Distribution and tissue uptake of poly(ethylene glycol) with different molecular weights after intravenous administration to mice

Long-Acting Human Interleukin 2 Bioconjugate Modified with Fatty Acids by Sortase A

Human Interleukin 2 (IL-2) has already achieved impressive results as a therapeutic agent for cancer and autoimmune diseases. However, one of the limitations associated with the clinical application of IL-2 is its short half-life owing to rapid clearance by the kidneys. Modification with fatty acids, as an albumin noncovalent ligand with the advantage of deep penetration into tissues and high activity-to-mass ratio, is a commonly used approach to improve the half-life of native peptides and proteins. In this investigation, we attempted to extend the half-life of IL-2 through conjugation with a fatty acid using sortase A (srtA). We initially designed and optimized three IL-2 analogues with different peptide linkers between the C-terminus of IL-2 and srtA recognition sequence (LPETG). Among these, analogue A3 was validated as the optimal IL-2 analogue for further modification. Next, six fatty acid moieties with the same fatty acid and different hydrophilic spacers were conjugated to A3 through srtA. The six bioconjugates generated were screened for in vitro biological activity, among which bioconjugate B6 was identified as near-optimal to IL-2. Additionally, B6 could effectively bind albumin through the conjugated fatty acid, which contributed to a significant improvement in its pharmacokinetic properties in vivo. In summary, we have developed a novel IL-2 bioconjugate, B6, modified with fatty acids using srtA, which may effectively serve as a new-generation long-acting IL-2 immunotherapeutic agent.

Polymeric Tissue Adhesives

Polymeric tissue adhesives provide versatile materials for wound management and are widely used in a variety of medical settings ranging from minor to life-threatening tissue injuries. Compared to the traditional methods of wound closure (i.e., suturing and stapling), they are relatively easy to use, enable rapid application, and introduce minimal tissue damage. Furthermore, they can act as hemostats to control bleeding and provide a tissue-healing environment at the wound site. Despite their numerous current applications, tissue adhesives still face several limitations and unresolved challenges (e.g., weak adhesion strength and poor mechanical properties) that limit their use, leaving ample room for future improvements. Successful development of next-generation adhesives will likely require a holistic understanding of the chemical and physical properties of the tissue-adhesive interface, fundamental mechanisms of tissue adhesion, and requirements for specific clinical applications. In this review, we discuss a set of rational guidelines for design of adhesives, recent progress in the field along with examples of commercially available adhesives and those under development, tissue-specific considerations, and finally potential functions for future adhesives. Advances in tissue adhesives will open new avenues for wound care and potentially provide potent therapeutics for various medical applications.

Multifunctional Role of Polyvinylpyrrolidone in Pharmaceutical Formulations

Polyvinylpyrrolidone (PVP), a non-ionic polymer, has been employed in multifarious fields such as paper, fibers and textiles, ceramics, and pharmaceutics due to its superior properties. Especially in pharmacy, the properties of inertness, non-toxicity, and biocompatibility make it a versatile excipient for both conventional formulations and novel controlled or targeted delivery systems, serving as a binder, coating agent, suspending agent, pore-former, solubilizer, stabilizer, etc. PVP with different molecular weights (MWs) and concentrations is used in a variety of formulations for different purposes. In this review, PVP-related researches mainly in recent 10 years were collected, and its main pharmaceutical applications were summarized as follows: (i) improving the bioavailability and stability of drugs, (ii) improving the physicomechanical properties of preparations, (iii) adjusting the release rate of drugs, and (iv) prolonging the in vivo circulation time of liposomes. Most of these applications could be explained by the viscosity, solubility, hydrophilicity, and hydrogen bond-forming ability of PVP, and the specific action mechanisms for each application were also tried to figure out. The effect of PVP on bioavailability improvement establishes it as a promising polymer in the emerging controlled or targeted formulations, attracting growing interest on it. Therefore, given its irreplaceability and tremendous opportunities for future developments, this review aims to provide an informative reference about current roles of PVP in pharmacy for interested readers.

Localized Delivery of Cisplatin to Cervical Cancer Improves Its Therapeutic Efficacy and Minimizes Its Side Effect Profile

PURPOSE

Cervical cancer represents the fourth most frequent malignancy in the world among women, and mortality has remained stable for the past 4 decades. Intravenous cisplatin with concurrent radiation therapy is the standard-of-care for patients with local and regional cervical cancer. However, cisplatin induces serious dose-limiting systemic toxicities and recurrence frequently occurs. In this study, we aimed to develop an intracervical drug delivery system that allows cisplatin release directly into the tumor and minimize systemic side effects.

METHODS AND MATERIALS

Twenty patient biopsies and 5 cell lines treated with cisplatin were analyzed for platinum content using inductively coupled plasma mass spectrometry. Polymeric implants loaded with cisplatin were developed and evaluated for degradation and drug release. The effect of local or systemic cisplatin delivery on drug biodistribution as well as tumor burden were evaluated in vivo, in combination with radiation therapy.

RESULTS

Platinum levels in patient biopsies were 6-fold lower than the levels needed for efficacy and radiosensitization in vitro. Cisplatin local delivery implant remarkably improved drug specificity to the tumor and significantly decreased accumulation in the blood, kidney, and other distant normal organs, compared with traditional systemic delivery. The localized treatment further resulted in complete inhibition of tumor growth.

