Discovery of First-in-Class, Potent, and Orally Bioavailable Embryonic Ectoderm Development (EED) Inhibitor with Robust Anticancer Efficacy

Abstract

Overexpression and somatic heterozygous mutations of EZH2, the catalytic subunit of polycomb repressive complex 2 (PRC2), are associated with several tumor types. EZH2 inhibitor, EPZ-6438 (tazemetostat), demonstrated clinical efficacy in patients with acceptable safety profile as monotherapy. EED, another subunit of PRC2 complex, is essential for its histone methyltransferase activity through direct binding to trimethylated lysine 27 on histone 3 (H3K27Me3). Herein we disclose the discovery of a first-in-class potent, selective, and orally bioavailable EED inhibitor compound 43 (EED226). Guided by X-ray crystallography, compound 43 was discovered by fragmentation and regrowth of compound 7, a PRC2 HTS hit that directly binds EED. The ensuing scaffold hopping followed by multiparameter optimization led to the discovery of 43. Compound 43 induces robust and sustained tumor regression in EZH2 preclinical DLBCL model. For the first time we demonstrate that specific and direct inhibition of EED can be effective as an anticancer strategy.

Discovery and Molecular Basis of a Diverse Set of Polycomb Repressive Complex 2 Inhibitors Recognition by EED

“…Collectively, this information has been very helpful for guiding the lead optimization effort. The manuscripts for the optimization results for EED210 and EED162 will be published separately [24, 39, 40]. In conclusion, we have discovered a new class of PRC2 allosteric inhibitors through binding to EED.…”

WD40 repeat domain proteins: a novel target class?

“…EED26, another EED-targeting chemical probe, was discovered via a high-throughput campaign to find compounds inhibiting the catalytic activity of the reconstituted PRC2 complex 26 . Elucidating the mechanism of action of the screening hit enabled structure-guided fragmentation, regrowth and optimization into a potent, selective EED inhibitor 95,96 . A-395 and EED226 display target-based cellular activity and significant in vivo efficacy in mouse tumor models and are valuable chemical tools to further interrogate the role of the PRC2 complex in tumor initiation and maintenance 25,26 .…”

Exploiting Epigenetic Alterations in Prostate Cancer

“…Indeed, several recent in vitro and in vivo studies document that inhibition of EZH2 with compounds such as DZNeP and GSK126 alone (Figure 1), or in combination with other drugs, decreases prostate tumor size and proliferation [107,108]. Another essential component of the PRC2 complex is the embryonic ectoderm development protein (EED), for which selective inhibitors phenocopying EZH2 inhibitors have very recently been described [109,110,111,112]. EED inhibitors display potent in vitro and in vivo efficacy in different tumor types, also in models harboring an EZH2 mutation leading to resistance to inhibitors [109,110,111].…”

“…Another essential component of the PRC2 complex is the embryonic ectoderm development protein (EED), for which selective inhibitors phenocopying EZH2 inhibitors have very recently been described [109,110,111,112]. EED inhibitors display potent in vitro and in vivo efficacy in different tumor types, also in models harboring an EZH2 mutation leading to resistance to inhibitors [109,110,111]. It will be interesting to find out whether tumors respond differently to inhibitors of EED or EZH2 inhibitors, and this will help to understand the respective roles of the H3K27me3 mark and of EZH2, as EED inhibition effectively reduces H3K27me3 levels but probably does not affect EZH2.…”