Receptor-directed small-molecule inhibitors of New World hemorrhagic fever mammarenavirus entry - PROJECT SUMMARY
Mammarenaviruses are endemic in rodent populations worldwide and zoonotic transmission can lead to severe
life-threatening hemorrhagic fever. In the Americas, five mammarenavirus species, including Junín and Machupo
viruses (JUNV and MACV, respectively), cause viral hemorrhagic fever. In the absence of FDA-licensed antiviral
therapies or vaccines, these viruses pose a significant public health concern and threaten national security. The
pathogenic New World mammarenaviruses (NWMs) utilize the human transferrin receptor 1 (hTfR1) for entry
into human cells. The GP1 subunit of the virus envelope glycoprotein binds to the apical domain of hTfR1, a
region that is not involved in the binding to the major hTfR1 ligands. This interaction between GP1 and hTfR1
therefore represents a potential therapeutic target for broad inhibition of NWM infection. Based on the structure
of the MACV envelope glycoprotein GP1 subunit in complex with hTfR1, we identified a novel druggable site in
the apical domain of hTfR1. A docking-based virtual screening campaign identified 28 hits that were
subsequently characterized to determine antiviral activity against JUNV infection in cell culture. Based on this
assessment, we selected two chemically distinct molecules displaying strong activity against JUNV for further
consideration. We hypothesize that targeting the apical domain pocket of hTfR1 that interacts with viral GP1
will broadly inhibit infection by all known pathogenic NWMs and thereby protect mice expressing hTfR1 from
lethal disease associated with JUNV infection. To explore this hypothesis, we will pursue the following specific
aims. Aim 1. Identify potent and broadly active compounds targeting the druggable hTfR1 apical domain
site that interacts with NWM GP1. The two distinct chemical scaffolds identified in our preliminary studies will
serve as the foundation for the design of analogs to define structure-activity relationships (SARs) important for
broad antiviral activity. We will implement an iterative campaign involving molecular modeling, medicinal
chemistry and in vitro antiviral testing against native JUNV and pseudotyped viruses displaying the envelope
glycoprotein of NWMs. Our strategy will include optimization for drug-like properties. Aim 2. Evaluate
pharmacokinetics (PK) and efficacy of optimized lead candidates in hTfR1 mice. Two optimized
compounds from each chemical scaffold will be chosen for evaluation in animals based on their in vitro potency,
selectivity, breadth of inhibition and drug-like properties. We will assess oral bioavailability, determine the
maximum tolerated dose and establish PK profiles for the lead candidates in mice. Results from these studies
will guide decisions regarding dosing levels and the frequency and duration of treatment in subsequent efficacy
studies in a validated hTfR1 mouse model of lethal JUNV infection. In addition to improved survival outcome in
JUNV-challenged hTfR1 mice, we will measure the impact of treatments on viral loads, histopathology, and
disease severity and duration. Our long-term goal is to develop a novel host-directed small-molecule therapeutic
agent that could be deployed to treat NWM hemorrhagic fevers.
