Polyethylene glycol-conjugated pharmaceutical proteins

Environmental concerns on water-soluble and biodegradable plastics and their applications - A review

Water-soluble polymers are materials rapidly growing in volume and in number of materials and applications. Examples include synthetic plastics such as polyacrylamide, polyacrylic acid, polyethylene glycol, polyethylene oxide and polyvinyl alcohol, with applications ranging from cosmetics and paints to water purification, pharmaceutics and food packaging. Despite their abundance, their environmental concerns (e.g., bioaccumulation, toxicity, and persistence) are still not sufficiently assessed, especially since water soluble plastics are often not biodegradable, due to their chemical structure. This review aims to overview the most important water-soluble and biodegradable polymers, their applications, and their environmental impact. Degradation products from water-insoluble polymers designed for biodegradation can also be water soluble. Most water-soluble plastics are not immediately harmful for humans and the environment, but the degradation products are sometimes more hazardous, e.g. for polyacrylamide. An increased use of water-soluble plastics could also introduce unanticipated environmental hazards. Therefore, excessive use of water-soluble plastics in applications where they can enter the environment should be discouraged. Often the plastics can be omitted or replaced by natural polymers with lower risks. It is recommended to include non-biodegradable water-soluble plastics in regulations for microplastics, to make risk assessments for different water-soluble plastics and to develop labels for flushable materials.

Influence of Heat Treatment of Nitinol Wire on the Properties of Nitinol/Hybrid Layer for Ibuprofen Release

The efficiency of drug delivery from coatings of metallic implants is one of the key factors. The influence of chemical and thermal treatments of nitinol wire on the corrosion properties, deposition of hydroxyapatite(HA)/poly ε-caprolactone-polyethylene glycol (PEG-b-PCL), and the amount of ibuprofen released from that bilayer were studied. The hydroxyapatite layer was electrodeposited by pulse current, while the PEG-b-PCL layer was by drop-coating. It was shown that nitinol wire, chemically treated and thermally heated at 470 °C under optimized conditions, is the most optimal substrate for the deposition of uniform and compact hybrid HA/(PEG-b-PCL) bilayer. Ibuprofen incorporated into this hybrid bilayer exhibits the maximum release into phosphate-buffered saline (PBS) solution. About 80% of ibuprofen is released within 5 h.

Synthesis, physicochemical characterization, and investigation of anti-inflammatory activity of water-soluble PEGylated 1,2,4-Triazoles

A series of water-soluble PEGylated 1,2,4-triazoles 5-8 were successfully synthesized from methyl 5-(chloromethyl)-1-aryl-1H-1,2,4-triazole-3-carboxylates 1. All of the water-soluble PEGylated 1,2,4-triazoles were characterized by FT-IR and 1H NMR spectroscopy. The solubility, in vitro plasma stability, and anti-inflammatory activity were also determined and compared to original methyl 5-(halomethyl)-1-aryl-1H-1,2,4-triazole-3-carboxylates. For SAR study, all PEGylated 1,2,4-triazoles 5-8 performed potential anti-inflammatory activity on LPS-induced RAW 264.7 cells (IC50 = 3.42-7.81 μM). Moreover, the western blot result showed PEGylated 1,2,4-triazole 7d performed 5.43 and 2.37 folds inhibitory activity over iNOS and COX-2 expressions. On the other hand, the cell viability study revealed PEGylated 1,2,4-triazoles 7 and 8 with PEG molecular weight more than 600 presented better cell safety (cell viability > 95 %). Through the solubility and in vitro plasma stability studies, PEGylated 1,2,4-triazoles 7a-d exhibited higher hydrophilicity and prolonged 2.01 folds of half-life in compound 7d. Furthermore, the in vivo anti-inflammatory and gastric safety results indicated PEGylated 1,2,4-triazole 7d more effectively decreased the inflammatory response in edema and COX-2 expression and exhibited higher gastric safety than Indomethacin. Following the in vitro and in vivo study results, PEGylated 1,2,4-triazole 7d possessed favorable solubility, plasma stability features, safety, and significant anti-inflammatory activity to become the potential water-soluble anti-inflammatory candidate.

Effect of Mini-PEGs Modification on the Enzymatic Digestion of D-Amino Acid-Containing Peptides under the Action of PROK

It was previously reported that D-amino acid-containing peptides exhibited the ability to resist enzymatic hydrolysis. This study investigated the influence of mini-PEGs modification on enzymatic hydrolysis ability of D-amino acid-containing peptides. The results showed that PEGylation promoted enzymatic hydrolysis of the D-amino acid-containing peptide, especially, the cleavage rate of the D-amino acid-containing peptide 6-w with PEG₃ modification at the N-ends was up to 17 times higher in the presence of proteinase K (PROK) compared to those without PEG₃ modification. Moreover, analysis of the enzymatic cleavage sites demonstrated a similar cleavage pattern of the PEGylated D-amino acid-containing peptide to that of the unmodified peptide. The computational simulations further showed that the enhanced enzymatic hydrolysis ability can be attributed to the strong interaction between PROK and the peptide after PEG₃ modification and the resulting formation of a mature catalytic triad structure.

