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

A Poly-ADP-Ribose Polymer-GCSF Conjugate

Poly-ADP-ribose (PAR) is a naturally occurring form of polymers synthesized through enzymatic reactions catalyzed by poly(ADP-ribose) polymerases (PARPs). It is known for regulating various important cellular signaling pathways and processes. As a water soluble and biocompatible type of polymer, PAR may hold promise for safe and efficient delivery of therapeutics. To explore the therapeutic potential of PAR polymers, we herein generate PAR polymers conjugated with human granulocyte colony-stimulating factor (GCSF) protein by harnessing human PARP1-catalyzed auto-poly-ADP-ribosylation and a clickable analogue of nicotinamide adenine dinucleotide (NAD⁺). The resulting PAR polymer-based conjugate with multivalent GCSF ligands exhibits a potent cell proliferative activity. Notably, mice treated with a single dose of the PAR polymer-GCSF conjugate show sustained high levels of neutrophil in blood for 11 days, demonstrating excellent in vivo efficacy. Functionalized PAR polymers may provide new scaffolds for conjugating with therapeutic proteins or peptides toward improved pharmacological activities.

A new site-specific monoPEGylated β-lactoglobulin at the N-terminal: Effect of different molecular weights of mPEG on its conformation and antigenicity

A new method was investigated to decline the antigenicity of β-Lactoglobulin (β-LG) by site specifically conjugating β-LG at the N-terminus with 5 kDa and 10 kDa monomethoxy polyethylene glycol propyl aldehyde (mPEG-ALD). The optimal reaction conditions were molar ratio of 1:10 (β-LG:mPEG-ALD), reaction time for 16 h, and pH 5.0, and the content of mono-PEGylated β-LG was 51.3%. The results showed that mono-PEGylated β-LG with molecular mass of 23.2 kDa and 28.5 kDa. The peptide fragments of mPEG_5kDa-ALD-β-LG produced the same sequence pattern of β-LG except for the absence of one peptides f(1-14), indicating that α-amino group at the N-terminal was selectively modified. Furthermore, the conformation of modified β-LG underwent into slight change. The antigenicity of mPEG_5kDa-ALD-β-LG and mPEG_10kDa-ALD-β-LG decreased from 144.4 μg/mL to 66.7 and 39.0 μg/mL respectively. It was speculated that the steric hindrance effect of PEG was the main reason for the decline of antigenicity of β-LG.

Review transglutaminases: part II-industrial applications in food, biotechnology, textiles and leather products

Because of their protein cross-linking properties, transglutaminases are widely used in several industrial processes, including the food and pharmaceutical industries. Transglutaminases obtained from animal tissues and organs, the first sources of this enzyme, are being replaced by microbial sources, which are cheaper and easier to produce and purify. Since the discovery of microbial transglutaminase (mTGase), the enzyme has been produced for industrial applications by traditional fermentation process using the bacterium Streptomyces mobaraensis. Several studies have been carried out in this field to increase the enzyme industrial productivity. Researches on gene expression encoding transglutaminase biosynthesis were performed in Streptomyces lividans, Escherichia coli, Corynebacterium glutamicum, Yarrowia lipolytica, and Pichia pastoris. In the first part of this review, we presented an overview of the literature on the origins, types, mediated reactions, and general characterizations of these important enzymes, as well as the studies on recombinant microbial transglutaminases. In this second part, we focus on the application versatility of mTGase in three broad areas: food, pharmacological, and biotechnological industries. The use of mTGase is presented for several food groups, showing possibilities of applications and challenges to further improve the quality of the end-products. Some applications in the textile and leather industries are also reviewed, as well as special applications in the PEGylation reaction, in the production of antibody drug conjugates, and in regenerative medicine.