CONCLUSIONS

The current standard-of-care systemic administration of cisplatin provides a subtherapeutic dose. We developed a polymeric drug delivery system that delivered high doses of cisplatin directly into the cervical tumor, while lowering drug accumulation and consequent side effects in normal tissues. Moving forward, these data will be used as the basis of a future first-in-human clinical trial to test the efficacy of localized cisplatin as adjuvant or neoadjuvant chemotherapy in local and regional cervical cancer.

Rational design, engineer, and characterization of a novel pegylated single isomer human arginase for arginine depriving anti-cancer treatment

AIMS

Arginine depleting enzymes are found effective to treat arginine-auxotrophic cancers and therapy-resistant malignancies, alone or in combination with cytotoxic agents or immune checkpoint inhibitors. We aim to select and validate a long-lasting, safe and effective PEGylated and cobalt-chelated arginase conjugated at the selective cysteine residue as a therapeutic agent against cancers.

MAIN METHODS

Exploring pharmacokinetic and pharmacodynamic properties of the three arginase conjugates with different PEG modality (20 kDa linear as A20L, 20 kDa branched as A20Y, and 40 kDa branched as A40Y) by cell-based and animal studies.

KEY FINDINGS

Arginase conjugates showed comparable systemic half-lives, about 20 h in rats and mice. The extended half-life of PEGylated arginase was concurrent with the integrity of conjugates of which PEG and protein moieties remain attached in bloodstream for 72 h after drug administration. Arginase modified with a linear 20 kDa PEG (A20L) was chosen as the lead candidate (PT01). In vitro assays confirmed the very potent cytotoxicity of PT01 against cancer cell lines of breast, prostate, and pancreas origin. In MIA PaCa-2 pancreatic and PC-3 prostate tumor xenograft models, weekly infusion of the PT01 at 5 and 10 mg/kg induced significant tumor growth inhibition of 44-67%. All mice experienced dose-dependent but rapidly reversible weight loss following each weekly dose, suggesting tolerable toxicity.

SIGNIFICANCE

These non-clinical data support PT01 as the lead candidate for clinical development that may benefit cancer patients by providing an alternative cytotoxic mechanism.

Pre-treatment with high molecular weight free PEG effectively suppresses anti-PEG antibody induction by PEG-liposomes in mice

Immune responses against polyethylene glycol (PEG) can lead to the rapid clearance of PEGylated drugs and are associated with increased risk of serious adverse events such as infusion reactions and anaphylaxis. Although select PEGylated therapeutics can induce anti-PEG antibodies (APA), there is currently no readily deployable strategy to mitigate their negative effects. Given the large number of PEGylated therapeutics that are either FDA-approved or in clinical development, methods that suppress APA induction to ensure the safety and efficacy of PEGylated drugs in patients would be a valuable clinical tool. We previously showed that infusion of high molecular weight (MW) free PEG can safely and effectively restore the circulation of PEG liposomes in animals with high pre-existing titers of APA, without stimulating additional APA production. Here, we explored the effectiveness of prophylaxis with free PEG or tolerogenic PEGylated liposomes as a strategy to reduce the amount of APA induced by subsequently administered PEGylated liposomes. Surprisingly, we found that a single administration of free PEG alone was capable of markedly reducing the APA response to PEG-liposomes for ~2 months; the effectiveness was comparable to, and frequently exceeded, interventions with different tolerogenic PEG-liposomes. These results support further investigations of free PEG prophylaxis as a potential strategy to ameliorate the APA response to sensitizing PEGylated therapeutics.

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.

Double hydrophilic block copolymers self-assemblies in biomedical applications

Double-hydrophilic block copolymers (DHBCs), consisting of at least two different water-soluble blocks, are an alternative to the classical amphiphilic block copolymers and have gained increasing attention in the field of biomedical applications. Although the chemical nature of the two blocks can be diverse, most classical DHBCs consist of a bioeliminable non-ionic block to promote solubilization in water, like poly(ethylene glycol), and a second block that is more generally a pH-responsive block capable of interacting with another ionic polymer or substrate. This second block is generally non-degradable and the presence of side chain functional groups raises the question of its fate and toxicity, which is a limitation in the frame of biomedical applications. In this review, following a first part dedicated to recent examples of non-degradable DHBCs, we focus on the DHBCs that combine a biocompatible and bioeliminable non-ionic block with a degradable functional block including polysaccharides, polypeptides, polyesters and other miscellaneous polymers. Their use to design efficient drug delivery systems for various biomedical applications through stimuli-dependent self-assembly is discussed along with the current challenges and future perspectives for this class of copolymers.

Thermally Targeted p50 Peptide Inhibits Proliferation and Induces Apoptosis of Breast Cancer Cell Lines

The application of rationally designed therapeutic peptides (TP) may improve outcomes in cancer treatment. These peptides hold the potential to directly target proliferative pathways and stimulate cell arrest or death pathways. Elastin-like polypeptide (ELP) is an elastin derived biopolymer that undergoes a thermally mediated phase transition. This study employs p50, a nuclear localization sequence derived peptide that inhibits the activation of NFκB and is implicated in cancer cell survival and metastasis. In order to effectively delivery p50, it is conjugated to SynB1-ELP1, a thermally responsive macromolecular carrier. By applying an external heat source, mild hyperthermic conditions (41 °C) induce aggregation and therefore can be used to specifically target ELP to solid tumors in cancer therapy. The addition of a cell penetrating peptide (CPP) to the N-terminus of the macromolecular carrier enhances the cellular uptake and directs the subcellular localization of the bioactive peptide. The novel TP, p50, inhibits proliferation and induces apoptosis of breast cancer cells by blocking the intranuclear import of NFκB. By expanding the repertoire of oncogenic targets, CPPs, and ELP carrier sizes, ELP-based polypeptides may be modulated to optimize the delivery of these novel therapies and allow for the flexibility to create individualized cancer therapies.

