Targeting Myeloid Differentiation Using Potent 2‑Hydroxypyrazolo[1,5‑a]pyridine Scaffold-Based Human Dihydroorotate Dehydrogenase Inhibitors

Human dihydroorotate dehydrogenase (hDHODH) catalyzes the rate-limiting step in de novo pyrimidine biosynthesis, the conversion of dihydroorotate to orotate. hDHODH has recently been found to be associated with acute myelogenous leukemia, a disease for which the standard of intensive care has not changed over decades. This work presents a novel class of hDHODH inhibitors, which are based on an unusual carboxylic group bioisostere 2-hydroxypyrazolo­[1,5-a]­pyridine, that has been designed starting from brequinar, one of the most potent hDHODH inhibitors. A combination of structure-based and ligand-based strategies produced compound 4, which shows brequinar-like hDHODH potency in vitro and is superior in terms of cytotoxicity and immunosuppression. Compound 4 also restores myeloid differentiation in leukemia cell lines at concentrations that are one log digit lower than those achieved in experiments with brequinar. This Article reports the design, synthesis, SAR, X-ray crystallography, biological assays, and physicochemical characterization of the new class of hDHODH inhibitors.

人二氢乳清酸脱氢酶（hDHODH）催化从头嘧啶生物合成途径中的限速步骤，即二氢乳清酸向乳清酸的转化。近期研究发现，hDHODH与急性髓系白血病相关，而该疾病的标准化强化治疗方案数十年来未曾更新。本研究报道了一类新型hDHODH抑制剂，其核心骨架基于罕见的羧酸基团生物电子等排体（bioisostere）2-羟基吡唑并[1,5-a]吡啶，设计起点为目前活性最强的hDHODH抑制剂之一布喹那（brequinar）。通过整合基于结构与基于配体的两类设计策略，研究人员获得化合物4：其体外hDHODH抑制活性与布喹那相当，但在细胞毒性与免疫抑制活性方面更具优势。此外，化合物4可在比布喹那实验所用浓度低一个数量级的剂量下，恢复白血病细胞系的髓系分化。本文报道了这类新型hDHODH抑制剂的设计、合成、构效关系（structure-activity relationship, SAR）、X射线晶体学分析、生物学活性评价及理化特性表征。