Measurement of Pre-Existing IgG and IgM Antibodies against Polyethylene Glycol in Healthy Individuals

Surface modification of extracellular vesicles with polyoxazolines to enhance their plasma stability and tumor accumulation

Extracellular vesicles (EVs) are future promising therapeutics, but their instability in vivo after administration remains an important barrier to their further development. Many groups evaluated EV surface modification strategies to add a targeting group with the aim of controlling EV biodistribution. Conversely, fewer groups focused on their stabilization to obtain "stealth" allogenic EVs. Modulating their stabilization and biodistribution is an essential prerequisite for their development as nano-therapeutics. Here, we explored polyoxazolines with lipid anchors association to the EV membrane (POxylation as an alternative to PEGylation) to stabilize EVs in plasma and control their biodistribution, while preserving their native properties. We found that this modification maintained and seemed to potentiate the immunomodulatory properties of EVs derived from mesenchymal stem/stromal cells (MSC). Using a radiolabeling protocol to track EVs at a therapeutically relevant concentration in vivo, we demonstrated that POxylation is a promising option to stabilize EVs in plasma because it increased EV half-life by 6 fold at 6 h post-injection. Moreover, EV accumulation in tumors was higher after POxylation than after PEGylation.

Stealth mRNA nanovaccines to control lymph node trafficking

mRNA-based vaccines symbolize a new paradigm shift in personalized medicine for the treatment of infectious and non-infectious diseases. However, the reactogenicity associated with the currently approved formulations limits their applicability in autoinflammatory disorders, such as tumour therapeutics. In this study, we present a delivery system showing controlled immunogenicity and minimal non-specific inflammation, allowing for selective delivery of mRNA to antigen presenting cells (APCs) within the medullary region of the lymph nodes. Our platform offers precise control over the trafficking of nanoparticles within the lymph nodes by optimizing stealth and targeting properties, as well as the subsequent opsonization process. By targeting specific cells, we observed a potent adaptive and humoral immune response, which holds promise for preventive and therapeutic anti-tumoral vaccines. Through spatial programming of nanoparticle distribution, we can promote robust immunization, thus improving and expanding the utilization of mRNA vaccines. This innovative approach signifies a remarkable step forward in the field of targeted nanomedicine.

Liposomes with Low Levels of Grafted Poly(ethylene glycol) Remain Susceptible to Destabilization by Anti-Poly(ethylene glycol) Antibodies

Binding of anti-PEG antibodies to poly(ethylene glycol) (PEG) on the surface of PEGylated liposomal doxorubicin (PLD) in vitro and in rats can activate complement and cause the rapid release of doxorubicin from the liposome interior. Here, we find that irinotecan liposomes (IL) and L-PLD, which have 16-fold lower levels of 1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE)-PEG2000 in their liposome membrane as compared to PLD, generate less complement activation but remain sensitive to destabilization and drug release by anti-PEG antibodies. Complement activation and liposome destabilization correlated with the theoretically estimated number of antibody molecules bound per liposome. Drug release from liposomes proceeded through the alternative complement pathway but was accelerated by the classical complement pathway. In contrast to PLD destabilization by anti-PEG immunoglobulin G (IgG), which proceeded by the insertion of membrane attack complexes in the lipid bilayer of otherwise intact PLD, anti-PEG IgG promoted the fusion of L-PLD, and IL to form unilamellar and oligo-vesicular liposomes. Anti-PEG immunoglobulin M (IgM) induced drug release from all liposomes (PLD, L-PLD, and IL) via the formation of unilamellar and oligo-vesicular liposomes. Anti-PEG IgG destabilized both PLD and L-PLD in rats, indicating that the reduction of PEG levels on liposomes is not an effective approach to prevent liposome destabilization by anti-PEG antibodies.

An Assay for Immunogenic Detection of Anti-PEG Antibody

With the increasing use of polyethylene glycol (PEG) based proteins and drug delivery systems, anti-PEG antibodies have commonly been detected among the population, causing the accelerated blood clearance and hypersensitivity reactions, poses potential risks to the clinical efficacy and safety of PEGylated drugs. Therefore, vigilant monitoring of anti-PEG antibodies is crucial for both research and clinical guidance regarding PEGylated drugs. The enzyme-linked immunosorbent assay (ELISA) is a common method for detecting anti-PEG antibodies. However, diverse coating methods, blocking solutions and washing solutions have been employed across different studies, and unsuitable use of Tween 20 as the surfactant even caused biased results. In this study, we established the optimal substrate coating conditions, and investigated the influence of various surfactants and blocking solutions on the detection accuracy. The findings revealed that incorporating 1 % bovine serum albumin into the serum dilution in the absence of surfactants will result the credible outcomes of anti-PEG antibody detection.

Impact of the Hydrophilicity of Poly(sarcosine) on Poly(ethylene glycol) (PEG) for the Suppression of Anti-PEG Antibody Binding

A method of poly(ethylene glycol) (PEG) conjugation is known as PEGylation, which has been employed to deliver therapeutic drugs, proteins, or nanoparticles by considering the intrinsic non- or very low immunogenic property of PEG. However, PEG has its weaknesses, and one major concern is the potential immunogenicity of PEGylated proteins. Because of its hydrophilicity, poly(sarcosine) (P(Sar)) may be an attractive-and superior-substitute for PEG. In the present study, we designed a double hydrophilic diblock copolymer, methoxy-PEG-b-P(Sar) m (m = 5-55) (mPEG-P(Sar) m ), and synthesized a triblock copolymer with hydrophobic poly(l-isoleucine) (P(Ile)). We validated that double hydrophilic mPEG-P(Sar) block copolymers suppressed the specific binding of three monoclonal anti-PEG antibodies (anti-PEG mAbs) to PEG. The results of our indirect ELISAs indicate that P(Sar) significantly helps to reduce the binding of anti-PEG mAbs to PEG. Importantly, the steady suppression of this binding was made possible, in part, thanks to the maximum number of sarcosine units in the triblock copolymer, as evidenced by sandwich ELISA and biolayer interferometry assay (BLI): the intrinsic hydrophilicity of P(Sar) had a clear supportive effect on PEG. Finally, because we used P(Ile) as a hydrophobic block, PEG-P(Sar) might be an attractive alternative to PEG in the search for protein shields that minimize the immunogenicity of PEGylated proteins.

Mitigating the Effects of Persistent Antipolymer Immune Reactions in Nanomedicine: Evaluating Materials-Based Approaches Using Molecular Imaging

Poly(ethylene glycol) (PEG) is a hydrophilic polymer ubiquitously used in both medical and nonmedical goods. Recent debate surrounding the observed stimulation of immune responses against PEG has spurred the development of materials that may be suitable replacements for this common polymeric component. The underlying view is that these alternative materials with comparable physicochemical properties can overcome the unfavorable and unpredictable effects of antibody-mediated clearance by being chemically, and therefore antigenically, distinct from PEG. However, this hypothesis has not been thoroughly tested in any defined manner, and the immune response observed against PEG has not been rigorously investigated within the context of these emerging materials. Consequently, it remains unclear whether immunity-mediated discrimination between polymeric entities even occurs in vivo and, if this is the case, how it may be exploited. In this study, we utilize positron emission tomography-computed tomography molecular imaging in mice immunized to develop specific antibody responses to PEG and an alternative polymer in order to visualize and quantify the influence of antipolymer antibodies on the biodistribution of synthetic polymers in vivo as a function of immunization status. Under the conditions of this experiment, mice could be primed to exhibit both innate and adaptive immunity to all of the polymer systems to which they were exposed. We demonstrate that alternating between chemically disparate polymers is a viable approach to extend their efficacy when antipolymer humoral immune responses arise.

