O-linked sugar chain of human granulocyte colony-stimulating factor protects it against polymerization and denaturation allowing it to retain its biological activity

Combining machine learning with structure-based protein design to predict and engineer post-translational modifications of proteins

Post-translational modifications (PTMs) of proteins play a vital role in their function and stability. These modifications influence protein folding, signaling, protein-protein interactions, enzyme activity, binding affinity, aggregation, degradation, and much more. To date, over 400 types of PTMs have been described, representing chemical diversity well beyond the genetically encoded amino acids. Such modifications pose a challenge to the successful design of proteins, but also represent a major opportunity to diversify the protein engineering toolbox. To this end, we first trained artificial neural networks (ANNs) to predict eighteen of the most abundant PTMs, including protein glycosylation, phosphorylation, methylation, and deamidation. In a second step, these models were implemented inside the computational protein modeling suite Rosetta, which allows flexible combination with existing protocols to model the modified sites and understand their impact on protein stability as well as function. Lastly, we developed a new design protocol that either maximizes or minimizes the predicted probability of a particular site being modified. We find that this combination of ANN prediction and structure-based design can enable the modification of existing, as well as the introduction of novel, PTMs. The potential applications of our work include, but are not limited to, glycan masking of epitopes, strengthening protein-protein interactions through phosphorylation, as well as protecting proteins from deamidation liabilities. These applications are especially important for the design of new protein therapeutics where PTMs can drastically change the therapeutic properties of a protein. Our work adds novel tools to Rosetta's protein engineering toolbox that allow for the rational design of PTMs.

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.

Immunogenicity of Therapeutic Biological Modalities - Lessons from Hemophilia A Therapies

The introduction and development of biologics such as therapeutic proteins, gene-, and cell-based therapy have revolutionized the scope of treatment for many diseases. However, a significant portion of the patients develop unwanted immune reactions against these novel biological modalities, referred to as immunogenicity, and no longer benefit from the treatments. In the current review, using Hemophilia A (HA) therapy as an example, we will discuss the immunogenicity issue of multiple biological modalities. Currently, the number of therapeutic modalities that are approved or recently explored to treat HA, a hereditary bleeding disorder, is increasing rapidly. These include, but are not limited to, recombinant factor VIII proteins, PEGylated FVIII, FVIII Fc fusion protein, bispecific monoclonal antibodies, gene replacement therapy, gene editing therapy, and cell-based therapy. They offer the patients a broader range of more advanced and effective treatment options, yet immunogenicity remains the most critical complication in the management of this disorder. Recent advances in strategies to manage and mitigate immunogenicity will also be reviewed.

Semisynthesis of Homogeneous, Active Granulocyte Colony-Stimulating Factor Glycoforms

Granulocyte colony stimulating factor (G-CSF) is a cytokine used to treat neutropenia. Different glycosylated and non-glycosylated variants of G-CSF for therapeutic application are currently generated by recombinant expression. Here, we describe our approaches to establish a first semisynthesis strategy to access the aglycone and O-glycoforms of G-CSF, thereby enabling the preparation of selectively and homogeneously post-translationally modified variants of this important cytokine. Eventually, we succeeded by combining selenocysteine ligation of a recombinantly produced N-terminal segment with a synthetic C-terminal part, transiently equipped with a side-chain-linked, photocleavable PEG moiety, at low concentration. The transient PEGylation enabled quantitative enzymatic elongation of the carbohydrate at Thr133. Overall, we were able to significantly reduce the problems related to the low solubility and the tendency to aggregate of the two protein segments, which allowed the preparation of four G-CSF variants that were successfully folded and demonstrated biological activity in cell proliferation assays.

Impact of Extractables/Leachables from Filter Materials on the Stability of Protein-Based Pharmaceutical Products

The manufacturing of biopharmaceutical drug solutions can involve close contact with various polymeric components, including common filter membranes. Potential leachable substances from filters may interact with the protein and thereby increase the structural damage and aggregation. The main aim of the study deals with the assessment of extractable and leachable (E/L) from different filters and the potential effect of E/Ls on protein (human granulocyte-colony stimulating factor (rh-GCSF) stability. The present study examines the E/L profile of five different polymeric filter membranes using various chromatographic techniques including LC-MS and GC-MS. In order to investigate their effect on protein stability, G-CSF (human granulocyte colony-stimulating factor) formulations were spiked with filter leachable stock solutions at two different pH levels. The spiked formulations were further analyzed with respect to their aggregation behavior. The results demonstrated a higher E/L content in the case of polyamide (PA), polycarbonate (PC), and polyethersulfone (PES) filters as compared to the polytetrafluoroethylene (PTFE) and regenerative cellulose (RC) filter materials. The E/L from RC and PES was found surface-active, whereas E/L from PA and RC significantly altered the particle size/structure resulting in the aggregation of proteins. Furthermore, bisphenol A was found to be one of the E/L substances from PC filters and can impose significant health problems when administered along with pharmaceutical products. The present study reports a qualitative rank ordering of the filter membranes in terms of their propensity to generate E/Ls and thus can be helpful in selecting a suitable membrane filter.

