PROJECT SUMMARY/ABSTRACT Human cytomegalovirus (HCMV) is the most common congenital infection worldwide and a major infectious complication after solid organ and bone marrow transplantation. A few antiviral agents are used for HCMV therapy, all target the viral DNA polymerase. Ganciclovir, and its oral formulation valganciclovir are the most commonly used agents. A terminase inhibitor was recently approved for HCMV prophylaxis after bone marrow transplantation. Ongoing therapeutic challenges stem from the side effects associated with the DNA polymerase inhibitors, emergence of resistant virus mutants during prolonged treatment courses, lack of antiviral combination regimens, and cases of refractory HCMV disease that are non-responsive to all current antivirals. These serious problems drive the drug development pipeline for HCMV. Identification of novel viral targets and viral-host interactions will lead to better control of HCMV and will reduce morbidity and mortality from this pathogen. Using the LOPAC library of 1280 pharmacologically active compounds, we identified several new hits that inhibit HCMV replication in vitro at low micro-molar concentrations. Compound ARP101 inhibited several strains of HCMV, as well as human herpesvirus (HSV) 1 and 2. In addition, ARP101 inhibited a ganciclovir resistant HCMV, indicating its mechanism of action is different from GCV. Our preliminary data show that ARP101 induces autophagy, while HCMV mostly aims to inhibit autophagy. Despite autophagy induction, its substrate p62 is also induced in infected cells treated with ARP101. We therefore hypothesize that the autophagy substrate p62 is a major hub for HCMV inhibition by ARP101, leading to a non-canonical autophagy-related pathway that overcomes HCMV replication. Our goals are: 1) Validate in detail the anti-HCMV activity of ARP101 and define its activity when used in combination with approved anti-HCMV agents ganciclovir and letermovir; 2) Delineate the autophagic proteins that are induced by ARP101 for HCMV inhibition, with a specific focus on p62, and 3) Identify the cellular target(s) of ARP101 using a cell-permeable/bioorthogonal/photolabeling derivative of ARP101, pull down assays and mass spectrometry. Success of this project will lead to in-depth target validation studies, which will in turn enable rationale design of improved derivatives of ARP101 for HCMV inhibition. Our studies will enhance our understanding of the role of autophagy during HCMV infection and its potential targeting for HCMV therapeutics in combination with direct acting antiviral agents.

PROJECT NARRATIVE Human Cytomegalovirus (HCMV) causes serious morbidity and mortality in solid organ and bone marrow transplant recipients and is the most common congenital infection worldwide. The limited treatment options for HCMV are based on inhibition of the viral DNA polymerase; therefore, discovery of new therapeutic strategies against HCMV is urgently needed. The overall aims of this proposal are to identify the mechanism(s) of action and molecular targets of a newly identified HCMV inhibitor, ARP101.