Carrier Shape Matters: Filomicelles, Long-circulation, and the EPR effect

描述（由申请人提供）：这里要解决的最终问题是什么范围的丝状形状和柔性在循环和渗透肿瘤或其他多孔组织中是“纳米”的？我们的蠕虫状“Filomicelles”由两亲性PEG基聚合物制成，类似于临床使用的那些，也类似于用于制备聚合物囊泡的那些，但我们的圆柱形Filomicelles似乎已经具有令人惊讶的独特和有利的药代动力学性质。虽然生物材料文献目前表明，远大于约100-200 nm的颗粒半径导致肝脏和脾脏的吞噬细胞快速清除，但我们发现，许多微米长的丝状胶束可以“蠕动”通过毛细血管并在体内循环一周或更长时间-比迄今报道的任何合成载体都长。绘制出这种长循环的限制-长度，直径，灵活性，表面电荷，药物保留和配体靶向-是我们在体内的终极目标。长循环Filomicelles应该大大增加药物输送的“曲线下面积”，我们确实已经发现，单次注射PEG-聚酯，8 μ m长的Filomicelles负载疏水性抗有丝分裂药物紫杉醇使实体瘤缩小了近一半。这是在“TAX”剂量（mg/kg）下发现的，其作为游离药物无效。丝状胶束也似乎比单次注射负载有TAX和阿霉素的聚合物囊泡更有效。由于我们的两种类型的基于聚合物的载体由PEG分数仅相差5- 10%的共聚物制成，因此我们可以更直接地比较载体形态在递送中的影响。然而，对于这两种系统，我们还不知道有多少TAX（i）直接释放到循环中，（ii）从循环中的降解载体中逐渐释放出球形胶束，或（iii）从渗透肿瘤的丝状胶束或囊泡中释放出来。我们在此的最终目的是解决在异种移植模型中，丝状胶束（相对于聚合物囊泡）如何可以利用增强的渗透和保留（“EPR”）效应被动递送至肿瘤-特别是肺肿瘤（在人中具有80- 90%的死亡率）。这些载体的EPR效应的一般性将在其渗透到非癌性“多孔”组织如受损心肌和营养不良肌肉的有限研究中进行检查。在上述体内研究的同时，我们建议进一步设计（采用原子模拟）、制造、装载、表征（稳定性、释放等），和目标新型嵌段共聚物载体。已经看到靶向蠕虫状丝状胶束在显示合适受体的表面上协同拉链，至少在体外模型系统中是这样。随后细胞的内化可以导致大量药物从单个胶束中一次性释放-原则上足以杀死单个细胞。在我们最初的目标中，我们试图通过首先澄清嵌段共聚物自组装和形状稳定性的规则，然后评估共聚物降解，细胞运输和运输来测试这种效力假设。我们建议集中开发治疗性配体，包括靶向的骨化诱导剂，因为我们最终寻求更广泛的控制和靶向（但首先是被动的！）用于体内研究的共聚物组件。

DESCRIPTION (provided by applicant): The ultimate question to be addressed here is what range of filamentous shapes & flexibilities are 'nano' in the circulation and in permeating tumors or other porous tissues? Our worm-like 'Filomicelles' are made from amphiphilic PEG-based polymers similar to those in clinical use and similar to those used to make polymer vesicles, but our cylindrical Filomicelles already appear to possess surprisingly distinct and advantageous pharmacokinetic properties. While the biomaterials literature currently suggests that a particle radius much greater than approximately 100-200 nm leads to rapid clearance by phagocytes of the liver and spleen, we find that Filomicelles many microns long can "worm" through the capillaries and circulate in vivo for a week or more - longer than any synthetic carrier yet reported. Mapping out the limits of this long circulation - length, diameter, flexibility, surface charge, drug retention, and ligand-targeting - is our pen-ultimate Aim in vivo. Long circulating Filomicelles should greatly increase the 'Area Under the Curve' for drug delivery, and we indeed already find that a single injection of PEG-polyester, 8 mu m-long Filomicelles loaded with the hydrophobic anti-mitotic drug taxol shrinks a solid tumor by almost half ... And this is found at a 'TAX' dose (in mg/kg) which is ineffective as free drug. Filomicelles also appear more potent than a single injection of polymer vesicles loaded with both TAX and Doxorubicin. Since our two types of polymer-based carriers are made from copolymers that differ in PEG fraction by only 5-10%, we can more directly compare effects of carrier morphology in delivery. For either system however, we do not yet know how much TAX is (i) released directly in the circulation, (ii) released gradually with sphere micelles from degrading carriers in circulation, or (iii) released from Filomicelles or vesicles that have permeated the tumor. Our ultimate Aim here is to address how the Filomicelles (vs polymer vesicles) might take advantage of the Enhanced Permeation and Retention ('EPR') effect in passive delivery to tumors - specifically lung tumors (with 80- 90% mortality in humans) in a xenograft model. The generality of the EPR effect with these carriers will be examined in limited studies of their permeation into non-cancerous 'porous' tissues such as damaged myocardium and dystrophic muscle. In parallel with the in vivo studies above, we propose to further the designs (with atomistic simulation), make, load, characterize (stability, release, etc.), and target novel block copolymer carriers. Targeted worm-like Filomicelles are already seen to cooperatively zip up on surfaces displaying suitable receptors, at least with model systems in vitro. Subsequent internalization by the cell can then lead to delivery of a large amount of drug all at once from a single micelle - enough to kill a single cell, in principle. In our initial Aims we seek to test this hypothesis of potency by first clarifying precepts of block copolymer self-assembly and shape stability, and then assessing copolymer degradation, cellular trafficking and transport. We propose a focused development of therapeutic ligands, including targeted apoptosis-inducers, as we ultimately seek a wider range of control and targeting (but passive first!) of copolymer assemblies for in vivo studies.