Brain Tumor-Penetrating Nanoparticle Delivery with MR-Guided Focused Ultrasound

描述(申请人提供)：多形性胶质母细胞瘤(GBM)是最常见的原发脑癌，5年生存率为12%。由于血脑屏障(BBB)的作用，化疗药物以极低的浓度进入大脑，这一事实严重限制了GBM的治疗。目前规避BBB的策略(即格利亚德尔晶片和对流增强输送)是侵入性的，只能适度提高存活率。显然，需要侵入性较小的策略，为脑瘤提供持续和分散的药物输送。为了满足这一需求，我们提出了一种创新的图像引导药物输送方法，通过聚焦超声(FUS)和微泡(MBS)将磁共振(MR)靶向的BBB开口与载药纳米颗粒相结合，这些纳米颗粒已经被设计成具有极高密度的聚乙二醇(PEG)涂层，以快速穿透脑组织(即“脑穿透纳米颗粒”或BPN)。我们假设，这种方法将通过增强跨血脑屏障向FUS靶向肿瘤的药物输送，在肿瘤内部提供持续的药物输送，并将全身副作用降至最低，从而改善脑癌的治疗。我们将用四个目标来检验这一假设。在目标1中，我们将优化BPN的大小和表面化学，以实现脑肿瘤的穿透和长循环时间。示踪剂BPN将被用来确定在体外新获得的脑瘤中生产具有可控颗粒渗透深度的BPN所需的纳米颗粒大小范围和表面化学。随后，将从可生物降解的聚合物中生成具有这些最佳特性的BPN并进行测试。在与目标1平行运行的目标2中，我们将确定安全且可逆的MR引导血脑屏障对9L大鼠颅内肿瘤开放的FUS压力阈值，作为MB直径的函数。然后，FUS压力阈值将被用作确定最佳FUS和MB参数的基础，以将最有希望的BPN配方从AIM 1输送到脑肿瘤。这些FUS和MB参数将被带到目标3，在那里我们将通过荧光分子断层成像(FMT)来评估可生物降解的BPN的全身和脑内的生物分布。BPN在跨血脑屏障传递后进入大脑的分散将使用共聚焦显微镜进一步详细分析。脑组织炎症预计可以忽略不计或不存在，将进行组织学评估。在目标4中，我们将首先确定紫杉醇BPN的最大耐受量(MTD)，然后评估药物的药代动力学(PK)。最后，我们将通过测量治疗后肿瘤生长减少和提高动物存活率来确定MR引导下FUS和MBS载药BPN对侵袭性脑肿瘤的整体疗效。如果这些临床前研究如预期那样进行，我们就可以很好地将其转移到临床上。我们的下一步将是使用弗吉尼亚大学的临床InSightec ExAblate系统在大型动物(猪)中测试MR引导的BPN传递方法的安全性，然后启动临床试验。

DESCRIPTION (provided by applicant): Glioblastoma multiforme (GBM), the most common primary brain cancer, has a 5-year survival rate of <12%. GBM treatment is severely limited by the fact that chemotherapeutic drugs reach the brain in very low concentrations due to the blood brain barrier (BBB). Current strategies to circumvent the BBB (i.e. Gliadel wafers and convection enhanced delivery) are invasive and lead to only moderate improvements in survival. Clearly, less-invasive strategies that provide sustained and well-dispersed drug delivery to brain tumors are needed. To address this need, we propose an innovative image guided drug-delivery approach that couples magnetic resonance (MR)-targeted BBB opening via focused ultrasound (FUS) and microbubbles (MBs) with drug-loaded nanoparticles that have been engineered with extremely dense polyethylene glycol (PEG) coatings to rapidly penetrate brain tissue (i.e. "brain penetrating nanoparticles" or BPNs). We hypothesize that this approach will improve brain cancer treatment by enhancing drug delivery across the BBB to FUS-targeted tumors, providing sustained drug delivery deep within tumors, and minimizing systemic side effects. We will test this hypothesis with 4 aims. In Aim 1, we will optimize BPN size and surface chemistry for brain tumor penetration and long circulation time. Tracer BPNs will be used to determine the nanoparticle size range and surface chemistry required to produce BPNs with controlled particle penetration depths in freshly obtained brain tumors ex vivo. Subsequently, BPNs with these optimal characteristics will be generated from biodegradable polymers and tested. In Aim 2, running in parallel with Aim 1, we will determine FUS pressure thresholds for safe and reversible MR-guided BBB opening to gadolinium in intracranial 9L rat brain tumors as a function of MB diameter. Then, FUS pressure thresholds will be used as a basis for determining optimal FUS and MB parameters for delivering the most promising BPN formulation from Aim 1 to brain tumors. These FUS and MB parameters will be carried to Aim 3, wherein we will evaluate whole-body and brain biodistributions of biodegradable BPNs via Fluorescence Molecular Tomography (FMT). BPN dispersion into the brain after delivery across the BBB will be further analyzed in detail using confocal microscopy. Brain tissue inflammation, which is expected to be negligible or absent, will be assessed histologically. In Aim 4, we will first determine the maximum tolerated dose (MTD) of paclitaxel-loaded BPNs, followed by an evaluation of drug pharmacokinetics (PK). Finally, we will determine the overall efficacy of drug-loaded BPN delivery with MR- guided FUS and MBs to invasive brain tumors by measuring reduced tumor growth and enhanced animal survival after treatment. If these pre-clinical studies proceed as expected, we are well-positioned for translation to the clinic. Our next step would be to test the safety of the MR-guided BPN delivery approach in large animals (pig) using the University of Virginia's clinical Insightec Exablate system, followed by the initiation of a clinical trial.