Hematopoietic stem cell mobilization strategies to support high-dose chemotherapy: A focus on relapsed/refractory germ cell tumors

High-dose chemotherapy (HDCT) with autologous hematopoietic stem cell transplantation has been explored and has played an important role in the management of patients with high-risk germ cell tumors (GCTs) who failed to be cured by conventional chemotherapy. Hematopoietic stem cells (HSCs) collected from the peripheral blood, after appropriate pharmacologic mobilization, have largely replaced bone marrow as the principal source of HSCs in transplants. As it is currently common practice to perform tandem or multiple sequential cycles of HDCT, it is anticipated that collection of large numbers of HSCs from the peripheral blood is a prerequisite for the success of the procedure. Moreover, the CD34+ cell dose/kg of body weight infused after HDCT has proven to be a major determinant of hematopoietic engraftment, with patients who receive > 2 × 10⁶ CD34+ cells/kg having consistent, rapid, and sustained hematopoietic recovery. However, many patients with relapsed/refractory GCTs have been exposed to multiple cycles of myelosuppressive chemotherapy, which compromises the efficacy of HSC mobilization with granulocyte colony-stimulating factor with or without chemotherapy. Therefore, alternative strategies that use novel agents in combination with traditional mobilizing regimens are required. Herein, after an overview of the mechanisms of HSCs mobilization, we review the existing literature regarding studies reporting various HSC mobilization approaches in patients with relapsed/refractory GCTs, and finally report newer experimental mobilization strategies employing novel agents that have been applied in other hematologic or solid malignancies.

A high-affinity RBD-targeting nanobody improves fusion partner's potency against SARS-CoV-2

A key step to the SARS-CoV-2 infection is the attachment of its Spike receptor-binding domain (S RBD) to the host receptor ACE2. Considerable research has been devoted to the development of neutralizing antibodies, including llama-derived single-chain nanobodies, to target the receptor-binding motif (RBM) and to block ACE2-RBD binding. Simple and effective strategies to increase potency are desirable for such studies when antibodies are only modestly effective. Here, we identify and characterize a high-affinity synthetic nanobody (sybody, SR31) as a fusion partner to improve the potency of RBM-antibodies. Crystallographic studies reveal that SR31 binds to RBD at a conserved and 'greasy' site distal to RBM. Although SR31 distorts RBD at the interface, it does not perturb the RBM conformation, hence displaying no neutralizing activities itself. However, fusing SR31 to two modestly neutralizing sybodies dramatically increases their affinity for RBD and neutralization activity against SARS-CoV-2 pseudovirus. Our work presents a tool protein and an efficient strategy to improve nanobody potency.

Photo-induced radical thiol-ene chemistry: a versatile toolbox for peptide-based drug design

While the global market for peptide/protein-based therapeutics is witnessing significant growth, the development of peptide drugs remains challenging due to their low oral bioavailability, poor membrane permeability, and reduced metabolic stability. However, a toolbox of chemical approaches has been explored for peptide modification to overcome these obstacles. In recent years, there has been a revival of interest in photoinduced radical thiol-ene chemistry as a powerful tool for the construction of therapeutic peptides.

Structural and functional diversity of neutrophil glycosylation in innate immunity and related disorders

The granulated neutrophils are abundant innate immune cells that utilize bioactive glycoproteins packed in cytosolic granules to fight pathogenic infections, but the neutrophil glycobiology remains poorly understood. Facilitated by technological advances in glycoimmunology, systems glycobiology and glycoanalytics, a considerable body of literature reporting on novel aspects of neutrophil glycosylation has accumulated. Herein, we summarize the building knowledge of the structural and functional diversity displayed by N- and O-linked glycoproteins spatiotemporally expressed and sequentially brought-into-action across the diverse neutrophil life stages during bone marrow maturation, movements to, from and within the blood circulation and microbicidal processes at the inflammatory sites in peripheral tissues. It transpires that neutrophils abundantly decorate their granule glycoproteins including neutrophil elastase, myeloperoxidase and cathepsin G with peculiar glyco-signatures not commonly reported in other areas of human glycobiology such as hyper-truncated chitobiose core- and paucimannosidic-type N-glycans and monoantennary complex-type N-glycans. Sialyl Lewis^x, Lewis^x, poly-N-acetyllactosamine extensions and core 1-/2-type O-glycans are also common neutrophil glyco-signatures. Granule-specific glycosylation is another fascinating yet not fully understood feature of neutrophils. Recent literature suggests that unconventional biosynthetic pathways and functions underpin these prominent neutrophil-associated glyco-phenotypes. The impact of glycosylation on key neutrophil effector functions including extravasation, degranulation, phagocytosis and formation of neutrophil extracellular traps during normal physiological conditions and in innate immune-related diseases is discussed. We also highlight new technologies that are expected to further advance neutrophil glycobiology and briefly discuss the untapped diagnostic and therapeutic potential of neutrophil glycosylation that could open avenues to combat the increasingly prevalent innate immune disorders.

