cyclotron-produced 55/58mCo from 54/57Fe in <1.5 h, recovers >85% Co and achieves [55Co]Co-NOTA and -DOTA AMA 89 ± 48 and 35 ± 7 MBq/nmol (EOB), respectively. Cobalt-55 and -58m were quantitatively labeled to functionalized NOTA at 106 and 50 MBq/nmol (EOB), respectively, corroborating measured AMA. This method is faster than previously published methods and achieves better [55/58mCo]Co-NOTA and -DOTA AMA.

Evaluating the viral clearance ability of continuous monoclonal antibody purification steps, in order to inactivate and/or remove four model viruses

Background and Objectives

Viral clearance studies are an essential part of a manufacturer's plan to ensure the safety of an injectable biologic product. In this way, viral safety is a critical quality attribute for biologics such as monoclonal antibodies (Mabs). Evaluation of virus purification by downstream processes is a key component of risk mitigation. In this study, the capability of continuous monoclonal antibody purification steps was evaluated in the process of instant monoclonal antibody purification in different stages of purification, and the amount of reduction or inactivation of each step was determined.

Materials and Methods

Four enveloped and non-enveloped viral models VSV, Reovirus, EMCV, and HSV1 were used for spiking in selected samples in the designated tests, to have a comprehensive examination of the ability to clear the virus such as the type of genetic material, chemical resistance, and particle size. A TCID50 and qPCR methods were used to measure viral reduction. Two cell lines, Vero (African green monkey kidney) and L929 (Mouse fibroblast) were used for 4 model viruses propagation. The steps that were evaluated included 4 steps monoclonal antibody purification; cation exchange chromatography, acidic pH treatment, affinity chromatography, and nanofiltration.

Results

The nano-filter stage showed the highest viral reduction and cation exchange chromatography showed the lowest reduction. The cumulative decrease using TCID50 is equal to 19.27 [log10] for all steps and for the qPCR method is equal to 12.47 [log10] in three steps of nano-filter, affinity chromatography, and ion exchange chromatography.

Conclusion

The overall average reduction coefficient for all four model viruses is significantly high, which indicates the high capacity of the monoclonal antibody production process in inactivating and removing viruses leads to reducing the load of all four model viruses.

Development of tandem cation exchange chromatography for high purity extracellular vesicle isolation: The effect of ligand steric availability

Purification of extracellular vesicles for research and therapeutic applications requires updated methodology to address the limitations of traditional ultracentrifugation and other size-based separation techniques. Their downfalls include induced extracellular vesicle aggregation, low yields, poor scalability and one-dimensionality of the separation process, as the size or sedimentation speed of extracellular vesicles is often the only selection criterion. Ion exchange chromatography is a promising alternative or supplementary method candidate, as it offers a different approach for extracellular vesicle separation, which is surface charge. For now, mostly anion exchange chromatography has been evaluated for extracellular vesicle purification, as it successfully relies on the strongly negative surface charge of extracellular vesicles. However, as extracellular vesicles are very complex in their structure, also cation exchange chromatography could be applicable, due to individual cationic domains on the extracellular vesicle surface. Here, we compare anion exchange chromatography to different types of cation exchange chromatography for the purification of platelet extracellular vesicle samples also containing plasma-derived impurities. We found that the choice of resin structure used for cation exchange chromatography is critical for binding platelet extracellular vesicles, as a conventional-type cation exchanger was found to only capture and elute less than 20% of extracellular vesicles. With the tentacle-type resin, it was possible to obtain comparable platelet extracellular vesicle yields (over 90%) with cation exchange chromatography compared to anion exchange chromatography, as well as superior purity, especially when it was combined to conventional cation exchange resin.

