Overcoming thermostability challenges in mRNA-lipid nanoparticle systems with piperidine-based ionizable lipids

Engineered multi-domain lipid nanoparticles for targeted delivery

Engineered lipid nanoparticles (LNPs) represent a breakthrough in targeted drug delivery, enabling precise spatiotemporal control essential to treat complex diseases such as cancer and genetic disorders. However, the complexity of the delivery process-spanning diverse targeting strategies and biological barriers-poses significant challenges to optimizing their design. To address these, this review introduces a multi-domain framework that dissects LNPs into four domains: structure, surface, payload, and environment. Engineering challenges, functional mechanisms, and characterization strategies are analyzed across each domain, along with a discussion of advantages, limitations, and in vivo fate (e.g., biodistribution and clearance). The framework also facilitates comparisons with natural exosomes and exploration of alternative administration routes, such as intranasal and intraocular delivery. We highlight current characterization techniques, such as cryo-TEM and multiscale molecular dynamics simulations, as well as the recently emerging artificial intelligence (AI) applications-ranging from LNP structure screening to the prospective use of generative models for de novo design beyond traditional experimental and simulation paradigms. Finally, we examine how engineered LNPs integrate active, passive, endogenous, and stimuli-responsive targeting mechanisms to achieve programmable delivery, potentially surpassing biological sophistication in therapeutic performance.

Transition Temperature-Guided Design of Lipid Nanoparticles for Effective mRNA Delivery

Lipid nanoparticles (LNPs) are promising mRNA delivery vehicles due to their biocompatibility and tunable characteristics. While current rational design approaches focus on ionizable lipids' pKa and zeta potential to optimize mRNA encapsulation and endosomal escape, the selection of helper lipids remains largely empirical. We propose that the lipid transition temperature (Tm), marking the shift from the gel to the liquid crystalline phase, can guide rational helper lipid selection. Through screening 54 ionizable lipids, we identified H7T4, which displayed favorable physicochemical properties when combined with its tail variants but exhibited poor transfection efficiency. Using nano differential scanning calorimetry (nDSC) and biological small-angle X-ray scattering (BioSAXS), we found that lowering the system's Tm by combining H7T4 (high transition temperature) with a low-transition-temperature helper lipid such as 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) significantly enhanced mRNA cellular uptake both in vitro and in vivo. These findings establish Tm as a crucial parameter for a rational LNP design.

Lipid nanoparticle (LNP) mediated mRNA delivery in neurodegenerative diseases

Neurodegenerative diseases (NDD) are characterized by the progressive loss of neurons and the impairment of cellular functions. Messenger RNA (mRNA) has emerged as a promising therapy for treating NDD, as it can encode missing or dysfunctional proteins and anti-inflammatory cytokines or neuroprotective proteins to halt the progression of these diseases. However, effective mRNA delivery to the central nervous system (CNS) remains a significant challenge due to the limited penetration of the blood-brain barrier (BBB). Lipid nanoparticles (LNPs) offer an efficient solution by encapsulating and protecting mRNA, facilitating transfection and intracellular delivery. This review discusses the pathophysiological mechanisms of neurological disorders, including Parkinson's disease (PD), Alzheimer's disease (AD), multiple sclerosis (MS), Huntington's disease (HD), ischemic stroke, spinal cord injury, and Friedreich's ataxia. Additionally, it explores the potential of LNP-mediated mRNA delivery as a therapeutic strategy for these diseases. Various approaches to overcoming BBB-related challenges and enhancing the delivery and efficacy of mRNA-LNPs are discussed, including non-invasive methods with strong potential for clinical translation. With advancements in artificial intelligence (AI)-guided mRNA and LNP design, targeted delivery, gene editing, and CAR-T cell therapy, mRNA-LNPs could significantly transform the treatment landscape for NDD, paving the way for future clinical applications.

