Impact of host cell line choice on glycan profile

Unique challenges required reassessment and alterations to critical reagents to rescue a neutralizing antibody assay

Aim: To redevelop a neutralizing antibody (NAb) assay to be much more drug tolerant, have a large dynamic range and have high inhibition when using high levels of positive control (PC). Materials & methods: Early assay data suggested that typical biotin labeling of the capture reagent (Drug 1, produced in a human cell line) was blocking it from binding with the PC or the detection target, and that the detection target was out competing the PC. Methodical biotin labeling experiments were performed at several challenge ratios and an Fc linker was added to the detection target. Results & conclusion: A larger dynamic range, high inhibition and higher drug tolerance were achieved by adding an acid dissociation step to the assay, performing atypical biotin labeling of Drug 1 and switching to a detection target that contained an Fc linker to increase steric hinderance and decrease its binding affinity to Drug 1.

Preclinical study and first-in-human imaging of [18F]FAP-2286, and comparison with 2-[18F]FDG PET/CT in various cancer patients

PURPOSE

Fibroblast-activated protein (FAP) is highly expressed in cancer-associated fibroblasts (CAFs) of many solid cancers, but low or absent in normal tissues. Our study aimed to develop a novel FAP-specific tracer, namely [18F]FAP-2286, and evaluated its performance in comparison with well-established agents such as [18F]FAPI-42 and [68Ga]Ga-FAP-2286 in preclinical research, as well as 2-[18F]FDG in pilot clinical study.

METHODS

[18F]FAP-2286 was manually synthesized in accordance with Good Manufacturing Practice (GMP). Subsequent investigations encompassed cell uptake, competitive binding affinity, internalization and efflux assays using HT-1080hFAP cell lines. PET imaging and biodistribution studies were conducted in HEK-293ThFAP, A549hFAP, HT-1080hFAP tumor-bearing mice as well as HEK-293T, A549 and HT-1080 control groups. Furthermore, clinical evaluation of [18F]FAP-2286 was performed in fifteen patients with various cancers compared to 2-[18F]FDG PET.

RESULTS

The radiolabeling yield of [18F]FAP-2286 was 30.53 ± 5.20%, with a radiochemical purity exceeding 97%. In cell assays, [18F]FAP-2286 showed specific uptake, high internalization fraction and low cellular efflux. Rapid tumor uptake and satisfactory tumor retention was observed on micro-PET imaging and cancer patients. Meanwhile, the clinical research demonstrated that [18F]FAP-2286 may represent an alternative for low glucose-metabolism malignant tumors PET imaging such as gastric cancers.

CONCLUSION

[18F]FAP-2286 showed superior imaging quality including rapid and high target uptake and satisfactory retention in both tumor-bearing mice and cancer patients. It may emerge as a promising candidate for early or delayed phase imaging and 2-[18F]FDG non-avid cancers PET scan.

Recent advances in microscale separation techniques for glycome analysis

The glycomic analysis holds significant appeal due to the diverse roles that glycans and glycoconjugates play, acting as modulators and mediators in cellular interactions, cell/organism structure, drugs, energy sources, glyconanomaterials, and more. The glycomic analysis relies on liquid-phase separation technologies for molecular purification, separation, and identification. As a miniaturized form of liquid-phase separation technology, microscale separation technologies offer various advantages such as environmental friendliness, high resolution, sensitivity, fast speed, and integration capabilities. For glycan analysis, microscale separation technologies are continuously evolving to address the increasing challenges in their unique manners. This review discusses the fundamentals and applications of microscale separation technologies for glycomic analysis. It covers liquid-phase separation technologies operating at scales generally less than 100 µm, including capillary electrophoresis, nanoflow liquid chromatography, and microchip electrophoresis. We will provide a brief overview of glycomic analysis and describe new strategies in microscale separation and their applications in glycan analysis from 2014 to 2023.

Glycan-directed SARS-CoV-2 inhibition by leek extract and lectins with insights into the mode-of-action of Concanavalin A

Four years after its outbreak, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remains a global challenge for human health. At its surface, SARS-CoV-2 features numerous extensively glycosylated spike proteins. This glycan coat supports virion docking and entry into host cells and at the same time renders the virus less susceptible to neutralizing antibodies. Given the high genetic plasticity of SARS-CoV-2 and the rapid emergence of immune escape variants, targeting the glycan shield by carbohydrate-binding agents emerges as a promising strategy. However, the potential of carbohydrate-targeting reagents as viral inhibitors remains underexplored. Here, we tested seven plant-derived carbohydrate-binding proteins, called lectins, and one crude plant extract for their antiviral activity against SARS-CoV-2 in two types of human lung cells: A549 cells ectopically expressing the ACE2 receptor and Calu-3 cells. We identified three lectins and an Allium porrum (leek) extract inhibiting SARS-CoV-2 infection in both cell systems with selectivity indices (SI) ranging between >2 and >299. Amongst these, the lectin Concanavalin A (Con A) exerted the most potent and broad activity against a panel of SARS-CoV-2 variants. We used multiplex super-resolution microscopy to address lectin interactions with SARS-CoV-2 and its host cells. Notably, we discovered that Con A not only binds to SARS-CoV-2 virions and their host cells, but also causes SARS-CoV-2 aggregation. Thus, Con A exerts a dual mode-of-action comprising both, antiviral and virucidal, mechanisms. These results establish Con A and other plant lectins as candidates for COVID-19 prevention and basis for further drug development.

Reprogramming anchorage dependency to develop cell lines for recombinant protein expression

As the biopharmaceutical industry continues to mature in its cost-effectiveness and productivity, many companies have begun employing larger-scale biomanufacturing and bioprocessing protocols. While many of these protocols require cells with anchorage-independent growth, it remains challenging to induce the necessary suspension adaptations in many different cell types. In addition, although transfection efficiency is an important consideration for all cells, especially for therapeutic protein production, cells in suspension are generally more difficult to transfect than adherent cells. Thus, much of the biomanufacturing industry is focused on the development of new human cell lines with properties that can support more efficient biopharmaceutical production. With this in mind, we identified a set of "Adherent-to-Suspension Transition" (AST) factors, IKZF1, BTG2 and KLF1, the expression of which induces adherent cells to acquire anchorage-independent growth. Working from the HEK293A cell line, we established 293-AST cells and 293-AST-TetR cells for inducible and reversible reprogramming of anchorage dependency. Surprisingly, we found that the AST-TetR system induces the necessary suspension adaptations with an accompanying increase in transfection efficiency and protein expression rate. Our AST-TetR system therefore represents a novel technological platform for the development of cell lines used for generating therapeutic proteins.

The impact of glycosylation on the structure, function, and interactions of CD14

CD14 is an innate immune receptor that senses pathogen-associated molecular patterns, such as lipopolysaccharide, to activate the innate immune response. Although CD14 is known to be glycosylated, detailed understanding about the structural and functional significance of this modification is still missing. Herein, an NMR and MS-based study, assisted by MD simulations, has provided a 3D-structural model of glycosylated CD14. Our results reveal the existence of a key N-glycosylation site at Asn282 that exclusively contains unprocessed oligomannnose N-glycans that perfectly fit the concave cavity of the bent-solenoid shaped protein. This site is not accessible to glycosidases and is fundamental for protein folding and secretion. A second N-site at Asn151 displays mostly complex N-glycans, with the typical terminal epitopes of the host cell-line expression system (i.e. βGal, α2,3 and α2,6 sialylated βGal, here), but also particularities, such as the lack of core fucosylation. The glycan at this site points outside the protein surface, resulting in N-glycoforms fully exposed and available for interactions with lectins. In fact, NMR experiments show that galectin-4, proposed as a binder of CD14 on monocytes to induce their differentiation into macrophages-like cells, interacts in vitro with CD14 through the recognition of the terminal glycoepitopes on Asn151. This work provides key information about CD14 glycosylation, which helps to better understand its functional roles and significance. Although protein glycosylation is known to be dynamic and influenced by many factors, some of the features found herein (presence of unprocessed N-glycans and lack of core Fuc) are likely to be protein specific.

