The Impact of Glycosylation on the Pharmacokinetics of a TNFR2:Fc Fusion Protein Expressed in Glycoengineered Pichia Pastoris

Evaluation of NUN-004, a Novel Engineered Ephrin Antagonist, in Healthy Volunteers and Patients with Amyotrophic Lateral Sclerosis: A Phase I/Ib, Open-Label, Escalating Dose and Extended Access Study

BACKGROUND

Erythropoietin-producing hepatocellular carcinoma A4 (EphA4) is implicated in the pathophysiology of amyotrophic lateral sclerosis. EphA4 fusion protein (EphA4-Fc) inhibits EphA4 function in vivo but is too short-lived for prolonged therapy. NUN-004 (mEphA4-Fc) is a modified EphA4-Fc engineered for an extended half-life.

OBJECTIVE

This first-in-human phase I/Ib study evaluated the safety, tolerability, pharmacokinetics, immunogenicity and efficacy of NUN-004 in healthy volunteers and patients with amyotrophic lateral sclerosis.

METHODS

In this open-label study, Part 1 enrolled 20 healthy volunteers in five single ascending dose cohorts (1, 3, 10, 20 and 30 mg/kg), followed by Part 2, which enrolled eight patients with amyotrophic lateral sclerosis in two multiple ascending dose cohorts (cycle 1: 15 and 30 mg/kg) who could continue into an extended access phase (cycles 2-6: 15 mg/kg) for a total of 6 months' treatment. All participants received intravenous NUN-004; multiple dosing was administered weekly in 28-day cycles. Primary endpoints included safety assessments, single-dose and multiple-dose pharmacokinetics, and anti-drug antibodies. Efficacy assessments were Amyotrophic Lateral Sclerosis Function Rating Score Revised (ALSFRS-R) and forced vital capacity.

RESULTS

NUN-004 was well tolerated, with no serious adverse events or discontinuations. NUN-004 exposure generally increased with dose. Single-dose half-life was 111.7 (± 22.8) h in healthy volunteers (n = 20) and 74.4 (± 19.4) h in patients (n = 6). Steady state was observed in patients by day 8. Steady-state half-life (cycle 1 doses 2-4) was 83.7 (± 26.6) to 101.1 (± 46.0) h. No antibody response was observed. ALSFRS-R showed a slight improvement (+0.09 points/month) to cycle 4 and a slight decline (-0.35 points/month) over the whole study. Forced vital capacity trends were consistent with ALSFRS-R.

CONCLUSIONS

This study supports the safety, tolerability and extended half-life of NUN-004, and provides preliminary evidence for its ability to ameliorate disease progression in an amyotrophic lateral sclerosis cohort.

CLINICAL TRIAL REGISTRATION

Registered on ANZCTR under identifier ACTRN12621000514808 (3 May, 2021).

Modulation of the pharmacokinetics of soluble ACE2 decoy receptors through glycosylation

The Spike of SARS-CoV-2 recognizes a transmembrane protease, angiotensin-converting enzyme 2 (ACE2), on host cells to initiate infection. Soluble derivatives of ACE2, in which Spike affinity is enhanced and the protein is fused to Fc of an immunoglobulin, are potent decoy receptors that reduce disease in animal models of COVID-19. Mutations were introduced into an ACE2 decoy receptor, including adding custom N-glycosylation sites and a cavity-filling substitution together with Fc modifications, which increased the decoy's catalytic activity and provided small to moderate enhancements of pharmacokinetics following intravenous and subcutaneous administration in humanized FcRn mice. Most prominently, sialylation of native glycans increases exposures by orders of magnitude, and the optimized decoy is therapeutically efficacious in a mouse COVID-19 model. Ultimately, an engineered and highly sialylated decoy receptor produced using methods suitable for manufacture of representative drug substance has high exposure with a 5- to 9-day half-life. Finally, peptide epitopes at mutated sites in the decoys generally have low binding to common HLA class II alleles and the predicted immunogenicity risk is low. Overall, glycosylation is a critical molecular attribute of ACE2 decoy receptors and modifications that combine tighter blocking of Spike with enhanced pharmacokinetics elevate this class of molecules as viable drug candidates.

Applications of the Methylotrophic Yeast Komagataella phaffii in the Context of Modern Biotechnology

Komagataella phaffii (formerly Pichia pastoris) is a methylotrophic yeast widely used in laboratories around the world to produce recombinant proteins. Given its advantageous features, it has also gained much interest in the context of modern biotechnology. In this review, we present the utilization of K. phaffii as a platform to produce several products of economic interest such as biopharmaceuticals, renewable chemicals, fuels, biomaterials, and food/feed products. Finally, we present synthetic biology approaches currently used for strain engineering, aiming at the production of new bioproducts.

