Systemic Exposure, Metabolism, and Elimination of [14C]-Labeled Amino Lipid, Lipid 5,After a Single Administration of mRNA Encapsulating Lipid Nanoparticles to Sprague Dawley Rats

The emerging therapeutic modality of lipid nanoparticle (LNP)-encapsulated mRNAs has demonstrated promising clinical results when used as vaccines and is currently being tested in formulations for a wide range of targeted chronic disease treatments. These therapeutics are multicomponent assemblages of well-characterized naturally occurring molecules in addition to xenobiotic molecules, whose in vivo distributions are poorly understood. Here, the metabolic outcome and in vivo elimination of Lipid 5, a key xenobiotic amino lipid in LNP formulations, were assessed after intravenous administration of 14C-labeled Lipid 5 to Sprague Dawley rats. Intact Lipid 5 was predominantly cleared from plasma within 10 h after dosing, with only small quantities (<1% of 14C dose) of a single diacid metabolite detected after 10 h. Lipid 5 was rapidly metabolized via ester hydrolysis into aliphatic alcohols and diacidic amino head group moieties, which were further metabolized via β-oxidation. Overall, >90% of the administered Lipid 5-derived 14C was recovered in urine (65%) and feces (35%), predominantly as oxidative metabolites, within 72 h after dosing, indicating rapid renal and hepatic elimination. In vitro metabolite identification after incubation with human, nonhuman primate, and rat hepatocytes showed similar metabolites to those found in vivo. No meaningful differences were observed in Lipid 5 metabolism or elimination by sex. In conclusion, Lipid 5, a critical amino lipid component of LNPs for mRNA therapeutic delivery, showed minimal exposure, rapid metabolism, and near-complete elimination of 14C metabolites in rats. Significance Statement Lipid 5 is a key component of lipid nanoparticles used for the delivery of mRNA-based medicines; understanding the rates and routes of its clearance is crucial to assessing its long-term safety in LNP technology. This study conclusively established the rapid metabolism, and near- complete elimination of intravenously administered [14C]Lipid 5 in rats via both liver and kidney as oxidative metabolites derived from ester hydrolysis and subsequent β-oxidation.

Biodistribution of Lipid 5, mRNA, and Its Translated Protein Following Intravenous Administration of mRNA-Encapsulated Lipid Nanoparticles in Rats

RNA-based therapeutics and vaccines represent a novel and expanding class of medicines, the success of which depends on the encapsulation and protection of mRNA molecules in lipid nanoparticle (LNP)-based carriers. With the development of mRNA-LNP modalities, which can incorporate xenobiotic constituents, extensive biodistribution analyses are necessary to better understand the factors that influence their in vivo exposure profiles. This study investigated the biodistribution of heptadecan-9-yl 8-((2-hydroxyethyl)(8-(nonyloxy)-8-] oxooctyl)amino)octanoate (Lipid 5)-a xenobiotic amino lipid- and its metabolites in male and female pigmented (Long-Evans) and nonpigmented (Sprague Dawley) rats by using quantitative whole-body autoradiography (QWBA) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques. After intravenous injection of Lipid 5-containing LNPs, 14C-containing Lipid 5 ([14C]Lipid 5) and radiolabeled metabolites ([14C]metabolites) were rapidly distributed, with peak concentrations reached within 1 hour in most tissues. After 10 hours, [14C]Lipid 5 and [14C]metabolites concentrated primarily in the urinary and digestive tracts. By 24 hours, [14C]Lipid 5 and [14C]metabolites were localized almost exclusively in the liver and intestines, with few or no concentrations detected in non-excretory systems, which is suggestive of hepatobiliary and renal clearance. [14C]Lipid 5 and [14C]metabolites were completely cleared within 168 hours (7 days). Biodistribution profiles were similar between QWBA and LC-MS/MS techniques, pigmented and nonpigmented rats, and male and female rats, excluding the reproductive organs. In conclusion, the rapid clearance through known excretory systems, with no evidence of redistribution for Lipid 5 or accumulation of [14C]metabolites, provides confidence for the safe and effective use of Lipid 5-containing LNPs. Significance Statement This study demonstrates the rapid, systemic distribution of intact and radiolabeled metabolites of Lipid 5, a xenobiotic amino lipid component of novel mRNA-LNP medicines, and its effective clearance without substantial redistribution after intravenous administration; additionally, findings were consistent between different mRNAs encapsulated within LNPs of similar composition. This study confirms the applicability of current analytical methods for lipid biodistribution analyses, and taken together with appropriate safety studies, supports the continued use of Lipid 5 in mRNA-medicines.