From Synthesis to Characterization of Site-Selective PEGylated Proteins

Covalent attachment of therapeutic proteins to polyethylene glycol (PEG) is widely used for the improvement of its pharmacokinetic and pharmacological properties, as well as the reduction in reactogenicity and related side effects. This technique named PEGylation has been successfully employed in several approved drugs to treat various diseases, even cancer. Some methods have been developed to obtain PEGylated proteins, both in multiple protein sites or in a selected amino acid residue. This review focuses mainly on traditional and novel examples of chemical and enzymatic methods for site-selective PEGylation, emphasizing in N-terminal PEGylation, that make it possible to obtain products with a high degree of homogeneity and preserve bioactivity. In addition, the main assay methods that can be applied for the characterization of PEGylated molecules in complex biological samples are also summarized in this paper.

Microbial transglutaminase for biotechnological and biomedical engineering

Research on bacterial transglutaminase dates back to 1989, when the enzyme has been isolated from Streptomyces mobaraensis. Initially discovered during an extensive screening campaign to reduce costs in food manufacturing, it quickly appeared as a robust and versatile tool for biotechnological and pharmaceutical applications due to its excellent activity and simple handling. While pioneering attempts to make use of its extraordinary cross-linking ability resulted in heterogeneous polymers, currently it is applied to site-specifically ligate diverse biomolecules yielding precisely modified hybrid constructs comprising two or more components. This review covers the extensive and rapidly growing field of microbial transglutaminase-mediated bioconjugation with the focus on pharmaceutical research. In addition, engineering of the enzyme by directed evolution and rational design is highlighted. Moreover, cumbersome drawbacks of this technique mainly caused by the enzyme's substrate indiscrimination are discussed as well as the ways to bypass these limitations.

Recent progress in enzymatic protein labelling techniques and their applications

Protein-based conjugates are valuable constructs for a variety of applications. Conjugation of proteins to fluorophores is commonly used to study their cellular localization and the protein-protein interactions. Modification of therapeutic proteins with either polymers or cytotoxic moieties greatly enhances their pharmacokinetics or potency. To label a protein of interest, conventional direct chemical reaction with the side-chains of native amino acids often yields heterogeneously modified products. This renders their characterization complicated, requires difficult separation steps and may impact protein function. Although modification can also be achieved via the insertion of unnatural amino acids bearing bioorthogonal functional groups, these methods can have lower protein expression yields, limiting large scale production. As a site-specific modification method, enzymatic protein labelling is highly efficient and robust under mild reaction conditions. Significant progress has been made over the last five years in modifying proteins using enzymatic methods for numerous applications, including the creation of clinically relevant conjugates with polymers, cytotoxins or imaging agents, fluorescent or affinity probes to study complex protein interaction networks, and protein-linked materials for biosensing. This review summarizes developments in enzymatic protein labelling over the last five years for a panel of ten enzymes, including sortase A, subtiligase, microbial transglutaminase, farnesyltransferase, N-myristoyltransferase, phosphopantetheinyl transferases, tubulin tyrosin ligase, lipoic acid ligase, biotin ligase and formylglycine generating enzyme.

Site-Specific Transglutaminase-Mediated Conjugation of Interferon α-2b at Glutamine or Lysine Residues

Interferon α (IFN α) subtypes are important protein drugs that have been used to treat infectious diseases and cancers. Here, we studied the reactivity of IFN α-2b to microbial transglutaminase (TGase) with the aim of obtaining a site-specific conjugation of this protein drug. Interestingly, TGase allowed the production of two monoderivatized isomers of IFN with high yields. Characterization by mass spectrometry of the two conjugates indicated that they are exclusively modified at the level of Gln101 if the protein is reacted in the presence of an amino-containing ligand (i.e., dansylcadaverine) or at the level of Lys164 if a glutamine-containing molecule is used (i.e., carbobenzoxy-l-glutaminyl-glycine, ZQG). We explained the extraordinary specificity of the TGase-mediated reaction on the basis of the conformational features of IFN. Indeed, among the 10 Lys and 12 Gln residues of the protein, only Gln101 and Lys164 are located in highly flexible protein regions. The TGase-mediated derivatization of IFN was then applied to the production of IFN derivatives conjugated to a 20 kDa polyethylene glycol (PEG), using PEG-NH₂ for Gln101 derivatization and PEG modified with ZQG for Lys164 derivatization. The two mono-PEGylated isomers of IFN were obtained in good yields, purified, and characterized in terms of protein conformation, antiviral activity, and pharmacokinetics. Both conjugates maintained a native-like secondary structure, as indicated by far-UV circular dichroism spectra. Importantly, they disclosed good in vitro antiviral activity retention (about only 1.6- to 1.8-fold lower than that of IFN) and half-lives longer (about 5-fold) than that of IFN after intravenous administration to rats. Overall, these results provide evidence that TGase can be used for the development of site-specific derivatives of IFN α-2b possessing interesting antiviral and pharmacokinetic properties.

