2,3,8-Trisubstituted Quinolines with Antimalarial Activity.

Combination therapy drugs are considered a fundamental way to control malaria as it mimimizes the risk of emergence of resistance to the individual partner drugs. Consequently, this type of therapy constitutes a driving force for the discovery of new drugs with different modes of action, since this will provide options for combining different drugs to achieve the optimum antimalarial treatment. In this context, a 2,3,8-trisubstitued quinoline compound was found in a high throughput screen (HTS) to show an excellent inhibition of P. falciparum NF54 (IC50 = 22 nM) and low cytotoxicity. We performed a detailed evaluation of the substituents to improve the metabolic stability and solubility liabilities of the original hit and identified derivatives with enhanced physicochemical and/or PK properties and that maintained biological activity. However the high potency was not retained on testing against drug resistant plasmodium strains.

Novel inhibitors of Plasmodium falciparum based on 2,5-disubstituted furans.

Phenotypic HTS campaigns with a blood stage malaria assay have been used to discover novel chemotypes for malaria treatment with potential alternative mechanisms of action compared to existing agents. N1-(5-(3-Chloro-4-fluorophenyl)furan-2-yl)-N3,N3-dimethylpropane-1,3-diamine, 1 was identified as a modest inhibitor of P. falciparum NF54 (IC50 = 875 nM) with an apparent long plasma half-life after high dose oral administration to mice, although the compound later showed poor metabolic stability in liver microsomes through ring- and side chain-oxidation and N-dealkylation. We describe here the synthesis of derivatives of 1, exploring the influence of substitution patterns around the aromatic ring, variations on the alkyl chain and modifications in the core heterocycle, in order to probe potency and metabolic stability, where 4k showed a long half-life in rats.