Post-encapsulation methods for the preparation of mRNA-LNPs

Microfluidics mixing is the current lab-scale method used for producing mRNA-loaded lipid nanoparticles (mRNA-LNPs) thanks to reproducibility and robustness of microfluidic mixing. Despite these advantages, the production of small LNP volumes is associated with significant material waste. Given the high cost of synthetic mRNA, this waste can be a major limitation, particularly for early-stage screening of formulations. This study proposes alternative methods for mRNA-LNP formulation aiming to improve their stability for both formulation and mRNA screening, while reducing material waste on a research scale. Specifically, we investigated post-encapsulation of mRNA into pre-formed vesicles (PFVs) obtained by microfluidic mixing. These PFVs were complexed with mRNA by: (1) a microfluidic or (2) a manual pipetting method. The resulting mRNA-LNPs produced using these two post-encapsulation methods exhibit similar physicochemical properties and morphologies to those obtained by conventional microfluidic protocol. These mRNA-LNPs were assessed on in vitro and in vivo expression. mRNA-LNPs prepared by our alternative methods showed a similar transfection level compared to the conventional formulation taken as a control. The suitability of post-encapsulation methods to other lipids, mRNAs and microfluidic systems was also confirmed. This work offers robust, simple and economic alternative methods for preparing small volumes of mRNA-LNPs. The versatility of post-encapsulation methods allows to screen mRNA formulations in a wide range of laboratories. These methods could be applied to encapsulate tailored doses of mRNA and various mRNA constructs to achieve an optimal and personalized therapy.

Immune Modulation with Oral DNA/RNA Nanoparticles

The oral delivery of DNA/RNA nanoparticles represents a transformative approach in immunotherapy and vaccine development. These nanoparticles enable targeted immune modulation by delivering genetic material to specific cells in the gut-associated immune system, triggering both mucosal and systemic immune responses. Unlike parenteral administration, the oral route offers a unique immunological environment that supports both tolerance and activation, depending on the formulation design. This review explores the underlying mechanisms of immune modulation by DNA/RNA nanoparticles, their design and delivery strategies, and recent advances in their application. Emphasis is placed on strategies to overcome physiological barriers such as acidic pH, enzymatic degradation, mucus entrapment, and epithelial tight junctions. Special attention is given to the role of gut-associated lymphoid tissue in mediating immune responses and the therapeutic potential of these systems in oral vaccine platforms, food allergies, autoimmune diseases, and chronic inflammation. Despite challenges, recent advances in nanoparticle formulation support the translation of these technologies into clinical applications for both therapeutic immunomodulation and vaccination.

Cubic Phase-Inducible Zwitterionic Phospholipids Improve the Functional Delivery of mRNA

Lipid nanoparticles (LNPs) are clinically advanced delivery systems for RNA. The extensively developed structure of ionizable lipids greatly contributes to the functional delivery of mRNA. However, endosomal escape is one of the severe biological barriers that continue to render this process inefficient (e.g., less than 10%). Although LNPs contain phospholipids, their role is poorly understood, and there have been few attempts to perform the chemical engineering required to improve their functionality. Herein, a cubic phase-inducible fusogenic zwitterionic phospholipid derived from 1,2-dioleoyl-3-sn-glycero-phosphoethanolamine (DOPE), DOPE-Cx is described, that is designed to correct this problem. The orientation of a zwitterionic head group of DOPE is engineered by attaching a series of hydrophobic moieties for zwitterionic intermolecular interaction with the head structure of phosphatidylcholine (PC), and this is followed by a lipid-phase transition into non-lamellar phases to facilitate membrane fusion-mediated endosomal escape. A structure-activity relationship study reveals that DOPE-Cx lipids with small hydrophobic chains induce cubic phases instead of a hexagonal phase when mixed with PC, which enhances the functional delivery of mRNA in the liver as opposed to the action of the typically utilized and naturally occurring phospholipids. Engineered functionalized phospholipids will be of great value for the therapeutic applications of mRNAs.

