Investigation on PEGylation strategy of recombinant human interleukin-1 receptor antagonist

Expression and characterization of recombinant IL-1Ra in Aspergillus oryzae as a system

BACKGROUND

The interleukin-1 receptor antagonist (IL-1Ra) is a crucial molecule that counteracts the effects of interleukin-1 (IL-1) by binding to its receptor. A high concentration of IL-1Ra is required for complete inhibition of IL-1 activity. However, the currently available Escherichia coli-expressed IL-1Ra (E. coli IL-1Ra, Anakinra) has a limited half-life. This study aims to produce a cost-effective, functional IL-1Ra on an industrial scale by expressing it in the pyrG auxotroph Aspergillus oryzae.

RESULTS

We purified A. oryzae-expressed IL-1Ra (Asp. IL-1Ra) using ion exchange and size exclusion chromatography (53 mg/L). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that Asp. IL-1Ra is N-glycosylated and approximately 17 kDa in size. We conducted a comparative study of the bioactivity, binding kinetics, and half-life between Asp. IL-1Ra and E. coli IL-1Ra. Asp. IL-1Ra showed good bioactivity even at a low concentration of 0.5 nM. The in vitro half-life of Asp. IL-1Ra was determined for different time points (0, 24, 48, 72, and 96 h) and showed higher stability than E. coli IL-1Ra, despite exhibiting a 100-fold lower binding affinity (2 nM).

CONCLUSION

This study reports the production of a functional Asp. IL-1Ra with advantageous stability, without extensive downstream processing. To our knowledge, this is the first report of a recombinant functional and stable IL-1Ra expressed in A. oryzae. Our results suggest that Asp. IL-1Ra has potential for industrial-scale production as a cost-effective alternative to E. coli IL-1Ra.

Sustained intra-cartilage delivery of interleukin-1 receptor antagonist using cationic peptide and protein-based carriers

OBJECTIVE

Blocking the interleukin-1 (IL-1) catabolic cascade following joint trauma can be achieved using its receptor antagonist, IL-1Ra. However, its clinical translation for osteoarthritis therapy has been unsuccessful due to its rapid joint clearance and lack of targeting and penetration into deep cartilage layers at therapeutic concentrations. Here, we target the high negative charge of cartilage aggrecan-glycosaminoglycans (GAGs) by attaching cationic carriers to IL-1Ra. IL-1Ra was conjugated to the cartilage targeting glycoprotein, Avidin, and a short length optimally charged cationic peptide carrier (CPC+14). It is hypothesized that electro-diffusive transport and binding properties of IL-1Ra-Avidin and IL-1Ra-CPC+14 will create intra-cartilage depots of IL-1Ra, resulting in long-term suppression of IL-1 catabolism with only a single administration.

DESIGN

IL-1Ra was conjugated to Avidin or CPC+14 using site specific maleimide linkers, and confirmed using gel electrophoresis, high-performance liquid chromatography (HPLC), and mass spectrometry. Intra-cartilage transport and retention of conjugates was compared with native IL-1Ra. Attenuation of IL-1 catabolic signaling with one-time dose of IL-1Ra-CPC+14 and IL-1Ra-Avidin was assessed over 16 days using IL-1α challenged bovine cartilage and compared with unmodified IL-1Ra.

RESULTS

Positively charged IL-1Ra penetrated through the full-thickness of cartilage, creating a drug depot. A single dose of unmodified IL-1Ra was not sufficient to attenuate IL-1-induced cartilage deterioration over 16 days. However, when delivered using Avidin, and to a greater extent CPC+14, IL-1Ra significantly suppressed cytokine induced GAG loss and nitrite release while improving cell metabolism and viability.

CONCLUSION

Charge-based cartilage targeting drug delivery systems hold promise as they can enable long-term therapeutic benefit with only a single dose.

Polyglycerol for Half-Life Extension of Proteins-Alternative to PEGylation?

Since several decades, PEGylation is known to be the clinical standard to enhance pharmacokinetics of biotherapeutics. In this study, we introduce polyglycerol (PG) of different lengths and architectures (linear and hyperbranched) as an alternative polymer platform to poly(ethylene glycol) (PEG) for half-life extension (HLE). We designed site-selective N-terminally modified PG-protein conjugates of the therapeutic protein anakinra (IL-1ra, Kineret) and compared them systematically with PEG analogues of similar molecular weights. Linear PG and PEG conjugates showed comparable hydrodynamic sizes and retained their secondary structure, whereas binding affinity to IL-1 receptor 1 decreased with increasing polymer length, yet remained in the low nanomolar range for all conjugates. The terminal half-life of a 40 kDa linear PG-modified anakinra was extended 4-fold compared to the unmodified protein, close to its PEG analogue. Our results demonstrate similar performances of PEG- and PG-anakinra conjugates and therefore highlight the outstanding potential of polyglycerol as a PEG alternative for half-life extension of biotherapeutics.