Kupffer cells determine intrahepatic traffic of PEGylated liposomal doxorubicin

Intrahepatic accumulation dominates organ distribution for most nanomedicines. However, obscure intrahepatic fate largely hampers regulation on their in vivo performance. Herein, PEGylated liposomal doxorubicin is exploited to clarify the intrahepatic fate of both liposomes and the payload in male mice. Kupffer cells initiate and dominate intrahepatic capture of liposomal doxorubicin, following to deliver released doxorubicin to hepatocytes with zonated distribution along the lobule porto-central axis. Increasing Kupffer cells capture promotes doxorubicin accumulation in hepatocytes, revealing the Kupffer cells capture-payload release-hepatocytes accumulation scheme. In contrast, free doxorubicin is overlooked by Kupffer cells, instead quickly distributing into hepatocytes by directly crossing fenestrated liver sinusoid endothelium. Compared to free doxorubicin, liposomal doxorubicin exhibits sustained metabolism/excretion due to the extra capture-release process. This work unveils the pivotal role of Kupffer cells in intrahepatic traffic of PEGylated liposomal therapeutics, and quantitively describes the intrahepatic transport/distribution/elimination process, providing crucial information for guiding further development of nanomedicines.

Reciprocal Interaction with Neutrophils Facilitates Cutaneous Accumulation of Liposomes

Liposomes are versatile drug delivery systems in clinical use for cancer and many other diseases. Unfortunately, PEGylated liposomal doxorubicin (sLip/DOX) exhibits serious dose-limiting cutaneous toxicities, which are closely related to the extravascular accumulation of sLip/DOX in the dermis. No clinical interventions have been proposed for cutaneous toxicities due to the elusive transport pathways. Herein, we showed that the reciprocal interaction between liposomes and neutrophils played pivotal roles in liposome extravasation into the dermis. Neutrophils captured liposomes via the complement receptor 3 (CD11b/CD18) recognizing the fragment of complement component C3 (iC3b) deposited on the liposomal surface. Uptake of liposomes also activated neutrophils to induce CD11b upregulation and enhanced the ability of neutrophils to migrate outside the capillaries. Furthermore, inhibition of complement activation either by CRIg-L-FH (a C3b/iC3b targeted complement inhibitor) or blocking the phosphate negative charge in mPEG-DSPE could significantly reduce liposome uptake by neutrophils and alleviate the cutaneous accumulation of liposomes. These results validated the liposome extravasation pathway mediated by neutrophils and provided potential solutions to the devastating cutaneous toxicities occurring during sLip/DOX treatment.

Engineering LNPs with polysarcosine lipids for mRNA delivery

Since the approval of the lipid nanoparticles (LNP)-mRNA vaccines against the SARS-CoV-2 virus, there has been an increased interest in the delivery of mRNA through LNPs. However, current LNP formulations contain PEG lipids, which can stimulate the generation of anti-PEG antibodies. The presence of these antibodies can potentially cause adverse reactions and reduce therapeutic efficacy after administration. Given the widespread deployment of the COVID-19 vaccines, the increased exposure to PEG may necessitate the evaluation of alternative LNP formulations without PEG components. In this study, we investigated a series of polysarcosine (pSar) lipids as alternatives to the PEG lipids to determine whether pSar lipids could still provide the functionality of the PEG lipids in the ALC-0315 and SM-102 LNP systems. We found that complete replacement of the PEG lipid with a pSar lipid can increase or maintain mRNA delivery efficiency and exhibit similar safety profiles in vivo.

Broadly Applicable Bispecific Linker Approach to Noncovalently Target Therapeutic Nanoparticles to Tumor Cells Expressing Carcinoembryonic Antigen

Design strategies that lead to a more focused in vivo delivery of functionalized nanoparticles (NPs) and their cargo can potentially maximize their therapeutic efficiency while reducing systemic effects, broadening their clinical applications. Here, we report the development of a noncovalent labeling approach where immunoglobulin G (IgG)-decorated NPs can be directed to a cancer cell using a simple, linear bispecific protein adaptor, termed MFE23-ZZ. MFE23-ZZ was created by fusing a single-chain fragment variable domain, termed MFE23, recognizing carcinoembryonic antigen (CEA) expressed on tumor cells, to a small protein ZZ module, which binds to the Fc fragment of IgG. As a proof of concept, monoclonal antibodies (mAbs) were generated against a NP coat protein, namely, gas vesicle protein A (GvpA) of Halobacterium salinarum gas vesicles (GVs). The surface of each GV was therapeutically derivatized with the photoreactive agent chlorin e6 (Ce6GVs) and anti-GvpA mAbs were subsequently bound to GvpA on the surface of each Ce6GV. The bispecific ligand MFE23-ZZ was then bound to mAb-decorated Ce6GVs via their Fc domain, resulting in a noncovalent tripartite complex, namely, MFE23.ZZ-2B10-Ce6GV. This complex enhanced the intracellular uptake of Ce6GVs into human CEA-expressing murine MC38 colon carcinoma cells (MC38.CEA) relative to the CEA-negative parental cell line MC38 in vitro, making them more sensitive to light-induced cell killing. These results suggest that the surface of NP can be rapidly and noncovalently functionalized to target tumor-associated antigen-expressing tumor cells using simple bispecific linkers and any IgG-labeled cargo. This noncovalent approach is readily applicable to other types of functionalized NPs.

Mechanisms and Barriers in Nanomedicine: Progress in the Field and Future Directions

In recent years, steady progress has been made in synthesizing and characterizing engineered nanoparticles, resulting in several approved drugs and multiple promising candidates in clinical trials. Regulatory agencies such as the Food and Drug Administration and the European Medicines Agency released important guidance documents facilitating nanoparticle-based drug product development, particularly in the context of liposomes and lipid-based carriers. Even with the progress achieved, it is clear that many barriers must still be overcome to accelerate translation into the clinic. At the recent conference workshop "Mechanisms and Barriers in Nanomedicine" in May 2023 in Colorado, U.S.A., leading experts discussed the formulation, physiological, immunological, regulatory, clinical, and educational barriers. This position paper invites open, unrestricted, nonproprietary discussion among senior faculty, young investigators, and students to trigger ideas and concepts to move the field forward.

Optimized Enzyme-Linked Immunosorbent Assay for Anti-PEG Antibody Detection in Healthy Donors and Patients Treated with PEGylated Liposomal Doxorubicin

There is considerable interest in quantifying anti-PEG antibodies, given their potential involvement in accelerated clearance, complement activation, neutralization, and acute reactions associated with drug delivery systems. Published and commercially available anti-PEG enzyme-linked immunosorbent assays (ELISAs) differ significantly in terms of reagents and conditions, which could be confusing to users who want to perform in-house measurements. Here, we optimize the ELISA protocol for specific detection of anti-PEG IgG and IgM in sera from healthy donors and in plasma from cancer patients administered with PEGylated liposomal doxorubicin. The criterion of specificity is the ability of free PEG or PEGylated liposomes to inhibit the ELISA signals. We found that coating high-binding plates with monoamine methoxy-PEG5000, as opposed to bovine serum albumin-PEG20000, and blocking with 1% milk, as opposed to albumin or lysozyme, significantly improve the specificity, with over 95% of the signal being blocked by competition. Despite inherent between-assay variability, setting the cutoff value of the optical density at the 80th percentile consistently identified the same subjects. Using the optimized assay, we longitudinally measured levels of anti-PEG IgG/IgM in cancer patients before and after the PEGylated liposomal doxorubicin chemotherapy cycle (1 month apart, three cycles total). Antibody titers did not show any increase but rather a decrease between treatment cycles, and up to 90% of antibodies was bound to the infused drug. This report is a step toward harmonizing anti-PEG assays in human subjects, emphasizing the cost-effectiveness and optimized specificity.

Humoral immune response against SARS-CoV-2 and polyethylene glycol elicited by anti-SARS-CoV-2 mRNA vaccine, and effect of pre-existing anti-polyethylene glycol antibody in patients with hematological and autoimmune diseases

Background

The effects of vaccination are modified by hematological and autoimmune diseases and/or treatment. Anti-SARS-CoV-2 mRNA vaccine contains polyethylene glycol (PEG), it is largely unknown whether PEG influences the effects of vaccination or induces a humoral response. This study examined whether anti-PEG antibodies before vaccination (pre-existing) influenced the acquisition of SARS-CoV-2 antibodies and evaluated the relationship between the development of anti-SARS-CoV-2 antibodies and anti-PEG antibodies after SARS-CoV-2 vaccination in hematological and autoimmune diseases.

Methods

Anti-SARS-CoV-2 antibody IgG, anti-PEG IgG, and IgM titers were evaluated in patients with hematological and autoimmune diseases after the second dose of BNT162B2. Anti-PEG IgG and IgM titers were also measured before vaccination to examine changes after vaccination and the relationship with vaccine efficacy.