Development, preclinical evaluation and preliminary dosimetry profiling of SB03178, a first-of-its-kind benzo[h]quinoline-based fibroblast activation protein-α-targeted radiotheranostic for cancer imaging and therapy

Fibroblast activation protein-α (FAP) is a marker of cancer-associated fibroblasts (CAFs) that constitute a significant portion of most carcinomas. Since it plays a critical role in tumor growth and metastasis, its timely detection to identify tumor lesions in early developmental stages using targeted radiopharmaceuticals has gained significant impetus. In the present work, two novel FAP-targeted precursors SB03178 and SB04033 comprising of an atypical benzo[h]quinoline construct were synthesized and either chelated to diagnostic radionuclide gallium-68 or therapeutic radionuclide lutetium-177, with ≥90% radiochemical purities and 22-76% decay-corrected radiochemical yields. natGa-labeled complexes displayed dose-dependent FAP inhibition, with binding potency of natGa-SB03178 being ∼17 times higher than natGa-SB04033. To evaluate their pharmacokinetic profiles, PET imaging and ex vivo biodistribution analyses were executed in FAP-overexpressing HEK293T:hFAP tumor-bearing mice. While both tracers displayed clear tumor visualization that was primarily FAP-arbitrated, with negligible uptake in most peripheral tissues, [68Ga]Ga-SB03178 demonstrated higher tumor uptake and superior tumor-to-background contrast ratios than [68Ga]Ga-SB04033. 177Lu-labeled SB03178 was subjected to tumor retention studies, mouse dosimetry profiling and mouse-to-human dose extrapolations also using the HEK293T:hFAP tumor model. [177Lu]Lu-SB03178 exhibited a combination of high and sustained tumor uptake, with excellent tumor-to-critical organ uptake ratios resulting in a high radiation absorbed dose to the tumor and a low estimated whole-body dose to humans. Our preliminary findings are considerably encouraging to support clinical development of [68Ga]Ga-/[177Lu]Lu-SB03178 theranostic pair for use in a vast majority of FAP-overexpressing neoplasms, particularly carcinomas.

Combining Cell-Intrinsic and -Extrinsic Resistance to HIV-1 By Engineering Hematopoietic Stem Cells for CCR5 Knockout and B Cell Secretion of Therapeutic Antibodies

Autologous transplantation of CCR5 null hematopoietic stem and progenitor cells (HSPCs) is the only known cure for HIV-1 infection. However, this treatment is limited because of the rarity of CCR5 -null matched donors, the morbidities associated with allogeneic transplantation, and the prevalence of HIV-1 strains resistant to CCR5 knockout (KO) alone. Here, we propose a one-time therapy through autologous transplantation of HSPCs genetically engineered ex vivo to produce both CCR5 KO cells and long-term secretion of potent HIV-1 inhibiting antibodies from B cell progeny. CRISPR-Cas9-engineered HSPCs maintain engraftment capacity and multi-lineage potential in vivo and can be engineered to express multiple antibodies simultaneously. Human B cells engineered to express each antibody secrete neutralizing concentrations capable of inhibiting HIV-1 pseudovirus infection in vitro . This work lays the groundwork for a potential one-time functional cure for HIV-1 through combining the long-term delivery of therapeutic antibodies against HIV-1 and the known efficacy of CCR5 KO HSPC transplantation.

In vitro evolution of diagnostic antibodies targeting native antigens in plasma by sandwich flow cytometry

Monoclonal antibodies (mAbs) that recognize and bind to specific antigens (Ags) have a wide range of applications in research, therapy, and diagnostics. However, many of these antibodies cannot bind well to the native Ags. In this study, based on the Chinese hamster ovary (CHO) cell display platform developed previously in our lab, we reported a novel artificial evolution procedure to improve the affinity of mAb against the native Ag directly using the plasma samples without purification of the native Ag. In this procedure, a pair of antibodies able to bind the Ag in sandwich manner are first confirmed (Ab1/Ab2) and the antibody (Ab) to be affinity-improved (Ab1) is displayed on CHO cells for Ab mutation. Then the cells were detected and sorted with flow cytometry in the form of Ab1-Ag-fluorescence labeled Ab2, which we named sandwich flow cytometry. Here, we used soluble isoform of suppression of tumorigenicity 2 (sST2) protein as model Ag, carried out "sandwich" maturation directly using the plasma samples containing the native sST2 protein and optimized a pair of antibodies with significantly improved sensitivity in the detection of the native sST2 in plasma. This method could be very useful in optimization of the diagnostic Ab pairs working in a "sandwich" manner if more antibodies were also successfully affinity-matured with this method.

Application of sample displacement batch chromatography for fractionation of proteoforms

Fractionation of proteoforms is currently the most challenging topic in the field of proteoform analysis. The need for considering the existence of proteoforms in experimental approaches is not only important in Life Science research in general but especially in the manufacturing of therapeutic proteins (TPs) like recombinant therapeutic antibodies (mAbs). Some of the proteoforms of TPs have significantly decreased actions or even cause side effects. The identification and removal of proteoforms differing from the main species, having the desired action, is challenging because the difference in the composition of atoms is often very small and their concentration in comparison to the main proteoform can be low. In this study, we demonstrate that sample displacement batch chromatography (SDBC) is an easy-to-handle, economical, and efficient method for fractionating proteoforms. As a model sample a commercial ovalbumin fraction was used, containing many ovalbumin proteoforms. The most promising parameters for the SDBC were determined by a screening approach and applied for a 10-segment fractionation of ovalbumin with cation exchange chromatography resins. Mass spectrometry of intact proteoforms was used for characterizing the SDBC fractionation process. By SDBC, a significant separation of different proteoforms was obtained.

Unveiling the multifaceted landscape of N-glycosylation in antibody variable domains: Insights and implications

N-glycosylation at the antibody variable domain has emerged as an important modification influencing antibody function. Despite its significance, information regarding its role and regulation remains limited. To address this gap, we comprehensively explored antibody structures housing N-glycosylation within the Protein Data Bank, yielding fresh insights into this intricate landscape. Our findings revealed that among 208 structures, N-glycosylation was more prevalent in human and mouse antibodies containing IGHV1-8 and IGHV2-2 germline genes, respectively. Moreover, our research highlights the potential for somatic hypermutation to introduce N-glycosylation sites by substituting polar residues (Ser or Thr) in germline variable genes with asparagine. Notably, our study underscores the prevalence of N-glycosylation in antiviral antibodies, especially anti-HIV. Besides antigen-antibody interaction, our findings suggest that N-glycosylation may impact antibody specificity, affinity, and avidity by influencing Fab dimer formation and complementary-determining region orientation. We also identified different glycan structures in HIV and SARS-CoV-2 antibody proteomic datasets, highlighting disparities from the N-glycan structures between PDB antibodies and biological repertoires further highlighting the complexity of N-glycosylation patterns. Our findings significantly enrich our understanding of the N-glycosylation's multifaceted characteristics within the antibody variable domain. Additionally, they underscore the pressing imperative for a more comprehensive characterization of its impact on antibody function.

A survey of FDA Approved Monoclonal Antibodies and Fc-fusion Proteins for Manufacturing Changes and Comparability Assessment

OBJECTIVE

Manufacturing changes occur commonly throughout stages of biologics development and may result in product quality attribute changes. As changes in critical quality attributes have the potential to affect clinical safety and efficacy of products, it is imperative to ensure the quality and clinical performance before introducing the after-change products. Thus, we embarked on this project to understand what data have supported the manufacturing changes for licensed products with pre- and post-approval changes.

