Anti-PEG antibodies compromise the integrity of PEGylated lipid-based nanoparticles via complement

Enhancing bevacizumab efficacy in a colorectal tumor mice model using dextran-coated albumin nanoparticles

Bevacizumab is a monoclonal antibody (mAb) that prevents the growth of new blood vessels and is currently employed in the treatment of colorectal cancer (CRC). However, like other mAb, bevacizumab shows a limited penetration in the tumors, hampering their effectiveness and inducing adverse reactions. The aim of this work was to design and evaluate albumin-based nanoparticles, coated with dextran, as carriers for bevacizumab in order to promote its accumulation in the tumor and, thus, improve its antiangiogenic activity. These nanoparticles (B-NP-DEX50) displayed a mean size of about 250 nm and a payload of about 110 µg/mg. In a CRC mice model, these nanoparticles significantly reduced tumor growth and increased tumor doubling time, tumor necrosis and apoptosis more effectively than free bevacizumab. At the end of study, bevacizumab plasma levels were higher in the free drug group, while tumor levels were higher in the B-NP-DEX50 group (2.5-time higher). In line with this, the biodistribution study revealed that nanoparticles accumulated in the tumor core, potentially improving therapeutic efficacy while reducing systemic exposure. In summary, B-NP-DEX can be an adequate alternative to improve the therapeutic efficiency of biologically active molecules, offering a more specific biodistribution to the site of action.

Nanoparticle-Binding Immunoglobulins Predict Variable Complement Responses in Healthy and Diseased Cohorts

Systemic administration of nanomedicines results in the activation of the complement cascade, promoting phagocytic uptake and triggering proinflammatory responses. Identifying the biomarkers that can predict the "risk" of abnormally high complement responders can improve the safety and efficacy of nanomedicines. Polyethylene glycol (PEG) and dextran are two types of clinically approved polymer coatings that trigger complement activation. We performed a multifaceted analysis of the factors affecting the complement activation by PEGylated liposomal doxorubicin (PLD) and dextran-coated superparamagnetic iron oxide nanoworms (SPIO NWs) in plasma from patients with different inflammatory disease conditions and healthy donors. The complement activation (measured as deposition of the complement protein C3) varied greatly, with 29-fold and 26-fold differences for PLD and SPIO NWs, respectively. Chronic inflammation, acute infection, use of steroids, and sex had minor effects on the variable complement activation, whereas age inversely correlated with the complement activation. C-reactive protein level was not predictive of high (top 20th percentile) complement responses. Plasma concentrations of the main complement factors, as well as total IgG and IgM, showed no correlation with the activation by either nanoparticle. On the other hand, plasma concentrations of anti-PEG IgG and IgM showed a strong positive correlation with the activation by PLD. Particularly, titers of anti-PEG IgM showed the best predictive value for the "risk" of high complement activation by PLD. Titers of antidextran IgG and IgM showed a lower correlation with the activation by SPIO NWs and poor predictive value of the top 20% complement responses. Nanoparticle-bound immunoglobulins showed the best correlation with complement activation and a strong predictive value, supporting the critical role of immunoglobulins in inciting complement. The opsonization of PLD with C3 in plasma with high anti-PEG antibodies was predominantly via the alternative pathway. Characterizing the nature of nanoparticle-binding antibodies has important implications in mitigating and stratifying nanomedicine safety.

PEGylation-Dependent Cell Uptake of Lipid Nanoparticles Revealed by Spatiotemporal Correlation Spectroscopy

Polyethylene glycol (PEG) is a common surface modification for lipid nanoparticles (LNPs) to improve their stability and in vivo circulation time. However, the impact of PEGylation on LNP cellular uptake remains poorly understood. To tackle this issue, we systematically compared plain and PEGylated LNPs by combining dynamic light scattering, electrophoretic light scattering, and synchrotron small-angle X-ray scattering (SAXS) that unveils a striking similarity in size and core structure but a significant reduction in surface charge. Upon administration to human embryonic kidney (HEK 293) cells, plain and PEGylated LNPs were internalized through different endocytic routes, as revealed by spatiotemporal correlation spectroscopy. An imaging-derived mean square displacement (iMSD) analysis shows that PEGylated LNPs exhibit a significantly stronger preference for caveolae-mediated endocytosis (CAV) and clathrin-mediated endocytosis (CME) pathways compared to plain LNPs, with these latter being better tailored to MCR-dependent internalization and trafficking. This suggests that PEG plays a crucial role in directing LNPs toward specific cellular uptake routes. Further studies should explore how PEG-mediated endocytosis impacts intracellular trafficking and ultimately translates to therapeutic efficacy, guiding the design of next-generation LNP delivery systems.

Amine headgroups in ionizable lipids drive immune responses to lipid nanoparticles by binding to the receptors TLR4 and CD1d

Lipid nanoparticles (LNPs) are the most clinically advanced delivery vehicle for RNA therapeutics, partly because of established lipid structure-activity relationships focused on formulation potency. Yet such knowledge has not extended to LNP immunogenicity. Here we show that the innate and adaptive immune responses elicited by LNPs are linked to their ionizable lipid chemistry. Specifically, we show that the amine headgroups in ionizable lipids drive LNP immunogenicity by binding to Toll-like receptor 4 and CD1d and by promoting lipid-raft formation. Immunogenic LNPs favour a type-1 T-helper-cell-biased immune response marked by increases in the immunoglobulins IgG2c and IgG1 and in the pro-inflammatory cytokines tumour necrosis factor, interferon γ and the interleukins IL-6 and IL-2. Notably, the inflammatory signals originating from these receptors inhibit the production of anti-poly(ethylene glycol) IgM antibodies, preventing the often-observed loss of efficacy in the LNP-mediated delivery of siRNA and mRNA. Moreover, we identified computational methods for the prediction of the structure-dependent innate and adaptive responses of LNPs. Our findings may help accelerate the discovery of well-tolerated ionizable lipids suitable for repeated dosing.

