title: Improved inhibitors of trypanothione reductase by combination of motifs: synthesis, inhibitory potency, binding mode, and antiprotozoal activities.
abstract: Trypanothione reductase (TR) is an essential enzyme in the trypanothione-based redox metabolism of trypanosomatid parasites. This system is absent in humans and, therefore, offers a promising target for the development of selective new drugs against African sleeping sickness and Chagas' disease. Over the past two decades, a variety of nonpeptidic small-molecule ligands of the parasitic enzyme were discovered. A current goal is to decipher the binding mode of these known inhibitors in order to optimize their structures. We analyzed the binding mode of recently reported 1-(1-(benzo[b]thiophen-2-yl)cyclohexyl)piperidine (BTCP) analogues using computer modeling methods. This led us to conclude that the analogues occupy a different region of the active site than the diaryl sulfide-based class of inhibitors. A combination of the two motifs significantly increased affinity for the enzyme compared to the respective parent compounds. The newly synthesized conjugates exhibit K(ic) values for TR as low as 0.51±0.1 μM and high selectivity for the parasitic enzyme over the related human glutathione reductase (hGR), as was predicted by our molecular modeling studies. In vitro studies showed IC(50) values in the low micromolar to submicromolar range against Trypanosoma brucei rhodesiense, often in combination with low cytotoxicity against mammalian cells. Interestingly, even stronger activities were found against Plasmodium falciparum.
authors.affiliation: Laboratorium für Organische Chemie, ETH Zürich, Hönggerberg, HCI, 8093 Zürich, Switzerland.
authors.forename: Christian
authors.initials: C
authors.lastname: Eberle
authors.forename: Birgit Sophia
authors.initials: BS
authors.lastname: Lauber
authors.forename: Daniel
authors.initials: D
authors.lastname: Fankhauser
authors.forename: Marcel
authors.initials: M
authors.lastname: Kaiser
authors.forename: Reto
authors.initials: R
authors.lastname: Brun
authors.forename: R Luise
authors.initials: RL
authors.lastname: Krauth-Siegel
authors.forename: François
authors.initials: F
authors.lastname: Diederich
mesh_terms: D020816:Amino Acid Motifs; D000981:Antiprotozoal Agents / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D015195:Drug Design; D004353:Drug Evaluation, Preclinical; D004791:Enzyme Inhibitors / Q000138:chemical synthesis / Q000378:metabolism / Q000494:pharmacology*; D008958:Models, Molecular; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors* / Q000737:chemistry / Q000378:metabolism
chemical_list: D000981:Antiprotozoal Agents; D004791:Enzyme Inhibitors; D009247:NADH, NADPH Oxidoreductases; C049608:trypanothione reductase