Intravitreal hydrogels for sustained release of therapeutic proteins

This review highlights how hydrogel formulations can improve intravitreal protein delivery to the posterior segment of the eye in order to increase therapeutic outcome and patient compliance. Several therapeutic proteins have shown excellent clinical successes for the treatment of various intraocular diseases. However, drug delivery to the posterior segment of the eye faces significant challenges due to multiple physiological barriers preventing drugs from reaching the retina, among which intravitreal protein instability and rapid clearance from the site of injection. Hence, frequent injections are required to maintain therapeutic levels. Moreover, because the world population ages, the number of patients suffering from ocular diseases, such as age-related macular degeneration (AMD) and diabetic retinopathy (DR) is increasing and causing increased health care costs. Therefore, there is a growing need for suitable delivery systems able to tackle the current limitations in retinal protein delivery, which also may reduce costs. Hydrogels have shown to be promising delivery systems capable of sustaining release of therapeutic proteins and thus extending their local presence. Here, an extensive overview of preclinically developed intravitreal hydrogels is provided with attention to the rational design of clinically useful intravitreal systems. The currently used polymers, crosslinking mechanisms, in vitro/in vivo models and advancements are discussed together with the limitations and future perspective of these biomaterials.

An antibody-supermolecule conjugate for tumor-specific targeting of tumoricidal methylated β-cyclodextrin-threaded polyrotaxanes

We previously found that acid-labile polyrotaxane containing methylated β-cyclodextrin (Me-PRX) induces endoplasmic reticulum (ER) stress-related autophagy and autophagic cell death. Me-PRX-induced autophagic cell death occurs even in apoptosis-resistant cells; tumor-targeted Me-PRX delivery could thus be an effective cancer treatment approach. In this study, antibody-supermolecule conjugates, consisting of a tumor-specific antibody and Me-PRX, were designed to achieve a tumor-specific delivery of Me-PRX. Trastuzumab, a monoclonal antibody against HER2 expressed in various malignant tumors, was selected as a tumor-targeting antibody, and phenyl maleimide group-modified Me-PRX (Mal-Me-PRX) was conjugated to the cysteine residue of the reduced Trastuzumab to obtain a Trastuzumab-Me-PRX conjugate (Tras-Me-PRX). The cellular association of Tras-Me-PRX to HER2-expressing tumor cells was remarkably greater than that of unmodified Me-PRX. Moreover, Tras-Me-PRX effectively reduced the viability of HER2-expressing tumor cells at a lower concentration compared to the unmodified Me-PRX. In conclusion, antibody-Me-PRX conjugates are regarded as a new class of antibody-drug conjugates that would contribute to the chemotherapy of cancers.

Cell encapsulation spatially alters crosslink density of poly(ethylene glycol) hydrogels formed from free-radical polymerizations

Photopolymerizable poly(ethylene glycol) (PEG) hydrogels are a promising platform for chondrocyte encapsulation and cartilage tissue engineering. This study demonstrates that during the process of encapsulation, chondrocytes alter the formation of PEG hydrogels leading to a reduction in the bulk and local hydrogel crosslink density. Freshly isolated chondrocytes were shown to interact with hydrogel precursors, in part through thiol-mediated events between dithiol crosslinkers and cell surface free thiols, depleting crosslinker concentration and causing a reduction in the bulk hydrogel crosslink density. This effect was more pronounced with increasing cell density at the time of encapsulation. Encapsulation of chondrocytes in fluorescently labeled hydrogels exhibited a gradient in hydrogel density around the cell, which was abrogated by treatment of the cells with the antioxidant estradiol prior to encapsulation. This gradient led to spatial variations in the degradation behavior of a hydrolytically degradable PEG hydrogel, creating regions devoid of hydrogel surrounding cells. Collectively, findings from this study indicate that the antioxidant defense mechanisms in chondrocytes alter the resultant properties of PEG hydrogels formed by free-radical polymerizations. These interactions will have a significant impact on tissue engineering, affecting the local microenvironment around cells and how tissue grows within the hydrogels. STATEMENT OF SIGNIFICANCE: Cell encapsulations in synthetic hydrogels formed by free-radical polymerizations offer numerous benefits for tissue engineering. Herein, we studied cartilage cells and identified that during encapsulation, cells interfered with hydrogel formation through two distinct mechanisms. Thiol-mediated events between monomers led to monomer depletion and a lower crosslinked hydrogel. Cells' antioxidant defense mechanisms interfered with free-radicals and inhibited hydrogel formation near the cell. These cell-mediated effects led to softer hydrogels and created unique hydrogel degradations patterns causing rapid degradation around the cells. The latter has benefits for tissue engineering, where these regions provide space for tissue growth. Overall, this study demonstrates that cells play a key role in how the hydrogel structure forms when cells are present.