Transitioning to Pegylated Interferon for the Treatment of Cutaneous T-Cell Lymphoma: Meeting the Challenge of Therapy Discontinuation and a Proposed Algorithm

Cutaneous T-cell lymphoma (CTCL) is an uncommon non-Hodgkin lymphoma characterized by skin involvement, with the most recognized subtypes being mycosis fungoides (MF) and Sezary syndrome (SS). Interferon has been an established treatment for MF/SS since 1984 and is integrated into management guidelines internationally. In 2019, manufacturers abruptly discontinued interferon-α2b and interferon-α2a. Many alternative systemic therapies in MF/SS remain unfunded or unavailable in Canada, presenting a unique challenge. Although off-label use of pegylated interferon is a logical substitute, there are no established dosing guidelines and limited published experience. This case series provides a single-center experience on pegylated interferon-α2b for treatment of MF/SS, a suggested management algorithm, and a review of the literature. All patients identified in the Calgary Cutaneous Lymphoma Program with stage IIB–IVB MF/SS treated with interferon-α2b (4.5–9 MU/week) were switched to once weekly pegylated interferon (90 μg, 0.5 mL) between February and July 2021. Response was monitored using the mSWAT and SkinDex-29 tools. Eight patients were switched to pegylated interferon, with a median disease duration of 69 months (range: 8–275 months). Five out of eight patients remain on pegylated interferon, with the remainder having switched to preplanned therapies. Two patients required dose reduction due to side effects, including grade II anemia and mood changes. The remaining patients had normal laboratory investigations and no additional side effects. Uncommon lymphomas like MF/SS have limited treatment options, and the impact of abrupt product discontinuation is substantial. We propose a management algorithm for the transition of patients from interferon to pegylated interferon.

Distinctive Formation of PEG-Lipid Nanopatches onto Solid Polymer Surfaces Interfacing Solvents from Atomistic Simulation

The interface between solid poly(lactic acid-co-glycolic acid), PLGA, and solvents is described by large-scale atomistic simulations for water, ethyl acetate, and the mixture of them at ambient conditions. Interactions at the interface are dominated by Coulomb forces for water and become overwhelmingly dispersive for the other two solvents. This effect drives a neat liquid-phase separation of the mixed solvent, with ethyl acetate covering the PLGA surface and water being segregated away from it. We explore with all-atom Molecular Dynamics the formation of macromolecular assemblies on the surface of the PLGA-solvent interface when DSPE-PEG, 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-(polyethylene glycol)_n amine, is added to the solvent. By following in time the deposition of the DSPE-PEG macromolecules onto the PLGA surface, the mechanism of how nanopatches remain adsorbed to the surface despite the presence of the solvent is probed. These patches have a droplet-like aspect when formed at the PLGA-water interface that flatten in the PLGA-ethyl acetate interface case. Dispersive forces are dominant for the nanopatch adhesion to the surface, while electrostatic forces are dominant for keeping the solvent around the new formations. Considering the droplet-like patches as wetting the PLGA surface, we predict an effective wetting behavior at the water interface that fades significantly at the ethyl acetate interface. The predicted mechanism of PEG-lipid nanopatch formation may be generally applicable for tailoring the synthesis of asymmetric PLGA nanoparticles for specific drug delivery conditions.

Overview of polyethylene glycol-based materials with a special focus on core-shell particles for drug delivery application

Polyethylene glycols (PEG) are water-soluble nonionic polymeric molecules. PEG and PEG-based materials are used for various important applications such as solvents, adhesives, adsorbents, drug delivery agents, tissue engineering scaffolds, etc. The coating of nanoparticles with PEG forms core-shell nanoparticles. The PEG-based core-shell nanoparticles are synthesized for the development of high-quality drug delivery systems. In the present review, we first explained the basics and various applications of PEGs and PEG-based composites materials and then concentrated on the PEG-based core-shell nanoparticles for biomedical applications specifically their use in drug delivery.

Physiological and Pathological Factors Affecting Drug Delivery to the Brain by Nanoparticles

The prevalence of neurological/neurodegenerative diseases, such as Alzheimer's disease is known to be increasing due to an aging population and is anticipated to further grow in the decades ahead. The treatment of brain diseases is challenging partly due to the inaccessibility of therapeutic agents to the brain. An increasingly important observation is that the physiology of the brain alters during many brain diseases, and aging adds even more to the complexity of the disease. There is a notion that the permeability of the blood-brain barrier (BBB) increases with aging or disease, however, the body has a defense mechanism that still retains the separation of the brain from harmful chemicals in the blood. This makes drug delivery to the diseased brain, even more challenging and complex task. Here, the physiological changes to the diseased brain and aged brain are covered in the context of drug delivery to the brain using nanoparticles. Also, recent and novel approaches are discussed for the delivery of therapeutic agents to the diseased brain using nanoparticle based or magnetic resonance imaging guided systems. Furthermore, the complement activation, toxicity, and immunogenicity of brain targeting nanoparticles as well as novel in vitro BBB models are discussed.

Comparing the efficacy and side-effects of PDLASTA® (Pegfilgrastim) with PDGRASTIM® (Filgrastim) in breast cancer patients: a non-inferiority randomized clinical trial

BACKGROUND

The objective of this study was to compare the efficacy and side effects of a single dose (Pegfilgrastim or PDL) or repeated six daily injections (Filgrastim or PDG) during chemotherapy courses in breast cancer patients in a non-inferiority clinical trial.

METHODS

In this randomized clinical trial, 80 patients were recruited and allocated randomly to two equal arms. In one group, a single subcutaneous dose of PDL was injected the day after receiving the chemotherapy regimen in each cycle. The second arm received a subcutaneous injection of PDG for six consecutive days in each cycle of treatment. The side effects of GCF treatment and its effect on blood parameters were compared in each cycle and during eight cycles of chemotherapy.

RESULTS

Hematologic parameters showed no significant differences in any of the treatment courses between the two study groups. The comparison of WBC (p = 0.527), Hgb (p = 0.075), Platelet (p = 0.819), Neutrophil (p = 0.575), Lymphocyte (p = 705) and ANC (p = 0.675) changes during the eight courses of treatment also revealed no statistically significant difference between the two study groups. Side effects including headache, injection site reaction and muscle pain had a lower frequency in patients receiving PDL drugs.

CONCLUSION

It seems that PDL is non-inferior in efficacy and also less toxic than PDG. Since PDL can be administered in a single dose and is also less costly, it can be regarded as a cost-effective drug for the treatment of chemotherapy-induced neutropenia.

TRIAL REGISTRATION

IRCT20190504043465N1 , May 2019.