The microbial transglutaminase immobilization on carboxylated poly(N-isopropylacrylamide) for thermo-responsivity

Microbial transglutaminase (mTG) is widely utilized in the PEGylation of pharmaceutical proteins. mTG immobilization can be achieved via covalent bonding on solid supports. However, the catalytic efficiency of mTG immobilized on solid supports was significantly reduced by mass transfer limitation. To overcome this limitation, mTG was covalently immobilized on the thermo-responsive carboxylated poly(N-isopropylacrylamide) (pNIPAM). The pNIPAM-mTG conjugate exhibited reversibly solubility in aqueous solution with a low critical solution temperature (LCST) at 39°C, i.e., it was insoluble above 39°C and soluble below 39°C. The pH dependence of the pNIPAM-mTG conjugate was similar with that of the native mTG. Upon conjugation to pNIPAM, the optimal temperature of mTG shifted down from 50-55°C to 40-45°C, and the thermal stability of the conjugate was elevated. The easy separation of the pNIPAM-mTG conjugate with its substrate and the catalytic efficiency of the pNIPAM-mTG conjugate were demonstrated by employing the pNIPAM-mTG conjugate to cross-link bovine serum albumin (BSA) and catalyze PEGylation of therapeutic protein, cytochrome c (Cyt C), respectively. The thermo-responsive mTG is suitable to modify proteins in food processing and biomedical engineering.

Monoconjugation of Human Amylin with Methylpolyethyleneglycol

Amylin is a pancreatic hormone cosecreted with insulin that exerts unique roles in metabolism and glucose homeostasis. The therapeutic restoration of postprandial and basal amylin levels is highly desirable in diabetes mellitus. Protein conjugation with the biocompatible polymer polyethylene glycol (PEG) has been shown to extend the biological effects of biopharmaceuticals. We have designed a PEGylated human amylin by using the aminoreactive compound methoxylpolyethylene glycol succinimidyl carbonate (mPEGsc). The synthesis in organic solvent resulted in high yields of monoPEGylated human amylin, which showed large stability against aggregation, an 8 times increase in half-life in vivo compared to the non-conjugated amylin, and pharmacological activity as shown by modulation of cAMP production in MCF–7 cell line, decrease in glucagon and modulation of glycemia following subcutaneous administration in mice. Altogether these data reveal the potential use of PEGylated human amylin for the restoration of fasting amylin levels.

High-level expression of a recombinant active microbial transglutaminase in Escherichia coli

Background

Bacterial transglutaminases are increasingly required as industrial reagents for in vitro modification of proteins in different fields such as in food processing as well as for enzymatic site-specific covalent conjugation of therapeutic proteins to polyethylene glycol to get derivatives with improved clinical performances.

In this work we studied the production in Escherichia coli of a recombinant transglutaminase from Streptomyces mobaraensis (microbial transglutaminase or MTGase) as enzymatically active chimeric forms using different expression systems under the control of both lac promoter or thermoinducible phage lambda promoter.

Results

Thermoinducible and constitutive expression vectors were constructed expressing Met-MTGase with chimeric LacZ_1-8PNP_1–20 or LacZ_1–8 fusion protein under different promoters. After transformed in competent Escherichia coli K12 strains were fermented in batch and fed-bach mode in different mediums in order to select the best conditions of expression.

