Delivery Strategies for mRNA Vaccines

Area of Science:

• Biotechnology and Pharmaceutical Sciences
• Vaccinology
• Molecular and Cellular Biology

Background:

• Messenger RNA (mRNA) therapeutics show promise for infectious diseases and cancer, with early successes in gene therapy.
• The first FDA-approved lipid nanoparticle (LNP)-based siRNA therapy (patisiran) in 2018 marked a milestone, driven by advances in LNP formulation.
• Key to LNP success are cationic ionizable lipids that facilitate mRNA encapsulation and endosomal release for cytosolic delivery and protein translation.

Purpose of the Study:

• To review various delivery strategies for mRNA vaccines, highlighting their components, design, and formulation challenges.
• To discuss the clinical success of LNP-mRNA vaccines, exemplified by COVID-19 vaccines from Pfizer/BioNTech and Moderna.
• To identify the need for enhanced storage stability of mRNA vaccines for broader global accessibility.

Main Methods:

• Review of existing literature on mRNA vaccine delivery systems.
• Analysis of LNP formulation components, including cationic ionizable lipids and their pKa.
• Examination of alternative delivery vehicles such as cationic nano emulsions (CNEs).

Main Results:

• Lipid nanoparticles (LNPs) protect mRNA from degradation and facilitate its delivery to the cytosol for antigen production.
• Clinically successful COVID-19 mRNA vaccines utilize LNP technology, demonstrating its efficacy.
• Various delivery strategies, including naked mRNA, ex vivo loading, CNEs, cationic peptides, and polymers, have been explored.

Conclusions:

• LNPs are a successful delivery vehicle for mRNA vaccines, enabling therapeutic applications.
• Further optimization of LNP formulations is required to address challenges like storage stability.
• Enhancing the thermostability of mRNA vaccines above 0°C is essential for equitable distribution, particularly in developing regions.