MUC1-Targeted Radiopharmaceuticals in Cancer Imaging and Therapy

Mucin 1 (MUC1) is a large, transmembrane mucin glycoprotein overexpressed in most adenocarcinomas and plays an important role in tumor progression. Regarding its cellular distribution, biochemical features, and function, tumor-related MUC1 varies from the MUC1 expressed in normal cells. Therefore, targeting MUC1 for cancer immunotherapy and imaging can exploit the difference between cancerous and normal cells. Radiopharmaceuticals have a potential use as carriers for the delivery of radionuclides to tumors for a diagnostic imaging and radiotherapy. Several radiolabeled targeting molecules like peptides, antibodies, and aptamers have been efficiently demonstrated in detecting and treating cancer by targeting MUC1. This review provides a brief overview of the current status of developments and applications of MUC1-targeted radiopharmaceuticals in cancer imaging and therapy.

Clinical Relevance of Pre-Existing and Treatment-Induced Anti-Poly(Ethylene Glycol) Antibodies

Abstract

Poly(ethylene glycol) (PEG) is a nontoxic, hydrophilic polymer that is often covalently attached to proteins, drugs, tissues, or materials; a procedure commonly referred to as PEGylation. PEGylation improves solubility, circulation time, and reduces immunogenicity of therapeutic molecules. Currently, there are 21 PEGylated drugs approved by the Food and Drug Administration (FDA), and more in the developmental stage. In addition to the polymer's applications in the clinic, PEG is widely used as a solvent and emulsifying agent in the formulation of cosmetics, cleaning, and personal care products. Due to the ubiquitous presence of the polymer in everyday products, patients can develop antibodies against PEG (αPEG Abs) that can be problematic when a PEGylated drug is administered. These αPEG Abs can provoke hypersensitivity reactions, accelerated drug clearance, and decreased therapeutic efficacy. Herein, we review how the prevalence of PEG in everyday products has induced αPEG Abs within the general public as well as the effect of these Abs on the performance of PEGylated therapeutics. We will focus on clinical manifestations following the administration of PEGylated drugs.

Lay Summary

Poly(ethylene glycol) (PEG) is a polymer found in products including cosmetics, personal care products, cleaning agents, medicine, and food. Due to the prevalence of PEG, people can develop antibodies (αPEG Abs) against the polymer, which recognize PEG as foreign. Of note, PEG is frequently incorporated into drug formulations to improve therapeutic efficacy. Complications can arise when a patient receiving a PEGylated drug has previously developed αPEG Abs from interactions with PEG in everyday products. The presence of high concentrations of αPEG Abs in blood can result in decreased treatment efficacy and allergic reactions to a wide range of therapeutics.

20 kDa PEGylated Adrenomedullin as a New Therapeutic Candidate for Inflammatory Bowel Disease

Human adrenomedullin (AM), a hypotensive peptide, also has anti-colitis activity. We prepared a polyethylene glycol (PEG) ylated form of AM through the conjugation of PEG-AM (1–15) and AM (15–52). Highly pure monomeric 20 kDa PEG-AM (20kPEG-AM) stimulated cyclic adenosine monophosphate production in HEK-293 cells stably expressing the type 1 AM receptor in a dose-dependent manner. The half-life of 20kPEG-AM was 7.4 h following subcutaneous administration in mice. We assessed the anti-colitis effect of subcutaneous 20kPEG-AM administration in the dextran sodium sulfate murine colitis model. Single and double subcutaneous injection of 20kPEG-AM significantly reduced total inflammation scores. These results suggest that 20kPEG-AM is a promising therapeutic candidate for the treatment of human inflammatory bowel diseases.

PEGYLATION: an important approach for novel drug delivery system

PEGylation is the covalent addition of PEG to one more molecule. PEGylation can improve the maintenance time of the therapeutics similar to proteins, liposomes, and nanoparticle through shielding them beside different debasing mechanisms dynamic in a body that improve beneficial properties. This skill is used to get better half-life and other pharmaceutical properties of a protein, peptide, or non-peptide molecule. Polyethylene glycol is harmless, non-immunogenic, non-antigenic, and extremely soluble in water and FDA accepted polymer. It shows a significant role in drug delivery. A variety of PEG-based formulations are available in the market. This paper represents the benefits of PEGylation over non-PEGylated products. Now a day, PEGylation plays an important role in the drug delivery system. PEGylation increases the therapeutic potential of drugs.

Perspectives, Tendencies, and Guidelines in Affinity-Based Strategies for the Recovery and Purification of PEGylated Proteins

In recent years, the effective purification of PEGylated therapeutic proteins from reaction media has received particular attention. Although several techniques have been used, affinity-based strategies have been scarcely explored despite the fact that, after PEGylation, marked changes in the molecular affinity parameters of the modified molecules are observed. With this in mind, future contributions in the bioseparation of these polymer-protein conjugates are expected to exploit affinity in chromatographic and nonchromatographic techniques which will surely derive in the integration of different operations. However, this will only occur as novel ligands which are simultaneously found. As it will be mentioned, these novel ligands may be screened or designed. In both cases, computer-aided tools will support their identification or development. Additionally, ligand discovery by high-throughput screening (HTS) is believed to become a fast, economic, and informative technology that will aid in the mass production of ligands along with genetic engineering and related technologies. Therefore, besides analyzing the state of the art in affinity separation strategies for PEGylated molecules, this review proposes a basic guideline for the selection of adequate ligands to provide information and prospective on the future of affinity operations in solving this particular bioengineering problem.

Polyethylene Glycol Acts as a Mechanistic Stabilizer of L-asparaginase: A Computational Probing

BACKGROUND

L-asparaginase (L-ASN) is an anti-cancer enzyme therapeutic drug that exerts cytotoxicity via inhibition of protein synthesis through depletion of L-asparagine in the tumor microenvironment. The therapeutic performance of the native drug is partial due to the associated instability, reduced half-life and immunogenic complications.

OBJECTIVE

In this study, we attempted the modification of recombinant L-asparaginase with PEG and an integrated computational strategy to probe the PEGylation in the protein to understand the biological stability/activity imparted by PEG.

