Ribonucleotide reductase (RR), an established cancer target, is usually inhibited by antimetabolites, which display multiple cross-reactive effects. Recently, we discovered a naphthyl salicyl acyl hydrazone-based inhibitor (NSAH or E-3a) of human RR (hRR) binding at the catalytic site (C-site) and inhibiting hRR reversibly. We herein report the synthesis and biochemical characterization of 25 distinct analogs. We designed each analog through docking to the C-site of hRR based on our 2.7 Å X-ray crystal structure (PDB ID: 5TUS). Broad tolerance to minor structural variations preserving inhibitory potency is observed. E-3f (82% yield) displayed an in vitro IC₅₀ of 5.3 ± 1.8 μM against hRR, making it the most potent in this series. Kinetic assays reveal that E-3a, E-3c, E-3t, and E-3w bind and inhibit hRR through a reversible and competitive mode. Target selectivity toward the R1 subunit of hRR is established, providing a novel way of inhibition of this crucial enzyme.

中文翻译：

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结构指导的合成和机理研究揭示了萘基水杨Hy Hy支架上的亮点是人类核糖核苷酸还原酶的非核糖竞争性可逆抑制剂。

核糖核苷酸还原酶（RR）是已确立的癌症靶标，通常被抗代谢物抑制，该抗代谢物表现出多种交叉反应作用。最近，我们发现了基于萘基水杨酰基的人RR（hRR）的抑制剂（NSAH或E - 3a）在催化位点（C-位）结合并可逆地抑制hRR。我们在此报告了25种不同类似物的合成和生化特性。我们基于2.7ÅX射线晶体结构（PDB ID：5TUS），通过对接至hRR的C位点设计了每个类似物。观察到对微小结构变化的广泛耐受性，从而保持了抑制效力。E - 3f（82％的收率）显示了体外IC ₅₀相对于hRR为5.3±1.8μM，使其在该系列中最有效。动力学测定表明，E - 3a，E - 3c，E - 3t和E - 3w通过可逆和竞争模式结合并抑制hRR。建立了对hRR R1亚基的目标选择性，为抑制这种关键酶提供了一种新颖的方法。