An Allosteric PRC2 Inhibitor Targeting EED Suppresses Tumor Progression by Modulating the Immune Response

Abstract

Aberrant activity of polycomb repressive complex 2 (PRC2) is involved in a wide range of human cancer progression. The WD40 repeat-containing protein EED is a core component of PRC2 and enhances PRC2 activity through interaction with H3K27me3. In this study, we report the discovery of a class of pyrimidone compounds, represented by BR-001, as potent allosteric inhibitors of PRC2. X-ray co-crystallography showed that BR-001 directly binds EED in the H3K27me3-binding pocket. BR-001 displayed antitumor potency in vitro and in vivo. In Karpas422 and Pfeiffer xenograft mouse models, twice daily oral dosing with BR-001 resulted in robust antitumor activity. BR-001 was also efficacious in syngeneic CT26 colon tumor-bearing mice; oral dosing of 30 mg/kg of BR-001 led to 59.3% tumor growth suppression and increased frequency of effector CD8 þ T-cell infiltrates in tumors. Pharmacodynamic analysis revealed that CXCL10 was highly upregulated, suggesting that CXCL10 triggers the trafficking of CD8 þ T cells toward tumor sites. Our results demonstrate for the first time that inhibition of EED modulates the tumor immune microenvironment to induce regression of colon tumors and therefore has the potential to be used in combination with immune-oncology therapy.Significance: BR-001, a potent inhibitor of the EED subunit of the PRC2 complex, suppresses tumor progression by modulating the tumor microenvironment. Analysis and interpretation of data (e.g., statistical analysis, biostatistics, computational analysis):

Small molecules in targeted cancer therapy: advances, challenges, and future perspectives

“…428 A phase I trial (NCT02900651) is ongoing to evaluate the safety and efficacy of EED226 in patients with advanced malignancies, such as DLBCL, nasopharyngeal carcinoma (NPC) or other advanced solid tumors for whom no further effective standard treatment is available. Besides, some other small-molecule inhibitors, such as A-395, 429 BR-001, and UNC6852, were also reported as EED inhibitors that inhibit the interaction between EZH2 and EED and destabilize PRC2 complex, 430,431 thereby exerting antitumor activity. Moreover, Wang et al developed a unique strategy to target EZH2 by protein degradation.…”

Polycomb Repressive Complex 2 Modulation through the Development of EZH2–EED Interaction Inhibitors and EED Binders

“…Finally, the authors unveiled an unprecedented immunomodulatory mechanism of action for BR-001 and most likely for EZH2 allosteric inhibitors in general. 54 Indeed, BR-001 resulted in robust upregulation of the CXCL10 chemokine levels in colorectal carcinoma cells that eventually led to CD8 + T cell recruitment to the tumor in murine models, which might expand the biological application of this antitumor agent.…”

“…The ensuing hit-optimization process has led to EED binders with improved physicochemical and biological properties in vivo , ultimately providing a clinical candidate (MAK683). 53 , 54 …”

Allosteric regulation of histone lysine methyltransferases: from context-specific regulation to selective drugs

“…Small molecules that were designed to bind the allosteric site of the PRC2 regulatory subunit EED disrupt its interaction with the H3K27me3 mark. Some of these EED inhibitors are highly effective in inhibiting the histone methyltransferase activity of PRC2 [120][121][122][123]. Among them, EED226 induces a conformational change upon binding to EED and these interactions lead to the loss of PRC2 activity, with a similar cellular effect as the SAM-competitive inhibitors targeting the active site [120].…”