Six flavonoids inhibit the antigenicity of β-lactoglobulin by noncovalent interactions: A spectroscopic and molecular docking study

It is practical to inhibit the allergenicity of β-lactoglobulin (β-LG) using natural products acting via noncovalent interactions; however, the mechanism of the effect has not been investigated in detail. Herein, the comprehensive noncovalent mechanism of inhibition of the antigenicity of β-LG by six flavonoids (kaempferol, myricetin, phloretin, epigallocatechin-3-gallate (EGCG), naringenin, and quercetin) was investigated by spectroscopic and molecular docking methods. Our results indicate that six flavonoids reduced the antigenicity of β-LG in the following order: EGCG > phloretin > naringenin > myricetin > kaempferol > quercetin, with antigenic inhibition rates of 72.6%, 68.4%, 59.7%, 52.3%, 51.4% and 40.8%, respectively. Six flavonoids induced distinct conformational changes in β-LG, which were closely associated with a decline in antigenicity of β-LG. The flavonoids bound to specific antigen epitopes in the β-sheet and β-turn of β-LG to induce a decrease in the antigenicity of the protein.

Injectable biomaterials for delivery of interleukin-1 receptor antagonist: Toward improving its therapeutic effect

Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory cytokine that inhibits IL-1 activity and has been proposed to treat a wide variety of systemic and local inflammatory pathologies for multiple decades. However, the short half-life and high concentration required to inhibit IL-1 activity has limited its use in clinical applications. Many strategies have been developed with the goal of improving the therapeutic efficacy of IL-1Ra for a variety of pathologies, including fusing IL-1Ra to protein/peptide/polymer partners, releasing IL-1Ra from injectable polymer or mineral particles, and release of IL-1Ra from injectable coacervates and gels. This literature review examines injectable biomaterials engineered to improve IL-1Ra delivery, both locally and systemically, to increase its efficacy and ease of use in clinic. STATEMENT OF SIGNIFICANCE: Interleukin-1 receptor antagonist (IL-1Ra) is a therapeutic protein with the potential to treat numerous inflammatory conditions and diseases. However, its short biological half-life and high therapeutic concentration may limit its utility in all but a few clinical scenarios. In this review, we present the biomaterial based delivery strategies which have been explored to deliver IL-1Ra to improve its efficacy and applicability to treat inflammation.

Self-Assembled Raspberry-Like Core/Satellite Nanoparticles for Anti-Inflammatory Protein Delivery

Functional proteins are very promising for protein therapeutics; however, effective delivery of therapeutic proteins remains challenging. Herein, we developed novel core/satellite nanoparticles by tethering therapeutic proteins to the core/shell polymeric particle surface through cucurbit[8]uril (CB[8])-mediated host-guest interactions. The effectiveness of the core/satellite nanoparticles as protein carrier was demonstrated through the intra-articular delivery of interleukin-1 receptor antagonist (IL-1Ra). We showed that IL-1Ra can effectively self-assemble onto the surface of the polymeric nanoparticles and maintained good protein bioactivity by inhibiting IL-1-mediated signaling. More importantly, in vivo results revealed that IL-1Ra-bounded core/satellite nanoparticles could significantly increase the retention time of IL-1Ra in the rat stifle joint compared to soluble IL-1Ra, which could greatly improve the efficacy of IL-1Ra. These results indicate that the facile host-guest self-assembly can be exploited as an effective approach for realizing the therapeutic potential of proteins.

