G9a is a histone lysine methyltransferase (HKMT) involved in epigenetic regulation via the installation of histone methylation marks. 6,7-Dimethoxyquinazoline analogues, such as BIX-01294, are established as potent, substrate competitive inhibitors of G9a. With an objective to identify novel chemotypes for substrate competitive inhibitors of G9a, we have designed and synthesised a range of heterocyclic scaffolds, and investigated their ability to inhibit G9a. These studies have led to improved understanding of the key pharmacophoric features of BIX-01294 and the identification of a new core quinoline inhibitory scaffold, which retains excellent potency and high selectivity. Molecular docking was carried out to explain the observed in vitro data.