Discovery of ML324, a JMJD2 demethylase inhibitor with demonstrated antiviral activity

A critical and dynamic epigenetic post-translational modification involves Ne-methylation of histone lysine residues by histone methyltransferases. This process was originally thought to be an irreversible epigenetic mark, yet two representative classes of histone lysine demethylases which reverse this process are LSD1/2 and the Jumonji domain containing proteins (JMJD) have emerged. Despite an increased interest in these enzymes as a result of their suspected role in a variety of diseases (e.g. cancer and virus infection), a dearth of potent and cell-permeable inhibitors of the JMJD2 enzymes remain. As such, we sought to discover novel small molecule inhibitors of the JMJD2 family of histone demethylases via a quantitative high throughput screen and subsequent medicinal chemistry optimization campaign. Herein, we describe the discovery and optimization of N-(3-(dimethyamino)propyl-4-(8-hydroxyquinolin-6-yl)benzamide, ML324, a probe molecule that displays submicromolar inhibitory activity toward JMJD2E (in vitro) and possesses excellent in vitro ADME properties. In contrast to previously reported inhibitors of the JMJD proteins, ML324 displays excellent cell permeability providing an opportunity for more extensive cell-based studies of JMJD2 enzymes to be undertaken. In addition, ML324 demonstrates potent anti-viral activity against both herpes simplex virus (HSV) and human cytomegalovirus (hCMV) infection via inhibition viral IE gene expression. ML324 suppresses the formation of HSV plaques, even at high MOI, and blocks HSV-1 reactivation in a mouse ganglia explant model of latently infected mice. The studies described herein provide the basis for the use of JMJD2 inhibitors in proof-of-concept animal models for treatment of herpes virus infections and recurrence.