Transient stealth coating of liver sinusoidal wall by anchoring two-armed PEG for retargeting nanomedicines

A major critical issue in systemically administered nanomedicines is nonspecific clearance by the liver sinusoidal endothelium, causing a substantial decrease in the delivery efficiency of nanomedicines into the target tissues. Here, we addressed this issue by in situ stealth coating of liver sinusoids using linear or two-armed poly(ethylene glycol) (PEG)-conjugated oligo(l-lysine) (OligoLys). PEG-OligoLys selectively attached to liver sinusoids for PEG coating, leaving the endothelium of other tissues uncoated and, thus, accessible to the nanomedicines. Furthermore, OligoLys having a two-armed PEG configuration was ultimately cleared from sinusoidal walls to the bile, while OligoLys with linear PEG persisted in the sinusoidal walls, possibly causing prolonged disturbance of liver physiological functions. Such transient and selective stealth coating of liver sinusoids by two-arm-PEG-OligoLys was effective in preventing the sinusoidal clearance of nonviral and viral gene vectors, representatives of synthetic and nature-derived nanomedicines, respectively, thereby boosting their gene transfection efficiency in the target tissues.

Plasma Polyethylene Glycol (PEG) Levels Reach Steady State Following Repeated Treatment with N8-GP (Turoctocog Alfa Pegol; Esperoct®)

Background

Extended half-life (EHL) factor VIII (FVIII)-replacement therapies enable patients with haemophilia A to maintain higher activity levels with fewer injections. N8-GP (turoctocog alfa pegol; Esperoct^®) is an EHL product derived from conjugation of polyethylene glycol (PEG) to a recombinant FVIII protein. Upon activation, PEG is released from the active protein and excreted in urine and faeces. While PEG levels are expected to reach steady state with repeated dosing, there has been some discussion regarding whether abnormal accumulation of PEG in plasma and tissues may occur.

Objective

Our objective was to examine plasma PEG concentrations in rats and humans repeatedly treated with N8-GP for periods of up to 5 years.

Methods

PEG levels were measured using liquid chromatography-tandem mass spectrometry in plasma samples from rats treated with N8-GP as part of a 52-week toxicity study. Human plasma samples from children, adolescents and adults treated with N8-GP as part of the pathfinder programme were also examined (NCT01731600; NCT01480180). These data were compared with steady-state PEG levels predicted by pharmacokinetic modelling of single-dose rat data.

Results

PEG levels reached steady state in plasma in both rats and humans after repeated dosing. The timing and degree of PEG increase to steady state were in line with or below model predictions, confirming the utility of the pharmacokinetic model and indicating that rat data can be used to estimate human plasma PEG levels.

Conclusion

Steady-state PEG levels were reached in plasma from rats and humans repeatedly treated with N8-GP. No unexpected increase in PEG was observed.

Photo-crosslinked anhydride-modified polyester and -ethers for pH-sensitive drug release

Photo-crosslinkable polymers have a great potential for the delivery of sensitive drugs. They allow preparation of drug releasing devices by photo-crosslinking, thus avoiding high processing temperatures. In this study, the hydrolysis behavior and drug release of three different photo-crosslinkable poly(ether anhydride)s and one poly(ester anhydride) were investigated. Three-arm poly(ethylene glycol) or polycaprolactone was reacted with succinic anhydride to obtain carboxylated macromers, and further functionalized with methacrylic anhydride to form methacrylated marcromers with anhydride linkages. The synthetized macromers were used to prepare photo-crosslinked matrices with different hydrolytic degradation times for active agent release purposes. The hydrolysis was clearly pH-sensitive: polymer networks degraded slowly in acidic conditions, and degradation rate increased as the pH shifted towards basic conditions. Drug release was studied with two water-soluble model drugs lidocaine (234 mol/g) and vitamin B₁₂ (1355 g/mol). Vitamin B₁₂ was released mainly due to polymer network degradation, whereas smaller molecule lidocaine was released also through diffusion and swelling of polymer network. Only a small amount of vitamin B₁₂ was released in acidic conditions (pH 1.3 and pH 2.1). These polymers have potential in colon targeted drug delivery as the polymer could protect sensitive drugs from acidic conditions in the stomach, and the drug would be released as the conditions change closer to neutral pH in the intestine.

Tailoring Kidney Transport of Organic Dyes with Low-Molecular-Weight PEGylation

Subtle changes in size can induce distinct responses of the body to hard nanomaterials; however, it is largely unknown whether just a few ethylene oxide unit differences in soft poly(ethylene glycol) (PEG) molecules could significantly alter the renal clearance of small molecules. By systematically investigating in vivo transport of the representative renal clearable organic dyes, IRDye800CW after being conjugated with a series of PEG molecules with molecular weight (MW) below 10 kDa, we found a MW-dependent scaling law: PEG45 (MW = 2100 Da) is an optimized MW to generate the most efficient renal clearance for IRDye800CW by expediting the glomerular filtration of organic dyes and reducing their nonspecific interactions with background tissue. Moreover, the uniqueness of PEG45 can be generalized to other organic dyes such as ZW800-1 and fluorescein. This finding highlights the importance of low-MW PEGylation in tailoring in vivo transport of organic fluorophores, which would broaden their biomedical applications.

Size-Dependent EPR Effect of Polymeric Nanoparticles on Tumor Targeting

Passive targeting of large nanoparticles by the enhanced permeability and retention (EPR) effect is a crucial concept for solid tumor targeting in cancer nanomedicine. There is, however, a trade-off between the long-term blood circulation of nanoparticles and their nonspecific background tissue uptake. To define this size-dependent EPR effect, near-infrared fluorophore-conjugated polyethylene glycols (PEG-ZW800s; 1-60 kDa) are designed and their biodistribution, pharmacokinetics, and renal clearance are evaluated in tumor-bearing mice. The targeting efficiency of size-variant PEG-ZW800s is investigated in terms of tumor-to-background ratio (TBR). Interestingly, smaller sized PEGs (≤20 kDa, 12 nm) exhibit significant tumor targeting with minimum to no nonspecific uptakes, while larger sized PEGs (>20 kDa, 13 nm) accumulate highly in major organs, including the lungs, liver, and pancreas. Among those tested, 20 kDa PEG-ZW800 exhibits the highest TBR, while excreting unbound molecules to the urinary bladder. This result lays a foundation for engineering tumor-targeted nanoparticles and therapeutics based on the size-dependent EPR effect.