METHODS

We surveyed the manufacturing changes of 85 monoclonal antibodies and 10 Fc fusion proteins approved by the Food and Drug Administration as of December 25, 2021. After collecting the type and timing of changes for these products, we investigated the approaches that provided supporting data for the changes. The source documents included reports submitted by applicants and FDA's regulatory reviews.

RESULTS

Analytical comparability was assessed to support all identified manufacturing changes. Supporting clinical data were available in 92% of these manufacturing changes; including data from pharmacokinetic comparability studies alone (3%), other studies on efficacy or safety (70%) and a combination of both (19%). Clinical pharmacokinetic comparability data contributed to supporting substantial changes, such as host cell type or master cell bank changes, concentration or formulation changes, and changes from pre-filled syringes to autoinjectors, especially when introduced after completing pivotal studies.

CONCLUSION

Our comprehensive retrospective analysis provides an understanding of the regulatory experience and industry practice, which could facilitate developing appropriate comparability approaches to support manufacturing changes in the future.

Cell-based production of Fc-GlcNAc and Fc-alpha-2,6 sialyl glycan enriched antibody with improved effector functions through glycosylation pathway engineering

Glycosylation of antibody plays an important role in Fc-mediated killing of tumor cells and virus-infected cells through effector functions such as antibody-dependent cellular cytotoxicity (ADCC), antibody dependent cell-mediated phagocytosis (ADCP) and vaccinal effect. Previous studies showed that therapeutical humanized antibodies with α2-6 sialyl complex type (SCT) glycan attached to Fc-Asn297 exhibited optimal binding to the Fc receptors on effector cells associated with ADCC, ADCP and vaccinal effect. However, the production of antibodies with homogeneous Fc-SCT needs multiple in vitro enzymatic and purification steps. In this study, we report two different approaches to shorten the processes to produce SCT-enriched antibodies. First, we expressed a bacterial endoglycosidase in GNT1-KO EXPI293 cells to trim all N -glycans to mono-GlcNAc glycoforms for in vitro transglycosylation to generate homogeneous SCT antibody. Second, we engineered the glycosylation pathway of HEK293 cells through knockout of the undesired glycosyltransferases and expression of the desired glycosyltransferases to produce SCT enriched antibodies with similar binding affinity to Fc receptors and ADCC activity to homogenous SCT antibody.

A platform for qualitative and quantitative characterization of α-Gal and NeuGc at the oligosaccharide level

Glycosylation modification serves as a pivotal quality attribute in glycoprotein-based therapeutics, emphasizing its role in drug safety and efficacy. Prior studies have underscored the potential immunogenic risks posed by the presence of galactose-α-1,3-galactose (α-Gal) and N-glycolylneuraminic acid (NeuGc) in glycoprotein formulations. This accentuates the imperative for developing robust qualitative and quantitative analytical methods to monitor these immunogenic epitopes, thereby ensuring drug safety. In the present investigation, α-Gal and NeuGc were accurately quantified using UPLC-FLR-MS/MS at the oligosaccharide level. Remarkably, α-Gal could be identified when the ion intensity ratio or the mass-to-charge ratio (m/z) of 528.19 to 366.14 exceeded 1. Concurrently, NeuGc and N-acetylneuraminic acid (NeuAc) could be unambiguously identified through their respective fragment ions at m/z 673.23 and m/z 657.23. Furthermore, relative quantification of α-Gal and NeuGc was achieved using fluorescence signals. This study introduces a sensitive and reliable analytical approach for the qualitative and quantitative assessment of α-Gal and NeuGc in glycoprotein pharmaceuticals. The methodology offers significant potential for application in process control and optimization of glycoprotein production, aimed at minimizing immunogenicity and enhancing product quality.

Glycosylation shapes the efficacy and safety of diverse protein, gene and cell therapies

Over recent decades, therapeutic proteins have had widespread success in treating a myriad of diseases. Glycosylation, a near universal feature of this class of drugs, is a critical quality attribute that significantly influences the physical properties, safety profile and biological activity of therapeutic proteins. Optimizing protein glycosylation, therefore, offers an important avenue to developing more efficacious therapies. In this review, we discuss specific examples of how variations in glycan structure and glycoengineering impacts the stability, safety, and clinical efficacy of protein-based drugs that are already in the market as well as those that are still in preclinical development. We also highlight the impact of glycosylation on next generation biologics such as T cell-based cancer therapy and gene therapy.

Pharmacokinetic Profiles of a Proposed Biosimilar Ustekinumab (BFI-751): Results From a Randomized Phase 1 Trial

BioFactura has developed a proposed biosimilar candidate (BFI-751) to ustekinumab reference product. Results are reported for the first-in-human trial designed to compare the pharmacokinetic profiles, safety, and immunogenicity of BFI-751 and ustekinumab reference products from the European Union and United States as well as similarity of the EU and US reference products. This was a multicenter, randomized, double blind, 3-parallel-group study (trial ID: NCT04843631). Healthy subjects were randomized to receive a single subcutaneous dose of 45 mg of BFI-751, EU ustekinumab, or US ustekinumab. The pharmacokinetic parameters were area under the concentration-time curve (AUC) from time zero to infinity, AUC from time zero to the last quantifiable concentration, and maximum concentration. Safety, tolerability, and immunogenicity data were also reported. Pairwise comparisons among the 3 treatments all met the standard bioequivalence criteria that the 90% confidence interval of the geometric mean ratios of AUC from time zero to infinity, AUC from time zero to the last quantifiable concentration, and maximum concentration are completely within the acceptance interval of 80%-125%. There were no marked differences in the safety and tolerability profiles for subjects receiving BFI-751 as compared to EU or US ustekinumab. Treatment-emergent adverse events were mild to moderate for all treatment groups.

Simplifying glycan monitoring of complex antigens such as the SARS-CoV-2 spike to accelerate vaccine development

Glycosylation is a key quality attribute that must be closely monitored for protein therapeutics. Established assays such as HILIC-Fld of released glycans and LC-MS of glycopeptides work well for glycoproteins with a few glycosylation sites but are less amenable for those with multiple glycosylation sites, resulting in complex datasets that are time consuming to generate and difficult to analyze. As part of efforts to improve preparedness for future pandemics, researchers are currently assessing where time can be saved in the vaccine development and production process. In this context, we evaluated if neutral and acidic monosaccharides analysis via HPAEC-PAD could be used as a rapid and robust alternative to LC-MS and HILIC-Fld for monitoring glycosylation between protein production batches. Using glycoengineered spike proteins we show that the HPAEC-PAD monosaccharide assays could quickly and reproducibly detect both major and minor glycosylation differences between batches. Moreover, the monosaccharide results aligned well with those obtained by HILIC-Fld and LC-MS.

Impact of Decalcification, Cold Ischemia, and Deglycosylation on Performance of Programmed Cell Death Ligand-1 Antibodies With Different Binding Epitopes: Comparison of 7 Clones

Programmed cell death ligand-1 (PD-L1) expression levels in patients' tumors have demonstrated clinical utility across many cancer types and are used to determine treatment eligibility. Several independently developed PD-L1 immunohistochemical (IHC) predictive assays are commercially available and have demonstrated different levels of staining between assays, generating interest in understanding the similarities and differences between assays. Previously, we identified epitopes in the internal and external domains of PD-L1, bound by antibodies in routine clinical use (SP263, SP142, 22C3, and 28-8). Variance in performance of assays utilizing these antibodies, observed following exposure to preanalytical factors such as decalcification, cold ischemia, and duration of fixation, encouraged additional investigation of antibody-binding sites, to understand whether binding site structures/conformations contribute to differential PD-L1 IHC assay staining. We proceeded to further investigate the epitopes on PD-L1 bound by these antibodies, alongside the major clones utilized in laboratory-developed tests (E1L3N, QR1, and 73-10). Characterization of QR1 and 73-10 clones demonstrated that both bind the PD-L1 C-terminal internal domain, similar to SP263/SP142. Our results also demonstrate that under suboptimal decalcification or fixation conditions, the performance of internal domain antibodies is less detrimentally affected than that of external domain antibodies 22C3/28-8. Furthermore, we show that the binding sites of external domain antibodies are susceptible to deglycosylation and conformational structural changes, which directly result in IHC staining reduction or loss. The binding sites of internal domain antibodies were unaffected by deglycosylation or conformational structural change. This study demonstrates that the location and conformation of binding sites, recognized by antibodies employed in PD-L1 diagnostic assays, differ significantly and exhibit differing degrees of robustness. These findings should reinforce the need for vigilance when performing clinical testing with different PD-L1 IHC assays, particularly in the control of cold ischemia and the selection of fixation and decalcification conditions.