Quantification of lactoferrin in human milk using monolithic cation exchange HPLC

Human lactoferrin (hLF) is one of the most important whey proteins in human milk, known for its ability to modulate innate host immunity and multifunctional activities for neonatal growth. The objective of this study was to validate an efficient method for the detection and quantification of hLF using a unique technology of cation-exchange high-performance liquid chromatography (HPLC) on CIM® monolithic columns. Human milk samples were collected using manual expression or a breast pump, at different weeks of lactation. After sample preparation, hLF was detected and measured by HPLC method and further confirmed by SDS-PAGE. Selected fractions were analysed also by LC-MS/MS. Presumably, due to the high density of positive charge on the surface of the N-terminal domain, hLF binds strongly to the column and elutes last, enabling the high specificity of this method. The LC-MS/MS analysis indicated that hLF eluted in two clearly separated peaks, presumably representing two different molecular species of hLF. hLF concentration in the human milk samples ranged from 2.03 mg/mL to 5.79 mg/mL and was not significantly affected by the sample collection method whereas it was negatively correlated with the stage of lactation. These results suggest that cation exchange chromatography is an accurate, efficient, and robust method for the detection and quantification of hLF.

Two peak elution behavior of a monoclonal antibody in cation exchange chromatography as a screening tool for excipients

Aggregation of proteins is a critical quality attribute and a major concern during the purification of therapeutic proteins, like monoclonal antibodies. In-solution experiments applying different stress scenarios, e.g., mechanical, or physical stresses, can determine the overall conformational stability of the protein to enhance drug product shelf-life. Several groups have reported surface-induced unfolding and aggregation of monoclonal antibodies and their derivatives during cation exchange chromatography, which results in a two-peak elution behavior of the protein and its species. We have investigated universal influencing factors, like temperature and hold time, on this phenomenon. The formation of the second peak is a kinetic process, which is strongly influenced by temperature during the hold time. However, our main focus was the application of excipients and their influence on the two-peak elution behavior. We compared the on-column screening results with results obtained through a "traditional" in-solution screening using nanoDSF. Mostly, stabilizing excipients, like Sucrose, show their stabilizing abilities in both systems, but some discrepancies, e.g., using Arginine, between the two orthogonal techniques show the potential of the on-column screening system to lead to unexpected results, which would not necessarily be visible in in-solution experiments.

Microfluidic Chromatography for Enhanced Amino Acid Detection at Ocean Worlds

Increasing interest in the detection of biogenic signatures, such as amino acids, on icy moons and bodies within our solar system has led to the development of compact in situ instruments. Given the expected dilute biosignatures and high salinities of these extreme environments, purification of icy samples before analysis enables increased detection sensitivity. Herein, we outline a novel compact cation exchange method to desalinate proteinogenic amino acids in solution, independent of the type and concentration of salts in the sample. Using a modular microfluidic device, initial experiments explored operational limits of binding capacity with phenylalanine and three model cations, Na⁺, Mg²⁺, and Ca²⁺. Phenylalanine recovery (94-17%) with reduced conductivity (30-200 times) was seen at high salt-to-amino-acid ratios between 25:1 and 500:1. Later experiments tested competition between mixtures of 17 amino acids and other chemistries present in a terrestrial ocean sample. Recoveries ranged from 11% to 85% depending on side chain chemistry and cation competition, with concentration shown for select high affinity amino acids. This work outlines a nondestructive amino acid purification device capable of coupling to multiple downstream analytical techniques for improved characterization of icy samples at remote ocean worlds.

Influence of ligand density variations on the two peak elution behavior of a monoclonal antibody in cation exchange chromatography

Cation exchange chromatography, as part of the monoclonal antibody purification train, is known as a mild polishing technique. However, in the last couple of years, more and more publications have shown unusual elution behavior, resulting from e.g. on-column (reversible) unfolding and aggregation of the predominantly mAb molecules. The stability of the investigated protein seems to play a significant role in this phenomenon. We have used a glycosylated IgG1 antibody as a model protein and investigated several influencing factors, including pH value and ligand density variations of three prototype Fractogel® cation exchange resins. Ligand density, pH and salt concentration are the main contributing factors in the Donnan effect, i.e. distribution of ions, between resin pore volume and bulk volume. This leads to a significantly lower pH value the protein is subjected to during the on-column hold time and therefore influences the conformational stability of our protein. Nano-DSF and kinetic SEC measurements show that the protein is destabilized at low pH values, but also, that the binding to the CEX resin and the elution with increasing salt concentration is responsible for the resulting two-peak elution behavior and partially reversible unfolding and aggregation.