Enhancing pharmacokinetic and pharmacodynamic properties of recombinant therapeutic proteins by manipulation of sialic acid content

The circulatory half-life of recombinant therapeutic proteins is an important pharmacokinetic attribute because it determines the dosing frequency of these drugs, translating directly to treatment cost. Thus, recombinant therapeutic glycoproteins such as monoclonal antibodies have been chemically modified by various means to enhance their circulatory half-life. One approach is to manipulate the N-glycan composition of these agents. Among the many glycan constituents, sialic acid (specifically, N-acetylneuraminic acid) plays a critical role in extending circulatory half-life by masking the terminal galactose that would otherwise be recognised by the hepatic asialoglycoprotein receptor (ASGPR), resulting in clearance of the biotherapeutic from the circulation. This review aims to provide an illustrative overview of various strategies to enhance the pharmacokinetic/pharmacodynamic properties of recombinant therapeutic proteins through manipulation of their sialic acid content.

Glycosylation of immunoglobin G in tumors: Function, regulation and clinical implications

Immunoglobulin G (IgG) is the predominant component in humoral immunity and the major effector of neutralizing heterogeneous antigens. Glycosylation, as excessive posttranscriptional modification, can modulate IgG immune function. Glycosylated IgG has been reported to correlate with tumor progression, presenting several characteristic modifications, including the core fucose, galactose, sialic acid, and the bisect N-acetylglucosamine (GlcNAc). Meanwhile, IgG glycosylation regulates tumor immunity involved in tumor progression and is thus a potential target. Herein, we summarized the research progression to provide novel insight into the application of IgG glycosylation in tumor diagnosis and treatment.

Sequential in vitro enzymatic N-glycoprotein modification reveals site-specific rates of glycoenzyme processing

N-glycosylation is an essential eukaryotic posttranslational modification that affects various glycoprotein properties, including folding, solubility, protein–protein interactions, and half-life. N-glycans are processed in the secretory pathway to form varied ensembles of structures, and diversity at a single site on a glycoprotein is termed ‘microheterogeneity’. To understand the factors that influence glycan microheterogeneity, we hypothesized that local steric and electrostatic factors surrounding each site influence glycan availability for enzymatic modification. We tested this hypothesis via expression of reporter N-linked glycoproteins in N-acetylglucosaminyltransferase MGAT1-null HEK293 cells to produce immature Man₅GlcNAc₂ glycoforms (38 glycan sites total). These glycoproteins were then sequentially modified in vitro from high mannose to hybrid and on to biantennary, core-fucosylated, complex structures by a panel of N-glycosylation enzymes, and each reaction time course was quantified by LC-MS/MS. Substantial differences in rates of in vitro enzymatic modification were observed between glycan sites on the same protein, and differences in modification rates varied depending on the glycoenzyme being evaluated. In comparison, proteolytic digestion of the reporters prior to N-glycan processing eliminated differences in in vitro enzymatic modification. Furthermore, comparison of in vitro rates of enzymatic modification with the glycan structures found on the mature reporters expressed in WT cells correlated well with the enzymatic bottlenecks observed in vivo. These data suggest higher order local structures surrounding each glycosylation site contribute to the efficiency of modification both in vitro and in vivo to establish the spectrum of microheterogeneity in N-linked glycoproteins.

Design of a novel switchable antibody display system in Pichia pastoris

Yeast surface display (YSD) has been shown to represent a powerful tool in the field of antibody discovery and engineering as well as for selection of high producer clones. However, YSD is predominantly applied in Saccharomyces cerevisiae, whereas expression of heterologous proteins is generally favored in the non-canonical yeast Pichia pastoris (Komagataella phaffii). Establishment of surface display in P. pastoris would therefore enable antibody selection and expression in a single host. Here we describe the generation of a Pichia surface display (PSD) system based on antibody expression from episomal plasmids. By screening a diverse set of expression vectors using Design of Experiments (DoE), the effect of different genetic elements on the surface expression of antibody fragments was analyzed. Among the tested genetic elements, we found that the combination of P. pastoris formaldehyde dehydrogenase (FLD1) promoter, S. cerevisiae invertase 2 signal peptide (SUC2), and α-agglutinin cell wall protein (SAG1) including an autonomously replicating sequence of Kluyveromyces lactis (panARS) were contributing most strongly to higher display levels of three tested antibody fragments. Employing this combination resulted in the display of antibody fragments for up to 25% of cells. Despite significantly reduced expression levels in PSD compared to well-established YSD in S. cerevisiae, similar fractions of antigen binding single-chain variable fragments (scFvs) were observed (80% vs. 84%). In addition, plasmid stability assays and flow cytometric analysis demonstrated the efficient plasmid clearance of cells and associated loss of antibody fragment display after removal of selective pressure. KEY POINTS: • First report of antibody display in P. pastoris using episomal plasmids. • Identification of genetic elements conferring highest levels of antibody display. • Comparable antigen binding capacity of displayed scFvs for PSD compared to YSD.

