Polyethylene glycol and immunology: aspects of allergic reactions and their mechanisms, as well as ways to prevent them in clinical practice

In modern medical practice, where polyethylene glycol is widely used as a component of various drugs, such as vaccines, chemotherapy drugs, and antibiotics, including vaccines, the issue of allergic reactions to this substance is becoming increasingly important. The purpose of this study is to review and systematise data on various aspects of allergic reactions to polyethylene glycol with the aim of better understanding their pathogenesis, clinical manifestations, diagnostic methods, and possible treatment approaches. The study analysed literature data in modern databases, such as MEDLINE, PubMed, and Scopus, on allergic reactions to polyethylene glycol, using the keywords: "PEG", "polyethylene glycol", "allergy", "side effect". The main aspects of allergy to this substance were highlighted, including mechanisms of development, diagnostic methods, and possible treatment strategies. The analysis found that allergic reactions to polyethylene glycol can manifest in a variety of ways, including anaphylaxis and systemic reactions. A possible role for the immune response has been identified, including the production of IgE and IgM antibodies, complement activation, and accelerated clearance in response to polyethylene glycol, in blood plasma. Data are also provided on how to diagnose an increased risk of an allergic reaction in patients who have previously received drugs with this type of drug transporter and in patients receiving high molecular weight types of polyethylene glycol. The results of this review contribute to a better understanding of allergic reactions to polyethylene glycol and provide information for the development of more effective diagnostic and treatment methods.

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.

Effects of PEG antibodies on in vivo performance of LNP-mRNA vaccines

Polyethylene glycol (PEG) plays important roles in stabilizing and lengthening circulation time of lipid nanoparticle (LNP) vaccines. Nowadays various levels of PEG antibodies have been detected in human blood, but the impact and mechanism of PEG antibodies on the in vivo performance of LNP vaccines has not been clarified thoroughly. By illustrating the distribution characteristics of PEG antibodies in human, the present study focused on the influence of PEG antibodies on the safety and efficacy of LNP-mRNA vaccine against COVID-19 in animal models. It was found that PEG antibodies led to shortened blood circulation duration, elevated accumulation and mRNA expression in liver and spleen, enhanced expression in macrophage and dendritic cells, while without affecting the production of anti-Spike protein antibodies of COVID-19 LNP vaccine. Noteworthily, PEG antibodies binding on the LNP vaccine increased probability of complement activation in animal as well as in human serum and led to lethal side effect in large dosage via intravenous injection of mice. Our data suggested that PEG antibodies in human was a risky factor of LNP-based vaccines for biosafety concerns but not efficacy.

The interplay between PEGylated nanoparticles and blood immune system

During the last two decades, an increasing number of reports have pointed out that the immunogenicity of polyethylene glycol (PEG) may trigger accelerated blood clearance (ABC) and hypersensitivity reaction (HSR) to PEGylated nanoparticles, which could make PEG modification counterproductive. These phenomena would be detrimental to the efficacy of the load and even life-threatening to patients. Consequently, further elucidation of the interplay between PEGylated nanoparticles and the blood immune system will be beneficial to developing and applying related formulations. Many groups have worked to unveil the relevance of structural factors, dosing schedule, and other factors to the ABC phenomenon and hypersensitivity reaction. Interestingly, the results of some reports seem to be difficult to interpret or contradict with other reports. In this review, we summarize the physiological mechanisms of PEG-specific immune response. Moreover, we speculate on the potential relationship between the induction phase and the effectuation phase to explain the divergent results in published reports. In addition, the role of nanoparticle-associated factors is discussed based on the classification of the action phase. This review may help researchers to develop PEGylated nanoparticles to avoid unfavorable immune responses based on the underlying mechanism.

Clinical Impact of Antipolyethylene Glycol (PEG) Antibody in Hematological Patients Administered PEGylated-Granulocyte Colony-Stimulating Factor

Polyethylene glycol (PEG) is a polymer covalently attached to proteins to improve their half-life and efficacy. We previously reported that the PEGylated granulocyte colony-stimulating factor (PEG-G-CSF) is immunogenic, which could adversely impact drug efficacy and safety in animal models. Here, we analyzed the relationship between anti-PEG antibody titers and the clinical impact of PEG-G-CSF in 19 hematological patients. A gradual decrease of anti-PEG antibody titers from baseline was observed after PEG-G-CSF administration. Of the 19 participants, 10 were assessed for noninfectious fever after the first administration of PEG-G-CSF and three experienced this reaction. The receiver operating characteristic curve revealed that the cut-off values of pretreated anti-PEG IgM and IgG titers for noninfectious fever were set at 5.0 and 96.6 U/mL, respectively. All patients who experienced noninfectious fever had anti-PEG antibody titers above this cut-off value (P = .033). An enzyme-linked immunosorbent assay revealed that some anti-PEG antibodies in patients with anti-PEG antibody titers above the cut-off value reacted with the PEGylated liposome. These results indicate the reactivity of the anti-PEG antibodies to PEGylated therapeutics observed in hematologic patients and the possibility of the relationship between high titers of anti-PEG antibodies and the development of adverse events after PEG-G-CSF administration.