An Advax-CpG55.2 adjuvanted recombinant hemagglutinin vaccine provides immunity against H7N9 influenza in adult and neonatal mice

There is a major unmet need for strategies to improve the immunogenicity and effectiveness of pandemic influenza vaccines, particularly in poor responder populations such as neonates. Recombinant protein approaches to pandemic influenza offer advantages over more traditional inactivated virus approaches, as they are free of problems such as egg adaptation or need for high level biosecurity containment for manufacture. However, a weakness of recombinant proteins is their low immunogenicity. We asked whether the use of an inulin polysaccharide adjuvant (Advax) alone or combined with a TLR9 agonist (CpG55.2) would enhance the immunogenicity and protection of a recombinant hemagglutinin vaccine against H7N9 influenza (rH7HA), including in neonatal mice. Advax adjuvant induced predominantly IgG1 responses against H7HA, whereas Advax-CpG55.2 adjuvant also induced IgG2a, IgG2b and IgG3 responses, consistent with the TLR9 agonist component inducing a Th1 bias. Advax-CpG55.2 adjuvanted rH7HA induced high serum neutralizing antibody titers in adult mice. In newborns it similarly overcame immune hypo-responsiveness and enhanced serum anti-rH7HA IgG levels in 7-day-old BALB/C and C57BL/6 mice. Immunized adult mice were protected against a lethal H7N9 virus challenge. When formulated with Advax-CpG55.2 adjuvant, greater protection was seen with rH7HA than with inactivated H7 whole virus antigen. Advax-CpG55.2 adjuvanted rH7HA represents a promising influenza vaccine platform for further development.

Long-Term Culturing of FreeStyle 293-F Cells Affects Immunoglobulin G Glycome Composition

Glycosylation of IgG regulates the effector function of this antibody in the immune response. Glycosylated IgG is a potent therapeutic used for both research and clinical purposes. While there is ample research on how different cell culture conditions affect IgG glycosylation, the data are missing on the stability of IgG glycome during long cell passaging, i.e., cell "aging". To test this, we performed three independent time course experiments in FreeStyle 293-F cells, which secrete IgG with a human-like glycosylation pattern and are frequently used to generate defined IgG glycoforms. During long-term cell culturing, IgG glycome stayed fairly stable except for galactosylation, which appeared extremely variable. Cell transcriptome analysis revealed no correlation in galactosyltransferase B4GALT1 expression with galactosylation change, but with expression of EEF1A1 and SLC38A10, genes previously associated with IgG galactosylation through GWAS. The FreeStyle 293-F cell-based system for IgG production is a good model for studies of mechanisms underlying IgG glycosylation, but results from the present study point to the utmost importance of the need to control IgG galactosylation in both in vitro and in vivo systems. This is especially important for improving the production of precisely glycosylated IgG for therapeutic purposes, since IgG galactosylation affects the inflammatory potential of IgG.

Head-to-head comparison of different classes of FAP radioligands designed to increase tumor residence time: monomer, dimer, albumin binders, and small molecules vs peptides

PURPOSE

Fibroblast activation protein-α (FAP)-targeting radioligands have recently demonstrated high diagnostic potential. However, their therapeutic value is impaired by the short tumor residence time. Several strategies have been tested to overcome this limitation, but a head-to-head comparison has never been done. With the aim to identify strengths and limitations of the suggested strategies, we compared the monomer FAPI-46 versus (a) its dimer (FAPI-46-F1D), (b) two albumin binders conjugates (FAPI-46-Ibu (ibuprofen) and FAPI-46-EB (Evans Blue)), and (c) cyclic peptide FAP-2286.

METHODS

177Lu-labeled ligands were evaluated in vitro in cell lines with low (HT-1080.hFAP) and high (HEK-293.hFAP) humanFAP expression. SPECT/CT imaging and biodistribution studies were conducted in HT-1080.hFAP and HEK-293.hFAP xenografts. The areas under the curve (AUC) of the tumor uptake and tumor-to-critical-organs ratios and the absorbed doses were estimated.

RESULTS

Radioligands showed IC50 in the picomolar range. Striking differences were observed in vivo regarding tumor uptake, residence, specificity, and total body distribution. All [177Lu]Lu-FAPI-46-based radioligands showed similar uptake between the two tumor models. [177Lu]Lu-FAP-2286 showed higher uptake in HEK-293.hFAP and the least background. The AUC of the tumor uptake and absorbed dose was higher for [177Lu]Lu-FAPI-46-F1D and the two albumin binder conjugates, [177Lu]Lu-FAPI-46-Ibu and [177Lu]Lu-FAPI-46-EB, in HT1080.hFAP xenografts and for [177Lu]Lu-FAPI-46-EB and [177Lu]Lu-FAP-2286 in HEK293.hFAP xenografts. The tumor-to-critical-organs AUC values and the absorbed doses were in favor of [177Lu]Lu-FAP-2286, but tumor-to-kidneys.

CONCLUSION

The study indicated dimerization and cyclic peptide structures as promising strategies for prolonging tumor residence time, sparing healthy tissues. Albumin binding strategy outcome depended on the albumin binding moiety. The peptide showed advantages in terms of tumor-to-background ratios, besides tumor-to-kidneys, but its tumor uptake was FAP expression-dependent.

Irisin acts through its integrin receptor in a two-step process involving extracellular Hsp90α

Exercise benefits the human body in many ways. Irisin is secreted by muscle, increased with exercise, and conveys physiological benefits, including improved cognition and resistance to neurodegeneration. Irisin acts via αV integrins; however, a mechanistic understanding of how small polypeptides like irisin can signal through integrins is poorly understood. Using mass spectrometry and cryo-EM, we demonstrate that the extracellular heat shock protein 90α (eHsp90α) is secreted by muscle with exercise and activates integrin αVβ5. This allows for high-affinity irisin binding and signaling through an Hsp90α/αV/β5 complex. By including hydrogen/deuterium exchange data, we generate and experimentally validate a 2.98 Å RMSD irisin/αVβ5 complex docking model. Irisin binds very tightly to an alternative interface on αVβ5 distinct from that used by known ligands. These data elucidate a non-canonical mechanism by which a small polypeptide hormone like irisin can function through an integrin receptor.

Production of monoclonal antibodies for therapeutic purposes: A review

Monoclonal antibodies (mAbs) have been used in the development of immunotherapies that target a variety of diseases, such as cancer, autoimmune diseases, and even viral infections; they play a key role in immunization and are expected after vaccination. However, some conditions do not promote the development of neutralizing antibodies. Production and use of mAbs, generated in biofactories, represent vast potential as aids in immunological responses when the organism cannot produce them on their own, these convey unique specificity by recognizing and targeting specific antigen. Antibodies can be defined as heterotetrametric glycoproteins of symmetric nature, and they participate as effector proteins in humoral responses. Additionally, there are different types of mAbs (murine, chimeric, humanized, human, mAbs as Antibody-drug conjugates and bispecific mAbs) discussed in the present work. When these molecules are produced in vitro as mAbs, several common techniques, such as hybridomas or phage display are used. There are several preferred cell lines that function as biofactories, for the production of mAbs, the selection of which rely on the variation of adaptability, productivity and both phenotypic and genotypic shifts. After the cell expression systems and culture techniques are used, there are diverse specialized downstream processes to achieve desired yield and isolation as well as product quality and characterization. Novel perspectives regarding these protocols represent a potential improvement for mAbs high-scale production.