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.

New Opportunities in Glycan Engineering for Therapeutic Proteins

Glycans as sugar polymers are important metabolic, structural, and physiological regulators for cellular and biological functions. They are often classified as critical quality attributes to antibodies and recombinant fusion proteins, given their impacts on the efficacy and safety of biologics drugs. Recent reports on the conjugates of N-acetyl-galactosamine and mannose-6-phosphate for lysosomal degradation, Fab glycans for antibody diversification, as well as sialylation therapeutic modulations and O-linked applications, have been fueling the continued interest in glycoengineering. The current advancements of the human glycome and the development of a comprehensive network in glycosylation pathways have presented new opportunities in designing next-generation therapeutic proteins.

Strains and Molecular Tools for Recombinant Protein Production in Pichia pastoris

Within the last two decades, the methylotrophic yeast Pichia pastoris (Komagataella phaffii) has become an important alternative to E. coli or mammalian cell lines for the production of recombinant proteins. Easy handling, strong promoters, and high cell density cultivations as well as the capability of posttranslational modifications are some of the major benefits of this yeast. The high secretion capacity and low level of endogenously secreted proteins further promoted the rapid development of a versatile Pichia pastoris toolbox. This chapter reviews common and new "Pichia tools" and their specific features. Special focus is given to expression strains, such as different methanol utilization, protease-deficient or glycoengineered strains, combined with application highlights. Different promoters and signal sequences are also discussed.

IgG N-glycans

Glycosylation, one of the most common post-translational modifications in mammalian cells, impacts many biological processes such as cell adhesion, proliferation and differentiation. As the most abundant glycoprotein in human serum, immunoglobulin G (IgG) plays a vital role in immune response and protection. There is a growing body of evidence suggests that IgG structure and function are modulated by attached glycans, especially N-glycans, and aberrant glycosylation is associated with disease states. In this chapter, we review IgG glycan repertoire and function, strategies for profiling IgG N-glycome and recent studies. Mass spectrometry (MS) based techniques are the most powerful tools for profiling IgG glycome. IgG glycans can be divided into high-mannose, biantennary complex and hybrid types, modified with mannosylation, core-fucosylation, galactosylation, bisecting GlcNAcylation, or sialylation. Glycosylation of IgG affects antibody half-life and their affinity and avidity for antigens, regulates crystallizable fragment (Fc) structure and Fcγ receptor signaling, as well as antibody effector function. Because of their critical roles, IgG N-glycans appear to be promising biomarkers for various disease states. Specific IgG glycosylation can convert a pro-inflammatory response to an anti-inflammatory activity. Accordingly, IgG glycoengineering provides a powerful approach to potentially develop effective drugs and treat disease. Based on the understanding of the functional role of IgG glycans, the development of vaccines with enhanced capacity and long-term protection are possible in the near future.

Purification of Modified Therapeutic Proteins Available on the Market: An Analysis of Chromatography-Based Strategies

Proteins, which have inherent biorecognition properties, have long been used as therapeutic agents for the treatment of a wide variety of clinical indications. Protein modification through covalent attachment to different moieties improves the therapeutic's pharmacokinetic properties, affinity, stability, confers protection against proteolytic degradation, and increases circulation half-life. Nowadays, several modified therapeutic proteins, including PEGylated, Fc-fused, lipidated, albumin-fused, and glycosylated proteins have obtained regulatory approval for commercialization. During its manufacturing, the purification steps of the therapeutic agent are decisive to ensure the quality, effectiveness, potency, and safety of the final product. Due to the robustness, selectivity, and high resolution of chromatographic methods, these are recognized as the gold standard in the downstream processing of therapeutic proteins. Moreover, depending on the modification strategy, the protein will suffer different physicochemical changes, which must be considered to define a purification approach. This review aims to deeply analyze the purification methods employed for modified therapeutic proteins that are currently available on the market, to understand why the selected strategies were successful. Emphasis is placed on chromatographic methods since they govern the purification processes within the pharmaceutical industry. Furthermore, to discuss how the modification type strongly influences the purification strategy, the purification processes of three different modified versions of coagulation factor IX are contrasted.

