Quantitative analysis of cholesterol oxidation products and desmosterol in parenteral liposomal pharmaceutical formulations

Excipient-related impurities in liposome drug products

Liposomes are widely used in the pharmaceutical industry as drug delivery systems to increase the efficacy and reduce the off-target toxicity of active pharmaceutical ingredients (APIs). The liposomes are more complex drug delivery systems than the traditional dosage forms, and phospholipids and cholesterol are the major structural excipients. These two excipients undergo hydrolysis and/or oxidation during liposome preparation and storage, resulting in lipids hydrolyzed products (LHPs) and cholesterol oxidation products (COPs) in the final liposomal formulations. These excipient-related impurities at elevated concentrations may affect liposome stability and exert biological functions. This review focuses on LHPs and COPs, two major categories of excipient-related impurities in the liposomal formulations, and discusses factors affecting their formation, and analytical methods to determine these excipient-related impurities.

A Reliable Quantification of Cholesterol and 25-Hydroxycholesterol in Liposomal Adjuvant Formulation by Liquid Chromatography High-Resolution Tandem Mass Spectrometry

Cholesterol, as one of the major components of liposomes, plays a critical role in modulating membrane bilayer permeability, fluidity, and structural stability. Controlling these quality attributes is essential to maintaining the efficacy and fitness of the liposomes in various applications. However, during the manufacture and storage of liposomes, cholesterol has a propensity to undergo oxidative degradation. Hence, an analytical tool that is capable of determining not only the identity and quantity of cholesterol but also its associated degradants is a prerequisite to effective process control and product quality and safety assessments. In this view, a new liquid chromatography electrospray ionization-tandem mass spectrometry (LC-ESI-MS/MS) method with parallel reaction monitoring (PRM) was developed and qualified to accurately quantify cholesterol and monitor the formation of 25-hydroxycholesterol degradant in liposomal drug formulations without the use of an isotopic internal standard (IS). The method was qualified according to the FDA Quality Guidance for Industry: Q2(R1). Study results showed that the method presents good specificity for cholesterol and 25-hydroxycholesterol detection in the liposomal matrix, good sensitivity characterized by LOD/LOQ in the nanomolar range, and accuracy within the range of 80 to 120%. The described method enables accurate evaluation of in-process and product release samples of Army Liposome Formulation with QS21 (ALFQ).

Assessing the physicochemical stability and intracellular trafficking of mRNA-based COVID-19 vaccines

The emergence of SARS-CoV-2 in Wuhan, China in 2019 has had a profound impact on humanity in every facet. While vaccines against this viral pathogen have been approved a year later, limitations to this therapeutic intervention persist, such as drug sensitivity to transportation and storage conditions, as well as significant financial losses from non-injected resuspended vials. Our research delves into the effects of thermal denaturation (4 - 40 °C) and light irradiation (720 and 10460 kJ/m2) on the mRNA-based vaccines BNT162b2 from BioNTech/Pfizer and mRNA-1273 from Moderna. We also investigated vaccine stability following incubation in syringes to simulate potential interactions with silicon oil. By assaying the effects of these stressors via biochemical and biophysical methods, we aim to elucidate the physicochemical properties, integrity, and stability of these mRNA-based vaccines. Furthermore, the incorporation of a fluorophore into both vaccines allowed us to monitor their localization within cells and assess their capacity to evade vesicular transport mechanisms, thus evaluating the differences between the two formulations. A comprehensive understanding of the aforementioned attributes can enable the establishment of optimal storage and manipulation conditions for these vaccines, thereby ensuring their safe and efficacious application while minimizing the waste of functional and safe therapeutic agents.

Polyplex designs for improving the stability and safety of RNA therapeutics

Nanoparticle-based delivery systems have contributed to the recent clinical success of RNA therapeutics, including siRNA and mRNA. RNA delivery using polymers has several distinct properties, such as enabling RNA delivery into extra-hepatic organs, modulation of immune responses to RNA, and regulation of intracellular RNA release. However, delivery systems should overcome safety and stability issues to achieve widespread therapeutic applications. Safety concerns include direct damage to cellular components, innate and adaptive immune responses, complement activation, and interaction with surrounding molecules and cells in the blood circulation. The stability of the delivery systems should balance extracellular RNA protection and controlled intracellular RNA release, which requires optimization for each RNA species. Further, polymer designs for improving safety and stability often conflict with each other. This review covers advances in polymer-based approaches to address these issues over several years, focusing on biological understanding and design concepts for delivery systems rather than material chemistry.