Identification, characterization, and engineering of glycosylation in thrombolyticsa

Cardiovascular diseases, such as myocardial infarction, ischemic stroke, and pulmonary embolism, are the most common causes of disability and death worldwide. Blood clot hydrolysis by thrombolytic enzymes and thrombectomy are key clinical interventions. The most widely used thrombolytic enzyme is alteplase, which has been used in clinical practice since 1986. Another clinically used thrombolytic protein is tenecteplase, which has modified epitopes and engineered glycosylation sites, suggesting that carbohydrate modification in thrombolytic enzymes is a viable strategy for their improvement. This comprehensive review summarizes current knowledge on computational and experimental identification of glycosylation sites and glycan identity, together with methods used for their reengineering. Practical examples from previous studies focus on modification of glycosylations in thrombolytics, e.g., alteplase, tenecteplase, reteplase, urokinase, saruplase, and desmoteplase. Collected clinical data on these glycoproteins demonstrate the great potential of this engineering strategy. Outstanding combinatorics originating from multiple glycosylation sites and the vast variety of covalently attached glycan species can be addressed by directed evolution or rational design. Directed evolution pipelines would benefit from more efficient cell-free expression and high-throughput screening assays, while rational design must employ structure prediction by machine learning and in silico characterization by supercomputing. Perspectives on challenges and opportunities for improvement of thrombolytic enzymes by engineering and evolution of protein glycosylation are provided.

Screening of Membrane Protein Production by Comparison of Transient Expression in Insect and Mammalian Cells

Membrane proteins are difficult biomolecules to express and purify. In this paper, we compare the small-scale production of six selected eukaryotic integral membrane proteins in insect and mammalian cell expression systems using different techniques for gene delivery. The target proteins were C terminally fused to the green fluorescent marker protein GFP to enable sensitive monitoring. We show that the choice of expression systems makes a considerable difference to the yield and quality of the six selected membrane proteins. Virus-free transient gene expression (TGE) in insect High Five cells combined with solubilization in dodecylmaltoside plus cholesteryl hemisuccinate generated the most homogeneous samples for all six targets. Further, the affinity purification of the solubilized proteins using the Twin-Strep^® tag improved protein quality in terms of yield and homogeneity compared to His-tag purification. TGE in High Five insect cells offers a fast and economically attractive alternative to the established methods that require either baculovirus construction and the infection of the insect cells or relatively expensive transient gene expression in mammalian cells for the production of integral membrane proteins.

Study on antibody Fc-glycosylation for optimal effector functions

A comprehensive structure-activity relationship study on antibody Fc-glycosylation has been performed using the chimeric anti-SSEA4 antibody chMC813-70 as a model. The α-2,6 sialylated biantennary complex type glycan was identified as the optimal Fc-glycan with significant enhancement in antibody effector functions, including binding to different Fc receptors and ADCC.

Innovative Metrics for Reporting and Comparing the Glycan Structural Profile in Biotherapeutics

Glycosylation is a critical quality attribute in biotherapeutics, impacting properties such as protein stability, solubility, clearance rate, efficacy, immunogenicity, and safety. Due to the heterogenic and complex nature of protein glycosylation, comprehensive characterization is demanding. Moreover, the lack of standardized metrics for evaluating and comparing glycosylation profiles hinders comparability studies and the establishment of manufacturing control strategies. To address both challenges, we propose a standardized approach based on novel metrics for a comprehensive glycosylation fingerprint which greatly facilitates the reporting and objective comparison of glycosylation profiles. The analytical workflow is based on a liquid chromatography-mass spectrometry-based multi-attribute method. Based on the analytical data, a matrix of glycosylation-related quality attributes, both at site-specific and whole molecule level, are computed, which provide metrics for a comprehensive product glycosylation fingerprint. Two case studies illustrate the applicability of the proposed indices as a standardized and versatile approach for reporting all dimensions of the glycosylation profile. The proposed approach further facilitates the assessments of risks associated with changes in the glycosylation profile that may affect efficacy, clearance, and immunogenicity.

Comparison of vector elements and process conditions in transient and stable suspension HEK293 platforms using SARS-CoV-2 receptor binding domain as a model protein

BACKGROUND

Mammalian cell lines are frequently used as protein expression hosts because of their ability to correctly fold and assemble complex proteins, produce them at high titers, and confer post-translational modifications (PTMs) critical to proper function. Increasing demand for proteins with human-like PTMs, particularly viral proteins and vectors, have made human embryonic kidney 293 (HEK293) cells an increasingly popular host. The need to engineer more productive HEK293 platforms and the ongoing nature of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic presented an opportunity to study strategies to improve viral protein expression in transient and stable HEK293 platforms.

RESULTS

Initial process development was done at 24 deep well plate (DWP) -scale to screen transient processes and stable clonal cell lines for recombinant SARS-CoV-2 receptor binding domain (rRBD) titer. Nine DNA vectors that drove rRBD production under different promoters and optionally contained Epstein-Barr virus (EBV) elements to promote episomal expression were screened for transient rRBD production at 37 °C or 32 °C. Use of the cytomegalovirus (CMV) promoter to drive expression at 32 °C led to the highest transient protein titers, but inclusion of episomal expression elements did not augment titer. In parallel, four clonal cell lines with titers higher than that of the selected stable pool were identified in a batch screen. Flask-scale transient transfection and stable fed-batch processes were then established that produced rRBD up to 100 mg/L and 140 mg/L, respectively. While a bio-layer interferometry (BLI) assay was crucial for efficiently screening DWP batch titers, an enzyme-linked immunosorbent assay (ELISA) was used to compare titers from the flask-scale batches due to varying matrix effects from different cell culture media compositions.

CONCLUSION

Comparing yields from the flask-scale batches revealed that stable fed-batch cultures produced up to 2.1x more rRBD than transient processes. The stable cell lines developed in this work are the first reported clonal, HEK293-derived rRBD producers and have titers up to 140 mg/L. As stable production platforms are more economically favorable for long-term protein production at large scales, investigation of strategies to increase the efficiency of high-titer stable cell line generation in Expi293F or other HEK293 hosts is warranted.

Recombinant mucin biotechnology and engineering

Mucins represent a largely untapped class of polymeric building block for biomaterials, therapeutics, and other biotechnology. Because the mucin polymer backbone is genetically encoded, sequence-specific mucins with defined physical and biochemical properties can be fabricated using recombinant technologies. The pendent O-glycans of mucins are increasingly implicated in immunomodulation, suppression of pathogen virulence, and other biochemical activities. Recent advances in engineered cell production systems are enabling the scalable synthesis of recombinant mucins with precisely tuned glycan side chains, offering exciting possibilities to tune the biological functionality of mucin-based products. New metabolic and chemoenzymatic strategies enable further tuning and functionalization of mucin O-glycans, opening new possibilities to expand the chemical diversity and functionality of mucin building blocks. In this review, we discuss these advances, and the opportunities for engineered mucins in biomedical applications ranging from in vitro models to therapeutics.

Protective effects of conditioned media of immortalized stem cells from human exfoliated deciduous teeth on pressure ulcer formation

Pressure ulcers (PUs) are increasing with aging worldwide, but there is no effective causal therapy. Although mesenchymal stem cells (MSCs) promote cutaneous wound healing, the effects of the conditioned medium (CM) of MSCs on cutaneous PU formation induced by ischemia-reperfusion injury have been poorly investigated. To address this issue, herein, we first established an immortalized stem cell line from human exfoliated deciduous teeth (SHED). This cell line was revealed to have superior characteristics in that it grows infinitely and vigorously, and stably and consistently secretes a variety of cytokines. Using the CM obtained from the immortalized SHED cell line, we investigated the therapeutic potential on a cutaneous ischemia-reperfusion mouse model for PU formation using two magnetic plates. This is the first study to show that CM from immortalized SHEDs exerts therapeutic effects on PU formation by promoting angiogenesis and oxidative stress resistance through vascular endothelial growth factor and hepatocyte growth factor. Thus, the CM of MSCs has potent therapeutic effects, whereas these therapies have not been implemented in human medicine. To try to meet the regulatory requirements for manufacturing and quality control as much as possible, it is necessary to produce CM that is consistently safe and effective. The immortalization of stem cells could be one of the breakthroughs to meet the regulatory requirements and consequently open up a novel avenue to create a novel type of cell-free regenerative medicine, although further investigation into the quality control is warranted.