The establishment of new protein expression system using N starvation inducible promoters in Chlorella

Chlorella is a unicellular green microalga that has been used in fields such as bioenergy production and food supplementation. In this study, two promoters of N (nitrogen) deficiency-inducible Chlorella vulgaris N Deficiency Inducible (CvNDI) genes were isolated from Chlorella vulgaris UTEX 395. These promoters were used for the production of a recombinant protein, human granulocyte-colony stimulating factor (hG-CSF) in Chlorella vulgaris UTEX 395 and Chlorella sp. ArM0029B. To efficiently secrete the hG-CSF, the protein expression vectors incorporated novel signal peptides obtained from a secretomics analysis of Chlorella spp. After a stable transformation of those vectors with a codon-optimized hG-CSF sequence, hG-CSF polypeptides were successfully produced in the spent media of the transgenic Chlorella. To our knowledge, this is the first report of recombinant protein expression using endogenous gene components of Chlorella.

Synthetic Glycobiology: Parts, Systems, and Applications

Protein glycosylation, the attachment of sugars to amino acid side chains, can endow proteins with a wide variety of properties of great interest to the engineering biology community. However, natural glycosylation systems are limited in the diversity of glycoproteins they can synthesize, the scale at which they can be harnessed for biotechnology, and the homogeneity of glycoprotein structures they can produce. Here we provide an overview of the emerging field of synthetic glycobiology, the application of synthetic biology tools and design principles to better understand and engineer glycosylation. Specifically, we focus on how the biosynthetic and analytical tools of synthetic biology have been used to redesign glycosylation systems to obtain defined glycosylation structures on proteins for diverse applications in medicine, materials, and diagnostics. We review the key biological parts available to synthetic biologists interested in engineering glycoproteins to solve compelling problems in glycoscience, describe recent efforts to construct synthetic glycoprotein synthesis systems, and outline exemplary applications as well as new opportunities in this emerging space.

Structural Aspects of the O-glycosylation Linkage in Glycopeptides via MD Simulations and Comparison with NMR Experiments

A powerful conformational searching and enhanced sampling simulation method, and unbiased molecular dynamics simulations have been used along with NMR spectroscopic observables to provide a detailed structural view of O-glycosylation. For four model systems, the force-field parameters can accurately predict experimental NMR observables (J couplings and NOE's). This enables us to derive conclusions based on the generated ensembles, in which O-glycosylation affects the peptide backbone conformation by forcing it towards to an extended conformation. An exception is described for β-GalNAc-Thr where the α content is increased and stabilized via hydrogen bonding between the sugar and the peptide backbone, which was not observed in the rest of the studied systems. These observations might offer an explanation for the evolutionary preference of α-linked GalNAc glycosylation instead of a β link.

Generic Substitution of Orphan Drugs for the Treatment of Rare Diseases: Exploring the Potential Challenges

Generic drugs are important components of measures introduced by healthcare regulatory authorities to reduce treatment costs. In most patients and conditions the switch from a branded drug to its generic counterpart is performed with no major complications. However, evidence from complex diseases suggests that generic substitution requires careful evaluation in some settings and that current bioequivalence criteria may not always be adequate for establishing the interchangeability of branded and generic products. Rare diseases, also called orphan diseases, are a group of heterogeneous diseases that share important characteristics: in addition to their scarcity, most are severe, chronic, highly debilitating, and often present in early childhood. Finding a treatment for a rare disease is challenging. Thanks to incentives that encourage research and development programs in rare diseases, several orphan drugs are currently available. The elevated cost of orphan drugs is a highly debated issue and a cause of limited access to treatment for many patients. As patent protection and the exclusivity period of several orphan drugs will expire soon, generic versions of orphan drugs should reach the market shortly, with great expectations about their impact on the economic burden of rare diseases. However, consistent with other complex diseases, generic substitution may require thoughtful considerations and may be even contraindicated in some rare conditions. This article provides an overview of rare disease characteristics, reviews reports of problematic generic substitution, and discusses why generic substitution of orphan drugs may be challenging and should be undertaken carefully in rare disease patients.

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.

Transient co-expression with three O-glycosylation enzymes allows production of GalNAc-O-glycosylated Granulocyte-Colony Stimulating Factor in N. benthamiana

BACKGROUND

Expression of economically relevant proteins in alternative expression platforms, especially plant expression platforms, has gained significant interest in recent years. A special interest in working with plants as bioreactors for the production of pharmaceutical proteins is related to low production costs, product safety and quality. Among the different properties that plants can also offer for the production of recombinant proteins, protein glycosylation is crucial since it may have an impact on pharmaceutical functionality and/or stability.

RESULTS

The pharmaceutical glycoprotein human Granulocyte-Colony Stimulating Factor was transiently expressed in Nicotiana benthamiana plants and subjected to mammalian-specific mucin-type O-glycosylation by co-expressing the pharmaceutical protein together with the glycosylation machinery responsible for such post-translational modification.

CONCLUSIONS

The pharmaceutical glycoprotein human Granulocyte-Colony Stimulating Factor can be expressed in N. benthamiana plants via agroinfiltration with its native mammalian-specific mucin-type O-glycosylation.

