Targeting EZH2 and EGFR therapeutic vulnerabilities of TNBC with a single chemical entity confers preclinical treatment advantage

Globally, triple-negative breast cancer (TNBC) has a huge unmet medical need, as it has limited targeted therapeutic options. However, it has well-known therapeutic vulnerabilities for selective inhibition of pathways such as EGFR, mTOR, PARP, enhancer of zeste homolog 2 (EZH2), PD1-PDL1, etc. Analysis of publicly available databases clearly suggests that concomitant EZH2 and EGFR overexpression results in poor survival of patients with TNBC compared to their individual overexpression, underscoring the strong rationale for dual-targeted therapeutic intervention. Herein, potent, tumor cell-selective chemical probes were designed and synthesized that simultaneously bind to both EZH2 and EGFR and inhibit their pro-tumorigenic functions in TNBC. Structure-activity relationship (SAR)-driven optimized lead molecule S-023-0996 (41a) proficiently binds and inhibits dual targets, dampening tumor cell proliferation, migration, and invasion in vitro with superior efficacy and safety than individual drug combinations (EZH2 inhibitor tazemetostat and EGFR inhibitor gefitinib). Mass spectrometry-based proteomic profiling revealed that translation inhibition is a key differentiating factor for achieving robust anti-tumor effects of S-023-0996. S-023-0996 has favorable pharmacokinetic properties and inhibits tumor growth and metastasis in vivo more efficiently than comparator drug combinations in preclinical TNBC models. Our results represent the discovery of a first-in-class dual EZH2-EGFR inhibitor and establish the possibility of targeting two TNBC vulnerabilities together with a single chemical entity.