Customized yeast cell factories for biopharmaceuticals: from cell engineering to process scale up

The manufacture of recombinant therapeutics is a fastest-developing section of therapeutic pharmaceuticals and presently plays a significant role in disease management. Yeasts are established eukaryotic host for heterologous protein production and offer distinctive benefits in synthesising pharmaceutical recombinants. Yeasts are proficient of vigorous growth on inexpensive media, easy for gene manipulations, and are capable of adding post translational changes of eukaryotes. Saccharomyces cerevisiae is model yeast that has been applied as a main host for the manufacture of pharmaceuticals and is the major tool box for genetic studies; nevertheless, numerous other yeasts comprising Pichia pastoris, Kluyveromyces lactis, Hansenula polymorpha, and Yarrowia lipolytica have attained huge attention as non-conventional partners intended for the industrial manufacture of heterologous proteins. Here we review the advances in yeast gene manipulation tools and techniques for heterologous pharmaceutical protein synthesis. Application of secretory pathway engineering, glycosylation engineering strategies and fermentation scale-up strategies in customizing yeast cells for the synthesis of therapeutic proteins has been meticulously described.

Structural insight and stability of TNFR-Fc fusion protein (Etanercept) produced by using transgenic silkworms

Therapeutic proteins expressed using transgenic animals have been of great interest for several years. Especially, transgenic silkworm has been studied intensively because of its ease in handling, low-cost, high-yield and unique glycosylation patterns. However, the physicochemical property of the therapeutic protein expressed in transgenic silkworm remains elusive. Here, we constructed an expression system for the TNFR-Fc fusion protein (Etanercept) using transgenic silkworm. The TNFR-Fc fusion protein was employed to N-glycan analysis, which revealed an increased amount of afucosylated protein. Evidence from surface plasmon resonance analysis showed that the TNFR-Fc fusion protein exhibit increased binding affinity for Fcγ receptor IIIa and FcRn compared to the commercial Etanercept, emphasizing the profit of expression system using transgenic silkworm. We have further discussed the comparison of higher order structure, thermal stability and aggregation of the TNFR-Fc fusion protein.

The role of ligand-binding assay and LC-MS in the bioanalysis of complex protein and oligonucleotide therapeutics

Ligand-binding assay (LBA) and LC-MS have been the preferred bioanalytical techniques for the quantitation and biotransformation assessment of various therapeutic modalities. This review provides an overview of the applications of LBA, LC-MS/MS and LC-HRMS for the bioanalysis of complex protein therapeutics including antibody-drug conjugates, fusion proteins and PEGylated proteins as well as oligonucleotide therapeutics. The strengths and limitations of LBA and LC-MS, along with some guidelines on the choice of appropriate bioanalytical technique(s) for the bioanalysis of these therapeutic modalities are presented. With the discovery of novel and more complex therapeutic modalities, there is an increased need for the biopharmaceutical industry to develop a comprehensive bioanalytical strategy integrating both LBA and LC-MS.

Glycoengineering Chinese hamster ovary cells: a short history

Biotherapeutic glycoproteins have revolutionised the field of pharmaceuticals, with new discoveries and continuous improvements underpinning the rapid growth of this industry. N-glycosylation is a critical quality attribute of biotherapeutic glycoproteins that influences the efficacy, half-life and immunogenicity of these drugs. This review will focus on the advances and future directions of remodelling N-glycosylation in Chinese hamster ovary (CHO) cells, which are the workhorse of recombinant biotherapeutic production, with particular emphasis on antibody products, using strategies such as cell line and protein backbone engineering.

Developing a medium combination to attain similar glycosylation profile to originator by DoE and cluster analysis method

Glycosylation is critical for monoclonal antibody production because of its impact on pharmacokinetics and pharmacodynamics. Modulation of glycan profile is frequently needed in biosimilar development. However, glycosylation profile is not a single value like that of cell culture titer, hence making it challenging for the Design of Experiment (DoE) methodology to be directly applied. In this study, a Her2-binding antibody was developed as a biosimilar to Herceptin. Cluster analysis was introduced to demonstrate the similarity of glycan profiles between the samples and the reference with specific value-distance. The glycosylation was subsequently optimized with the DoE method. Basal medium and feed medium were found to be the significant factors to the glycosylation pattern. Moreover, a combination of medium and feed strategy was developed to attain the most similar glycoprotein molecule to that of the originator biologic drug. This study may provide an additional option to evaluate multivariable factors and assess biosimilarity and/or comparability in monoclonal antibody production.

