Development of Diaminoquinazoline Histone Lysine Methyltransferase Inhibitors as Potent Blood-Stage Antimalarial Compounds

• Published in: ChemMedChem 2014-10, Vol.9 (10), p.2360-2373
• Main Authors: Sundriyal, Sandeep, Malmquist, Nicholas A., Caron, Joachim, Blundell, Scott, Liu, Feng, Chen, Xin, Srimongkolpithak, Nitipol, Jin, Jian, Charman, Susan A., Scherf, Artur, Fuchter, Matthew J.
• Format: Article
• Language: English
• Subjects: Animals; Antimalarials - pharmacology; Blood; diaminoquinazolines; drug design; histone methyltransferase; Histone-Lysine N-Methyltransferase - metabolism; Malaria; Plasmodium falciparum; Plasmodium falciparum - drug effects; Plasmodium falciparum - enzymology; Quinazolines - pharmacology; structure-activity relationships
• ISSN: 1860-7179; 1860-7187
• DOI: 10.1002/cmdc.201402098

Modulating epigenetic mechanisms in malarial parasites is an emerging avenue for the discovery of novel antimalarial drugs. Previously we demonstrated the potent in vitro and in vivo antimalarial activity of (1‐benzyl‐4‐piperidyl)[6,7‐dimethoxy‐2‐(4‐methyl‐1,4‐diazepin‐1‐yl)‐4‐quinazolinyl]amine (BIX01294; 1), a known human G9a inhibitor, together with its dose‐dependent effects on histone methylation in the malarial parasite. This work describes our initial medicinal chemistry efforts to optimise the diaminoquinazoline chemotype for antimalarial activity. A variety of analogues were designed by substituting the 2 and 4 positions of the quinazoline core, and these molecules were tested against Plasmodium falciparum (3D7 strain). Several analogues with IC50 values as low as 18.5 nM and with low mammalian cell toxicity (HepG2) were identified. Certain pharmacophoric features required for antimalarial activity were found to be analogous to the previously published SAR of these analogues for G9a inhibition, thereby suggesting potential similarities between the malarial and human HKMT targets of this chemotype. Physiochemical, in vitro activity, and in vitro metabolism studies were also performed for a select set of potent analogues to evaluate their potential as antimalarial leads. Parasite epigenetics: The antimalarial activities of diaminoquinazoline derivatives, known to inhibit human histone methyltransferase (HKMT, G9a/GLP) were evaluated. Results of structure–activity relationship analyses and initial in vitro studies suggest these compounds inhibit the HKMT target in malarial parasites.