title: Discovery of Inhibitors of Trypanosoma brucei by Phenotypic Screening of a Focused Protein Kinase Library.
abstract: A screen of a focused kinase inhibitor library against Trypanosoma brucei rhodesiense led to the identification of seven series, totaling 121 compounds, which showed >50 % inhibition at 5 μm. Screening of these hits in a T. b. brucei proliferation assay highlighted three compounds with a 1H-imidazo[4,5-b]pyrazin-2(3H)-one scaffold that showed sub-micromolar activity and excellent selectivity against the MRC5 cell line. Subsequent rounds of optimisation led to the identification of compounds that exhibited good in vitro drug metabolism and pharmacokinetics (DMPK) properties, although in general this series suffered from poor solubility. A scaffold-hopping exercise led to the identification of a 1H-pyrazolo[3,4-b]pyridine scaffold, which retained potency. A number of examples were assessed in a T. b. brucei growth assay, which could differentiate static and cidal action. Compounds from the 1H-imidazo[4,5-b]pyrazin-2(3H)-one series were found to be either static or growth-slowing and not cidal. Compounds with the 1H-pyrazolo[3,4-b]pyridine scaffold were found to be cidal and showed an unusual biphasic nature in this assay, suggesting they act by at least two mechanisms.
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Woodland
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Stephen
authors.initials: S
authors.lastname: Thompson
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Laura A T
authors.initials: LA
authors.lastname: Cleghorn
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Neil
authors.initials: N
authors.lastname: Norcross
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Manu
authors.initials: M
authors.lastname: De Rycker
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Raffaella
authors.initials: R
authors.lastname: Grimaldi
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Irene
authors.initials: I
authors.lastname: Hallyburton
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Bhavya
authors.initials: B
authors.lastname: Rao
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Suzanne
authors.initials: S
authors.lastname: Norval
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Laste
authors.initials: L
authors.lastname: Stojanovski
authors.affiliation: Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, 4002, Basel, Switzerland.
authors.forename: Reto
authors.initials: R
authors.lastname: Brun
authors.affiliation: Swiss Tropical and Public Health Institute, Socinstrasse 57, P.O. Box, 4002, Basel, Switzerland.
authors.forename: Marcel
authors.initials: M
authors.lastname: Kaiser
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Frearson
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: David W
authors.initials: DW
authors.lastname: Gray
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Wyatt
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK.
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Read
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, DD1 5EH, UK. i.h.gilbert@dundee.ac.uk.
authors.forename: Ian H
authors.initials: IH
authors.lastname: Gilbert
mesh_terms: D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D055808:Drug Discovery; D006801:Humans; D015394:Molecular Structure; D021261:Parasitic Sensitivity Tests; D010641:Phenotype; D047428:Protein Kinase Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D011494:Protein Kinases / Q000378:metabolism*; D054852:Small Molecule Libraries / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship; D016833:Trypanosoma brucei rhodesiense / Q000187:drug effects* / Q000254:growth & development
chemical_list: D047428:Protein Kinase Inhibitors; D054852:Small Molecule Libraries; D011494:Protein Kinases
keywords: Trypanosoma brucei; cidal; kinases; phenotypic; static