Results

In patients with hematological (n = 182) and autoimmune diseases (n = 96), anti-SARS-CoV-2 and anti-PEG antibody titers were evaluated after a median of 33 days from 2nd vaccination. The median anti-SARS-CoV-2 antibody titers were 1901 AU/mL and 3832 AU/mL in patients with hematological and autoimmune disease, respectively. Multiple regression analysis showed that age and days from 2nd vaccination were negatively associated with anti-SARS-CoV-2 antibody titers. Anti-CD20 antibody treatment was negatively correlated with anti-SARS-CoV-2 antibody titers in hematological disease, and C-reactive protein (CRP) was positively correlated with anti-SARS-CoV-2 antibody titers in autoimmune disease. Baseline anti-PEG antibody titers were significantly higher in patients with autoimmune disease but were not correlated with anti-SARS-CoV-2 antibody titers. Patients with increased anti-PEG IgG acquired higher anti-SARS-CoV-2 antibody titers in patients with autoimmune disease.

Conclusions

Anti-SARS-CoV-2 antibody acquisition was suboptimal in patients with hematological disease, but both anti-SARS-CoV-2 antibody and anti-PEG IgG were acquired in patients with autoimmune disease, reflecting robust humoral immune response. Pre-existing anti-PEG antibody titers did not affect anti-SARS-CoV-2 antibody acquisition.

Facts and Hopes on Chimeric Cytokine Agents for Cancer Immunotherapy

Cytokines are key mediators of immune responses that can modulate the antitumor activity of immune cells. Cytokines have been explored as a promising cancer immunotherapy. However, there are several challenges to cytokine therapy, especially a lack of tumor targeting, resulting in high toxicity and limited efficacy. To overcome these limitations, novel approaches have been developed to engineer cytokines with improved properties, such as chimeric cytokines. Chimeric cytokines are fusion proteins that combine different cytokine domains or link cytokines to antibodies (immunocytokines) or other molecules that can target specific receptors or cells. Chimeric cytokines can enhance the selectivity and stability of cytokines, leading to reduced toxicity and improved efficacy. In this review, we focus on two promising cytokines, IL2 and IL15, and summarize the current advances and challenges of chimeric cytokine design and application for cancer immunotherapy. Most of the current approaches focus on increasing the potency of cytokines, but another important goal is to reduce toxicity. Cytokine engineering is promising for cancer immunotherapy as it can enhance tumor targeting while minimizing adverse effects.

Physiological Barriers and Strategies of Lipid-Based Nanoparticles for Nucleic Acid Drug Delivery

Lipid-based nanoparticles (LBNPs) are currently the most promising vehicles for nucleic acid drug (NAD) delivery. Although their clinical applications have achieved success, the NAD delivery efficiency and safety are still unsatisfactory, which are, to a large extent, due to the existence of multi-level physiological barriers in vivo. It is important to elucidate the interactions between these barriers and LBNPs, which will guide more rational design of efficient NAD vehicles with low adverse effects and facilitate broader applications of nucleic acid therapeutics. This review describes the obstacles and challenges of biological barriers to NAD delivery at systemic, organ, sub-organ, cellular, and subcellular levels. The strategies to overcome these barriers are comprehensively reviewed, mainly including physically/chemically engineering LBNPs and directly modifying physiological barriers by auxiliary treatments. Then the potentials and challenges for successful translation of these preclinical studies into the clinic are discussed. In the end, a forward look at the strategies on manipulating protein corona (PC) is addressed, which may pull off the trick of overcoming those physiological barriers and significantly improve the efficacy and safety of LBNP-based NADs delivery.

Impact of PEG sensitization on the efficacy of PEG hydrogel-mediated tissue engineering

While poly(ethylene glycol) (PEG) hydrogels are generally regarded as biologically inert blank slates, concerns over PEG immunogenicity are growing, and the implications for tissue engineering are unknown. Here, we investigate these implications by immunizing mice against PEG to stimulate anti-PEG antibody production and evaluating bone defect regeneration after treatment with bone morphogenetic protein-2-loaded PEG hydrogels. Quantitative analysis reveals that PEG sensitization increases bone formation compared to naive controls, whereas histological analysis shows that PEG sensitization induces an abnormally porous bone morphology at the defect site, particularly in males. Furthermore, immune cell recruitment is higher in PEG-sensitized mice administered the PEG-based treatment than their naive counterparts. Interestingly, naive controls that were administered a PEG-based treatment also develop anti-PEG antibodies. Sex differences in bone formation and immune cell recruitment are also apparent. Overall, these findings indicate that anti-PEG immune responses can impact tissue engineering efficacy and highlight the need for further investigation.

The Role of Biological Sex in Pre-Clinical (Mouse) mRNA Vaccine Studies

In this study, we consider the influence of biological sex-specific immune responses on the assessment of mRNA vaccines in pre-clinical murine studies. Recognising the established disparities in immune function attributed to genetic and hormonal differences between individuals of different biological sexes, we compared the mRNA expression and immune responses in mice of both biological sexes after intramuscular injection with mRNA incorporated within lipid nanoparticles. Regarding mRNA expression, no significant difference in protein (luciferase) expression at the injection site was observed between female and male mice following intramuscular administration; however, we found that female BALB/c mice exhibit significantly greater total IgG responses across the concentration range of mRNA lipid nanoparticles (LNPs) in comparison to their male counterparts. This study not only contributes to the scientific understanding of mRNA vaccine evaluation but also emphasizes the importance of considering biological sex in vaccine study designs during pre-clinical evaluation in murine studies.

Reexamining the effects of drug loading on the in vivo performance of PEGylated liposomal doxorubicin

Higher drug loading employed in nanoscale delivery platforms is a goal that researchers have long sought after. But such viewpoint remains controversial because the impacts that nanocarriers bring about on bodies have been seriously overlooked. In the present study we investigated the effects of drug loading on the in vivo performance of PEGylated liposomal doxorubicin (PLD). We prepared PLDs with two different drug loading rates: high drug loading rate, H-Dox, 12.9% w/w Dox/HSPC; low drug loading rate, L-Dox, 2.4% w/w Dox/HSPC (L-Dox had about 5 folds drug carriers of H-Dox at the same Dox dose). The pharmaceutical properties and biological effects of H-Dox and L-Dox were compared in mice, rats or 4T1 subcutaneous tumor-bearing mice. We showed that the lowering of doxorubicin loading did not cause substantial shifts to the pharmaceutical properties of PLDs such as in vitro and in vivo stability (stable), anti-tumor effect (equivalent effective), as well as tissue and cellular distribution. Moreover, it was even more beneficial for mitigating the undesired biological effects caused by PLDs, through prolonging blood circulation and alleviating cutaneous accumulation in the presence of pre-existing anti-PEG Abs due to less opsonins (e.g. IgM and C3) deposition on per particle. Our results warn that the effects of drug loading would be much more convoluted than expected due to the complex intermediation between nanocarriers and bodies, urging independent investigation for each individual delivery platform to facilitate clinical translation and application.

Treatment-induced and Pre-existing Anti-peg Antibodies: Prevalence, Clinical Implications, and Future Perspectives

Polyethylene glycol (PEG) is a versatile polymer that is used in numerous pharmaceutical applications like the food industry, a wide range of disinfectants, cosmetics, and many commonly used household products. PEGylation is the term used to describe the covalent attachment of PEG molecules to nanocarriers, proteins and peptides, and it is used to prolong the circulation half-life of the PEGylated products. Consequently, PEGylation improves the efficacy of PEGylated therapeutics. However, after four decades of research and more than two decades of clinical applications, an unappealing side of PEGylation has emerged. PEG immunogenicity and antigenicity are remarkable challenges that confound the widespread clinical application of PEGylated therapeutics - even those under clinical trials - as anti-PEG antibodies (Abs) are commonly reported following the systemic administration of PEGylated therapeutics. Furthermore, pre-existing anti-PEG Abs have also been reported in healthy individuals who have never been treated with PEGylated therapeutics. The circulating anti-PEG Abs, both treatment-induced and pre-existing, selectively bind to PEG molecules of the administered PEGylated therapeutics inducing activation of the complement system, which results in remarkable clinical implications with varying severity. These include increased blood clearance of the administered PEGylated therapeutics through what is known as the accelerated blood clearance (ABC) phenomenon and initiation of serious adverse effects through complement activation-related pseudoallergic reactions (CARPA). Therefore, the US FDA industry guidelines have recommended the screening of anti-PEG Abs, in addition to Abs against PEGylated proteins, in the clinical trials of PEGylated protein therapeutics. In addition, strategies revoking the immunogenic response against PEGylated therapeutics without compromising their therapeutic efficacy are important for the further development of advanced PEGylated therapeutics and drug-delivery systems.