Synthesis of self-assembled IL-1Ra-presenting nanoparticles for the treatment of osteoarthritis

Osteoarthritis is a progressive joint disease that results in degradation of cartilage in load-bearing joints. Pain and inflammation in the joint are the hallmarks of this condition, which further exacerbate the cartilage destruction and health of the patient. It is hence imperative to treat the joint inflammation at the earliest. Interleukin 1 (IL-1) blockade by IL-1 receptor antagonist (IL-1Ra) has shown promise in the clinic but this therapy suffers from rapid clearance, high doses, and frequent intervention. Use of carrier particles that result in longer residence time has been proposed. Here we have synthesized a new class of nanoparticles presenting IL-1Ra on the surface and with tunable size from 300 to 700 nm. These IL-1Ra-poly(2-hydroxyethyl methacrylate)-pyridine nanoparticles are cytocompatible and stable in serum-containing solutions for several days. Our results further demonstrate that these nanoparticles are capable of blocking IL-1β signaling in an NF-κB inducible reporter cell line. These engineered nanoparticles are promising for localized intra-articular delivery in joint space to reduce inflammation in osteoarthritis and other inflammatory diseases. © 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 595-599, 2016.

Specific therapy to regulate inflammation in rheumatoid arthritis: molecular aspects

Rheumatoid arthritis (RA) is a chronic inflammatory disease in which persistent inflammation of synovial tissue results in a progressive functional decline of the joint and premature mortality. TNF inhibitors were the first biological disease-modifying antirheumatic drugs (DMARDs) used to treat RA. Since then, new biological drugs have emerged, such as inhibitors of IL-1, IL-6 and others, with different mechanisms of action that include the depletion of B cells and the inhibition of T-cell costimulation. Recently, RA treatments have incorporated the use of synthetic DMARDs. This review describes the molecular aspects of the mechanisms of action of biological and synthetic DMARDs, discusses the adverse effects and limitations of established therapies and analyses the alternative approaches to RA treatment.

Head to head comparison of the formulation and stability of concentrated solutions of HESylated versus PEGylated anakinra

Although PEGylation of biologics is currently the gold standard for half-life extension, the technology has a number of limitations, most importantly the non-biodegradability of PEG and the extremely high viscosity at high concentrations. HESylation is a promising alternative based on coupling to the biodegradable polymer hydroxyethyl starch (HES). In this study, we are comparing HESylation with PEGylation regarding the effect on the protein's physicochemical properties, as well as on formulation at high concentrations, where protein stability and viscosity can be compromised. For this purpose, the model protein anakinra is coupled to HES or PEG by reductive amination. Results show that coupling of HES or PEG had practically no effect on the protein's secondary structure, and that it reduced protein affinity by one order of magnitude, with HESylated anakinra more affine than the PEGylated protein. The viscosity of HESylated anakinra at protein concentrations up to 75 mg/mL was approximately 40% lower than that of PEG-anakinra. Both conjugates increased the apparent melting temperature of anakinra in concentrated solutions. Finally, HESylated anakinra was superior to PEG-anakinra regarding monomer recovery after 8 weeks of storage at 40°C. These results show that HESylating anakinra offers formulation advantages compared with PEGylation, especially for concentrated protein solutions.

IL-1Ra and its delivery strategies: inserting the association in perspective

Interleukin-1 receptor antagonist (IL-1Ra) is a naturally occurring anti-inflammatory antagonist of interleukin-1 family of pro-inflammatory cytokines. The broad spectrum anti-inflammatory effects of IL-1Ra have been investigated against various auto-immune diseases such as diabetes mellitus, rheumatoid arthritis. Despite of its outstanding broad spectrum anti-inflammatory effects, IL-1Ra has short biological half-life (4-6 h) and to cope with this problem, up till now, many delivery strategies have been applied either to extend the half-life and/or prolong the steady-state sustained release of IL-1Ra from its target site. Here in our present paper, we have provided an overview of all approaches attempted to prolong the duration of therapeutic effects of IL-1Ra either by fusing IL-1Ra using fusion protein technology to extend the half-life and/or development of new dosage forms using various biodegradable polymers to prolong its steady-state sustained release at the site of administration. These approaches have been characterized by their intended impact on either in vitro release characteristics and/or pharmacokinetic and pharmacodynamic parameters of IL-1Ra. We have also compared these delivery strategies with each other on the basis of bioactivity of IL-1Ra after fusion with fusion protein partner and/or encapsulation with biodegradable polymer.