A Review on the Stability Challenges of Advanced Biologic Therapeutics

Advanced biotherapeutic systems such as gene therapy, mRNA lipid nanoparticles, antibody-drug conjugates, fusion proteins, and cell therapy have proven to be promising platforms for delivering targeted biologic therapeutics. Preserving the intrinsic stability of these advanced therapeutics is essential to maintain their innate structure, functionality, and shelf life. Nevertheless, various challenges and obstacles arise during formulation development and throughout the storage period due to their complex nature and sensitivity to various stress factors. Key stability concerns include physical degradation and chemical instability due to various factors such as fluctuations in pH and temperature, which results in conformational and colloidal instabilities of the biologics, adversely affecting their quality and therapeutic efficacy. This review emphasizes key stability issues associated with these advanced biotherapeutic systems and approaches to identify and overcome them. In gene therapy, the brittleness of viral vectors and gene encapsulation limits their stability, requiring the use of stabilizers, excipients, and lyophilization. Keeping cells viable throughout the whole cell therapy process, from culture to final formulation, is still a major difficulty. In mRNA therapeutics, stabilization strategies such as the optimization of mRNA nucleotides and lipid compositions are used to address the instability of both the mRNA and lipid nanoparticles. Monoclonal antibodies are colloidally and conformationally unstable. Hence, buffers and stabilizers are useful to maintain stability. Although fusion proteins and monoclonal antibodies share structural similarities, they show a similar pattern of instability. Antibody-drug conjugates possess issues with conjugation and linker stability. This review outlines the stability issues associated with advanced biotherapeutics and provides insights into the approaches to address these challenges.

Multicomponent thiolactone-based ionizable lipid screening platform for efficient and tunable mRNA delivery to the lungs

Ionizable lipids are essential components of lipid nanoparticles (LNPs) for efficient mRNA delivery. However, designing them for high protein expression, endosomal escape, and organ targeting is challenging due to complex structure-activity relationships. Here, we present a high-throughput platform for screening ionizable lipids using a two-step, scalable, one-pot reaction. This enabled the synthesis and vivo screening of 91 new lipids, followed by a structure-activity study, leading to the development of CP-LC-0729, which significantly surpasses the MC3 benchmark in protein expression with preliminary studies showing no in vivo toxicity. Additionally, a one-step strategy helped to yield a permanently cationic lipid which was tested in a fifth-lipid formulation, showing a highly selective lung delivery with a 32-fold increase in protein expression in vivo, outperforming current endogenous targeting strategies. All these findings underscore the potential of lipid CP-LC-0729 and our lipid platform in advancing the efficiency and specificity of mRNA delivery systems.

A novel in-vitro expression assay by LC/MS/MS enables multi-antigen mRNA vaccine characterization

The new era of messenger RNA (mRNA) vaccines has led to development of a novel, state-of-the-art characterization method for this class of molecules. Currently, flow cytometry-based assays with antigen-specific antibodies are utilized for monitoring in-vitro expression (IVE) of mRNA. Here we present development, optimization, and application of an in-vitro expression liquid chromatography tandem mass spectrometry (IVE-LC/MS/MS) assay as an orthogonal method to IVE-flow cytometry that can be used for in-depth characterization of the expressed protein antigens and monitoring their relative expression levels in the cell post-mRNA transfection. The IVE-LC/MS/MS assessment accomplished the detection of influenza hemagglutinin (HA) antigens of four distinct strains simultaneously. The workflow is presented here, highlighting the optimization of all necessary steps required for protein purification and mass spectrometry method setup. The IVE-LC/MS/MS assay is a robust and versatile technique that complements the IVE-flow cytometry method and offers several advantages, such as being antibody-free, capable of multiplexing, and highly sensitive and selective. The various studies in this work, including evaluating dose-response relationships, refining transfection protocols, and examining mRNA-LNP stability under various conditions showcase the significant benefits of applying IVE-LC/MS/MS across different experimental settings. IVE-LC/MS/MS is a powerful tool for understanding and improving the performance and quality of mRNA LNPs.

Influence of salt solution on the physicochemical properties and in vitro/ in vivo expression of mRNA/LNP

Lipid nanoparticles (LNPs) have revolutionized nucleic acid delivery, enabling significant advances in mRNA-based therapeutics. While extensive research has focused on lipid composition, the impact of preparation solutions on LNP performance remains underexplored. This study systematically investigated the effects of pH, salt type, and concentration across key preparation solutions-mRNA aqueous, dilution, exchange, and storage solutions-on the physicochemical properties, stability, and expression efficiency of SM102-based mRNA/LNPs. Findings revealed that the pH of the mRNA aqueous solution was critical, with a pH of 4 optimizing encapsulation efficiency (EE) and cellular expression. The exchange solution's pH significantly influenced biodistribution, particularly liver-specific expression following intravenous and intramuscular administration. Sucrose was identified as essential for freeze-thaw stability, with a 300 mM concentration minimizing aggregation and mRNA leakage. Furthermore, preparation solutions were shown to influence the structural integrity of LNPs, impacting their in vivo and in vitro performance. These insights highlight the importance of preparation conditions in optimizing LNP formulations for clinical applications, offering a foundation for enhanced therapeutic design and delivery.

