Leveraging RNA nanotechnology for next-generation gene delivery systems

我们能建立有效的基因传递系统来靶向大脑吗？基因疗法有望有效逆转遗传性和获得性脑部疾病的病因。然而，大脑可以说是治疗药物，特别是大型基因治疗药物所针对的最具挑战性的器官。这是由于血脑屏障(BBB)的存在，血脑屏障是一种高度选择性的边界，将血液循环与大脑分开，由嵌入毛细血管基底膜的一层连续的密封内皮细胞形成。血脑屏障在生理上保护神经元免受血液中存在的神经毒性因素的影响，但也阻止了外源性药物达到其作用目标。非靶向脑疗法不仅会导致治疗效果不佳，而且还会因有毒药物在其他器官中积聚而产生副作用，危及患者的生命。脂类纳米颗粒被认为能够通过血脑屏障，这要归功于它们的电荷和大小通过流产介导的内吞作用或跨细胞作用。但这种方法未能提供有效的递送，缺乏针对大脑的已获批准的基因疗法就证明了这一点。我们可以使用核酸作为基因递送系统来靶向大脑吗？核酸是一种不稳定的天然聚合物，在静脉注射时会被核酸酶降解，到目前为止被认为不适合用作药物输送载体。然而，它们具有适应空间排列的分子和精确形状和大小的纳米颗粒的受控化学计量比的固有性质，这对于有效的组织和细胞靶向至关重要。新的方法包括引入核酸酶稳定的RNA纳米颗粒，这是基于Six公司的专利组合，用于开发基于DNA和RNA的纳米颗粒和靶向分子，包括但不限于适体，用于提供选定的基因治疗药物。在初步研究中，这些颗粒已经显示出在大脑中积累。该研究方案的重点是评估RNA纳米颗粒电荷、亲脂性和大小之间的因果关系，以及与组织/细胞靶向之间的关系。核酸的重复单位(核苷酸)的性质允许在计算机中精确设计输送系统，并使用机器学习预测纳米颗粒的行为。这为创建组织靶向的按需平台并减少物理实验提供了高度的灵活性。将开发一套允许纳米颗粒进行化学计量表征和生物分布监测成像的方法工具箱。该平台的临床前演示者将接受评估，这要归功于致力于神经退行性疾病动物模型的先驱研究小组的参与，这些动物模型包括帕金森氏症和肯尼迪病(脊髓性肌萎缩症)。

Can we built efficient gene delivery systems to target the brain? Gene therapy offers the promise to effectively revert the cause of inherited and acquired brain diseases. However, the brain is arguably the most challenging organ to target with therapeutic agents, especially large-size gene therapeutics. This is due to the existence of the blood brain barrier (BBB) - a highly selective border separating the blood circulation from the brain, formed by a continuous layer of sealed endothelial cells embedded in the capillary basement membrane. The BBB physiologically protects the neurons from neurotoxic factors present in the bloodstream, but also prevents exogenously administered medications to reach their target of action. Non-targeting brain therapies could not only result in poor efficacy of the treatment, but also in side effects due to the accumulation of toxic drugs in other organs, encumbering the life of the patient. Lipid nanoparticles were thought to cross the BBB, thanks to their charge and size by abortpion mediated endocytosis or transcytosis. But this approach failed to provide efficient delivery, testified by the lack of approved gene therapies targeting the brain.Can we use nucleic acids as gene delivery systems to target the brain? Nucleic acids are unstable natural polymers that degrade by nucleases upon intravenous injection and thus far were considered unsuitable for use as drug delivery vehicles. Yet, they have inherent properties to accommodate spatially arranged molecules and controlled stoichiometry for precise shape and size nanoparticles, crucial for an efficient tissue and cell targeting. The new approach involves the introduction of nuclease stable RNA nanoparticles, based on Sixfold's Ltd patent portfolio for the exploitation of DNA and RNA-based nanoparticles and targeting molecules including, but not limited to, aptamers, for the delivery of selected gene therapeutics. In preliminary studies, these particles have shown to accumulate in the brain. The research programme focuses on the assessment of the causal relationship between RNA nanoparticles charge, lipophilicity and size; to tissue/cell targeting. The nature of repetitive units (nucleotides) of nucleic acids, allows for precise design of the delivery systems in silico and prediction of the nanoparticle behaviour using Machine Learning. This offers a high degree of flexibility to create an on-demand platform for tissue targeting and reduce the physical experimentation. A toolbox of methods allowing for the nanoparticles stoichiometric characterization and biodistribution monitoring imaging will be developed. Preclinical demonstrators of the platform will be assessed thanks to the engagement of pioneering research groups working on animal models on neurodegenerative diseases including Parkinson's and Kennedy's (spinal bulbar muscular atrophy) diseases.