« Back to Pipeline


Targeting the virus main protease (Mpro): interrupting virus replication

Jeong, G. U., et al. (2020). “Therapeutic Strategies Against COVID-19 and Structural Characterization of SARS-CoV-2: A Review.” Frontiers in Microbiology 11(1723).

STI-1558 is designed with the following properties:

  • STI-1558 is a prodrug, and its active form AC1115 binds to Cys-145 of catalytic domain of Mpro , which is 100% conserved in all SARS-CoV-2 variants and achieves a broad-spectrum anti-SARS-CoV-2 activity, including against the original SARS-CoV-2 strain as well as the predominant variants of concern (VOCs), such as Delta and Omicron.
  • STI-1558 is also a Cathepsin L inhibitor, which may block effective viral entry into host cells without accelerating viral mutations.
  • Oral bioavailability up to 76% with fast absorption and enhanced drug exposure in plasma allowing early treatment of COVID at home by oral administration.
  • Avoids the use of a potent  CYP34A inhibitor (e.g., ritonavir) as booster to increase the plasma exposure allowing for standalone treatment with low risk for drug interaction.
  • A drug product with robust formulation, stability and large-scale drug substance manufacture with controlled cost allowing for global accessibility and application.