Pharmaceutical strategies for optimized mRNA expression

Messenger RNA (mRNA)-based immunotherapies and protein in situ production therapies hold great promise for addressing theoretically all the diseases characterized by aberrant protein levels. The safe, stable, and precise delivery of mRNA to target cells via appropriate pharmaceutical strategies is a prerequisite for its optimal efficacy. In this review, we summarize the structural characteristics, mode of action, development prospects, and limitations of existing mRNA delivery systems from a pharmaceutical perspective, with an emphasis on the impacts from formulation adjustments and preparation techniques of non-viral vectors on mRNA stability, target site accumulation and transfection efficiency. In addition, we introduce strategies for synergistical combination of mRNA and small molecules to augment the potency or mitigate the adverse effects of mRNA therapeutics. Lastly, we delve into the challenges impeding the development of mRNA drugs while exploring promising avenues for future advancements.

High-Throughput Quantification and Characterization of Dual Payload mRNA/LNP Cargo via Deformulating Size Exclusion and Ion Pairing Reversed Phase Assays

Therapeutic drugs and multivalent vaccines based on the delivery of mRNA via lipid nanoparticle (LNP) technologies are expected to dominate the biopharmaceutical industry landscape in the coming years. Many of these innovative therapies include several nucleic acid components (e.g., nuclease mRNA and guide RNA) posing unique analytical challenges when monitoring the quantity and quality of each individual payload substance in the formulated LNP. Current methods were optimized for single payload analysis and often lack resolving power needed to investigate nucleic acid mixtures. Ion pairing reversed phase (IP-RP) and size exclusion chromatography (SEC) are increasingly being used to characterize nucleic acids. Here, we studied their application for payload quantification in formulated LNP drug-like products. Using a detergent to disrupt the LNPs, the liberated payloads can be separated on an octadecyl RP column using a fast gradient. Reproducible results were obtained as lipids, and surfactants were efficiently eluted using a high organic solvent wash protocol. Alternatively, we also established an online SEC disruption analysis of the mRNA/LNPs wherein an alcohol and detergent containing a mobile phase was applied. Such conditions universally deformulated all tested LNP samples, indicating that a 5 min-long SEC separation can be used as a high-throughput platform method. In both approaches, the measurements facilitate a multiattribute analysis. Apart from quantitation, the characterization of specific impurities is achieved: IP-RP reveals mRNA-lipid adducts, while SEC informs on size variants, which in turn reduces a laboratory's analytical workload. These easy-to-adopt LC-based assays are expected to fortify the analytical toolbox for emerging gene therapeutics.

Antigen Delivery Platforms for Next-Generation Coronavirus Vaccines

The COVID-19 pandemic, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), is in its sixth year and is being maintained by the inability of current spike-alone-based COVID-19 vaccines to prevent transmission leading to the continuous emergence of variants and sub-variants of concern (VOCs). This underscores the critical need for next-generation broad-spectrum pan-Coronavirus vaccines (pan-CoV vaccine) to break this cycle and end the pandemic. The development of a pan-CoV vaccine offering protection against a wide array of VOCs requires two key elements: (1) identifying protective antigens that are highly conserved between passed, current, and future VOCs; and (2) developing a safe and efficient antigen delivery system for induction of broad-based and long-lasting B- and T-cell immunity. This review will (1) present the current state of antigen delivery platforms involving a multifaceted approach, including bioinformatics, molecular and structural biology, immunology, and advanced computational methods; (2) discuss the challenges facing the development of safe and effective antigen delivery platforms; and (3) highlight the potential of nucleoside-modified mRNA encapsulated in lipid nanoparticles (LNP) as the platform that is well suited to the needs of a next-generation pan-CoV vaccine, such as the ability to induce broad-based immunity and amenable to large-scale manufacturing to safely provide durable protective immunity against current and future Coronavirus threats.

