STING Agonist Induced Innate Immune Responses Drive Anti-Respiratory Virus Activity <i>In Vitro</i> with Limited Antiviral Efficacy <i>In Vivo</i>

The emergence of SARS-CoV-2 and seasonal outbreaks of other respiratory viruses highlight the urgent need for broad-spectrum antivirals to treat respiratory tract infections. Stimulator of interferon genes (STING) is a key component of innate immune signaling and plays a critical role in protection of the host against viral infections. Previously the STING agonist diABZI-4, a diamidobenzimidazole-based compound, demonstrated protection against SARS-CoV-2 both <i>in vitro</i> and <i>in vivo</i>. However, its broad-spectrum antiviral activity against other respiratory viruses in human airway epithelial cells, which are the primary targets of these infections, is not well established. In this study, we demonstrated that diABZI-4 stimulated robust innate immune responses protecting lung cells against a wide range of respiratory viruses, including influenza A virus (IAV), common cold coronaviruses, SARS-CoV-2, human rhinovirus (HRV), and human parainfluenza virus. diABZI-4 was highly active in physiologically relevant human airway epithelial tissues grown at the air-liquid interface, blocking replication of IAV, SARS-CoV-2, and HRV in these tissues. Furthermore, treatment of macrophages with diABZI-4 resulted in the secretion of cytokines that protected the primary airway epithelial cells from IAV infection. Despite the promising <i>in vitro</i> pan-antiviral activity, intranasal administration of diABZI-4 in mice provided early, but not sustained, inhibition of IAV replication in the lungs. These data highlight the complexities of the relationship between timing of STING agonist-driven inflammatory responses and viral replication dynamics, emphasizing the development challenge posed by STING agonists as potential therapeutics against respiratory viruses.