The two most performing fusion protein systems namely short thermoinducible LacZ_1–8Met-MTGase from NP668/1 and long constitutive LacZ_1–8PNP_1–20Met-MTGase from NP650/1 has been chosen to compare both efficiency of expression and biochemical qualities of the product. Proteins were extracted, purified to homogeneity and verified as a single peak obtained in RP-HPLC. The LacZ_1–8PNP_1–20Met-MTGase fusion protein purified from NP650/1 exhibited an activity of 15 U/mg compared to 24 U/mg for the shorter fusion protein purified from NP668/1 cell strain.

Conclusions

Combining the experimental data on expression levels and specific activities of purified MTGase fusion proteins, the chimeric LacZ_1–8Met-MTGase, which displays an enzymatic activity comparable to the wild-type enzyme, was selected as a candidate for producing microbial transglutaminase for industrial applications.

Design Rationale and Development Approach for Pegfilgrastim as a Long-Acting Granulocyte Colony-Stimulating Factor

Filgrastim, a recombinant methionyl human granulocyte colony-stimulating factor (G-CSF) (r-metHuG-CSF), is efficacious in stimulating neutrophil production and maturation to prevent febrile neutropenia (FN) in response to chemotherapy. Because of its relatively short circulating half-life, daily filgrastim injections are required to stimulate neutrophil recovery. In an effort to develop a long-acting form of filgrastim that was as safe and efficacious as filgrastim but had a longer in vivo residence time, a number of strategies were considered. Ultimately, fusion of filgrastim to polyethylene glycol (PEG) was selected. Following extensive analysis of conjugation chemistries as well as in vitro and in vivo characterization of a panel of PEGylated proteins, a construct containing a 20 kDa PEG moiety covalently conjugated to the N-terminus of filgrastim was chosen for advancement as pegfilgrastim. Pegfilgrastim is primarily cleared by neutrophils and neutrophil precursors (rather than the kidneys), meaning that clearance from the circulation is self-regulating and pegfilgrastim is eliminated only after neutrophils start to recover. Importantly, addition of PEG did not alter the mechanism of action and safety profile compared to filgrastim. Clinical evaluation revealed that a single 6 mg dose effectively reduces the duration of neutropenia and risk of FN in patients receiving chemotherapy. This work demonstrates the benefit of using PEGylation to generate pegfilgrastim, which allows for once-per-chemotherapy cycle administration while maintaining similar safety and efficacy profiles as those for multiple daily administration of filgrastim. Approaches that may provide advances for therapeutic agonists of G-CSF receptor are also discussed.

Recent developments in protein and peptide parenteral delivery approaches

Discovery of insulin in the early 1900s initiated the research and development to improve the means of therapeutic protein delivery in patients. In the past decade, great emphasis has been placed on bringing protein and peptide therapeutics to market. Despite tremendous efforts, parenteral delivery still remains the major mode of administration for protein and peptide therapeutics. Other routes such as oral, nasal, pulmonary and buccal are considered more opportunistic rather than routine application. Improving biological half-life, stability and therapeutic efficacy is central to protein and peptide delivery. Several approaches have been tried in the past to improve protein and peptide in vitro/in vivo stability and performance. Approaches may be broadly categorized as chemical modification and colloidal delivery systems. In this review we have discussed various chemical approaches such as PEGylation, hyperglycosylation, mannosylation, and colloidal carriers including microparticles, nanoparticles, liposomes, carbon nanotubes and micelles for improving protein and peptide delivery. Recent developments on in situ thermosensitive gel-based protein and peptide delivery have also been described. This review summarizes recent developments on some currently existing approaches to improve stability, bioavailability and bioactivity of peptide and protein therapeutics following parenteral administration.