Site-specific PEGylation of therapeutic proteins via optimization of both accessible reactive amino acid residues and PEG derivatives

Modification of accessible amino acid residues with poly(ethylene glycol) [PEG] is a widely used technique for formulating therapeutic proteins. In practice, site-specific PEGylation of all selected/engineered accessible nonessential reactive residues of therapeutic proteins with common activated PEG derivatives is a promising strategy to concomitantly improve pharmacokinetics, allow retention of activity, alleviate immunogenicity, and avoid modification isomers. Specifically, through molecular engineering of a therapeutic protein, accessible essential residues reactive to an activated PEG derivative are substituted with unreactive residues provided that protein activity is retained, and a limited number of accessible nonessential reactive residues with optimized distributions are selected/introduced. Subsequently, all accessible nonessential reactive residues are completely PEGylated with the activated PEG derivative in great excess. Branched PEG derivatives containing new PEG chains with negligible metabolic toxicity are more desirable for site-specific PEGylation. Accordingly, for the successful formulation of therapeutic proteins, optimization of the number and distributions of accessible nonessential reactive residues via molecular engineering can be integrated with the design of large-sized PEG derivatives to achieve site-specific PEGylation of all selected/engineered accessible reactive residues.

Covalent conjugation of poly(ethylene glycol) to proteins and peptides: strategies and methods

PEGylation, the covalent linking of PEG chains, has become the leading drug delivery approach for proteins. This technique initiated its first steps almost 40 years ago, and since then, a variety of methods and strategies for protein-polymer coupling have been devised. PEGylation can give a number of relevant advantages to the conjugated protein, such as an important in vivo half-life prolongation, a reduction or an abolishment of immunogenicity, and a reduction of aggregation. Furthermore, the technique has demonstrated a great degree of versatility and efficacy--not only PEG-protein conjugates have reached the commercial marketplace (with nine types of derivatives), but a PEG-aptamer and PEGylated liposomes are now also available. Most of this success is due to the development of several PEGylation strategies and to the large selection of PEGylating agents presently at hand for researchers. Nevertheless, this technique still requires a certain level of familiarity and knowledge in order to achieve a positive outcome for a PEGylation project. To draw general guidelines for conducting PEGylation studies is not always easy or even possible because such experiments often require case-by-case optimization. On the other hand, several common methods can be used as starting examples for the development of tailor-made coupling conditions. Therefore, this chapter aims to provide a basic introduction to a wide range of PEGylation procedures for those researchers who may not be familiar with this field.

In vivo anti-tumor activity of polypeptide HM-3 modified by different polyethylene glycols (PEG)

HM-3, designed by our laboratory, is a polypeptide composed of 18 amino acids. Pharmacodynamic studies in vivo and in vitro indicated that HM-3 could inhibit endothelial cell migration and angiogenesis, thereby inhibiting tumor growth. However, the half-life of HM-3 is short. In this study, we modified HM-3 with different polyethylene glycols (PEG) in order to reduce the plasma clearance rate, extend the half-life in the body, maintain a high concentration of HM-3 in the blood and increase the therapeutic efficiency. HM-3 was modified with four different types of PEG with different molecular weights (ALD-mPEG_5k, ALD-mPEG_10k, SC-mPEG_10k and SC-mPEG_20k), resulting in four modified products (ALD-mPEG_5k-HM-3, ALD-mPEG_10k-HM-3, SC-mPEG_10k-HM-3 and SC-mPEG_20k-HM-3, respectively). Anti-tumor activity of these four modified HM-3 was determined in BALB/c mice with Taxol as a positive control and normal saline as a negative control. Tumor weight inhibition rates of mice treated with Taxol, HM-3, ALD-mPEG_5k-HM-3, ALD-mPEG_10k-HM-3, SC-mPEG_10k-HM-3 and SC-mPEG_20k-HM-3 were 44.50%, 43.92%, 37.95%, 31.64%, 20.27% and 50.23%, respectively. Tumor inhibition rates in the Taxol, HM-3 and SC-mPEG_20k-HM-3 groups were significantly higher than that in the negative control group. The efficiency of tumor inhibition in the SC-mPEG_20k-HM-3 group (drug treatment frequency: once per two days) was better than that in the HM-3 group (drug treatment frequency: twice per day). In addition, tumor inhibition rate in the SC-mPEG_20k-HM-3 group was higher than that in the taxol group. We conclude that SC-mPEG_20k-HM-3 had a low plasma clearance rate and long half-life, resulting in high anti-tumor therapeutic efficacy in vivo. Therefore, SC-mPEG_20k-HM-3 could be potentially developed as new anti-tumor drugs.

