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

ABSTRACT

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.

Graphical abstract

KEYWORDS:

• Ionizable LNPs
• shelf life stability
• mRNA hydrolytic degradation
• internal structure
• hybrid formulation

Article highlights

• Although mRNA-ionizable LNPs technology represents the future of nucleic acid delivery, therapeutic applications are limited due to ultra-cold storage and short shelf life.

• Internal structural rearrangement occurs during manufacturing and storage. pH (7.4) is expected to be one of the causes of the short storage shelf life

• Water trapped inside the core-shell ionizable LNPs structure makes a significant contribution to the short half-life of mRNA breakdown during long-term storage.

• Over time, a trace amount of ethanol degrades the lipid membrane, making the formulation unstable.

• The formulation excipients and their impurities greatly contributed to the long-term instability of the mRNA-ionizable LNPs. The implementation of advanced formulation strategies or novel lipids is required to achieve mRNA stability 4°C or room temperature.

This box summarizes key points contained in the article.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Additional information

Funding

This research was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) and funded by the Ministry of Science and ICT (NRF-2020R1A2B5B01001719), Korea; also supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (BK 21four).