Simplifying the detection and monitoring of protein glycosylation during in vitro glycoengineering

The majority of mammalian proteins are glycosylated, with the glycans serving to modulate a wide range of biological activities. Variations in protein glycosylation can have dramatic effects on protein stability, immunogenicity, antibody effector function, pharmacological safety and potency, as well as serum half-life. The glycosylation of therapeutic biologicals is a critical quality attribute (CQA) that must be carefully monitored to ensure batch-to-batch consistency. Notably, many factors can affect the composition of the glycans during glycoprotein production, and variations in glycosylation are among the leading causes of pharmaceutical batch rejection. Currently, the characterization of protein glycosylation relies heavily on methods that employ chromatography and/or mass spectrometry, which require a high level of expertise, are time-consuming and costly and, because they are challenging to implement during in-process biologics production or during in vitro glycan modification, are generally performed only post-production. Here we report a simplified approach to assist in monitoring glycosylation features during glycoprotein engineering, that employs flow cytometry using fluorescent microspheres chemically coupled to high-specificity glycan binding reagents. In our GlycoSense method, a range of carbohydrate-sensing microspheres with distinct optical properties may be combined into a multiplex suspension array capable of detecting multiple orthogonal glycosylation features simultaneously, using commonplace instrumentation, without the need for glycan release. The GlycoSense method is not intended to replace more detailed post-production glycan profiling, but instead, to complement them by potentially providing a cost-effective, rapid, yet robust method for use at-line as a process analytic technology (PAT) in a biopharmaceutical workflow or at the research bench. The growing interest in using in vitro glycoengineering to generate glycoproteins with well-defined glycosylation, provides motivation to demonstrate the capabilities of the GlycoSense method, which we apply here to monitor changes in the protein glycosylation pattern (GlycoPrint) during the in vitro enzymatic modification of the glycans in model glycoproteins.

Identification of Cell Culture Factors Influencing Afucosylation Levels in Monoclonal Antibodies by Partial Least-Squares Regression and Variable Importance Metrics

Retrospective analysis of historic data for cell culture processes is a powerful tool to develop further process understanding. In particular, deploying retrospective analyses can identify important cell culture process parameters for controlling critical quality attributes, e.g., afucosylation, for the production of monoclonal antibodies (mAbs). However, a challenge of analyzing large cell culture data is the high correlation between regressors (particularly media composition), which makes traditional analyses, such as analysis of variance and multivariate linear regression, inappropriate. Instead, partial least-squares regression (PLSR) models, in combination with machine learning techniques such as variable importance metrics, are an orthogonal or alternative approach to identifying important regressors and overcoming the challenge of a highly covariant data structure. A specific workflow for the retrospective analysis of cell culture data is proposed that covers data curation, PLS regression, model analysis, and further steps. In this study, the proposed workflow was applied to data from four mAb products in an industrial cell culture process to identify significant process parameters that influence the afucosylation levels. The PLSR workflow successfully identified several significant parameters, such as temperature and media composition, to enhance process understanding of the relationship between cell culture processes and afucosylation levels.

Engineering protein glycosylation in CHO cells to be highly similar to murine host cells

Since 2015 more than 34 biosimilars have been approved by the FDA. This new era of biosimilar competition has stimulated renewed technology development focused on therapeutic protein or biologic manufacturing. One challenge in biosimilar development is the genetic differences in the host cell lines used to manufacture the biologics. For example, many biologics approved between 1994 and 2011 were expressed in murine NS0 and SP2/0 cell lines. Chinese Hamster ovary (CHO) cells, however, have since become the preferred hosts for production due to their increased productivity, ease of use, and stability. Differences between murine and hamster glycosylation have been identified in biologics produced using murine and CHO cells. In the case of monoclonal antibodies (mAbs), glycan structure can significantly affect critical antibody effector function, binding activity, stability, efficacy, and in vivo half-life. In an attempt to leverage the intrinsic advantages of the CHO expression system and match the reference biologic murine glycosylation, we engineered a CHO cell expressing an antibody that was originally produced in a murine cell line to produce murine-like glycans. Specifically, we overexpressed cytidine monophospho-N-acetylneuraminic acid hydroxylase (CMAH) and N-acetyllactosaminide alpha-1,3-galactosyltransferase (GGTA) to obtain glycans with N-glycolylneuraminic acid (Neu5Gc) and galactose-α-1,3-galactose (alpha gal). The resulting CHO cells were shown to produce mAbs with murine glycans, and they were then analyzed by the spectrum of analytical methods typically used to demonstrate analytical similarity as a part of demonstrating biosimilarity. This included high-resolution mass spectrometry, biochemical, as well as cell-based assays. Through selection and optimization in fed-batch cultures, two CHO cell clones were identified with similar growth and productivity criteria to the original cell line. They maintained stable production for 65 population doubling times while matching the glycosylation profile and function of the reference product expressed in murine cells. This study demonstrates the feasibility of engineering CHO cells to express mAbs with murine glycans to facilitate the development of biosimilars that are highly similar to marketed reference products expressed in murine cells. Furthermore, this technology can potentially reduce the residual uncertainty regarding biosimilarity, resulting in a higher probability of regulatory approval and potentially reduced costs and time in development.

Impact of N-Linked Glycosylation on Therapeutic Proteins

Therapeutic proteins have unique advantages over small-molecule drugs in the treatment of various diseases, such as higher target specificity, stronger pharmacological efficacy and relatively low side effects. These advantages make them increasingly valued in drug development and clinical practice. However, although highly valued, the intrinsic limitations in their physical, chemical and pharmacological properties often restrict their wider applications. As one of the most important post-translational modifications, glycosylation has been shown to exert positive effects on many properties of proteins, including molecular stability, and pharmacodynamic and pharmacokinetic characteristics. Glycoengineering, which involves changing the glycosylation patterns of proteins, is therefore expected to be an effective means of overcoming the problems of therapeutic proteins. In this review, we summarize recent efforts and advances in the glycoengineering of erythropoietin and IgG monoclonal antibodies, with the goals of illustrating the importance of this strategy in improving the performance of therapeutic proteins and providing a brief overview of how glycoengineering is applied to protein-based drugs.

1Progress, applications, challenges and prospects of protein purification technology

Protein is one of the most important biological macromolecules in life, which plays a vital role in cell growth, development, movement, heredity, reproduction and other life activities. High quality isolation and purification is an essential step in the study of the structure and function of target proteins. Therefore, the development of protein purification technologies has great theoretical and practical significance in exploring the laws of life activities and guiding production practice. Up to now, there is no forthcoming method to extract any proteins from a complex system, and the field of protein purification still faces significant opportunities and challenges. Conventional protein purification generally includes three steps: pretreatment, rough fractionation, and fine fractionation. Each of the steps will significantly affect the purity, yield and the activity of target proteins. The present review focuses on the principle and process of protein purification, recent advances, and the applications of these technologies in the life and health industry as well as their far-reaching impact, so as to promote the research of protein structure and function, drug development and precision medicine, and bring new insights to researchers in related fields.

