Bioconjugate approaches for the systemic delivery of proteins with the Feldan Shuttle

细胞膜是一种生物屏障，很难穿过，尤其是蛋白质。它的极性外部和非极性内部有效地阻止了这些分子的扩散，这限制了它们到达细胞内部的能力。这是治疗性蛋白质递送的主要挑战，因为这些药剂中的许多必须到达细胞内空间才有活性。Feldan Therapeutics Inc已经开发了阳离子肽文库（即，FeldanShuttle平台）以促进蛋白质、蛋白质复合物和肽（即，货物）进入细胞。由于在货物和穿梭之间没有形成共价键，并且由于文库内有大量不同的肽穿梭，因此该平台适合于促进许多类别的货物的细胞内递送。这已经在离体以及中试动物研究中得到证实。然而，这一过程是非特异性的，将在遇到的第一个细胞中发生。虽然对于将蛋白质递送到细胞培养物中不是问题，但这种非特异性意味着货物递送将限于注射部位的紧邻区域（即，不能靶向患病组织与健康组织）。此外，虽然穿梭物和货物蛋白之间缺乏共价键被认为对细胞培养实验有利，但这是体内的主要挑战，因为注射时的高稀释度会导致穿梭物与货物蛋白解离。该项目将建立在Gauthier教授和Feldan已经建立的概念验证结果的基础上。目标是进一步推进Shuttle/PEG/Cargo生物缀合物原型的设计，以：i）通过暂时失活其细胞穿透特性来增加其在体内的循环时间; ii）暂时将Cargo蛋白质缀合至Shuttle，使得两种组分都能够在体内循环。（Feldan航天飞机及其货物）到达身体的目标区域; iii）与Shuttle和Cargo的物理混合物相比，在体内实现改变的生物分布。原型的预期开发将是迭代的，并将以健康小鼠的细胞培养和动物实验中评估的性能为指导。

The cell membrane is a biological barrier that can be difficult to cross, especially for proteins. Its polar exterior and non-polar interior effectively block diffusion of these molecules, which limits their ability to reach the interior of the cell. This is a major challenge for the delivery of therapeutic proteins, because many of these agents must reach the intracellular space to be active. Feldan Therapeutics Inc. has developed a library of cationic peptides (i.e., the Feldan Shuttle platform) to facilitate the delivery of proteins, protein complexes, and peptides (i.e., the Cargos) into the cell. Because no covalent bond is formed between the cargo and the Shuttle, and because of the large number of different peptide Shuttles within the library, this platform is suitable for promoting the intracellular delivery of many categories of Cargos. This has been demonstrated in both ex vivo as well as in pilot animal studies. However, this process is non-specific and will occur in the first cells encountered. While not an issue for the delivery of proteins into cell cultures, this non-specificity implies that cargo delivery will be restricted to the immediate area at the site of injection (i.e., inability to target diseased vs. healthy tissue). Moreover, while the lack of covalent bond between the Shuttle and the cargo protein is seen as advantageous for cell culture experiments, this is a major challenge in vivo, due to high dilution upon injection that would cause the Shuttle to become dissociated from the cargo protein. This project will build upon proof-of-concept findings already established by Prof. Gauthier and Feldan. The objectives are to further advance the design of a prototype Shuttle/PEG/Cargo bioconjugate to: i) Increase its circulation time in the body by temporarily deactivating its cell-penetrating properties; ii) Temporarily conjugate a Cargo protein to the Shuttle so that both components (the Feldan Shuttle and its Cargo) reach the targeted area in the body; iii) Achieve altered biodistribution in vivo compared to a physical mixture of Shuttle and Cargo. The foreseen development of the prototype will be iterative and will be guided by performance assessed in both cell culture and animal experiments in healthy mice.