Reversal of aberrant epigenetic silencing by small molecule inhibitors is of high interest in the fields of chemical biology and drug discovery. Full understanding of these processes is crucial for the development of truly epigenetic therapies. Histone lysine methyltransferases (HKMTs), including G9a and EZH2, are the key players in epigenetic regulation, and are involved in many diseases such as cancer. In 2009, the first substrate competitive G9a inhibitor, BIX-01294, was reported by screening a large chemical library, which paved the way for future HKMT drug discovery research.
In our research, we aimed to develop a novel substrate competitive dual G9a and EZH2 inhibitor using BIX-01294 as a prototype. Initially, the refinement of the side chain modification of BIX-01294 allowed us to understand essential Structure Activity Relationships (SAR) of the active compounds in a cell-based assay and an enzymatic assay (Chapter 2). Furthermore, the replacement of the quinazoline ring of BIX-01294 by other heteroaromatic rings was investigated (Chapter 3). While maintaining similar side chains as thosed use within the active compounds, new analogues including thieno-pyrimidine, furo-pyrimidine, purine and quinolone rings, were synthesised.
Together these efforts have resulted in new synthetic routes towards a range of di-substituted heteroaromatic analogues as well as novel quinazoline derivatives for biological assessment. Compound 35, 158, and 183 show inhibitory activities against EZH2 in the enzymatic assay and promising SAR for further optimisation. Quinoline 183 also inhibits G9a in the low nanomolar range. Several compounds show promising data in the cell-based assay. Further biological evaluation of novel heteroaromatic analogues is currently underway.