Introduction The orexin neuropeptide–receptor system is a central sleep and wake regulator in the brain. The two orexin receptor subtypes, OX1R and OX2R, are expressed either alone or together in all major wake-promoting brain areas. OX1R and OX2R activation by orexins causes elevation of intracellular calcium, which enhances synaptic transmission in secondary, monoaminergic wake- and arousal-promoting neurotransmitter circuits. Orexin receptor antagonists represent a novel and specific treatment of insomnia, which is different from classical therapy that more broadly inhibits brain activity via GABAA activation. Here we describe the molecular pharmacology of daridorexant, an orexin receptor antagonist which has proven highly effective in improving sleep and daytime functioning in insomnia patients. Methods Orexin-A(OxA)-induced calcium release assays in OX1R- and OX2R-expressing recombinant cell lines were applied to measure the antagonistic potency and kinetic properties of daridorexant in functional assays. Whole-cell competitive binding assays, using an orthosteric tracer were employed to determine the Ki of daridorexant. Comparisons were made with suvorexant and lemborexant. Results In OxA-induced calcium release assays with 2-h pre-incubation time, daridorexant displayed apparent Kb values of 0.5 nM (OX1R) and 0.8 nM (OX2R) with insurmountable antagonism on both receptors, demonstrating equipotent and highly effective functional inhibition of both receptor subtypes. On-target residence times of daridorexant (37oC) expressed as receptor occupancy half-lives (ROt1/2) were 4 min (OX1R) and 8 min (OX2R). In binding assays, daridorexant behaved as highly potent orthosteric antagonist. Also suvorexant behaved as dual insurmountable antagonist at OX1R/OX2R (appKb=0.7nM/1.0nM; ROt1/2=9 min/6 min) and as potent orthosteric antagonist in binding assays. Interestingly, lemborexant displayed a different interaction profile at OX1R/OX2R (appKb=13nM/0.4nM, ROt1/2<2min/<2min), i.e. it behaved as preferential OX2R antagonist with a very short on-target residence time and little insurmountability. Conclusion Daridorexant displays the desired target interaction profile of a dual, equipotent, and insurmountable antagonist of both OX1R and OX2R, which ensures equally efficient inhibition of both arousal-/wake-promoting receptor subtypes. Daridorexant′s on-target residence times are long enough to cause insurmountable inhibition, but short enough to avoid pharmacodynamic effects after drug elimination. Support (if any) Funded by Idorsia Pharmaceuticals Ltd.

中文翻译：

---

059 Daridorexant：orexin-1 和 orexin-2 受体的双重、等效和不可克服的拮抗剂

简介 食欲素神经肽受体系统是大脑中的中央睡眠和唤醒调节器。两种食欲素受体亚型，OX1R 和 OX2R，在所有主要的促醒脑区单独或一起表达。食欲素对 OX1R 和 OX2R 的激活会导致细胞内钙升高，从而增强次级、单胺能唤醒和唤醒促进神经递质回路中的突触传递。Orexin 受体拮抗剂代表了一种新的和特异性的失眠治疗方法，它不同于通过 GABAA 激活更广泛地抑制大脑活动的经典疗法。在这里，我们描述了 daridorexant 的分子药理学，这是一种食欲素受体拮抗剂，已被证明在改善失眠患者的睡眠和白天功能方面非常有效。方法 在表达 OX1R 和 OX2R 的重组细胞系中应用 Orexin-A(OxA) 诱导的钙释放测定，以测量达瑞克生在功能测定中的拮抗效力和动力学特性。使用正构示踪剂的全细胞竞争性结合测定被用来确定daridorexant的Ki。与 suvorexant 和 lemborexant 进行了比较。结果 在 2 小时预孵育时间的 OxA 诱导的钙释放试验中，daridorexant 显示出 0.5 nM (OX1R) 和 0.8 nM (OX2R) 的表观 Kb 值，对两种受体具有不可克服的拮抗作用，证明了对这两种受体的等效且高效的功能抑制受体亚型。以受体占据半衰期 (ROt1/2) 表示的 daridorexant (37oC) 的靶向停留时间分别为 4 分钟 (OX1R) 和 8 分钟 (OX2R)。在结合测定中，daridorexant 表现为高效的正构拮抗剂。此外，suvorexant 在 OX1R/OX2R (appKb=0.7nM/1.0nM；ROt1/2=9 min/6 min) 上表现为双重不可克服的拮抗剂，在结合试验中表现为有效的正构拮抗剂。有趣的是，lemborexant 在 OX1R/OX2R（appKb=13nM/0.4nM，ROt1/2<2min/<2min）表现出不同的相互作用特征，即它表现为优先的 OX2R 拮抗剂，具有非常短的在靶停留时间和几乎不可逾越的能力. 结论 Daridorexant 显示了 OX1R 和 OX2R 的双重、等效和不可克服的双重拮抗剂的所需靶标相互作用谱，这确保了对唤醒/唤醒促进受体亚型的同等有效抑制。Daridorexant 的在靶停留时间足够长，足以引起难以克服的抑制作用，但足够短以避免药物消除后的药效学影响。支持（如果有）由 Idorsia Pharmaceuticals Ltd. 资助。