Polymer-Graphene Nanoassemblies and their Applications in Cancer Theranostics

BACKGROUND AND OBJECTIVE

Graphene-based nanomaterials have received increasing attention due to their unique physical-chemical properties including two-dimensional planar structure, large surface area, chemical and mechanical stability, superconductivity and good biocompatibility. On the other hand, graphene-based nanomaterials have been explored as theranostics agents, the combination of therapeutics and diagnostics. In recent years, grafting hydrophilic polymer moieties have been introduced as an efficient approach to improve the properties of graphene-based nanomaterials and obtain new nanoassemblies for cancer therapy.

METHODS AND RESULTS

This review would illustrate biodistribution, cellular uptake and toxicity of polymergraphene nanoassemblies and summarize part of successes achieved in cancer treatment using such nanoassemblies.

CONCLUSION

The observations showed successful targeting functionality of the polymer-GO conjugations and demonstrated a reduction of the side effects of anti-cancer drugs for normal tissues.

Synthetic 3D PEG-Anisogel Tailored with Fibronectin Fragments Induce Aligned Nerve Extension

An enzymatically cross-linked polyethylene glycol (PEG)-based hydrogel was engineered to promote and align nerve cells in a three-dimensional manner. To render the injectable, otherwise bioinert, PEG-based material supportive for cell growth, its mechanical and biochemical properties were optimized. A recombinant fibronectin fragment (FNIII9*-10/12-14) was coupled to the PEG backbone during gelation to provide cell adhesive and growth factor binding domains in close vicinity. Compared to full-length fibronectin, FNIII9*-10/12-14 supports nerve growth at similar concentrations. In a 3D environment, only the ultrasoft 1 w/v% PEG hydrogels with a storage modulus of ∼10 Pa promoted neuronal growth. This gel was used to establish the first fully synthetic, injectable Anisogel by the addition of magnetically aligned microelements, such as rod-shaped microgels or short fibers. The Anisogel led to linear neurite extension and represents a large step in the direction of clinical translation with the opportunity to treat acute spinal cord injuries.

Mono-PEGylates of exenatide in branched and dimeric structures can improve in vivo stability and hypoglycemic bioactivity

Exenatide, a synthetic version of exendin-4, is a glucagon-like peptide-1 receptor agonist (GLP-1RA) used for treating diabetes, but its relatively short half-life is a major disadvantage. In this study, we attempted residue-specific mono-PEGylation to the middle of the amino acid backbone to extend its in vivo half-life. Exenatide was point-mutated from Lys to Cys at the 12th residue to yield a variant (K12C), and PEG-maleimide of varying molecular weights (MW) (5, 10, 20, 40 kD) was site-specifically conjugated to yield a mono-PEGylate with branched T-shape molecular structure. In another approach, we conjugated a bis-maleimide PEG (10 kD) to the middle of two K12Cs to yield an H-shape homodimer PEGylate In vitro bioactivity assays indicated that: (1) PEGylates conjugated with higher MW PEG lead to stronger receptor binding, (2) the branched form was superior to the linear configuration in the binding, and (3) both T-shape and H-shape mono-PEGylates demonstrated better potency than the native exenatide, evidenced by lower EC₅₀. Db/db mouse experiments to evaluate in vivo hypoglycemic activity indicated that: (1) all mono-PEGylates resulted in improved glucose tolerance compared to the native exenatide, (2) the homodimer PEGylate demonstrated much stronger hypoglycemic activity, especially during the initial period, and (3) the H-shape and T-shape mono-PEGylates (40 kD) maintained hypoglycemia for up to ca. 168 and 140 h, representing approximately 12- and 14-fold increase, respectively, compared with the native exenatide. Our findings suggest that the exenatide mono-PEGylates in unclassical molecular structures can improve in vivo pharmacokinetics properties.

Preclinical evaluation of topically-administered PEGylated Fab' lung toxicity

PEGylation is a promising approach to increase the residence time of antibody fragments in the lungs and sustain their therapeutic effects. However, concerns arise as to the potential pulmonary toxicity of antibody fragments conjugated to high molecular weight (HMW) polyethylene glycol (PEG), notably after repeated administrations, and the possibility of PEG accumulation in the lungs. The purpose of this proof-of-concept study is to give insights about the safety of lung administration of a Fab’ anti-IL17A antibody fragment conjugated to two-armed 40 kDa PEG (PEG40). The presence of the PEG40 moiety inside alveolar macrophages remained stable for at least 24 h after intratracheal administration of PEG40-Fab’ to mice. PEG40 was then progressively cleared from alveolar macrophages. Incubation of PEG40 alone with macrophages in vitro did not significantly harm macrophages and did not affect phagocytosis or the production of inflammatory markers. After acute or chronic administration of PEG40-Fab’ to mice, no signs of significant pulmonary toxicity or inflammatory cell accumulation were observed. A vacuolization of alveolar macrophages not associated with any inflammation was noticed when PEG40, PEG40-Fab’, or unPEGylated Fab’ were administered. To conclude this preliminary proof of concept study, acute or repeated pulmonary administrations of PEGylated Fab’ appear safe in rodents.

