Identification, Design and Biological Evaluation of Heterocyclic Quinolones Targeting Plasmodium falciparum Type II NADH:Quinone Oxidoreductase (PfNDH2)

High Resolution Image Download MS PowerPoint Slide Following a program undertaken to identify hit compounds against NADH:ubiquinone oxidoreductase (PfNDH2), a novel enzyme target within the malaria parasite Plasmodium falciparum, hit to lead optimization led to identification of CK-2-68, a molecule suitable for further development. In order to reduce ClogP and improve solubility of CK-2-68 incorporation of a variety of heterocycles, within the side chain of the quinolone core, was carried out, and this approach led to a lead compound SL-2-25 ( 8b ). 8b has IC 50 s in the nanomolar range versus both the enzyme and whole cell P. falciparum (IC 50 = 15 nM PfNDH2; IC 50 = 54 nM (3D7 strain of P. falciparum ) with notable oral activity of ED 50 /ED 90 of 1.87/4.72 mg/kg versus Plasmodium berghei (NS Strain) in a murine model of malaria when formulated as a phosphate salt. Analogues in this series also demonstrate nanomolar activity against the bc 1 complex of P. falciparum providing the potential added benefit of a dual mechanism of action. The potent oral activity of 2-pyridyl quinolones underlines the potential of this template for further lead optimization studies.