High-Performance Liquid Chromatography Coupled with Tandem Mass Spectrometry Method for the Identification and Quantification of Lipids in Liposomes

Liposomes are spherical, closed vesicles consisting of at least one lipid bilayer with a water chamber and are widely used to encapsulate bioactive molecules. Lipid membranes, composed of different types of lipids or lipophilic components, determine whether liposomes can achieve the desired purpose and determine the overall quality of liposomes. Thus, the quantification of lipid components and encapsulated molecules is essential to characterize and control the quality of liposomes. Moreover, multicomponent simultaneous determination is the preferred method for lipid component analysis in liposomes. Therefore, the present work describes an analytical methodology for the simultaneous determination of commonly used lipids in liposome formulations, using h igh-performance liquid chromatography coupled with a tandem mass spectrometry (MS) detector (HPLC-MS/MS). HPLC-MS/MS consists of a rapid and highly efficient chromatographic separation of the liposomal components with a C18 column and the subsequent detection of the ingredients through an MS detector, along with an accurate mass fragmentation pattern. The analytical process mainly includes lipid extraction, solution preparation, the optimization of chromatographic conditions, and method validation. We hope this analytical methodology is valuable and efficient and can be applied to the analysis of multiple types of lipids in liposomes, such as raw material quality analysis, formulation study, overall quality control, etc.

Why mRNA-ionizable LNPs formulations are so short-lived: causes and way-out

INTRODUCTION

Messenger ribonucleic acid (mRNA) and small interfering RNA (siRNA) are biological molecules that can be heated, frozen, lyophilized, precipitated, or re-suspended without degradation. Currently, ionizable lipid nanoparticles (LNPs) are a promising approach for mRNA therapy. However, the long-term shelf-life stability of mRNA-ionizable LNPs is one of the open questions about their use and safety. At an acidic pH, ionizable lipids shield anionic mRNA. However, the stability of mRNA under storage conditions remains a mystery. Moreover, ionizable LNPs excipients also cause instability during long-term storage.

AREA COVERED

This paper aims to illustrate why mRNA-ionizable LNPs have such a limited storage half-life. For the first time, we compile the tentative reasons for the short half-life and ultra-cold storage of mRNA-LNPs in the context of formulation excipients. The article also provided possible ways of prolonging the lifespan of mRNA-ionizable LNPs during long storage.

EXPERT OPINION

mRNA-ionizable LNPs are the future of genetic medicine. Current limitations of the formulation can be overcome by an advanced drying process or a whole new hybrid formulation strategy to extend the shelf life of mRNA-ionizable LNPs. A breakthrough technology may open up new research directions for producing thermostable and safe mRNA-ionizable LNPs at room temperature.

Oxysterols in stored powders as potential health hazards

Cholesterol oxidation products (COPs) have greater biological activity than cholesterol itself. Oxysterols reduce the nutritional value of foods and exhibit a wide range of biological activity, including pro-oxidant, carcinogenic, and cytotoxic properties. The most commonly detected oxysterols in foods are 7α-HC, 7β-HC, a product of their dehydrogenation 7-KC and α-CE, β-CE. The main dietary sources of oxysterols are eggs and egg-derived products, thermally processed milk and milk-based products, fried meat. This study aimed to measure the amount of cholesterol oxidation products in milk powder, egg powder and milk-egg powder during 24 months of storage. The changes in the selected oxysterols (determined by gas chromatography) were recorded. In milk powder, after the production process, the amount of cholesterol was 0.2 g 100 g^-1 fat and in egg powder it was 3.4 g 100 g^-1. After 6 months of storage, the dominant oxysterol in milk and egg powder was 7α-HC and in milk-egg powder it was 7-KC. After the storage period, oxysterols in powdered milk reached 1.81% of total cholesterol.  The most stable cholesterol was in the milk-egg mixture and its oxidation was the slowest. This study showed the presence of COPs in milk powder, egg powder and milk-egg powder and the effect of storage on cholesterol oxidation.

