Developing the required biomarkers that define ferroportin target engagement and impact on downstream signaling for clinical translation

摘要 开发所需的生物标志物，以定义铁蛋白靶标的结合和影响 临床翻译的下游信号 铁是生命所必需的，但也是剧毒的。因此，铁的获取、运输、储存和利用 都受到严格的监管。海普西丁是铁的主要调节剂；它控制从饮食中摄取铁和 通过与铁转运蛋白铁蛋白的相互作用，从铁储存中释放出铁。 肝素生产功能障碍会导致严重的健康问题，包括β-地中海贫血和遗传性 血色沉着症。在这两种疾病中，低水平的海普西丁增加了肠道铁的吸收和释放。 从网状内皮系统回收的铁，导致巨噬细胞铁的消耗，相对较低 血清铁蛋白水平，肝脏铁浓度升高，以及游离铁释放到循环中，导致器官 损坏。如果不进行治疗，铁会继续积累，最终相当一部分患者 达到有毒的铁超载水平。 目前，铁超负荷疾病患者的治疗方法包括静脉采血、输血。 和/或铁络合剂，视疾病而定。抽血和输血很不方便，而且 需要去医院就诊，而螯合疗法与相当大的毒性有关。因此，有一个显著的 需要更安全、耐受性更好的新疗法。 由于海普西丁具有复杂的4-二硫键结构、不溶性、聚集性和快速清除性， 它不适合作为一种治疗方法，而海普西丁模拟物已被提出为潜在的治疗方法。要克服 主药海普西丁的物理化学局限性更强、更稳定、更易溶、更有效 使用有目的地构建的基于结构的药物设计环境的替代支架(Vectrix™)。 在SBIR第一阶段提案期间，在优化效力后开发了海普西丁模拟物PTG-300， 稳定性、溶解性和其他物理化学性质。此第二阶段SBIR提案的总体目标是 发展表征体内靶向结合的方法，包括药代动力学和 研究PTG-300与铁蛋白结合的药效学方法及其影响 下游生物标志物和疗效。这些生物标志物将被用来辅助剂量选择和提供早期的 阶段性临床概念验证。 具体目标是：1)开发方法来表征目标交战(TE)的程度 铁蛋白，2)开发药效学(PD)生物标志物，描述铁蛋白结合对 下游信号，3)TE和对PD生物标记物的影响与临床前模型中的疗效相关 地中海贫血，4)为PTG-300的临床应用提供进一步的机制数据。 这些都是朝着我们的最终目标迈出的重要一步，我们的最终目标是展示晚期临床的临床益处 审判。在这项研究中开发的生物标记物将允许评估机制特异性和疾病- 指导临床设计的相关参数。

Abstract Developing the required biomarkers that define ferroportin target engagement and impact on downstream signaling for clinical translation Iron is essential for life, but is also highly toxic. Consequently, iron acquisition, transport, storage and utilization are tightly regulated. Hepcidin is the master regulator of iron; it controls the uptake of iron from diet and the release from iron stores through its interaction with the iron transporter ferroportin. Dysfunctional hepcidin production can cause serious health issues, including β-thalassemia and hereditary hemochromatosis. In both diseases, low hepcidin levels increase intestinal iron absorption and increase release of recycled iron from the reticuloendothelial system, which causes depletion of macrophage iron, relatively lower levels of serum ferritin, increased liver iron concentration, and free iron release into the circulation, causing organ damage. Without treatment, iron continues to accumulate, and a considerable proportion of patients eventually reach toxic iron-overload levels. Patients with iron overload diseases are currently treated with combinations of phlebotomy, blood transfusions and/or iron chelators, depending on the disease. Phlebotomy and blood transfusions are inconvenient and require hospital visits, while chelation therapy is associated with considerable toxicity. Thus, there is a significant need for new treatments that are safer and better tolerated. Because of hepcidin's complicated 4-disulfide structure, insolubility, aggregation potential and rapid clearance, it is unsuitable as a treatment and hepcidin mimetics have been proposed as potential therapeutics. To overcome the physicochemical limitations of hepcidin, Protagonist engineered more potent, stable, soluble and efficacious alternative scaffolds using a purposefully built structure-based drug design environment (Vectrix™). During the SBIR Phase I proposal, the hepcidin mimetic PTG-300 was developed after optimizing potency, stability, solubility and other physicochemical properties. The overall objective of this Phase II SBIR proposal is to develop methods for characterizing in vivo target engagement, including pharmacokinetic and pharmacodynamic methods to characterize the binding of PTG-300 to ferroportin and how binding affects downstream biomarkers and efficacy. These biomarkers will be used to aid dose selections and to provide early- stage clinical proof-of-concept. The specific objectives are to: 1) develop methods to characterize the extent of target engagement (TE) of ferroportin, 2) develop pharmacodynamic (PD) biomarkers that describe the effect of ferroportin engagement on downstream signaling, 3) correlate the TE and effect on PD biomarkers with efficacy in a preclinical model of thalassemia, 4) provide further mechanistic data on the clinical utility of PTG-300. These are important steps towards our ultimate objective of demonstrating clinical benefit in late-stage clinical trials. The biomarkers developed in this study will permit the assessment of mechanism-specific and disease- related parameters to guide clinical design.