P2X4 receptor antagonists have potential as drugs for the treatment of neuropathic pain and neurodegenerative diseases. In the present study the discovery of phenoxazine derivatives as potent P2X4 antagonists is described. N-Substituted phenoxazine and related acridone and benzoxazine derivatives were synthesized and optimized with regard to their potency to inhibit ATP-induced calcium influx in 1321N1 astrocytoma cells stably transfected with the human P2X4 receptor. In addition, species selectivity (rat, mouse, human) and receptor subtype selectivity (versus P2X1,2,3,7) were investigated. The most potent P2X4 antagonist of the present series was N-(benzyloxycarbonyl)phenoxazine (26, PSB-12054) with an IC₅₀ of 0.189 μM and good selectivity versus the other human P2X receptor subtypes. N-(p-Methylphenylsulfonyl)phenoxazine (21, PSB-12062) was identified as a selective P2X4 antagonist that was equally potent in all three species (IC₅₀: 0.928–1.76 μM). The compounds showed an allosteric mechanism of action. The present study represents the first structure–activity relationship analysis of P2X4 antagonists.

中文翻译：

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N取代的苯恶嗪和Ac啶酮衍生物：强大的P2X4受体拮抗剂的结构-活性关系。

P2X4受体拮抗剂作为治疗神经性疼痛和神经退行性疾病的药物具有潜力。在本研究中，描述了吩恶嗪衍生物作为有效的P2X4拮抗剂的发现。合成并优化了N取代的吩恶嗪以及相关的a啶酮和苯并恶嗪衍生物，以抑制在被人P2X4受体稳定转染的1321N1星形细胞瘤细胞中ATP诱导的钙内流。此外，还研究了物种选择性（大鼠，小鼠，人类）和受体亚型选择性（相对于P2X1,2,3,7）。本系列中最有效的P2X4拮抗剂是N-（苄氧羰基）吩恶嗪（26，PSB-12054），IC ₅₀与其他人P2X受体亚型相比，具有0.189μM的选择性和良好的选择性。N-（对-甲基苯基磺酰基）苯恶嗪（21，PSB-12062）被确定为选择性P2X4拮抗剂，在所有三个物种中均具有同等效力（IC ₅₀：0.928-1.76μM）。该化合物显示出变构作用机理。本研究代表了P2X4拮抗剂的第一个结构-活性关系分析。