Small Molecule Compounds That Inhibit Antioxidant Response Gene Expression in an Inducer-Dependent Manner

Marburg virus (MARV) causes severe disease in humans and is known to activate nuclear factor erythroid 2-related factor 2 (Nrf2), the major transcription factor of the antioxidant response. Canonical activation of Nrf2 involves oxidative or electrophilic stress that prevents Kelch-like ECH-associated protein 1 (Keap1) targeted degradation of Nrf2, leading to Nrf2 stabilization and activation of the antioxidant response. MARV activation of Nrf2 is noncanonical with the MARV VP24 protein (mVP24) interacting with Keap1, freeing Nrf2 from degradation. A high-throughput screening (HTS) assay was developed to identify inhibitors of mVP24-induced Nrf2 activity and used to screen more than 55,000 compounds. Hit compounds were further screened against secondary HTS assays for the inhibition of antioxidant activity induced by additional canonical and noncanonical mechanisms. This pipeline identified 14 compounds that suppress the response, dependent on the inducer, with 50% inhibitory concentrations below 5 μM and selectivity index values greater than 10. Notably, several of the identified compounds specifically inhibit mVP24-induced Nrf2 activity.