Engineering approaches for innate immune-mediated tumor microenvironment remodeling

Cancer immunotherapy offers transformative promise particularly for the treatment of lethal cancers, since a correctly trained immune system can comprehensively orchestrate tumor clearance with no need for continued therapeutic intervention. Historically, the majority of immunotherapies have been T cell-focused and have included immune checkpoint inhibitors, chimeric antigen receptor T cells, and T-cell vaccines. Unfortunately T-cell-focused therapies have failed to achieve optimal efficacy in most solid tumors largely because of a highly immunosuppressed 'cold' or immune-excluded tumor microenvironment (TME). Recently, a rapidly growing treatment paradigm has emerged that focuses on activation of tumor-resident innate antigen-presenting cells, such as dendritic cells and macrophages, which can drive a proinflammatory immune response to remodel the TME from 'cold' or immune-excluded to 'hot'. Early strategies for TME remodeling centered on free cytokines and agonists, but these approaches have faced significant hurdles in both delivery and efficacy. Systemic toxicity from off-target inflammation is a paramount concern in these therapies. To address this critical gap, engineering approaches have provided the opportunity to add 'built-in' capabilities to cytokines, agonists, and other therapeutic agents to mediate improved delivery and efficacy. Such capabilities have included protective encapsulation to shield them from degradation, targeting to direct them with high specificity to tumors, and co-delivery strategies to harness synergistic proinflammatory pathways. Here, we review innate immune-mediated TME remodeling engineering approaches that focus on cytokines, innate immune agonists, immunogenic viruses, and cell-based methods, highlighting emerging preclinical approaches and strategies that are either being tested in clinical trials or already Food and Drug Administration approved.

Study of uricase-polynorbornene conjugates derived from grafting-from ring-opening metathesis polymerization

PEGylation has been the 'gold standard' in bioconjugation due to its ability to improve the pharmacokinetics and pharmacodynamics of native proteins. However, growing clinical evidence of hypersensitivity reactions to PEG due to pre-existing anti-PEG antibodies in healthy humans have raised concerns. Advancements in controlled polymerization techniques and conjugation chemistries have paved the way for the development of protein-polymer conjugates that can circumvent these adverse reactions while retaining the benefits of such modifications. Herein, we show the development of polynorbornene based bioconjugates of therapeutically relevant urate oxidase (UO) enzymes used in the treatment of gout synthesized by grafting-from ring-opening metathesis polymerization (ROMP). Notably, these conjugates exhibit comparable levels of bioactivity to PEGylated UO and demonstrate increased stability across varying temperatures and pH conditions. Immune recognition of conjugates by anti-UO antibodies reveal low protein immunogenicity following the conjugation process. Additionally, UO conjugates employing zwitterionic polynorbornene successfully avoid recognition by anti-PEG antibodies, further highlighting a potential replacement for PEG.

Impact of Anti-PEG IgM Induced via the Topical Application of a Cosmetic Product Containing PEG Derivatives on the Antitumor Effects of PEGylated Liposomal Antitumor Drug Formulations in Mice

Poly(ethylene glycol) (PEG) is used in many common products, such as cosmetics. PEG, however, is also used to covalently conjugate drug molecules, proteins, or nanocarriers, which is termed PEGylation, to serve as a shield against the natural immune system of the human body. Repeated administration of some PEGylated products, however, is known to induce anti-PEG antibodies. In addition, preexisting anti-PEG antibodies are now being detected in healthy individuals who have never received PEGylated therapeutics. Both treatment-induced and preexisting anti-PEG antibodies alter the pharmacokinetic properties, which can result in a subsequent reduction in the therapeutic efficacy of administered PEGylated therapeutics through the so-called accelerated blood clearance (ABC) phenomenon. Moreover, these anti-PEG antibodies are widely reported to be related to severe hypersensitivity reactions following the administration of PEGylated therapeutics, including COVID-19 vaccines. We recently reported that the topical application of a cosmetic product containing PEG derivatives induced anti-PEG immunoglobulin M (IgM) in a mouse model. Our finding indicates that the PEG derivatives in cosmetic products could be a major cause of the preexistence of anti-PEG antibodies in healthy individuals. In this study, therefore, the pharmacokinetics and therapeutic effects of Doxil (doxorubicin hydrochloride-loaded PEGylated liposomes) and oxaliplatin-loaded PEGylated liposomes (Liposomal l-OHP) were studied in mice. The anti-PEG IgM antibodies induced by the topical application of cosmetic products obviously accelerated the blood clearance of both PEGylated liposomal formulations. Moreover, in C26 tumor-bearing mice, the tumor growth suppressive effects of both Doxil and Liposomal l-OHP were significantly attenuated in the presence of anti-PEG IgM antibodies induced by the topical application of cosmetic products. These results confirm that the topical application of a cosmetic product containing PEG derivatives could produce preexisting anti-PEG antibodies that then affect the therapeutic efficacy of subsequent doses of PEGylated therapeutics.

Poly(Oxanorbornene)-Protein Conjugates Prepared by Grafting-to ROMP as Alternatives for PEG

PEGylation is the gold standard in protein-polymer conjugation, improving circulation half-life of biologics while mitigating the immune response to a foreign substance. However, preexisting anti-PEG antibodies in healthy humans are becoming increasingly prevalent and elicitation of anti-PEG antibodies when patients are administered with PEGylated therapeutics challenges their safety profile. In the current study, two distinct amine-reactive poly(oxanorbornene) (PONB) imide-based water-soluble block co-polymers are synthesized using ring-opening metathesis polymerization (ROMP). The synthesized block-copolymers include PEG-based PONB-PEG and sulfobetaine-based PONB-Zwit. The polymers are then covalently conjugated to amine residues of lysozyme (Lyz) and urate oxidase (UO) using a grafting-to bioconjugation technique. Both Lyz-PONB and UO-PONB conjugates retained significant bioactivities after bioconjugation. Immune recognition studies of UO-PONB conjugates indicated a comparable lowering of protein immunogenicity when compared to PEGylated UO. PEG-specific immune recognition is negligible for UO-PONB-Zwit conjugates, as expected. These polymers provide a new alternative for PEG-based systems that retain high levels of activity for the biologic while showing improved immune recognition profiles.

PEGylated therapeutics in the clinic

The covalent attachment of polyethylene glycol (PEG) to therapeutic agents, termed PEGylation, is a well-established and clinically proven drug delivery approach to improve the pharmacokinetics and pharmacodynamics of drugs. Specifically, PEGylation can improve the parent drug's solubility, extend its circulation time, and reduce its immunogenicity, with minimal undesirable properties. PEGylation technology has been applied to various therapeutic modalities including small molecules, aptamers, peptides, and proteins, leading to over 30 PEGylated drugs currently used in the clinic and many investigational PEGylated agents under clinical trials. Here, we summarize the diverse types of PEGylation strategies, the key advantages of PEGylated therapeutics over their parent drugs, and the broad applications and impacts of PEGylation in clinical settings. A particular focus has been given to the size, topology, and functionalities of PEG molecules utilized in clinically used PEGylated drugs, as well as those under clinical trials. An additional section has been dedicated to analyzing some representative PEGylated drugs that were discontinued at different stages of clinical studies. Finally, we critically discuss the current challenges faced in the development and clinical translation of PEGylated agents.