METHODS

In vitro PEGylation of recombinant L-ASN was carried out and further evaluated in silico.

RESULTS

PEGylation enhanced thermal and pH activities with extended serum half-life and resistance to proteases compared to the native enzyme. The molecular dynamics analysis revealed intricate interactions required in the coupling of PEG to L-asparaginase to bestow stronger binding affinity of L-asparagine moiety towards L-asparaginase. PEG-asparagine complex ensured stable conformation over both the native protein and asparagine-protein complex thus elucidating the PEG-induced stable conformation in the protein. PEG mechanistically stabilized L-asparaginase through inducing pocket modification at the receptor to adapt to the cavity.

CONCLUSION

The study provides the rationale of PEGylation in imparting the stability towards Lasparaginase which would expand the potential application of L-asparaginase enzyme for the effective treatment of cancer.

Hyaluronic Acid-Antibody Fragment Bioconjugates for Extended Ocular Pharmacokinetics

Treatment of ocular diseases associated with neovascularization currently requires frequent intravitreal injections of antivascular endothelial growth factor (anti-VEGF) therapies. Reducing the required frequency of anti-VEGF injections and associated clinical visits may improve patient adherence to the prescribed treatment regimen and improve outcomes. Herein, we explore conjugation of rabbit and fragment antibodies (Fab) to the biopolymer hyaluronic acid (HA) as a half-life modifying strategy, and assess the impact on Fab biophysical properties and vitreal pharmacokinetics. HA-Fab conjugates of three distinct molecular weights and hydrodynamic radii (R_H) were assessed for in vivo pharmacokinetic performance relative to unconjugated Fab after intravitreal injection in rabbits. Covalent conjugation to HA did not significantly alter the thermal stability or secondary or tertiary structure, or diminish the potency of the Fab, thereby preserving its pharmacological properties. Conjugation to HA did significantly slow the in vivo clearance of Fab from the rabbit vitreous in an R_H-dependent manner. Compared to free Fab (observed vitreal half-life of 2.8 days), HA-Fab conjugates cleared with observed half-lives of 7.6, 10.2, and 18.3 days for 40 kDa, 200 kDa, and 600 kDa HA conjugates, respectively. This work elucidates a possible strategy for long-acting delivery of proteins intended for the treatment of chronic posterior ocular diseases.

Site-specific PEGylation of micro-plasmin for improved thrombolytic therapy through engineering enhanced resistance against serpin mediated inhibition

The relatively rapid inhibition of microplasmin by α₂-AP leads to short functional half-life of the molecule in vivo, causing inefficient clot dissolution, even after site-specific, local catheter-based delivery. Here, we describe a PEGylation approach for improving the therapeutic potential via improving the survival of microplasmin in presence of its cognate inhibitor, α₂-AP, wherein a series of strategically designed cysteine analogs of micro-plasminogen were prepared and expressed in E. coli, and further modified by covalent grafting in vitro with PEG groups of different molecular sizes so as to select single or double PEG chains that increase the molecular weight and hydrodynamic radii of the conjugates, but with a minimal discernible effect on intrinsic plasmin activity and structural framework, as explored by amidolytic activity and CD-spectroscopy, respectively. Interestingly, some of the purified PEG-coupled proteins after conversion to their corresponding proteolytically active forms were found to exhibit significantly reduced inhibition rates (up to 2-fold) by α₂-AP relative to that observed with wild-type microplasmin. These results indicate an interesting, and not often observed, effect of PEG groups through reduced/altered dynamics between protease and inhibitor, likely through a steric hindrance mechanism. Thus, the present study successfully identifies single- and double-site PEGylated muteins of microplasmin with significantly enhanced functional half-life through enhanced resistance to inactivation by its in vivo plasma inhibitor. Such an increased survival of bioactivity in situ, holds unmistakable potential for therapeutic exploitation, especially in ischemic strokes where a direct, catheter-based deposition within the cranium has been shown to be promising, but is currently limited by the very short in vivo bioactive half-life of the fibrin dissolving agent/s.

Macroporous Polymer⁻Protein Hybrid Materials for Antibody Purification by Combination of Reactive Gelation and Click-Chemistry

Clickable core-shell nanoparticles based on poly(styrene-co-divinylbenzene-co-vinylbenzylazide) have been synthesized via emulsion polymerization. The 38 nm sized particles have been swollen by divinyl benzene (DVB) and 2,2'-azobis(2-methylpropionitrile) (AIBN) and subsequently processed under high shear rates in a Z-shaped microchannel giving macroporous microclusters (100 µm), through the reactive gelation process. The obtained clusters were post-functionalized by "click-chemistry" with propargyl-PEG-NHS-ester and propargylglicidyl ether, yielding epoxide or NHS-ester activated polymer supports for bioconjugation. Macroporous affinity materials for antibody capturing were produced by immobilizing recombinant Staphylococcus aureus protein A on the polymeric support. Coupling chemistry exploiting thiol-epoxide ring-opening reactions with cysteine-containing protein A revealed up to three times higher binding capacities compared to the protein without cysteine. Despite the lower binding capacities compared to commercial affinity phases, the produced polymer-protein hybrids can serve as stationary phases for immunoglobulin affinity chromatography as the materials revealed superior intra-particle mass transports.

