title: Design, synthesis and biological evaluation of novel inhibitors of Trypanosoma brucei pteridine reductase 1.
abstract: Genetic studies indicate that the enzyme pteridine reductase 1 (PTR1) is essential for the survival of the protozoan parasite Trypanosoma brucei. Herein, we describe the development and optimisation of a novel series of PTR1 inhibitors, based on benzo[d]imidazol-2-amine derivatives. Data are reported on 33 compounds. This series was initially discovered by a virtual screening campaign (J. Med. Chem., 2009, 52, 4454). The inhibitors adopted an alternative binding mode to those of the natural ligands, biopterin and dihydrobiopterin, and classical inhibitors, such as methotrexate. Using both rational medicinal chemistry and structure-based approaches, we were able to derive compounds with potent activity against T. brucei PTR1 (K(i)(app)=7 nM), which had high selectivity over both human and T. brucei dihydrofolate reductase. Unfortunately, these compounds displayed weak activity against the parasites. Kinetic studies and analysis indicate that the main reason for the lack of cell potency is due to the compounds having insufficient potency against the enzyme, which can be seen from the low K(m) to K(i) ratio (K(m)=25 nM and K(i)=2.3 nM, respectively).
authors.affiliation: Drug Discovery Unit, Division of Biological Chemistry & Drug Discovery, College of Life Sciences, University of Dundee, Sir James Black Centre, Dundee, Scotland, DD1 5EH, UK.
authors.forename: Daniel
authors.initials: D
authors.lastname: Spinks
authors.forename: Han B
authors.initials: HB
authors.lastname: Ong
authors.forename: Chidochangu P
authors.initials: CP
authors.lastname: Mpamhanga
authors.forename: Emma J
authors.initials: EJ
authors.lastname: Shanks
authors.forename: David A
authors.initials: DA
authors.lastname: Robinson
authors.forename: Iain T
authors.initials: IT
authors.lastname: Collie
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Read
authors.forename: Julie A
authors.initials: JA
authors.lastname: Frearson
authors.forename: Paul G
authors.initials: PG
authors.lastname: Wyatt
authors.forename: Ruth
authors.initials: R
authors.lastname: Brenk
authors.forename: Alan H
authors.initials: AH
authors.lastname: Fairlamb
authors.forename: Ian H
authors.initials: IH
authors.lastname: Gilbert
mesh_terms: D000818:Animals; D015195:Drug Design; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D008958:Models, Molecular; D010088:Oxidoreductases / Q000037:antagonists & inhibitors*; D013329:Structure-Activity Relationship
chemical_list: D004791:Enzyme Inhibitors; D010088:Oxidoreductases; C085592:pteridine reductase