Strategies to Overcome Hurdles in Cancer Immunotherapy

Despite marked advancements in cancer immunotherapy over the past few decades, there remains an urgent need to develop more effective treatments in humans. This review explores strategies to overcome hurdles in cancer immunotherapy, leveraging innovative technologies including multi-specific antibodies, chimeric antigen receptor (CAR) T cells, myeloid cells, cancer-associated fibroblasts, artificial intelligence (AI)-predicted neoantigens, autologous vaccines, and mRNA vaccines. These approaches aim to address the diverse facets and interactions of tumors' immune evasion mechanisms. Specifically, multi-specific antibodies and CAR T cells enhance interactions with tumor cells, bolstering immune responses to facilitate tumor infiltration and destruction. Modulation of myeloid cells and cancer-associated fibroblasts targets the tumor's immunosuppressive microenvironment, enhancing immunotherapy efficacy. AI-predicted neoantigens swiftly and accurately identify antigen targets, which can facilitate the development of personalized anticancer vaccines. Additionally, autologous and mRNA vaccines activate individuals' immune systems, fostering sustained immune responses against cancer neoantigens as therapeutic vaccines. Collectively, these strategies are expected to enhance efficacy of cancer immunotherapy, opening new horizons in anticancer treatment.

Ethylene oxide graft copolymers reduce the immunogenicity of lipid nanoparticles

Lipid nanoparticle (LNP)/mRNA complexes have great therapeutic potential but their PEG chains can induce the production of anti-PEG antibodies. New LNPs that do not contain PEG are greatly needed. We demonstrate here that poly-glutamic acid-ethylene oxide graft copolymers can replace the PEG on LNPs and outperform PEG-LNPs after chronic administration.

Toward a large-batch manufacturing process for silicon-stabilized lipid nanoparticles: A highly customizable RNA delivery platform

While lipid nanoparticles (LNPs) are a key enabling technology for RNA-based therapeutics, some outstanding challenges hinder their wider clinical translation and use, particularly in terms of RNA stability and limited shelf life. In response to these limitations, we developed silicon-stabilized hybrid lipid nanoparticles (sshLNPs) as a next-generation nanocarrier with improved physical and temperature stability, as well as the highly advantageous capacity for "post-hoc loading" of RNA. Nevertheless, previously reported sshLNP formulations were produced using lipid thin film hydration, making scale-up impractical. To realize the potential of this emerging delivery platform, a manufacturing process enabling multikilogram batch sizes was required for successful clinical translation and deployment at scale. This was achieved by developing a revised protocol based on solvent injection mixing and incorporating other process adjustments to enable in-flow extrusion of multiliter volumes, while ensuring sshLNPs with the desired characteristics. Optimized procedures for nanoparticle formation, extrusion, and tangential flow filtration (to remove residual organic solvent) currently enable production of 2 kg finished batches. Importantly, sshLNPs produced via the modified large-scale workflow show equivalent physical and functional properties to those derived from the earlier small-scale methods, paving the way for GMP manufacturing protocols to enable vital translational clinical studies.

Role of size, surface charge, and PEGylated lipids of lipid nanoparticles (LNPs) on intramuscular delivery of mRNA

Lipid nanoparticles (LNPs) are currently the most commonly used non-viral gene delivery system. Their physiochemical attributes, encompassing size, charge and surface modifications, significantly affect their behaviors both in vivo and in vitro. Nevertheless, the effects of these properties on the transfection and distribution of LNPs after intramuscular injection remain elusive. In this study, LNPs with varying sizes, lipid-based charges and PEGylated lipids were formulated to study their transfection and in vivo distribution. Luciferase mRNA (mLuc) was entraped in LNPs as a model nucleic acid molecule. Results indicated that smaller-sized LNPs and those with neutral potential presented superior transfection efficiency after intramuscular injection. Surprisingly, the sizes and charges did not exert a notable influence on the in vivo distribution of the LNPs. Furthermore, PEGylated lipids with shorter acyl chains contributed to enhanced transfection efficiency due to their superior cellular uptake and lysosomal escape capabilities. Notably, the mechanisms underlying cellular uptake differed among LNPs containing various types of PEGylated lipids, which was primarily attributed to the length of their acyl chain. Together, these insights underscore the pivotal role of nanoparticle characteristics and PEGylated lipids in the intramuscular route. This study not only fills crucial knowledge gaps but also provides significant directions for the effective delivery of mRNA via LNPs.

Lipid Nanoparticles Elicit Reactogenicity and Sickness Behavior in Mice Via Toll-Like Receptor 4 and Myeloid Differentiation Protein 88 Axis

mRNA therapeutics encapsulated in lipid nanoparticles (LNPs) offer promising avenues for treating various diseases. While mRNA vaccines anticipate immunogenicity, the associated reactogenicity of mRNA-loaded LNPs poses significant challenges, especially in protein replacement therapies requiring multiple administrations, leading to adverse effects and suboptimal therapeutic outcomes. Historically, research has primarily focused on the reactogenicity of mRNA cargo, leaving the role of LNPs understudied in this context. Adjuvanticity and pro-inflammatory characteristics of LNPs, originating at least in part from ionizable lipids, may induce inflammation, activate toll-like receptors (TLRs), and impact mRNA translation. Knowledge gaps remain in understanding LNP-induced TLR activation and its impact on induction of animal sickness behavior. We hypothesized that ionizable lipids in LNPs, structurally resembling lipid A from lipopolysaccharide, could activate TLR4 signaling via MyD88 and TRIF adaptors, thereby propagating LNP-associated reactogenicity. Our comprehensive investigation utilizing gene ablation studies and pharmacological receptor manipulation proves that TLR4 activation by LNPs triggers distinct physiologically meaningful responses in mice. We show that TLR4 and MyD88 are essential for reactogenic signal initiation, pro-inflammatory gene expression, and physiological outcomes like food intake and body weight─robust metrics of sickness behavior in mice. The application of the TLR4 inhibitor TAK-242 effectively reduces the reactogenicity associated with LNPs by mitigating TLR4-driven inflammatory responses. Our findings elucidate the critical role of the TLR4-MyD88 axis in LNP-induced reactogenicity, providing a mechanistic framework for developing safer mRNA therapeutics and offering a strategy to mitigate adverse effects through targeted inhibition of this pathway.