The Storage and In-Use Stability of mRNA Vaccines and Therapeutics: Not A Cold Case

The remarkable impact of mRNA vaccines on mitigating disease and improving public health has been amply demonstrated during the COVID-19 pandemic. Many new mRNA-based vaccine and therapeutic candidates are in development, yet the current reality of their stability limitations requires their frozen storage. Numerous challenges remain to improve formulated mRNA stability and enable refrigerator storage, and this review provides an update on developments to tackle this multi-faceted stability challenge. We describe the chemistry underlying mRNA degradation during storage and highlight how lipid nanoparticle (LNP) formulations are a double-edged sword: while LNPs protect mRNA against enzymatic degradation, interactions with and between LNP excipients introduce additional risks for mRNA degradation. We also discuss strategies to improve mRNA stability both as a drug substance (DS) and a drug product (DP) including the (1) design of the mRNA molecule (nucleotide selection, primary and secondary structures), (2) physical state of the mRNA-LNP complexes, (3) formulation composition and purity of the components, and (4) DS and DP manufacturing processes. Finally, we summarize analytical control strategies to monitor and assure the stability of mRNA-based candidates, and advocate for an integrated analytical and formulation development approach to further improve their storage, transport, and in-use stability profiles.

Impact of lipid nanoparticle size on mRNA vaccine immunogenicity

Lipid nanoparticles (LNP) are effective delivery vehicles for messenger RNA (mRNA) and have shown promise for vaccine applications. Yet there are no published reports detailing how LNP biophysical properties can impact vaccine performance. In our hands, a retrospective analysis of mRNA LNP vaccine in vivo studies revealed a relationship between LNP particle size and immunogenicity in mice using LNPs of various compositions. To further investigate this, we designed a series of studies to systematically change LNP particle size without altering lipid composition and evaluated biophysical properties and immunogenicity of the resulting LNPs. While small diameter LNPs were substantially less immunogenic in mice, all particle sizes tested yielded a robust immune response in non-human primates (NHP).

Naturally-occurring cholesterol analogues in lipid nanoparticles induce polymorphic shape and enhance intracellular delivery of mRNA

Endosomal sequestration of lipid-based nanoparticles (LNPs) remains a formidable barrier to delivery. Herein, structure-activity analysis of cholesterol analogues reveals that incorporation of C-24 alkyl phytosterols into LNPs (eLNPs) enhances gene transfection and the length of alkyl tail, flexibility of sterol ring and polarity due to -OH group is required to maintain high transfection. Cryo-TEM displays a polyhedral shape for eLNPs compared to spherical LNPs, while x-ray scattering shows little disparity in internal structure. eLNPs exhibit higher cellular uptake and retention, potentially leading to a steady release from the endosomes over time. 3D single-particle tracking shows enhanced intracellular diffusivity of eLNPs relative to LNPs, suggesting eLNP traffic to productive pathways for escape. Our findings show the importance of cholesterol in subcellular transport of LNPs carrying mRNA and emphasize the need for greater insights into surface composition and structural properties of nanoparticles, and their subcellular interactions which enable designs to improve endosomal escape.

Optimization of Lipid Nanoparticles for Intramuscular Administration of mRNA Vaccines

mRNA vaccines have the potential to tackle many unmet medical needs that are unable to be addressed with conventional vaccine technologies. A potent and well-tolerated delivery technology is integral to fully realizing the potential of mRNA vaccines. Pre-clinical and clinical studies have demonstrated that mRNA delivered intramuscularly (IM) with first-generation lipid nanoparticles (LNPs) generates robust immune responses. Despite progress made over the past several years, there remains significant opportunity for improvement, as the most advanced LNPs were designed for intravenous (IV) delivery of siRNA to the liver. Here, we screened a panel of proprietary biodegradable ionizable lipids for both expression and immunogenicity in a rodent model when administered IM. A subset of compounds was selected and further evaluated for tolerability, immunogenicity, and expression in rodents and non-human primates (NHPs). A lead formulation was identified that yielded a robust immune response with improved tolerability. More importantly for vaccines, increased innate immune stimulation driven by LNPs does not equate to increased immunogenicity, illustrating that mRNA vaccine tolerability can be improved without affecting potency.

A Novel Amino Lipid Series for mRNA Delivery: Improved Endosomal Escape and Sustained Pharmacology and Safety in Non-human Primates

The success of mRNA-based therapies depends on the availability of a safe and efficient delivery vehicle. Lipid nanoparticles have been identified as a viable option. However, there are concerns whether an acceptable tolerability profile for chronic dosing can be achieved. The efficiency and tolerability of lipid nanoparticles has been attributed to the amino lipid. Therefore, we developed a new series of amino lipids that address this concern. Clear structure-activity relationships were developed that resulted in a new amino lipid that affords efficient mRNA delivery in rodent and primate models with optimal pharmacokinetics. A 1-month toxicology evaluation in rat and non-human primate demonstrated no adverse events with the new lipid nanoparticle system. Mechanistic studies demonstrate that the improved efficiency can be attributed to increased endosomal escape. This effort has resulted in the first example of the ability to safely repeat dose mRNA-containing lipid nanoparticles in non-human primate at therapeutically relevant levels.