Development and validation of analytical methodologies for the quantification of PCK3145 and PEG-PCK3145 in mice

PCK3145 is an anti-metastatic synthetic peptide against prostate cancer. The objective of the study is to develop and validate novel and sensitive methods for the determination of PCK3145 and Pegylated PCK3145 in mouse plasma. An LC-MS/MS method was developed and validated for the determination of PCK3145 giving high sensitivity and linearity in the range of 0.125-4.0 μg/mL. PCK3145 characterised by short half-life, therefore, it was conjugated with the poly ethylene glycol (PEG). However, LC-MS/MS has been more difficult to apply for the quantitative analysis of PEGylated peptides due to the large size. A UHPLC-UV method was developed and validated for the determination of PEG-PCK3145, with linearity of 0.05-2.0 mg/mL. In order to further improve the sensitivity for the detection of PEG-PCK3145, an indirect ELISA method was used. It was found that this method was capable of detecting PCK3145 through the quantification of PEG with excellent sensitivity found at 0.132 ng/mL. The in vitro proteolytic stability of PCK3145 and PEG-PCK3145 in mouse plasma and whole blood was studied by LC-MS/MS and UHPLC, respectively. The LC-MS/MS and ELISA methods can be applied for monitoring levels of PCK3145 in mouse plasma for in vivo pharmacokinetic and bioavailability animal studies.

Biocompatible Porous Polyester-Ether Hydrogel Scaffolds with Cross-Linker Mediated Biodegradation and Mechanical Properties for Tissue Augmentation

Porous polyester-ether hydrogel scaffolds (PEHs) were fabricated using acid chloride/alcohol chemistry and a salt templating approach. The PEHs were produced from readily available and cheap commercial reagents via the reaction of hydroxyl terminated poly(ethylene glycol) (PEG) derivatives with sebacoyl, succinyl, or trimesoyl chloride to afford ester cross-links between the PEG chains. Through variation of the acid chloride cross-linkers used in the synthesis and the incorporation of a hydrophobic modifier (poly(caprolactone) (PCL)), it was possible to tune the degradation rates and mechanical properties of the resulting hydrogels. Several of the hydrogel formulations displayed exceptional mechanical properties, remaining elastic without fracture at compressive strains of up to 80%, whilst still displaying degradation over a period of weeks to months. A subcutaneous rat model was used to study the scaffolds in vivo and revealed that the PEHs were infiltrated with well vascularised tissue within two weeks and had undergone significant degradation in 16 weeks without any signs of toxicity. Histological evaluation for immune responses revealed that the PEHs incite only a minor inflammatory response that is reduced over 16 weeks with no evidence of adverse effects.

Enhanced MRI T 2 Relaxivity in Contrast-Probed Anchor-Free PEGylated Iron Oxide Nanoparticles

Superparamagnetic iron oxide nanoparticles (SPIONs, ~11-nm cores) were PEGylated without anchoring groups and studied as efficient MRI T 2 contrast agents (CAs). The ether group of PEG is efficiently and directly linked to the positively charged surface of SPIONs, and mediated through a dipole-cation covalent interaction. Anchor-free PEG-SPIONs exhibit a spin-spin relaxivity of 123 ± 6 mM-1s-1, which is higher than those of PEG-SPIONs anchored with intermediate biomolecules, iron oxide nanoworms, or Feridex. They do not induce a toxic response for Fe concentrations below 2.5 mM, as tested on four different cell lines with and without an external magnetic field. Magnetic resonance phantom imaging studies show that anchor-free PEG-SPIONs produce a significant contrast in the range of 0.1-0.4 [Fe] mM. Our findings reveal that the PEG molecules attached to the cores immobilize water molecules in large regions of ~85 nm, which would lead to blood half-life of a few tens of minutes. This piece of research represents a step forward in the development of next-generation CAs for nascent-stage cancer detection. Contrast-probed anchor-free PEGylated iron oxide contrast agent.

HM10660A, a long-acting hIFN-α-2b, is a potent candidate for the treatment of hepatitis C through an enhanced biological half-life

Interferon-α (IFN-α) has been widely used for the treatment of infections due to the hepatitis C virus (HCV). Because of the short half-life of IFN-α in serum, it must be administered three times per week. To increase the half-life of IFN-α, the immunoglobulin G4 (IgG4) Fc fragment (HMC001) was conjugated with human IFN-α-2b to develop a long-acting IFN-α-2b, HM10660A. An analysis of the antiviral efficacy of HM10660A in a human hepatocyte-engrafted mouse model found that HM10660A reduced serum HCV titers more effectively than a commercially available peginterferon α-2a (PEGASYS^®) and IFN-α-2b. Pharmacokinetic (PK) and pharmacodynamic (PD) studies of HM10660A using monkeys demonstrated that the half-life of HM10660A was approximately 2-fold longer than commercially available peginterferon α-2a, which is approved for a once-weekly regimen. Moreover, the IFN-mediated induction profiles of neopterin and 2', 5'-oligoadenylate synthase (OAS) in normal cynomolgus monkeys indicated that HM10660A had enhanced antiviral activity and a prolonged duration of action compared with peginterferon α-2a. Considering the improved PK and PD properties, HM10660A can most likely be dosed every two or four weeks, providing superior antiviral efficacy and convenience for patients with HCV.

Recombinant and chemo-/bio-orthogonal synthesis of liposomal thrombomodulin and its antithrombotic activity

Thrombomodulin (TM) is an endothelial cell membrane protein that acts as a major cofactor in the protein C anticoagulant pathway. The EGF-like domains 4-6 of TM (TM₄₅₆) are essential for PC activation. In this study, we proposed a liposomal recombinant TM conjugate to mimic the membrane TM structure and its anticoagulant activity. First, a DSPE-PEG₂₀₀₀-TM₄₅₆ was successfully synthesized by site-specific conjugation of azido-TM₄₅₆ with DSPE-PEG₂₀₀₀-DBCO via copper-free click chemistry quantitatively. Then, liposome-TM₄₅₆ was fabricated via direct liposome formation with the DSPE-PEG₂₀₀₀-TM₄₅₆ and other lipids. This liposomal formulation of TM₄₅₆ retained protein C activation activity as that of TM₄₅₆. Also, liposome-TM₄₅₆ was much more stable and had a longer plasma half-life than TM₄₅₆ and DSPE-PEG₂₀₀₀-TM₄₅₆, respectively. Moreover, liposome-TM₄₅₆ showed in vivo anticoagulant effect by decreasing the mortality from 80% to 20% in a thrombin-induced thromboembolism mouse model. The reported liposome-TM₄₅₆ conjugate mimics the endothelial TM anticoagulation activity and may serve as an effective anticoagulant agent candidate for future development.