Lipid Nanoparticles for Nucleic Acid Delivery Beyond the Liver

Lipid nanoparticles (LNPs) are the most clinically advanced drug delivery system for nucleic acid therapeutics, exemplified by the success of the COVID-19 mRNA vaccines. However, their clinical use is currently limited to hepatic diseases and vaccines due to their tendency to accumulate in the liver upon intravenous administration. To fully leverage their potential, it is essential to understand and address their liver tropism, while also developing strategies to enhance delivery to tissues beyond the liver. Ensuring that these therapeutics reach their target cells while avoiding off-target cells is essential for both their efficacy and safety. There are three potential targeting strategies-passive, active, and endogenous-which can be used individually or in combination to target nonhepatic tissues. In this review, we delve into the recent advancements in LNP engineering for delivering nucleic acid beyond the liver.

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.

Comirnaty-induced cardiopulmonary distress and other symptoms of complement-mediated pseudo-anaphylaxis in a hyperimmune pig model: Causal role of anti-PEG antibodies

Background

Comirnaty, Pfizer-BioNTech's polyethylene-glycol (PEG)-containing Covid-19 vaccine, can cause hypersensitivity reactions (HSRs), or rarely, life-threatening anaphylaxis in a small fraction of immunized people. A causal role of anti-PEG antibodies (Abs) has been proposed, but causality has not yet proven in an animal model. The aim of this study was to provide such evidence using pigs immunized against PEG, which displayed very high levels of anti-PEG antibodies (Abs). We also aimed to find evidence for a role of complement activation and thromboxane A2 release in blood to explore the mechanism of anaphylaxis.

Methods

Pigs (n = 6) were immunized with 0.1 mg/kg PEGylated liposome (Doxebo) i.v., and the rise of anti-PEG IgG and IgM were measured in serial blood samples with ELISA. After ∼2-3 weeks the animals were injected i.v. with 1/3 human dose of the PEGylated mRNA vaccine, Comirnaty, and the hemodynamic (PAP, SAP) cardiopulmonary (HR, EtCO2,), hematological (WBC, granulocyte, lymphocyte and platelet counts) parameters and blood immune mediators (anti-PEG IgM and IgG antibodies, thromboxane B2, C3a) were measured as endpoints of HSRs (anaphylaxis).

Results

The level of anti-PEG IgM and IgG rose 5-10-thousand-fold in all of 6 pigs immunized with Doxebo by day 6, after which time all animals developed anaphylactic shock to i.v. injection of 1/3 human dose of Comirnaty. The reaction, starting within 1 min involved maximal pulmonary hypertension and decreased systemic pulse pressure amplitude, tachycardia, granulo- and thrombocytopenia, and skin reactions (flushing or rash). These physiological changes or their absence were paralleled by C3a and TXB2 rises in blood.

Conclusions

Consistent with previous studies, these data show a causal role of anti-PEG Abs in the anaphylaxis to Comirnaty, which involves complement activation, and, hence, it represents C activation-related pseudo-anaphylaxis. The setup provides the first large-animal model for mRNA-vaccine-induced anaphylaxis in humans.

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.

Artificial protein coronas: directing nanoparticles to targets

The protein corona surrounding nanoparticles (NPs) offers exciting possibilities for targeted drug delivery. However, realizing this potential requires direct evidence of corona-receptor interactions in vivo; a challenge hampered by the limitations of in vitro settings. This opinion proposes that utilizing engineered protein coronas can address this challenge. Artificial coronas made of selected plasma proteins retain their properties in vivo, enabling manipulation for specific receptor targeting. To directly assess corona-receptor interactions mimicking in vivo complexity, we propose testing artificial coronas with recently adapted quartz crystal microbalance (QCM) setups whose current limitations and potential advancements are critically discussed. Finally, the opinion proposes future experiments to decipher corona-receptor interactions and unlock the full potential of the protein corona for NP-based drug delivery.

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.

Development of Lipid Nanoparticle Formulation for the Repeated Administration of mRNA Therapeutics

During the COVID-19 pandemic, mRNA vaccines emerged as a rapid and effective solution for global immunization. The success of COVID-19 mRNA vaccines has increased interest in the use of lipid nanoparticles (LNPs) for the in vivo delivery of mRNA therapeutics. Although mRNA exhibits robust expression profiles, transient protein expression is often observed, raising uncertainty regarding the frequency of its administration. Additionally, various RNA therapeutics may necessitate repeated dosing to achieve optimal therapeutic outcomes. Nevertheless, the impact of repeated administrations of mRNA/LNP on immune responses and protein expression efficacy remains unclear. In this study, we investigated the influence of the formulation parameters, specifically ionizable lipids and polyethylene glycol (PEG) lipids, on the repeat administration of mRNA/LNP. Our findings revealed that ionizable lipids had no discernible impact on the dose-responsive efficacy of repeat administrations, whereas the lipid structure and molar ratio of PEG lipids were primary factors that affected mRNA/LNP performance. The optimization of the LNP formulation with PEG lipid confirmed the sustained dose-responsive efficacy of mRNA after repeated administrations. This study highlights the critical importance of optimizing LNP formulations for mRNA therapeutics requiring repeated administrations.

Advances in lipid nanoparticle mRNA therapeutics beyond COVID-19 vaccines

The remarkable success of two lipid nanoparticle-mRNA vaccines against coronavirus disease (COVID-19) has placed the therapeutic and prophylactic potential of messenger RNA (mRNA) in the spotlight. It has also drawn attention to the indispensable role of lipid nanoparticles in enabling the effects of this nucleic acid. To date, lipid nanoparticles are the most clinically advanced non-viral platforms for mRNA delivery. This is thanks to their favorable safety profile and efficiency in protecting the nucleic acid from degradation and allowing its cellular uptake and cytoplasmic release upon endosomal escape. Moreover, the development of lipid nanoparticle-mRNA therapeutics was already a very active area of research even before the COVID-19 pandemic, which has likely only begun to bear its fruits. In this Review, we first discuss key aspects of the development of lipid nanoparticles as mRNA carriers. We then highlight promising preclinical and clinical studies involving lipid nanoparticle-mRNA formulations against infectious diseases and cancer, and to enable protein replacement or supplementation and genome editing. Finally, we elaborate on the challenges in advancing lipid nanoparticle-mRNA technology to widespread therapeutic use.