Zwitterionic Polymer-Decorated Lipid Nanoparticles for mRNA Delivery in Mammalian Cells

Lipid nanoparticles (LNPs) play a key role in the effective transport of mRNA into cells for protein translation. Despite the stealthiness of poly(ethylene glycol) (PEG) that helps protect LNPs from protein absorption and blood clearance, the generation of anti-PEG antibodies resulting in PEG allergies remains a challenge for the development of an mRNA vaccine. Herein, a non-PEG lipid was developed by conjugating 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) with an antifouling zwitterionic polymer, poly(2-methyacryloyloxyethyl phosphorylcholine) (PMPC), of different chain lengths. The PMPC-LNPs formulated from DPPE-PMPC were spherical (diameter ≈ 144-255 nm), neutral in charge, and stable at 4 °C for up to 28 days. Their fraction of stealthiness being close to 1 emphasized the antifouling characteristics of PMPC decorated on LNPs. The PMPC-LNPs were nontoxic to HEK293T cells, did not induce inflammatory responses in THP-1 cells, and exhibited an mRNA transfection efficiency superior to that of PEG-LNPs. This work demonstrated the potential of the developed zwitterionic polymer-conjugated LNPs as promising mRNA carriers.

Interactions between nanoparticle corona proteins and the immune system

The corona surrounding nanoparticles (NPs) in serum contains proteins such as complement, immunoglobulins, and apolipoproteins that can interact with the immune system. This review article describes the impact of these interactions on nanomedicine stability, biodistribution, efficacy, and safety. Notably, it highlights the latest findings on the generation of antibody responses to the polyethylene glycol (PEG) component of SARS-CoV-2 mRNA vaccines and possible mechanisms of hypersensitivity reactions induced by antibodies that bind to NPs. Finally, we briefly outline how the NP interactions with immune cells can be harnessed to enhance targeted delivery of nanocargos to disease sites.

Polyethylene glycol (PEG)-associated immune responses triggered by clinically relevant lipid nanoparticles in rats

With the large-scale vaccination of lipid nanoparticles (LNP)-based COVID-19 mRNA vaccines, elucidating the potential polyethylene glycol (PEG)-associated immune responses triggered by clinically relevant LNP has become imminent. However, inconsistent findings were observed across very limited population-based studies. Herein we initiated a study using LNP carrier of Comirnaty® as a representative, and simulated real-world clinical practice covering a series of time points and various doses correlated with approved LNP-delivered drugs in a rat model. We demonstrated the time- and dose-dependency of LNP-induced anti-PEG antibodies in rats. As a thymus-independent antigen, LNP unexpectedly induced isotype switch and immune memory, leading to rapid enhancement and longer lasting time of anti-PEG IgM and IgG upon re-injection in rats. Importantly, initial LNP injection accelerated the blood clearance of subsequent dosing in rats. These findings refine our understandings on LNP and possibly other PEG derivatives, and may promote optimization of related premarket guidelines and clinical protocols.

Accelerated blood clearance of PEGylated nanoparticles induced by PEG-based pharmaceutical excipients

PEGylated nanomedicines have been extensively developed and applied to cancer therapy. However, the antitumor efficacy of these nanoparticles is hampered by the accelerated blood clearance (ABC) effect caused by anti-PEG antibodies in vivo. There is still limited understanding about the cause of pre-existing anti-PEG antibodies in the human body. Herein, we discovered that PEG-based pharmaceutical excipients, commonly used in clinical and daily settings, could induce anti-PEG antibodies in vivo and lead to considerable potential clinical impacts on pharmacokinetics and pharmacodynamics of PEGylated nanoparticles. Specifically, we investigated the ability of poloxamer 188 (F68) and poloxamer 407 (F127), the two most frequently used PEG-based pharmaceutical excipients, to elicit the production of anti-PEG antibodies and influence the pharmacokinetics of PEGylated nanoparticles, with PEGylated liposome nanoparticles (L-NPs) as a model. Anti-PEG IgG and IgM levels were significantly boosted 3.8- and 32.2-fold, respectively, after pre-injection with F68, leading to rapid clearance of subsequently injected L-NPs from circulation due to the capture by neutrophils and monocytes. However, pre-injection of F127 did not induce the production of anti-PEG IgG, although there was a 7.7-fold increase in IgM level, which resulted in minimal effect on circulation time of L-NPs. Furthermore, the potential clinical impacts of F68 and F127 were further inspected for PEGylated liposomal doxorubicin (PLD). It was found that administering F68 prior to treatment led to over a one-third decrease in the antitumor effectiveness of PLD, while F127 had a negligible impact. Our study elucidates the mechanism by which PEG-based pharmaceutical excipients influence the effectiveness of PEGylated nanomedicines. It also highlights the significance of considering the potential for an ABC effect induced by PEG-based pharmaceutical excipients in patients.

Protein corona on brain targeted nanocarriers: Challenges and prospects

Safe and efficient medical therapy for brain diseases is still an unmet clinical need due to various barriers represented by the blood-brain barrier. Well-designed brain targeted nanocarriers are potential solutions for enhanced brain drug delivery; however, the complicated in vivo process attenuates performance of nanocarriers, which severely hampers clinical translation. The formation of protein corona (PC) is inevitable for nanocarriers circulation and transport in biofluids, acting as an important factor to regulate in vivo performance of nanocarriers. In this review, the reported strategies have been retrospected for better understanding current situation in developing brain targeted nanocarriers. The interplay between brain targeted nanocarriers and plasma proteins is emphasized to comprehend how the nanocarriers adsorb proteins by certain synthetic identity, and following regulations on in vivo performance of nanocarriers. More importantly, the mainstream methods to promote efficiency of nanocarriers by regulating PC, defined as in vitro functionalization and in vivo functionalization strategies, are also discussed. Finally, viewpoints about future development of brain targeted nanocarriers according to the understanding on nanocarriers-PC interaction are proposed.

Cases of less-than-expected FVIII activity in previously treated patients during post-marketing surveillance of N8-GP

INTRODUCTION

Turoctocog alfa pegol (N8-GP) is a glycoPEGylated, extended half-life (EHL), human recombinant factor VIII (FVIII) approved for the treatment and prevention of bleeding episodes in patients with haemophilia A. Since its launch in August 2019, > 800 patients have been treated worldwide.

AIM

To present data from identified post-marketing cases of less-than-expected FVIII activity in previously treated patients (PTPs) without inhibitors after switching to N8-GP.

METHODS

The post-marketing safety database was searched using keywords such as 'coagulation FVIII level decreased'. Identified cases reported prior to 13 October 2021 were included in this report. Cases in which patients had FVIII inhibitors were excluded.

RESULTS

Here we report 14 cases of less-than-expected FVIII activity. Details varied greatly amongst the cases. At presentation, FVIII activity ranged from 1% (15 min post-dose) to 51% (2 days post-dose). Seven patients experienced bleeding episodes after switching to N8-GP with heterogeneity in bleeding presentations. Six out of seven patients who were tested for anti-PEG IgG and/or IgM antibodies were positive. In all known cases, FVIII activity returned to the expected range when switched to an alternative FVIII replacement product.

CONCLUSION

In conclusion, the 14 reported cases of less-than-expected FVIII activity, without presence of detectable FVIII inhibitors, presented with heterogenous characteristics, and wide variations in FVIII activity and anti-PEG antibody titre. FVIII activity returned to the expected range after switching to alternative FVIII products. In line with WFH guidelines, monitoring of FVIII activity can ensure FVIII activity in the expected range. The safety surveillance of N8-GP continues.

Gout therapeutics and drug delivery

Gout is a common inflammatory arthritis caused by persistently elevated uric acid levels. With the improvement of people's living standards, the consumption of processed food and the widespread use of drugs that induce elevated uric acid, gout rates are increasing, seriously affecting the human quality of life, and becoming a burden to health systems worldwide. Since the pathological mechanism of gout has been elucidated, there are relatively effective drug treatments in clinical practice. However, due to (bio)pharmaceutical shortcomings of these drugs, such as poor chemical stability and limited ability to target the pathophysiological pathways, traditional drug treatment strategies show low efficacy and safety. In this scenario, drug delivery systems (DDS) design that overcome these drawbacks is urgently called for. In this review, we initially describe the pathological features, the therapeutic targets, and the drugs currently in clinical use and under investigation to treat gout. We also comprehensively summarize recent research efforts utilizing lipid, polymeric and inorganic carriers to develop advanced DDS for improved gout management and therapy.

