Development of broad-spectrum antiviral therapies is critical for outbreak and pandemic preparedness against emerging and reemerging viruses. Viruses inducing hemorrhagic fevers cause high morbidity and mortality in humans and are associated with several recent international outbreaks, but approved therapies for treating most of these pathogens are lacking. Here, we show that 4′-fluorouridine (4′-FlU; EIDD-2749), an orally available ribonucleoside analog, has antiviral activity against multiple hemorrhagic fever viruses in cell culture, including Nipah virus, Crimean-Congo hemorrhagic fever virus, orthohantaviruses, and arenaviruses. We performed preclinical in vivo evaluation of oral 4′-FlU against two arenaviruses, Old World Lassa virus (LASV) and New World Junín virus (JUNV), in guinea pig models of lethal disease. 4′-FlU demonstrated both advantageous pharmacokinetic characteristics and high efficacy in both of these lethal disease guinea pig models. Additional experiments supported protection of the infected animals even when 4′-FlU delivery was reduced to a low dose of 0.5 milligram per kilogram. To demonstrate clinical utility, 4′-FlU treatment was evaluated when initiated late in the course of infection (12 or 9 days after infection for LASV and JUNV, respectively). Delayed treatment resulted in rapid resolution of clinical signs, demonstrating an extended window for therapeutic intervention. These data support the use of 4′-FlU as a potent and efficacious treatment against highly pathogenic arenaviruses of public health concern with a virus inhibition profile suggesting broad-spectrum utility as an orally available antiviral drug against a wide variety of viral pathogens.

Due to their ability to inhibit viral DNA or RNA replication, nucleoside analogues have been used for decades as potent antiviral therapeutics. However, one of the major limitations of nucleoside analogues is the development of antiviral resistance. In that regard, flexible nucleoside analogues known as “fleximers” have garnered attention over the years due to their ability to survey different amino acids in enzyme binding sites, thus overcoming the potential development of antiviral resistance. Acyclic fleximers have previously demonstrated antiviral activity against numerous viruses including Middle East Respiratory Syndrome coronavirus (MERS-CoV), Ebola virus (EBOV), and, most recently, flaviviruses such as Dengue (DENV) and Yellow Fever Virus (YFV). Due to these interesting results, a Structure Activity Relationship (SAR) study was pursued in order to analyze the effect of the pyrimidine functional group and acyl protecting group on antiviral activity, cytotoxicity, and conformation. The results of those studies are presented herein.

From July–November 2020, mink (Neogale vison) on 12 Utah farms experienced an increase in mortality rates due to confirmed SARS-CoV-2 infection. We conducted epidemiologic investigations on six farms to identify the source of virus introduction, track cross-species transmission, and assess viral evolution. Interviews were conducted and specimens were collected from persons living or working on participating farms and from multiple animal species. Swabs and sera were tested by SARS-CoV-2 real-time reverse transcription polymerase chain reaction (rRT-PCR) and serological assays, respectively. Whole genome sequencing was attempted for specimens with cycle threshold values <30. Evidence of SARS-CoV-2 infection was detected by rRT-PCR or serology in ≥1 person, farmed mink, dog, and/or feral cat on each farm. Sequence analysis showed high similarity between mink and human sequences on corresponding farms. On farms sampled at multiple time points, mink tested rRT-PCR positive up to 16 weeks post-onset of increased mortality. Workers likely introduced SARS-CoV-2 to mink, and mink transmitted SARS-CoV-2 to other animal species; mink-to-human transmission was not identified. Our findings provide critical evidence to support interventions to prevent and manage SARS-CoV-2 in people and animals on mink farms and emphasizes the importance of a One Health approach to address emerging zoonoses.

Lujo virus (LUJV), a highly pathogenic arenavirus, was first identified in 2008 in Zambia. To aid the identification of effective therapeutics for LUJV, we developed a recombinant reporter virus system, confirming reporter LUJV comparability with wild-type virus and its utility in high-throughput antiviral screening assays. Using this system, we evaluated compounds with known and unknown efficacy against related arenaviruses, with the aim of identifying LUJV-specific and potential new pan-arenavirus antivirals. We identified six compounds demonstrating robust anti-LUJV activity, including several compounds with previously reported activity against other arenaviruses. These data provide critical evidence for developing broad-spectrum antivirals against high-consequence arenaviruses.

Nipah virus (NiV) causes near-annual outbreaks of fatal encephalitis and respiratory disease in South Asia with a high mortality rate (∼70%). Since there are no approved therapeutics for NiV disease in humans, the WHO has designated NiV and henipaviral diseases priority pathogens for research and development. We generated a new recombinant green fluorescent reporter NiV of the circulating Bangladesh genotype (rNiV-B-ZsG) and optimized it alongside our previously generated Malaysian genotype reporter counterpart (rNiV-M-ZsG) for antiviral screening in primary-like human respiratory cell types. Validating our platform for rNiV-B-ZsG with a synthetic compound library directed against viral RNA-dependent RNA polymerases, we identified a hit compound and confirmed its sub-micromolar activity against wild-type NiV, green fluorescent reporter, and the newly constructed bioluminescent red fluorescent double reporter (rNiV-B-BREP) NiV. We furthermore demonstrated that rNiV-B-ZsG and rNiV-B-BREP viruses showed pathogenicity comparable to wild-type NiV-B in the Syrian golden hamster model of disease, supporting additional use of these tools for both pathogenesis and advanced pre-clinical studies in vivo.