Long circulating liposomes: challenges and opportunities

The poor pharmacokinetic parameters and low solubility of many anticancer therapeutics have warranted the use of drug-delivery systems such as liposomes. Overcoming some drawbacks of the conventional liposomes, targeted liposomal delivery by longer circulation time by addition of poly(ethylene glycol) to the liposomal surface and further adding specific ligands to achieve ligand selective retention and uptake has been introduced. PEGylated liposomes are the only second-generation liposomal formulations in clinical use and are now being challenged with the allergenic response they pose even in the treatment of naive patients. This article will review the challenges and hindrances in the use of long circulating liposomes and explore the opportunities to overcome this issue.

Identification of somatostatin receptors using labeled PEGylated octreotide, as an active internalization

Numerous normal and tumors cells are well-known to express the somatostatin receptors (SSTRs) on their surface which makes the receptor be useful for tumor scintigraphy. Thus, the identification of SSTRs is beneficial, especially SSTR₂. The somatostatin analog, Octreotide (OCT), was chosen as a ligand, as it is known to selectively bind to SSTR₂. Moreover, polyethylene glycol (PEG), 8armPEG, was used as a branched PEG to provide a low nonspecific cell binding and easily chemical modification. OCT and fluorescein (Flu) were conjugated to branched PEG using a water-soluble carbodiimide (EDC) and N-hydroxy succinimide (NHS) so as to activate its carboxylic acid group. 8armPEG-tagged Flu and OCT was characterized by gel permeation chromatography (GPC) to proof the conjugation of OCT to 8armPEG. Finally, cellular uptake was studied using pancreatic cancer cells with well-expressed somatostatin receptors using a confocal laser scanning microscope (CLMS) and fluorescence activated cell sorting (FACS). GPC showed increases in molecular mass since it showed a difference in elution time of 8armPEG itself and 8armPEG labeled with Flu. CLMS and FACS showed high binding with the positive SSTR₂ cells expression and showed negative results with negative expressing SSTR₂. These bindings were decreased when the receptors were occupied with free OCT which confirms the specific binding to SSTR₂. Therefore, we formulated a novel model to easily identify SSTR₂ and other receptors which serves as a promising platform for identification of tumor cells overexpressing the SSTR₂, which would be a hopeful target for cancer therapy and tumor scintigraphy.

Overcoming anti-PEG antibody mediated accelerated blood clearance of PEGylated liposomes by pre-infusion with high molecular weight free PEG

Antibodies that specifically bind polyethylene glycol (PEG), i.e. anti-PEG antibodies (APA), are associated with reduced efficacy and increased risk of serious adverse events for several PEGylated therapeutics. Here, we explored the concept of using free PEG molecules to saturate circulating APA. Surprisingly, we found that 40 kDa free PEG effectively restored the prolonged circulation of PEGylated liposomes in the presence of high titers of pre-existing APA for at least 48 h in mice. In contrast, lower molecular weight free PEG (≤10 kDa) failed to restore circulation beyond a few hours. These in vivo results were consistent with estimates from a minimal physiologically based pharmacokinetic model. Importantly, the infusion of free PEG appeared to be safe in mice previously sensitized by injection of PEGylated liposomes, and free PEG did not elicit excess APA production even in mice with pre-existing adaptive immunity against PEG. Our results support further investigation of high molecular weight free PEG as a potential method to control and overcome high titers of APA, restoring the prolonged circulation of PEGylated liposomes and possibly other PEGylated therapeutics.

Probing the subcutaneous absorption of a PEGylated FUD peptide nanomedicine via in vivo fluorescence imaging

The Functional Upstream Domain (FUD) peptide is a potent inhibitor of fibronectin assembly and a therapeutic candidate for disorders linked with hyperdeposition of fibronectin-modulated ECM proteins. Most recently, experiments involving subcutaneous (s.c.) administration of a PEGylated FUD (PEG-FUD) of 27.5 kDa molecular weight yielded a significant reduction of fibronectin and collagen deposition in a murine model of renal fibrosis. The benefits of FUD PEGylation need to be studied to unlock the full potential of the PEG-FUD platform. This work studies the impact of PEGylating the FUD peptide with differently sized PEG on its absorption from the site of injection following s.c. delivery using non-invasive in vivo fluorescence imaging. The FUD and mFUD (control) peptides and their 10 kDa, 20 kDa, and 40 kDa PEG conjugates were labeled with the sulfo-Cy5 fluorophore. Isothermal titration calorimetry (ITC) and confocal fluorescence microscopy experiments verified FUD and PEG-FUD fibronectin binding activity preservation following sulfo-Cy5 labeling. Fluorescence in vivo imaging experiments revealed a linear relationship between the absorption apparent half-life (t_1/2) and the MW of FUD, mFUD, and their PEG conjugates. Detected drug signal in the kidney and bladder regions of mice suggests that smaller peptides of both the FUD and mFUD series enter the kidney earlier and in higher amounts than their larger PEG conjugates. This work highlights an important delayed dose absorption enhancement that MW modification via PEGylation can contribute to a drug when combined with the subcutaneous route of delivery.

