Oral Presentation Australasian RNA Biology and Biotechnology Association 2025 Conference

The HERACLES Trial: Novel 3-base Oligonucleotide Therapeutic Antagonises TLR7/8 in Autoimmune Skin Disease (127431)

Mary Speir 1 2 3 4 , Daniel S Wenholz 1 4 , Sunil Sapkota 2 3 , W. Samantha N Jayasekara 2 3 , Michael P Gantier 2 3 , Olivier F Laczka 1 4
  1. Noxopharm Ltd, Castle Hill, NSW, Australia
  2. Centre for Innate Immunity and Infectious Disease, Hudson Institute of Medical Research, Melbourne, VIC, Australia
  3. Department of Molecular and Translational Science, Monash University, Melbourne, VIC, Australia
  4. Pharmorage Pty ltd, Sydney, NSW, Australia

Toll-like receptor (TLR) 7 and TLR8 are innate immune sensors that trigger pro-inflammatory cytokine and Type-I interferon production in response to short RNA fragments. Several studies have now definitively linked aberrant TLR7 activation to both systemic and cutaneous forms of lupus erythematosus in humans1-4. We have recently uncovered a novel mechanism for TLR7/8 regulation, whereby naturally-occurring 2′-O-methyl (2′-OMe)-modified RNA fragments, as short as 3-bases, potently antagonise TLR7 and TLR8 at steady-state to prevent autoimmunity5. Accordingly, synthetic RNA-like 3-base oligonucleotide mimetic can be rationally designed to bind to TLR7 and TLR8 to effectively block their activation.

 

Based on this discovery, we undertook medicinal chemistry studies to develop a high affinity oligonucleotide drug candidate with dual antagonistic activities on human TLR7 and TLR8 (named SOF-16). Using a multi-step formulation development process with excipient screening and extensive characterisation, including stability, in vitro permeation and release testing, pharmacokinetic and biological activity assays, we have now developed SOF-SKN; a proprietary topical formulation that uses Pharmacopoeia-compliant excipients to provide sustained delivery of SOF-16 to TLR7/8-expressing immune cells in the dermis. In a murine model of skin inflammation induced by topical application of Aldara™ cream (containing the TLR7 agonist imiquimod), SOF-SKN was able to blunt inflammatory gene expression and ameliorate clinical signs of inflammation (redness and scaliness). To-date, SOF-SKN has also demonstrated an excellent safety profile in non-clinical safety/toxicity studies both in vitro and in vivo.

 

Our results establish that select chemically modified 3-base oligonucleotides can be rationally designed and optimised to effectively antagonise TLR7/8 and dampen skin autoimmunity. SOF-SKN is currently intended as a first-line topical treatment for cutaneous lupus erythematosus (CLE), with a Phase I clinical trial – HERACLES (Harnessing Endogenous Regulators Against CLE Study) – underway in Australia. To our knowledge, this is the first topical formulation of an oligonucleotide to reach clinical development.

  1. Brown, G.J., et al., TLR7 gain-of-function genetic variation causes human lupus. Nature, 2022. 605(7909): p. 349-356.
  2. Mishra, H., et al., Disrupted degradative sorting of TLR7 is associated with human lupus. Sci. Immunol., 2024. 9(92): p. eadi9575.
  3. Wolf, C., et al., UNC93B1 variants underlie TLR7-dependent autoimmunity. Sci. Immunol., 2024. 9(92): p. eadi9769.
  4. David, C., et al., Interface Gain-of-Function Mutations in TLR7 Cause Systemic and Neuro-inflammatory Disease. J Clin Immunol, 2024. 44(2): p. 60.
  5. Alharbi, A.S., et al., 2’-O-Methyl-guanosine 3-base RNA fragments mediate essential natural TLR7/8 antagonism. BioRxiv 2024.