Structural investigation of PEG-fibrinogen conjugates

Controllable bio-synthetic polymeric hydrogels made from fibrinogen-poly(ethylene glycol) adducts have been successfully employed in tissue engineering. The structural consequences of PEG conjugation to fibrinogen (i.e., PEGylation) in such a hydrogel network are not fully understood. The current investigation details the structural alterations caused to the reduced fibrinogen polypeptides by the covalent attachment of linear or branched PEG chains. The structure of PEGylated fibrinogen polypeptides were comprehensively characterized using small angle X-ray scattering, light scattering, and cryo-transmission electron microscopy. These characterizations concur that the bio-synthetic hybrids self-assemble into elongated objects, having a protein core of about 50 A in diameter decorated with multiple PEG chains. Conjugates with branched PEG chains were shorter, and have lower average molecular weight compared to conjugates with linear chains. The diameter of the protein core of both samples was similar, suggesting a tail-to-head aggregation of the PEGylated fibrinogen polypeptide. A more complete understanding of this unique structural arrangement can provide further insight into the full extent of biofunctional accessibility in a biomaterial that combines the advantages of synthetic polymers with bioactive proteins.

Enhanced circulation half-life of site-specific PEGylated rhG-CSF: optimization of PEG molecular weight

Recombinant human granulocyte colony stimulating factor (rhG-CSF) and its PEGylated product "mono-PEG20-GCSF" have already been widely used for treatment of all kinds of neutropenia. However, the high required dosage of mono-PEG20-GCSF made it relatively expensive in clinical use. We postulated that an N-terminal site-specific PEGylated rhG-CSF with higher PEG Mw (PEG30 kDa) might be able to achieve longer circulation half-life while retaining its bioactivity, allowing the reduction of dosage for clinical use. rhG-CSF was PEGylated at the N-terminus by 5 kDa, 10 kDa, 20 kDa and 30 kDa methoxy-poly(ethylene glycol)-propionaldehyde (mPEG-ALD), and the four PEGylates were compared with respect to reaction, separation, characterization and also in vivo/in vitro activity, results showed that the mPEG-ALD of higher Mw demonstrated better N-terminal site-specific selectivity, separation purity and yield. The production cost and in vitro activity of mono-PEG30-GCSF and mono-PEG20-GCSF were almost the same, while mono-PEG30-GCSF showed longer in vivo circulation half-life and 60% higher drug bioavailability than mono-PEG20-GCSF. Consequently, mono-PEG30-GCSF shall be administered at a lower dosage than mono-PEG20-GCSF while retaining the same therapeutic efficacy.

Current status and challenges of cytokine pharmacology

The major concern of pharmacology about cytokines has originated from plentiful data showing association between gross changes in their production and pathophysiological processes. Despite the enigmatic role of cytokines in diseases, a number of them have become a subject of cytokine and anti-cytokine immunotherapies. Production of cytokines can be influenced by many endogenous and exogenous stimuli including drugs. Cells of the immune system, such as macrophages and lymphocytes, are richly endowed with receptors for the mediators of physiological functions, such as biogenic amines, adenosine, prostanoids, steroids, etc. Drugs, agonists or antagonists of these receptors can directly or indirectly up- and down-regulate secretion of cytokines and expression of cytokine receptors. Vice versa, cytokines interfere with drug pharmacokinetics and pharmacodynamics through the interactions with cytochrome P450 and multiple drug resistance proteins. The aim of the review is to encourage more intensive studies in these fields of cytokine pharmacology. It also outlines major areas of searching promising candidates for immunotherapeutic interventions.

Anti-inflammatory polymeric coatings for implantable biomaterials and devices

Synthetic polymer coatings are used extensively in modern medical devices and implants because of their material versatility and processability. These coatings are designed for specific applications by controlling composition and physical and chemical properties, and they can be formed into a variety of complex structures and shapes. However, implantation of these materials into the body elicits a strong inflammatory host response that significantly limits the integration and biological performance of devices. Biomaterial-mediated inflammation is a complex reaction involving protein adsorption, leukocyte recruitment and activation, secretion of inflammatory mediators, and fibrous encapsulation of the implant. Significant research efforts have focused on modifying material properties using various anti-inflammatory polymeric surface coatings to generate more biocompatible implants. This minireview provides a brief background on the events of biomaterial-mediated inflammation and highlights various approaches used for modifying material surfaces to modulate inflammatory responses. These include both passive and active strategies, such as nonfouling surface treatments and delivery of anti-inflammatory agents, respectively. Novel approaches will be needed to extend the in vivo lifetime and performance of devices and reduce the need for multiple implantation surgeries.