HDAC3调节显示了对乳腺癌，包括三阴性病例的潜力。设计并合成了新型吡嗪-肼基类HDAC3抑制剂。首发化合物4i表现出强力HDAC3抑制活性（IC50 = 14 nM），至少具有121倍的选择性。它对三阴性乳腺癌细胞具有较强的细胞毒性（IC50：4T1为0.55 μM，MDA-MB-231为0.74 μM），并且对正常细胞具有最小毒性。代谢稳定的4i展现了优越的药代动力学特性。在携带肿瘤的小鼠模型中观察到的4i的治疗效果呈剂量依赖。肿瘤组织的生物标记分析显示较Ac-tubulin和Ac-SMC3增强的乙酰化作用，乙酰化位点包括Ac-H3K9，Ac-H3K27和Ac-H4K12，表明4i体内对HDAC3具有选择性。肿瘤组织的免疫印迹研究显示凋亡蛋白caspase-3，caspase-7和细胞色素C的上调，以及增殖标志物Bcl-2，CD44，EGFR和Ki-67的下调。化合物4i代表了一个有希望的潜在治疗药物，特别是对于三阴性乳腺癌病例而言。

HDAC3 modulation shows promise for breast cancer, including triple-negative cases. Novel pyrazino-hydrazide-based HDAC3 inhibitors were designed and synthesized. Lead compound 4i exhibited potent HDAC3 inhibition (IC50 = 14 nM) with at least 121-fold selectivity. It demonstrated strong cytotoxicity against triple-negative breast cancer cells (IC50: 0.55 μM for 4T1, 0.74 μM for MDA-MB-231) with least normal cell toxicity. Metabolically stable 4i displayed a superior pharmacokinetic profile. A dose-dependent therapeutic efficacy of 4i was observed in a tumor-bearing mouse model. The biomarker analysis with tumor tissues displayed enhanced acetylation on Ac-H3K9, Ac-H3K27, and Ac-H4K12 compared to Ac-tubulin and Ac-SMC3 indicating HDAC3 selectivity of 4i in vivo. The immunoblotting study with tumor tissue showed upregulation of apoptotic proteins caspase-3, caspase-7, and cytochrome c and the downregulation of proliferation markers Bcl-2, CD44, EGFR, and Ki-67. Compound 4i represents a promising candidate for targeted breast cancer therapy, particularly for cases with triple-negative breast cancer.