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Discovery of a Novel Respiratory Syncytial Virus Replication Inhibitor.

ABSTRACT: A high-throughput screen of a Roche internal chemical library based on inhibition of the respiratory syncytial virus (RSV)-induced cytopathic effect (CPE) on HEp-2 cells was performed to identify RSV inhibitors. Over 2,000 hits were identified and confirmed to be efficacious against RSV infection in vitro Here, we report the discovery of a triazole-oxadiazole derivative, designated triazole-1, as an RSV replication inhibitor, and we characterize its mechanism of action. Triazole-1 inhibited the replication of both RSV A and B subtypes with 50% inhibitory concentration (IC₅₀) values of approximately 1 μM, but it was not effective against other viruses, including influenza virus A, human enterovirus 71 (EV71), and vaccinia virus. Triazole-1 was shown to inhibit RSV replication when added at up to 8 h after viral entry, suggesting that it inhibits RSV after viral entry. In a minigenome reporter assay in which RSV transcription regulatory sequences flanking a luciferase gene were cotransfected with RSV N/P/L/M2-1 genes into HEp-2 cells, triazole-1 demonstrated specific and dose-dependent RSV transcription inhibitory effects. Consistent with these findings, deep sequencing of the genomes of triazole-1-resistant mutants revealed a single point mutation (A to G) at nucleotide 13546 of the RSV genome, leading to a T-to-A change at amino acid position 1684 of the L protein, which is the RSV RNA polymerase for both viral transcription and replication. The effect of triazole-1 on minigenome transcription, which was mediated by the L protein containing the T1684A mutation, was significantly reduced, suggesting that the T1684A mutation alone conferred viral resistance to triazole-1.

SUBMITTER: Wang L

PROVIDER: S-EPMC8316115 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Respiratory syncytial virus (RSV) is a leading cause of hospitalization of infants and young children, causing considerable respiratory disease and repeat infections that may lead to chronic respiratory conditions such as asthma, wheezing, and bronchitis. RSV causes ?34 million new episodes of lower respiratory tract illness (LRTI) in children younger than 5?years of age, with >3 million hospitalizations due to severe RSV-associated LRTI. The standard of care is limited to symptomatic relief as there are no approved vaccines and few effective antiviral drugs; thus, a safe and efficacious RSV therapeutic is needed. Therapeutic targeting of host proteins hijacked by RSV to facilitate replication is a promising antiviral strategy as targeting the host reduces the likelihood of developing drug resistance. The nuclear export of the RSV M protein, mediated by the nuclear export protein exportin 1 (XPO1), is crucial for RSV assembly and budding. Inhibition of RSV M protein export by leptomycin B correlated with reduced RSV replication in vitro In this study, we evaluated the anti-RSV efficacy of Verdinexor (KPT-335), a small molecule designed to reversibly inhibit XPO1-mediated nuclear export. KPT-335 inhibited XPO1-mediated transport and reduced RSV replication in vitro KPT-335 was effective against RSV A and B strains and reduced viral replication following prophylactic or therapeutic administration. Inhibition of RSV replication by KPT-335 was due to a combined effect of reduced XPO1 expression, disruption of the nuclear export of RSV M protein, and inactivation of the NF-?B signaling pathway.IMPORTANCE RSV is an important cause of LRTI in infants and young children for which there are no suitable antiviral drugs offered. We evaluated the efficacy of KPT-335 as an anti-RSV drug and show that KPT-335 inhibits XPO1-mediated nuclear export, leading to nuclear accumulation of RSV M protein and reduction in RSV levels. KPT-335 treatment also resulted in inhibition of proinflammatory pathways, which has important implications for its effectiveness in vivo.

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Discovery of a Novel Respiratory Syncytial Virus Replication Inhibitor.

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