title: Novel inhibitor binding site discovery on HIV-1 capsid N-terminal domain by NMR and X-ray crystallography.
abstract: The HIV-1 capsid (CA) protein, a domain of Gag, which participates in formation of both the mature and immature capsid, represents a potential target for anti-viral drug development. Characterization of hits obtained via high-throughput screening of an in vitro capsid assembly assay led to multiple compounds having this potential. We previously presented the characterization of two inhibitor series that bind the N-terminal domain of the capsid (CA(NTD)), at a site located at the bottom of its helical bundle, often referred to as the CAP-1 binding site. In this work we characterize a novel series of benzimidazole hits. Initial optimization of this series led to compounds with improved in vitro assembly and anti-viral activity. Using NMR spectroscopy we found that this series binds to a unique site on CA(NTD), located at the apex of the helical bundle, well removed from previously characterized binding sites for CA inhibitors. 2D (1)H-(15)N HSQC and (19)F NMR showed that binding of the benzimidazoles to this distinct site does not affect the binding of either cyclophilin A (CypA) to the CypA-binding loop or a benzodiazepine-based CA assembly inhibitor to the CAP-1 site. Unfortunately, while compounds of this series achieved promising in vitro assembly and anti-viral effects, they also were found to be quite sensitive to a number of naturally occurring CA(NTD) polymorphisms observed among clinical isolates. Despite the negative impact of this finding for drug development, the discovery of multiple inhibitor binding sites on CA(NTD) shows that capsid assembly is much more complex than previously realized.
authors.affiliation: Department of Chemistry, Boehringer Ingelheim (Canada) Ltd , Research & Development, 2100 Cunard Street, Laval, Québec, Canada H7S 2G5.
authors.forename: Nathalie
authors.initials: N
authors.lastname: Goudreau
authors.forename: Christopher T
authors.initials: CT
authors.lastname: Lemke
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Faucher
authors.forename: Chantal
authors.initials: C
authors.lastname: Grand-Maître
authors.forename: Sylvie
authors.initials: S
authors.lastname: Goulet
authors.forename: Jean-Eric
authors.initials: JE
authors.lastname: Lacoste
authors.forename: Jean
authors.initials: J
authors.lastname: Rancourt
authors.forename: Eric
authors.initials: E
authors.lastname: Malenfant
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Mercier
authors.forename: Steve
authors.initials: S
authors.lastname: Titolo
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Mason
mesh_terms: D019380:Anti-HIV Agents / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D001562:Benzimidazoles / Q000737:chemistry; D001665:Binding Sites; D001667:Binding, Competitive; D036022:Capsid Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000378:metabolism*; D018360:Crystallography, X-Ray; D021984:Cyclophilin A / Q000378:metabolism / Q000494:pharmacology; D015497:HIV-1 / Q000235:genetics / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D011110:Polymorphism, Genetic; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: D019380:Anti-HIV Agents; D001562:Benzimidazoles; D036022:Capsid Proteins; C031000:benzimidazole; D021984:Cyclophilin A