Targeting the polymerase and endonuclease activities of the L protein of human pathogenic mammarenaviruses

PROJECT SUMMARY Several mammarenaviruses (MaAv), chiefly Lassa (LASV) in Western Africa and Junin (JUNV) in the Argentinean Pampas, cause hemorrhagic fever (HF) disease in humans and pose important public health problems in their endemic regions. In addition, the globally distributed MaAv lymphocytic choriomeningitis virus (LCMV) is an underrecognized human pathogen of clinical significance in neonatal infections, and a serious threat to immunocompromised people. Moreover, LASV and JUNV pose credible biodefense threats and are Category A agents. No FDA-licensed vaccines exist for MaAv, and current therapy is limited to the off-label use of ribavirin whose efficacy remains controversial. Hence, the significance to human health of developing novel therapeutics to combat human pathogenic MaAv. We have identified potent novel lead compound inhibitors of the polymerase (mCOT466) and EndoN (mCPB916) activities of the Old World (LCMV and LASV), and the distantly related New World JUNV) MaAv L proteins. The central goal of this proposal is to define the mechanisms of action, broad-spectrum anti-MaAv potential, and in vivo efficacy of these inhibitors while minimizing off-target liabilities. To reach these goals, we will complete the following studies: 1) We will use a combination of biochemical, cell-based functional, structural, and viral genetics studies to gain a detailed understanding of mCOT466 and mCPB916 mechanisms of action, mechanisms of viral escape and biological properties of drug-resistant viruses. 2) We will assess the broad-spectrum antiviral activity of mCOT466 and mCPB916 against a panel of known HF- causing MaAv, and other non-MaAv Bunyaviricetes of concern. 3) We will pursue MedChem and ADMET studies to identify mCOT466 and mCPB916 analogs/prodrugs with optimal PK, PD and TK features for their development as oral antivirals. 4) We will assess the in vivo prophylactic and therapeutic efficacy of optimized mCOT466 and mCPB916 analogs/prodrugs in mono-and combination therapy modes in validated animal models of LASV, and JUNV lethal infections. The successful completion of the proposed studies will generate the data and knowledge required for subsequent IND-enabling studies and advanced nonclinical studies for oral preclinical polymerase and EndoN inhibitors, suitable for combination therapy, with potent and broad- spectrum MaAv activity to treat infections by human pathogenic MaAv, and other non-MaAv Bunyaviricetes of concern associated with severe disease and death in humans.