Challenges and opportunities in gene editing of B cells

B cells have long been an underutilized target in immune cell engineering, despite a number of unique attributes that could address longstanding challenges in medicine. Notably, B cells evolved to secrete large quantities of antibodies for prolonged periods, making them suitable platforms for long-term protein delivery. Recent advances in gene editing technologies, such as CRISPR-Cas, have improved the precision and efficiency of engineering and expanded potential applications of engineered B cells. While most work on B cell editing has focused on ex vivo modification, a body of recent work has also advanced the possibility of in vivo editing applications. In this review, we will discuss both past and current approaches to B cell engineering, and its promising applications in immunology research and therapeutic gene editing.

Generation and functional evaluation of novel monoclonal antibodies targeting glycosylated human stem cell factor

Human stem cell factor (hSCF) is an early-acting growth factor that promotes proliferation, differentiation, migration, and survival in several tissues. It plays a crucial role in hematopoiesis, gametogenesis, melanogenesis, intestinal motility, and in development and recovery of nervous and cardiovascular systems. Potential therapeutic applications comprise anemia treatment, mobilization of hematopoietic stem/progenitor cells to peripheral blood, and increasing gene transduction efficiency for gene therapy. Developing new tools to characterize recombinant hSCF in most native-like form as possible is crucial to understand the complexity of its in vivo functions and for improving its biotechnological applications. The soluble domain of hSCF was expressed in HEK293 cells. Highly purified rhSCF showed great molecular mass variability due to the presence of N- and O-linked carbohydrates, and it presented a 2.5-fold increase on proliferative activity compared to bacteria-derived hSCF. Three hybridoma clones producing monoclonal antibodies (mAbs) with high specificity for the glycoprotein were obtained. 1C4 and 2D3 mAbs were able to detect bacteria-derived and glycosylated rhSCF and demonstrated to be excellent candidates to develop a sandwich ELISA assay for rhSCF quantification, with detection limits of 0.18 and 0.07 ng/ml, respectively. Interestingly, 1A10 mAb only recognized glycosylated rhSCF, suggesting that sugar moieties might be involved in epitope recognition. 1A10 mAb showed the highest binding affinity, and it constituted the best candidate for immunodetection of the entire set rhSCF glycoforms in western blot assays, and for intracellular cytokine staining. Our work shows that combining glycosylated rhSCF expression with hybridoma technology is a powerful strategy to obtain specific suitable immunochemical assays and thus improve glycoprotein-producing bioprocesses. KEY POINTS: • Soluble glycosylated human SCF exerted improved proliferative activity on UT-7 cells. • Three mAbs with high specificity targeting glycosylated human SCF were obtained. • mAbs applications comprise sandwich ELISA, western blot, and immunofluorescence assays.

Progress toward rapid, at-line N-glycosylation detection and control for recombinant protein expression

Proteins continue to represent a large fraction of the therapeutics market, reaching over a hundred billion dollars in market size globally. One key feature of protein modification that can affect both structure and function is the addition of glycosylation following protein folding, leading to regulatory requirements for the accurate assessment of protein attributes, including glycan structures. The non-template-driven, innately heterogeneous N-glycosylation process thus requires accurate detection to robustly generate protein therapies. A challenge exists in the timely detection of protein glycosylation without labor-intensive manipulation. In this article, we discuss progress toward N-glycoprotein control, focusing on novel control strategies and the advancement of rapid, high-throughput analysis methods.

Disrupting N-Glycosylation Using Type I Mannosidase Inhibitors Alters B-Cell Receptor Signaling

Kifunensine is a known inhibitor of type I α-mannosidase enzymes and has been shown to have therapeutic potential for a variety of diseases and application in the expression of high-mannose N-glycan bearing glycoproteins; however, the compound's hydrophilic nature limits its efficacy. We previously synthesized two hydrophobic acylated derivatives of kifunensine, namely, JDW-II-004 and JDW-II-010, and found that these compounds were over 75-fold more potent than kifunensine. Here we explored the effects of these compounds on different mice and human B cells, and we demonstrate that they affected the cells in a similar fashion to kifunensine, further demonstrating their functional equivalence to kifunensine in assays utilizing primary cells. Specifically, a dose-dependent increase in the formation of high-mannose N-glycans decorated glycoproteins were observed upon treatment with kifunensine, JDW-II-004, and JDW-II-010, but greater potency was observed with the acylated derivatives. Treatment with kifunensine or the acylated derivatives also resulted in impaired B-cell receptor (BCR) signaling of the primary mouse B cells; however, primary human B cells treated with kifunensine or JDW-II-004 did not affect BCR signaling, while a modest increase in BCR signaling was observed upon treatment with JDW-010. Nevertheless, these findings demonstrate that the hydrophobic acylated derivatives of kifunensine can help overcome the mass-transfer limitations of the parent compound, and they may have applications for the treatment of ERAD-related diseases or prove to be more cost-effective alternatives for the generation and production of high-mannose N-glycan bearing glycoproteins.

Highly sensitive characterization of non-human glycan structures of monoclonal antibody drugs utilizing tandem mass spectrometry

Glycosylation is an important attribute of monoclonal antibodies (mAbs) for assessing manufacturing quality. Analysis of non-human glycans containing terminal galactose-α1,3-galactose and N-glycolylneuraminic acid is essential due to the potential immunogenicity and insufficient efficacy caused by mAb expression in non-human mammalian cells. Using parallel sequencing of isobaric glycopeptides and isomeric glycans that were separated by reversed-phase and porous graphitic carbon LC, we report a highly sensitive LC MS/MS method for the comprehensive characterization of low-abundance non-human glycans and their closely related structural isomers. We demonstrate that the straightforward use of high-abundance diagnostic ions and complementary fragments under the positive ionization low-energy collision-induced dissociation is a universal approach to rapidly discriminate branch-linkage structures of biantennary glycans. Our findings reveal the structural diversity of non-human glycans and sulfation of α-galactosylated glycans, providing both an analytical method and candidate structures that could potentially be used in the crucial quality control of therapeutic mAb products.

Advanced strategies in glycosylation prediction and control during biopharmaceutical development: Avenues toward Industry 4.0

Glycosylation has been shown to define the safety and efficacy of biopharmaceuticals, thus classified as a critical quality attribute. However, controlling glycan heterogeneity has always been a major challenge owing to the multi-variate factors that govern the glycosylation process. Conventional approaches for controlling glycosylation such as gene editing and metabolic control have succeeded in obtaining desired glycan profiles in accordance with the Quality by Design paradigm. Nonetheless, the development of smart algorithms and omics-enabled complete cell characterization have made it possible to predict glycan profiles beforehand, and manipulate process variables accordingly. This review thus discusses the various approaches available for control and prediction of glycosylation in biopharmaceuticals. Further, the futuristic goal of integrating such technologies is discussed in order to attain an automated and digitized continuous bioprocess for control of glycosylation. Given, control of a process as complex as glycosylation requires intense monitoring intervention, we examine the current technologies that enable automation. Finally, we discuss the challenges and the technological gap that currently limits incorporation of an automated process in routine bio-manufacturing, with a glimpse into the economic bearing. This article is protected by copyright. All rights reserved.

Enhanced metabolism and negative regulation of ER stress support higher erythropoietin production in HEK293 cells

Recombinant protein production can cause severe stress on cellular metabolism, resulting in limited titer and product quality. To investigate cellular and metabolic characteristics associated with these limitations, we compare HEK293 clones producing either erythropoietin (EPO) (secretory) or GFP (non-secretory) protein at different rates. Transcriptomic and functional analyses indicate significantly higher metabolism and oxidative phosphorylation in EPO producers compared with parental and GFP cells. In addition, ribosomal genes exhibit specific expression patterns depending on the recombinant protein and the production rate. In a clone displaying a dramatically increased EPO secretion, we detect higher gene expression related to negative regulation of endoplasmic reticulum (ER) stress, including upregulation of ATF6B, which aids EPO production in a subset of clones by overexpression or small interfering RNA (siRNA) knockdown. Our results offer potential target pathways and genes for further development of the secretory power in mammalian cell factories.

