Protein Lysine Methyltransferase G9a Inhibitors: Design, Synthesis, and Structure Activity Relationships of 2,4-Diamino-7-aminoalkoxy-quinazolines.

Abstract

Protein lysine methyltransferase G9a, which catalyzes methylation of lysine 9 of histone H3 (H3K9) and lysine 373 (K373) of p53, is over expressed in human cancers. Genetic knockdown of G9a inhibits cancer cell growth and the di-methylation of p53 K373 results in the inactivation of p53. Initial SAR exploration of the 2,4-diamino-6,7-dimethoxyquinazoline template represented by 3a (BIX01294), a selective small molecule inhibitor of G9a and GLP, led to the discovery of 10 (UNC0224) as a potent G9a inhibitor with excellent selectivity. A high resolution X-ray crystal structure of the G9a-10 complex, the first co-crystal structure of G9a with a small molecule inhibitor, was obtained. Based on the structural insights revealed by this co-crystal structure, optimization of the 7-dimethylaminopropoxy side chain of 10 resulted in the discovery of 29 (UNC0321) (Morrison K i = 63 pM), which is the first G9a inhibitor with picomolar potency and the most potent G9a inhibitor to date.

Small-molecule histone methyltransferase inhibitors display rapid antimalarial activity against all blood stage forms inPlasmodium falciparum

“…These results indicate that BIX-01294 does indeed exert an effect on parasite histone methylation levels, and this effect is not simply a consequence of parasites dying. Together with its significant precedence as an HKMT inhibitor (33)(34)(35)(36)(37)(38), this result is highly suggestive of inhibition of parasite histone methyltransferase activity.…”

“…BIX-01294 was shown to be noncompetitive for the methyl donor S-adenosylmethionine and instead competitive for the histone substrate (30,37). In light of the high precedence of this class of compounds to serve as mammalian HKMT inhibitors (33)(34)(35)(36)(37)(38), focused BIX-01294 derivatives were explored for the development of parasitespecific histone methyltransferase inhibitors in our study. Our discovery that BIX-01294-treated and TM2-115-treated P. falciparum parasites exhibit greatly reduced H3K4me3 levels in BIX-01294-treated parasites, while maintaining a distinct profile compared with human cell lines treated with BIX-01294, is highly supportive of our compounds acting as parasite histone methyltransferase inhibitors.…”

“…S1) have resulted only in very low enzymatic activity. There is evidence that this small-molecule scaffold can be tuned to effect HKMT specificity (33)(34)(35)(36)(37)(38), in particular altering activity against HKMTs other than G9a. It is highly likely that focused medicinal chemistry efforts will enable further specificity of these compounds toward their parasite targets.…”

“…BIX-01294 and analogs were synthesized according to well-established procedures (33)(34)(35)(36)(37)(38). See SI Compound Characterization Data for characterization data for BIX-01294, TM2-115, and -119.…”

“…1) was discovered in a high-throughput screen and was shown to be an inhibitor of the HKMTs G9a/GLP (30). BIX-01294 has also been used successfully in stem cell modulation (31,32), and subsequent medicinal chemistry studies have shown the potential of this scaffold in the discovery of compounds with increased potency, selectivity, and cellular permeability (33)(34)(35)(36)(37)(38). In this work, we identified two compounds that target histone methylation in P. falciparum.…”