Fully Synthetic Granulocyte Colony-Stimulating Factor Enabled by Isonitrile-Mediated Coupling of Large, Side-Chain-Unprotected Peptides

Human granulocyte colony-stimulating factor (G-CSF) is an endogenous glycoprotein involved in hematopoiesis. Natively glycosylated and nonglycosylated recombinant forms, lenograstim and filgrastim, respectively, are used clinically to manage neutropenia in patients undergoing chemotherapeutic treatment. Despite their comparable therapeutic potential, the purpose of O-linked glycosylation at Thr133 remains a subject of controversy. In light of this, we have developed a synthetic platform to prepare G-CSF aglycone with the goal of enabling access to native and designed glycoforms with site-selectivity and glycan homogeneity. To address the synthesis of a relatively large, aggregation-prone sequence, we advanced an isonitrile-mediated ligation method. The chemoselective activation and coupling of C-terminal peptidyl Gly thioacids with the N-terminus of an unprotected peptide provide ligated peptides directly in a manner complementary to that with conventional native chemical ligation-desulfurization strategies. Herein, we describe the details and application of this method as it enabled the convergent total synthesis of G-CSF aglycone.

Expression and Control of Codon-Optimized Granulocyte Colony-Stimulating Factor in Pichia pastoris

Granulocyte colony-stimulating factor (GCSF) has therapeutic applications due to its proven efficacy in different forms of neutropenia and chemotherapy-induced leucopenia. The original 564-bp nucleotide sequence from NCBI was codon optimized and assembled by overlapping PCR method comprising of 16 oligos of 50-nt length with 15 base overhang. The synthetic gene (CO-GCSF) was cloned under glucose utilizing glyceraldehyde 3-phosphate dehydrogenase (GAP) and methanol-utilizing alcohol oxidase (AOX1) promoters and expressed in Pichia pastoris SMD1168 strain. Constitutive expression under GAP resulted in cellular toxicity while AOX1 promoter controlled expression was stable. Variation in the levels of expression was observed among the transformant colonies with transformant #2 secreting up to ∼4 mg/L of GCSF. The molecular mass of the expressed GCSF in P. pastoris was ∼19.0 kDa. Quatitation of the expressed protein was carried out by a highly reproducible gel densitometric method. Effect of several operational and nutritional conditions was studied on GCSF production and the results suggest a general approach for increasing the yield of GCSF several folds (2- to 5-fold) over the standard conditions employed currently. Cultivation of the single-copy integrant in the chemically defined medium in a 5-L fermenter resulted in a volumetric productivity of ∼0.7 mg/L/h at the end of the induction phase, which was about 4-fold higher than attained in the shake flask.

Use of biosimilar filgrastim compared with lenograstim in autologous haematopoietic stem-cell transplant and in sibling allogeneic transplant

OBJECTIVES

Biosimilar filgrastim was compared with lenograstim for autologous haematopoietic stem-cell transplant (HSCT) in patients with haematological malignancies. Data from a separate group of sibling donors who underwent allogeneic HSCT are also reported.

METHODS

Patients with lymphoma or multiple myeloma (MM) who underwent autologous HSCT with biosimilar filgrastim were compared with a historical control group of patients who received lenograstim. Peripheral blood (PB) cells counts were monitored after 7-8 consecutive days of granulocyte-colony stimulating factor (G-CSF) injection and apheresis was performed on day 8 if PB CD34+ cell count was ⩾10 cells/µl. The target PB CD34+ cell doses were ⩾2.0 × 10(6)/kg (lymphoma), ⩾4.0 × 10(6)/kg (MM ⩾60 years old) or ⩾8.0 × 10(6)/kg (MM <60 years old).

RESULTS

A total of 259 patients were included in the autologous HSCT comparison (biosimilar filgrastim, n = 104; lenograstim, n = 155). In patients with lymphoma and older MM patients (⩾60 years old), no significant differences were observed between groups with regard to stem-cell mobilization parameters. However, in MM patients <60 years old, all parameters were significantly superior in the biosimilar filgrastim group, including the need for 1 rather than 2 apheresis procedures. No significant differences were observed between groups in median number of days to absolute neutrophil count (ANC) or platelet recovery. In the allogeneic setting, 47 sibling donors received biosimilar filgrastim. Mean CD34+ count at the first apheresis was 6.1 × 10(6)/kg. A total of 13 donors needed a second apheresis and 4 required a third. Among recipients, median days to ANC recovery was 16 (10-28) and to platelet recovery was 13 (9-54).

CONCLUSIONS

Biosimilar filgrastim is as effective as lenograstim for autologous HSCT in patients with lymphoma or MM patients ⩾60 years old. However, mobilization with biosimilar filgrastim appeared to be superior to that with lenograstim in younger MM patients.

Expression of the functional recombinant human glycosyltransferase GalNAcT2 in Escherichia coli

BACKGROUND

Recombinant protein-based therapeutics have become indispensable for the treatment of many diseases. They are produced using well-established expression systems based on bacteria, yeast, insect and mammalian cells. The majority of therapeutic proteins are glycoproteins and therefore the post-translational attachment of sugar residues is required. The development of an engineered Escherichia coli-based expression system for production of human glycoproteins could potentially lead to increased yields, as well as significant decreases in processing time and costs.

