title: Mechanism of action for respiratory syncytial virus inhibitor RSV604.
abstract: Respiratory syncytial virus (RSV) is the leading cause of acute lower respiratory tract infections in young children and other high-risk populations. RSV nucleoprotein (N) is essential for virus assembly and replication as part of the viral ribonucleoprotein (RNP) complex. RSV604 was a putative N inhibitor in phase 2 clinical trials whose molecular mechanism of action (MoA) was not well understood. This study investigated the cell line-dependent potency of RSV604 and demonstrated its direct binding to the N protein in vitro, providing the first evidence of direct target engagement for this class of inhibitors reported to date. The affinity of RSV604 N binding was not affected by RSV604 resistance mutations in the N protein. RSV604 engaged in two different MoAs in HeLa cells, inhibiting both RSV RNA synthesis and the infectivity of released virus. The lack of inhibition of viral RNA synthesis in some cell lines explained the cell-type-dependent potency of the inhibitor. RSV604 did not inhibit viral RNA synthesis in the RSV subgenomic replicon cells or in the cell-free RNP assay, suggesting that it might act prior to viral replication complex formation. RSV604 did not alter N protein localization in the infected cells. Taken together, these results provide new insights leading to an understanding of the MoAs of RSV604 and other similar N inhibitors.
authors.affiliation: Infection Innovative Medicines Unit, AstraZeneca R&D Boston, Waltham, Massachusetts, USA.
authors.forename: SreeRupa
authors.initials: S
authors.lastname: Challa
authors.affiliation: Discovery Sciences, AstraZeneca, Mereside, Alderley Park, Macclesfield, Cheshire, United Kingdom.
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Scott
authors.affiliation: Infection Innovative Medicines Unit, AstraZeneca R&D Boston, Waltham, Massachusetts, USA.
authors.forename: Olga
authors.initials: O
authors.lastname: Yuzhakov
authors.affiliation: Infection Innovative Medicines Unit, AstraZeneca R&D Boston, Waltham, Massachusetts, USA.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: Infection Innovative Medicines Unit, AstraZeneca R&D Boston, Waltham, Massachusetts, USA.
authors.forename: Choi Lai
authors.initials: CL
authors.lastname: Tiong-Yip
authors.affiliation: Discovery Sciences, AstraZeneca R&D Boston, Waltham, Massachusetts, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Gao
authors.affiliation: Infection Innovative Medicines Unit, AstraZeneca R&D Boston, Waltham, Massachusetts, USA.
authors.forename: Jason
authors.initials: J
authors.lastname: Thresher
authors.affiliation: Infection Innovative Medicines Unit, AstraZeneca R&D Boston, Waltham, Massachusetts, USA qin.yu@astrazeneca.com.
authors.forename: Qin
authors.initials: Q
authors.lastname: Yu
mesh_terms: D001570:Benzodiazepinones / Q000494:pharmacology*; D002460:Cell Line; D006801:Humans; D010671:Phenylurea Compounds / Q000494:pharmacology*; D012367:RNA, Viral / Q000187:drug effects*; D012136:Respiratory Syncytial Viruses / Q000187:drug effects*; D014779:Virus Replication / Q000187:drug effects
chemical_list: C519521:1-(2-fluorophenyl)-3-(2-oxo-5-phenyl-2,3-dihydro-1H-benzo(e)(1,4)diazepin-3-yl)urea; D001570:Benzodiazepinones; D010671:Phenylurea Compounds; D012367:RNA, Viral