Identification of a New Class of Selective Excitatory Amino Acid Transporter Subtype 1 (EAAT1) Inhibitors Followed by a Structure–Activity Relationship Study

Screening of a small compound library at the three excitatory amino acid transporter subtypes 1–3 (EAAT1–3) resulted in the identification of compound (Z)-4-chloro-3-(5-((3-(2-ethoxy-2-oxoethyl)-2,4-dioxothiazolidin-5-ylidene)­methyl)­furan-2-yl)­benzoic acid (1a) that exhibited a distinct preference as an inhibitor at EAAT1 (IC50 20 μM) compared to EAAT2 and EAAT3 (IC50 > 300 μM). This prompted us to subject 1a to an elaborate structure–activity relationship study through the purchase and synthesis and subsequent pharmacological characterization of a total of 36 analogues. Although this effort did not result in analogues with substantially improved inhibitory potencies at EAAT1 compared to that displayed by the hit, it provided a detailed insight into structural requirements for EAAT1 activity of this scaffold. The discovery of this new class of EAAT1-selective inhibitors not only supplements the currently available pharmacological tools in the EAAT field but also substantiates the notion that EAAT ligands not derived from α-amino acids hold considerable potential in terms of subtype-selective modulation of the transporters.针对3种兴奋性氨基酸转运体（excitatory amino acid transporter, EAAT）亚型1~3的小分子化合物库筛选，成功鉴定出化合物(Z)-4-氯-3-(5-((3-(2-乙氧基-2-氧代乙基)-2,4-二氧代噻唑烷-5-亚基)甲基)呋喃-2-基)苯甲酸(1a)。该化合物对EAAT1表现出显著的抑制剂选择性，其半数抑制浓度（half maximal inhibitory concentration, IC50）为20 μM，相较于其对EAAT2与EAAT3的抑制活性（IC50 > 300 μM）差异显著。这一结果促使我们对化合物1a开展系统性构效关系研究，通过采购与合成共计36个类似物，并对其进行后续药理学表征。尽管该研究未获得相较于先导化合物1a对EAAT1抑制活性显著提升的类似物，但本研究明确了该母核结构发挥EAAT1抑制活性所需的结构特征。本次发现的这类新型EAAT1选择性抑制剂，不仅补充了EAAT研究领域当前可用的药理学工具，同时也验证了一个观点：非源自α-氨基酸的EAAT配体，在转运体亚型选择性调控方面具有可观的应用潜力。