Perspectives on dendritic architectures and their biological applications: From core to cell

The challenges of medicine today include the increasing stipulation for sensitive and effective systems that can improve the pathological responses with a simultaneous reduction in accumulation and drug side effects. The demand can be fulfilled through the advancements in nanomedicine that includes nanostructures and nanodevices for diagnosing, treating, and prevention of various diseases. In this respect, the nanoscience provides various novel techniques with carriers such as micelles, dendrimers, particles and vesicles for the transportation of active moieties. Further, an efficient way to improve these systems is through stimuli a responsive system that utilizes supramolecular hyperbranched structures to meet the above criteria. The stimuli-responsive dendritic architectures exhibit spatial, temporal, convenient, effective, safety and controlled drug release in response to specific trigger through electrostatic interactions plus π stacking. The stimuli-responsive systems are capable of sequestering the drug molecules underneath a predefined set of conditions and discharge them in a different environment through either exogenous or endogenous stimulus. The incorporation of photoresponsive moieties at various components of dendrimer such as core, branches or at the peripheral end exaggerates its significance in various allied fields of nanotechnology which includes sensors, photoswitch, electronic widgets and in drug delivery systems. This is due to the light instigated geometrical modifications at the core or at the surface molecules which generates huge conformational changes throughout the hyperbranched structure. Further, numerous synthetic methodologies have been investigated for utilization of dendrimers in therapeutic drug delivery and its applicability towards stimuli responsive systems such as photo-instigated, thermal-instigated, and pH-instigated hyperbranched structures and their advancement in the field of nanomedicine. This paper highlights the fascinating theoretical advances and principal mechanisms of dendrimer synthesis and their ability to capture light that strengthens its applicability from radiant energy to medical photonics.

PEG-PCL-based nanomedicines: A biodegradable drug delivery system and its application

The lack of efficient therapeutic options for many severe disorders including cancer spurs demand for improved drug delivery technologies. Nanoscale drug delivery systems based on poly(ethylene glycol)-poly(ε-caprolactone) copolymers (PEG-PCL) represent a strategy to implement therapies with enhanced drug accumulation at the site of action and decreased off-target effects. In this review, we discuss state-of-the-art nanomedicines based on PEG-PCL that have been investigated in a preclinical setting. We summarize the various synthesis routes and different preparation methods used for the production of PEG-PCL nanoparticles. Additionally, we review physico-chemical properties including biodegradability, biocompatibility, and drug loading. Finally, we highlight recent therapeutic applications investigated in vitro and in vivo using advanced systems such as triggered release, multi-component therapies, theranostics, or gene delivery systems.

PEGylation of Biopharmaceuticals: A Review of Chemistry and Nonclinical Safety Information of Approved Drugs

Modification of biopharmaceutical molecules by covalent conjugation of polyethylene glycol (PEG) molecules is known to enhance pharmacologic and pharmaceutical properties of proteins and other large molecules and has been used successfully in 12 approved drugs. Both linear and branched-chain PEG reagents with molecular sizes of up to 40 kDa have been used with a variety of different PEG derivatives with different linker chemistries. This review describes the properties of PEG itself, the history and evolution of PEGylation chemistry, and provides examples of PEGylated drugs with an established medical history. A trend toward the use of complex PEG architectures and larger PEG polymers, but with very pure and well-characterized PEG reagents is described. Nonclinical toxicology findings related to PEG in approved PEGylated biopharmaceuticals are summarized. The effect attributed to the PEG part of the molecules as observed in 5 of the 12 marketed products was cellular vacuolation seen microscopically mainly in phagocytic cells which is likely related to their biological function to absorb and remove particles and macromolecules from blood and tissues. Experience with marketed PEGylated products indicates that adverse effects in toxicology studies are usually related to the active part of the drug but not to the PEG moiety.

PEGylation of a High-Affinity Anti-(+)Methamphetamine Single Chain Antibody Fragment Extends Functional Half-Life by Reducing Clearance

PURPOSE

Methamphetamine (METH) abuse is a worldwide drug problem, yet no FDA-approved pharmacological treatments are available for METH abuse. Therefore, we produced an anti-METH single chain antibody fragment (scFv7F9Cys) as a pharmacological treatment for METH abuse. ScFv's have a short half-life due to their small size, limiting their clinical use. Thus, we examined the pharmacokinetic effects of conjugating poly(ethylene) glycol (-PEG) to scFv7F9Cys to extend its functional half-life.

METHODS

The affinity of scFv7F9Cys and PEG conjugates to METH was determined in vitro via equilibrium dialysis saturation binding. Pharmacokinetic and parameters of scFv7F9Cys and scFv7F9Cys-PEG20K (30 mg/kg i.v. each) and their ability to bind METH in vivo were determined in male Sprague-Dawley rats receiving a subcutaneous infusion of METH (3.2 mg/kg/day).

RESULTS

Of three PEGylated conjugates, scFv7F9Cys-PEG20K was determined the most viable therapeutic candidate. PEGylation of scFv7F9Cys did not alter METH binding functionality in vitro, and produced a 27-fold increase in the in vivo half-life of the antibody fragment. Furthermore, total METH serum concentrations increased following scFv7F9Cys or scFv7F9Cys-PEG20K administration, with scFv7F9Cys-PEG20K producing significantly longer changes in METH distribution than scFv7F9Cys.

CONCLUSIONS

PEGylation of scFv7F9Cys significantly increase the functional half-life of scFv7F9Cys, suggesting it may be a long-lasting pharmacological treatment option for METH abuse.