Boosting Intracellular Delivery of Lipid Nanoparticle-Encapsulated mRNA

Intracellular delivery of mRNA holds great potential for vaccine1-3 and therapeutic4 discovery and development. Despite increasing recognition of the utility of lipid-based nanoparticles (LNPs) for intracellular delivery of mRNA, particle engineering is hindered by insufficient understanding of endosomal escape, which is believed to be a main limiter of cytosolic availability and activity of the nucleic acid inside the cell. Using a series of CRISPR-based genetic perturbations of the lysosomal pathway, we have identified that late endosome/lysosome (LE/Ly) formation is essential for functional delivery of exogenously presented mRNA. Lysosomes provide a spatiotemporal hub to orchestrate mTOR signaling and are known to control cell proliferation, nutrient sensing, ribosomal biogenesis, and mRNA translation. Through modulation of the mTOR pathway we were able to enhance or inhibit LNP-mediated mRNA delivery. To further boost intracellular delivery of mRNA, we screened 212 bioactive lipid-like molecules that are either enriched in vesicular compartments or modulate cell signaling. Surprisingly, we have discovered that leukotriene-antagonists, clinically approved for treatment of asthma and other lung diseases, enhance intracellular mRNA delivery in vitro (over 3-fold, p < 0.005) and in vivo (over 2-fold, p < 0.005). Understanding LNP-mediated intracellular delivery will inspire the next generation of RNA therapeutics that have high potency and limited toxicity.

Preclinical and Clinical Demonstration of Immunogenicity by mRNA Vaccines against H10N8 and H7N9 Influenza Viruses

Recently, the World Health Organization confirmed 120 new human cases of avian H7N9 influenza in China resulting in 37 deaths, highlighting the concern for a potential pandemic and the need for an effective, safe, and high-speed vaccine production platform. Production speed and scale of mRNA-based vaccines make them ideally suited to impede potential pandemic threats. Here we show that lipid nanoparticle (LNP)-formulated, modified mRNA vaccines, encoding hemagglutinin (HA) proteins of H10N8 (A/Jiangxi-Donghu/346/2013) or H7N9 (A/Anhui/1/2013), generated rapid and robust immune responses in mice, ferrets, and nonhuman primates, as measured by hemagglutination inhibition (HAI) and microneutralization (MN) assays. A single dose of H7N9 mRNA protected mice from a lethal challenge and reduced lung viral titers in ferrets. Interim results from a first-in-human, escalating-dose, phase 1 H10N8 study show very high seroconversion rates, demonstrating robust prophylactic immunity in humans. Adverse events (AEs) were mild or moderate with only a few severe and no serious events. These data show that LNP-formulated, modified mRNA vaccines can induce protective immunogenicity with acceptable tolerability profiles.

Pharmaceutical cocrystals: along the path to improved medicines

Cocrystals, a long known but understudied class of crystalline solids, have attracted interest from crystal engineers and pharmaceutical scientists in the past decade and are now an integral part of the preformulation stage of drug development.

Complexities of particulate matter measurement in parenteral formulations of small-molecule amphiphilic drugs

Reconstituted parenteral solutions of three surface-active anti-infective small-molecule drugs and solutions of sodium dodecyl sulfate (SDS, a model surfactant) were studied to quantify the impact of sample preparation and handling on particle counts. Turbidimetry and light obscuration profiles were recorded as a function of agitation and shearing with and without the introduction of foam into the solutions. SDS solutions at concentrations above the critical micelle concentration (CMC) show significantly greater sensitivity to shear and foam presence than SDS solution below the CMC: Values of >10 μm particles increased 8 fold over control (an unsheared sample) in the micellar solution vs. 4 fold particle count increase over control at a sub-micellar concentration. An even more significant increase in the ratio of particle count in sheared/unsheared solution is seen for >25 μm unit counts, due to the increased interference of foam with the measurement. Two commercial products, injection formulations of teicoplanin and cefotaxime sodium, as well as an investigational compound 1, showed an increase in scattering as a function of foam production. The impact of foaming was significant, resulting in an increase of turbidity and light obscuration measurements in all solutions. The results illustrate some of the challenges that are inherent to optically clear, homogeneous pharmaceutical injections containing compounds which have a tendency toward self-association and surfactant-like behavior.