Poster Presentation Australasian RNA Biology and Biotechnology Association 2025 Conference

Highly conserved siRNAs encapsulated in LNPs protect against SARS-CoV-2 (#54)

Yuan Zhang 1 , Matt Johansen 2 , Scott Ledger 1 , Ernest Moles 3 4 5 6 , Pall Thordarson 3 , Philip M. Hansbro 2 , Maria Kavallaris 3 4 5 6 , Anthony Kelleher 1 3 , Chantelle Ahlenstiel 1 3
  1. Kirby Institute, UNSW, SYDNEY, NSW, Australia
  2. Centenary Institute, University of Technology Sydney, SYDNEY, NSW, Australia
  3. RNA Institute, UNSW, SYDNEY, NSW, Australia
  4. Children's Cancer Institute, UNSW, SYDNEY, NSW, Australia
  5. Australian Centre for Nanomedicine, UNSW, SYDNEY, NSW, Australia
  6. School of Clinical Medicine, UNSW, SYDNEY, NSW, Australia

Introduction

COVID-19 has resulted in over 777 million confirmed cases and more than 7 million deaths globally. While vaccination offers protection for individuals with a functional immune system, immunocompromised populations will not generate sufficient responses. There remains a critical need for new antiviral treatments to reduce morbidity, mortality, and healthcare burden, especially to reduce hospitalisation and admission to intensive care. Small interfering RNAs (siRNAs) offer high specificity and therapeutic potential against viral infections; however, the efficiency of therapeutic delivery to non-hepatic target sites remains a challenge.

Methods

We investigated direct delivery of naked siRNA to the respiratory tract of mice via intranasal instillation and then examined three clinically relevant lipid nanoparticle (LNP) formulations that mimic the compositions of Anylam’s Onpattro, Moderna’s Spikevax, and Pfizer-BioNTech’s Comirnaty RNA-based therapeutics, to identify the optimal nanocarrier for siRNA delivery and antiviral efficacy.

Results

It is demonstrated that intranasal administration of naked siRNAs in a  K18-hACE2 transgenic SARS-CoV-2 mouse model was capable of reducing   viral mRNA levels by approximately half a log and clinical severity, evidencing their protective effect in vivo. All LNP formulations assessed showed successful delivery of siRNA to respiratory cells in vitro providing effective silencing of their targeted SARS-CoV-2 genes. However, the Alnylam-based LNP-siRNA treatment had the least off-target immune activation, with no induction of interferon stimulated genes, and remained effective when administered 24 hours post-infection.  Chemical modification of siRNA using 2’-Ome modifications further decreased any off-target immune activation, while still maintaining antiviral efficacy against SARS-CoV-2 infection. 

Conclusion

Our study demonstrates that LNP-encapsulated, chemically modified and combination siRNAs can provide an effective and mutation-resilient antiviral strategy.