Application of cation exchange chromatography in bind and elute and flowthrough mode for the purification of enteroviruses

Members of the enterovirus genus are promising oncolytic agents. Their morphogenesis involves the generation of both genome-packed infectious capsids and empty capsids. The latter are typically considered as an impurity in need of removal from the final product. The separation of empty and full capsids can take place with centrifugation methods, which are of low throughput and poorly scalable, or scalable chromatographic processes, which typically require peak cutting and a significant trade-off between purity and yield. Here we demonstrate the application of packed bed cation exchange (CEX) column chromatography for the separation of empty capsids from infectious virions for a prototype strain of Coxsackievirus A21. This separation was developed using high throughput chromatography techniques and scaled up as a bind and elute polishing step. The separation was robust over a wide range of operating conditions and returned highly resolved empty and full capsids. The CEX step could be operated in bind and elute or flowthrough mode with similar selectivity and returned yields greater than 70% for full mature virus particles. Similar performance was also achieved using a selection of other bead based CEX chromatography media, demonstrating general applicability of this type of chromatography for Coxsackievirus A21 purification. These results highlight the wide applicability and excellent performance of CEX chromatography for the purification of enteroviruses, such as Coxsackievirus A21.

Production and Conjugation of Truncated Recombinant Diphtheria Toxin to VEGFR-2 Specific Nanobody and Evaluation of its Cytotoxic Effect on PC-3 Cell Line

Immunotoxins have represented a great potency in targeted therapeutics to encounter tumors. They consist of a protein toxin conjugated to a targeting moiety, which recognizes a specific antigen on surface of cancer cells and accordingly induces cell death by toxin segment. The targeting part could be a nanobody, which is a group of antibodies composed of an only functional single variable heavy chain (VHH).Therefore, this study was done to produce an immunotoxin (VGRNb-DT) by chemical conjugation of a truncated diphtheria toxin moiety to an anti-vascular endothelial growth factor receptor 2(VEGFR-2) nanobody, and to identify effectiveness of immunotoxin in recognizing the VEGFR-2- positive cancer cells and inhibiting cell growth and survival. Diphtheria toxin was expressed and purified by nickel affinity chromatography, and accordingly, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot analysis confirmed its expression. Function of heterobifunctional crosslinkers, Sulfo-SMCC (sulfosuccinimidyl-4-(N-maleimidomethyl) cyclohexane-1-carboxylate), and SATP (N-succinimidyl-S- acetylthiopropionate) for bioconjugation purposes was acknowledged by cation exchange high-performance liquid chromatography (HPLC). Cytotoxicity of immunotoxin was evaluated on the VEGFR-2 positive PC-3 cell line by MTT assay. Overexpression of VEGFR-2 in the PC-3 cell line allowed immunotoxin to recognize them by anti-VEGFR-2 nanobodies. The concentrations above 5 μg/ml represented a significant decrease in cell survival rate in PC-3 cells compared to HEK293 cells (VEGFR-2 negative cells) as controls.VGRNb-DT demonstrated a successful bioconjugation; furthermore, variable concentrations were correlated with cell death in prostate cancer PC-3 cells.

Mechanistic modeling and simulation of a complex low and high loading elution behavior of a polypeptide in cation exchange chromatography

The mechanistic modeling of preparative liquid chromatography is still a challenging task. Non-ideal thermodynamic conditions may require activity coefficients for the mechanistic description of preparative chromatography. In this work, a chromatographic cation exchange step with a polypeptide having a complex elution behavior in low and high loading situations is modeled. Model calibration in the linear range of the isotherm is done by applying counterion-induced linear gradient elution experiments between pH 3.3 and pH 4.3. Inverse fitting with column loads up to 25 mg/mL_CV is performed for parameter estimation in the non-linear range. The polypeptide elution peak shows an anti-Langmuirian behavior with fronting under low loading conditions and a switch to a Langmuirian behavior with increasing load. This unusual elution behavior could be described with an extended version of the sigmoidal Self-Association isotherm, including two activity coefficients for the polypeptide and counterion in solution. The activity coefficient of the solute polypeptide shows a strong influence on the model parameters and is crucial in the linear and non-linear range of the isotherm. The modeling procedure results in a unique and robust model parameter set that is sufficient to describe the complex elution behavior and allows modeling over the full isotherm range. This article is protected by copyright. All rights reserved.