Tetra-PEG Based Hydrogel Sealants for In Vivo Visceral Hemostasis

Medical sealant devices for in vivo hemostasis are far from satisfactory in the aged society. A major challenge is effective integration of quick hemorrhage control of the increased anticoagulated patients, high safety, and facile accessibility. Here, a well-defined ammonolysis-based Tetra-PEG hydrogel sealant is developed with rapid gelation speed, strong tissue adhesion, and high mechanical strength. Introduction of cyclized succinyl ester groups into a hydrogel matrix endows the sealant with fast degradable and controllably dissolvable properties. The hydrogel possesses outstanding hemostatic capabilities even under the anticoagulated conditions while displaying excellent biocompatibility and feasibility. These results reveal that the optimized hydrogel may be a facile, effective, and safe sealant for hemorrhage control in vivo.

Printing Therapeutic Proteins in 3D using Nanoengineered Bioink to Control and Direct Cell Migration

A nanoengineered bioink loaded with therapeutic proteins is designed to direct cell function in a 3D printed construct. The bioink is developed from a hydrolytically degradable polymer and 2D synthetic nanoparticle. The synthesis of poly(ethylene glycol)-dithiothreitol (PEGDTT) via a Michael-like step growth polymerization results in acrylate terminated degradable macromer. The addition of 2D nanosilicates to PEGDTT results in formation of shear-thinning bioinks with high printability and structural fidelity. The mechanical properties, swelling kinetics, and degradation rate of 3D printed constructs can be modulated by changing the ratio of PEG:PEGDTT and nanosilicates concentration. Due to high surface area and charged characteristic of nanosilicates, protein therapeutics can be sequestered in 3D printing structure for prolong duration. Sustained release of pro-angiogenic therapeutics from 3D printed structure, promoted rapid migration of human endothelial umbilical vein cell. This approach to design biologically active inks to control and direct cell behavior can be used to engineer 3D complex tissue structure for regenerative medicine.

Exploration of biomedical dendrimer space based on in-vivo physicochemical parameters: Key factor analysis (Part 2)

In nanomedicine, the widespread concern of nanoparticles in general, and dendrimers, in particular, is the analysis of key in-vivo physicochemical parameters to ensure the preclinical and clinical development of 'safe' bioactive nanomaterials. It is clear that for biomedical applications, biocompatible dendrimers, used as nanocarriers or active per se, should be devoid of toxicity and immunogenicity, and have adequate PK/PD behaviors (adequate exposure) in order to diffuse in different tissues. Functionalization of dendrimers has a dramatic effect on in-vivo physicochemical parameters. In this review, we highlighted key in-vivo physicochemical properties, based on data from biochemical, cellular and animal models, to provide biocompatible dendrimers. Up-to-date, only scarce studies have been described on this topic.

Absorption, distribution, metabolism and excretion of the biomaterials used in Nanocarrier drug delivery systems

Nanocarriers (NCs) are a type of drug delivery system commonly used to regulate the pharmacokinetic and pharmacodynamic properties of drugs. Although a wide variety of NCs has been developed, relatively few have been registered for clinical trials and even fewer are clinically approved. Overt or potential toxicity, indistinct mechanisms of drug release and unsatisfactory pharmacokinetic behavior all contribute to their high failure rate during preclinical and clinical testing. These negative characteristics are not only due to the NCs themselves but also to the materials of the drug nanocarrier system (MDNS) that are released in vivo. In this article, we review the main analytical techniques used for bioassay of NCs and MDNS and their pharmacokinetics after administration by various routes. We anticipate our review will serve to improve the understanding of MDNS pharmacokinetics and facilitate the development of NC drug delivery systems.

Synthesis of Mono- and Dithiols of Tetraethylene Glycol and Poly(ethylene glycol)s via Enzyme Catalysis

This paper investigates the transesterification of methyl 3-mercaptopropionate (MP-SH) with tetraethylene glycol (TEG) and poly(ethylene glycol)s (PEG)s catalyzed by Candida antarctica Lipase B (CALB) without the use of solvent (in bulk). The progress of the reactions was monitored by 1H-NMR spectroscopy. We found that the reactions proceeded in a step-wise manner, first producing monothiols. TEG-monothiol was obtained in 15 min, while conversion to dithiol took 8 h. Monothiols from PEGs with Mn = 1000 and 2050 g/mol were obtained in 8 and 16 h, respectively. MALDI-ToF mass spectrometry verified the absence of dithiols. The synthesis of dithiols required additional fresh CALB and MP-SH. The structure of the products was confirmed by 1H-NMR and 13C-NMR spectroscopy. Enzyme catalysis was found to be a powerful tool to effectively synthesize thiol-functionalized TEGs and PEGs.

A Simple and Efficient Method for Synthesis of Carboxymethylated Polyethyleneglycol

A simple and efficient method for the synthesis of carboxymethylated polyethylene glycol (CM-PEG) by the oxidation of the corresponding monomethoxy polyethylene glycol (mPEG) with catalytic amounts of TEMPO and hypobromide as a regenerating oxidant and water as solvent was developed.

Safety of recombinant coagulation factors in treating hemophilia

INTRODUCTION

During the last decade, new FVIII/IX concentrates have been developed for the treatment of patients affected by hemophilia A/B. Significant progress has been achieved regarding their half-life, but the old issue of immunogenicity and new concerns about safety need to be addressed.

AREAS COVERED

After the implementation of virucidal methods, both plasma-derived and recombinant clotting factor concentrates achieved a very safe profile. The development of anti-FVIII antibodies is the major adverse event of replacement therapy with both FVIII concentrates. Furthermore, the new extended half-life concentrates, protein fused or pegylated, raised some concerns about their side effects.