Unlocking the Mitochondria for Nanomedicine-based Treatments: Overcoming Biological Barriers, Improving Designs, and Selecting Verification Techniques

Enhanced targeting approaches will support the treatment of diseases associated with dysfunctional mitochondria, which play critical roles in energy generation and cell survival. Obstacles to mitochondria-specific targeting include the presence of distinct biological barriers and the need to pass through (or avoid) various cell internalization mechanisms. A range of studies have reported the design of mitochondrially-targeted nanomedicines that navigate the complex routes required to influence mitochondrial function; nonetheless, a significant journey lies ahead before mitochondrially-targeted nanomedicines become suitable for clinical use. Moving swiftly forward will require safety studies, in vivo assays confirming effectiveness, and methodologies to validate mitochondria-targeted nanomedicines' subcellular location/activity. From a nanomedicine standpoint, we describe the biological routes involved (from administration to arrival within the mitochondria), the features influencing rational design, and the techniques used to identify/validate successful targeting. Overall, rationally-designed mitochondria-targeted-based nanomedicines hold great promise for precise subcellular therapeutic delivery.

Strategies to reduce the risks of mRNA drug and vaccine toxicity

mRNA formulated with lipid nanoparticles is a transformative technology that has enabled the rapid development and administration of billions of coronavirus disease 2019 (COVID-19) vaccine doses worldwide. However, avoiding unacceptable toxicity with mRNA drugs and vaccines presents challenges. Lipid nanoparticle structural components, production methods, route of administration and proteins produced from complexed mRNAs all present toxicity concerns. Here, we discuss these concerns, specifically how cell tropism and tissue distribution of mRNA and lipid nanoparticles can lead to toxicity, and their possible reactogenicity. We focus on adverse events from mRNA applications for protein replacement and gene editing therapies as well as vaccines, tracing common biochemical and cellular pathways. The potential and limitations of existing models and tools used to screen for on-target efficacy and de-risk off-target toxicity, including in vivo and next-generation in vitro models, are also discussed.

RNA-encapsulating lipid nanoparticles in cancer immunotherapy: From pre-clinical studies to clinical trials

Nanoparticle-based delivery systems such as RNA-encapsulating lipid nanoparticles (RNA LNPs) have dramatically advanced in function and capacity over the last few decades. RNA LNPs boast of a diverse array of external and core configurations that enhance targeted delivery and prolong circulatory retention, advancing therapeutic outcomes. Particularly within the realm of cancer immunotherapies, RNA LNPs are increasingly gaining prominence. Pre-clinical in vitro and in vivo studies have laid a robust foundation for new and ongoing clinical trials that are actively enrolling patients for RNA LNP cancer immunotherapy. This review explores RNA LNPs, starting from their core composition to their external membrane formulation, set against a backdrop of recent clinical breakthroughs. We further elucidate the LNP delivery avenues, broach the prevailing challenges, and contemplate the future perspectives of RNA LNP-mediated immunotherapy.

Revolutionizing lymph node metastasis imaging: the role of drug delivery systems and future perspectives

The deployment of imaging examinations has evolved into a robust approach for the diagnosis of lymph node metastasis (LNM). The advancement of technology, coupled with the introduction of innovative imaging drugs, has led to the incorporation of an increasingly diverse array of imaging techniques into clinical practice. Nonetheless, conventional methods of administering imaging agents persist in presenting certain drawbacks and side effects. The employment of controlled drug delivery systems (DDSs) as a conduit for transporting imaging agents offers a promising solution to ameliorate these limitations intrinsic to metastatic lymph node (LN) imaging, thereby augmenting diagnostic precision. Within the scope of this review, we elucidate the historical context of LN imaging and encapsulate the frequently employed DDSs in conjunction with a variety of imaging techniques, specifically for metastatic LN imaging. Moreover, we engage in a discourse on the conceptualization and practical application of fusing diagnosis and treatment by employing DDSs. Finally, we venture into prospective applications of DDSs in the realm of LNM imaging and share our perspective on the potential trajectory of DDS development.

mRNA-LNP COVID-19 Vaccine Lipids Induce Complement Activation and Production of Proinflammatory Cytokines: Mechanisms, Effects of Complement Inhibitors, and Relevance to Adverse Reactions

A small fraction of people vaccinated with mRNA-lipid nanoparticle (mRNA-LNP)-based COVID-19 vaccines display acute or subacute inflammatory symptoms whose mechanism has not been clarified to date. To better understand the molecular mechanism of these adverse events (AEs), here, we analyzed in vitro the vaccine-induced induction and interrelations of the following two major inflammatory processes: complement (C) activation and release of proinflammatory cytokines. Incubation of Pfizer-BioNTech's Comirnaty and Moderna's Spikevax with 75% human serum led to significant increases in C5a, sC5b-9, and Bb but not C4d, indicating C activation mainly via the alternative pathway. Control PEGylated liposomes (Doxebo) also induced C activation, but, on a weight basis, it was ~5 times less effective than that of Comirnaty. Viral or synthetic naked mRNAs had no C-activating effects. In peripheral blood mononuclear cell (PBMC) cultures supplemented with 20% autologous serum, besides C activation, Comirnaty induced the secretion of proinflammatory cytokines in the following order: IL-1α < IFN-γ < IL-1β < TNF-α < IL-6 < IL-8. Heat-inactivation of C in serum prevented a rise in IL-1α, IL-1β, and TNF-α, suggesting C-dependence of these cytokines' induction, although the C5 blocker Soliris and C1 inhibitor Berinert, which effectively inhibited C activation in both systems, did not suppress the release of any cytokines. These findings suggest that the inflammatory AEs of mRNA-LNP vaccines are due, at least in part, to stimulation of both arms of the innate immune system, whereupon C activation may be causally involved in the induction of some, but not all, inflammatory cytokines. Thus, the pharmacological attenuation of inflammatory AEs may not be achieved via monotherapy with the tested C inhibitors; efficacy may require combination therapy with different C inhibitors and/or other anti-inflammatory agents.