HPLC method with post-column derivatization for the analysis of endogenous histidine in human saliva validated using the total-error concept

Histidine (His) is an essential amino acid that plays an important biological role and associated with various pathological conditions. A simple and reliable method for the determination of endogenous histidine in human saliva was optimized and validated. The analyte was separated from the saliva matrix by cation exchange chromatography and detected fluorimetrically (λ_ex/λ_em = 360/440 nm) after online, specific post-column derivatization (PCD) reaction with o-phthalaldehyde. The chemical and instrumental variables of the post-column reaction were optimized using Box-Behnken experimental design to achieve maximum sensitivity. Method validation was carried out employing the total-error concept. Histidine could be analyzed reliably in the range of 0.5-5.0 μΜ, with an LOD (S/N = 3) of 50 nM. Monte Carlo simulations and capability analysis were used to investigate the ruggedness of the PCD reaction. The sampling strategy, sample preparation and stability were also investigated. Seventeen saliva samples were successfully analyzed with histidine levels being in the range of 2.7-19.5 μΜ.

New and efficient purification process for recombinant human insulin produced in Escherichia coli

A new and efficient purification process for recombinant human insulin production was developed by exploring new resins and optimizing purification steps from E. coli inclusion body washing to insulin polishing. A combined additives inclusion body wash protocol drastically improved efficiency in clarifying ZZ-proinsulin samples. ZZ-proinsulin recovery increased three-fold under optimized solubilization and sulfitolysis incubation temperature and duration. Desalting with Bio-Gel P4 and P6 resulted in higher sample loading and product recovery compared to conventional resins. A higher recovery (96%) and purity (81%) of ZZ-proinsulin were achievable with the Nuvia S cation exchanger for proinsulin purification compared to a reported process using expensive affinity chromatography resin. As the first step for insulin purification, process scale-up is more economical and practical when Nuvia HR-S cation exchanger was used instead of commonly used reversed-phase chromatography. Nuvia HR-S was highly effective in removing ZZ fusion protein (90% removal) after enzymatic cleavage, although ZZ fusion protein has a very close theoretical pI to human insulin, which was supposedly challenging to be removed by cation exchange chromatography. Also, insulin can be eluted at a lower ethanol % using Nuvia HR-S compared to other reported processes and is thus more environmentally sustainable. Recombinant human insulin was obtained with over 98% purity in just a single reversed-phase polishing step, which is comparable to the reference standard. The process workflow presented here can be potentially applied for the development of purification workflow for insulin analogs or other peptide products derived from E. coli inclusion body.Key points• Drastic efficiency improvement for inclusion body wash with combined additives.• High recovery of proinsulin purification with high capacity cation exchange resin.• Effective removal of fusion tag at lower ethanol % with high-resolution resin.

Exploration of fiber-based cation exchange adsorbents for the removal of monoclonal antibody aggregates