Analytical comparability assessment on glycosylation of ziv-aflibercept and the biosimilar candidate

Ziv-aflibercept (aflibercept) is a recombinant fusion protein which combines the portions of human vascular endothelial growth factor receptors extracellular domains fused to the Fc portion of human IgG1. It is a highly sialylated glycoprotein with 5 N-glycosylation sites. In this study, a comprehensive strategy for comparability study of the complex glycosylation was developed between aflibercept and the biosimilar candidate including the investigations on N-glycosylation sites, site occupancy, site-specific glycoforms, released glycans and sialic acids. The results indicated that same N-glycosylation sites were identified, site occupancy were 100% except N₆₈ site, site-specific glycoforms and released glycans showed similar glycan species, contents of NANA were at a same level for two products. Minor differences were found between two products. The biosimilar candidate presented lower level of aglycosylation, lower level of glycans containing one terminal sialic acid, higher level of glycans containing two terminal sialic acids, higher level of G0F and Man5, lower level of G1F and G2F compared with aflibercept. However, further studies exhibited no differences were observed in the cell-based biological potency and Fc effector function. Moreover, the biosimilar candidate showed a similar pharmacokinetics curve and bioequivalence compared with aflibercept.

The biodistribution of therapeutic proteins: Mechanism, implications for pharmacokinetics, and methods of evaluation

Therapeutic proteins (TPs) are a diverse drug class that include monoclonal antibodies (mAbs), recombinantly expressed enzymes, hormones and growth factors, cytokines (e.g. chemokines, interleukins, interferons), as well as a wide range of engineered fusion scaffolds containing IgG1 Fc domain for half-life extension. As the pharmaceutical industry advances more potent and selective protein-based medicines through discovery and into the clinical stages of development, it has become widely appreciated that a comprehensive understanding of the mechanisms of TP biodistribution can aid this endeavor. This review aims to highlight the literature that has advanced our understanding of the determinants of TP biodistribution. A particular emphasis is placed on the multi-faceted role of the neonatal Fc receptor (FcRn) in mAb and Fc-fusion protein disposition. In addition, characterization of the TP-target interaction at the cell-level is discussed as an essential strategy to establish pharmacokinetic-pharmacodynamic (PK/PD) relationships that may lead to more informed human dose projections during clinical development. Methods for incorporation of tissue and cell-level parameters defining these characteristics into higher-order mechanistic and semi-mechanistic PK models will also be presented.

At-line high throughput site-specific glycan profiling using targeted mass spectrometry

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High throughput, site-specific glycan profiling using targeted mass spectrometry.

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Rapid analysis of glycan profiles directly from culture media.

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Methodology is fully compatible with automation.

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Methodology can be integrated into cell line selection and process development.

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Strategy can be used for multi-attribute product quality screening/monitoring.

Protein post-translational modification (PTM) plays an important role in many biological processes; of which glycosylation is arguably one of the most complex and diverse modifications and is crucial for the safety and efficacy of biotherapeutic proteins.

Mass spectrometric characterization of protein glycosylation is well established with clear advantages and disadvantages; on one hand it is precise and information-rich, as well as being relative inexpensive in terms of the reagents and consumables despite the instrumentation cost and, depending on the method, can give site specific information; on the other hand it generally suffers from low throughput, restriction to largely purified samples and is less quantitative, especially for sialylated glycan species.

Here, we describe a high throughput, site-specific, targeted mass spectrometric peptide mapping approach to quickly screen/rank candidate production cell lines and culture conditions that give favourable glycosylation profiles directly from conditioned culture media for an Fc-fusion protein. The methodology is fully compatible with automation and combines the speed of ‘top-down’ mass spectrometry with the site-specific information of ‘bottom-up’ mass spectrometry. In addition, this strategy can be used for multi-attribute product quality screening/monitoring as an integral part of cell line selection and process development.

Homogeneous production and characterization of recombinant N-GlcNAc-protein in Pichia pastoris

BACKGROUND

Therapeutic glycoproteins have occupied an extremely important position in the market of biopharmaceuticals. N-Glycosylation of protein drugs facilitates them to maintain optimal conformations and affect their structural stabilities, serum half-lives and biological efficiencies. Thus homogeneous N-glycoproteins with defined N-glycans are essential in their application in clinic therapeutics. However, there still remain several obstacles to acquire homogeneous N-glycans, such as the high production costs induced by the universal utilization of mammalian cell expression systems, the non-humanized N-glycan structures and the N-glycosylation microheterogeneities between batches.