RESULTS

This work describes the expression of functional human-derived glycosyltransferase UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase 2 (GalNAcT2) in a recombinant E. coli strain. For expression, a codon-optimised gene encoding amino acids 52-571 of GalNAcT2 lacking the transmembrane N-terminal domain was inserted into a pET-23 derived vector encoding a polyhistidine-tag which was translationally fused to the N-terminus of the glycosyltransferase (HisDapGalNAcT2). The glycosyltransferase was produced in E. coli using a recently published expression system. Soluble HisDapGalNAcT2 produced in SHuffle® T7 host cells was purified using nickel affinity chromatography and was subsequently analysed by size exclusion chromatography coupled to multi-angle light scattering (SEC-MALS) and circular dichroism spectroscopy to determine molecular mass, folding state and thermal transitions of the protein. The activity of purified HisDapGalNAcT2 was monitored using a colorimetric assay based on the release of phosphate during transfer of glycosyl residues to a model acceptor peptide or, alternatively, to the granulocyte-colony stimulating growth factor (G-CSF). Modifications were assessed by Matrix Assisted Laser Desorption Ionization Time-of-flight Mass Spectrometry analysis (MALDI-TOF-MS) and Electrospray Mass Spectrometry analysis (ESI-MS). The results clearly indicate the glycosylation of the acceptor peptide and of G-CSF.

CONCLUSION

In the present work, we isolated a human-derived glycosyltransferase by expressing soluble HisDapGalNAcT2 in E. coli. The functional activity of the enzyme was shown in vitro. Further investigations are needed to assess the potential of in vivo glycosylation in E. coli.

Formulation and stability of cytokine therapeutics

Cytokines are messenger proteins that regulate the proliferation and differentiation of cells and control immune responses. Interferons, interleukins, and growth factors have applications in cancer, autoimmune, and viral disease treatment. The cytokines are susceptible to chemical and physical instability. This article reviews the structure and stability issues of clinically used cytokines, as well as formulation strategies for improved stability. Some general aspects for identifying most probable stability concerns, selecting excipients, and developing stable cytokine formulations are presented. The vast group of cytokines offers possibilities for new biopharmaceuticals. The formulation approaches of the current cytokine products could facilitate development of new biopharmaceuticals.

Comparison of filgrastim and lenograstim in pediatric solid tumors

PURPOSE

Chemotherapy-induced febrile neutropenia (FEN), which causes treatment delays or chemotherapy dose reductions, is a serious side effect of cancer treatment. In Turkey, recombinant G-CSF (rG-CSF) has been used since 2000 to control neutropenia. The purpose of this prospective randomized study is to compare the effectiveness, toxicities and the cost of these two drugs in children.

METHODS

Between April and December 2008, 29 patients were administered 40 courses of chemotherapy in each arm. A randomized crossover study was designed. All patients were administered rG-CSF 24 hours after the last day of chemotherapy as a secondary prophylaxis. Complete blood counts as well as peripheral blood progenitor (CD34+) cell levels were measured before G-CSF treatment and on the fifth and the seventh day of treatment.

RESULTS

The median duration of neutropenia, FEN, the length of hospitalization, the incidence of FEN, and documented infection was not different between the two rG-CSF treatment groups. Erythrocyte and platelet transfusion rates were also similar. After 7 days, the mean leukocyte (WBC [white blood cell]) and neutrophil count (ANC [absolute neutrophil count]), hemoglobin and platelet levels were not significantly different. However, the CD34+ cell level was significantly higher in the lenograstim group. Lenograstim was also more expensive than filgrastim. No serious side effects were reported for either rG-CSF treatment.

CONCLUSIONS

There is no difference following the administration of either lenograstim or filgrastim for the duration of neutropenia, FEN or hospitalization for pediatric cancer patients. For stem cell mobilization, lenograstim was superior to filgrastim.

Characterization of disulfide linkages in recombinant human granulocyte-colony stimulating factor

RATIONALE

Recombinant human G granulocyte-colony stimulating factor (rhG-CSF) produced in Escherichia coli is a non-glycosylated polypeptide containing five cysteine residues. The reported major disulfide (S-S) linkages in mature human G-CSF are C36 -C42 and C64 -C74 , leaving C17 as a free cysteine, which could potentially result in S-S scrambling. The purpose of this work is to illustrate different mass spectrometry (MS) approaches for characterization of S-S linkages in therapeutic proteins including S-S scrambling using rhG-CSF as a model protein.

METHODS

Peptide mapping analysis of both non-reduced and reduced digests of rhG-CSF was performed to demonstrate the presence of S-S linked peptides and their corresponding reduced peptides. High mass accuracy measurements of these peptides provided the initial identifications of S-S linkages. Collision-induced dissociation (CID) and electron transfer dissociation (ETD) were used to fragment these peptides in order to obtain further sequence information and identify S-S linkages.

RESULTS

S-S linked peptides and their corresponding reduced peptides correlating with major S-S linkages were observed. Peptides that correlated with other S-S linkages as a result of S-S scrambling were also observed.