Cation exchange chromatography (CEX) is a widely used technique for the removal of monoclonal antibody (mAb) aggregates. At present, resins are mainly used for this purpose, as convective types of adsorbents such as membrane adsorbers (MAs) have often not demonstrated overall comparable performance for this particular application. Fiber-based adsorbents can overcome the current limitations of MAs with respect to permeability, binding capacity, and adsorbent cost, and could therefore be a viable alternative to resins for the removal of mAb aggregates. It has not been evaluated, however, whether and under which conditions the use of such adsorbents is feasible for this purpose. In the present study, the use of fiber-based CEX adsorbents for mAb aggregate removal was examined. Two types of fiber-based adsorbents, an uncontrolled grafted and a controlled grafted fiber-based adsorbent, were evaluated with respect to permeability, dynamic mAb binding capacity (DBC), resolution capabilities, and the performance in bind and elute (B/E) and frontal chromatography mode with respect to typical performance indicators. The permeabilities of the fiber-based adsorbents ranged from 200 to 1700 mD, making it possible to use the fiber-based adsorbents at larger bed heights than membrane adsorbers with fast mobile phase velocities. Antibody DBCs ranged from 20 to 41 g/L at 150 cm/h, and at higher mobile phase velocities exceeded the DBC of an existing resin material, Poros 50 HS, which has frequently been used for aggregate removal. Both fiber types showed good resolution capabilities of monomer and aggregates, and provided better resolution per column length than Poros 50 HS. Typical purity and yield constraints were fulfilled for both fiber types in both B/E and frontal chromatography mode for mobile phase velocities ranging up to 480 cm/h and 1060 cm/h. The overall performance of the controlled grafted fibers was found to be superior to the performance of uncontrolled grafted fiber-based adsorbents due to higher productivity and lower buffer consumption. The overall performance of the fiber-based adsorbents was found to be comparable to the performance of Poros 50 HS at typical operating conditions. The results in this study indicate that the use of fiber-based adsorbents for mAb aggregate removal is feasible with a performance that is comparable to the performance of an existing resin material. Depending on the cost of the adsorbents and the use scenario, the usage of such adsorbents could be beneficial.

Clean and folded: Production of active, high quality recombinant human interferon-λ1

Type III interferons exhibit antiviral activity against influenza viruses, coronaviruses, rotaviruses, and others. In addition, this type of interferon theoretically has therapeutic advantages, in comparison with type I interferons, due to its ability to activate a narrower group of genes in a relatively small group of target cells. Hence, it can elicit more targeted antiviral or immunomodulatory responses. Obtaining biologically-active interferon lambda (hIFN-λ₁) is fraught with difficulties at the stage of expression in soluble form or, in the case of expression in the form of inclusion bodies, at the stage of refolding. In this work, hIFN-λ₁ was expressed in the form of inclusion bodies, and a simple, effective refolding method was developed. Efficient and scalable methods for chromatographic purification of recombinant hIFN-λ₁ were also developed. High-yield, high-purity product was obtained through optimization of several processes including: recombinant protein expression; metal affinity chromatography; cation exchange chromatography; and an intermediate protein refolding stage. The obtained protein was shown to feature expected specific biological activity in line with published effects: induction of MxA gene expression in A549 cells and antiviral activity against influenza A virus.

Determination of histidine in human serum and urine by cation exchange chromatography coupled to selective on-line post column derivatization

A reliable and highly selective method for the determination of histidine in human serum and urine is described. Histidine was separated from the matrix by cation exchange chromatography and detected selectively using on-line post column derivatization and fluorimetric detection. Unique reaction of histidine with o-phthalaldehyde in the absence of nucleophilic compounds offered specific detection in the complex biological substrate. Linearity was obeyed in the range of 0.5 - 25 μmol L-1 with a limit of detection of 0.160 μmol L-1. The absence of matrix effect (<5%) enabled the processing of real samples after minimal pretreatment. Endogenous histidine has been determined in human serum in the range of 78 - 119 μmol L-1 and random human urine in the range of 266 - 2034 μmol L-1. The percent recoveries were satisfactory in all cases, ranging between 89 and 114%.

Experimental investigation and mass transfer modelling of 3D printed monolithic cation exchangers

