Identification of analogs that improve activity towards opened KV7.2/3-channels while reducing adverse effects on liver cells in vitro

结构相关的钾通道调节剂氟吡汀和瑞替加滨最近因不良副作用而从市场上召回。毒性的原因可能是由于两种药物氧化为反应性代谢物，在氟吡汀的情况下，其可引起肝损伤，在瑞替加滨的情况下，其可与内源性黑色素反应，在眼睛和指甲组织中形成蓝色色素。在之前的研究中，我们开发了氟吡汀和瑞替加滨的类似物，其中氮原子被交换为硫原子，导致类似物被氧化为不反应的亚砜和砜，或者对氧化反应完全惰性。这些类似物的优点是它们不会生物转化为有毒的氮杂醌二亚胺代谢物;因此，既不会与蛋白质反应形成可能导致肝毒性的免疫原性半抗原，也不会引起色素形成的反应。同时，许多新合成的类似物在打开异源四聚体Kv7.2/3通道方面显示出大大改善的效力。因此，它们的剂量可能比最初的镇痛药氟吡汀或抗癫痫药瑞替加滨低得多，后者在从市场上撤下后开辟了一个空缺的治疗利基。该项目的主要目标是探索新的钾通道调节剂在合成和筛选的迭代过程中的通道开放活性和毒性方面的生物活性，旨在提高这类独特药物的治疗潜力。此外，我们希望探索未经证实的假设，即氮原子与硫原子的交换可以导致氧化的有利抑制或代谢转换为毒性较小的产物。向前推进，重要的是通过测定对其他离子通道的活性来评估化合物对Kv7.2/3的选择性。这也可能导致发现具有独特不同选择性模式的新的先导结构。此外，氧化性能不仅应该用电化学方法进行评估，就像我们过去所做的那样，而且更接近生物系统，以便更好地预测活性代谢物的潜在形成。这些研究还将用于优化新化合物的药代动力学性质，例如，由于最具活性的化合物在性质上是亲脂性的，该项目还将致力于改善其物理化学性质，如水溶性。为了实现这一目标，将探索进一步的结构修饰，这在以前的项目中是不可能的，因为时间限制。该项目旨在促进具有良好GI特征、低成瘾性和低肝毒性的新型镇痛药的开发。

The structurally related potassium channel modulators flupirtine and retigabine were recalled recently from the market due to undesirable side effects. The cause for toxicity is likely to be due to the oxidation of both drugs to reactive metabolites, which in the case of flupirtine can cause liver damage and in the case of retigabine can react with endogenic melanin to form blue pigments in the eye and finger nail tissues. In the previous grant, we developed analogues of both flupirtine and retigabine, whereby a nitrogen was exchanged for a sulfur atom, resulting in analogues that are oxidized either to unreactive sulfoxides and sulfones or are inert to oxidations altogether. These analogues could offer the advantage that they will not be biotransformed to toxic azaquinonediimines metabolites; thus, neither reactions with proteins to form immunogenic haptens that could cause hepatotoxicity, nor reactions leading to the formation of color pigments are feared. At the same time, many of the newly synthesized analogues showed much improved potency with regards to opening of the heterotetrameric Kv7.2/3 channel. Thus, they could possibly be dosed at much lower levels than the original analgesic drug flupirtine or the antiepileptic drug retigabine, which after their removal from the market opened a vacant therapeutic niche. The main goal of the project is to explore the biological activities of new potassium channel modulators with respect to channel opening activity and toxicity in an iterative process of synthesis and screening aimed at improving the therapeutic potential of this unique class of drugs. Moreover, we wish to explore the unproven hypothesis that exchange of the nitrogen atoms for sulfur atom can result in an advantageous inhibition of oxidation or a metabolic switching to less toxic products.Moving forward it is important to assess the selectivity of the compounds for Kv7.2/3 by determining the activity on other ion channels. This could also lead to the discovery of new lead structures with uniquely different selectivity patterns. Furthermore, the oxidation properties should not only be evaluated with electrochemical methods, as we have done in the past, but more closely with biological systems so that the potential formation of reactive metabolites can be better anticipated. These studies will also serve to optimize the pharmacokinetic properties of the new compounds, e.g., with regards to plasma half-life.Since the most active compounds are lipophilic in nature, the project will also aim to improve the physicochemical properties, such as water solubility. Towards this goal, further structural modifications will be explored that were not possible because of time constraints in the previous project.The project aims to contribute to the development of novel analgesics with good GI profiles, low addiction potential and low hepatotoxicity.