College of Bioscience and Biotechnology, Hunan Agricultural University, Changsha, China.
School of Sciences and State Key Laboratory of Natural Medicines, China Pharmaceutical University, Nanjing, China.
Br J Pharmacol. 2024 Apr;181(8):1203-1220. doi: 10.1111/bph.16273. Epub 2023 Dec 7.
The P2X3 receptor, a trimeric ionotropic purinergic receptor, has emerged as a potential therapeutic target for refractory chronic cough (RCC). Nevertheless, gefapixant/AF-219, the only marketed P2X3 receptor antagonist, might lead taste disorders by modulating the human P2X2/3 (hP2X2/3) heterotrimer. Hence, in RCC drug development, compounds exhibiting strong affinity for the hP2X3 homotrimer and a weak affinity for the hP2X2/3 heterotrimer hold promise. An example of such a molecule is sivopixant/S-600918, a clinical Phase II RCC candidate with a reduced incidence of taste disturbance compared to gefapixant. Sivopixant and its analogue, (3-(4-([3-chloro-4-isopropoxyphenyl]amino)-3-(4-methylbenzyl)-2,6-dioxo-3,6-dihydro-1,3,5-triazin-1(2H)-yl)propanoic acid (DDTPA), exhibit both high affinity and high selectivity for hP2X3 homotrimers, compared with hP2X2/3 heterotrimers. The mechanism underlying the druggable site and its high selectivity remains unclear.
To analyse mechanisms that distinguish this drug candidate from other inhibitors of the P2X3 receptors we used a combination of chimera construction, site covalent occupation, metadynamics, mutagenesis and whole-cell recording.
The high affinity and selectivity of sivopixant/DDTPA for hP2X3 receptors was determined by the tri-symmetric site located close to the upper vestibule. Substitution of only four amino acids inside the upper body domain of hP2X2 with those of hP2X3, enabled the hP2X2/3 heterotrimer to exhibit a similar level of apparent affinity for sivopixant/DDTPA as the hP2X3 homotrimer.
From the receptor-ligand recognition perspective, we have elucidated the molecular basis of novel RCC clinical candidates' cough-suppressing properties and reduced side effects, offering a promising approach to the discovery of novel drugs that specifically target P2X3 receptors.
P2X3 受体是一种三聚体离子型嘌呤能受体，已成为难治性慢性咳嗽（RCC）的潜在治疗靶点。然而，唯一上市的 P2X3 受体拮抗剂 gefapixant/AF-219 可能通过调节人 P2X2/3（hP2X2/3）异三聚体而导致味觉障碍。因此，在 RCC 药物开发中，对于 hP2X3 同三聚体具有强亲和力且对 hP2X2/3 异三聚体具有弱亲和力的化合物具有潜力。此类分子的一个例子是 sivopixant/S-600918，这是一种临床二期 RCC 候选药物，与 gefapixant 相比，味觉障碍的发生率降低。Sivopixant 及其类似物（3-（4-（[3-氯-4-异丙氧基苯基]氨基）-3-（4-甲基苄基）-2,6-二氧代-3,6-二氢-1,3,5-三嗪-1（2H）-基）丙基）-丙酸（DDTPA）与 hP2X2/3 异三聚体相比，对 hP2X3 同三聚体具有高亲和力和高选择性。其作用部位的可用药机制及其高选择性仍不清楚。
为了分析该候选药物与其他 P2X3 受体抑制剂之间的区别，我们使用嵌合体构建、位点共价占据、元动力学、突变和全细胞记录的组合来分析机制。
Sivopixant/DDTPA 对 hP2X3 受体的高亲和力和选择性是由靠近上前庭的三对称位点决定的。仅将 hP2X2 上部结构域内的四个氨基酸替换为 hP2X3 的氨基酸，使 hP2X2/3 异三聚体对 sivopixant/DDTPA 的表观亲和力与 hP2X3 同三聚体相似。
从受体-配体识别的角度，我们阐明了新型 RCC 临床候选药物镇咳作用和降低副作用的分子基础，为发现专门针对 P2X3 受体的新型药物提供了有前途的方法。