Anti-PEG antibodies enriched in the protein corona of PEGylated nanocarriers impact the cell uptake

Poly(ethylene glycol) (PEG) is the gold standard used to reduce unspecific protein adsorption and prolong nanocarrier circulation time. However, this stealth effect could be counteracted by the increasing prevalence of anti-PEG antibodies in the bloodstream. Up to now, the presence of anti-PEG antibodies in the protein corona and their effect on cell uptake has not been investigated yet. Our results showed a high concentration and prevalence of anti-PEG antibodies in the German population. PEGylated nanocarriers exhibited a higher level of anti-PEG antibodies in the protein corona compared to non-PEGylated, which lead to higher uptake in macrophages. Consequently, the anti-PEG antibodies in the protein corona could mitigate the stealth effect of PEG, leading to accelerated blood clearance and unwanted side effects.

Characterization of pre-existing anti-PEG and anti-AGAL antibodies towards PRX-102 in patients with Fabry disease

Polyethylene glycol (PEG)ylated drugs are used for medical treatment, since PEGylation either decreases drug clearance or/and shields the protein from undesirable immunogenicity. PEGylation was implemented in a new enzyme replacement therapy for Fabry disease (FD), pegunigalsidase-alfa (PRX-102). However, exposure to PEG via life-style products and vaccination can result in the formation of anti-PEG antibodies. We demonstrate the de novo formation of functional anti-PEG antibodies in a healthy male after the second mRNA-based vaccination against SARS-CoV-2. Consequently, we analyzed the frequency and inhibitory function of anti-PEG and anti-α-Galactosidase A (AGAL) antibodies in 102 FD patients (46.9% males). We identified 29 out of 87 (33.3%) patients with low anti-PEG titers. Sera from patients without anti-AGAL antibodies [n=70] showed a higher rescued AGAL activity of agalsidase-beta and PRX-102 [both p<0.0001] compared to those with anti-AGAL antibodies [n=15]. Sera from anti-AGAL antibody-negative and -positive patients had less inhibitory effects on PRX-102 (rescued activity: 89 ± 6% versus 85 ± 7% and 49 ± 26% versus 25 ± 32%; both p<0.0001). Enzyme stability assays demonstrated that AUCs in anti-AGAL-negative sera (n=20) were 7.6-fold higher for PRX-102, while AUCs of both enzymes in anti-AGAL-positive sera (n=6) were decreased. However, AUC for PRX-102 was 33% of non-anti-AGAL-positive sera treated PRX-102 and 5-fold higher compared to agalsidase-beta. Anti-PEG antibodies had no significant effects on serum half-life of PRX-102, probably due to low titers. Conceivably, therapy efficacy may be superior under next-generation PRX-102 therapy compared to current enzyme replacement therapies in terms of reduced inhibitory effects of anti-AGAL and minor inhibitory effects of anti-PEG antibodies.

Poly(2-ethyl-2-oxazoline)-Conjugated Hemoglobins as a Red Blood Cell Substitute

Hemoglobin wrapped covalently with poly(2-ethyl-2-oxazoline)s (POx-Hb) is characterized physicochemically and physiologically as an artificial O2 carrier for use as a red blood cell (RBC) substitute. The POx-Hb is generated by linkage of porcine Hb surface-lysines to a sulfhydryl terminus of the POx derivative, with the average binding number of the polymers ascertained as 6. The POx-Hb shows moderately higher colloid osmotic activity and O2 affinity than the naked Hb. Human adult HbA conjugated with POx also possesses equivalent features and O2 binding properties. The POx-Hb solution exhibits good hemocompatibility, with no influence on the functions of platelets, granulocytes, and monocytes. Its circulation half-life in rats is 14 times longer than that of naked Hb. Hemorrhagic shock in rats is relieved sufficiently by infusion of the POx-Hb solution, as revealed by improvements of circulatory parameters. Serum biochemistry tests and histopathological observations indicate no acute toxicity or abnormality in the related organs. All results indicate that POx-Hb represents an attractive alternative for RBCs and a useful O2 therapeutic reagent in transfusion medicine.

Dose-Dependent Production of Anti-PEG IgM after Intramuscular PEGylated-Hydrogenated Soy Phosphatidylcholine Liposomes, but Not Lipid Nanoparticle Formulations of DNA, Correlates with the Plasma Clearance of PEGylated Liposomal Doxorubicin in Rats

PEGylated lipid nanoparticle-based Covid-19 vaccines, including Pfizer's BNT162b2 and Moderna's mRNA-1273, have been shown to stimulate variable anti-PEG antibody production in humans. Anti-PEG antibodies have the potential to accelerate the plasma clearance of PEGylated therapeutics, such as PEGylated liposomes and proteins, and compromise their therapeutic efficacy. However, it is not yet clear whether antibody titers produced by PEGylated Covid-19 vaccines significantly affect the clearance of PEGylated therapeutics. This study examined how anti-PEG IgM levels affect the pharmacokinetics of PEGylated liposomal doxorubicin (PLD) and compared the immunogenicity of a lipid nanoparticle formulation of linear DNA (DNA-LNP) to standard PEG-HSPC liposomes. DNA-LNP was prepared using the same composition and approach as Pfizer's BNT162b2, except linear double-stranded DNA was used as the genetic material. PEGylated HSPC-based liposomes were formulated using the lipid rehydration and extrusion method. Nanoparticles were dosed IM to rats at 0.005-0.5 mg lipid/kg body weight 1 week before evaluating the plasma pharmacokinetics of clinically relevant doses of PLD (1 mg/kg, IV) or PEGylated interferon α2a (Pegasys, 5 μg/kg, SC). Plasma PEG IgM was compared between pre- and 1-week post-dose blood samples. The results showed that anti-PEG IgM production increased with increasing PEG-HSPC liposome dose and that IgM significantly correlated with the plasma half-life, clearance, volume of distribution, and area under the curve of a subsequent dose of PLD. The plasma exposure of Pegasys was also significantly reduced after initial delivery of 0.005 mg/ml PEG-HSPC liposome. However, a single 0.05 mg/kg IM dose of DNA-LNP did not significantly elevate PEG IgM and did not alter the IV pharmacokinetics of PLD. These data showed that PEGylated Covid-19 vaccines are less immunogenic compared to standard PEGylated HSPC liposomes and that there is an antibody threshold for accelerating the clearance of PEGylated therapeutics.

Role of anti-polyethylene glycol (PEG) antibodies in the allergic reactions to PEG-containing Covid-19 vaccines: Evidence for immunogenicity of PEG

A small fraction of recipients who receive polyethylene-glycol (PEG)-containing COVID-19 mRNA-LNP vaccines (Comirnaty and Spikevax) develop hypersensitivity reactions (HSRs) or anaphylaxis. A causal role of anti-PEG antibodies (Abs) has been proposed, but not yet been proven in humans.We used ELISA for serial measurements of SARS-CoV-2 neutralizing Ab (anti-S) and anti-PEG IgG/IgM Ab levels before and after the first and subsequent booster vaccinations with mRNA-LNP vaccines in a total of 291 blood donors. The HSRs in 15 subjects were graded and correlated with anti-PEG IgG/IgM, just as the anti-S and anti-PEG Ab levels with each other. The impacts of gender, allergy, mastocytosis and use of cosmetics were also analyzed. Serial testing of two or more plasma samples showed substantial individual variation of anti-S Ab levels after repeated vaccinations, just as the levels of anti-PEG IgG and IgM, which were over baseline in 98-99 % of unvaccinated individuals. About 3-4 % of subjects in the strongly left-skewed distribution had 15-45-fold higher values than the median, referred to as anti-PEG Ab supercarriers. Both vaccines caused significant rises of anti-PEG IgG/IgM with >10-fold rises in about ∼10 % of Comirnaty, and all Spikevax recipients. The anti-PEG IgG and/or IgM levels in the 15 vaccine reactors (3 anaphylaxis) were significantly higher compared to nonreactors. Serial testing of plasma showed significant correlation between the booster injection-induced rises of anti-S and anti-PEG IgGs, suggesting coupled anti-S and anti-PEG immunogenicity.Conclusions: The small percentage of people who have extremelevels of anti-PEG Ab in their blood may be at increased risk for HSRs/anaphylaxis to PEGylated vaccines and other PEGylated injectables. This risk might be further increased by the anti-PEG immunogenicity of these vaccines. Screening for anti-PEG Ab "supercarriers" may help predicting reactors and thus preventing these adverse phenomena.