CONCLUSIONS

Presence of the reported major S-S linkages in rhG-CSF was confirmed. S-S scrambling was also observed in which C18 was involved in S-S linkages and C37 , C65 or C75 were present as free cysteines. This study demonstrates the practical utility of combining different MS methods for characterization of S-S linkages in therapeutic proteins.

A single N-acetylgalactosamine residue at threonine 106 modifies the dynamics and structure of interferon α2a around the glycosylation site

Enzymatic addition of GalNAc to isotopically labeled IFNα2a produced in Escherichia coli yielded the O-linked glycoprotein GalNAcα-[(13)C,(15)N]IFNα2a. The three-dimensional structure of GalNAcα-IFNα2a has been determined in solution by NMR spectroscopy at high resolution. Proton-nitrogen heteronuclear Overhauser enhancement measurements revealed that the addition of a single monosaccharide unit at Thr-106 significantly slowed motions of the glycosylation loop on the nanosecond time scale. Subsequent addition of a Gal unit produced Gal(β1,3)GalNAcα-[(13)C,(15)N]IFNα2a. This extension resulted in a further decrease in the dynamics of this loop. The methodology used here allowed the first such description of the structure and dynamics of an O-glycoprotein and opens the way to the study of this class of proteins.

A new site-specific monoPEGylated filgrastim derivative prepared by enzymatic conjugation: Production and physicochemical characterization

We describe the preparation and characterization of a new monoPEGylated derivate of a recombinant form of filgrastim (methionyl human granulocite colony stimulating factor, rh-Met-G-CSF), BK0026, prepared by enzymatic site-specific 20kDa PEG conjugation to glutamine 135 residue by microbial transglutaminase catalyzed reaction. BK0026 was purified to a clinical grade by a single cation exchange chromatography step and characterized by using a panel of physicochemical analyses. NH(2)-terminal sequence and peptide mapping demonstrated no differences between the primary structure of BK0026 and the non-PEGylated filgrastim. The circular dichroism and fluorescence spectroscopy showed the preservation of high order protein structure. The single conjugation site on glutamine 135 was identified by endoproteinase Glu-C peptide mapping combined with mass spectrometry analysis and NH(2)-terminal sequence of the PEGylated peptides. BK0026 purity as well as product- and process-related contaminants was determined by several analytical methods, which showed that BK0026 is stable for more than 2 years when stored at 4-8°C. The advantages of enzymatic PEGylation of filgrastim are the absolute specificity of glutamine 135 conjugation combined with high PEGylation yields under very mild reaction conditions. The new site specific monoPEGylated filgrastim is a promising candidate for preclinical and clinical studies aimed at developing a long-lasting treatment of neutropenia in oncological patients under chemotherapy treatments.

Protein glycosylation and its impact on biotechnology

Glycosylation is a post-translational modification that is of paramount importance in the production of recombinant pharmaceuticals as most recombinantly produced therapeutics are N- and/or O-glycosylated. Being a cell-system-dependent process, it also varies with expression systems and growth conditions, which result in glycan microheterogeneity and macroheterogeneity. Glycans have an effect on drug stability, serum half-life, and immunogenicity; it is therefore important to analyze and optimize the glycan decoration of pharmaceuticals. This review summarizes the aspects of protein glycosylation that are of interest to biotechnologists, namely, biosynthesis and biological relevance, as well as the tools to optimize and to analyze protein glycosylation.

Non-core region modulates interleukin-11 signaling activity: generation of agonist and antagonist variants

Human interleukin-11 (hIL-11) is a pleiotropic cytokine administered to patients with low platelet counts. From a structural point of view hIL-11 belongs to the long-helix cytokine superfamily, which is characterized by a conserved core motif consisting of four α-helices. We have investigated the region of hIL-11 that does not belong to the α-helical bundle motif, and that for the purpose of brevity we have termed "non-core region." The primary sequence of the interleukin was altered at various locations within the non-core region by introducing glycosylation sites. Functional consequences of these modifications were examined in cell-based as well as biophysical assays. Overall, the data indicated that the non-core region modulates the function of hIL-11 in two ways. First, the majority of muteins displayed enhanced cell-stimulatory properties (superagonist behavior) in a glycosylation-dependent manner, suggesting that the non-core region is biologically designed to limit the full potential of hIL-11. Second, specific modification of a predicted mini α-helix led to cytokine inactivation, demonstrating that this putative structural element belongs to site III engaging a second copy of cell-receptor gp130. These findings have unveiled new and unexpected elements modulating the biological activity of hIL-11, which may be exploited to develop more versatile medications based on this important cytokine.

Glycosylation of therapeutic proteins: an effective strategy to optimize efficacy

During their development and administration, protein-based drugs routinely display suboptimal therapeutic efficacies due to their poor physicochemical and pharmacological properties. These innate liabilities have driven the development of molecular strategies to improve the therapeutic behavior of protein drugs. Among the currently developed approaches, glycoengineering is one of the most promising, because it has been shown to simultaneously afford improvements in most of the parameters necessary for optimization of in vivo efficacy while allowing for targeting to the desired site of action. These include increased in vitro and in vivo molecular stability (due to reduced oxidation, cross-linking, pH-, chemical-, heating-, and freezing-induced unfolding/denaturation, precipitation, kinetic inactivation, and aggregation), as well as modulated pharmacodynamic responses (due to altered potencies from diminished in vitro enzymatic activities and altered receptor binding affinities) and improved pharmacokinetic profiles (due to altered absorption and distribution behaviors, longer circulation lifetimes, and decreased clearance rates). This article provides an account of the effects that glycosylation has on the therapeutic efficacy of protein drugs and describes the current understanding of the mechanisms by which glycosylation leads to such effects.