RESULTS

In this study, we constructed a Pichia pastoris (Komagataella phaffii) expression system producing truncated N-GlcNAc-modified recombinant proteins through introducing an ENGase isoform (Endo-T) which possesses powerful hydrolytic activities towards high-mannose type N-glycans. The results showed that the location of Endo-T in different subcellular fractions, such as Endoplasmic reticulum (ER), Golgi or cell membrane, affected their hydrolytic efficiencies. When the Endo-T was expressed in Golgi, the secreted IgG1-Fc region was efficiently produced with almost completely truncated N-glycans and the N-GlcNAc modification on the glycosite Asn²⁹⁷ was confirmed via Mass Spectrometry.

CONCLUSION

This strategy develops a simple glycoengineered yeast expression system to produce N-GlcNAc modified proteins, which could be further extended to different N-glycan structures. This system would provide a prospective platform for mass production of increasing novel glycoprotein drugs.

The Mechanistic Impact of N-Glycosylation on Stability, Pharmacokinetics, and Immunogenicity of Therapeutic Proteins

N-glycosylation is one of major post-translational modifications in nature, and it is essential for protein structure and function. As hydrophilic moieties of glycoproteins, N-glycans play important roles in protein stability. They protect the proteins against proteolytic degradation, aggregation, and thermal denaturation through maintaining optimal conformations. There are extensive evidences showing the involvement of N-glycans in the pharmacodynamics and pharmacokinetics of recombinant therapeutic proteins and antibodies. Highly sialylated complex-type glycans enable the longer serum half-lives of proteins against uptake through hepatic asialoglycoprotein receptor and mannose receptor for degradation in lysosomes. Moreover, the presence of nonhuman glycans results in clearance through pre-existing antibodies from serum and induces IgE-mediated anaphylaxis. N-glycans also facilitate or reduce the adverse immune responses of the proteins through interacting with multiple glycan-binding proteins, including those specific for mannose or mannose 6-phosphate. Due to the glycan impacts, a few therapeutic proteins were glycoengineered to improve the pharmacokinetics and stability. Thus, N-glycosylation should be extensively investigated and optimized for each individual protein for better efficacy and safety.

Improving Immunotherapy Through Glycodesign

Immunotherapy is revolutionizing health care, with the majority of high impact "drugs" approved in the past decade falling into this category of therapy. Despite considerable success, glycosylation-a key design parameter that ensures safety, optimizes biological response, and influences the pharmacokinetic properties of an immunotherapeutic-has slowed the development of this class of drugs in the past and remains challenging at present. This article describes how optimizing glycosylation through a variety of glycoengineering strategies provides enticing opportunities to not only avoid past pitfalls, but also to substantially improve immunotherapies including antibodies and recombinant proteins, and cell-based therapies. We cover design principles important for early stage pre-clinical development and also discuss how various glycoengineering strategies can augment the biomanufacturing process to ensure the overall effectiveness of immunotherapeutics.

Pharmacokinetics of monoclonal antibodies and Fc-fusion proteins

There are many factors that can influence the pharmacokinetics (PK) of a mAb or Fc-fusion molecule with the primary determinant being FcRn-mediated recycling. Through Fab or Fc engineering, IgG-FcRn interaction can be used to generate a variety of therapeutic antibodies with significantly enhanced half-life or ability to remove unwanted antigen from circulation. Glycosylation of a mAb or Fc-fusion protein can have a significant impact on the PK of these molecules. mAb charge can be important and variants with pI values of 1-2 unit difference are likely to impact PK with lower pI values being favorable for a longer half-life. Most mAbs display target mediated drug disposition (TMDD), which can have significant consequences on the study designs of preclinical and clinical studies. The PK of mAb can also be influenced by anti-drug antibody (ADA) response and off-target binding, which require careful consideration during the discovery stage. mAbs are primarily absorbed through the lymphatics via convection and can be conveniently administered by the subcutaneous (sc) route in large doses/volumes with co-formulation of hyaluronidase. The human PK of a mAb can be reasonably estimated using cynomolgus monkey data and allometric scaling methods.

Purification Methods for Recombinant Factor VIII Expressed in Human Liver SK-Hep Cells

Coagulation factor VIII is one of the largest proteins attempted to be expressed in recombinant form. A very complex and labile protein which has a very short half-live and need a fast and efficient purification chain. Here, we describe a simple purification sequence using multimodal Capto MMC, affinity FVIII select and ion exchange SP-Fastflow chromatography steps without subjecting the target molecule to mechanical and temperature stress, separating impurities from rFVIII using net charge, hydrophobicity, and affinity of the molecules.