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.

In Vivo mRNA CAR T Cell Engineering via Targeted Ionizable Lipid Nanoparticles with Extrahepatic Tropism

With six therapies approved by the Food and Drug Association, chimeric antigen receptor (CAR) T cells have reshaped cancer immunotherapy. However, these therapies rely on ex vivo viral transduction to induce permanent CAR expression in T cells, which contributes to high production costs and long-term side effects. Thus, this work aims to develop an in vivo CAR T cell engineering platform to streamline production while using mRNA to induce transient, tunable CAR expression. Specifically, an ionizable lipid nanoparticle (LNP) is utilized as these platforms have demonstrated clinical success in nucleic acid delivery. Though LNPs often accumulate in the liver, the LNP platform used here achieves extrahepatic transfection with enhanced delivery to the spleen, and it is further modified via antibody conjugation (Ab-LNPs) to target pan-T cell markers. The in vivo evaluation of these Ab-LNPs confirms that targeting is necessary for potent T cell transfection. When using these Ab-LNPs for the delivery of CAR mRNA, antibody and dose-dependent CAR expression and cytokine release are observed along with B cell depletion of up to 90%. In all, this work conjugates antibodies to LNPs with extrahepatic tropism, evaluates pan-T cell markers, and develops Ab-LNPs capable of generating functional CAR T cells in vivo.

Chemically Modified Platforms for Better RNA Therapeutics

RNA-based therapies have catalyzed a revolutionary transformation in the biomedical landscape, offering unprecedented potential in disease prevention and treatment. However, despite their remarkable achievements, these therapies encounter substantial challenges including low stability, susceptibility to degradation by nucleases, and a prominent negative charge, thereby hindering further development. Chemically modified platforms have emerged as a strategic innovation, focusing on precise alterations either on the RNA moieties or their associated delivery vectors. This comprehensive review delves into these platforms, underscoring their significance in augmenting the performance and translational prospects of RNA-based therapeutics. It encompasses an in-depth analysis of various chemically modified delivery platforms that have been instrumental in propelling RNA therapeutics toward clinical utility. Moreover, the review scrutinizes the rationale behind diverse chemical modification techniques aiming at optimizing the therapeutic efficacy of RNA molecules, thereby facilitating robust disease management. Recent empirical studies corroborating the efficacy enhancement of RNA therapeutics through chemical modifications are highlighted. Conclusively, we offer profound insights into the transformative impact of chemical modifications on RNA drugs and delineates prospective trajectories for their future development and clinical integration.

Self-Assembled Nanostructures Presenting Repetitive Arrays of Subunit Antigens for Enhanced Immune Response

Infectious diseases pose persistent threats to public health, demanding advanced vaccine technologies. Nanomaterial-based delivery systems offer promising solutions to enhance immunogenicity while minimizing reactogenicity. We introduce a self-assembled vaccine (SAV) platform employing antigen-polymer conjugates designed to facilitate robust immune responses. The SAVs exhibit efficient cellular uptake by dendritic cells (DCs) and macrophages, which are crucial players in the innate immune system. The high-density antigen presentation of this SAV platform enhances the affinity for DCs through multivalent recognition, significantly augmenting humoral immunity. SAV induced high levels of immunoglobulin G (IgG), IgG1, and IgG2a, suggesting that mature DCs efficiently induced B cell activation through multivalent antigen recognition. Universality was confirmed by applying it to respiratory viruses, showcasing its potential as a versatile vaccine platform. Furthermore, we have also demonstrated strong protection against influenza A virus infection with SAV containing hemagglutinin, which is used in influenza A virus subunit vaccines. The efficacy and adaptability of this nanostructured vaccine present potential utility in combating infectious diseases.

Amphiphilic Block Copolymer Nanostructures as a Tunable Delivery Platform: Perspective and Framework for the Future Drug Product Development

Nanoformulation of active payloads or pharmaceutical ingredients (APIs) has always been an area of interest to achieve targeted, sustained, and efficacious delivery. Various delivery platforms have been explored, but loading and delivery of APIs have been challenging because of the chemical and structural properties of these molecules. Polymersomes made from amphiphilic block copolymers (ABCPs) have shown enormous promise as a tunable API delivery platform and confer multifold advantages over lipid-based systems. For example, a COVID booster vaccine comprising polymersomes encapsulating spike protein (ACM-001) has recently completed a Phase I clinical trial and provides a case for developing safe drug products based on ABCP delivery platforms. However, several limitations need to be resolved before they can reach their full potential. In this Perspective, we would like to highlight such aspects requiring further development for translating an ABCP-based delivery platform from a proof of concept to a viable commercial product.

Immune response to the components of lipid nanoparticles for ribonucleic acid therapeutics

Ribonucleic acid therapeutics have advantages over biologics and small molecules, including lower safety risks, cheaper costs, and extensive targeting flexibility, which is rapidly fueling the expansion of the field. This is made possible by breakthroughs in the field of drug delivery, wherein lipid nanoparticles (LNPs) are one of the most clinically advanced systems. LNP formulations that are currently approved for clinical use typically contain an ionizable cationic lipid, a phospholipid, cholesterol, and a polyethylene glycol-lipid; each contributes to the stability and/or effectiveness of LNPs. In this review, we discuss the immunomodulatory effects associated with each of the lipid components. We highlight several studies in which the components of LNPs have been implicated in cellular sensing and explore the pathways involved.