Development of Thermally Stable mRNA-LNP Delivery Systems: Current Progress and Future Prospects

The success of mRNA-LNP-based COVID-19 vaccines opens a new era for mRNA-LNP-based therapy. This breakthrough is expected to catalyze the development of more mRNA-LNP-based medicines, not only for preventive vaccines but also for therapeutic purposes. Despite the promising outlook, there are fundamental challenges impeding the progress and widespread application of mRNA-LNP formulations. One of the significant challenges is their thermal instability, requiring these products to be stored at ultralow temperatures for long-term stability. The specific requirements present significant challenges for the storage, transportation, and distribution of mRNA-LNP formulations. To effectively prepare for future infectious disease outbreaks and broaden the application of mRNA-LNP-based therapies for other illnesses, improving the thermostability of mRNA-LNP formulations is critical. In this review, we discuss the potential factors contributing to the thermal instability of mRNA-LNP formulations and examine the roles of key components such as ionizable lipids, cholesterol, pH, buffers, and stabilizing agents like sugars in maintaining their thermal stability, with the goal of providing insights that can guide the future development of thermally stable mRNA-LNP formulations.

Breaking the final barrier: Evolution of cationic and ionizable lipid structure in lipid nanoparticles to escape the endosome

In the past decade, nucleic acid therapies have seen a boon in development and clinical translation largely due to advances in nanotechnology that have enabled their safe and targeted delivery. Nanoparticles can protect nucleic acids from degradation by serum enzymes and can facilitate entry into cells. Still, achieving endosomal escape to allow nucleic acids to enter the cytoplasm has remained a significant barrier, where less than 5% of nanoparticles within the endo-lysosomal pathway are able to transfer their cargo to the cytosol. Lipid-based drug delivery vehicles, particularly lipid nanoparticles (LNPs), have been optimized to achieve potent endosomal escape, and thus have been the vector of choice in the clinic as demonstrated by their utilization in the COVID-19 mRNA vaccines. The success of LNPs is in large part due to the rational design of lipids that can specifically overcome endosomal barriers. In this review, we chart the evolution of lipid structure from cationic lipids to ionizable lipids, focusing on structure-function relationships, with a focus on how they relate to endosomal escape. Additionally, we examine recent advancements in ionizable lipid structure as well as discuss the future of lipid design.

Impact of Lipid Tail Length on the Organ Selectivity of mRNA-Lipid Nanoparticles

The delivery of mRNA molecules to organs beyond the liver is valuable for therapeutic applications. Functionalized lipid nanoparticles (LNPs) using exogenous mechanisms can regulate in vivo mRNA expression profiles from hepatocytes to extrahepatic tissues but lead to process complexity and cost escalation. Here, we report that mRNA expression gradually shifts from the liver to the spleen in an ionizable lipid tail length-dependent manner. Remarkably, this simple chemical strategy held true even when different ionizable lipid head structures were employed. As a potential mechanism underlying this discovery, our data suggest that 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) is enriched on the surface of mRNA/LNPs with short-tail lipids. This feature limits their interaction with biological components, avoiding their rapid hepatic clearance. We also show that spleen-targeting LNPs loaded with SARS-CoV-2 receptor-binding domain (RBD) mRNA can efficiently induce immune responses and neutralize activity following intramuscular vaccination priming and boosting.

The United States Food and Drug Administration's Platform Technology Designation to Expedite the Development of Drugs

Drug development costs can be significantly reduced if proven "platform" technologies are allowed to be used without having to validate their use. The most recent US Food and Drug Administration (FDA) guideline brings more clarity, as well as a greater focus on the most complex technologies that can now be used for faster drug development. The FDA has highlights the use of lipid nanoparticles (LNPs) to package and deliver mRNA vaccines, gene therapy, and short (2-20 length) synthetic nucleotides (siRNA). Additionally, monoclonal antibody cell development is targeted. The FDA provides a systematic process of requesting platform status to benefit from its advantages. It brings advanced science and rationality into regulatory steps for the FDA's approval of drugs and biologicals.