Discovery of Reversible DNA Methyltransferase and Lysine Methyltransferase G9a Inhibitors with Antitumoral in Vivo Efficacy

Using
knowledge- and structure-based approaches, we designed and
synthesized reversible chemical probes that simultaneously inhibit
the activity of two epigenetic targets, histone 3 lysine 9 methyltransferase
(G9a) and DNA methyltransferases (DNMT), at nanomolar ranges. Enzymatic
competition assays confirmed our design strategy: substrate competitive
inhibitors. Next, an initial exploration around our hit 11 was pursued to identify an adequate tool compound for in vivo testing.
In vitro treatment of different hematological neoplasia cell lines
led to the identification of molecules with clear antiproliferative
efficacies (GI50 values in the nanomolar range). On the
basis of epigenetic functional cellular responses (levels of lysine
9 methylation and 5-methylcytosine), an acceptable therapeutic window
(around 1 log unit) and a suitable pharmacokinetic profile, 12 was selected for in vivo proof-of-concept (Nat. Commun. 2017, 8, 15424). Herein, 12 achieved a significant in vivo efficacy: 70% overall tumor
growth inhibition of a human acute myeloid leukemia (AML) xenograft
in a mouse model.