Versatile delivery platform for nucleic acids, negatively charged protein drugs, and genome-editing ribonucleoproteins using a multi-step transformable polyrotaxane

Various biopharmaceuticals, such as nucleic acids, proteins, and genome-editing molecules, have been developed. Generally, carriers are prepared for each biopharmaceutical to deliver it intracellularly; thus, the applications of individual carriers are limited. Moreover, the development of carriers is laborious and expensive. Therefore, in the present study, versatile and universal delivery carriers were developed for various biopharmaceuticals using aminated polyrotaxane libraries. Step-by-step and logical screening revealed that aminated polyrotaxane, including the carbamate bond between the axile molecule and endcap, is suitable as a backbone polymer. Movable and flexible properties of the amino groups modified on polyrotaxane facilitated efficient complexation with various biopharmaceuticals, such as small interfering RNA, antisense oligonucleotides, messenger RNA, β-galactosidase, and genome-editing ribonucleoproteins. Diethylenetriamine and cystamine modifications of polyrotaxane provided endosomal-escape abilities and drug-release properties in the cytosol, allowing higher delivery efficacies than commercially available high-standard carriers without cytotoxicity. Thus, the resulting polyrotaxane might serve as a versatile and universal delivery platform for various biopharmaceuticals.

PEGylated Lipid Nanoparticle Formulations: Immunological Safety and Efficiency Perspective

Lipid nanoparticles (LNPs) have been recognized as efficient vehicles to transport a large variety of therapeutics. Currently in the spotlight as important constituents of the COVID-19 mRNA vaccines, LNPs play a significant role in protecting and transporting mRNA to cells. As one of their key constituents, polyethylene glycol (PEG)-lipid conjugates are important in defining LNP physicochemical characteristics and biological activity. PEGylation has proven particularly efficient in conferring longer systemic circulation of LNPs, thus greatly improving their pharmacokinetics and efficiency. Along with revealing the benefits of PEG conjugates, studies have revealed unexpected immune reactions against PEGylated nanocarriers such as accelerated blood clearance (ABC), involving the production of anti-PEG antibodies at initial injection, which initiates accelerated blood clearance upon subsequent injections, as well as a hypersensitivity reaction referred to as complement activation-related pseudoallergy (CARPA). Further, data have been accumulated indicating consistent yet sometimes controversial correlations between various structural parameters of the PEG-lipids, the properties of the PEGylated LNPs, and the magnitude of the observed adverse effects. Detailed knowledge and comprehension of such correlations are of foremost importance in the efforts to diminish and eliminate the undesirable immune reactions and improve the safety and efficiency of the PEGylated medicines. Here, we present an overview based on analysis of data from the CAS Content Collection regarding the PEGylated LNP immunogenicity and overall safety concerns. A comprehensive summary has been compiled outlining how various structural parameters of the PEG-lipids affect the immune responses and activities of the LNPs, with regards to their efficiency in drug delivery. This Review is thus intended to serve as a helpful resource in understanding the current knowledge in the field, in an effort to further solve the remaining challenges and to achieve full potential.

Consequences of poly(ethylene oxide) and poloxamer P188 on transcription in healthy and stressed myoblasts

Poly(ethylene oxide) (PEO) and poloxamers, a class of poly(ethylene oxide)-b-poly(propylene oxide)-b-poly(ethylene oxide) (PEO-PPO-PEO) triblock copolymers, have many personal and medical care applications, including the stabilization of stressed cellular membranes. Despite the widespread use, the cellular transcriptional response to these molecules is relatively unknown. C2C12 myoblasts, a model muscle cell, were subjected to short-term Poloxamer 188 (P188) and PEO181 (8,000 g/mol) treatment in culture. RNA was extracted and sequenced to quantify transcriptomic impact. The addition of moderate concentrations (14 µM) of either polymer to unstressed cells caused substantial differential gene expression, including at least twofold modulation of 357 and 588 genes, respectively. In addition, evaluation of the transcriptome response to osmotic stress without polymer treatment revealed dramatic change in RNA expression. Interestingly, the addition of polymer to stressed cells-at concentrations that provide physiological protection-did not yield a significant difference in expression of any gene relative to stress alone. Genome-scale expression analysis was corroborated by single-gene quantitative real-time PCR. Changes in protein expression were measured via western blot, which revealed partial alignment with the RNA results. Collectively, the significant changes to expression of multiple genes and resultant protein translation demonstrates an unexpectedly broad biochemical response to these polymers in healthy myoblasts in vitro. Meanwhile, the lack of substantial transcriptional response to polymer treatment in stressed cells highlights the physical nature of that protective mechanism.

One to one comparison of cell-free synthesized erythropoietin conjugates modified with linear polyglycerol and polyethylene glycol

With more than 20 Food and Drug Administration (FDA)-approved poly (ethylene glycol) (PEG) modified drugs on the market, PEG is the gold standard polymer in bioconjugation. The coupling improves stability, efficiency and can prolong blood circulation time of therapeutic proteins. Even though PEGylation is described as non-toxic and non-immunogenic, reports accumulate with data showing allergic reactions to PEG. Since PEG is not only applied in therapeutics, but can also be found in foods and cosmetics, anti-PEG-antibodies can occur even without a medical treatment. Hypersensitivity to PEG thereby can lead to a reduced drug efficiency, fast blood clearance and in rare cases anaphylactic reactions. Therefore, finding alternatives for PEG is crucial. In this study, we present linear polyglycerol (LPG) for bioconjugation as an alternative polymer to PEG. We report the conjugation of LPG and PEG by click-chemistry to the glycoprotein erythropoietin (EPO), synthesized in a eukaryotic cell-free protein synthesis system. Furthermore, the influence of the polymers on EPOs stability and activity on a growth hormone dependent cell-line was evaluated. The similar characteristics of both bioconjugates show that LPGylation can be a promising alternative to PEGylation.

Antibodies against Poly(ethylene glycol) Activate Innate Immune Cells and Induce Hypersensitivity Reactions to PEGylated Nanomedicines

Nanomedicines and macromolecular drugs can induce hypersensitivity reactions (HSRs) with symptoms ranging from flushing and breathing difficulties to hypothermia, hypotension, and death in the most severe cases. Because many normal individuals have pre-existing antibodies that bind to poly(ethylene glycol) (PEG), which is often present on the surface of nanomedicines and macromolecular drugs, we examined if and how anti-PEG antibodies induce HSRs to PEGylated liposomal doxorubicin (PLD). Anti-PEG IgG but not anti-PEG IgM induced symptoms of HSRs including hypothermia, altered lung function, and hypotension after PLD administration in C57BL/6 and nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mice. Hypothermia was significantly reduced by blocking FcγRII/III, by depleting basophils, monocytes, neutrophils, or mast cells, and by inhibiting secretion of histamine and platelet-activating factor. Anti-PEG IgG also induced hypothermia in mice after administration of other PEGylated liposomes, nanoparticles, or proteins. Humanized anti-PEG IgG promoted binding of PEGylated nanoparticles to human immune cells and induced secretion of histamine from human basophils in the presence of PLD. Anti-PEG IgE could also induce hypersensitivity reactions in mice after administration of PLD. Our results demonstrate an important role for IgG antibodies in induction of HSRs to PEGylated nanomedicines through interaction with Fcγ receptors on innate immune cells and provide a deeper understanding of HSRs to PEGylated nanoparticles and macromolecular drugs that may facilitate development of safer nanomedicines.

