Metal Chelate Conjugated Dendrimer Constructs for Diagnosis and Therapy

用于诊断和治疗的金属螯合物共轭树枝状聚合物构建体

• 批准号: 8158284
• 负责人: MARTIN W BRECHBIEL
• 金额: $ 48.83万
• 依托单位: DIVISION OF CLINICAL SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/8158284
• 关键词: Diagnosis; Electron Transport Complex III; Malignant neoplasm of ovary; Metals; polypropyleneimine

Macromolecular MRI contrast agents based upon dendrimers obviate many of the deficiencies of serum albumin or linear polymer based MRI contrast agents of comparable size. This is due to the iterative polymeric synthesis by which they are created that then promotes a controlled size and shape of the dendrimer concomitantly generating the means for reproducible chemistry that is key to the clinical translation of such agents. To create MRI contrast agents with dendrimers, the terminal primary amines of dendrimers are modified with chelated Gd(III) developed in our laboratories. Historically, these reagents were shown to possess a molar relaxivity 6 times that of Magnevist, the currently approved MRI contrast agent. Excellent conventional whole body MR imaging and 3D T-O-F MR angiograms have been obtained with PAMAM and polypropyleneimine or DAB dendrimer based agents. Past studies established that macromolecular chelate conjugated dendrimer based Gd(III) MR contrast agents can be tuned for various applications by adjusting fundamental criteria: generation (MW and size), core elements (lipophilicity and charge), PEG conjugation (prolong circulation and minimize liver and other organ uptake), lysine co-administration (renal clearance), and conjugation to targeting vectors (molecular targeting). PAMAM based agents have imaged murine tumor vasculature accurately at the 200 micron scale. DAB based agents have selective properties wherein reverse contrast images of 0.3 mm metastatic liver tumors were detected. These dendrimer based agents have also been selectively targeted, not only by conjugation to antibodies, but by other vectors, such as avidin to deliver exceptionally high levels of Gd(III) into disseminated intraperitoneal ovarian cancer tumor. This study done in conjunction with an optical imaging agent runs in parallel with our creation of multi-modality dendrimer based imaging agents. The incorporation of a NIR optical imaging dye into the MRI agent to add an enhanced level of sensitivity to complement the resolution of the MRI imaging provided an additional level of sensitivity for the imaging of lymphatics and sentinel nodes that can be envisioned as being translated to an intraoperative scenario wherein MRI imaging and mapping would supplement real-time surgical intervention and excision of malignancy. While the chemistry established the ability to create such macromolecular agents, the imaging resulted in compromised targeting which defined that these agents require very careful systematic investigation combined with equally careful defined characterization. Lastly, new chelation chemistry for conjugation of Gd(III) complexes to dendrimer has been prompted by the need to re-invent this field moving it from aqueous chemistry back to organic phase solvents to enhance both characterization and consistency of yields. This chemistry has also evolved out of the need for specialized analogs of established bifunctional chelation agents to address the development of site-specific conjugation chemistry required for actively targeted dendrimer based imaging agents e.g, maleimides targeting a unique thiol residue, or agents functionalized with alkyne and azide groups for click chemistry conjugation strategies. In parallel to this effort, the very recent impact on NFS related Gd(III) toxicity of less than adequately stable MRI contrast agents prompted a complete halt of projects with an application of new directionality in the choice of bifunctional chelating agent at the heart of all of these studies. All ongoing projects were completed using the 1B4M-DTPA bifunctional chelate while all new projects were put on hold until adequate amounts of bifunctional DOTA became available through the synthesis efforts of the Section itself as opposed to purchase of this agent. While this effort was put into place over the past 2 years, all of the MR contrast projects have now migrated to the exclusive use of a pre-complexation of the Gd(III) conjugate strategy using DOTA to eliminate a characterization complexity intended to simplify translation of these agents into clinical use. Results from the studies to validate this transformation have revealed that not only can such a strategy be successfully employed despite warnings of probably lowered solubility (not true), but that far greater molar relaxivity can be achieved by this means. We have reported a 5-fold enhancement over the prior technology while concurrently decreasing the actual physical amount of Gd(III) conjugated to the dendrimer by 65%. The impact of this result should reach across to all macromolecular MR contrast agents regardless of platform to fully address safety, characterization, and reproducibility thereby furthering an entire fields potential for clinical translation of such agents. The exquisite advantages of the dendrimer based agents over low molecular weight agents continue to be very clearly demonstrated. In parallel to the development of dendrimer based agents, a long-term collaboration with NINDS investigators to develop a surrogate marker for CED of chemotherapeutic drugs using an albumin core platform unfortunately was discontinued as those investigators insisted upon using the less safe DTPA chemistry vs. delaying until the above advancement had been achieved and validated. While regrettable, the Chemistry Section would rather get the science and chemistry right and advance this technology into the clinic in the safest format possible using a safe agent as opposed to knowingly participating in the clinical use of an unsafe agent simply to be able to conduct that same trial. Regardless of this disappointment, the Chemistry Section continued the investigation independently to validate the use of the above strategy and a report has been submitted for publication on those results. The US patent covering this technology was issued last year and these new results should prove to make it yet more valuable to HHS and should also contribute to translation of this technology into the clinic. Studies of MRI and other imaging modality agents in collaboration with the Molecular Imaging Program have unfortunately been effectively terminated due to a lack of cooperation and access to instrumentation residing therein in what was to be a resource for all NCI researchers despite agreements to the contrary. However, collaboration with Radiology, CC, the PET Dept, CC, NIMH, and extramural researchers that were easily established to replace the contribution from the Molecular Imaging Program, NCI continue to be fruitful.

