Paridiprubart inhibits TLR4-dependant NF-κB activation by multiple pathogens

Respiratory pathogens such as SARS-CoV-2 and influenza can activate an exaggerated inflammatory response (cytokine storm) in the lungs that may result in acute respiratory distress syndrome (ARDS), hospitalization, and death. Therapies that target a specific pathogen (i.e. anti-virals) must, by nature, be selected after a specific diagnosis and may become ineffective due to pathogen evolution. An alternate strategy is to counter the exaggerated innate immune response present in ARDS patients using host-directed drug therapies that are agnostic to the infectious agent to overcome both of these challenges. Originally described as the innate immune receptor for lipopolysaccharide (LPS), Toll-like receptor 4 (TLR4) is now understood to be an important mediator of inflammation caused by a variety of pathogen-associated molecular patterns (PAMPs) and host-derived damage-associated molecular patterns (DAMPs). Here we show that paridiprubart, a monoclonal antibody that prevents TLR4 dimer formation, inhibits the response to TLR4 agonists including LPS, the SARS-CoV-2 spike protein, the DAMP high mobility group box 1 (HMGB1), as well as the NF-κB response to infection by both viral and bacterial pathogens. Notable in this regard, we demonstrate that SARS-CoV-2 increases HMGB1 levels, and that paridiprubart inhibits both the SARS-CoV-2 and HMGB1-triggered NF-κB response, illustrating its potential to suppress this self-amplifying inflammatory signal. We also observed that the inhibitory effect of paridiprubart is apparent when cells are exposed to the SARS-CoV-2 spike protein, which is itself a direct TLR4 agonist. In the context of active infection, paridiprubart suppressed the NF-κB-dependent response elicited by infection with SARS-CoV-2, the seasonal coronavirus 229E, influenza A virus or Haemophilus influenzae, a gram-negative bacterial pathogen. Combined, these findings reinforce the central role played by TLR4 in the inflammatory response to infection by diverse pathogens, and demonstrates the protective potential of paridiprubart-dependent inhibition of pathogenic TLR4 responses. ### Competing Interest Statement L.K., K.K., L.C., N.R., B.G., M.B are employees of Edesa Biotech. All other authors declare no competing financial interests.