Post-translational modifications and glycoprofiling of palivizumab by UHPLC–RPLC/HILIC and mass spectrometry

Viral infections are progressively becoming a global health burden, as witnessed in the ongoing COVID-19 pandemic. Respiratory Syncytial Virus (RSV) is another highly contagious negative-sense RNA virus that causes lower respiratory tract infections and high mortality in infants. Palivizumab (Synagis^®) is the only humanized monoclonal antibody (mAb) approved by the FDA against RSV. The virus neutralization efficacy often depends on the nature and abundance of the glycoforms in therapeutic mAbs. Therefore, a thorough estimation of their PTM profile, especially glycosylation, is relevant. Here, we describe the intact and released glycan analysis of palivizumab (Synagis^®) using HILIC chromatography and mass spectrometry. We detected five glycoforms (Man5/G0FB, G0F/G1F, G1F/G1F, G0FB/G0FB, and G2F/G2F) in deconvoluted MS spectra of intact glycosylated palivizumab. The mapping of the peptide and glycopeptides using LC–ESI–MS led to the detection of associated PTMs and the direct identification of a glycopeptide, GlcNAc₃Man₂. EEQYNSTYR, derived from the heavy chain of palivizumab.Release glycan analysis using UHPLC–HILIC revealed a typical glycan profile consisting of major glycans, G0F (33.94%), G1F (35.50%), G2F (17.24%) also reported previously and minor G1F’ (5.81%), Man5 (3.96%) and G0FB (2.26%) forms with the superior resolution of isomeric G1F/G1F’. Next, we provide the first experimental evidence of Neu5Gc in the commercial palivizumab formulation using DMB labelling. The estimated monosaccharide composition was consistent with previous studies. The findings of the study highlight the efficiency of the release glycan method in providing a correct measure of the total palivizumab glycan pool compared to the intact glycoprotein/glycopeptide approach. The UHPLC–RPLC/HILIC and MS combinations provide a more comprehensive glycoprofile assessment due to the parallel use of fluorescent labels for the analysis of the release of N-glycan, sialic acid, and monosaccharide composition. This approach is suitable for quick quality testing and market surveillance of therapeutic mAbs. Alongside a well-perceived need for cost-effective immunoprophylaxis and the ongoing fast-paced development of next-generation variants of palivizumab, such as MEDI8897, the study reiterates glycosylation as a critical parameter that needs monitoring for drug characterization and quality control.

Design and production strategies for developing a recombinant butyrylcholinesterase medical countermeasure for Organophosphorus poisoning

Organophosphorus nerve agents represent a serious chemical threat due to their ease of production and scale of impact. The recent use of the nerve agent Novichok has re-emphasised the need for broad-spectrum medical countermeasures (MCMs) to these agents. However, current MCMs are limited. Plasma derived human butyrylcholinesterase (huBChE) is a promising novel bioscavenger MCM strategy, but is prohibitively expensive to isolate from human plasma at scale. Efforts to produce recombinant huBChE (rBChE) in various protein expression platforms have failed to achieve key critical attributes of huBChE such as circulatory half-life. These proteins often lack critical features such as tetrameric structure and requisite post-translational modifications. This review evaluates previous attempts to generate rBChE and assesses recent advances in mammalian cell expression and protein engineering strategies that could be deployed to achieve the required half-life and yield for a viable rBChE MCM. This includes the addition of a proline-rich attachment domain, fusion proteins, post translational modifications, expression system selection and optimised downstream processes. Whilst challenges remain, a combinatorial approach of these strategies demonstrates potential as a technically feasible approach to achieving a bioactive and cost effective bioscavenger MCM.

The role of the cell surface glycocalyx in drug delivery to and through the endothelium

Cell membranes are key interfaces where materials engineering meets biology. Traditionally regarded as just the location of receptors regulating the uptake of molecules, we now know that all mammalian cell membranes are 'sugar coated'. These sugars, or glycans, form a matrix bound at the cell membrane via proteins and lipids, referred to as the glycocalyx, which modulate access to cell membrane receptors crucial for interactions with drug delivery systems (DDS). Focusing on the key blood-tissue barrier faced by most DDS to enable transport from the place of administration to target sites via the circulation, we critically assess the design of carriers for interactions at the endothelial cell surface. We also discuss the current challenges for this area and provide opportunities for future research efforts to more fully engineer DDS for controlled, efficient, and targeted interactions with the endothelium for therapeutic application.

Sialylation-dependent pharmacokinetics and differential complement pathway inhibition are hallmarks of CR1 activity in vivo

Human Complement Receptor 1 (HuCR1) is a potent membrane-bound regulator of complement both in vitro and in vivo, acting via interaction with its ligands C3b and C4b. Soluble versions of HuCR1 have been described such as TP10, the recombinant full-length extracellular domain, and more recently CSL040, a truncated version lacking the C-terminal long homologous repeat domain D (LHR-D). However, the role of N-linked glycosylation in determining its pharmacokinetic (PK) and pharmacodynamic (PD) properties is only partly understood. We demonstrated a relationship between the asialo-N-glycan levels of CSL040 and its PK/PD properties in rats and non-human primates (NHPs), using recombinant CSL040 preparations with varying asialo-N-glycan levels. The clearance mechanism likely involves the asialoglycoprotein receptor (ASGR), as clearance of CSL040 with a high proportion of asialo-N-glycans was attenuated in vivo by co-administration of rats with asialofetuin, which saturates the ASGR. Biodistribution studies also showed CSL040 localisation to the liver following systemic administration. Our studies uncovered differential PD effects by CSL040 on complement pathways, with extended inhibition in both rats and NHPs of the alternative pathway compared to the classical and lectin pathways that were not correlated with its PK profile. Further studies showed that this effect was dose dependent and observed with both CSL040 and the full-length extracellular domain of HuCR1. Taken together, our data suggests that sialylation optimization is an important consideration for developing HuCR1-based therapeutic candidates such as CSL040 with improved PK properties and shows that CSL040 has superior PK/PD responses compared to full-length soluble HuCR1.

Recent advances in the production of recombinant factor IX: bioprocessing and cell engineering

Appropriate treatment of Hemophilia B is vital for patients' quality of life. Historically, the treatment used was the administration of coagulation Factor IX derived from human plasma. Advancements in recombinant technologies allowed Factor IX to be produced recombinantly. Successful recombinant production has triggered a gradual shift from the plasma derived origins of Factor IX, as it provides extended half-life and expanded production capacity. However, the complex post-translational modifications of Factor IX have made recombinant production at scale difficult. Considerable research has therefore been invested into understanding and optimizing the recombinant production of Factor IX. Here, we review the evolution of recombinant Factor IX production, focusing on recent developments in bioprocessing and cell engineering to control its post-translational modifications in its expression from Chinese Hamster Ovary (CHO) cells.

Harnessing secretory pathway differences between HEK293 and CHO to rescue production of difficult to express proteins

Biologics represent the fastest growing group of therapeutics, but many advanced recombinant protein moieties remain difficult to produce. Here, we identify metabolic engineering targets limiting expression of recombinant human proteins through a systems biology analysis of the transcriptomes of CHO and HEK293 during recombinant expression. In an expression comparison of 24 difficult to express proteins, one third of the challenging human proteins displayed improved secretion upon host cell swapping from CHO to HEK293. Guided by a comprehensive transcriptomics comparison between cell lines, especially highlighting differences in secretory pathway utilization, a co-expression screening of 21 secretory pathway components validated ATF4, SRP9, JUN, PDIA3 and HSPA8 as productivity boosters in CHO. Moreover, more heavily glycosylated products benefitted more from the elevated activities of the N- and O-glycosyltransferases found in HEK293. Collectively, our results demonstrate the utilization of HEK293 for expression rescue of human proteins and suggest a methodology for identification of secretory pathway components for metabolic engineering of HEK293 and CHO.