Development of an Alcohol Dilution-Lyophilization Method for the Preparation of mRNA-LNPs with Improved Storage Stability

Choice of organic solvent affects function of mRNA-LNP; pyridine produces highly functional mRNA-LNP

Lipid nanoparticles (LNPs) are well-known nanocarriers for mRNA delivery. mRNA-encapsulated LNPs (mRNA-LNPs) are prepared by alcohol dilution (broadly defined as solvent dilution) method, in which mRNA dissolved in acidic buffer is mixed with lipid dissolved in an organic solvent. Ethanol is the most commonly used organic solvent for dissolving lipids during the preparation of mRNA-LNPs. However, no studies have systematically investigated the effects of organic solvents that dissolve lipids during the preparation of mRNA-LNPs on the properties and functions of mRNA-LNPs. In this study, we prepared mRNA-LNPs by using a series of organic solvents and evaluated their characteristics. After screening, we discovered that pyridine, an organic solvent, improved the quality of mRNA-LNPs and their function in vitro and in vivo. Pyridine was applied versatilely to some lipid-composition combinations generally used in the preparation of mRNA-LNPs and can also be adapted to microfluidic-based preparation. Furthermore, with appropriate purification, the amount of pyridine remaining in the final preparation of the mRNA-LNPs was extremely low and did not affect safety. Although further mechanism-based studies are required, we conclude that pyridine is a solvent that can be applied to the production of mRNA-LNPs as a pharmaceutical product.

Formulation screening of lyophilized mRNA-lipid nanoparticles

Lipid nanoparticles (LNPs) have demonstrated their therapeutic potential as safe and effective drug delivery systems for nucleic acids during the COVID-19 pandemic. However, one of the main challenges during technical CMC (Chemistry, Manufacturing, and Controls) development is their long-term stability at temperatures of 2-8 °C or higher, which may be improved by the removal of water by lyophilization. In this study, we identified lyo-/cryo-protectants for freeze-dried mRNA-LNP formulations beyond conventional excipients such as sucrose and trehalose as Tg-modifiers using polyA as a surrogate. Hydroxypropyl-beta-cyclodextrin, Kollidon® 12 PF (PVP), and dextran 40 kDa were tested in combinations to best stabilize the mRNA-LNPs during the lyophilization process as well as during storage for up to 6 months at 2-8 °C, 25 °C/60 % r.h., and 40 °C/75 % r.h.. We also tested the formulation principle including protectants in- and outside of the LNPs. Formulations were assessed for size, PDI, encapsulation efficiency, and properties related to the lyophilized dosage form. While 10 % (w/V) sucrose formulations successfully stabilized LNPs during the lyophilization process, they were not suitable for storage at temperatures beyond 2-8 °C. The most promising formulations for storage at higher temperatures were identified as 9 % (w/V) trehalose + 1 % (w/V) PVP with only a small increase in size over 6 months at 25 °C maintaining PDI and encapsulation efficiency. Results were verified with eGFP-mRNA-LNPs and tested in cell culture experiments. This study may serve as guidance for formulation scientists to further optimize freeze-dried mRNA-LNP formulations and eventually eliminate the cold chain for mRNA-LNP products.

Recent advances in drying and development of solid formulations for stable mRNA and siRNA lipid nanoparticles

Current RNA lipid nanoparticle (LNP) based products are typically liquid formulations that require ultra-cold storage temperatures for stability. To address this limitation, recent efforts have focused on enhancing stability and enabling room temperature storage by converting these formulations into solid forms through drying processes such as lyophilization, spray drying, and spray-freeze drying. Nevertheless, the drying process itself can influence the stability of RNA/LNP formulations. Therefore, understanding the factors that contribute to instability during drying is essential. The choice of drying technique for LNPs depends on factors such as the mode of delivery, lipid components, and desired final product characteristics. Additionally, the drying mechanism and associated stresses must also be carefully considered. Drying methods involve a range of process parameters related to formulation, process settings, and the manufacturing environment. It is essential to understand how these parameters influence the final solid-state products' attributes, including appearance, moisture content, flow properties, and reconstitution time, as these can significantly affect the physical and chemical stability of the formulation. This review focuses on various drying techniques and their impact on the stability of RNA/LNP-based systems.

mRNA vaccines for infectious diseases - advances, challenges and opportunities

The concept of mRNA-based vaccines emerged more than three decades ago. Groundbreaking discoveries and technological advancements over the past 20 years have resolved the major roadblocks that initially delayed application of this new vaccine modality. The rapid development of nucleoside-modified COVID-19 mRNA vaccines demonstrated that this immunization platform is easy to develop, has an acceptable safety profile and can be produced at a large scale. The flexibility and ease of antigen design have enabled mRNA vaccines to enter development for a wide range of viruses as well as for various bacteria and parasites. However, gaps in our knowledge limit the development of next-generation mRNA vaccines with increased potency and safety. A deeper understanding of the mechanisms of action of mRNA vaccines, application of novel technologies enabling rational antigen design, and innovative vaccine delivery strategies and vaccination regimens will likely yield potent novel vaccines against a wide range of pathogens.