Effects of glycosylation on the stability of protein pharmaceuticals

In recent decades, protein-based therapeutics have substantially expanded the field of molecular pharmacology due to their outstanding potential for the treatment of disease. Unfortunately, protein pharmaceuticals display a series of intrinsic physical and chemical instability problems during their production, purification, storage, and delivery that can adversely impact their final therapeutic efficacies. This has prompted an intense search for generalized strategies to engineer the long-term stability of proteins during their pharmaceutical employment. Due to the well known effect that glycans have in increasing the overall stability of glycoproteins, rational manipulation of the glycosylation parameters through glycoengineering could become a promising approach to improve both the in vitro and in vivo stability of protein pharmaceuticals. The intent of this review is therefore to further the field of protein glycoengineering by increasing the general understanding of the mechanisms by which glycosylation improves the molecular stability of protein pharmaceuticals. This is achieved by presenting a survey of the different instabilities displayed by protein pharmaceuticals, by addressing which of these instabilities can be improved by glycosylation, and by discussing the possible mechanisms by which glycans induce these stabilization effects.

Pharmacologic rationale for early G-CSF prophylaxis in cancer patients and role of pharmacogenetics in treatment optimization

The use of recombinant human granulocyte colony stimulating factors (G-CSF) has become an integral part of supportive care during cytotoxic chemotherapy. Current guidelines recommend the use of G-CSF in patients with substantial risk of febrile neutropenia. However, little consensus exists about optimal timing and tailoring of this therapy. Based on the known effects of chemotherapy and G-CSF on bone marrow compartments, we propose a model that supports the prophylactic rather than therapeutic use of G-CSF therapy. In addition, several genetic alterations in G-CSF signalling pathway have been described. These genetic variants may predict the risk of febrile neutropenia and response to G-CSF. Thus, future pharmacogenetic/omics studies in this field are warranted. Through the identification of patients at risk and the knowledge of biological basis for optimal timing, hopefully we should soon be able to improve the application of the existing guidelines for G-CSF therapy and patient's prognosis.

Reduced dose of lenograstim is as efficacious as standard dose of filgrastim for peripheral blood stem cell mobilization and transplantation: a randomized study in patients undergoing autologous peripheral stem cell transplantation

In vitro studies have demonstrated a 27% increased efficacy of lenograstim over filgrastim. However, equal doses of 10 microg/kg/day of filgrastim and lenograstim have been recommended for mobilization of CD34+ cells without associated chemotherapy. In this study, we investigated whether a 25% reduced dose of lenograstim at 7.5 microg/kg/day is equavalent to 10 microg/kg/day filgrastim for autologous peripheral blood stem cell (PBSC) mobilization and transplantation. A total of 40 consecutive patients were randomized to either filgrastim (n = 20) or lenograstim (n = 20). The two cohorts were similar in regard to disease, sex, body weight, body surface area, conditioning regimens, previous chemotherapy cycles and radiotherapy. Each growth factor was administered for 4 consecutive days. The first PBSC apheresis was done on the 5th day. In the posttransplant period, the same G-CSF was given at 5 microg/kg/day until leukocyte engraftment. Successful mobilization was achieved in 95% of patients. Successful mobilization with the first apheresis, was achieved in 10/20 (50%) patients in the filgrastim group versus 9/20 (46%) patients in the lenograstim group. No significant difference was seen in the median number of CD34+cells mobilized, as well as the median number of apheresis, median volume of apheresis, percentage of CD34+ cells, and CD34+ cell number. Leukocyte and platelet engraftments, the number of days requiring G-CSF and parenteral antibiotics, the number of transfusions were similar in both groups in the posttransplant period. Lenograstim 7.5 microg/kg/day is as efficious as filgrastim 10 microg/kg/day for autologous PBSC mobilization and transplantation.

Choice of cellular protein expression system

Recombinant protein expression has become a standard laboratory tool, and a wide variety of systems and techniques are now in use. Because there are so many systems to choose from, the investigator has to be careful to use the combination that will give the best results for the protein being studied. This overview unit discusses expression and production choices, including post-translational modifications (e.g., glycosylation, acylation, sulfation, and removal of N-terminal methionine), in vivo and in vitro folding, and influence of downstream elements on expression.