PEGylated PAMAM dendrimers: Enhancing efficacy and mitigating toxicity for effective anticancer drug and gene delivery

Poly(amidoamine) dendrimers (PAMAM) are well-defined, highly branched, nanoscale macromolecules with numerous active amine groups on the surface. PAMAM dendrimer can enhance the solubility of hydrophobic drugs, and with numerous reactive groups on the surface PAMAM dendrimer can be engineered with various functional groups for specific targeting ability. However, in physiological conditions, these amine groups are toxic to cells and limit the application of PAMAM. In the recent years, polyethylene glycol (PEG) conjugation has been the most widely used approach to reduce the toxicity of the active group on dendrimer surface. PEG molecules are known to be inert, non-immunogenic, and non-antigenic with a significant water solubility. PEGylated PAMAM-mediated delivery could not only overcome the limitations of dendrimer such as drug leakage, immunogenicity, hemolytic toxicity, systemic cytotoxicity but they also have the ability to enhance the solubilization of hydrophobic drugs and facilitates the potential for DNA transfection, siRNA delivery and tumor targeting. This review focuses on the recent developments on the application and influence of PEGylation on various biopharmaceutical properties of PAMAM dendrimers.

STATEMENT OF SIGNIFICANCE

It is well established that dendrimers have demonstrated promising potentials for drug delivery. However, the inherent toxicity poses challenges for its clinical translation. In this regard, PEGylation has helped mitigate some of the toxicity concerns of dendrimers and have paved the way forward for testing its translational potentials. The review is a collection of articles demonstrating the utility of PEGylation of the most studied PAMAM dendrimers. To our knowledge, this is a first such attempt to draw reader's attention, specifically, towards PEGylated PAMAM dendrimers.

Delivery of Doxorubicin from Biodegradable PEG Hydrogels Having Schiff Base Linkages†

In our quest to develop new drug delivery systems, we designed and synthesized PEG-conjugates and PEG-hydrogels with a degradable linkage to the drug. Specifically, methoxyPEG-doxorubicin (MPEG-CH=N-Doxo) and doxorubicin-PEG aldehyde (OHC-PEG-CH=N-Doxo) conjugates, plus poly (vinyl amine)-PEG-doxorubicin (PVAm-PEG-Doxo) hydrogels were prepared. The hydrogels were crosslinked by PEG-Schiff base linkages, and the Doxo was conjugated to the gel by pendant Schiff base bonds (PVAm-N=CH-PEG-CH=N-Doxo). The release profile of Doxo from the hydrogels was dependent on pH and on the ratio of PVAm to the PEG-dialdehyde crosslinker. These degradable PEG hydrogels could be good candidates for slow release of Doxo from subcutaneous or IM implants.

Erythrocyte-mediated delivery of recombinant enzymes

The possibility to clone, express and purify recombinant enzymes have originated the opportunity to dispose of a virtually infinite array of proteins that could be used in the clinics to treat several inherited and acquired pathological conditions. However, the direct administration of these recombinant proteins faces some intrinsic difficulties, such as degradation by circulating proteases and/or inactivation by the patient immune system. The use of drug delivery systems may overcome these limitations. Concerning recombinant enzyme therapy, the present review will mainly focus on the exploitation of erythrocytes as a carrier system for enzymes removing potentially noxious metabolites from the circulation, either as limiting treatment strategy for auxotrophic tumours or as a detoxing approach for some intoxication type inherited metabolic disorders. Moreover, the possibility of using RBCs as a potential delivering system addressing the enzymes to the monocyte-macrophages of reticular endothelial system for the treatment of diseases associated with this cell lineage, e.g. lysosome storage diseases, will be briefly discussed.

Analysis of heterogeneity in nonspecific PEGylation reactions of biomolecules

The compositional heterogeneity associated with polymer conjugation reactions of biomolecules is analyzed for the particular case of nonspecific PEGylation reactions. It is shown that the distribution of the number of PEG moieties grafted to biomolecules such as proteins is a binomial-type function of two parameters-the reaction efficiency as well as the number of binding sites per biomolecule. The nature of this distribution implies that uniform compositions are favored for increasing number of coupling sites per biomolecule as well as for increasing efficiency of the modification process. Therefore, the binomial distribution provides a rationale for the pronounced heterogeneity that is observed for PEGylated small enzyme systems even at high coupling efficiencies. For the particular case of PEGylated trypsin it is shown that the heterogeneity results in a broad distribution of deactivation times that is captured by a stretched exponential decay model. The presented analysis is expected to apply to general modification processes of compounds in which partial functionalization of a fixed number of reactive sites is achieved by means of a nonspecific coupling reaction.

A sensitive WST-8-based bioassay for PEGylated granulocyte colony stimulating factor using the NFS-60 cell line

CONTEXT

Granulocyte colony stimulating factor (G-CSF) has been commonly used to treat neutropenia caused by chemotherapy, radiotherapy, and organ transplants. Improved in vitro efficacy of G-CSF has already been observed by conjugating it to polyethylene glycol (PEG).

OBJECTIVE

The in vivo bioassay using tetrazolium dye with the NFS-60 cell line has been recommended for G-CSF but no such monographs are available for PEGylated G-CSF in pharmacopeias. In the present study, the assay recommended for G-CSF was evaluated for its suitability to PEGylated G-CSF.

MATERIALS AND METHODS

The generally used MTS [3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium]-based assay was compared with a bioassay employing a water-soluble tetrazolium dye, WST-8 [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium], using NFS-60 cells at a concentration of 7 × 10(5) cells/ml against 800 IU/ml of PEGylated G-CSF at 24, 48, 72, and 72 h time points to determine the efficacy of PEGylated G-CSF. Further, the optimized WST-8 dye-based assay was used to test the potency of various commercially available PEGylated G-CSF preparations.

RESULTS

The results demonstrated enhanced sensitivity of the WST-8-based assay over the conventional MTS-based assay for determining the potency of PEGylated G-CSF using the NFS-60 cell line.

CONCLUSION

Our study demonstrates the potential application of WST-8-based bioassays for other biotherapeutic proteins of human and veterinary interest.