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.

A mouse model for studying the effect of blood anti-PEG IgMs levels on the in vivo fate of PEGylated liposomes

The presence of anti-polyethylene glycol (PEG) antibodies in the systemic circulation might have potential implications for the therapeutic activity of PEGylated products in vivo in the clinic. In order to study the effect of pre-existing anti-PEG antibodies on the in vivo fate and the therapeutic efficiency of PEGylated therapeutics, we developed a BALB/c mouse model by virtue of the intraperitoneal (i.p.) inoculation of hybridoma cells (HIK-M09 and HIK-M11), secreting monoclonal anti-PEG IgM, mimicking the presence of pre-existing anti-PEG antibodies in the blood. In the model, the titers of anti-PEG IgM in the blood increased as a function of hybridoma cells numbers and time after i.p. inoculation. The in vivo levels of anti-PEG IgM decreased in a dose-dependent manner, following i.v. administration of empty PEGylated liposomes. C26 tumor-bearing mice with measurable levels of anti-PEG IgM, receiving i.v. injection of DiR-labeled empty PEGylated liposomes, showed lower levels of liposomal tumor accumulation and higher levels of liver and spleen accumulation, compared to C26 tumor-bearing mice without measurable anti-PEG IgM. This specifies that the presence of anti-PEG IgM in the murine circulation induced accelerated blood clearance of PEGylated liposomes and reduced their tumor accumulation. The biodistribution and antitumor efficacy of commercially available doxorubicin (DXR)-containing PEGylated liposomes, Doxil®, were scrutinized in the anti-PEG IgM mouse model. In C26 tumor-bearing mice having circulating anti-PEG IgM, at 24 h after injection almost no DXR was observed in blood and tumor, and increased DXR accumulation was observed in spleen and liver, compared to tumor-bearing mice with no circulating anti-PEG IgM. The antitumor efficacy of Doxil® was significantly compromised in the C26 tumor-bearing mice in the presence of anti-PEG IgM. These results demonstrate that the anti-PEG IgM mouse model could be a useful prognostic indicator for the therapeutic effectiveness of different formulations of PEGylated therapeutics in pre-clinical studies.

Anti-PEG IgM production and accelerated blood clearance phenomenon after the administration of PEGylated exosomes in mice

Recently, there is an increasing interest in exosomes or extracellular vesicles as potential candidates for delivering RNAs, proteins, genes, and anticancer agents. Engineering of exosome properties is rapidly evolving as a means of expanding exosome applications. PEGylation of exosomes is a technique used to improve their in vivo stability, circulation half-lives, and sometimes to allow the binding targeting ligands to the exosome exterior. According to FDA guidelines for the development of PEGylated proteins, immunological responses to PEGylated molecules and particles should be examined. In this study, we prepared PEGylated exosomes and investigated the production of anti-PEG IgM antibodies after single i.v. injections in mice. In addition, we monitored blood concentrations and tumor accumulation of a second dose of PEGylated exosomes administered after the initial dose. Single injections of PEGylated exosomes in mice induced anti-PEG IgM production in a T cell-dependent manner. The anti-PEG IgM production decreased when the injection dose of PEGylated exosomes was further increased. Anti-PEG IgM induced by injection of PEGylated exosomes decreased blood concentrations of a second dose of PEGylated exosomes and suppressed their tumor accumulation in a C26 murine colorectal cancer model. Initial injection doses of either PEGylated liposomes or PEGylated ovalbumin (PEG-OVA), both of them induced anti-PEG IgM production, also decreased the blood concentration of PEGylated exosomes. Interestingly, anti-PEG IgM induced by injection of PEGylated exosomes did not affect the blood concentration of PEG-OVA. These results imply the importance of monitoring anti-PEG IgM when repeat PEGylated exosome doses are required and/or when PEGylated exosomes are used together with other PEGylated therapeutics.

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

Abstract

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

Lay Summary

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