基于树枝状聚合物的大分子MRI造影剂消除了基于血清白蛋白或具有可比尺寸的线性聚合物的MRI造影剂的许多缺陷。这是由于它们是通过迭代聚合合成产生的，然后促进树枝状聚合物的受控尺寸和形状，同时产生可重复化学的手段，这是此类药物临床转化的关键。为了用树枝状聚合物制造 MRI 造影剂，树枝状聚合物的末端伯胺用我们实验室开发的螯合 Gd(III) 进行修饰。从历史上看，这些试剂的摩尔弛豫度是当前批准的 MRI 造影剂 Magnevis 的 6 倍。使用基于 PAMAM 和聚丙烯亚胺或 DAB 树枝状聚合物的试剂可以获得出色的传统全身 MR 成像和 3D T-O-F MR 血管造影照片。过去的研究表明，基于大分子螯合物缀合的树枝状大分子 Gd(III) MR 造影剂可以通过调整基本标准来调整用于各种应用：生成（分子量和尺寸）、核心元素（亲脂性和电荷）、PEG 缀合（延长循环并最大限度地减少肝脏）和其他器官摄取）、赖氨酸共同给药（肾脏清除）以及与靶向载体结合（分子靶向）。基于 PAMAM 的试剂已在 200 微米尺度上对小鼠肿瘤脉管系统进行了精确成像。基于 DAB 的试剂具有选择性特性，其中检测到 0.3 mm 转移性肝肿瘤的反向对比图像。这些基于树枝状聚合物的药物也已被选择性靶向，不仅通过与抗体缀合，而且通过其他载体，例如抗生物素蛋白，将异常高水平的 Gd(III) 递送到播散性腹膜内卵巢癌肿瘤中。这项与光学显像剂结合进行的研究与我们基于多模态树枝状聚合物的显像剂的创建同时进行。将 NIR 光学成像染料加入 MRI 试剂中，可提高灵敏度，以补充 MRI 成像的分辨率，为淋巴管和前哨淋巴结的成像提供了额外的灵敏度，可以设想将其转化为术中场景，其中 MRI 成像和绘图将补充实时手术干预和恶性肿瘤切除。虽然化学建立了制造此类大分子药物的能力，但成像导致靶向性受损，这表明这些药物需要非常仔细的系统研究以及同样仔细的定义表征。 最后，由于需要重新发明这一领域，将其从水相化学转移回有机相溶剂，以增强表征和产率的一致性，因此催生了用于将 Gd(III) 配合物与树枝状聚合物缀合的新螯合化学。这种化学反应还源于对已建立的双功能螯合剂的专门类似物的需求，以解决主动靶向树枝状大分子成像剂所需的位点特异性缀合化学的发展，例如靶向独特硫醇残基的马来酰亚胺，或用炔和官能化的试剂。用于点击化学缀合策略的叠氮化物基团。与此同时，最近不稳定的 MRI 造影剂对 NFS 相关 Gd(III) 毒性的影响促使项目完全停止，在双功能螯合剂的选择中应用新方向是所有项目的核心这些研究。所有正在进行的项目都是使用 1B4M-DTPA 双功能螯合物完成的，而所有新项目都被搁置，直到通过该部门本身的合成工作而不是购买该试剂获得足够数量的双功能 DOTA。虽然这项工作是在过去 2 年中投入实施的，但所有 MR 对比项目现已转向专门使用 Gd(III) 共轭策略的预复合，使用 DOTA 来消除表征复杂性，旨在简化翻译这些药物投入临床使用。 验证这种转变的研究结果表明，尽管有可能降低溶解度的警告（不正确），但这种策略不仅可以成功采用，而且可以通过这种方式实现更大的摩尔弛豫率。我们报告了比现有技术增强了 5 倍，同时将与树枝状聚合物结合的 Gd(III) 的实际物理量减少了 65%。这一结果的影响应该遍及所有大分子磁共振造影剂，无论平台如何，以充分解决安全性、表征和再现性，从而进一步推动此类药物临床转化的整个领域的潜力。基于树枝状聚合物的试剂相对于低分子量试剂的卓越优势继续得到非常清楚的证明。在开发基于树枝状大分子的药物的同时，与 NINDS 研究人员长期合作，使用白蛋白核心平台开发化疗药物 CED 的替代标记，不幸的是，由于这些研究人员坚持使用不太安全的 DTPA 化学而不是延迟，因此中止了直到上述进步得到实现并得到验证。虽然令人遗憾的是，化学科宁愿正确地掌握科学和化学，并使用安全的药剂以尽可能安全的形式将这项技术推进到临床，而不是故意参与不安全药剂的临床使用，只是为了能够进行同样的审判。尽管令人失望，化学科仍继续独立进行调查，以验证上述策略的使用，并已提交一份关于这些结果的报告供出版。这项技术的美国专利于去年发布，这些新结果应该会证明它对 HHS 来说更有价值，并且也应该有助于将该技术转化为临床。不幸的是，与分子成像项目合作进行的 MRI 和其他成像方式研究已被有效终止，因为尽管有相反的协议，但由于缺乏合作和使用其中的仪器，这些仪器本应成为所有 NCI 研究人员的资源。然而，与放射科、CC、PET 部门、CC、NIMH 和校外研究人员的合作很容易建立，以取代 NCI 分子成像项目的贡献，仍然富有成效。