Emerging Strategies for Immunotherapy of Solid Tumors Using Lipid-Based Nanoparticles

The application of lipid-based nanoparticles for COVID-19 vaccines and transthyretin-mediated amyloidosis treatment have highlighted their potential for translation to cancer therapy. However, their use in delivering drugs to solid tumors is limited by ineffective targeting, heterogeneous organ distribution, systemic inflammatory responses, and insufficient drug accumulation at the tumor. Instead, the use of lipid-based nanoparticles to remotely activate immune system responses is an emerging effective strategy. Despite this approach showing potential for treating hematological cancers, its application to treat solid tumors is hampered by the selection of eligible targets, tumor heterogeneity, and ineffective penetration of activated T cells within the tumor. Notwithstanding, the use of lipid-based nanoparticles for immunotherapy is projected to revolutionize cancer therapy, with the ultimate goal of rendering cancer a chronic disease. However, the translational success is likely to depend on the use of predictive tumor models in preclinical studies, simulating the complexity of the tumor microenvironment (e.g., the fibrotic extracellular matrix that impairs therapeutic outcomes) and stimulating tumor progression. This review compiles recent advances in the field of antitumor lipid-based nanoparticles and highlights emerging therapeutic approaches (e.g., mechanotherapy) to modulate tumor stiffness and improve T cell infiltration, and the use of organoids to better guide therapeutic outcomes.

Nucleic acid degradation as barrier to gene delivery: a guide to understand and overcome nuclease activity

Gene therapy is on its way to revolutionize the treatment of both inherited and acquired diseases, by transferring nucleic acids to correct a disease-causing gene in the target cells of patients. In the fight against infectious diseases, mRNA-based therapeutics have proven to be a viable strategy in the recent Covid-19 pandemic. Although a growing number of gene therapies have been approved, the success rate is limited when compared to the large number of preclinical and clinical trials that have been/are being performed. In this review, we highlight some of the hurdles which gene therapies encounter after administration into the human body, with a focus on nucleic acid degradation by nucleases that are extremely abundant in mammalian organs, biological fluids as well as in subcellular compartments. We overview the available strategies to reduce the biodegradation of gene therapeutics after administration, including chemical modifications of the nucleic acids, encapsulation into vectors and co-administration with nuclease inhibitors and discuss which strategies are applied for clinically approved nucleic acid therapeutics. In the final part, we discuss the currently available methods and techniques to qualify and quantify the integrity of nucleic acids, with their own strengths and limitations.

A shift of paradigm: From avoiding nanoparticular complement activation in the field of nanomedicines to its exploitation in the context of vaccine development

The complement system plays a central role in our innate immunity to fight pathogenic microorganisms, foreign and altered cells, or any modified molecule. Consequences of complement activation include cell lysis, release of histamines, and opsonization of foreign structures in preparation for phagocytosis. Because nanoparticles interact with the immune system in various ways and can massively activate the complement system due to their virus-mimetic size and foreign texture, detrimental side effects have been described after administration like pro-inflammatory responses, inflammation, mild to severe anaphylactic crisis and potentially complement activated-related pseudoallergy (CARPA). Therefore, application of nanotherapeutics has sometimes been observed with restraint, and avoiding or even suppressing complement activation has been of utmost priority. In contrast, in the field of vaccine development, particularly protein-based immunogens that are attached to the surface of nanoparticles, may profit from complement activation regarding breadth and potency of immune response. Improved transport to the regional lymph nodes, enhanced antigen uptake and presentation, as well as beneficial effects on immune cells like B-, T- and follicular dendritic cells may be exploited by strategic nanoparticle design aimed to activate the complement system. However, a shift of paradigm regarding complement activation by nanoparticular vaccines can only be achieved if these beneficial effects are accurately elicited and overshooting effects avoided.

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.

Colorectal cancer cell exosome and cytoplasmic membrane for homotypic delivery of therapeutic molecules

Colorectal cancer (CRC) is one of the most common causes of death in the world. The multi-drug resistance, especially in metastatic colorectal cancer, drives the development of new strategies that secure a positive outcome and reduce undesirable side effects. Nanotechnology has made an impact in addressing some pharmacokinetic and safety issues related to administration of free therapeutic agents. However, demands of managing complex biointerfacing require equally complex methods for introducing stimuli-responsive or targeting elements. In order to procure a more efficient solution to the overcoming of biological barriers, the physiological functions of cancer cell plasma and exosomal membranes provided the source of highly functionalized coatings. Biomimetic nanovehicles based on colorectal cancer (CRC) membranes imparted enhanced biological compatibility, immune escape and protection to diverse classes of therapeutic molecules. When loaded with therapeutic load or used as a coating for other therapeutic nanovehicles, they provide highly efficient and selective cell targeting and uptake. This review presents a detailed overview of the recent application of homotypic biomimetic nanovehicles in the management of CRC. We also address some of the current possibilities and challenges associated with the CRC membrane biomimetics.

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.

Targeting cancer with mRNA-lipid nanoparticles: key considerations and future prospects

Harnessing mRNA-lipid nanoparticles (LNPs) to treat patients with cancer has been an ongoing research area that started before these versatile nanoparticles were successfully used as COVID-19 vaccines. Currently, efforts are underway to harness this platform for oncology therapeutics, mainly focusing on cancer vaccines targeting multiple neoantigens or direct intratumoural injections of mRNA-LNPs encoding pro-inflammatory cytokines. In this Review, we describe the opportunities of using mRNA-LNPs in oncology applications and discuss the challenges for successfully translating the findings of preclinical studies of these nanoparticles into the clinic. We critically appraise the potential of various mRNA-LNP targeting and delivery strategies, considering physiological, technological and manufacturing challenges. We explore these approaches in the context of the potential clinical applications best suited to each approach and highlight the obstacles that currently need to be addressed to achieve these applications. Finally, we provide insights from preclinical and clinical studies that are leading to this powerful platform being considered the next frontier in oncology treatment.

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.

Peptide delivery of a multivalent mRNA SARS-CoV-2 vaccine

Lipid nanoparticles (LNP) have been instrumental in the success of mRNA vaccines and have opened up the field to a new wave of therapeutics. However, what is ahead beyond the LNP? The approach herein used a nanoparticle containing a blend of Spike, Membrane and Envelope antigens complexed for the first time with the RALA peptide (RALA-SME). The physicochemical characteristics and functionality of RALA-SME were assessed. With >99% encapsulation, RALA-SME was administered via intradermal injection in vivo, and all three antigen-specific IgG antibodies were highly significant. The IgG2a:IgG1 ratio were all >1.2, indicating a robust TH1 response, and this was further confirmed with the T-Cell response in mice. A complete safety panel of markers from mice were all within normal range, supported by safety data in hamsters. Vaccination of Syrian Golden hamsters with RALA-SME derivatives produced functional antibodies capable of neutralising SARS-CoV-2 from both Wuhan-Hu-1 and Omicron BA.1 lineages after two doses. Antibody levels increased over the study period and provided protection from disease-specific weight loss, with inhibition of viral migration down the respiratory tract. This peptide technology enables the flexibility to interchange and add antigens as required, which is essential for the next generation of adaptable mRNA vaccines.

