Development of a high-throughput replicon assay for the identification of respiratory syncytial virus inhibitors

• We established a robust RSV replicon assay for HTS.
• This assay enabled large-scale screening for RSV replication inhibitors with low biocontainment requirement.
• The RSV replicon assay was validated by multiple RSV replication inhibitors.
• We further developed a multiplex assay that delivers both RSV replicon and cytotoxicity readouts.

Respiratory syncytial virus (RSV) drug discovery has been hindered by the lack of good chemistry starting points and would benefit from robust and convenient assays for high-throughput screening (HTS). In this paper, we present the development and optimization of a 384-well RSV replicon assay that enabled HTS for RSV replication inhibitors with a low bio-containment requirement. The established replicon assay was successfully implemented for high-throughput screening. A validation screen was performed which demonstrated high assay performance and reproducibility. Assay quality was further confirmed via demonstration of appropriate pharmacology for different classes of RSV replication tool inhibitors. RSV replicon and cytotoxicity assays were further developed into a multiplexed format that measured both inhibition of viral replication and cytotoxicity from the same well. This provided a time and cost efficient approach to support lead optimization. In summary, we have developed a robust RSV replicon assay to help expedite the discovery of novel RSV therapeutics.