Lipids and Lipid Derivatives for RNA Delivery

RNA-based therapeutics have shown great promise in treating a broad spectrum of diseases through various mechanisms including knockdown of pathological genes, expression of therapeutic proteins, and programmed gene editing. Due to the inherent instability and negative-charges of RNA molecules, RNA-based therapeutics can make the most use of delivery systems to overcome biological barriers and to release the RNA payload into the cytosol. Among different types of delivery systems, lipid-based RNA delivery systems, particularly lipid nanoparticles (LNPs), have been extensively studied due to their unique properties, such as simple chemical synthesis of lipid components, scalable manufacturing processes of LNPs, and wide packaging capability. LNPs represent the most widely used delivery systems for RNA-based therapeutics, as evidenced by the clinical approvals of three LNP-RNA formulations, patisiran, BNT162b2, and mRNA-1273. This review covers recent advances of lipids, lipid derivatives, and lipid-derived macromolecules used in RNA delivery over the past several decades. We focus mainly on their chemical structures, synthetic routes, characterization, formulation methods, and structure-activity relationships. We also briefly describe the current status of representative preclinical studies and clinical trials and highlight future opportunities and challenges.

Challenges of Storage and Stability of mRNA-Based COVID-19 Vaccines

In December 2019, a new and highly pathogenic coronavirus emerged-coronavirus disease 2019 (COVID-19), a disease caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), quickly spread throughout the world. In response to this global pandemic, a few vaccines were allowed for emergency use, beginning in November 2020, of which the mRNA-based vaccines by Moderna (Moderna, Cambridge, MA, USA) and BioNTech (BioTech, Mainz, Germany)/Pfizer (Pfizer, New York, NY, USA) have been identified as the most effective ones. The mRNA platform allowed rapid development of vaccines, but their global use is limited by ultracold storage requirements. Most resource-poor countries do not have cold chain storage to execute mass vaccination. Therefore, determining strategies to increase stability of mRNA-based vaccines in relatively higher temperatures can be a game changer to address the current global pandemic and upcoming new waves. In this review, we summarized the current research strategies to enhance stability of the RNA vaccine delivery system.

Novel Timosaponin AIII-Based Multifunctional Liposomal Delivery System for Synergistic Therapy Against Hepatocellular Carcinoma Cancer

Introduction

As high cholesterol level has been reported to be associated with cancer cell growth and cholesterol is vulnerable to oxidation, the conventional liposomes including cholesterol in the formulation seem to be challenged. Timosaponin AIII (TAIII), as a steroid saponin from Anemarrhena asphodeloides Bunge, possesses a similar structure with cholesterol and exhibits a wide range of antitumor activities, making it possible to develop a TAIII-based liposome where TAIII could potentially stabilize the phospholipid bilayer as a substitution of cholesterol and work as a chemotherapeutic drug as well. Meanwhile, TAIII could enhance the uptake of doxorubicin hydrochloride (DOX) in human hepatocellular carcinoma (HCC) cells and exhibit synergistic effect. Thus, we designed a novel thermally sensitive multifunctional liposomal system composed of TAIII and lipids to deliver DOX for enhanced HCC treatment.

Methods

The synergistic effects of DOX and TAIII were explored on HCC cells and the tumor inhibition rate of TAIII-based liposomes carrying DOX was evaluated on both subcutaneous and orthotopic transplantation tumor models. TAIII-based multifunctional liposomes were characterized.

Results

Synergistic HCC cytotoxicity was achieved at molar ratios of 1:1, 1:2 and 1:4 of DOX/TAIII. TAIII-based liposomes carrying a low DOX dose of 2 mg/kg exhibited significantly enhanced antitumor activity than 5 mg/kg of DOX without detected cardiotoxicity on both subcutaneous and orthotopic transplantation tumor models. TAIII-based liposomes were characterized with smaller size than cholesterol liposomes but exhibited favorable stability. Mild hyperthermia generated by laser irradiation accelerated the release of DOX and TAIII from liposomes at tumor site, and cell permeability of TAIII enhanced uptake of DOX in HCC cells.