3D printing has recently found application in chromatography as a means to create ordered stationary phases with improved separation efficiency. Currently, 3D printed stationary phases are limited by the lack of 3D printing materials suitable for chromatographic applications, and require a strict compromise in terms of desired resolution, model size and the associated print time. Modelling of mass transfer in 3D printed monoliths is also fundamental to understand and further optimise separation performance of 3D printed stationary phases. In this work, a novel 3D printing material was formulated and employed to fabricate monolithic cation exchangers (CEXs) with carboxyl functionalities. CEXs were printed with ligand densities of 0.7, 1.4, 2.1 and 2.8 mmol/g and used in batch adsorption experiments with lysozyme as model protein. All CEXs demonstrated high binding strength towards lysozyme, with maximum binding capacities of up to 108 mg/mL. The experimental results were described using mass transfer models based on lumped pore diffusion and lumped solid diffusion mechanisms adapted to reflect the complex geometry of the 3D printed monoliths. An exact 3D model as well as less computationally demanding 1D and 2D approximations were evaluated in terms of their quality to capture the experimental trend of batch adsorption kinetic data. Overall, the model results indicate that mass transfer in the fabricated CEXs is mostly controlled by pore diffusion at high protein concentrations in the mobile phase, with solid diffusion becoming important at low protein concentrations. Also, the kinetic data were approximated equally well by both the full 3D model as well as the 2D approximation, indicating leaner mathematical models of lower dimensionality can be employed to describe mass transfer in complex three dimensional geometries. We believe this work will help spur the development of 3D printable materials for separations and aid in the development of quantitative platforms to evaluate and optimise the performance of 3D printed monoliths.

Selective post-column derivatization coupled to cation exchange chromatography for the determination of histamine and its precursor histidine in fish and Oriental sauce samples

Histamine is a biogenic amine that is formed from histidine by action of the enzyme histidine decarboxylase and can be toxic at high intakes. Thus, the quantification of these analytes in foods constitutes a significant axis of food safety. In this study we present the development, validation and application of a new method for the determination of histamine and its precursor histidine in fish products and oriental sauces. The analytes were separated rapidly through a cation exchange column using an acidic mobile phase (7 mmol L^-1 nitric acid) and reacted downstream with o-phthalaldehyde in post-column mode in the absence of nucleophilic reagents. The derivatives were detected spectrofluorimetrically at λ_ex/λ_em. = 360/440 nm. Following investigation of the chromatographic and post-column conditions, the method was validated as for its intended applications. The limits of detection were 0.16 and 0.17 μmol L^-1 for histidine and histamine respectively (ca. 0.1 mg kg^-1) and the precision was better than 5%. Various food samples were successfully analyzed without matrix interferences following minimal pretreatment. The percent recoveries ranged between 91.3 and 117.9%.

Bridging size and charge variants of a therapeutic monoclonal antibody by two-dimensional liquid chromatography

Monoclonal antibodies are heterogeneous in nature and may contain numerous variants with differences in size, charge, and hydrophobicity, which may impact clinical efficacy, immunogenicity, and safety. Characterization of antibody variants is necessary to build structure-function correlation and establish a proper control strategy. Isolation and enrichment of variants by conventional chromatographic peak fractionation is labor-intensive and time-consuming. The instability of fractions during isolation and subsequent characterization may also be a concern. Hence, it is desirable to analyze antibody variants in an online and real-time manner. Here we demonstrate a 2D-LC methodology - multiple heart-cutting IEC-SEC- as an investigational tool to facilitate a charge variant characterization study. Both IEC modes - anion exchange (AEX) and cation exchange (CEX) chromatography are discussed. Using this approach, direct bridging of size and charge variants of an antibody molecule was achieved without offline peak fractionation. It was observed that antibody aggregates elute late on both the AEX and CEX columns, presumably due to secondary hydrophobic interactions. Additionally, we overcame the solvent mismatch issue and developed a 2D SEC-IEC method to confirm the bridging results. This is the first reported SEC-IEC 2D-LC application for the characterization of antibody size and charge variants.