Glycoengineering of EphA4 Fc leads to a unique, long-acting and broad spectrum, Eph receptor therapeutic antagonist

Eph receptors have emerged as targets for therapy in both neoplastic and non-neoplastic disease, however, particularly in non-neoplastic diseases, redundancy of function limits the effectiveness of targeting individual Eph proteins. We have shown previously that a soluble fusion protein, where the EphA4 ectodomain was fused to IgG Fc (EphA4 Fc), was an effective therapy in acute injuries and demonstrated that EphA4 Fc was a broad spectrum Eph/ephrin antagonist. However, a very short in vivo half-life effectively limited its therapeutic development. We report a unique glycoengineering approach to enhance the half-life of EphA4 Fc. Progressive deletion of three demonstrated N-linked sites in EphA4 progressively increased in vivo half-life such that the triple mutant protein showed dramatically improved pharmacokinetic characteristics. Importantly, protein stability, affinity for ephrin ligands and antagonism of cell expressed EphA4 was fully preserved, enabling it to be developed as a broad spectrum Eph/ephrin antagonist for use in both acute and chronic diseases.

Glycoengineering of pertuzumab and its impact on the pharmacokinetic/pharmacodynamic properties

Pertuzumab is an antihuman HER2 antibody developed for HER2 positive breast cancer. Glycosylation profiles are always the important issue for antibody based therapy. Previous findings have suggested the impact of glycosylation profiles on the function of antibodies, like pharmacodynamics, antibody-dependent cellular cytotoxicity (ADCC) and complement-dependent cytotoxicity (CDC). However, the roles of fucose and sialic acid in the function of therapeutic antibodies still need further investigation, especially the role of sialic acid in nonfucosylated antibodies. This study focused on the pharmacokinetic and pharmacodynamic properties of pertuzumab after glycoengineering. Herein, nonfucosylated pertuzumab was produced in CHO^FUT8−/− cells, and desialylated pertuzumab was generated by enzymatic hydrolysis. Present data indicated that fucose was critical for ADCC activity by influencing the interaction between pertuzumab and FcγRIIIa, nevertheless removal of sialic acid increased the ADCC and CDC activity of pertuzumab. Meanwhile, regarding to sialic acid, sialidase hydrolysis directly resulted in asialoglycoprotein receptors (ASGPRs) dependent clearance in hepatic cells in vitro. The pharmacokinetic assay revealed that co-injection of asialofetuin can protect desialylated pertuzumab against ASGPRs-mediated clearance. Taken together, the present study elucidated the importance of fucose and sialic acid for pertuzumab, and also provided further understanding of the relationship of glycosylation/pharmacokinetics/pharmacodynamics of therapeutic antibody.

Fc gamma receptors: glycobiology and therapeutic prospects

Therapeutic antibodies hold great promise for the treatment of cancer and autoimmune diseases, and developments in antibody–drug conjugates and bispecific antibodies continue to enhance treatment options for patients. Immunoglobulin (Ig) G antibodies are proteins with complex modifications, which have a significant impact on their function. The most important of these modifications is glycosylation, the addition of conserved glycans to the antibody Fc region, which is critical for its interaction with the immune system and induction of effector activities such as antibody-dependent cell cytotoxicity, complement activation and phagocytosis. Communication of IgG antibodies with the immune system is controlled and mediated by Fc gamma receptors (FcγRs), membrane-bound proteins, which relay the information sensed and gathered by antibodies to the immune system. These receptors are also glycoproteins and provide a link between the innate and adaptive immune systems. Recent information suggests that this receptor glycan modification is also important for the interaction with antibodies and downstream immune response. In this study, the current knowledge on FcγR glycosylation is discussed, and some insight into its role and influence on the interaction properties with IgG, particularly in the context of biotherapeutics, is provided. For the purpose of this study, other Fc receptors such as FcαR, FcεR or FcRn are not discussed extensively, as IgG-based antibodies are currently the only therapeutic antibody-based products on the market. In addition, FcγRs as therapeutics and therapeutic targets are discussed, and insight into and comment on the therapeutic aspects of receptor glycosylation are provided.

Engineering yeast for producing human glycoproteins: where are we now?

Yeast has advanced as an alternative for mammalian cell culture for the production of recombinant therapeutic glycoproteins. Engineered yeast strains not only allow to mimic the human N-glycosylation pathway but also specific types of human O-glycosylation. This is of great value for therapeutic protein production and indispensable to determine the structure-function relationships of glycans on recombinant proteins. However, as the technology matures, some limitations have come up that may hamper biomedical applications and must be considered to exploit the full potential of the unprecedented glycan homogeneity obtained on relevant biopharmaceuticals. In this special report, we focus on the recent developments in N- and O-glycosylation engineering in yeasts of industrial importance, to produce recombinant therapeutics with customized glycans.