Conclusion

The innovative application of TAIII working as bilayer stabilizer and chemotherapeutic drug affords a stable multifunctional liposomal delivery system for synergistic therapy against HCC, which may be referred for the development of other types of saponins with similar property.

mRNA-lipid nanoparticle COVID-19 vaccines: Structure and stability

A drawback of the current mRNA-lipid nanoparticle (LNP) COVID-19 vaccines is that they have to be stored at (ultra)low temperatures. Understanding the root cause of the instability of these vaccines may help to rationally improve mRNA-LNP product stability and thereby ease the temperature conditions for storage. In this review we discuss proposed structures of mRNA-LNPs, factors that impact mRNA-LNP stability and strategies to optimize mRNA-LNP product stability. Analysis of mRNA-LNP structures reveals that mRNA, the ionizable cationic lipid and water are present in the LNP core. The neutral helper lipids are mainly positioned in the outer, encapsulating, wall. mRNA hydrolysis is the determining factor for mRNA-LNP instability. It is currently unclear how water in the LNP core interacts with the mRNA and to what extent the degradation prone sites of mRNA are protected through a coat of ionizable cationic lipids. To improve the stability of mRNA-LNP vaccines, optimization of the mRNA nucleotide composition should be prioritized. Secondly, a better understanding of the milieu the mRNA is exposed to in the core of LNPs may help to rationalize adjustments to the LNP structure to preserve mRNA integrity. Moreover, drying techniques, such as lyophilization, are promising options still to be explored.

Saponin surfactants used in drug delivery systems: A new application for natural medicine components

Saponins are a group of compounds widely distributed in the plant kingdom. Due to their amphiphilic characteristic structure, saponins have high surface activity and self-assembly property and can be used as natural biosurfactants. Therefore, saponin has become a potential drug delivery system (DDS) carrier and has attracted the attention of many researchers. Increasing studies have found that when drugs combining with saponins, their solubility or bioavailability are improved. This phenomenon may be due to a synergistic mechanism and provides a potentially novel concept for DDS: saponins may be also used for carrier materials. This review emphasized the molecular characteristics and mechanism of saponins as carriers and the research on the morphology of saponin carriers. Besides, the article also introduced the role and application of saponins in DDS. Although there are still some limitations with the application of saponins such as cost, applicability, and hemolysis, the development of technology and in-depth molecular mechanism research will provide saponins with greater application prospects as DDS carriers.

Cholesterol Reduces Partitioning of Antifungal Drug Itraconazole into Lipid Bilayers

Cholesterol plays a crucial role in modulating the physicochemical properties of biomembranes, both increasing mechanical strength and decreasing permeability. Cholesterol is also a common component of vesicle-based delivery systems, including liposome-based drug delivery systems (LDSs). However, its effect on the partitioning of drug molecules to lipid membranes is very poorly recognized. Herein, we performed a combined experimental/computational study of the potential for the use of the LDS formulation for the delivery of the antifungal drug itraconazole (ITZ). We consider the addition of cholesterol to the lipid membrane. Since ITZ is only weakly soluble in water, its bioavailability is limited. Use of an LDS has thus been proposed. We studied lipid membranes composed of cholesterol, 1-palmitoyl-2-oleoyl-sn-glycerol-3-phosphocholine (POPC), and ITZ using a combination of computational molecular dynamics (MD) simulations of lipid bilayers and Brewster angle microscopy (BAM) experiments of monolayers. Both experimental and computational results show separation of cholesterol and ITZ. Cholesterol has a strong preference to orient parallel to the bilayer normal. However, ITZ, a long and relatively rigid molecule with weakly hydrophilic groups along the backbone, predominantly locates below the interface between the hydrocarbon chain region and the polar region of the membrane, with its backbone oriented parallel to the membrane surface; the orthogonal orientation in the membrane could be the cause of the observed separation. In addition, fluorescence measurements demonstrated that the affinity of ITZ for the lipid membrane is decreased by the presence of cholesterol, which is thus probably not a suitable formulation component of an LDS designed for ITZ delivery.