EXPERT OPINION

The treatment of hemophilia A with inhibitors by induction of immunotolerance and using by-passing concentrates, improved the quality of life of patients but did not allow them to have a life expectancy like that of patients without inhibitors. The new humanized monoclonal antibody (MAb) ACE910, mimicking FVIII function, seems to be able to reduce the bleedings of hemophilia A patients with inhibitors. The post-marketing surveillance will clarify if the adverse events observed during the phase III clinical trials and compassionate use were due to the association with a Prothrombin activated complex concentrate or to the prothrombotic effect of the drug itself.

Reshapable hydrogel tissue expander for ridge augmentation: Results of a series of successive insertions at the same intraoral site

BACKGROUND

Oral mucosa expansion before ridge augmentation is a procedure to reduce soft tissue exposure and to improve bone graft density and volume after augmentation. This study explored a novel, shapeable hydrogel tissue expander (HTE) in intraoral sites that had undergone previous expansion and surgery.

METHODS

Nine beagle dogs had all premolar teeth extracted and adjacent alveolar bone reduced. After at least 3 months healing hydrogels were placed at 4 sites in each dog: maxilla and mandible, right and left. After 6 weeks of expansion, the hydrogels were removed and measured for volume expansion and physical condition. Punch biopsies were taken of the expanded oral mucosa. After 3 months, a second hydrogel insertion was performed at each of the same sites. After this second expansion cycle, volume and hydrogel condition were recorded. Three dogs received ultrasound imaging of the hydrogels during the second expansion. Necropsy specimens were taken of both expanded and non-expanded oral mucosa.

RESULTS

Within 2 weeks after HTE insertion in both first and second insertions, blood flow returned to the pre-insertion level. The first and second insertions resulted in linear oral mucosa gain of 8.13 mm, and 6.44 mm, respectively. First and second insertion hydrogels erupted from 4% of the first expansion sites, and 3% of the second expansion sites. There was no directional migration of the expanding hydrogel at any site. Histology found little inflammatory reaction to any hydrogel implant.

CONCLUSION

Oral mucosa can be consistently and successfully expanded before bone graft for ridge augmentation even at sites with a history of prior surgeries.

Single-Domain Antibodies and Their Formatting to Combat Viral Infections

Since their discovery in the 1990s, single-domain antibodies (VHHs), also known as Nanobodies^®, have changed the landscape of affinity reagents. The outstanding solubility, stability, and specificity of VHHs, as well as their small size, ease of production and formatting flexibility favor VHHs over conventional antibody formats for many applications. The exceptional ease by which it is possible to fuse VHHs with different molecular modules has been particularly explored in the context of viral infections. In this review, we focus on VHH formats that have been developed to combat viruses including influenza viruses, human immunodeficiency virus-1 (HIV-1), and human respiratory syncytial virus (RSV). Such formats may significantly increase the affinity, half-life, breadth of protection of an antiviral VHH and reduce the risk of viral escape. In addition, VHHs can be equipped with effector functions, for example to guide components of the immune system with high precision to sites of viral infection.

Long circulating genetically encoded intrinsically disordered zwitterionic polypeptides for drug delivery

The clinical utility of many peptide and protein drugs is limited by their short in-vivo half-life. To address this limitation, we report a new class of polypeptide-based materials that have a long plasma circulation time. The design of these polypeptides is motivated by the hypothesis that incorporating a zwitterionic sequence, within an intrinsically disordered polypeptide motif, would impart "stealth" behavior to the polypeptide and increase its plasma residence time, a behavior akin to that of synthetic stealth polymers. We designed these zwitterionic polypeptides (ZIPPs) with a repetitive (VPX₁X₂G)_n motif, where X₁ and X₂ are cationic and anionic amino acids, respectively, and n is the number of repeats. To test this hypothesis, we synthesized a set of ZIPPs with different pairs of cationic and anionic residues with varied chain length. We show that a combination of lysine and glutamic acid in the ZIPP confer superior pharmacokinetics, for both intravenous and subcutaneous administration, compared to uncharged control polypeptides. Finally, to demonstrate their clinical utility, we fused the best performing ZIPP sequence to glucagon-like peptide-1 (GLP1), a peptide drug used for treatment of type-2 diabetes and show that the ZIPP-GLP1 fusion outperforms an uncharged polypeptide of the same molecular weight in a mouse model of type-2 diabetes.

Development of a docetaxel micellar formulation using poly(ethylene glycol)-polylactide-poly(ethylene glycol) (PEG-PLA-PEG) with successful reconstitution for tumor targeted drug delivery

Docetaxel (DTX)-loaded polymeric micelles (DTBM) were formulated using the triblock copolymer, poly(ethylene glycol)-polylactide-poly(ethylene glycol) (PEG-PLA-PEG), to comprehensively study their pharmaceutical application as anticancer nanomedicine. DTBM showed a stable formulation of anticancer nanomedicine that could be reconstituted after lyophilization (DTBM-R) in the presence of PEG 2000 and D-mannitol (Man) as surfactant and protectant, respectively. DTBM-R showed a particle size less than 150 nm and greater than 90% of DTX recovery after reconstitution. The robustly formed micelles might minimize systemic toxicity due to their sustained drug release and also maximize antitumor efficacy through increased accumulation and release of DTX from the micelles. From the pharmaceutical development point of view, DTBM-R showing successful reconstitution could be considered as a potent nanomedicine for tumor treatment.