Engineering β1,4-galactosyltransferase I to reduce secretion and enhance N-glycan elongation in insect cells

β1,4-galactosyltransferase I (B4GALT1) is a Golgi-resident enzyme that elongates glycoprotein glycans, but a subpopulation of this enzyme is secreted following proteolytic cleavage in its stem domain. We hypothesized that engineering B4GALT1 to block cleavage and secretion would enhance its retention and, therefore, its function. To test this hypothesis, we replaced the cytoplasmic/transmembrane/stem (CTS) domains of B4GALT1 with those from human α1,3-fucosyltransferase 7 (FUT7), which is not cleaved and secreted. Expression of FUT7-CTS-B4GALT1 in insect cells produced lower levels of secreted and higher levels of intracellular B4GALT1 activity than the native enzyme. We also noted that the B4GALT1 used in our study had a leucine at position 282, whereas all other animal B4GALT1 sequences have an aromatic amino acid at this position. Thus, we examined the combined impact of changing the CTS domains and the amino acid at position 282 on intracellular B4GALT1 activity levels and N-glycan processing in insect cells. The results demonstrated a correlation between the levels of intracellular B4GALT1 activity and terminally galactosylated N-glycans, N-glycan branching, the appearance of hybrid structures, and reduced core fucosylation. Thus, engineering B4GALT1 to reduce its cleavage and secretion is an approach that can be used to enhance N-glycan elongation in insect cells.

Biopharmaceutical discovery and production in yeast

The selection of an expression platform for recombinant biopharmaceuticals is often centered upon suitable product titers and critical quality attributes, including post-translational modifications. Although notable differences between microbial, yeast, plant, and mammalian host systems exist, recent advances have greatly mitigated any inherent liabilities of yeasts. Yeast expression platforms are important to both the supply of marketed biopharmaceuticals and the pipelines of novel therapeutics. In this review, recent advances in yeast-based expression of biopharmaceuticals will be discussed. The advantages of using glycoengineered yeast as a production host and in the discovery space will be illustrated. These advancements, in turn, are transforming yeast platforms from simple production systems to key technological assets in the discovery and selection of biopharmaceutical lead candidates.

Strains and molecular tools for recombinant protein production in Pichia pastoris

Within the last two decades, the methylotrophic yeast Pichia pastoris has become an important alternative to E. coli or mammalian cell lines for the production of recombinant proteins. Easy handling, strong promoters, and high cell density cultivations as well as the capability of posttranslational modifications are some of the major benefits of this yeast. The high secretion capacity and low level of endogenously secreted proteins further promoted the rapid development of a versatile Pichia pastoris toolbox. This chapter reviews common and new "Pichia tools" and their specific features. Special focus is given to expression strains, such as different methanol utilization, protease-deficient or glycoengineered strains, combined with application highlights. Different promoters and signal sequences are also discussed.

Characterization of the Pichia pastoris protein-O-mannosyltransferase gene family

The methylotrophic yeast, Pichiapastoris, is an important organism used for the production of therapeutic proteins. However, the presence of fungal-like glycans, either N-linked or O-linked, can elicit an immune response or enable the expressed protein to bind to mannose receptors, thus reducing their efficacy. Previously we have reported the elimination of β-linked glycans in this organism. In the current report we have focused on reducing the O-linked mannose content of proteins produced in P. pastoris, thereby reducing the potential to bind to mannose receptors. The initial step in the synthesis of O-linked glycans in P. pastoris is the transfer of mannose from dolichol-phosphomannose to a target protein in the yeast secretory pathway by members of the protein-O-mannosyltransferase (PMT) family. In this report we identify and characterize the members of the P. pastoris PMT family. Like Candida albicans, P. pastoris has five PMT genes. Based on sequence homology, these PMTs can be grouped into three sub-families, with both PMT1 and PMT2 sub-families possessing two members each (PMT1 and PMT5, and PMT2 and PMT6, respectively). The remaining sub-family, PMT4, has only one member (PMT4). Through gene knockouts we show that PMT1 and PMT2 each play a significant role in O-glycosylation. Both, by gene knockouts and the use of Pmt inhibitors we were able to significantly reduce not only the degree of O-mannosylation, but also the chain-length of these glycans. Taken together, this reduction of O-glycosylation represents an important step forward in developing the P. pastoris platform as a suitable system for the production of therapeutic glycoproteins.