Studying the formation of aggregates in recombinant human granulocyte-colony stimulating factor (rHuG-CSF), lenograstim, using size-exclusion chromatography and SDS-PAGE

The stability of proteins is a subject of intense current interest. Aggregation, as a dominant degradation pathway for therapeutic proteins, may cause multiple adverse effects, including loss of efficacy and immunogenicity. In the present study, the formation of aggregates in lenograstim under physiological conditions was monitored. For this purpose, a simple and selective size-exclusion high-performance liquid chromatography method for detection and separation of aggregates from intact protein was developed. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis was performed under reducing and non-reducing conditions to determine the nature of aggregate bond formation. Using both techniques, the presence of a low aggregate content attached via disulfide bonds was detected.

The function of the human interferon-beta 1a glycan determined in vivo

Recombinant human interferon-beta (rhIFN-beta) is the leading therapeutic intervention shown to change the cause of relapsing-remitting multiple sclerosis, and both a nonglycosylated and a significantly more active glycosylated variant of rhIFN-beta are used in treatment. This study investigates the function of the rhIFN-beta1a glycan moiety and its individual carbohydrate residues, using the myxovirus resistance (Mx) mRNA as a biomarker in Mx-congenic mice. We showed that the Mx mRNA level in blood leukocytes peaked 3 h after s.c. administration of rhIFN-beta1a. In addition, a clear dose-response relationship was confirmed, and the Mx response was shown to be receptor-mediated. Using specific glycosidases, different glycosylation analogs of rhIFN-beta1a were obtained, and their activities were determined. The glycosylated rhIFN-beta1a showed significantly higher activity than its deglycosylated counterpart, due to a protein stabilization/solubilization effect of the glycan. It is interesting to note that the terminating sialic acids were essential for these effects. Conclusively, the structure/bioactivity relationship of rhIFN-beta1a was determined in vivo, and it provided a novel insight into the role of the rhIFN-beta1a glycan and its carbohydrate residues. The possibilities of improving the pharmacological properties of rhIFN-beta1a using glycoengineering are discussed.

Human granulocyte colony stimulating factor (hG-CSF): cloning, overexpression, purification and characterization

Background

Biopharmaceutical drugs are mainly recombinant proteins produced by biotechnological tools. The patents of many biopharmaceuticals have expired, and biosimilars are thus currently being developed. Human granulocyte colony stimulating factor (hG-CSF) is a hematopoietic cytokine that acts on cells of the neutrophil lineage causing proliferation and differentiation of committed precursor cells and activation of mature neutrophils. Recombinant hG-CSF has been produced in genetically engineered Escherichia coli (Filgrastim) and successfully used to treat cancer patients suffering from chemotherapy-induced neutropenia. Filgrastim is a 175 amino acid protein, containing an extra N-terminal methionine, which is needed for expression in E. coli. Here we describe a simple and low-cost process that is amenable to scaling-up for the production and purification of homogeneous and active recombinant hG-CSF expressed in E. coli cells.

Results

Here we describe cloning of the human granulocyte colony-stimulating factor coding DNA sequence, protein expression in E. coli BL21(DE3) host cells in the absence of isopropyl-β-D-thiogalactopyranoside (IPTG) induction, efficient isolation and solubilization of inclusion bodies by a multi-step washing procedure, and a purification protocol using a single cationic exchange column. Characterization of homogeneous rhG-CSF by size exclusion and reverse phase chromatography showed similar yields to the standard. The immunoassay and N-terminal sequencing confirmed the identity of rhG-CSF. The biological activity assay, in vivo, showed an equivalent biological effect (109.4%) to the standard reference rhG-CSF. The homogeneous rhG-CSF protein yield was 3.2 mg of bioactive protein per liter of cell culture.

Conclusion

The recombinant protein expression in the absence of IPTG induction is advantageous since cost is reduced, and the protein purification protocol using a single chromatographic step should reduce cost even further for large scale production. The physicochemical, immunological and biological analyses showed that this protocol can be useful to develop therapeutic bioproducts. In summary, the combination of different experimental strategies presented here allowed an efficient and cost-effective protocol for rhG-CSF production. These data may be of interest to biopharmaceutical companies interested in developing biosimilars and healthcare community.

N-glycosylation of murine IFN-beta in a putative receptor-binding region

Human and mouse genomes contain more than 20 related genes encoding diverse type I interferons (IFNs- alpha/beta), cytokines that are crucial for resistance of organisms against viral infections. Although the amino acid sequences of various IFN-alpha/beta subtypes differ markedly, they are all considered to share a common three-dimensional structure and to bind the same heterodimeric receptor, composed of the IFNAR-1 and IFNAR-2 subunits. Analysis of available mammalian IFN-beta sequences showed that they all carry 1 to 5 predicted N-glycosylation sites. Murine IFN-beta contains three predicted N-glycosylation sites (Asn29, Asn69, Asn76), one of which (Asn29) is located in the AB loop, in a region predicted to interact with the type I IFN receptor. The aim of this work was to test if this site is indeed N-glycosylated and if this glycosylation would affect IFN antiviral activity. We showed that all three N-glycosylation sites predicted from the sequence, including Asn29, carry N-linked sugars. Mutation of individual N-glycosylation sites had a weak negative influence on IFN antiviral activity. In contrast, the complete loss of glycosylation dramatically decreased activity. Our data suggest that interaction of murine IFN-beta with the IFNAR could locally differ from that of human IFN-alpha2 and human IFN-beta.