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.

基于树状大分子的磁共振造影剂消除了血清白蛋白或类似大小的线性聚合物MRI造影剂的许多缺陷。这是由于它们被创造出来的迭代聚合合成，然后促进了树突分子的控制大小和形状，同时产生了可重复化学的手段，这是这些药物临床翻译的关键。为了制造具有树状大分子的MRI造影剂，我们用实验室开发的螯合Gd（III）修饰了树状大分子的末端伯胺。从历史上看，这些试剂的摩尔弛豫率是目前批准的MRI造影剂Magnevist的6倍。利用PAMAM和聚丙烯亚胺或DAB树突状物获得了出色的常规全身磁共振成像和3D T-O-F磁共振血管成像。过去的研究表明，大分子螯合物偶联树突状分子Gd(III) MR造影剂可以通过调整基本标准来适应各种应用：生成（分子量和大小）、核心元素（亲脂性和电荷）、PEG偶联（延长循环并减少肝脏和其他器官的摄取）、赖氨酸共给药（肾脏清除）和偶联靶向载体（分子靶向）。基于PAMAM的药物可以在200微米尺度上精确成像小鼠肿瘤血管系统。基于DAB的试剂具有选择性，其中0.3 mm转移性肝肿瘤的反向对比图像被检测到。这些基于树突状分子的药物也被选择性靶向，不仅通过与抗体结合，而且通过其他载体，如亲和素，将异常高水平的Gd（III）递送到弥散性腹腔内卵巢癌肿瘤中。这项研究与光学显像剂一起进行，与我们创建的多模态树状聚合物显像剂并行。在MRI试剂中加入近红外光学成像染料，以提高灵敏度水平，以补充MRI成像的分辨率，为淋巴和前哨淋巴结的成像提供了额外的灵敏度水平，可以设想转化为术中场景，其中MRI成像和绘图将补充实时手术干预和恶性肿瘤切除。虽然化学方法建立了制造这种大分子试剂的能力，但成像结果导致靶向性受损，这决定了这些试剂需要非常仔细的系统研究，并结合同样仔细的定义特性。最后，由于需要重新发明这一领域，将其从水化学移回有机相溶剂，以提高表征和产率的一致性，促使了Gd（III）配合物与树状大分子缀合的新螯合化学。这种化学也从对已建立的双功能螯合剂的专门类似物的需求发展而来，以解决主动靶向树状聚合物成像剂所需的位点特异性偶联化学的发展，例如，针对独特硫醇残基的马来酰亚胺，或用于点击化学偶联策略的炔和叠氮基团功能化的试剂。与此同时，最近不太稳定的MRI造影剂对NFS相关Gd（III）毒性的影响促使所有这些研究的核心项目在双功能螯合剂的选择中应用新的方向性。所有正在进行的项目都是使用1B4M-DTPA双功能螯合剂完成的，而所有新项目都被搁置，直到通过该科自身的综合努力获得足够数量的双功能DOTA，而不是购买这种剂。虽然这项工作在过去的2年里已经到位，但所有的MR对比项目现在都已经转移到使用DOTA对Gd（III）缀合物的预络合策略，以消除表征的复杂性，旨在简化这些药物转化为临床使用。验证这一转变的研究结果表明，尽管有可能降低溶解度的警告（不是真的），但这种策略不仅可以成功地应用，而且通过这种方法可以实现更大的摩尔弛豫。我们已经报道了比先前的技术提高了5倍，同时将Gd（III）共轭到树状聚合物上的实际物理量减少了65%。这一结果的影响应该延伸到所有的大分子磁共振造影剂，而不考虑平台，以充分解决安全性、特性和可重复性问题，从而进一步提高这类药物临床翻译的整个领域的潜力。树突状分子基药剂相对于低分子量药剂的优越优势继续得到非常清楚的证明。在开发基于树突状分子的药物的同时，与NINDS研究人员开发一种使用白蛋白核心平台的化疗药物CED替代标志物的长期合作不幸被终止，因为这些研究人员坚持使用不太安全的DTPA化学，而不是推迟到上述进展已经实现和验证。令人遗憾的是，化学科宁愿把科学和化学正确起来，并以尽可能安全的形式使用安全的药物将这项技术推进到临床，而不是故意参与临床使用不安全的药物，只是为了能够进行同样的试验。尽管令人失望，化学科继续独立进行调查，以验证上述战略的使用，并就这些结果提交了一份报告供发表。这项技术的美国专利是去年颁发的，这些新的结果应该证明它对HHS更有价值，也应该有助于将这项技术转化为临床。不幸的是，与分子成像计划合作的MRI和其他成像模式剂的研究已被有效终止，原因是缺乏合作和访问驻留在其中的仪器，这些仪器本应是所有NCI研究人员的资源，尽管有相反的协议。然而，与放射学、CC、PET部门、CC、NIMH和校外研究人员的合作很容易取代分子成像项目的贡献，NCI继续取得成果。