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.

Recent Progress in Nucleic Acid Pulmonary Delivery toward Overcoming Physiological Barriers and Improving Transfection Efficiency

Pulmonary delivery of therapeutic agents has been considered the desirable administration route for local lung disease treatment. As the latest generation of therapeutic agents, nucleic acid has been gradually developed as gene therapy for local diseases such as asthma, chronic obstructive pulmonary diseases, and lung fibrosis. The features of nucleic acid, specific physiological structure, and pathophysiological barriers of the respiratory tract have strongly affected the delivery efficiency and pulmonary bioavailability of nucleic acid, directly related to the treatment outcomes. The development of pharmaceutics and material science provides the potential for highly effective pulmonary medicine delivery. In this review, the key factors and barriers are first introduced that affect the pulmonary delivery and bioavailability of nucleic acids. The advanced inhaled materials for nucleic acid delivery are further summarized. The recent progress of platform designs for improving the pulmonary delivery efficiency of nucleic acids and their therapeutic outcomes have been systematically analyzed, with the application and the perspectives of advanced vectors for pulmonary gene delivery.

Hybrid Lipid Nanocapsules: A Robust Platform for mRNA Delivery

The success of the mRNA vaccine against COVID-19 has garnered significant interest in the development of mRNA therapeutics against other diseases, but there remains a strong need for a stable and versatile delivery platform for these therapeutics. In this study, we report on a family of robust hybrid lipid nanocapsules (hLNCs) for the delivery of mRNA. The hLNCs are composed of kolliphore HS15, labrafac lipophile WL1349, 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE), and a conjugate of oleic acid (OA) and polyethylenimines of varying size (PEI─0.8, 1.8, and 25 kDa). They are prepared by a solvent-free, temperature-phase inversion method, yielding an average size of ∼40 nm and a particle distribution index (PDI) < 0.2. We demonstrate that the PDI remains <0.2 over a wide pH range and in a wide range of medium. We further show that the PDI and the functionality of mRNA condensed on the particles are robust to drying in a sugar glass and subsequent rehydration. Finally, we demonstrate that mRNA-loaded hLNCs yield reasonable transfection in vitro and in vivo settings.

Lipid Nanoparticle (LNP) Delivery Carrier-Assisted Targeted Controlled Release mRNA Vaccines in Tumor Immunity

In recent years, lipid nanoparticles (LNPs) have attracted extensive attention in tumor immunotherapy. Targeting immune cells in cancer therapy has become a strategy of great research interest. mRNA vaccines are a potential choice for tumor immunotherapy, due to their ability to directly encode antigen proteins and stimulate a strong immune response. However, the mode of delivery and lack of stability of mRNA are key issues limiting its application. LNPs are an excellent mRNA delivery carrier, and their structural stability and biocompatibility make them an effective means for delivering mRNA to specific targets. This study summarizes the research progress in LNP delivery carrier-assisted targeted controlled release mRNA vaccines in tumor immunity. The role of LNPs in improving mRNA stability, immunogenicity, and targeting is discussed. This review aims to systematically summarize the latest research progress in LNP delivery carrier-assisted targeted controlled release mRNA vaccines in tumor immunity to provide new ideas and strategies for tumor immunotherapy, as well as to provide more effective treatment plans for patients.

Optimized biomimetic minerals maintain activity of mRNA complexes after long term storage

mRNA therapeutics can be readily designed, manufactured, and brought to scale, as demonstrated by widespread global vaccination against COVID-19. However, mRNA therapies require cold chain shipment and storage from manufacturing to administration, which may limit them to affluent communities. This problem could be addressed by mimicking the known ability of mineralized fossils to durably stabilize nucleic acids under extreme conditions. We synthesized and screened 40 calcium-phosphate minerals for their ability to store and maintain the activity of lyophilized mRNA complexes. The optimal mineral formulation incorporated mRNA complexes with high efficiency (77 %), and increased mRNA transfection efficiency by 5.6-fold. Lyophilized mRNA complexes stored with the optimized mineral formulation for 6 months at 25 °C were 3.2-fold more active than those stored with state-of-the-art excipients, but without a mineral. mRNA complexes stored with minerals at room temperature did not decline in transfection efficacy from 3 days to 6 months of storage, indicating that minerals can durably maintain activity of therapeutic mRNA complexes without cold chain storage. STATEMENT OF SIGNIFICANCE: Therapeutic mRNA, such as mRNA COVID-19 vaccines, require extensive cold chain storage that limits their general application. This work screened a library of minerals to maintain the activity of mRNA complexes with freeze-drying. The optimized mineral was able to maintain mRNA activity up to 6 months of storage at room temperature outperforming current methods of freeze-drying therapeutic mRNA complexes.