title: Targeting conserved water molecules: design of 4-aryl-5-cyanopyrrolo[2,3-d]pyrimidine Hsp90 inhibitors using fragment-based screening and structure-based optimization.
abstract: Inhibitors of the Hsp90 molecular chaperone are showing promise as anti-cancer agents. Here we describe a series of 4-aryl-5-cyanopyrrolo[2,3-d]pyrimidine ATP competitive Hsp90 inhibitors that were identified following structure-driven optimization of purine hits revealed by NMR based screening of a proprietary fragment library. Ligand-Hsp90 X-ray structures combined with molecular modeling led to the rational displacement of a conserved water molecule leading to enhanced affinity for Hsp90 as measured by fluorescence polarization, isothermal titration calorimetry and surface plasmon resonance assays. This displacement was achieved with a nitrile group, presenting an example of efficient gain in binding affinity with minimal increase in molecular weight. Some compounds in this chemical series inhibit the proliferation of human cancer cell lines in vitro and cause depletion of oncogenic Hsp90 client proteins and concomitant elevation of the co-chaperone Hsp70. In addition, one compound was demonstrated to be orally bioavailable in the mouse. This work demonstrates the power of structure-based design for the rapid evolution of potent Hsp90 inhibitors and the importance of considering conserved water molecules in drug design.
authors.affiliation: Vernalis Ltd., Granta Park, Great Abington, Cambridge, UK.
authors.forename: Nicholas G M
authors.initials: NG
authors.lastname: Davies
authors.forename: Helen
authors.initials: H
authors.lastname: Browne
authors.forename: Ben
authors.initials: B
authors.lastname: Davis
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Drysdale
authors.forename: Nicolas
authors.initials: N
authors.lastname: Foloppe
authors.forename: Stephanie
authors.initials: S
authors.lastname: Geoffrey
authors.forename: Ben
authors.initials: B
authors.lastname: Gibbons
authors.forename: Terance
authors.initials: T
authors.lastname: Hart
authors.forename: Roderick
authors.initials: R
authors.lastname: Hubbard
authors.forename: Michael Rugaard
authors.initials: MR
authors.lastname: Jensen
authors.forename: Howard
authors.initials: H
authors.lastname: Mansell
authors.forename: Andrew
authors.initials: A
authors.lastname: Massey
authors.forename: Natalia
authors.initials: N
authors.lastname: Matassova
authors.forename: Jonathan D
authors.initials: JD
authors.lastname: Moore
authors.forename: James
authors.initials: J
authors.lastname: Murray
authors.forename: Robert
authors.initials: R
authors.lastname: Pratt
authors.forename: Stuart
authors.initials: S
authors.lastname: Ray
authors.forename: Alan
authors.initials: A
authors.lastname: Robertson
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Roughley
authors.forename: Joseph
authors.initials: J
authors.lastname: Schoepfer
authors.forename: Kirsten
authors.initials: K
authors.lastname: Scriven
authors.forename: Heather
authors.initials: H
authors.lastname: Simmonite
authors.forename: Stephen
authors.initials: S
authors.lastname: Stokes
authors.forename: Allan
authors.initials: A
authors.lastname: Surgenor
authors.forename: Paul
authors.initials: P
authors.lastname: Webb
authors.forename: Mike
authors.initials: M
authors.lastname: Wood
authors.forename: Lisa
authors.initials: L
authors.lastname: Wright
authors.forename: Paul
authors.initials: P
authors.lastname: Brough
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001665:Binding Sites; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D015195:Drug Design; D045325:HCT116 Cells; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006207:Half-Life; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D062105:Molecular Docking Simulation; D011743:Pyrimidines / Q000138:chemical synthesis / Q000737:chemistry* / Q000493:pharmacokinetics; D011758:Pyrroles / Q000138:chemical synthesis / Q000737:chemistry* / Q000493:pharmacokinetics; D013329:Structure-Activity Relationship; D014867:Water / Q000737:chemistry*
chemical_list: D018841:HSP90 Heat-Shock Proteins; D011743:Pyrimidines; D011758:Pyrroles; C450639:Pyrrolo(2,3-d)pyrimidine; D014867:Water