title: Effective inhibitors of the essential kinase PknB and their potential as anti-mycobacterial agents.
abstract: PknB is an essential serine/threonine kinase of Mycobacterium tuberculosis with possible roles in a number of signalling pathways involved in cell division and metabolism. We screened a library of >50,000 compounds for inhibitors of the in vitro phosphorylation of GarA (Rv1827) by PknB and identified a number of inhibitors. A program of synthetic medicinal chemistry was subsequently conducted around one class of inhibitors and was successful in generating ATP competitive inhibitors with potency in the nanomolar range. Compounds in this class showed cross-reactivity with the related M. tuberculosis kinase, PknF, but not with PknG in an in vitro autophosphorylation assay. These synthesised inhibitors were able to prevent the growth of M. tuberculosis in an Alamar blue assay and in an intracellular model of infection, but only in the micromolar range. We attempted to determine if cell wall permeability was an explanation for the discrepancy between the potent in vitro compared with relatively poor in vivo activity, but found no evidence that the activity of the inhibitors could be improved by weakening the cell wall. Despite a number of drug discovery efforts attempting to develop inhibitors against PknB, it is yet to be reported that any such inhibitors prevent mycobacterial growth at submicromolar concentrations.
authors.affiliation: Division of Mycobacterial Research, MRC National Institute for Medical Research, The Ridgeway, Mill Hill, London, NW7 1AA, United Kingdom. k.lougheed@imperial.ac.uk
authors.forename: Kathryn E A
authors.initials: KE
authors.lastname: Lougheed
authors.forename: Simon A
authors.initials: SA
authors.lastname: Osborne
authors.forename: Barbara
authors.initials: B
authors.lastname: Saxty
authors.forename: David
authors.initials: D
authors.lastname: Whalley
authors.forename: Tim
authors.initials: T
authors.lastname: Chapman
authors.forename: Nathalie
authors.initials: N
authors.lastname: Bouloc
authors.forename: Jasveen
authors.initials: J
authors.lastname: Chugh
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Nott
authors.forename: Dony
authors.initials: D
authors.lastname: Patel
authors.forename: Vicky L
authors.initials: VL
authors.lastname: Spivey
authors.forename: Catherine A
authors.initials: CA
authors.lastname: Kettleborough
authors.forename: Justin S
authors.initials: JS
authors.lastname: Bryans
authors.forename: Debra L
authors.initials: DL
authors.lastname: Taylor
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Smerdon
authors.forename: Roger S
authors.initials: RS
authors.lastname: Buxton
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D002455:Cell Division; D002478:Cells, Cultured; D055808:Drug Discovery; D006801:Humans; D008264:Macrophages / Q000187:drug effects*; D009169:Mycobacterium tuberculosis / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism; D047428:Protein Kinase Inhibitors / Q000494:pharmacology*; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors*; D015398:Signal Transduction / Q000187:drug effects; D014376:Tuberculosis / Q000188:drug therapy* / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D047428:Protein Kinase Inhibitors; C475060:PknB protein, Mycobacterium tuberculosis; D017346:Protein Serine-Threonine Kinases