A novel leptin antagonist peptide inhibits breast cancer growth in vitro and in vivo

The role of the obesity cytokine leptin in breast cancer progression has raised interest in interfering with leptin's actions as a valuable therapeutic strategy. Leptin interacts with its receptor through three different binding sites: I–III. Site I is crucial for the formation of an active leptin–leptin receptor complex and in its subsequent activation. Amino acids 39-42 (Leu-Asp-Phe-Ile- LDFI) were shown to contribute to leptin binding site I and their mutations in alanine resulted in muteins acting as typical antagonists. We synthesized a small peptide based on the wild-type sequence of leptin binding site I (LDFI) and evaluated its efficacy in antagonizing leptin actions in breast cancer using in vitro and in vivo experimental models. The peptide LDFI abolished the leptin-induced anchorage-dependent and -independent growth as well as the migration of ERα-positive (MCF-7) and -negative (SKBR3) breast cancer cells. These results were well correlated with a reduction in the phosphorylation levels of leptin downstream effectors, as JAK2/STAT3/AKT/MAPK. Importantly, the peptide LDFI reversed the leptin-mediated up-regulation of its gene expression, as an additional mechanism able to enhance the peptide antagonistic activity. The described effects were specific for leptin signalling, since the developed peptide was not able to antagonize the other growth factors' actions on signalling activation, proliferation and migration. Finally, we showed that the LDFI pegylated peptide markedly reduced breast tumour growth in xenograft models. The unmodified peptide LDFI acting as a full leptin antagonist could become an attractive option for breast cancer treatment, especially in obese women.

Conjugation of PolyPEG to interferon alpha extends serum half-life while maintaining low viscosity of the conjugate

The covalent attachment of poly(ethylene glycol) (PEG) to therapeutic proteins is a commonly used approach for extending in vivo half-lives. A potential limitation of this PEGylation strategy is the adverse effect of PEG on conjugate viscosity. Interferon-alpha (IFN) was conjugated via its N-terminal amino group by reductive amination to α-aldehyde functional comb-shaped PolyPEG polymers (50 and 70 kDa) and to linear PEG (30 kDa). In vitro potencies of the purified PEGylated IFN conjugates were measured by reporter gene assay using a HEK293P/ISRE-SEAP cell line. IFN levels were measured in rats following intravenous injection. Viscosities of various linear PEG and PolyPEG polymers along with the polymer-IFN conjugates were determined using a rotational rheometer with cone-and-plate geometry. In vitro potencies and half-lives of the PEGylated IFN conjugates were compared with those of the marketed branched PEG-IFN conjugate PEGASYS. Both PolyPEG-IFN conjugates retained a similar potency as that of the marketed comparator, whereas the linear PEG-IFN conjugate potency was greater. All conjugates showed extended half-lives compared to that of naked IFN, with the PolyPEG conjugates exhibiting the longest half-lives and the linear PEG conjugate, the shortest. Viscosity analysis showed that the linear PEG-IFN conjugate was over twice as viscous as both PolyPEG conjugates. Taken together, this work demonstrates the potential of PolyPEG conjugation to therapeutic proteins as a novel tool for optimizing pharmacokinetic profiles in a way that potentially allows administration of high-dose formulations because of lower conjugate viscosity.

Clinical observation of the therapeutic effects of pegylated recombinant human granulocyte colony-stimulating factor in patients with concurrent chemoradiotherapy-induced grade IV neutropenia

The aim of the present study was to investigate the efficacy and side-effects of preventive treatment with pegylated recombinant human granulocyte colony-stimulating factor (PEG-rhG-CSF) on concurrent chemoradiotherapy-induced grade IV neutropenia and to provide a rational basis for its clinical application. A total of 114 patients with concurrent chemoradiotherapy-induced grade IV neutropenia were enrolled. A randomized approach was used to divide the patients into an experimental group and a control group. The experimental group included three subgroups, namely a P-50 group, P-100 group and P + R group. The P-50 group had 42 cases, which were given a single 50-μg/kg subcutaneous injection of PEG-rhG-CSF. The P-100 group had 30 cases, which received a single 100-μg/kg subcutaneous injection of PEG-rhG-CSF. The P + R group comprised 22 cases, which were given a single 50-μg/kg subcutaneous injection of PEG-rhG-CSF and rhG-CSF 5 μg/kg/day; when the absolute neutrophil count (ANC) was ≥2.0×10⁹/l, the administration of rhG-CSF was stopped. The control group (RC group) comprised 20 patients, who received rhG-CSF 5 μg/kg/day by subcutaneous injection until the ANC was ≥2.0×10⁹/l. Changes in the neutrophil proliferation rate and ANC values over time, the neutropenic symptom remission time and incidence of adverse drug reactions were analyzed statistically in each group of patients. In the experimental group, the neutrophil proliferation rate and ANC values were significantly higher than those in the control group; the clinical effects began 12–24 h after treatment in the experimental group, and indicated that the treatment improved neutropenia in ~48 h after treatment. There was no significant difference in the neutrophil proliferation rate and ANC values between the P-50 and P+R groups. In the experimental group, the remission time of neutropenia-induced fever and muscle pain after administration was significantly shorter than that in the control group, with a statistically significant difference (P<0.05). The adverse drug reaction rates showed no significant difference between the experimental group and the control group. PEG-rhG-CSF had good efficacy and safety in the treatment of concurrent chemotherapy-induced grade IV neutropenia. For the treatment of concurrent chemotherapy-induced grade IV neutropenia, a single subcutaneous injection of 50 μg/kg PEG-rhG-CSF is the recommended dose. The effects begin at 12–24 h; if the ANC values are not significantly improved during this time, no supplementary administration of rhG-CSF is necessary.

Protein–polymer therapeutics: a macromolecular perspective

The development of protein–polymer hybrids emerged several decades ago with the vision that their synergistic combination will offer macromolecular hybrids with manifold features to succeed as the next generation therapeutics.

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.