Practical considerations on the particle size and permeability of ion-exchange columns applied to biopharmaceutical separations

The goal of this study was to better understand the possibilities and limitations of modern cation exchange chromatography (CEX) columns for the separation of protein biopharmaceuticals (typically mAbs and related products). Several commercial and research columns consisting of a non-porous polymeric core particle with a thin hydrophilic coating and grafted ion-exchanger sulfonate groups, were compared. The impact of particle size, porosity and packing pressure on the separation of therapeutic proteins was evaluated in a systematic way. First, it was shown that the porosity of modern CEX columns depends on the applied conditions, and lower apparent porosity as well as increased column pressures were observed when using low ionic strength mobile phase (less than 0.01 M NaCl), due to swelling. Column pressure seemed to be dependent on the 1/d_p³ to 1/d_p⁵ relationships with particle size, depending on whether 0.3 M NaCl or pure water was used as mobile phase, respectively. Using 5 cm long columns packed with 2 or 2.5 µm particles could easily result in higher than 1000 bar pressure drops when the mobile phase ionic strength is low. Therefore, it is recommended that particle size not be decreased to below 2.5 µm so that technologies can remain compatible with the current state of ultra-high pressure (UHPLC) instrumentation. This recommendation is underscored by the fact that a decrease in particle size does not produce improved separations, since the particles are non-porous (no intra-particle diffusion nor resistance to mass transfer) and that large solutes follow an on-off (bind and elute) type retention mechanism. The only advantage of CEX columns packed with small particles is that they can provide more specific surface area per unit length of column, and thus facilitate higher throughput methods. In conclusion, it appears that there is no need to further decrease the particle size in CEX since decreasing their particle size may result in more drawbacks than benefits.

Affinity profiling of monoclonal antibody and antibody-drug-conjugate preparations by coupled liquid chromatography-surface plasmon resonance biosensing

Monoclonal antibodies (mAbs) and antibody-drug conjugates (ADCs) are highly potent biopharmaceuticals designed for targeted cancer therapies. mAbs and ADCs can undergo modifications during production and storage which may affect binding to target receptors, potentially altering drug efficacy. In this work, liquid chromatography was coupled online to surface plasmon resonance (LC-SPR) to allow label-free affinity evaluation of mAb and ADC sample constituents (size and charge variants), under near-native conditions. Trastuzumab and its ADC trastuzumab emtansine (T-DM1) were used as a test sample and were analyzed by aqueous size-exclusion chromatography (SEC)-SPR before and after exposure to aggregate-inducing conditions. SEC-SPR allowed separation of the formed aggregates and measurement of their affinity towards the ligand-binding domain of the human epidermal growth factor receptor 2 (HER2) receptor immobilized on the surface of the SPR sensor chip. The monomer and aggregates of the mAb and ADC were shown to have similar antigen affinity. Conjugation of drugs to trastuzumab appeared to accelerate the aggregate formation. In addition, cation-exchange chromatography (CEX) was coupled to SPR enabling monitoring the maximum ligand-analyte binding capacity (R_max) of individual charge variants present in mAbs. Deamidated species and lysine variants in trastuzumab sample were separated but did not show different binding affinities to the immobilized HER2-binding domain. In order to allow protein variant assignment, parallel MS detection was added to the LC-SPR setup using a column effluent split. The feasibility of the LC-MS/SPR system was demonstrated by analysis of trastuzumab and T-DM1 providing information on antibody glycoforms and/or determination of the drug-to-antibody ratio (DAR), while simultaneously monitoring binding of eluting species to HER2.

Graphical abstract

Determination of isoelectric points and relative charge variants of 23 therapeutic monoclonal antibodies

Despite the popularity of therapeutic monoclonal antibodies (mAbs), data relative to their ionic physico-chemical properties are very scarce in the literature. In this work, isoelectric points (pIs) of 23 Food and Drug Administration (FDA) and European Medicines Agency (EMA) approved mAbs were determined by imaged capillary isoelectric focusing (icIEF), and ranged from 6.1 to 9.4. The obtained values were in good agreement with those calculated by both Vector NTI and MassLynx softwares. icIEF can therefore be considered as a reference technique for such a determination. The relative percentages of acidic and basic variants determined by cation exchange chromatography (CEX) using both salt- and pH-gradients were comprised between 15% and 30% for most mAbs and were in good agreement with each other, whereas generic icIEF seems to overestimate the amount of acidic charge variants in mAb products. To our knowledge, this is the first study focusing on the ionic properties of a wide range of FDA and EMA approved reference mAbs, using both generic chromatographic and electrophoretic methodologies. To illustrate the interest of the study for mAb developability purposes, ionic properties of a clinical mAb candidate (dalotuzumab) were also investigated.