Cancer/Testis Antigens as Targets for RNA-Based Anticancer Therapy

In the last few decades, RNA-based drugs have emerged as a promising candidate in the treatment of various diseases. The introduction of messenger RNA (mRNA) as a vaccine or therapeutic agent enables the production of almost any functional protein/peptide. The key to applying RNA therapy in clinical trials is developing safe and effective delivery systems. Exosomes and lipid nanoparticles (LNPs) have been exploited as promising vehicles for drug delivery. This review discusses the feasibility of exosomes and LNPs as vehicles for mRNA delivery. Cancer/testis antigens (CTAs) show restricted expression in normal tissues and widespread expression in cancer tissues. Many of these CTAs show expression in the sera of patients with cancers. These characteristics of CTAs make them excellent targets for cancer immunotherapy. This review summarizes the roles of CTAs in various life processes and current studies on mRNAs encoding CTAs. Clinical studies present the beneficial effects of mRNAs encoding CTAs in patients with cancers. This review highlight clinical studies employing mRNA-LNPs encoding CTAs.

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.

Evolution of nanomedicine formulations for targeted delivery and controlled release

Nanotechnology research over the past several decades has been aimed primarily at improving the physicochemical properties of small molecules to produce druggable candidates as well as for tumor targeting of cytotoxic molecules. The recent focus on genomic medicine and the success of lipid nanoparticles for mRNA vaccines have provided additional impetus for the development of nanoparticle drug carriers for nucleic acid delivery, including siRNA, mRNA, DNA, and oligonucleotides, to create therapeutics that can modulate protein deregulation. Bioassays and characterizations, including trafficking assays, stability, and endosomal escape, are key to understanding the properties of these novel nanomedicine formats. We review historical nanomedicine platforms, characterization methodologies, challenges to their clinical translation, and key quality attributes for commercial translation with a view to their developability into a genomic medicine. New nanoparticle systems for immune targeting, as well as in vivo gene editing and in situ CAR therapy, are also highlighted as emerging areas.

Microfluidic approaches for producing lipid-based nanoparticles for drug delivery applications

The importance of drug delivery for disease treatment is supported by a vast literature and increasing ongoing clinical studies. Several categories of nano-based drug delivery systems have been considered in recent years, among which lipid-based nanomedicines, both artificial and cell-derived, remain the most approved. The best artificial systems in terms of biocompatibility and low toxicity are liposomes, as they are composed of phospholipids and cholesterol, the main components of cell membranes. Extracellular vesicles-biological nanoparticles released from cells-while resembling liposomes in size, shape, and structure, have a more complex composition with up to hundreds of different types of lipids, proteins, and carbohydrates in their membranes, as well as an internal cargo. Although nanoparticle technologies have revolutionized drug delivery by enabling passive and active targeting, increased stability, improved solubilization capacity, and reduced dose and adverse effects, the clinical translation remains challenging due to manufacturing limitations such as laborious and time-consuming procedures and high batch-to-batch variability. A sea change occurred when microfluidic strategies were employed, offering advantages in terms of precise particle handling, simplified workflows, higher sensitivity and specificity, and good reproducibility and stability over bulk methods. This review examines scientific advances in the microfluidics-mediated production of lipid-based nanoparticles for therapeutic applications. We will discuss the preparation of liposomes using both hydrodynamic focusing of microfluidic flow and mixing by herringbone and staggered baffle micromixers. Then, an overview on microfluidic approaches for producing extracellular vesicles and extracellular vesicles-mimetics for therapeutic applications will describe microfluidic extrusion, surface engineering, sonication, electroporation, nanoporation, and mixing. Finally, we will outline the challenges, opportunities, and future directions of microfluidic investigation of lipid-based nanoparticles in the clinic.

Levodopa-loaded nanoparticles for the treatment of Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by degeneration of dopaminergic neurons in the substantia nigra pars compacta (SNpc) resulting in dopamine (DA) deficiency, which manifests itself in motor symptoms including tremors, rigidity and bradykinesia. Current PD treatments aim at symptom reduction through oral delivery of levodopa (L-DOPA), a precursor of DA. However, L-DOPA delivery to the brain is inefficient and increased dosages are required as the disease progresses, resulting in serious side effects like dyskinesias. To improve PD treatment efficacy and to reduce side effects, recent research focuses on the encapsulation of L-DOPA into polymeric- and lipid-based nanoparticles (NPs). These formulations can protect L-DOPA from systemic decarboxylation into DA and improve L-DOPA delivery to the central nervous system. Additionally, NPs can be modified with proteins, peptides and antibodies specifically targeting the blood-brain barrier (BBB), thereby reducing required dosages and free systemic DA. Alternative delivery approaches for NP-encapsulated L-DOPA include intravenous (IV) administration, transdermal delivery using adhesive patches and direct intranasal administration, facilitating increased therapeutic DA concentrations in the brain. This review provides an overview of the recent advances for NP-mediated L-DOPA delivery to the brain, and debates challenges and future perspectives on the field.