A PEG-lipid-free COVID-19 mRNA vaccine triggers robust immune responses in mice

COVID-19 mRNA vaccines represent a completely new category of vaccines and play a crucial role in controlling the COVID-19 pandemic. In this study, we have developed a PEG-lipid-free two-component mRNA vaccine (PFTCmvac) by formulating mRNA encoding the receptor binding domain (RBD) of SARS-CoV-2 into lipid-like nanoassemblies. Without using polyethylene glycol (PEG)-lipids, the self-assembled PFTCmvac forms thermostable nanoassemblies and exhibits a dose-dependent cellular uptake and membrane disruption, eventually leading to high-level protein expression in both mammalian cells and mice. Vaccination with PFTCmvac elicits strong humoral and cellular responses in mice, without evidence of significant adverse reactions. In addition, the vaccine platform does not trigger complement activation in human serum, even at a high serum concentration. Collectively, the PEG-lipid-free two-component nanoassemblies provide an alternative delivery technology for COVID-19 mRNA vaccines and opportunities for the rapid production of new mRNA vaccines against emerging infectious diseases.

The conundrum of COVID-19 mRNA vaccine-induced anaphylaxis

Novel messenger RNA (mRNA) vaccines have proven to be effective tools against coronavirus disease 2019, and they have changed the course of the pandemic. However, early reports of mRNA vaccine-induced anaphylaxis resulted in public alarm, contributing toward vaccine hesitancy. Although initial reports were concerning for an unusually high rate of anaphylaxis to the mRNA vaccines, the true incidence is likely comparable with other vaccines. These reactions occurred predominantly in young to middle-aged females, and many had a history of allergies. Although initially thought to be triggered by polyethylene glycol (PEG), lack of reproducibility of these reactions with subsequent dosing and absent PEG sensitization point away from an IgE-mediated PEG allergy in most. PEG skin testing has poor posttest probability and should be reserved for evaluating non-vaccine-related PEG allergy without influencing decisions for subsequent mRNA vaccination. Immunization stress-related response can closely mimic vaccine-induced anaphylaxis and warrants consideration as a potential etiology. Current evidence suggests that many individuals who developed anaphylaxis to the first dose of an mRNA vaccine can likely receive a subsequent dose after careful evaluation. The need to understand these reactions mechanistically remains critical because the mRNA platform is rapidly finding its way into other vaccinations and therapeutics.

Accelerated clearance by antibodies against methoxy PEG depends on pegylation architecture

Methoxy polyethylene glycol (mPEG) is attached to many proteins, peptides, nucleic acids and nanomedicines to improve their biocompatibility. Antibodies that bind PEG are present in many individuals and can be generated upon administration of pegylated therapeutics. Anti-PEG antibodies that bind to the PEG "backbone" can accelerate drug clearance and detrimentally affect drug activity and safety, but no studies have examined how anti-methoxy PEG (mPEG) antibodies, which selectively bind the terminus of mPEG, affect pegylated drugs. Here, we investigated how defined IgG and IgM monoclonal antibodies specific to the PEG backbone (anti-PEG) or terminal methoxy group (anti-mPEG) affect pegylated liposomes or proteins with a single PEG chain, a single branched PEG chain, or multiple PEG chains. Large immune complexes can be formed between all pegylated compounds and anti-PEG antibodies but only pegylated liposomes formed large immune complexes with anti-mPEG antibodies. Both anti-PEG IgG and IgM antibodies accelerated the clearance of all pegylated compounds but anti-mPEG antibodies did not accelerate clearance of proteins with a single or branched PEG molecule. Pegylated liposomes were primarily taken up by Kupffer cells in the liver, but both anti-PEG and anti-mPEG antibodies directed uptake of a heavily pegylated protein to liver sinusoidal endothelial cells. Our results demonstrate that in contrast to anti-PEG antibodies, immune complex formation and drug clearance induced by anti-mPEG antibodies depends on pegylation architecture; compounds with a single or branched PEG molecule are unaffected by anti-mPEG antibodies but are increasingly affected as the number of PEG chain in a structure increases.

Anti-PEG antibodies before and after a first dose of Comirnaty® (mRNA-LNP-based SARS-CoV-2 vaccine)

The early and massive vaccination campaign in Israel with the mRNA-LNP Comirnaty® (Pfizer-BioNTech) vaccine against the SARS-CoV-2 virus made available large amounts of data regarding the efficacy and safety of this vaccine. Adverse reactions to mRNA-based SARS-CoV-2 vaccines are rare events, but due to large mediatic coverage they became feared and acted as a potential source of delay for the vaccination of the Israeli population. The experience with the reactogenicity of the polyethylene glycol (PEG) moiety of PEGylated liposomes, PEGylated proteins and other PEGylated drugs raised the fear that similar adverse effects can be associated with the PEG lipid which is an essential component of currently used mRNA-LNP vaccines against COVID-19. In this study we quantified the levels of anti-PEG IgG, IgM and IgE present in the blood of 79 volunteers immediately before and 3 weeks after receiving a first dose of Comirnaty® vaccine. Our in vitro results show that different humanized anti-PEG antibodies bind the PEGylated nano-liposomes in a concentration-dependent manner, but they bind with a lower affinity to the Comirnaty vaccine, despite it having a high mole% of neutral PEG₂₀₀₀-lipid on its surface. We found an increase in IgG concentration in the blood 3 weeks after the first vaccine administration, but no increase in IgM or IgE. In addition, no severe signs of adverse reactions to the Comirnaty vaccine were observed in the population studied despite the significant pre-existing high titers of IgG before the first dose of vaccine in 2 donors.

Poly (beta-amino ester) as an in vivo nanocarrier for therapeutic nucleic acids

Therapeutic nucleic acids are an emerging class of therapy for treating various diseases through immunomodulation, protein replacement, gene editing, and genetic engineering. However, they need a vector to effectively and safely reach the target cells. Most gene and cell therapies rely on ex vivo gene delivery, which is laborious, time-consuming, and costly; therefore, devising a systematic vector for effective and safe in vivo delivery of therapeutic nucleic acids is required to target the cells of interest in an efficient manner. Synthetic nanoparticle vector poly beta amino ester (PBAE), a class of degradable polymer, is a promising candidate for in vivo gene delivery. PBAE is considered the most potent in vivo vector due to its excellent transfection performance and biodegradability. PBAE nanoparticles showed tunable charge density, diverse structural characteristics, excellent encapsulation capacity, high stability, stimuli-responsive release, site-specific delivery, potent binding to nucleic acids, flexible binding ability to various conjugates, and effective endosomal escape. These unique properties of PBAE are an essential contribution to in vivo gene delivery. The current review discusses each of the components used for PBAE synthesis and the impact of various environmental and physicochemical factors of the body on PBAE nanocarrier.

The mechanisms of anti-PEG immune response are different in the spleen and the lymph nodes

Polyethylene glycol (PEG) is a common ingredient in nanomedicines and pharmaceuticals. Recent studies show that approximately 20-70% of humans have anti-PEG antibodies that can recognize the polymer. Because these anti-PEG antibodies can reduce the effectiveness of certain PEGylated therapeutics, understanding how these immunoglobulins are produced is important. In this work, we investigate the mechanisms of the anti-PEG immune response, following the injection of polymeric nanoparticles by different routes of administration. We observed that the extent of systemic absorption and splenic deposition cannot predict the production of anti-PEG IgM - possibly because redundant biological pathways can be involved. Data obtained by surgically removing the spleen or depleting the complement activity suggest that the mechanisms behind the anti-PEG immune response differ between intravenous and subcutaneous injections. While B cells from the spleen appear to necessitate complement proteins to interact with nanoparticles, internalization by follicular B cells from the lymph nodes is unaffected by depletion of the cascade. This study confirms that the biological mechanisms involved in the immune recognition of nanomedicines varies based on the administration route. This knowledge can be utilized to use nanomedicines to engage the immune system in differentiated ways.

Zwitterionic Biomaterials

The term "zwitterionic polymers" refers to polymers that bear a pair of oppositely charged groups in their repeating units. When these oppositely charged groups are equally distributed at the molecular level, the molecules exhibit an overall neutral charge with a strong hydration effect via ionic solvation. The strong hydration effect constitutes the foundation of a series of exceptional properties of zwitterionic materials, including resistance to protein adsorption, lubrication at interfaces, promotion of protein stabilities, antifreezing in solutions, etc. As a result, zwitterionic materials have drawn great attention in biomedical and engineering applications in recent years. In this review, we give a comprehensive and panoramic overview of zwitterionic materials, covering the fundamentals of hydration and nonfouling behaviors, different types of zwitterionic surfaces and polymers, and their biomedical applications.