Preclinical and clinical phase I studies of a new recombinant Filgrastim (BK0023) in comparison with Neupogen®

Background

Filgrastim or methionyl-granulocyte colony-stimulating factor (Met-G-CSF), is a recombinant therapeutic protein widely used to treat severe neutropenia caused by myelosuppressive drugs in patients with nonmyeloid malignancies. In addition to its role in the regulation of granulopoiesis, treatment with G-CSF is considered the standard approach to mobilize CD34 positive (CD34⁺) mononuclear cells for reconstituting hemopoietic ability for bone marrow transplantation. An intended biosimilar filgrastim (coded BK0023) was produced in GMP conditions by E.coli fermentation according to an original recombinant process and showed physico-chemical properties and purity profile similar to Neupogen^®, a commercial preparation of filgrastim. The aim of the present study was to demonstrate the comparability of BK0023 to Neupogen^® in terms of both in vitro biological activities and in vivo toxicology, pharmacokinetics and pharmacodynamics.

Methods

Cell proliferation and radioligand binding assays were conducted in NFS-60 cells to compare the biological activity and functional interaction with the G-CSF receptor in vitro, while preclinical in vivo studies, including pharmacokinetics and pharmacodynamics after repeated dose were performed in normal and neutropenic rats. A phase I study was carried out in healthy male volunteers treated by multiple-dose subcutaneous administration of BK0023 and Neupogen^® to evaluate their pharmacodynamic effects as well as their pharmacokinetic and safety profile and to demonstrate their pharmacodynamic equivalence and pharmacokinetic bioequivalence.

Results

The results reported in this work demonstrate that BK0023 is comparable in terms of biological activity, efficacy and safety to Neupogen^®.

Conclusions

BK0023 has the same pharmacokinetic profile, efficacy and safety as the reference commercial filgrastim Neupogen^® and therefore could be further developed to become a convenient option to treat neutropenia in oncological patients.

Trial registration

Trial registration number (TRN): NCT01933971. Date of registration: Sept 6th 2013.

Preparation and characterization of PEGylated amylin

Amylin is a pancreatic hormone that plays important roles in overall metabolism and in glucose homeostasis. The therapeutic restoration of postprandial and basal amylin levels is highly desirable for patients with diabetes who need to avoid glucose excursions. Protein conjugation with polyethylene glycol (PEG) has long been known to be a convenient approach for extending the biological effects of biopharmaceuticals. We have investigated the reactivity of amylin with methoxy polyethylene glycol succinimidyl carbonate and methoxy polyethylene glycol succinimidyl propionate, which have an average molecular weight of 5 kDa. The reaction, which was conducted in both aqueous and organic (dimethyl sulfoxide) solvents, occurred within a few minutes and resulted in at least four detectable products with distinct kinetic phases. These results suggest a kinetic selectivity for PEGylation by succinimidyl derivatives; these derivatives exhibit enhanced reactivity with primary amine groups, as indicated by an evaluation of the remaining amino groups using fluorescamine. The analysis of tryptic fragments from mono- and diPEGylated amylin revealed that conjugation occurred within the 1-11 amino acid region, most likely at the two amine groups of Lys(1). The reaction products were efficiently separated by C-18 reversed phase chromatography. Binding assays confirmed the ability of mono- and diPEGylated amylin to interact with the amylin co-receptor receptor activity-modifying protein 2. Subcutaneous administration in mice revealed the effectiveness of monoPEG-amylin and diPEG-amylin in reducing glycemia; both compounds exhibited prolonged action compared to unmodified amylin. These features suggest the potential use of PEGylated amylin to restore basal amylin levels.

PEGylated drugs in rheumatology--why develop them and do they work?

Lack of efficacy and drug-related adverse effects are important reasons for the discontinuation of treatment in patients with rheumatic diseases. The development of new biologic therapies seeks to address these problems by specifically targeting the pathogenic mechanisms of disease. Most current biologics are proteins (particularly antibodies and enzymes) administered parenterally. It is important to optimize properties such as serum half-life, immunogenicity and solubility. Companies have thus begun to modify the drugs by conjugate chemistry, binding inert molecules such as polyethylene glycol (PEG) to biologic molecules to improve their pharmacodynamic properties. The use of PEG to alter these properties has to be weighed against the negative aspects of PEGylation, such as decreased activity and heterogeneity. This review focuses on the currently available PEGylated drugs used in rheumatological diseases, their efficacy, drawbacks and the current clinical trial evidence supporting their use.