Polysarcosine-Functionalized mRNA Lipid Nanoparticles Tailored for Immunotherapy

Lipid nanoparticles (LNPs) have gained great attention as carriers for mRNA-based therapeutics, finding applications in various indications, extending beyond their recent use in vaccines for infectious diseases. However, many aspects of LNP structure and their effects on efficacy are not well characterized. To further exploit the potential of mRNA therapeutics, better control of the relationship between LNP formulation composition with internal structure and transfection efficiency in vitro is necessary. We compared two well-established ionizable lipids, namely DODMA and MC3, in combination with two helper lipids, DOPE and DOPC, and two polymer-grafted lipids, either with polysarcosine (pSar) or polyethylene glycol (PEG). In addition to standard physicochemical characterization (size, zeta potential, RNA accessibility), small-angle X-ray scattering (SAXS) was used to analyze the structure of the LNPs. To assess biological activity, we performed transfection and cell-binding assays in human peripheral blood mononuclear cells (hPBMCs) using Thy1.1 reporter mRNA and Cy5-labeled mRNA, respectively. With the SAXS measurements, we were able to clearly reveal the effects of substituting the ionizable and helper lipid on the internal structure of the LNPs. In contrast, pSar as stealth moieties affected the LNPs in a different manner, by changing the surface morphology towards higher roughness. pSar LNPs were generally more active, where the highest transfection efficiency was achieved with the LNP formulation composition of MC3/DOPE/pSar. Our study highlights the utility of pSar for improved mRNA LNP products and the importance of pSar as a novel stealth moiety enhancing efficiency in future LNP formulation development. SAXS can provide valuable information for the rational development of such novel formulations by elucidating structural features in different LNP compositions.

Ionizable Lipid Nanoparticles for Therapeutic Base Editing of Congenital Brain Disease

Delivery of mRNA-based therapeutics to the perinatal brain holds great potential in treating congenital brain diseases. However, nonviral delivery platforms that facilitate nucleic acid delivery in this environment have yet to be rigorously studied. Here, we screen a diverse library of ionizable lipid nanoparticles (LNPs) via intracerebroventricular (ICV) injection in both fetal and neonatal mice and identify an LNP formulation with greater functional mRNA delivery in the perinatal brain than an FDA-approved industry standard LNP. Following in vitro optimization of the top-performing LNP (C3 LNP) for codelivery of an adenine base editing platform, we improve the biochemical phenotype of a lysosomal storage disease in the neonatal mouse brain, exhibit proof-of-principle mRNA brain transfection in vivo in a fetal nonhuman primate model, and demonstrate the translational potential of C3 LNPs ex vivo in human patient-derived brain tissues. These LNPs may provide a clinically translatable platform for in utero and postnatal mRNA therapies including gene editing in the brain.

Protein Corona of Anionic Fluid-Phase Liposomes Compromises Their Integrity Rather than Uptake by Cells

Despite the undisputable role of the protein corona in the biointeractions of liposome drug carriers, the field suffers from a lack of knowledge regarding the patterns of protein deposition on lipid surfaces with different compositions. Here, we investigated the protein coronas formed on liposomes of basic compositions containing combinations of egg phosphatidylcholine (PC), palmitoyloleoyl phosphatidylglycerol (POPG), and cholesterol. Liposome-protein complexes isolated by size-exclusion chromatography were delipidated and analyzed using label-free LC-MS/MS. The addition of the anionic lipid and cholesterol both affected the relative protein abundances (and not the total bound proteins) in the coronas. Highly anionic liposomes, namely those containing 40% POPG, carried corona enriched with cationic proteins (apolipoprotein C1, beta-2-glycoprotein 1, and cathelicidins) and were the least stable in the calcein release assay. Cholesterol improved the liposome stability in the plasma. However, the differences in the corona compositions had little effect on the liposome uptake by endothelial (EA.hy926) and phagocytic cells in the culture (U937) or ex vivo (blood-derived monocytes and neutrophils). The findings emphasize that the effect of protein corona on the performance of the liposomes as drug carriers occurs through compromising particle stability rather than interfering with cellular uptake.

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.

Knife's edge: Balancing immunogenicity and reactogenicity in mRNA vaccines

Since the discovery of messenger RNA (mRNA), there have been tremendous efforts to wield them in the development of therapeutics and vaccines. During the COVID-19 pandemic, two mRNA vaccines were developed and approved in record-breaking time, revolutionizing the vaccine development landscape. Although first-generation COVID-19 mRNA vaccines have demonstrated over 90% efficacy, alongside strong immunogenicity in humoral and cell-mediated immune responses, their durability has lagged compared to long-lived vaccines, such as the yellow fever vaccine. Although worldwide vaccination campaigns have saved lives estimated in the tens of millions, side effects, ranging from mild reactogenicity to rare severe diseases, have been reported. This review provides an overview and mechanistic insights into immune responses and adverse effects documented primarily for COVID-19 mRNA vaccines. Furthermore, we discuss the perspectives of this promising vaccine platform and the challenges in balancing immunogenicity and adverse effects.

Nanomaterials for antigen-specific immune tolerance therapy

Impairment of immune tolerance might cause autologous tissue damage or overactive immune response against non-pathogenic molecules. Although autoimmune disease and allergy have complicated pathologies, the current strategies have mainly focused on symptom amelioration or systemic immunosuppression which can lead to fatal adverse events. The induction of antigen-specific immune tolerance may provide therapeutic benefits to autoimmune disease and allergic response, while reducing nonspecific immune adverse responses. Diverse nanomaterials have been studied to induce antigen-specific immune tolerance therapy. This review will cover the immunological background of antigen-specific tolerance, clinical importance of antigen-specific immune tolerance, and nanomaterials designed for autoimmune and allergic diseases. As nanomaterials for modulating immune tolerances, lipid-based nanoparticles, polymeric nanoparticles, and biological carriers have been covered. Strategies to provide antigen-specific immune tolerance have been addressed. Finally, current challenges and perspectives of nanomaterials for antigen-specific immune tolerance therapy will be discussed.

Interplay between Liposomes and IgM: Principles, Challenges, and Opportunities

Liposomes have received tremendous attention as a class of versatile pharmaceutical vehicles of great potential over the past several decades. However, the application of liposomes encounters major challenges due to the knowledge gaps in their in vivo delivery process. Immunoglobulin M (IgM) displays both pervasiveness and complexity in regulating the biological functions as well as eliciting adverse effects of liposomes. Understanding, mitigating, and exploiting the duality of IgM are prerequisites for achieving various biomedical applications of liposomes. In this review, the intricate relationship between liposomes and their biological environments has been summarized, with an emphasis on the regulatory effects of IgM on in vivo performance of liposomes. Corresponding solutions have also been discussed to evade IgM-mediated opsonization for safe and efficient drug delivery.