Microheterogeneity of therapeutic monoclonal antibodies is governed by changes in the surface charge of the protein

It has previously been shown for individual antibodies, that the microheterogenity pattern can have a significant impact on various key characteristics of the product. The aim of this study to get a more generalized understanding of the importance of microheterogeneity. For that purpose, the charge variant pattern of various different commercially available therapeutic mAb products was compared using Cation-Exchange Chromatography with linear pH gradient antigen affinity, Fc-receptor affinity, antibody dependent cellular cytotoxicity (ADCC) and conformational stability. For three of the investigated antibodies, the basic charge variants showed a stronger binding affinity towards FcγRIIIa as well as an increased ADCC response. Differences in the conformational stability of antibody charge variants and the corresponding reference samples could not be detected by differential scanning calorimetry. The different biological properties of the mAb variants are therefore governed by changes in the surface charge of the protein and not by an altered structure. This can help to identify aspects of microheterogeneity that are critical for product quality and can lead to further improvements in the development and production of therapeutic antibody products.

Production and purification of Scandium-47: A potential radioisotope for cancer theranostics

In this study, production of ⁴⁷Sc radionuclide by irradiating the natural titanium dioxide powder (TiO₂) in the fast neutron flux (~3*10¹³ncm^-2s^-1) for 4 days in Tehran Research Reactor (TRR, Iran) and separation from titanium target was investigated. The study showed the feasibility of production ⁴⁷Sc by TRR. The separation efficiency and radiochemical purity (ScCl₃) of radio-scandium, ⁴⁷Sc radionuclide purity were obtained 98%, 99% and 88% respectively.

Simplified in vitro refolding and purification of recombinant human granulocyte colony stimulating factor using protein folding cation exchange chromatography

Protein folding-strong cation exchange chromatography (PF-SCX) has been employed for efficient refolding with simultaneous purification of recombinant human granulocyte colony stimulating factor (rhG-CSF). To acquire a soluble form of renatured and purified rhG-CSF, various chromatographic conditions, including the mobile phase composition and pH was evaluated. Additionally, the effects of additives such as urea, amino acids, polyols, sugars, oxidizing agents and their amalgamations were also investigated. Under the optimal conditions, rhG-CSF was efficaciously solubilized, refolded and simultaneously purified by SCX in a single step. The experimental results using ribose (2.0M) and arginine (0.6M) combination were found to be satisfactory with mass yield, purity and specific activity of 71%, ≥99% and 2.6×10(8)IU/mg respectively. Through this investigation, we concluded that the SCX refolding method was more efficient than conventional methods which has immense potential for the large-scale production of purified rhG-CSF.

Characterization of asparagine 330 deamidation in an Fc-fragment of IgG1 using cation exchange chromatography and peptide mapping

Deamidation is one of the most common degradation pathways for proteins and frequently occurs at "hot spots" with Asn-Gly, Asn-Ser or Asn-Thr sequences. Occasionally, deamidation may occur at other motifs if the local protein structure can participate or assist in the formation of the succinimide intermediate. Here we report the use of a chymotryptic peptide mapping method to identify and characterize a deamidated form of an IgG1 which was observed as an acidic peak in the cation exchange chromatography (CEX). The antibody was formulated in sodium acetate buffer, pH 5.3 and this deamidated form was observed mainly under thermal stress conditions. It was found that the IgG1 molecule with deamidation in the Fc region at asparagine residue 330 (in a Val-Ser-Asn-Lys motif) is the predominant form in this CEX peak, and was missed by tryptic mapping because the peptides are hydrophilic and elute near the void volume. In addition, a domain-based CEX method using papain digestion was developed to monitor the Asn 330 deamidation. These methods revealed that the Fc deamidation occurs mainly at Asn 330 in the VSNK motif at pH 5.3, whereas at pH 7.5, deamidation occurs predominantly at Asn 389 and Asn 394 in the NGQPENNYK motif.